hjkl_engine/

vim.rs

//! Vim-mode engine.
//!
//! Implements a command grammar of the form
//!
//! ```text
//! Command := count? (operator count? (motion | text-object)
//!                   | motion
//!                   | insert-entry
//!                   | misc)
//! ```
//!
//! The parser is a small state machine driven by one `Input` at a time.
//! Motions and text objects produce a [`Range`] (with inclusive/exclusive
//! / linewise classification). A single [`Operator`] implementation
//! applies a range — so `dw`, `d$`, `daw`, and visual `d` all go through
//! the same code path.
//!
//! The most recent mutating command is stored in
//! [`VimState::last_change`] so `.` can replay it.
//!
//! # Roadmap
//!
//! Tracked in the original plan at
//! `~/.claude/plans/look-at-the-vim-curried-fern.md`. Phases still
//! outstanding — each one can land as an isolated PR.
//!
//! ## P3 — Registers & marks
//!
//! - TODO: `RegisterBank` indexed by char:
//!     - unnamed `""`, last-yank `"0`, small-delete `"-`
//!     - named `"a-"z` (uppercase `"A-"Z` appends instead of overwriting)
//!     - blackhole `"_`
//!     - system clipboard `"+` / `"*` (wire to `crate::clipboard::Clipboard`)
//!     - read-only `":`, `".`, `"%` — surface in `:reg` output
//! - TODO: route every yank / cut / paste through the bank. Parser needs
//!   a `"{reg}` prefix state that captures the target register before a
//!   count / operator.
//! - TODO: `m{a-z}` sets a mark in a `HashMap<char, (buffer_id, row, col)>`;
//!   `'x` jumps to the line (FirstNonBlank), `` `x `` to the exact cell.
//!   Uppercase marks are global across tabs; lowercase are per-buffer.
//! - TODO: `''` and `` `` `` jump to the last-jump position; `'[` `']`
//!   `'<` `'>` bound the last change / visual region.
//! - TODO: `:reg` and `:marks` ex commands.
//!
//! ## P4 — Macros
//!
//! - TODO: `q{a-z}` starts recording raw `Input`s into the register;
//!   next `q` stops.
//! - TODO: `@{a-z}` replays the register by re-feeding inputs through
//!   `step`. `@@` repeats the last macro. Nested macros need a sane
//!   depth cap (e.g. 100) to avoid runaway loops.
//! - TODO: ensure recording doesn't capture the initial `q{a-z}` itself.
//!
//! ## P6 — Polish (still outstanding)
//!
//! - TODO: indent operators `>` / `<` (with line + text-object targets).
//! - TODO: format operator `=` — map to whatever SQL formatter we wire
//!   up; for now stub that returns the range unchanged with a toast.
//! - TODO: case operators `gU` / `gu` / `g~` on a range (already have
//!   single-char `~`).
//! - TODO: screen motions `H` / `M` / `L` once we track the render
//!   viewport height inside Editor.
//! - TODO: scroll-to-cursor motions `zz` / `zt` / `zb`.
//!
//! ## Known substrate / divergence notes
//!
//! - TODO: insert-mode indent helpers — `Ctrl-t` / `Ctrl-d` (increase /
//!   decrease indent on current line) and `Ctrl-r <reg>` (paste from a
//!   register). `Ctrl-r` needs the `RegisterBank` from P3 to be useful.
//! - TODO: `/` and `?` search prompts still live in `the host/src/lib.rs`.
//!   The plan calls for moving them into the editor (so the editor owns
//!   `last_search_pattern` rather than the TUI loop). Safe to defer.

use crate::VimMode;
use crate::input::{Input, Key};

use crate::buf_helpers::{
    buf_cursor_pos, buf_line, buf_line_bytes, buf_line_chars, buf_lines_to_vec, buf_row_count,
    buf_set_cursor_pos, buf_set_cursor_rc,
};
use crate::editor::Editor;

// ─── Modes & parser state ───────────────────────────────────────────────────

#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum Mode {
    #[default]
    Normal,
    Insert,
    Visual,
    VisualLine,
    /// Column-oriented selection (`Ctrl-V`). Unlike the other visual
    /// modes this one doesn't use tui-textarea's single-range selection
    /// — the block corners live in [`VimState::block_anchor`] and the
    /// live cursor. Operators read the rectangle off those two points.
    VisualBlock,
}

#[derive(Debug, Clone, PartialEq, Eq, Default)]
enum Pending {
    #[default]
    None,
    /// Operator seen; still waiting for a motion / text-object / double-op.
    /// `count1` is any count pressed before the operator.
    Op { op: Operator, count1: usize },
    /// Operator + 'i' or 'a' seen; waiting for the text-object character.
    OpTextObj {
        op: Operator,
        count1: usize,
        inner: bool,
    },
    /// Operator + 'g' seen (for `dgg`).
    OpG { op: Operator, count1: usize },
    /// Bare `g` seen in normal/visual — looking for `g`, `e`, `E`, …
    G,
    /// Bare `f`/`F`/`t`/`T` — looking for the target char.
    Find { forward: bool, till: bool },
    /// Operator + `f`/`F`/`t`/`T` — looking for target char.
    OpFind {
        op: Operator,
        count1: usize,
        forward: bool,
        till: bool,
    },
    /// `r` pressed — waiting for the replacement char.
    Replace,
    /// Visual mode + `i` or `a` pressed — waiting for the text-object
    /// character to extend the selection over.
    VisualTextObj { inner: bool },
    /// Bare `z` seen — looking for `z` (center), `t` (top), `b` (bottom).
    Z,
    /// `m` pressed — waiting for the mark letter to set.
    SetMark,
    /// `'` pressed — waiting for the mark letter to jump to its line
    /// (lands on first non-blank, linewise for operators).
    GotoMarkLine,
    /// `` ` `` pressed — waiting for the mark letter to jump to the
    /// exact `(row, col)` stored at set time (charwise for operators).
    GotoMarkChar,
    /// `"` pressed — waiting for the register selector. The next char
    /// (`a`–`z`, `A`–`Z`, `0`–`9`, or `"`) sets `pending_register`.
    SelectRegister,
    /// `q` pressed (not currently recording) — waiting for the macro
    /// register name. The macro records every key after the chord
    /// resolves, until a bare `q` ends the recording.
    RecordMacroTarget,
    /// `@` pressed — waiting for the macro register name to play.
    /// `count` is the prefix multiplier (`3@a` plays the macro 3
    /// times); 0 means "no prefix" and is treated as 1.
    PlayMacroTarget { count: usize },
}

// ─── Operator / Motion / TextObject ────────────────────────────────────────

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Operator {
    Delete,
    Change,
    Yank,
    /// `gU{motion}` — uppercase the range. Entered via the `g` prefix
    /// in normal mode or `U` in visual mode.
    Uppercase,
    /// `gu{motion}` — lowercase the range. `u` in visual mode.
    Lowercase,
    /// `g~{motion}` — toggle case of the range. `~` in visual mode
    /// (character at the cursor for the single-char `~` command stays
    /// its own code path in normal mode).
    ToggleCase,
    /// `>{motion}` — indent the line range by `shiftwidth` spaces.
    /// Always linewise, even when the motion is char-wise — mirrors
    /// vim's behaviour where `>w` indents the current line, not the
    /// word on it.
    Indent,
    /// `<{motion}` — outdent the line range (remove up to
    /// `shiftwidth` leading spaces per line).
    Outdent,
    /// `zf{motion}` / `zf{textobj}` / Visual `zf` — create a closed
    /// fold spanning the row range. Doesn't mutate the buffer text;
    /// cursor restores to the operator's start position.
    Fold,
    /// `gq{motion}` — reflow the row range to `settings.textwidth`.
    /// Greedy word-wrap: collapses each paragraph (blank-line-bounded
    /// run) into space-separated words, then re-emits lines whose
    /// width stays under `textwidth`. Always linewise, like indent.
    Reflow,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Motion {
    Left,
    Right,
    Up,
    Down,
    WordFwd,
    BigWordFwd,
    WordBack,
    BigWordBack,
    WordEnd,
    BigWordEnd,
    /// `ge` — backward word end.
    WordEndBack,
    /// `gE` — backward WORD end.
    BigWordEndBack,
    LineStart,
    FirstNonBlank,
    LineEnd,
    FileTop,
    FileBottom,
    Find {
        ch: char,
        forward: bool,
        till: bool,
    },
    FindRepeat {
        reverse: bool,
    },
    MatchBracket,
    WordAtCursor {
        forward: bool,
        /// `*` / `#` use `\bword\b` boundaries; `g*` / `g#` drop them so
        /// the search hits substrings (e.g. `foo` matches inside `foobar`).
        whole_word: bool,
    },
    /// `n` / `N` — repeat the last `/` or `?` search.
    SearchNext {
        reverse: bool,
    },
    /// `H` — cursor to viewport top (plus `count - 1` rows down).
    ViewportTop,
    /// `M` — cursor to viewport middle.
    ViewportMiddle,
    /// `L` — cursor to viewport bottom (minus `count - 1` rows up).
    ViewportBottom,
    /// `g_` — last non-blank char on the line.
    LastNonBlank,
    /// `gM` — cursor to the middle char column of the current line
    /// (`floor(chars / 2)`). Vim's variant ignoring screen wrap.
    LineMiddle,
    /// `{` — previous paragraph (preceding blank line, or top).
    ParagraphPrev,
    /// `}` — next paragraph (following blank line, or bottom).
    ParagraphNext,
    /// `(` — previous sentence boundary.
    SentencePrev,
    /// `)` — next sentence boundary.
    SentenceNext,
    /// `gj` — `count` visual rows down (one screen segment per step
    /// under `:set wrap`; falls back to `Down` otherwise).
    ScreenDown,
    /// `gk` — `count` visual rows up; mirror of [`Motion::ScreenDown`].
    ScreenUp,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TextObject {
    Word {
        big: bool,
    },
    Quote(char),
    Bracket(char),
    Paragraph,
    /// `it` / `at` — XML/HTML-style tag pair. `inner = true` covers
    /// content between `>` and `</`; `inner = false` covers the open
    /// tag through the close tag inclusive.
    XmlTag,
    /// `is` / `as` — sentence: a run ending at `.`, `?`, or `!`
    /// followed by whitespace or end-of-line. `inner = true` covers
    /// the sentence text only; `inner = false` includes trailing
    /// whitespace.
    Sentence,
}

/// Classification determines how operators treat the range end.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MotionKind {
    /// Range end is exclusive (end column not included). Typical: h, l, w, 0, $.
    Exclusive,
    /// Range end is inclusive. Typical: e, f, t, %.
    Inclusive,
    /// Whole lines from top row to bottom row. Typical: j, k, gg, G.
    Linewise,
}

// ─── Dot-repeat storage ────────────────────────────────────────────────────

/// Information needed to replay a mutating change via `.`.
#[derive(Debug, Clone)]
enum LastChange {
    /// Operator over a motion.
    OpMotion {
        op: Operator,
        motion: Motion,
        count: usize,
        inserted: Option<String>,
    },
    /// Operator over a text-object.
    OpTextObj {
        op: Operator,
        obj: TextObject,
        inner: bool,
        inserted: Option<String>,
    },
    /// `dd`, `cc`, `yy` with a count.
    LineOp {
        op: Operator,
        count: usize,
        inserted: Option<String>,
    },
    /// `x`, `X` with a count.
    CharDel { forward: bool, count: usize },
    /// `r<ch>` with a count.
    ReplaceChar { ch: char, count: usize },
    /// `~` with a count.
    ToggleCase { count: usize },
    /// `J` with a count.
    JoinLine { count: usize },
    /// `p` / `P` with a count.
    Paste { before: bool, count: usize },
    /// `D` (delete to EOL).
    DeleteToEol { inserted: Option<String> },
    /// `o` / `O` + the inserted text.
    OpenLine { above: bool, inserted: String },
    /// `i`/`I`/`a`/`A` + inserted text.
    InsertAt {
        entry: InsertEntry,
        inserted: String,
        count: usize,
    },
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum InsertEntry {
    I,
    A,
    ShiftI,
    ShiftA,
}

// ─── VimState ──────────────────────────────────────────────────────────────

#[derive(Default)]
pub struct VimState {
    mode: Mode,
    pending: Pending,
    count: usize,
    /// Last `f`/`F`/`t`/`T` target, for `;` / `,` repeat.
    last_find: Option<(char, bool, bool)>,
    last_change: Option<LastChange>,
    /// Captured on insert-mode entry: count, buffer snapshot, entry kind.
    insert_session: Option<InsertSession>,
    /// (row, col) anchor for char-wise Visual mode. Set on entry, used
    /// to compute the highlight range and the operator range without
    /// relying on tui-textarea's live selection.
    pub(super) visual_anchor: (usize, usize),
    /// Row anchor for VisualLine mode.
    pub(super) visual_line_anchor: usize,
    /// (row, col) anchor for VisualBlock mode. The live cursor is the
    /// opposite corner.
    pub(super) block_anchor: (usize, usize),
    /// Intended "virtual" column for the block's active corner. j/k
    /// clamp cursor.col to shorter rows, which would collapse the
    /// block across ragged content — so we remember the desired column
    /// separately and use it for block bounds / insert-column
    /// computations. Updated by h/l only.
    pub(super) block_vcol: usize,
    /// Track whether the last yank/cut was linewise (drives `p`/`P` layout).
    pub(super) yank_linewise: bool,
    /// Active register selector — set by `"reg` prefix, consumed by
    /// the next y / d / c / p. `None` falls back to the unnamed `"`.
    pub(super) pending_register: Option<char>,
    /// Recording target — set by `q{reg}`, cleared by a bare `q`.
    /// While `Some`, every consumed `Input` is appended to
    /// `recording_keys`.
    pub(super) recording_macro: Option<char>,
    /// Keys recorded into the in-progress macro. On `q` finish, these
    /// are encoded via [`crate::input::encode_macro`] and written to
    /// the matching named register slot, so macros and yanks share a
    /// single store.
    pub(super) recording_keys: Vec<crate::input::Input>,
    /// Set during `@reg` replay so the recorder doesn't capture the
    /// replayed keystrokes a second time.
    pub(super) replaying_macro: bool,
    /// Last register played via `@reg`. `@@` re-plays this one.
    pub(super) last_macro: Option<char>,
    /// Position of the most recent buffer mutation. Surfaced via
    /// the `'.` / `` `. `` marks for quick "back to last edit".
    pub(super) last_edit_pos: Option<(usize, usize)>,
    /// Position where the cursor was when insert mode last exited (Esc).
    /// Used by `gi` to return to the exact (row, col) where the user
    /// last typed, matching vim's `:h gi`.
    pub(super) last_insert_pos: Option<(usize, usize)>,
    /// Bounded ring of recent edit positions (newest at the back).
    /// `g;` walks toward older entries, `g,` toward newer ones. Capped
    /// at [`CHANGE_LIST_MAX`].
    pub(super) change_list: Vec<(usize, usize)>,
    /// Index into `change_list` while walking. `None` outside a walk —
    /// any new edit clears it (and trims forward entries past it).
    pub(super) change_list_cursor: Option<usize>,
    /// Snapshot of the last visual selection for `gv` re-entry.
    /// Stored on every Visual / VisualLine / VisualBlock exit.
    pub(super) last_visual: Option<LastVisual>,
    /// `zz` / `zt` / `zb` set this so the end-of-step scrolloff
    /// pass doesn't override the user's explicit viewport pinning.
    /// Cleared every step.
    pub(super) viewport_pinned: bool,
    /// Set while replaying `.` / last-change so we don't re-record it.
    replaying: bool,
    /// Entered Normal from Insert via `Ctrl-o`; after the next complete
    /// normal-mode command we return to Insert.
    one_shot_normal: bool,
    /// Live `/` or `?` prompt. `None` outside search-prompt mode.
    pub(super) search_prompt: Option<SearchPrompt>,
    /// Most recent committed search pattern. Surfaced to host apps via
    /// [`Editor::last_search`] so their status line can render a hint
    /// and so `n` / `N` have something to repeat.
    pub(super) last_search: Option<String>,
    /// Direction of the last committed search. `n` repeats this; `N`
    /// inverts it. Defaults to forward so a never-searched buffer's
    /// `n` still walks downward.
    pub(super) last_search_forward: bool,
    /// Back half of the jumplist — `Ctrl-o` pops from here. Populated
    /// with the pre-motion cursor when a "big jump" motion fires
    /// (`gg`/`G`, `%`, `*`/`#`, `n`/`N`, `H`/`M`/`L`, committed `/` or
    /// `?`). Capped at 100 entries.
    pub(super) jump_back: Vec<(usize, usize)>,
    /// Forward half — `Ctrl-i` pops from here. Cleared by any new big
    /// jump, matching vim's "branch off trims forward history" rule.
    pub(super) jump_fwd: Vec<(usize, usize)>,
    /// Set by `Ctrl-R` in insert mode while waiting for the register
    /// selector. The next typed char names the register; its contents
    /// are inserted inline at the cursor and the flag clears.
    pub(super) insert_pending_register: bool,
    /// Stashed start position for the `[` mark on a Change operation.
    /// Set to `top` before the cut in `run_operator_over_range` (Change
    /// arm); consumed by `finish_insert_session` on Esc-from-insert
    /// when the reason is `AfterChange`. Mirrors vim's `:h '[` / `:h ']`
    /// rule that `[` = start of change, `]` = last typed char on exit.
    pub(super) change_mark_start: Option<(usize, usize)>,
    /// Bounded history of committed `/` / `?` search patterns. Newest
    /// entries are at the back; capped at [`SEARCH_HISTORY_MAX`] to
    /// avoid unbounded growth on long sessions.
    pub(super) search_history: Vec<String>,
    /// Index into `search_history` while the user walks past patterns
    /// in the prompt via `Ctrl-P` / `Ctrl-N`. `None` outside that walk
    /// — typing or backspacing in the prompt resets it so the next
    /// `Ctrl-P` starts from the most recent entry again.
    pub(super) search_history_cursor: Option<usize>,
    /// Wall-clock instant of the last keystroke. Drives the
    /// `:set timeoutlen` multi-key timeout — if `now() - last_input_at`
    /// exceeds the configured budget, any pending prefix is cleared
    /// before the new key dispatches. `None` before the first key.
    /// 0.0.29 (Patch B): `:set timeoutlen` math now reads
    /// [`crate::types::Host::now`] via `last_input_host_at`. This
    /// `Instant`-flavoured field stays for snapshot tests that still
    /// observe it directly.
    pub(super) last_input_at: Option<std::time::Instant>,
    /// `Host::now()` reading at the last keystroke. Drives
    /// `:set timeoutlen` so macro replay / headless drivers stay
    /// deterministic regardless of wall-clock skew.
    pub(super) last_input_host_at: Option<core::time::Duration>,
}

const SEARCH_HISTORY_MAX: usize = 100;
pub(crate) const CHANGE_LIST_MAX: usize = 100;

/// Active `/` or `?` search prompt. Text mutations drive the textarea's
/// live search pattern so matches highlight as the user types.
#[derive(Debug, Clone)]
pub struct SearchPrompt {
    pub text: String,
    pub cursor: usize,
    pub forward: bool,
}

#[derive(Debug, Clone)]
struct InsertSession {
    count: usize,
    /// Min/max row visited during this session. Widens on every key.
    row_min: usize,
    row_max: usize,
    /// Snapshot of the full buffer at session entry. Used to diff the
    /// affected row window at finish without being fooled by cursor
    /// navigation through rows the user never edited.
    before_lines: Vec<String>,
    reason: InsertReason,
}

#[derive(Debug, Clone)]
enum InsertReason {
    /// Plain entry via i/I/a/A — recorded as `InsertAt`.
    Enter(InsertEntry),
    /// Entry via `o`/`O` — records OpenLine on Esc.
    Open { above: bool },
    /// Entry via an operator's change side-effect. Retro-fills the
    /// stored last-change's `inserted` field on Esc.
    AfterChange,
    /// Entry via `C` (delete to EOL + insert).
    DeleteToEol,
    /// Entry via an insert triggered during dot-replay — don't touch
    /// last_change because the outer replay will restore it.
    ReplayOnly,
    /// `I` or `A` from VisualBlock: insert the typed text at `col` on
    /// every row in `top..=bot`. `col` is the start column for `I`, the
    /// one-past-block-end column for `A`.
    BlockEdge { top: usize, bot: usize, col: usize },
    /// `c` from VisualBlock: block content deleted, then user types
    /// replacement text replicated across all block rows on Esc. Cursor
    /// advances to the last typed char after replication (unlike BlockEdge
    /// which leaves cursor at the insertion column).
    BlockChange { top: usize, bot: usize, col: usize },
    /// `R` — Replace mode. Each typed char overwrites the cell under
    /// the cursor instead of inserting; at end-of-line the session
    /// falls through to insert (same as vim).
    Replace,
}

/// Saved visual-mode anchor + cursor for `gv` (re-enters the last
/// visual selection). `mode` carries which visual flavour to
/// restore; `anchor` / `cursor` mean different things per flavour:
///
/// - `Visual`     — `anchor` is the char-wise visual anchor.
/// - `VisualLine` — `anchor.0` is the `visual_line_anchor` row;
///   `anchor.1` is unused.
/// - `VisualBlock`— `anchor` is `block_anchor`, `block_vcol` is the
///   sticky vcol that survives j/k clamping.
#[derive(Debug, Clone, Copy)]
pub(super) struct LastVisual {
    pub mode: Mode,
    pub anchor: (usize, usize),
    pub cursor: (usize, usize),
    pub block_vcol: usize,
}

impl VimState {
    pub fn public_mode(&self) -> VimMode {
        match self.mode {
            Mode::Normal => VimMode::Normal,
            Mode::Insert => VimMode::Insert,
            Mode::Visual => VimMode::Visual,
            Mode::VisualLine => VimMode::VisualLine,
            Mode::VisualBlock => VimMode::VisualBlock,
        }
    }

    pub fn force_normal(&mut self) {
        self.mode = Mode::Normal;
        self.pending = Pending::None;
        self.count = 0;
        self.insert_session = None;
    }

    /// Reset every prefix-tracking field so the next keystroke starts
    /// a fresh sequence. Drives `:set timeoutlen` — when the user
    /// pauses past the configured budget, [`crate::vim::step`] calls
    /// this before dispatching the new key.
    ///
    /// Resets: `pending`, `count`, `pending_register`,
    /// `insert_pending_register`. Does NOT touch `mode`,
    /// `insert_session`, marks, jump list, or visual anchors —
    /// those aren't part of the in-flight chord.
    pub(crate) fn clear_pending_prefix(&mut self) {
        self.pending = Pending::None;
        self.count = 0;
        self.pending_register = None;
        self.insert_pending_register = false;
    }

    pub fn is_visual(&self) -> bool {
        matches!(
            self.mode,
            Mode::Visual | Mode::VisualLine | Mode::VisualBlock
        )
    }

    pub fn is_visual_char(&self) -> bool {
        self.mode == Mode::Visual
    }

    pub fn enter_visual(&mut self, anchor: (usize, usize)) {
        self.visual_anchor = anchor;
        self.mode = Mode::Visual;
    }

    /// The pending repeat count (typed digits before a motion/operator),
    /// or `None` when no digits are pending. Zero is treated as absent.
    pub(crate) fn pending_count_val(&self) -> Option<u32> {
        if self.count == 0 {
            None
        } else {
            Some(self.count as u32)
        }
    }

    /// `true` when an in-flight chord is awaiting more keys. Inverse of
    /// `matches!(self.pending, Pending::None)`.
    pub(crate) fn is_chord_pending(&self) -> bool {
        !matches!(self.pending, Pending::None)
    }

    /// Return a single char representing the pending operator, if any.
    /// Used by host apps (status line "showcmd" area) to display e.g.
    /// `d`, `y`, `c` while waiting for a motion.
    pub(crate) fn pending_op_char(&self) -> Option<char> {
        let op = match &self.pending {
            Pending::Op { op, .. }
            | Pending::OpTextObj { op, .. }
            | Pending::OpG { op, .. }
            | Pending::OpFind { op, .. } => Some(*op),
            _ => None,
        };
        op.map(|o| match o {
            Operator::Delete => 'd',
            Operator::Change => 'c',
            Operator::Yank => 'y',
            Operator::Uppercase => 'U',
            Operator::Lowercase => 'u',
            Operator::ToggleCase => '~',
            Operator::Indent => '>',
            Operator::Outdent => '<',
            Operator::Fold => 'z',
            Operator::Reflow => 'q',
        })
    }
}

// ─── Entry point ───────────────────────────────────────────────────────────

/// Open the `/` (forward) or `?` (backward) search prompt. Clears any
/// live search highlight until the user commits a query. `last_search`
/// is preserved so an empty `<CR>` can re-run the previous pattern.
fn enter_search<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>, forward: bool) {
    ed.vim.search_prompt = Some(SearchPrompt {
        text: String::new(),
        cursor: 0,
        forward,
    });
    ed.vim.search_history_cursor = None;
    // 0.0.37: clear via the engine search state (the buffer-side
    // bridge from 0.0.35 was removed in this patch — the `BufferView`
    // renderer reads the pattern from `Editor::search_state()`).
    ed.set_search_pattern(None);
}

/// Compile `pattern` into a regex and push it onto the migration
/// buffer's search state. Invalid patterns clear the highlight (the
/// user is mid-typing a regex like `[` and we don't want to flash an
/// error).
fn push_search_pattern<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    pattern: &str,
) {
    let compiled = if pattern.is_empty() {
        None
    } else {
        // `:set ignorecase` flips every search pattern to case-insensitive
        // unless the user already prefixed an explicit `(?i)` / `(?-i)`
        // (regex crate honours those even when we layer another `(?i)`).
        // `:set smartcase` re-enables case sensitivity for any pattern
        // that contains an uppercase letter — matches vim's combined
        // `ignorecase` + `smartcase` behaviour.
        let case_insensitive = ed.settings().ignore_case
            && !(ed.settings().smartcase && pattern.chars().any(|c| c.is_uppercase()));
        let effective: std::borrow::Cow<'_, str> = if case_insensitive {
            std::borrow::Cow::Owned(format!("(?i){pattern}"))
        } else {
            std::borrow::Cow::Borrowed(pattern)
        };
        regex::Regex::new(&effective).ok()
    };
    let wrap = ed.settings().wrapscan;
    // 0.0.37: search FSM lives entirely on Editor — pattern + wrap
    // policy + per-row match cache. The `Search` trait impl always
    // wraps; engine code honours `wrap_around` before invoking it.
    ed.set_search_pattern(compiled);
    ed.search_state_mut().wrap_around = wrap;
}

fn step_search_prompt<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    // Ctrl-P / Ctrl-N (and Up / Down) walk the search history. Handled
    // before the regular char/backspace branches so `Ctrl-P` doesn't
    // type a literal `p`.
    let history_dir = match (input.key, input.ctrl) {
        (Key::Char('p'), true) | (Key::Up, _) => Some(-1),
        (Key::Char('n'), true) | (Key::Down, _) => Some(1),
        _ => None,
    };
    if let Some(dir) = history_dir {
        walk_search_history(ed, dir);
        return true;
    }
    match input.key {
        Key::Esc => {
            // Cancel. Drop the prompt but keep the highlighted matches
            // so `n` / `N` can repeat whatever was typed.
            let text = ed
                .vim
                .search_prompt
                .take()
                .map(|p| p.text)
                .unwrap_or_default();
            if !text.is_empty() {
                ed.vim.last_search = Some(text);
            }
            ed.vim.search_history_cursor = None;
        }
        Key::Enter => {
            let prompt = ed.vim.search_prompt.take();
            if let Some(p) = prompt {
                // Empty `/<CR>` (or `?<CR>`) re-runs the previous search
                // pattern in the prompt's direction — vim parity.
                let pattern = if p.text.is_empty() {
                    ed.vim.last_search.clone()
                } else {
                    Some(p.text.clone())
                };
                if let Some(pattern) = pattern {
                    push_search_pattern(ed, &pattern);
                    let pre = ed.cursor();
                    if p.forward {
                        ed.search_advance_forward(true);
                    } else {
                        ed.search_advance_backward(true);
                    }
                    ed.push_buffer_cursor_to_textarea();
                    if ed.cursor() != pre {
                        push_jump(ed, pre);
                    }
                    record_search_history(ed, &pattern);
                    ed.vim.last_search = Some(pattern);
                    ed.vim.last_search_forward = p.forward;
                }
            }
            ed.vim.search_history_cursor = None;
        }
        Key::Backspace => {
            ed.vim.search_history_cursor = None;
            let new_text = ed.vim.search_prompt.as_mut().and_then(|p| {
                if p.text.pop().is_some() {
                    p.cursor = p.text.chars().count();
                    Some(p.text.clone())
                } else {
                    None
                }
            });
            if let Some(text) = new_text {
                push_search_pattern(ed, &text);
            }
        }
        Key::Char(c) => {
            ed.vim.search_history_cursor = None;
            let new_text = ed.vim.search_prompt.as_mut().map(|p| {
                p.text.push(c);
                p.cursor = p.text.chars().count();
                p.text.clone()
            });
            if let Some(text) = new_text {
                push_search_pattern(ed, &text);
            }
        }
        _ => {}
    }
    true
}

/// `g;` / `g,` body. `dir = -1` walks toward older entries (g;),
/// `dir = 1` toward newer (g,). `count` repeats the step. Stops at
/// the ends of the ring; off-ring positions are silently ignored.
fn walk_change_list<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    dir: isize,
    count: usize,
) {
    if ed.vim.change_list.is_empty() {
        return;
    }
    let len = ed.vim.change_list.len();
    let mut idx: isize = match (ed.vim.change_list_cursor, dir) {
        (None, -1) => len as isize - 1,
        (None, 1) => return, // already past the newest entry
        (Some(i), -1) => i as isize - 1,
        (Some(i), 1) => i as isize + 1,
        _ => return,
    };
    for _ in 1..count {
        let next = idx + dir;
        if next < 0 || next >= len as isize {
            break;
        }
        idx = next;
    }
    if idx < 0 || idx >= len as isize {
        return;
    }
    let idx = idx as usize;
    ed.vim.change_list_cursor = Some(idx);
    let (row, col) = ed.vim.change_list[idx];
    ed.jump_cursor(row, col);
}

/// Push `pattern` onto the search history. Skips the push when the
/// most recent entry already matches (consecutive dedupe) and trims
/// the oldest entries beyond [`SEARCH_HISTORY_MAX`].
fn record_search_history<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    pattern: &str,
) {
    if pattern.is_empty() {
        return;
    }
    if ed.vim.search_history.last().map(String::as_str) == Some(pattern) {
        return;
    }
    ed.vim.search_history.push(pattern.to_string());
    let len = ed.vim.search_history.len();
    if len > SEARCH_HISTORY_MAX {
        ed.vim.search_history.drain(0..len - SEARCH_HISTORY_MAX);
    }
}

/// Replace the prompt text with the next entry in the search history.
/// `dir = -1` walks toward older entries (`Ctrl-P` / `Up`); `dir = 1`
/// toward newer ones (`Ctrl-N` / `Down`). Stops at the ends of the
/// history; the user can keep pressing the key without effect rather
/// than wrapping around.
fn walk_search_history<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>, dir: isize) {
    if ed.vim.search_history.is_empty() || ed.vim.search_prompt.is_none() {
        return;
    }
    let len = ed.vim.search_history.len();
    let next_idx = match (ed.vim.search_history_cursor, dir) {
        (None, -1) => Some(len - 1),
        (None, 1) => return, // already past the newest entry
        (Some(i), -1) => i.checked_sub(1),
        (Some(i), 1) if i + 1 < len => Some(i + 1),
        _ => None,
    };
    let Some(idx) = next_idx else {
        return;
    };
    ed.vim.search_history_cursor = Some(idx);
    let text = ed.vim.search_history[idx].clone();
    if let Some(prompt) = ed.vim.search_prompt.as_mut() {
        prompt.cursor = text.chars().count();
        prompt.text = text.clone();
    }
    push_search_pattern(ed, &text);
}

pub fn step<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>, input: Input) -> bool {
    // Phase 7f port: any cursor / content the host changed between
    // steps (mouse jumps, paste, programmatic set_content, …) needs
    // to land in the migration buffer before motion handlers that
    // call into `Buffer::move_*` see a stale state.
    ed.sync_buffer_content_from_textarea();
    // `:set timeoutlen` — if the user paused longer than the budget
    // since the last keystroke and a chord is in flight, drop the
    // pending prefix so the new key starts fresh. 0.0.29 (Patch B):
    // chord-timeout math now reads `Host::now()` so macro replay /
    // headless drivers stay deterministic. The legacy
    // `Instant::now()`-backed `last_input_at` field is retained for
    // snapshot tests that still observe it.
    let now = std::time::Instant::now();
    let host_now = ed.host.now();
    let timed_out = match ed.vim.last_input_host_at {
        Some(prev) => host_now.saturating_sub(prev) > ed.settings.timeout_len,
        None => false,
    };
    if timed_out {
        let chord_in_flight = !matches!(ed.vim.pending, Pending::None)
            || ed.vim.count != 0
            || ed.vim.pending_register.is_some()
            || ed.vim.insert_pending_register;
        if chord_in_flight {
            ed.vim.clear_pending_prefix();
        }
    }
    ed.vim.last_input_at = Some(now);
    ed.vim.last_input_host_at = Some(host_now);
    // Macro stop: a bare `q` ends an active recording before any
    // other handler sees the key (so `q` itself doesn't get
    // recorded). Replays don't trigger this — they finish on their
    // own when the captured key list runs out.
    if ed.vim.recording_macro.is_some()
        && !ed.vim.replaying_macro
        && matches!(ed.vim.pending, Pending::None)
        && ed.vim.mode != Mode::Insert
        && input.key == Key::Char('q')
        && !input.ctrl
        && !input.alt
    {
        let reg = ed.vim.recording_macro.take().unwrap();
        let keys = std::mem::take(&mut ed.vim.recording_keys);
        let text = crate::input::encode_macro(&keys);
        ed.set_named_register_text(reg.to_ascii_lowercase(), text);
        return true;
    }
    // Search prompt eats all keys until Enter / Esc.
    if ed.vim.search_prompt.is_some() {
        return step_search_prompt(ed, input);
    }
    // Snapshot whether this step is consuming the register-name half
    // of a macro chord. The recorder hook below uses this to skip
    // the chord's bookkeeping keys (`q{reg}` open and `@{reg}` open).
    let pending_was_macro_chord = matches!(
        ed.vim.pending,
        Pending::RecordMacroTarget | Pending::PlayMacroTarget { .. }
    );
    let was_insert = ed.vim.mode == Mode::Insert;
    // Capture pre-step visual snapshot so a visual → normal transition
    // can stash the selection for `gv` re-entry.
    let pre_visual_snapshot = match ed.vim.mode {
        Mode::Visual => Some(LastVisual {
            mode: Mode::Visual,
            anchor: ed.vim.visual_anchor,
            cursor: ed.cursor(),
            block_vcol: 0,
        }),
        Mode::VisualLine => Some(LastVisual {
            mode: Mode::VisualLine,
            anchor: (ed.vim.visual_line_anchor, 0),
            cursor: ed.cursor(),
            block_vcol: 0,
        }),
        Mode::VisualBlock => Some(LastVisual {
            mode: Mode::VisualBlock,
            anchor: ed.vim.block_anchor,
            cursor: ed.cursor(),
            block_vcol: ed.vim.block_vcol,
        }),
        _ => None,
    };
    let consumed = match ed.vim.mode {
        Mode::Insert => step_insert(ed, input),
        _ => step_normal(ed, input),
    };
    if let Some(snap) = pre_visual_snapshot
        && !matches!(
            ed.vim.mode,
            Mode::Visual | Mode::VisualLine | Mode::VisualBlock
        )
    {
        // Set the `<` / `>` marks so ex commands like `:'<,'>sort` resolve
        // their range. Per `:h v_:` the mark positions depend on the visual
        // submode:
        //
        // * Visual (charwise): position-ordered. `<` = lower (row, col),
        //   `>` = higher. Tuple comparison works because the selection is
        //   contiguous text.
        // * VisualLine: `<` snaps to (top_row, 0), `>` snaps to
        //   (bot_row, last_col_of_that_line). Vim treats linewise
        //   selections as full lines so the column components are
        //   normalised to line edges.
        // * VisualBlock: corners. `<` = (min_row, min_col),
        //   `>` = (max_row, max_col) computed independently — the cursor
        //   may sit on any corner so tuple ordering would mis-place the
        //   columns when the selection grew leftward.
        let (lo, hi) = match snap.mode {
            Mode::Visual => {
                if snap.anchor <= snap.cursor {
                    (snap.anchor, snap.cursor)
                } else {
                    (snap.cursor, snap.anchor)
                }
            }
            Mode::VisualLine => {
                let r_lo = snap.anchor.0.min(snap.cursor.0);
                let r_hi = snap.anchor.0.max(snap.cursor.0);
                let last_col = ed
                    .buffer()
                    .lines()
                    .get(r_hi)
                    .map(|l| l.chars().count().saturating_sub(1))
                    .unwrap_or(0);
                ((r_lo, 0), (r_hi, last_col))
            }
            Mode::VisualBlock => {
                let (r1, c1) = snap.anchor;
                let (r2, c2) = snap.cursor;
                ((r1.min(r2), c1.min(c2)), (r1.max(r2), c1.max(c2)))
            }
            _ => {
                // Defensive: pre_visual_snapshot only stores visual modes,
                // so this arm is unreachable in practice.
                if snap.anchor <= snap.cursor {
                    (snap.anchor, snap.cursor)
                } else {
                    (snap.cursor, snap.anchor)
                }
            }
        };
        ed.set_mark('<', lo);
        ed.set_mark('>', hi);
        ed.vim.last_visual = Some(snap);
    }
    // Ctrl-o in insert mode queues a single normal-mode command; once
    // that command finishes (pending cleared, not in operator / visual),
    // drop back to insert without replaying the insert session.
    if !was_insert
        && ed.vim.one_shot_normal
        && ed.vim.mode == Mode::Normal
        && matches!(ed.vim.pending, Pending::None)
    {
        ed.vim.one_shot_normal = false;
        ed.vim.mode = Mode::Insert;
    }
    // Phase 7c: every step ends with the migration buffer mirroring
    // the textarea's content + cursor + viewport. Edit-emitting paths
    // (insert_char, delete_char, …) inside `step_insert` /
    // `step_normal` thus all flow through here without each call
    // site needing to remember to sync.
    ed.sync_buffer_content_from_textarea();
    // Scroll viewport to keep cursor on-screen, honouring the same
    // `SCROLLOFF` margin the mouse-driven scroll uses. Skip when
    // the user just pinned the viewport with `zz` / `zt` / `zb`.
    if !ed.vim.viewport_pinned {
        ed.ensure_cursor_in_scrolloff();
    }
    ed.vim.viewport_pinned = false;
    // Recorder hook: append every consumed input to the active
    // recording (if any) so the replay reproduces the same sequence.
    // Skip the chord that started the recording (`q{reg}` open) and
    // skip during replay so a macro doesn't capture itself.
    if ed.vim.recording_macro.is_some()
        && !ed.vim.replaying_macro
        && input.key != Key::Char('q')
        && !pending_was_macro_chord
    {
        ed.vim.recording_keys.push(input);
    }
    consumed
}

// ─── Insert mode ───────────────────────────────────────────────────────────

fn step_insert<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    // `Ctrl-R {reg}` paste — the previous keystroke armed the wait. Any
    // non-char key cancels (matches vim, which beeps on selectors like
    // Esc and re-emits the literal text otherwise).
    if ed.vim.insert_pending_register {
        ed.vim.insert_pending_register = false;
        if let Key::Char(c) = input.key
            && !input.ctrl
        {
            insert_register_text(ed, c);
        }
        return true;
    }

    if input.key == Key::Esc {
        finish_insert_session(ed);
        ed.vim.mode = Mode::Normal;
        // Vim convention: pull the cursor back one cell on exit when
        // possible. Sticky column then mirrors the *visible* post-Back
        // column so the next vertical motion lands where the user
        // actually sees the cursor — not one cell to the right.
        let col = ed.cursor().1;
        // Record the pre-step-back cursor as the `gi` target. vim's `gi`
        // re-enters insert at this position (the cell the cursor occupied
        // when insert mode was active), matching vim's `:h gi` / `'^` mark.
        ed.vim.last_insert_pos = Some(ed.cursor());
        if col > 0 {
            crate::motions::move_left(&mut ed.buffer, 1);
            ed.push_buffer_cursor_to_textarea();
        }
        ed.sticky_col = Some(ed.cursor().1);
        return true;
    }

    // Ctrl-prefixed insert-mode shortcuts.
    if input.ctrl {
        match input.key {
            Key::Char('w') => {
                use hjkl_buffer::{Edit, MotionKind};
                ed.sync_buffer_content_from_textarea();
                let cursor = buf_cursor_pos(&ed.buffer);
                if cursor.row == 0 && cursor.col == 0 {
                    return true;
                }
                // Find the previous word start by stepping the buffer
                // cursor (vim `b` semantics) and snapshot it.
                crate::motions::move_word_back(&mut ed.buffer, false, 1, &ed.settings.iskeyword);
                let word_start = buf_cursor_pos(&ed.buffer);
                if word_start == cursor {
                    return true;
                }
                buf_set_cursor_pos(&mut ed.buffer, cursor);
                ed.mutate_edit(Edit::DeleteRange {
                    start: word_start,
                    end: cursor,
                    kind: MotionKind::Char,
                });
                ed.push_buffer_cursor_to_textarea();
                return true;
            }
            Key::Char('u') => {
                use hjkl_buffer::{Edit, MotionKind, Position};
                ed.sync_buffer_content_from_textarea();
                let cursor = buf_cursor_pos(&ed.buffer);
                if cursor.col > 0 {
                    ed.mutate_edit(Edit::DeleteRange {
                        start: Position::new(cursor.row, 0),
                        end: cursor,
                        kind: MotionKind::Char,
                    });
                    ed.push_buffer_cursor_to_textarea();
                }
                return true;
            }
            Key::Char('h') => {
                use hjkl_buffer::{Edit, MotionKind, Position};
                ed.sync_buffer_content_from_textarea();
                let cursor = buf_cursor_pos(&ed.buffer);
                if cursor.col > 0 {
                    ed.mutate_edit(Edit::DeleteRange {
                        start: Position::new(cursor.row, cursor.col - 1),
                        end: cursor,
                        kind: MotionKind::Char,
                    });
                } else if cursor.row > 0 {
                    let prev_row = cursor.row - 1;
                    let prev_chars = buf_line_chars(&ed.buffer, prev_row);
                    ed.mutate_edit(Edit::JoinLines {
                        row: prev_row,
                        count: 1,
                        with_space: false,
                    });
                    buf_set_cursor_rc(&mut ed.buffer, prev_row, prev_chars);
                }
                ed.push_buffer_cursor_to_textarea();
                return true;
            }
            Key::Char('o') => {
                // One-shot normal: leave insert mode for the next full
                // normal-mode command, then come back.
                ed.vim.one_shot_normal = true;
                ed.vim.mode = Mode::Normal;
                return true;
            }
            Key::Char('r') => {
                // Arm the register selector — the next typed char picks
                // a slot and pastes its text inline.
                ed.vim.insert_pending_register = true;
                return true;
            }
            Key::Char('t') => {
                // Insert-mode indent: prepend one shiftwidth to the
                // current line's leading whitespace. Cursor shifts
                // right by the same amount so the user keeps typing
                // at their logical position.
                let (row, col) = ed.cursor();
                let sw = ed.settings().shiftwidth;
                indent_rows(ed, row, row, 1);
                ed.jump_cursor(row, col + sw);
                return true;
            }
            Key::Char('d') => {
                // Insert-mode outdent: drop up to one shiftwidth of
                // leading whitespace. Cursor shifts left by the amount
                // actually stripped.
                let (row, col) = ed.cursor();
                let before_len = buf_line_bytes(&ed.buffer, row);
                outdent_rows(ed, row, row, 1);
                let after_len = buf_line_bytes(&ed.buffer, row);
                let stripped = before_len.saturating_sub(after_len);
                let new_col = col.saturating_sub(stripped);
                ed.jump_cursor(row, new_col);
                return true;
            }
            _ => {}
        }
    }

    // Widen the session's visited row window *before* handling the key
    // so navigation-only keystrokes (arrow keys) still extend the range.
    let (row, _) = ed.cursor();
    if let Some(ref mut session) = ed.vim.insert_session {
        session.row_min = session.row_min.min(row);
        session.row_max = session.row_max.max(row);
    }
    let mutated = handle_insert_key(ed, input);
    if mutated {
        ed.mark_content_dirty();
        let (row, _) = ed.cursor();
        if let Some(ref mut session) = ed.vim.insert_session {
            session.row_min = session.row_min.min(row);
            session.row_max = session.row_max.max(row);
        }
    }
    true
}

/// `Ctrl-R {reg}` body — insert the named register's contents at the
/// cursor as charwise text. Embedded newlines split lines naturally via
/// `Edit::InsertStr`. Unknown selectors and empty slots are no-ops so
/// stray keystrokes don't mutate the buffer.
fn insert_register_text<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    selector: char,
) {
    use hjkl_buffer::Edit;
    let text = match ed.registers().read(selector) {
        Some(slot) if !slot.text.is_empty() => slot.text.clone(),
        _ => return,
    };
    ed.sync_buffer_content_from_textarea();
    let cursor = buf_cursor_pos(&ed.buffer);
    ed.mutate_edit(Edit::InsertStr {
        at: cursor,
        text: text.clone(),
    });
    // Advance cursor to the end of the inserted payload — multi-line
    // pastes land on the last inserted row at the post-text column.
    let mut row = cursor.row;
    let mut col = cursor.col;
    for ch in text.chars() {
        if ch == '\n' {
            row += 1;
            col = 0;
        } else {
            col += 1;
        }
    }
    buf_set_cursor_rc(&mut ed.buffer, row, col);
    ed.push_buffer_cursor_to_textarea();
    ed.mark_content_dirty();
    if let Some(ref mut session) = ed.vim.insert_session {
        session.row_min = session.row_min.min(row);
        session.row_max = session.row_max.max(row);
    }
}

/// Compute the indent string to insert at the start of a new line
/// after Enter is pressed at `cursor`. Walks the smartindent rules:
///
/// - autoindent off → empty string
/// - autoindent on  → copy prev line's leading whitespace
/// - smartindent on → bump one `shiftwidth` if prev line's last
///   non-whitespace char is `{` / `(` / `[`
///
/// Indent unit (used for the smartindent bump):
///
/// - `expandtab && softtabstop > 0` → `softtabstop` spaces
/// - `expandtab` → `shiftwidth` spaces
/// - `!expandtab` → one literal `\t`
///
/// This is the placeholder for a future tree-sitter indent provider:
/// when a language has an `indents.scm` query, the engine will route
/// the same call through that provider and only fall back to this
/// heuristic when no query matches.
pub(super) fn compute_enter_indent(settings: &crate::editor::Settings, prev_line: &str) -> String {
    if !settings.autoindent {
        return String::new();
    }
    // Copy the prev line's leading whitespace (autoindent base).
    let base: String = prev_line
        .chars()
        .take_while(|c| *c == ' ' || *c == '\t')
        .collect();

    if settings.smartindent {
        // If the last non-whitespace character is an open bracket, bump
        // indent by one unit. This is the heuristic seam: a tree-sitter
        // `indents.scm` provider would replace this branch.
        let last_non_ws = prev_line.chars().rev().find(|c| !c.is_whitespace());
        if matches!(last_non_ws, Some('{' | '(' | '[')) {
            let unit = if settings.expandtab {
                if settings.softtabstop > 0 {
                    " ".repeat(settings.softtabstop)
                } else {
                    " ".repeat(settings.shiftwidth)
                }
            } else {
                "\t".to_string()
            };
            return format!("{base}{unit}");
        }
    }

    base
}

/// Strip one indent unit from the beginning of `line` and insert `ch`
/// instead. Returns `true` when it consumed the keystroke (dedent +
/// insert), `false` when the caller should insert normally.
///
/// Dedent fires when:
///   - `smartindent` is on
///   - `ch` is `}` / `)` / `]`
///   - all bytes BEFORE the cursor on the current line are whitespace
///   - there is at least one full indent unit of leading whitespace
fn try_dedent_close_bracket<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    cursor: hjkl_buffer::Position,
    ch: char,
) -> bool {
    use hjkl_buffer::{Edit, MotionKind, Position};

    if !ed.settings.smartindent {
        return false;
    }
    if !matches!(ch, '}' | ')' | ']') {
        return false;
    }

    let line = match buf_line(&ed.buffer, cursor.row) {
        Some(l) => l.to_string(),
        None => return false,
    };

    // All chars before cursor must be whitespace.
    let before: String = line.chars().take(cursor.col).collect();
    if !before.chars().all(|c| c == ' ' || c == '\t') {
        return false;
    }
    if before.is_empty() {
        // Nothing to strip — just insert normally (cursor at col 0).
        return false;
    }

    // Compute indent unit.
    let unit_len: usize = if ed.settings.expandtab {
        if ed.settings.softtabstop > 0 {
            ed.settings.softtabstop
        } else {
            ed.settings.shiftwidth
        }
    } else {
        // Tab: one literal tab character.
        1
    };

    // Check there's at least one full unit to strip.
    let strip_len = if ed.settings.expandtab {
        // Count leading spaces; need at least `unit_len`.
        let spaces = before.chars().filter(|c| *c == ' ').count();
        if spaces < unit_len {
            return false;
        }
        unit_len
    } else {
        // noexpandtab: strip one leading tab.
        if !before.starts_with('\t') {
            return false;
        }
        1
    };

    // Delete the leading `strip_len` chars of the current line.
    ed.mutate_edit(Edit::DeleteRange {
        start: Position::new(cursor.row, 0),
        end: Position::new(cursor.row, strip_len),
        kind: MotionKind::Char,
    });
    // Insert the close bracket at column 0 (after the delete the cursor
    // is still positioned at the end of the remaining whitespace; the
    // delete moved the text so the cursor is now at col = before.len() -
    // strip_len).
    let new_col = cursor.col.saturating_sub(strip_len);
    ed.mutate_edit(Edit::InsertChar {
        at: Position::new(cursor.row, new_col),
        ch,
    });
    true
}

/// Insert-mode key dispatcher backed by the migration buffer. Replaces
/// the historical `textarea.input(input)` call so the textarea field
/// can be ripped at the end of Phase 7f. PageUp / PageDown still flow
/// through the textarea (they're scroll-only with no buffer side
/// effect); every other navigation + edit key lands on `Buffer`.
/// Returns true when the buffer mutated.
fn handle_insert_key<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    use hjkl_buffer::{Edit, MotionKind, Position};
    ed.sync_buffer_content_from_textarea();
    let cursor = buf_cursor_pos(&ed.buffer);
    let line_chars = buf_line_chars(&ed.buffer, cursor.row);
    // Replace mode: overstrike the cell at the cursor instead of
    // inserting. At end-of-line, fall through to plain insert (vim
    // appends past the line).
    let in_replace = matches!(
        ed.vim.insert_session.as_ref().map(|s| &s.reason),
        Some(InsertReason::Replace)
    );
    let mutated = match input.key {
        Key::Char(c) if in_replace && cursor.col < line_chars => {
            ed.mutate_edit(Edit::DeleteRange {
                start: cursor,
                end: Position::new(cursor.row, cursor.col + 1),
                kind: MotionKind::Char,
            });
            ed.mutate_edit(Edit::InsertChar { at: cursor, ch: c });
            true
        }
        Key::Char(c) => {
            if !try_dedent_close_bracket(ed, cursor, c) {
                ed.mutate_edit(Edit::InsertChar { at: cursor, ch: c });
            }
            true
        }
        Key::Enter => {
            let prev_line = buf_line(&ed.buffer, cursor.row)
                .unwrap_or_default()
                .to_string();
            let indent = compute_enter_indent(&ed.settings, &prev_line);
            let text = format!("\n{indent}");
            ed.mutate_edit(Edit::InsertStr { at: cursor, text });
            true
        }
        Key::Tab => {
            if ed.settings.expandtab {
                // With softtabstop > 0, fill to the next sts boundary.
                // Otherwise insert a full tabstop run.
                let sts = ed.settings.softtabstop;
                let n = if sts > 0 {
                    sts - (cursor.col % sts)
                } else {
                    ed.settings.tabstop.max(1)
                };
                ed.mutate_edit(Edit::InsertStr {
                    at: cursor,
                    text: " ".repeat(n),
                });
            } else {
                ed.mutate_edit(Edit::InsertChar {
                    at: cursor,
                    ch: '\t',
                });
            }
            true
        }
        Key::Backspace => {
            // Softtabstop: if the N chars before the cursor are all spaces
            // and the cursor sits on an sts-aligned column, delete the run
            // as a single unit (vim's "backspace deletes a soft tab" feel).
            let sts = ed.settings.softtabstop;
            if sts > 0 && cursor.col >= sts && cursor.col.is_multiple_of(sts) {
                let line = buf_line(&ed.buffer, cursor.row).unwrap_or_default();
                let chars: Vec<char> = line.chars().collect();
                let run_start = cursor.col - sts;
                if (run_start..cursor.col).all(|i| chars.get(i).copied() == Some(' ')) {
                    ed.mutate_edit(Edit::DeleteRange {
                        start: Position::new(cursor.row, run_start),
                        end: cursor,
                        kind: MotionKind::Char,
                    });
                    return true;
                }
            }
            if cursor.col > 0 {
                ed.mutate_edit(Edit::DeleteRange {
                    start: Position::new(cursor.row, cursor.col - 1),
                    end: cursor,
                    kind: MotionKind::Char,
                });
                true
            } else if cursor.row > 0 {
                let prev_row = cursor.row - 1;
                let prev_chars = buf_line_chars(&ed.buffer, prev_row);
                ed.mutate_edit(Edit::JoinLines {
                    row: prev_row,
                    count: 1,
                    with_space: false,
                });
                buf_set_cursor_rc(&mut ed.buffer, prev_row, prev_chars);
                true
            } else {
                false
            }
        }
        Key::Delete => {
            if cursor.col < line_chars {
                ed.mutate_edit(Edit::DeleteRange {
                    start: cursor,
                    end: Position::new(cursor.row, cursor.col + 1),
                    kind: MotionKind::Char,
                });
                true
            } else if cursor.row + 1 < buf_row_count(&ed.buffer) {
                ed.mutate_edit(Edit::JoinLines {
                    row: cursor.row,
                    count: 1,
                    with_space: false,
                });
                buf_set_cursor_pos(&mut ed.buffer, cursor);
                true
            } else {
                false
            }
        }
        Key::Left => {
            crate::motions::move_left(&mut ed.buffer, 1);
            break_undo_group_in_insert(ed);
            false
        }
        Key::Right => {
            // Insert mode allows the cursor one past the last char so the
            // next typed letter appends — use the operator-context move.
            crate::motions::move_right_to_end(&mut ed.buffer, 1);
            break_undo_group_in_insert(ed);
            false
        }
        Key::Up => {
            let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
            crate::motions::move_up(&mut ed.buffer, &folds, 1, &mut ed.sticky_col);
            break_undo_group_in_insert(ed);
            false
        }
        Key::Down => {
            let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
            crate::motions::move_down(&mut ed.buffer, &folds, 1, &mut ed.sticky_col);
            break_undo_group_in_insert(ed);
            false
        }
        Key::Home => {
            crate::motions::move_line_start(&mut ed.buffer);
            break_undo_group_in_insert(ed);
            false
        }
        Key::End => {
            crate::motions::move_line_end(&mut ed.buffer);
            break_undo_group_in_insert(ed);
            false
        }
        Key::PageUp => {
            // Vim default: PageUp scrolls a full window up, cursor
            // tracks. Reuse the Ctrl-b scroll helper so behavior
            // matches the normal-mode equivalent.
            let rows = viewport_full_rows(ed, 1) as isize;
            scroll_cursor_rows(ed, -rows);
            return false;
        }
        Key::PageDown => {
            let rows = viewport_full_rows(ed, 1) as isize;
            scroll_cursor_rows(ed, rows);
            return false;
        }
        // F-keys, mouse scroll, copy/cut/paste virtual keys, Null —
        // no insert-mode behaviour.
        _ => false,
    };
    ed.push_buffer_cursor_to_textarea();
    mutated
}

fn finish_insert_session<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    let Some(session) = ed.vim.insert_session.take() else {
        return;
    };
    let lines = buf_lines_to_vec(&ed.buffer);
    // Clamp both slices to their respective bounds — the buffer may have
    // grown (Enter splits rows) or shrunk (Backspace joins rows) during
    // the session, so row_max can overshoot either side.
    let after_end = session.row_max.min(lines.len().saturating_sub(1));
    let before_end = session
        .row_max
        .min(session.before_lines.len().saturating_sub(1));
    let before = if before_end >= session.row_min && session.row_min < session.before_lines.len() {
        session.before_lines[session.row_min..=before_end].join("\n")
    } else {
        String::new()
    };
    let after = if after_end >= session.row_min && session.row_min < lines.len() {
        lines[session.row_min..=after_end].join("\n")
    } else {
        String::new()
    };
    let inserted = extract_inserted(&before, &after);
    if !inserted.is_empty() && session.count > 1 && !ed.vim.replaying {
        use hjkl_buffer::{Edit, Position};
        for _ in 0..session.count - 1 {
            let (row, col) = ed.cursor();
            ed.mutate_edit(Edit::InsertStr {
                at: Position::new(row, col),
                text: inserted.clone(),
            });
        }
    }
    // Helper: replicate `inserted` text across block rows top+1..=bot at `col`,
    // padding short rows to reach `col` first. Returns without touching the
    // cursor — callers position the cursor afterward according to their needs.
    fn replicate_block_text<H: crate::types::Host>(
        ed: &mut Editor<hjkl_buffer::Buffer, H>,
        inserted: &str,
        top: usize,
        bot: usize,
        col: usize,
    ) {
        use hjkl_buffer::{Edit, Position};
        for r in (top + 1)..=bot {
            let line_len = buf_line_chars(&ed.buffer, r);
            if col > line_len {
                let pad: String = std::iter::repeat_n(' ', col - line_len).collect();
                ed.mutate_edit(Edit::InsertStr {
                    at: Position::new(r, line_len),
                    text: pad,
                });
            }
            ed.mutate_edit(Edit::InsertStr {
                at: Position::new(r, col),
                text: inserted.to_string(),
            });
        }
    }

    if let InsertReason::BlockEdge { top, bot, col } = session.reason {
        // `I` / `A` from VisualBlock: replicate text across rows; cursor
        // stays at the block-start column (vim leaves cursor there).
        if !inserted.is_empty() && top < bot && !ed.vim.replaying {
            replicate_block_text(ed, &inserted, top, bot, col);
            buf_set_cursor_rc(&mut ed.buffer, top, col);
            ed.push_buffer_cursor_to_textarea();
        }
        return;
    }
    if let InsertReason::BlockChange { top, bot, col } = session.reason {
        // `c` from VisualBlock: replicate text across rows; cursor advances
        // to `col + ins_chars` (pre-step-back) so the Esc step-back lands
        // on the last typed char (col + ins_chars - 1), matching nvim.
        if !inserted.is_empty() && top < bot && !ed.vim.replaying {
            replicate_block_text(ed, &inserted, top, bot, col);
            let ins_chars = inserted.chars().count();
            let line_len = buf_line_chars(&ed.buffer, top);
            let target_col = (col + ins_chars).min(line_len);
            buf_set_cursor_rc(&mut ed.buffer, top, target_col);
            ed.push_buffer_cursor_to_textarea();
        }
        return;
    }
    if ed.vim.replaying {
        return;
    }
    match session.reason {
        InsertReason::Enter(entry) => {
            ed.vim.last_change = Some(LastChange::InsertAt {
                entry,
                inserted,
                count: session.count,
            });
        }
        InsertReason::Open { above } => {
            ed.vim.last_change = Some(LastChange::OpenLine { above, inserted });
        }
        InsertReason::AfterChange => {
            if let Some(
                LastChange::OpMotion { inserted: ins, .. }
                | LastChange::OpTextObj { inserted: ins, .. }
                | LastChange::LineOp { inserted: ins, .. },
            ) = ed.vim.last_change.as_mut()
            {
                *ins = Some(inserted);
            }
            // Vim `:h '[` / `:h ']`: on change, `[` = start of the
            // changed range (stashed before the cut), `]` = the cursor
            // at Esc time (last inserted char, before the step-back).
            // When nothing was typed cursor still sits at the change
            // start, satisfying vim's "both at start" parity for `c<m><Esc>`.
            if let Some(start) = ed.vim.change_mark_start.take() {
                let end = ed.cursor();
                ed.set_mark('[', start);
                ed.set_mark(']', end);
            }
        }
        InsertReason::DeleteToEol => {
            ed.vim.last_change = Some(LastChange::DeleteToEol {
                inserted: Some(inserted),
            });
        }
        InsertReason::ReplayOnly => {}
        InsertReason::BlockEdge { .. } => unreachable!("handled above"),
        InsertReason::BlockChange { .. } => unreachable!("handled above"),
        InsertReason::Replace => {
            // Record overstrike sessions as DeleteToEol-style — replay
            // re-types each character but doesn't try to restore prior
            // content (vim's R has its own replay path; this is the
            // pragmatic approximation).
            ed.vim.last_change = Some(LastChange::DeleteToEol {
                inserted: Some(inserted),
            });
        }
    }
}

fn begin_insert<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    count: usize,
    reason: InsertReason,
) {
    let record = !matches!(reason, InsertReason::ReplayOnly);
    if record {
        ed.push_undo();
    }
    let reason = if ed.vim.replaying {
        InsertReason::ReplayOnly
    } else {
        reason
    };
    let (row, _) = ed.cursor();
    ed.vim.insert_session = Some(InsertSession {
        count,
        row_min: row,
        row_max: row,
        before_lines: buf_lines_to_vec(&ed.buffer),
        reason,
    });
    ed.vim.mode = Mode::Insert;
}

/// `:set undobreak` semantics for insert-mode motions. When the
/// toggle is on, a non-character keystroke that moves the cursor
/// (arrow keys, Home/End, mouse click) ends the current undo group
/// and starts a new one mid-session. After this, a subsequent `u`
/// in normal mode reverts only the post-break run, leaving the
/// pre-break edits in place — matching vim's behaviour.
///
/// Implementation: snapshot the current buffer onto the undo stack
/// (the new break point) and reset the active `InsertSession`'s
/// `before_lines` so `finish_insert_session`'s diff window only
/// captures the post-break run for `last_change` / dot-repeat.
///
/// During replay we skip the break — replay shouldn't pollute the
/// undo stack with intra-replay snapshots.
pub(crate) fn break_undo_group_in_insert<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
) {
    if !ed.settings.undo_break_on_motion {
        return;
    }
    if ed.vim.replaying {
        return;
    }
    if ed.vim.insert_session.is_none() {
        return;
    }
    ed.push_undo();
    let n = crate::types::Query::line_count(&ed.buffer) as usize;
    let mut lines: Vec<String> = Vec::with_capacity(n);
    for r in 0..n {
        lines.push(crate::types::Query::line(&ed.buffer, r as u32).to_string());
    }
    let row = crate::types::Cursor::cursor(&ed.buffer).line as usize;
    if let Some(ref mut session) = ed.vim.insert_session {
        session.before_lines = lines;
        session.row_min = row;
        session.row_max = row;
    }
}

// ─── Normal / Visual / Operator-pending dispatcher ─────────────────────────

fn step_normal<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    // Consume digits first — except '0' at start of count (that's LineStart).
    if let Key::Char(d @ '0'..='9') = input.key
        && !input.ctrl
        && !input.alt
        && !matches!(
            ed.vim.pending,
            Pending::Replace
                | Pending::Find { .. }
                | Pending::OpFind { .. }
                | Pending::VisualTextObj { .. }
        )
        && (d != '0' || ed.vim.count > 0)
    {
        ed.vim.count = ed.vim.count.saturating_mul(10) + (d as usize - '0' as usize);
        return true;
    }

    // Handle pending two-key sequences first.
    match std::mem::take(&mut ed.vim.pending) {
        Pending::Replace => return handle_replace(ed, input),
        Pending::Find { forward, till } => return handle_find_target(ed, input, forward, till),
        Pending::OpFind {
            op,
            count1,
            forward,
            till,
        } => return handle_op_find_target(ed, input, op, count1, forward, till),
        Pending::G => return handle_after_g(ed, input),
        Pending::OpG { op, count1 } => return handle_op_after_g(ed, input, op, count1),
        Pending::Op { op, count1 } => return handle_after_op(ed, input, op, count1),
        Pending::OpTextObj { op, count1, inner } => {
            return handle_text_object(ed, input, op, count1, inner);
        }
        Pending::VisualTextObj { inner } => {
            return handle_visual_text_obj(ed, input, inner);
        }
        Pending::Z => return handle_after_z(ed, input),
        Pending::SetMark => return handle_set_mark(ed, input),
        Pending::GotoMarkLine => return handle_goto_mark(ed, input, true),
        Pending::GotoMarkChar => return handle_goto_mark(ed, input, false),
        Pending::SelectRegister => return handle_select_register(ed, input),
        Pending::RecordMacroTarget => return handle_record_macro_target(ed, input),
        Pending::PlayMacroTarget { count } => return handle_play_macro_target(ed, input, count),
        Pending::None => {}
    }

    let count = take_count(&mut ed.vim);

    // Common normal / visual keys.
    match input.key {
        Key::Esc => {
            ed.vim.force_normal();
            return true;
        }
        Key::Char('v') if !input.ctrl && ed.vim.mode == Mode::Normal => {
            ed.vim.visual_anchor = ed.cursor();
            ed.vim.mode = Mode::Visual;
            return true;
        }
        Key::Char('V') if !input.ctrl && ed.vim.mode == Mode::Normal => {
            let (row, _) = ed.cursor();
            ed.vim.visual_line_anchor = row;
            ed.vim.mode = Mode::VisualLine;
            return true;
        }
        Key::Char('v') if !input.ctrl && ed.vim.mode == Mode::VisualLine => {
            ed.vim.visual_anchor = ed.cursor();
            ed.vim.mode = Mode::Visual;
            return true;
        }
        Key::Char('V') if !input.ctrl && ed.vim.mode == Mode::Visual => {
            let (row, _) = ed.cursor();
            ed.vim.visual_line_anchor = row;
            ed.vim.mode = Mode::VisualLine;
            return true;
        }
        Key::Char('v') if input.ctrl && ed.vim.mode == Mode::Normal => {
            let cur = ed.cursor();
            ed.vim.block_anchor = cur;
            ed.vim.block_vcol = cur.1;
            ed.vim.mode = Mode::VisualBlock;
            return true;
        }
        Key::Char('v') if input.ctrl && ed.vim.mode == Mode::VisualBlock => {
            // Second Ctrl-v exits block mode back to Normal.
            ed.vim.mode = Mode::Normal;
            return true;
        }
        // `o` in visual modes — swap anchor and cursor so the user
        // can extend the other end of the selection.
        Key::Char('o') if !input.ctrl => match ed.vim.mode {
            Mode::Visual => {
                let cur = ed.cursor();
                let anchor = ed.vim.visual_anchor;
                ed.vim.visual_anchor = cur;
                ed.jump_cursor(anchor.0, anchor.1);
                return true;
            }
            Mode::VisualLine => {
                let cur_row = ed.cursor().0;
                let anchor_row = ed.vim.visual_line_anchor;
                ed.vim.visual_line_anchor = cur_row;
                ed.jump_cursor(anchor_row, 0);
                return true;
            }
            Mode::VisualBlock => {
                let cur = ed.cursor();
                let anchor = ed.vim.block_anchor;
                ed.vim.block_anchor = cur;
                ed.vim.block_vcol = anchor.1;
                ed.jump_cursor(anchor.0, anchor.1);
                return true;
            }
            _ => {}
        },
        _ => {}
    }

    // Visual mode: operators act on the current selection.
    if ed.vim.is_visual()
        && let Some(op) = visual_operator(&input)
    {
        apply_visual_operator(ed, op);
        return true;
    }

    // VisualBlock: extra commands beyond the standard y/d/c/x — `r`
    // replaces the block with a single char, `I` / `A` enter insert
    // mode at the block's left / right edge and repeat on every row.
    if ed.vim.mode == Mode::VisualBlock && !input.ctrl {
        match input.key {
            Key::Char('r') => {
                ed.vim.pending = Pending::Replace;
                return true;
            }
            Key::Char('I') => {
                let (top, bot, left, _right) = block_bounds(ed);
                ed.jump_cursor(top, left);
                ed.vim.mode = Mode::Normal;
                begin_insert(
                    ed,
                    1,
                    InsertReason::BlockEdge {
                        top,
                        bot,
                        col: left,
                    },
                );
                return true;
            }
            Key::Char('A') => {
                let (top, bot, _left, right) = block_bounds(ed);
                let line_len = buf_line_chars(&ed.buffer, top);
                let col = (right + 1).min(line_len);
                ed.jump_cursor(top, col);
                ed.vim.mode = Mode::Normal;
                begin_insert(ed, 1, InsertReason::BlockEdge { top, bot, col });
                return true;
            }
            _ => {}
        }
    }

    // Visual mode: `i` / `a` start a text-object extension.
    if matches!(ed.vim.mode, Mode::Visual | Mode::VisualLine)
        && !input.ctrl
        && matches!(input.key, Key::Char('i') | Key::Char('a'))
    {
        let inner = matches!(input.key, Key::Char('i'));
        ed.vim.pending = Pending::VisualTextObj { inner };
        return true;
    }

    // Ctrl-prefixed scrolling + misc. Vim semantics: Ctrl-d / Ctrl-u
    // move the cursor by half a window, Ctrl-f / Ctrl-b by a full
    // window. Viewport follows the cursor. Cursor lands on the first
    // non-blank of the target row (matches vim).
    if input.ctrl
        && let Key::Char(c) = input.key
    {
        match c {
            'd' => {
                scroll_cursor_rows(ed, viewport_half_rows(ed, count) as isize);
                return true;
            }
            'u' => {
                scroll_cursor_rows(ed, -(viewport_half_rows(ed, count) as isize));
                return true;
            }
            'f' => {
                scroll_cursor_rows(ed, viewport_full_rows(ed, count) as isize);
                return true;
            }
            'b' => {
                scroll_cursor_rows(ed, -(viewport_full_rows(ed, count) as isize));
                return true;
            }
            'r' => {
                do_redo(ed);
                return true;
            }
            'a' if ed.vim.mode == Mode::Normal => {
                adjust_number(ed, count.max(1) as i64);
                return true;
            }
            'x' if ed.vim.mode == Mode::Normal => {
                adjust_number(ed, -(count.max(1) as i64));
                return true;
            }
            'o' if ed.vim.mode == Mode::Normal => {
                for _ in 0..count.max(1) {
                    jump_back(ed);
                }
                return true;
            }
            'i' if ed.vim.mode == Mode::Normal => {
                for _ in 0..count.max(1) {
                    jump_forward(ed);
                }
                return true;
            }
            _ => {}
        }
    }

    // `Tab` in normal mode is also `Ctrl-i` — vim aliases them.
    if !input.ctrl && input.key == Key::Tab && ed.vim.mode == Mode::Normal {
        for _ in 0..count.max(1) {
            jump_forward(ed);
        }
        return true;
    }

    // Motion-only commands.
    if let Some(motion) = parse_motion(&input) {
        execute_motion(ed, motion.clone(), count);
        // Block mode: maintain the virtual column across j/k clamps.
        if ed.vim.mode == Mode::VisualBlock {
            update_block_vcol(ed, &motion);
        }
        if let Motion::Find { ch, forward, till } = motion {
            ed.vim.last_find = Some((ch, forward, till));
        }
        return true;
    }

    // Mode transitions + pure normal-mode commands (not applicable in visual).
    if ed.vim.mode == Mode::Normal && handle_normal_only(ed, &input, count) {
        return true;
    }

    // Operator triggers in normal mode.
    if ed.vim.mode == Mode::Normal
        && let Key::Char(op_ch) = input.key
        && !input.ctrl
        && let Some(op) = char_to_operator(op_ch)
    {
        ed.vim.pending = Pending::Op { op, count1: count };
        return true;
    }

    // `f`/`F`/`t`/`T` entry.
    if ed.vim.mode == Mode::Normal
        && let Some((forward, till)) = find_entry(&input)
    {
        ed.vim.count = count;
        ed.vim.pending = Pending::Find { forward, till };
        return true;
    }

    // `g` prefix.
    if !input.ctrl && input.key == Key::Char('g') && ed.vim.mode == Mode::Normal {
        ed.vim.count = count;
        ed.vim.pending = Pending::G;
        return true;
    }

    // `z` prefix (zz / zt / zb — cursor-relative viewport scrolls).
    if !input.ctrl
        && input.key == Key::Char('z')
        && matches!(
            ed.vim.mode,
            Mode::Normal | Mode::Visual | Mode::VisualLine | Mode::VisualBlock
        )
    {
        ed.vim.pending = Pending::Z;
        return true;
    }

    // Mark set / jump entries. `m` arms the set-mark pending state;
    // `'` and `` ` `` arm the goto states (linewise vs charwise). The
    // mark letter is consumed on the next keystroke.
    // In visual modes, `` ` `` also arms GotoMarkChar so the cursor can
    // extend the selection to a mark position (e.g. `` `[v`] `` idiom).
    if !input.ctrl
        && matches!(
            ed.vim.mode,
            Mode::Normal | Mode::Visual | Mode::VisualLine | Mode::VisualBlock
        )
        && input.key == Key::Char('`')
    {
        ed.vim.pending = Pending::GotoMarkChar;
        return true;
    }
    if !input.ctrl && ed.vim.mode == Mode::Normal {
        match input.key {
            Key::Char('m') => {
                ed.vim.pending = Pending::SetMark;
                return true;
            }
            Key::Char('\'') => {
                ed.vim.pending = Pending::GotoMarkLine;
                return true;
            }
            Key::Char('`') => {
                // Already handled above for all visual modes + normal.
                ed.vim.pending = Pending::GotoMarkChar;
                return true;
            }
            Key::Char('"') => {
                // Open the register-selector chord. The next char picks
                // a register that the next y/d/c/p uses.
                ed.vim.pending = Pending::SelectRegister;
                return true;
            }
            Key::Char('@') => {
                // Open the macro-play chord. Next char names the
                // register; `@@` re-plays the last-played macro.
                // Stash any count so the chord can multiply replays.
                ed.vim.pending = Pending::PlayMacroTarget { count };
                return true;
            }
            Key::Char('q') if ed.vim.recording_macro.is_none() => {
                // Open the macro-record chord. The bare-q stop is
                // handled at the top of `step` so it's not consumed
                // as another open. Recording-in-progress falls through
                // here and is treated as a no-op (matches vim).
                ed.vim.pending = Pending::RecordMacroTarget;
                return true;
            }
            _ => {}
        }
    }

    // Unknown key — swallow so it doesn't bubble into the TUI layer.
    true
}

fn handle_set_mark<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    if let Key::Char(c) = input.key
        && (c.is_ascii_lowercase() || c.is_ascii_uppercase())
    {
        // 0.0.36: lowercase + uppercase marks share the unified
        // `Editor::marks` map. Uppercase entries survive
        // `set_content` so they persist across tab swaps within the
        // same Editor (the map lives on the Editor, not the buffer).
        let pos = ed.cursor();
        ed.set_mark(c, pos);
    }
    true
}

/// `"reg` — store the register selector for the next y / d / c / p.
/// Accepts `a`–`z`, `A`–`Z`, `0`–`9`, `"`, and the system-clipboard
/// selectors `+` / `*`. Anything else cancels silently.
fn handle_select_register<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    if let Key::Char(c) = input.key
        && (c.is_ascii_alphanumeric() || matches!(c, '"' | '+' | '*' | '_'))
    {
        ed.vim.pending_register = Some(c);
    }
    true
}

/// `q{reg}` — start recording into `reg`. The recording session
/// captures every consumed `Input` until a bare `q` ends it (handled
/// inline at the top of `step`). Capital letters append to the
/// matching lowercase register, mirroring named-register semantics.
fn handle_record_macro_target<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    if let Key::Char(c) = input.key
        && (c.is_ascii_alphabetic() || c.is_ascii_digit())
    {
        ed.vim.recording_macro = Some(c);
        // For `qA` (capital), seed the buffer with the existing
        // lowercase recording so the new keystrokes append.
        if c.is_ascii_uppercase() {
            let lower = c.to_ascii_lowercase();
            // Seed `recording_keys` with the existing register's text
            // decoded back to inputs, so capital-register append
            // continues from where the previous recording left off.
            let text = ed
                .registers()
                .read(lower)
                .map(|s| s.text.clone())
                .unwrap_or_default();
            ed.vim.recording_keys = crate::input::decode_macro(&text);
        } else {
            ed.vim.recording_keys.clear();
        }
    }
    true
}

/// `@{reg}` — replay the macro recorded under `reg`. `@@` re-plays
/// the last-played macro. The replay re-feeds each captured `Input`
/// through `step`, with `replaying_macro` flagged so the recorder
/// (if active) doesn't double-capture. Honours the count prefix:
/// `3@a` plays the macro three times.
fn handle_play_macro_target<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    count: usize,
) -> bool {
    let reg = match input.key {
        Key::Char('@') => ed.vim.last_macro,
        Key::Char(c) if c.is_ascii_alphabetic() || c.is_ascii_digit() => {
            Some(c.to_ascii_lowercase())
        }
        _ => None,
    };
    let Some(reg) = reg else {
        return true;
    };
    // Read the macro text from the named register and decode back to
    // an Input stream. Empty / unset registers replay nothing.
    let text = match ed.registers().read(reg) {
        Some(slot) if !slot.text.is_empty() => slot.text.clone(),
        _ => return true,
    };
    let keys = crate::input::decode_macro(&text);
    ed.vim.last_macro = Some(reg);
    let times = count.max(1);
    let was_replaying = ed.vim.replaying_macro;
    ed.vim.replaying_macro = true;
    for _ in 0..times {
        for k in keys.iter().copied() {
            step(ed, k);
        }
    }
    ed.vim.replaying_macro = was_replaying;
    true
}

fn handle_goto_mark<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    linewise: bool,
) -> bool {
    let Key::Char(c) = input.key else {
        return true;
    };
    // Resolve the mark target. Lowercase letters look up the user
    // marks set via `m{a..z}`; the special chars below come from
    // automatic state vim maintains:
    //   `'` / `` ` `` — position before the most recent big jump
    //                  (peeks `jump_back` without popping).
    //   `.`           — the last edit's position.
    let target = match c {
        'a'..='z' | 'A'..='Z' => ed.mark(c),
        '\'' | '`' => ed.vim.jump_back.last().copied(),
        '.' => ed.vim.last_edit_pos,
        // Special auto-marks: `[` / `]` — last yank / change / paste bounds
        // (vim `:h '[` / `:h ']`). Stored by the operator and paste paths.
        // `<` / `>` — last visual selection start / end (vim `:h '<` /
        // `:h '>`). Stored by the visual-exit hook (0.5.3).
        '[' | ']' | '<' | '>' => ed.mark(c),
        _ => None,
    };
    let Some((row, col)) = target else {
        return true;
    };
    let pre = ed.cursor();
    let (r, c_clamped) = clamp_pos(ed, (row, col));
    if linewise {
        buf_set_cursor_rc(&mut ed.buffer, r, 0);
        ed.push_buffer_cursor_to_textarea();
        move_first_non_whitespace(ed);
    } else {
        buf_set_cursor_rc(&mut ed.buffer, r, c_clamped);
        ed.push_buffer_cursor_to_textarea();
    }
    if ed.cursor() != pre {
        push_jump(ed, pre);
    }
    ed.sticky_col = Some(ed.cursor().1);
    true
}

fn take_count(vim: &mut VimState) -> usize {
    if vim.count > 0 {
        let n = vim.count;
        vim.count = 0;
        n
    } else {
        1
    }
}

fn char_to_operator(c: char) -> Option<Operator> {
    match c {
        'd' => Some(Operator::Delete),
        'c' => Some(Operator::Change),
        'y' => Some(Operator::Yank),
        '>' => Some(Operator::Indent),
        '<' => Some(Operator::Outdent),
        _ => None,
    }
}

fn visual_operator(input: &Input) -> Option<Operator> {
    if input.ctrl {
        return None;
    }
    match input.key {
        Key::Char('y') => Some(Operator::Yank),
        Key::Char('d') | Key::Char('x') => Some(Operator::Delete),
        Key::Char('c') | Key::Char('s') => Some(Operator::Change),
        // Case operators — shift forms apply to the active selection.
        Key::Char('U') => Some(Operator::Uppercase),
        Key::Char('u') => Some(Operator::Lowercase),
        Key::Char('~') => Some(Operator::ToggleCase),
        // Indent operators on selection.
        Key::Char('>') => Some(Operator::Indent),
        Key::Char('<') => Some(Operator::Outdent),
        _ => None,
    }
}

fn find_entry(input: &Input) -> Option<(bool, bool)> {
    if input.ctrl {
        return None;
    }
    match input.key {
        Key::Char('f') => Some((true, false)),
        Key::Char('F') => Some((false, false)),
        Key::Char('t') => Some((true, true)),
        Key::Char('T') => Some((false, true)),
        _ => None,
    }
}

// ─── Jumplist (Ctrl-o / Ctrl-i) ────────────────────────────────────────────

/// Max jumplist depth. Matches vim default.
const JUMPLIST_MAX: usize = 100;

/// Record a pre-jump cursor position. Called *before* a big-jump
/// motion runs (`gg`/`G`, `%`, `*`/`#`, `n`/`N`, `H`/`M`/`L`, `/`?
/// commit, `:{nr}`). Making a new jump while the forward stack had
/// entries trims them — branching off the history clears the "redo".
fn push_jump<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>, from: (usize, usize)) {
    ed.vim.jump_back.push(from);
    if ed.vim.jump_back.len() > JUMPLIST_MAX {
        ed.vim.jump_back.remove(0);
    }
    ed.vim.jump_fwd.clear();
}

/// `Ctrl-o` — jump back to the most recent pre-jump position. Saves
/// the current cursor onto the forward stack so `Ctrl-i` can return.
fn jump_back<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    let Some(target) = ed.vim.jump_back.pop() else {
        return;
    };
    let cur = ed.cursor();
    ed.vim.jump_fwd.push(cur);
    let (r, c) = clamp_pos(ed, target);
    ed.jump_cursor(r, c);
    ed.sticky_col = Some(c);
}

/// `Ctrl-i` / `Tab` — redo the last `Ctrl-o`. Saves the current cursor
/// onto the back stack.
fn jump_forward<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    let Some(target) = ed.vim.jump_fwd.pop() else {
        return;
    };
    let cur = ed.cursor();
    ed.vim.jump_back.push(cur);
    if ed.vim.jump_back.len() > JUMPLIST_MAX {
        ed.vim.jump_back.remove(0);
    }
    let (r, c) = clamp_pos(ed, target);
    ed.jump_cursor(r, c);
    ed.sticky_col = Some(c);
}

/// Clamp a stored `(row, col)` to the live buffer in case edits
/// shrunk the document between push and pop.
fn clamp_pos<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    pos: (usize, usize),
) -> (usize, usize) {
    let last_row = buf_row_count(&ed.buffer).saturating_sub(1);
    let r = pos.0.min(last_row);
    let line_len = buf_line_chars(&ed.buffer, r);
    let c = pos.1.min(line_len.saturating_sub(1));
    (r, c)
}

/// True for motions that vim treats as jumps (pushed onto the jumplist).
fn is_big_jump(motion: &Motion) -> bool {
    matches!(
        motion,
        Motion::FileTop
            | Motion::FileBottom
            | Motion::MatchBracket
            | Motion::WordAtCursor { .. }
            | Motion::SearchNext { .. }
            | Motion::ViewportTop
            | Motion::ViewportMiddle
            | Motion::ViewportBottom
    )
}

// ─── Scroll helpers (Ctrl-d / Ctrl-u / Ctrl-f / Ctrl-b) ────────────────────

/// Half-viewport row count, with a floor of 1 so tiny / un-rendered
/// viewports still step by a single row. `count` multiplies.
fn viewport_half_rows<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    count: usize,
) -> usize {
    let h = ed.viewport_height_value() as usize;
    (h / 2).max(1).saturating_mul(count.max(1))
}

/// Full-viewport row count. Vim conventionally keeps 2 lines of overlap
/// between successive `Ctrl-f` pages; we approximate with `h - 2`.
fn viewport_full_rows<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    count: usize,
) -> usize {
    let h = ed.viewport_height_value() as usize;
    h.saturating_sub(2).max(1).saturating_mul(count.max(1))
}

/// Move the cursor by `delta` rows (positive = down, negative = up),
/// clamp to the document, then land at the first non-blank on the new
/// row. The textarea viewport auto-scrolls to keep the cursor visible
/// when the cursor pushes off-screen.
fn scroll_cursor_rows<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    delta: isize,
) {
    if delta == 0 {
        return;
    }
    ed.sync_buffer_content_from_textarea();
    let (row, _) = ed.cursor();
    let last_row = buf_row_count(&ed.buffer).saturating_sub(1);
    let target = (row as isize + delta).max(0).min(last_row as isize) as usize;
    buf_set_cursor_rc(&mut ed.buffer, target, 0);
    crate::motions::move_first_non_blank(&mut ed.buffer);
    ed.push_buffer_cursor_to_textarea();
    ed.sticky_col = Some(buf_cursor_pos(&ed.buffer).col);
}

// ─── Motion parsing ────────────────────────────────────────────────────────

fn parse_motion(input: &Input) -> Option<Motion> {
    if input.ctrl {
        return None;
    }
    match input.key {
        Key::Char('h') | Key::Backspace | Key::Left => Some(Motion::Left),
        Key::Char('l') | Key::Right => Some(Motion::Right),
        Key::Char('j') | Key::Down | Key::Enter => Some(Motion::Down),
        Key::Char('k') | Key::Up => Some(Motion::Up),
        Key::Char('w') => Some(Motion::WordFwd),
        Key::Char('W') => Some(Motion::BigWordFwd),
        Key::Char('b') => Some(Motion::WordBack),
        Key::Char('B') => Some(Motion::BigWordBack),
        Key::Char('e') => Some(Motion::WordEnd),
        Key::Char('E') => Some(Motion::BigWordEnd),
        Key::Char('0') | Key::Home => Some(Motion::LineStart),
        Key::Char('^') => Some(Motion::FirstNonBlank),
        Key::Char('$') | Key::End => Some(Motion::LineEnd),
        Key::Char('G') => Some(Motion::FileBottom),
        Key::Char('%') => Some(Motion::MatchBracket),
        Key::Char(';') => Some(Motion::FindRepeat { reverse: false }),
        Key::Char(',') => Some(Motion::FindRepeat { reverse: true }),
        Key::Char('*') => Some(Motion::WordAtCursor {
            forward: true,
            whole_word: true,
        }),
        Key::Char('#') => Some(Motion::WordAtCursor {
            forward: false,
            whole_word: true,
        }),
        Key::Char('n') => Some(Motion::SearchNext { reverse: false }),
        Key::Char('N') => Some(Motion::SearchNext { reverse: true }),
        Key::Char('H') => Some(Motion::ViewportTop),
        Key::Char('M') => Some(Motion::ViewportMiddle),
        Key::Char('L') => Some(Motion::ViewportBottom),
        Key::Char('{') => Some(Motion::ParagraphPrev),
        Key::Char('}') => Some(Motion::ParagraphNext),
        Key::Char('(') => Some(Motion::SentencePrev),
        Key::Char(')') => Some(Motion::SentenceNext),
        _ => None,
    }
}

// ─── Motion execution ──────────────────────────────────────────────────────

pub(crate) fn execute_motion<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    motion: Motion,
    count: usize,
) {
    let count = count.max(1);
    // FindRepeat needs the stored direction.
    let motion = match motion {
        Motion::FindRepeat { reverse } => match ed.vim.last_find {
            Some((ch, forward, till)) => Motion::Find {
                ch,
                forward: if reverse { !forward } else { forward },
                till,
            },
            None => return,
        },
        other => other,
    };
    let pre_pos = ed.cursor();
    let pre_col = pre_pos.1;
    apply_motion_cursor(ed, &motion, count);
    let post_pos = ed.cursor();
    if is_big_jump(&motion) && pre_pos != post_pos {
        push_jump(ed, pre_pos);
    }
    apply_sticky_col(ed, &motion, pre_col);
    // Phase 7b: keep the migration buffer's cursor + viewport in
    // lockstep with the textarea after every motion. Once 7c lands
    // (motions ported onto the buffer's API), this flips: the
    // buffer becomes authoritative and the textarea mirrors it.
    ed.sync_buffer_from_textarea();
}

/// Restore the cursor to the sticky column after vertical motions and
/// sync the sticky column to the current column after horizontal ones.
/// `pre_col` is the cursor column captured *before* the motion — used
/// to bootstrap the sticky value on the very first motion.
fn apply_sticky_col<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    motion: &Motion,
    pre_col: usize,
) {
    if is_vertical_motion(motion) {
        let want = ed.sticky_col.unwrap_or(pre_col);
        // Record the desired column so the next vertical motion sees
        // it even if we currently clamped to a shorter row.
        ed.sticky_col = Some(want);
        let (row, _) = ed.cursor();
        let line_len = buf_line_chars(&ed.buffer, row);
        // Clamp to the last char on non-empty lines (vim normal-mode
        // never parks the cursor one past end of line). Empty lines
        // collapse to col 0.
        let max_col = line_len.saturating_sub(1);
        let target = want.min(max_col);
        ed.jump_cursor(row, target);
    } else {
        // Horizontal motion or non-motion: sticky column tracks the
        // new cursor column so the *next* vertical motion aims there.
        ed.sticky_col = Some(ed.cursor().1);
    }
}

fn is_vertical_motion(motion: &Motion) -> bool {
    // Only j / k preserve the sticky column. Everything else (search,
    // gg / G, word jumps, etc.) lands at the match's own column so the
    // sticky value should sync to the new cursor column.
    matches!(
        motion,
        Motion::Up | Motion::Down | Motion::ScreenUp | Motion::ScreenDown
    )
}

fn apply_motion_cursor<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    motion: &Motion,
    count: usize,
) {
    apply_motion_cursor_ctx(ed, motion, count, false)
}

fn apply_motion_cursor_ctx<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    motion: &Motion,
    count: usize,
    as_operator: bool,
) {
    match motion {
        Motion::Left => {
            // `h` — Buffer clamps at col 0 (no wrap), matching vim.
            crate::motions::move_left(&mut ed.buffer, count);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::Right => {
            // `l` — operator-motion context (`dl`/`cl`/`yl`) is allowed
            // one past the last char so the range includes it; cursor
            // context clamps at the last char.
            if as_operator {
                crate::motions::move_right_to_end(&mut ed.buffer, count);
            } else {
                crate::motions::move_right_in_line(&mut ed.buffer, count);
            }
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::Up => {
            // Final col is set by `apply_sticky_col` below — push the
            // post-move row to the textarea and let sticky tracking
            // finish the work.
            let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
            crate::motions::move_up(&mut ed.buffer, &folds, count, &mut ed.sticky_col);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::Down => {
            let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
            crate::motions::move_down(&mut ed.buffer, &folds, count, &mut ed.sticky_col);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::ScreenUp => {
            let v = *ed.host.viewport();
            let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
            crate::motions::move_screen_up(&mut ed.buffer, &folds, &v, count, &mut ed.sticky_col);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::ScreenDown => {
            let v = *ed.host.viewport();
            let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
            crate::motions::move_screen_down(&mut ed.buffer, &folds, &v, count, &mut ed.sticky_col);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::WordFwd => {
            crate::motions::move_word_fwd(&mut ed.buffer, false, count, &ed.settings.iskeyword);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::WordBack => {
            crate::motions::move_word_back(&mut ed.buffer, false, count, &ed.settings.iskeyword);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::WordEnd => {
            crate::motions::move_word_end(&mut ed.buffer, false, count, &ed.settings.iskeyword);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::BigWordFwd => {
            crate::motions::move_word_fwd(&mut ed.buffer, true, count, &ed.settings.iskeyword);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::BigWordBack => {
            crate::motions::move_word_back(&mut ed.buffer, true, count, &ed.settings.iskeyword);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::BigWordEnd => {
            crate::motions::move_word_end(&mut ed.buffer, true, count, &ed.settings.iskeyword);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::WordEndBack => {
            crate::motions::move_word_end_back(
                &mut ed.buffer,
                false,
                count,
                &ed.settings.iskeyword,
            );
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::BigWordEndBack => {
            crate::motions::move_word_end_back(&mut ed.buffer, true, count, &ed.settings.iskeyword);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::LineStart => {
            crate::motions::move_line_start(&mut ed.buffer);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::FirstNonBlank => {
            crate::motions::move_first_non_blank(&mut ed.buffer);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::LineEnd => {
            // Vim normal-mode `$` lands on the last char, not one past it.
            crate::motions::move_line_end(&mut ed.buffer);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::FileTop => {
            // `count gg` jumps to line `count` (first non-blank);
            // bare `gg` lands at the top.
            if count > 1 {
                crate::motions::move_bottom(&mut ed.buffer, count);
            } else {
                crate::motions::move_top(&mut ed.buffer);
            }
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::FileBottom => {
            // `count G` jumps to line `count`; bare `G` lands at
            // the buffer bottom (`Buffer::move_bottom(0)`).
            if count > 1 {
                crate::motions::move_bottom(&mut ed.buffer, count);
            } else {
                crate::motions::move_bottom(&mut ed.buffer, 0);
            }
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::Find { ch, forward, till } => {
            for _ in 0..count {
                if !find_char_on_line(ed, *ch, *forward, *till) {
                    break;
                }
            }
        }
        Motion::FindRepeat { .. } => {} // already resolved upstream
        Motion::MatchBracket => {
            let _ = matching_bracket(ed);
        }
        Motion::WordAtCursor {
            forward,
            whole_word,
        } => {
            word_at_cursor_search(ed, *forward, *whole_word, count);
        }
        Motion::SearchNext { reverse } => {
            // Re-push the last query so the buffer's search state is
            // correct even if the host happened to clear it (e.g. while
            // a Visual mode draw was in progress).
            if let Some(pattern) = ed.vim.last_search.clone() {
                push_search_pattern(ed, &pattern);
            }
            if ed.search_state().pattern.is_none() {
                return;
            }
            // `n` repeats the last search in its committed direction;
            // `N` inverts. So a `?` search makes `n` walk backward and
            // `N` walk forward.
            let forward = ed.vim.last_search_forward != *reverse;
            for _ in 0..count.max(1) {
                if forward {
                    ed.search_advance_forward(true);
                } else {
                    ed.search_advance_backward(true);
                }
            }
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::ViewportTop => {
            let v = *ed.host().viewport();
            crate::motions::move_viewport_top(&mut ed.buffer, &v, count.saturating_sub(1));
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::ViewportMiddle => {
            let v = *ed.host().viewport();
            crate::motions::move_viewport_middle(&mut ed.buffer, &v);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::ViewportBottom => {
            let v = *ed.host().viewport();
            crate::motions::move_viewport_bottom(&mut ed.buffer, &v, count.saturating_sub(1));
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::LastNonBlank => {
            crate::motions::move_last_non_blank(&mut ed.buffer);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::LineMiddle => {
            let row = ed.cursor().0;
            let line_chars = buf_line_chars(&ed.buffer, row);
            // Vim's `gM`: column = floor(chars / 2). Empty / single-char
            // lines stay at col 0.
            let target = line_chars / 2;
            ed.jump_cursor(row, target);
        }
        Motion::ParagraphPrev => {
            crate::motions::move_paragraph_prev(&mut ed.buffer, count);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::ParagraphNext => {
            crate::motions::move_paragraph_next(&mut ed.buffer, count);
            ed.push_buffer_cursor_to_textarea();
        }
        Motion::SentencePrev => {
            for _ in 0..count.max(1) {
                if let Some((row, col)) = sentence_boundary(ed, false) {
                    ed.jump_cursor(row, col);
                }
            }
        }
        Motion::SentenceNext => {
            for _ in 0..count.max(1) {
                if let Some((row, col)) = sentence_boundary(ed, true) {
                    ed.jump_cursor(row, col);
                }
            }
        }
    }
}

fn move_first_non_whitespace<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    // Some call sites invoke this right after `dd` / `<<` / `>>` etc
    // mutates the textarea content, so the migration buffer hasn't
    // seen the new lines OR new cursor yet. Mirror the full content
    // across before delegating, then push the result back so the
    // textarea reflects the resolved column too.
    ed.sync_buffer_content_from_textarea();
    crate::motions::move_first_non_blank(&mut ed.buffer);
    ed.push_buffer_cursor_to_textarea();
}

fn find_char_on_line<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    ch: char,
    forward: bool,
    till: bool,
) -> bool {
    let moved = crate::motions::find_char_on_line(&mut ed.buffer, ch, forward, till);
    if moved {
        ed.push_buffer_cursor_to_textarea();
    }
    moved
}

fn matching_bracket<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) -> bool {
    let moved = crate::motions::match_bracket(&mut ed.buffer);
    if moved {
        ed.push_buffer_cursor_to_textarea();
    }
    moved
}

fn word_at_cursor_search<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    forward: bool,
    whole_word: bool,
    count: usize,
) {
    let (row, col) = ed.cursor();
    let line: String = buf_line(&ed.buffer, row).unwrap_or("").to_string();
    let chars: Vec<char> = line.chars().collect();
    if chars.is_empty() {
        return;
    }
    // Expand around cursor to a word boundary.
    let spec = ed.settings().iskeyword.clone();
    let is_word = |c: char| is_keyword_char(c, &spec);
    let mut start = col.min(chars.len().saturating_sub(1));
    while start > 0 && is_word(chars[start - 1]) {
        start -= 1;
    }
    let mut end = start;
    while end < chars.len() && is_word(chars[end]) {
        end += 1;
    }
    if end <= start {
        return;
    }
    let word: String = chars[start..end].iter().collect();
    let escaped = regex_escape(&word);
    let pattern = if whole_word {
        format!(r"\b{escaped}\b")
    } else {
        escaped
    };
    push_search_pattern(ed, &pattern);
    if ed.search_state().pattern.is_none() {
        return;
    }
    // Remember the query so `n` / `N` keep working after the jump.
    ed.vim.last_search = Some(pattern);
    ed.vim.last_search_forward = forward;
    for _ in 0..count.max(1) {
        if forward {
            ed.search_advance_forward(true);
        } else {
            ed.search_advance_backward(true);
        }
    }
    ed.push_buffer_cursor_to_textarea();
}

fn regex_escape(s: &str) -> String {
    let mut out = String::with_capacity(s.len());
    for c in s.chars() {
        if matches!(
            c,
            '.' | '+' | '*' | '?' | '(' | ')' | '[' | ']' | '{' | '}' | '|' | '^' | '$' | '\\'
        ) {
            out.push('\\');
        }
        out.push(c);
    }
    out
}

// ─── Operator application ──────────────────────────────────────────────────

/// Public(crate) entry: apply operator over the motion identified by a raw
/// char key. Called by `Editor::apply_op_motion` (the public controller API)
/// so the hjkl-vim pending-state reducer can dispatch `ApplyOpMotion` without
/// re-entering the FSM.
///
/// Applies the same vim quirks as `handle_after_op`:
/// - `cw` / `cW` → `ce` / `cE`
/// - `FindRepeat` → resolves against `last_find`
/// - Updates `last_find` and `last_change` per existing conventions.
///
/// No-op when `motion_key` does not produce a known motion.
pub(crate) fn apply_op_motion_key<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    motion_key: char,
    total_count: usize,
) {
    let input = Input {
        key: Key::Char(motion_key),
        ctrl: false,
        alt: false,
        shift: false,
    };
    let Some(motion) = parse_motion(&input) else {
        return;
    };
    let motion = match motion {
        Motion::FindRepeat { reverse } => match ed.vim.last_find {
            Some((ch, forward, till)) => Motion::Find {
                ch,
                forward: if reverse { !forward } else { forward },
                till,
            },
            None => return,
        },
        // Vim quirk: `cw` / `cW` → `ce` / `cE`.
        Motion::WordFwd if op == Operator::Change => Motion::WordEnd,
        Motion::BigWordFwd if op == Operator::Change => Motion::BigWordEnd,
        m => m,
    };
    apply_op_with_motion(ed, op, &motion, total_count);
    if let Motion::Find { ch, forward, till } = &motion {
        ed.vim.last_find = Some((*ch, *forward, *till));
    }
    if !ed.vim.replaying && op_is_change(op) {
        ed.vim.last_change = Some(LastChange::OpMotion {
            op,
            motion,
            count: total_count,
            inserted: None,
        });
    }
}

/// Public(crate) entry: apply doubled-letter line op (`dd`/`yy`/`cc`/`>>`/`<<`).
/// Called by `Editor::apply_op_double` (the public controller API).
pub(crate) fn apply_op_double<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    total_count: usize,
) {
    execute_line_op(ed, op, total_count);
    if !ed.vim.replaying {
        ed.vim.last_change = Some(LastChange::LineOp {
            op,
            count: total_count,
            inserted: None,
        });
    }
}

/// Public(crate) entry: set `Pending::OpTextObj { op, count1, inner }`.
/// Called by `Editor::enter_op_text_obj` (the public controller API).
pub(crate) fn enter_op_text_obj<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    count1: usize,
    inner: bool,
) {
    ed.vim.pending = Pending::OpTextObj { op, count1, inner };
}

/// Public(crate) entry: set `Pending::OpG { op, count1 }`.
/// Called by `Editor::enter_op_g` (the public controller API).
pub(crate) fn enter_op_g<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    count1: usize,
) {
    ed.vim.pending = Pending::OpG { op, count1 };
}

/// Public(crate) entry: set `Pending::OpFind { op, count1, forward, till }`.
/// Called by `Editor::enter_op_find` (the public controller API).
pub(crate) fn enter_op_find<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    count1: usize,
    forward: bool,
    till: bool,
) {
    ed.vim.pending = Pending::OpFind {
        op,
        count1,
        forward,
        till,
    };
}

fn handle_after_op<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    op: Operator,
    count1: usize,
) -> bool {
    // Inner count after operator (e.g. d3w): accumulate in state.count.
    if let Key::Char(d @ '0'..='9') = input.key
        && !input.ctrl
        && (d != '0' || ed.vim.count > 0)
    {
        ed.vim.count = ed.vim.count.saturating_mul(10) + (d as usize - '0' as usize);
        ed.vim.pending = Pending::Op { op, count1 };
        return true;
    }

    // Esc cancels.
    if input.key == Key::Esc {
        ed.vim.count = 0;
        return true;
    }

    // Same-letter: dd / cc / yy / gUU / guu / g~~ / >> / <<. Fold has
    // no doubled form in vim — `zfzf` is two `zf` chords, not a line
    // op — so skip the branch entirely.
    let double_ch = match op {
        Operator::Delete => Some('d'),
        Operator::Change => Some('c'),
        Operator::Yank => Some('y'),
        Operator::Indent => Some('>'),
        Operator::Outdent => Some('<'),
        Operator::Uppercase => Some('U'),
        Operator::Lowercase => Some('u'),
        Operator::ToggleCase => Some('~'),
        Operator::Fold => None,
        // `gqq` reflows the current line — vim's doubled form for the
        // reflow operator is the second `q` after `gq`.
        Operator::Reflow => Some('q'),
    };
    if let Key::Char(c) = input.key
        && !input.ctrl
        && Some(c) == double_ch
    {
        let count2 = take_count(&mut ed.vim);
        let total = count1.max(1) * count2.max(1);
        execute_line_op(ed, op, total);
        if !ed.vim.replaying {
            ed.vim.last_change = Some(LastChange::LineOp {
                op,
                count: total,
                inserted: None,
            });
        }
        return true;
    }

    // Text object: `i` or `a`.
    if let Key::Char('i') | Key::Char('a') = input.key
        && !input.ctrl
    {
        let inner = matches!(input.key, Key::Char('i'));
        ed.vim.pending = Pending::OpTextObj { op, count1, inner };
        return true;
    }

    // `g` — awaiting `g` for `gg`.
    if input.key == Key::Char('g') && !input.ctrl {
        ed.vim.pending = Pending::OpG { op, count1 };
        return true;
    }

    // `f`/`F`/`t`/`T` with pending target.
    if let Some((forward, till)) = find_entry(&input) {
        ed.vim.pending = Pending::OpFind {
            op,
            count1,
            forward,
            till,
        };
        return true;
    }

    // Motion.
    let count2 = take_count(&mut ed.vim);
    let total = count1.max(1) * count2.max(1);
    if let Some(motion) = parse_motion(&input) {
        let motion = match motion {
            Motion::FindRepeat { reverse } => match ed.vim.last_find {
                Some((ch, forward, till)) => Motion::Find {
                    ch,
                    forward: if reverse { !forward } else { forward },
                    till,
                },
                None => return true,
            },
            // Vim quirk: `cw` / `cW` are `ce` / `cE` — don't include
            // trailing whitespace so the user's replacement text lands
            // before the following word's leading space.
            Motion::WordFwd if op == Operator::Change => Motion::WordEnd,
            Motion::BigWordFwd if op == Operator::Change => Motion::BigWordEnd,
            m => m,
        };
        apply_op_with_motion(ed, op, &motion, total);
        if let Motion::Find { ch, forward, till } = &motion {
            ed.vim.last_find = Some((*ch, *forward, *till));
        }
        if !ed.vim.replaying && op_is_change(op) {
            ed.vim.last_change = Some(LastChange::OpMotion {
                op,
                motion,
                count: total,
                inserted: None,
            });
        }
        return true;
    }

    // Unknown — cancel the operator.
    true
}

fn handle_op_after_g<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    op: Operator,
    count1: usize,
) -> bool {
    if input.ctrl {
        return true;
    }
    let count2 = take_count(&mut ed.vim);
    let total = count1.max(1) * count2.max(1);
    // Case-op linewise form: `gUgU`, `gugu`, `g~g~` — same effect as
    // `gUU` / `guu` / `g~~`. The leading `g` was consumed into
    // `Pending::OpG`, so here we see the trailing U / u / ~.
    if matches!(
        op,
        Operator::Uppercase | Operator::Lowercase | Operator::ToggleCase
    ) {
        let op_char = match op {
            Operator::Uppercase => 'U',
            Operator::Lowercase => 'u',
            Operator::ToggleCase => '~',
            _ => unreachable!(),
        };
        if input.key == Key::Char(op_char) {
            execute_line_op(ed, op, total);
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::LineOp {
                    op,
                    count: total,
                    inserted: None,
                });
            }
            return true;
        }
    }
    let motion = match input.key {
        Key::Char('g') => Motion::FileTop,
        Key::Char('e') => Motion::WordEndBack,
        Key::Char('E') => Motion::BigWordEndBack,
        Key::Char('j') => Motion::ScreenDown,
        Key::Char('k') => Motion::ScreenUp,
        _ => return true,
    };
    apply_op_with_motion(ed, op, &motion, total);
    if !ed.vim.replaying && op_is_change(op) {
        ed.vim.last_change = Some(LastChange::OpMotion {
            op,
            motion,
            count: total,
            inserted: None,
        });
    }
    true
}

fn handle_after_g<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    let count = take_count(&mut ed.vim);
    // Extract the char and delegate to the shared apply_after_g body.
    // Non-char keys (ctrl sequences etc.) are silently ignored.
    if let Key::Char(ch) = input.key {
        apply_after_g(ed, ch, count);
    }
    true
}

/// Public(crate) entry point for bare `g<x>`. Applies the g-chord effect
/// given the char `ch` and pre-captured `count`. Called by `Editor::after_g`
/// (the public controller API) so the hjkl-vim pending-state reducer can
/// dispatch `AfterGChord` without re-entering the FSM.
pub(crate) fn apply_after_g<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    ch: char,
    count: usize,
) {
    match ch {
        'g' => {
            // gg — top / jump to line count.
            let pre = ed.cursor();
            if count > 1 {
                ed.jump_cursor(count - 1, 0);
            } else {
                ed.jump_cursor(0, 0);
            }
            move_first_non_whitespace(ed);
            if ed.cursor() != pre {
                push_jump(ed, pre);
            }
        }
        'e' => execute_motion(ed, Motion::WordEndBack, count),
        'E' => execute_motion(ed, Motion::BigWordEndBack, count),
        // `g_` — last non-blank on the line.
        '_' => execute_motion(ed, Motion::LastNonBlank, count),
        // `gM` — middle char column of the current line.
        'M' => execute_motion(ed, Motion::LineMiddle, count),
        // `gv` — re-enter the last visual selection.
        'v' => {
            if let Some(snap) = ed.vim.last_visual {
                match snap.mode {
                    Mode::Visual => {
                        ed.vim.visual_anchor = snap.anchor;
                        ed.vim.mode = Mode::Visual;
                    }
                    Mode::VisualLine => {
                        ed.vim.visual_line_anchor = snap.anchor.0;
                        ed.vim.mode = Mode::VisualLine;
                    }
                    Mode::VisualBlock => {
                        ed.vim.block_anchor = snap.anchor;
                        ed.vim.block_vcol = snap.block_vcol;
                        ed.vim.mode = Mode::VisualBlock;
                    }
                    _ => {}
                }
                ed.jump_cursor(snap.cursor.0, snap.cursor.1);
            }
        }
        // `gj` / `gk` — display-line down / up. Walks one screen
        // segment at a time under `:set wrap`; falls back to `j`/`k`
        // when wrap is off (Buffer::move_screen_* handles the branch).
        'j' => execute_motion(ed, Motion::ScreenDown, count),
        'k' => execute_motion(ed, Motion::ScreenUp, count),
        // Case operators: `gU` / `gu` / `g~`. Enter operator-pending
        // so the next input is treated as the motion / text object /
        // shorthand double (`gUU`, `guu`, `g~~`).
        'U' => {
            ed.vim.pending = Pending::Op {
                op: Operator::Uppercase,
                count1: count,
            };
        }
        'u' => {
            ed.vim.pending = Pending::Op {
                op: Operator::Lowercase,
                count1: count,
            };
        }
        '~' => {
            ed.vim.pending = Pending::Op {
                op: Operator::ToggleCase,
                count1: count,
            };
        }
        'q' => {
            // `gq{motion}` — text reflow operator. Subsequent motion
            // / textobj rides the same operator pipeline.
            ed.vim.pending = Pending::Op {
                op: Operator::Reflow,
                count1: count,
            };
        }
        'J' => {
            // `gJ` — join line below without inserting a space.
            for _ in 0..count.max(1) {
                ed.push_undo();
                join_line_raw(ed);
            }
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::JoinLine {
                    count: count.max(1),
                });
            }
        }
        'd' => {
            // `gd` — goto definition. hjkl-engine doesn't run an LSP
            // itself; raise an intent the host drains and routes to
            // `sqls`. The cursor stays put here — the host moves it
            // once it has the target location.
            ed.pending_lsp = Some(crate::editor::LspIntent::GotoDefinition);
        }
        // `gi` — go to last-insert position and re-enter insert mode.
        // Matches vim's `:h gi`: moves to the `'^` mark position (the
        // cursor where insert mode was last active, before Esc step-back)
        // and enters insert mode there.
        'i' => {
            if let Some((row, col)) = ed.vim.last_insert_pos {
                ed.jump_cursor(row, col);
            }
            begin_insert(ed, count.max(1), InsertReason::Enter(InsertEntry::I));
        }
        // `g;` / `g,` — walk the change list. `g;` toward older
        // entries, `g,` toward newer.
        ';' => walk_change_list(ed, -1, count.max(1)),
        ',' => walk_change_list(ed, 1, count.max(1)),
        // `g*` / `g#` — like `*` / `#` but match substrings (no `\b`
        // boundary anchors), so the cursor on `foo` finds it inside
        // `foobar` too.
        '*' => execute_motion(
            ed,
            Motion::WordAtCursor {
                forward: true,
                whole_word: false,
            },
            count,
        ),
        '#' => execute_motion(
            ed,
            Motion::WordAtCursor {
                forward: false,
                whole_word: false,
            },
            count,
        ),
        _ => {}
    }
}

fn handle_after_z<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    let count = take_count(&mut ed.vim);
    // Extract the char and delegate to the shared apply_after_z body.
    // Non-char keys (ctrl sequences etc.) are silently ignored.
    if let Key::Char(ch) = input.key {
        apply_after_z(ed, ch, count);
    }
    true
}

/// Public(crate) entry point for bare `z<x>`. Applies the z-chord effect
/// given the char `ch` and pre-captured `count`. Called by `Editor::after_z`
/// (the public controller API) so the hjkl-vim pending-state reducer can
/// dispatch `AfterZChord` without re-entering the engine FSM.
pub(crate) fn apply_after_z<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    ch: char,
    count: usize,
) {
    use crate::editor::CursorScrollTarget;
    let row = ed.cursor().0;
    match ch {
        'z' => {
            ed.scroll_cursor_to(CursorScrollTarget::Center);
            ed.vim.viewport_pinned = true;
        }
        't' => {
            ed.scroll_cursor_to(CursorScrollTarget::Top);
            ed.vim.viewport_pinned = true;
        }
        'b' => {
            ed.scroll_cursor_to(CursorScrollTarget::Bottom);
            ed.vim.viewport_pinned = true;
        }
        // Folds — operate on the fold under the cursor (or the
        // whole buffer for `R` / `M`). Routed through
        // [`Editor::apply_fold_op`] (0.0.38 Patch C-δ.4) so the host
        // can observe / veto each op via [`Editor::take_fold_ops`].
        'o' => {
            ed.apply_fold_op(crate::types::FoldOp::OpenAt(row));
        }
        'c' => {
            ed.apply_fold_op(crate::types::FoldOp::CloseAt(row));
        }
        'a' => {
            ed.apply_fold_op(crate::types::FoldOp::ToggleAt(row));
        }
        'R' => {
            ed.apply_fold_op(crate::types::FoldOp::OpenAll);
        }
        'M' => {
            ed.apply_fold_op(crate::types::FoldOp::CloseAll);
        }
        'E' => {
            ed.apply_fold_op(crate::types::FoldOp::ClearAll);
        }
        'd' => {
            ed.apply_fold_op(crate::types::FoldOp::RemoveAt(row));
        }
        'f' => {
            if matches!(
                ed.vim.mode,
                Mode::Visual | Mode::VisualLine | Mode::VisualBlock
            ) {
                // `zf` over a Visual selection creates a fold spanning
                // anchor → cursor.
                let anchor_row = match ed.vim.mode {
                    Mode::VisualLine => ed.vim.visual_line_anchor,
                    Mode::VisualBlock => ed.vim.block_anchor.0,
                    _ => ed.vim.visual_anchor.0,
                };
                let cur = ed.cursor().0;
                let top = anchor_row.min(cur);
                let bot = anchor_row.max(cur);
                ed.apply_fold_op(crate::types::FoldOp::Add {
                    start_row: top,
                    end_row: bot,
                    closed: true,
                });
                ed.vim.mode = Mode::Normal;
            } else {
                // `zf{motion}` / `zf{textobj}` — route through the
                // operator pipeline. `Operator::Fold` reuses every
                // motion / text-object / `g`-prefix branch the other
                // operators get.
                ed.vim.pending = Pending::Op {
                    op: Operator::Fold,
                    count1: count,
                };
            }
        }
        _ => {}
    }
}

fn handle_replace<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
) -> bool {
    if let Key::Char(ch) = input.key {
        if ed.vim.mode == Mode::VisualBlock {
            block_replace(ed, ch);
            return true;
        }
        let count = take_count(&mut ed.vim);
        replace_char(ed, ch, count.max(1));
        if !ed.vim.replaying {
            ed.vim.last_change = Some(LastChange::ReplaceChar {
                ch,
                count: count.max(1),
            });
        }
    }
    true
}

fn handle_find_target<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    forward: bool,
    till: bool,
) -> bool {
    let Key::Char(ch) = input.key else {
        return true;
    };
    let count = take_count(&mut ed.vim);
    apply_find_char(ed, ch, forward, till, count.max(1));
    true
}

/// Public(crate) entry point for bare `f<x>` / `F<x>` / `t<x>` / `T<x>`.
/// Applies the motion and records `last_find` for `;` / `,` repeat.
/// Called by `Editor::find_char` (the public controller API) so the
/// hjkl-vim pending-state reducer can dispatch `FindChar` without
/// re-entering the FSM.
pub(crate) fn apply_find_char<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    ch: char,
    forward: bool,
    till: bool,
    count: usize,
) {
    execute_motion(ed, Motion::Find { ch, forward, till }, count.max(1));
    ed.vim.last_find = Some((ch, forward, till));
}

fn handle_op_find_target<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    op: Operator,
    count1: usize,
    forward: bool,
    till: bool,
) -> bool {
    let Key::Char(ch) = input.key else {
        return true;
    };
    let count2 = take_count(&mut ed.vim);
    let total = count1.max(1) * count2.max(1);
    let motion = Motion::Find { ch, forward, till };
    apply_op_with_motion(ed, op, &motion, total);
    ed.vim.last_find = Some((ch, forward, till));
    if !ed.vim.replaying && op_is_change(op) {
        ed.vim.last_change = Some(LastChange::OpMotion {
            op,
            motion,
            count: total,
            inserted: None,
        });
    }
    true
}

fn handle_text_object<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    op: Operator,
    _count1: usize,
    inner: bool,
) -> bool {
    let Key::Char(ch) = input.key else {
        return true;
    };
    let obj = match ch {
        'w' => TextObject::Word { big: false },
        'W' => TextObject::Word { big: true },
        '"' | '\'' | '`' => TextObject::Quote(ch),
        '(' | ')' | 'b' => TextObject::Bracket('('),
        '[' | ']' => TextObject::Bracket('['),
        '{' | '}' | 'B' => TextObject::Bracket('{'),
        '<' | '>' => TextObject::Bracket('<'),
        'p' => TextObject::Paragraph,
        't' => TextObject::XmlTag,
        's' => TextObject::Sentence,
        _ => return true,
    };
    apply_op_with_text_object(ed, op, obj, inner);
    if !ed.vim.replaying && op_is_change(op) {
        ed.vim.last_change = Some(LastChange::OpTextObj {
            op,
            obj,
            inner,
            inserted: None,
        });
    }
    true
}

fn handle_visual_text_obj<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: Input,
    inner: bool,
) -> bool {
    let Key::Char(ch) = input.key else {
        return true;
    };
    let obj = match ch {
        'w' => TextObject::Word { big: false },
        'W' => TextObject::Word { big: true },
        '"' | '\'' | '`' => TextObject::Quote(ch),
        '(' | ')' | 'b' => TextObject::Bracket('('),
        '[' | ']' => TextObject::Bracket('['),
        '{' | '}' | 'B' => TextObject::Bracket('{'),
        '<' | '>' => TextObject::Bracket('<'),
        'p' => TextObject::Paragraph,
        't' => TextObject::XmlTag,
        's' => TextObject::Sentence,
        _ => return true,
    };
    let Some((start, end, kind)) = text_object_range(ed, obj, inner) else {
        return true;
    };
    // Anchor + cursor position the char-wise highlight / operator range;
    // for linewise text-objects we switch into VisualLine with the
    // appropriate row anchor.
    match kind {
        MotionKind::Linewise => {
            ed.vim.visual_line_anchor = start.0;
            ed.vim.mode = Mode::VisualLine;
            ed.jump_cursor(end.0, 0);
        }
        _ => {
            ed.vim.mode = Mode::Visual;
            ed.vim.visual_anchor = (start.0, start.1);
            let (er, ec) = retreat_one(ed, end);
            ed.jump_cursor(er, ec);
        }
    }
    true
}

/// Move `pos` back by one character, clamped to (0, 0).
fn retreat_one<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    pos: (usize, usize),
) -> (usize, usize) {
    let (r, c) = pos;
    if c > 0 {
        (r, c - 1)
    } else if r > 0 {
        let prev_len = buf_line_bytes(&ed.buffer, r - 1);
        (r - 1, prev_len)
    } else {
        (0, 0)
    }
}

fn op_is_change(op: Operator) -> bool {
    matches!(op, Operator::Delete | Operator::Change)
}

// ─── Normal-only commands (not motion, not operator) ───────────────────────

fn handle_normal_only<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    input: &Input,
    count: usize,
) -> bool {
    if input.ctrl {
        return false;
    }
    match input.key {
        Key::Char('i') => {
            begin_insert(ed, count.max(1), InsertReason::Enter(InsertEntry::I));
            true
        }
        Key::Char('I') => {
            move_first_non_whitespace(ed);
            begin_insert(ed, count.max(1), InsertReason::Enter(InsertEntry::ShiftI));
            true
        }
        Key::Char('a') => {
            crate::motions::move_right_to_end(&mut ed.buffer, 1);
            ed.push_buffer_cursor_to_textarea();
            begin_insert(ed, count.max(1), InsertReason::Enter(InsertEntry::A));
            true
        }
        Key::Char('A') => {
            crate::motions::move_line_end(&mut ed.buffer);
            crate::motions::move_right_to_end(&mut ed.buffer, 1);
            ed.push_buffer_cursor_to_textarea();
            begin_insert(ed, count.max(1), InsertReason::Enter(InsertEntry::ShiftA));
            true
        }
        Key::Char('R') => {
            // Replace mode — overstrike each typed cell. Reuses the
            // insert-mode key handler with a Replace-flavoured session.
            begin_insert(ed, count.max(1), InsertReason::Replace);
            true
        }
        Key::Char('o') => {
            use hjkl_buffer::{Edit, Position};
            ed.push_undo();
            // Snapshot BEFORE the newline so replay sees "\n<text>" as the
            // delta and produces one fresh line per iteration.
            begin_insert_noundo(ed, count.max(1), InsertReason::Open { above: false });
            ed.sync_buffer_content_from_textarea();
            let row = buf_cursor_pos(&ed.buffer).row;
            let line_chars = buf_line_chars(&ed.buffer, row);
            // Smart/auto-indent based on the current line (becomes the
            // "previous" line for the freshly-opened line below).
            let prev_line = buf_line(&ed.buffer, row).unwrap_or_default();
            let indent = compute_enter_indent(&ed.settings, prev_line);
            ed.mutate_edit(Edit::InsertStr {
                at: Position::new(row, line_chars),
                text: format!("\n{indent}"),
            });
            ed.push_buffer_cursor_to_textarea();
            true
        }
        Key::Char('O') => {
            use hjkl_buffer::{Edit, Position};
            ed.push_undo();
            begin_insert_noundo(ed, count.max(1), InsertReason::Open { above: true });
            ed.sync_buffer_content_from_textarea();
            let row = buf_cursor_pos(&ed.buffer).row;
            // The line opened above sits between row-1 and the current
            // row. Smart/auto-indent off the line above when there is
            // one; otherwise copy the current line's leading whitespace.
            let indent = if row > 0 {
                let above = buf_line(&ed.buffer, row - 1).unwrap_or_default();
                compute_enter_indent(&ed.settings, above)
            } else {
                let cur = buf_line(&ed.buffer, row).unwrap_or_default();
                cur.chars()
                    .take_while(|c| *c == ' ' || *c == '\t')
                    .collect::<String>()
            };
            ed.mutate_edit(Edit::InsertStr {
                at: Position::new(row, 0),
                text: format!("{indent}\n"),
            });
            // After insert, cursor sits on the surviving content one row
            // down — step back up onto the freshly-opened line, then to
            // the end of its indent so insert mode picks up where the
            // user expects to type.
            let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
            crate::motions::move_up(&mut ed.buffer, &folds, 1, &mut ed.sticky_col);
            let new_row = buf_cursor_pos(&ed.buffer).row;
            buf_set_cursor_rc(&mut ed.buffer, new_row, indent.chars().count());
            ed.push_buffer_cursor_to_textarea();
            true
        }
        Key::Char('x') => {
            do_char_delete(ed, true, count.max(1));
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::CharDel {
                    forward: true,
                    count: count.max(1),
                });
            }
            true
        }
        Key::Char('X') => {
            do_char_delete(ed, false, count.max(1));
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::CharDel {
                    forward: false,
                    count: count.max(1),
                });
            }
            true
        }
        Key::Char('~') => {
            for _ in 0..count.max(1) {
                ed.push_undo();
                toggle_case_at_cursor(ed);
            }
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::ToggleCase {
                    count: count.max(1),
                });
            }
            true
        }
        Key::Char('J') => {
            for _ in 0..count.max(1) {
                ed.push_undo();
                join_line(ed);
            }
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::JoinLine {
                    count: count.max(1),
                });
            }
            true
        }
        Key::Char('D') => {
            ed.push_undo();
            delete_to_eol(ed);
            // Vim parks the cursor on the new last char.
            crate::motions::move_left(&mut ed.buffer, 1);
            ed.push_buffer_cursor_to_textarea();
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::DeleteToEol { inserted: None });
            }
            true
        }
        Key::Char('Y') => {
            // Vim 8 default: `Y` yanks to end of line (same as `y$`).
            apply_op_with_motion(ed, Operator::Yank, &Motion::LineEnd, count.max(1));
            true
        }
        Key::Char('C') => {
            ed.push_undo();
            delete_to_eol(ed);
            begin_insert_noundo(ed, 1, InsertReason::DeleteToEol);
            true
        }
        Key::Char('s') => {
            use hjkl_buffer::{Edit, MotionKind, Position};
            ed.push_undo();
            ed.sync_buffer_content_from_textarea();
            for _ in 0..count.max(1) {
                let cursor = buf_cursor_pos(&ed.buffer);
                let line_chars = buf_line_chars(&ed.buffer, cursor.row);
                if cursor.col >= line_chars {
                    break;
                }
                ed.mutate_edit(Edit::DeleteRange {
                    start: cursor,
                    end: Position::new(cursor.row, cursor.col + 1),
                    kind: MotionKind::Char,
                });
            }
            ed.push_buffer_cursor_to_textarea();
            begin_insert_noundo(ed, 1, InsertReason::AfterChange);
            // `s` == `cl` — record as such.
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::OpMotion {
                    op: Operator::Change,
                    motion: Motion::Right,
                    count: count.max(1),
                    inserted: None,
                });
            }
            true
        }
        Key::Char('p') => {
            do_paste(ed, false, count.max(1));
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::Paste {
                    before: false,
                    count: count.max(1),
                });
            }
            true
        }
        Key::Char('P') => {
            do_paste(ed, true, count.max(1));
            if !ed.vim.replaying {
                ed.vim.last_change = Some(LastChange::Paste {
                    before: true,
                    count: count.max(1),
                });
            }
            true
        }
        Key::Char('u') => {
            do_undo(ed);
            true
        }
        Key::Char('r') => {
            ed.vim.count = count;
            ed.vim.pending = Pending::Replace;
            true
        }
        Key::Char('/') => {
            enter_search(ed, true);
            true
        }
        Key::Char('?') => {
            enter_search(ed, false);
            true
        }
        Key::Char('.') => {
            replay_last_change(ed, count);
            true
        }
        _ => false,
    }
}

/// Variant of begin_insert that doesn't push_undo (caller already did).
fn begin_insert_noundo<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    count: usize,
    reason: InsertReason,
) {
    let reason = if ed.vim.replaying {
        InsertReason::ReplayOnly
    } else {
        reason
    };
    let (row, _) = ed.cursor();
    ed.vim.insert_session = Some(InsertSession {
        count,
        row_min: row,
        row_max: row,
        before_lines: buf_lines_to_vec(&ed.buffer),
        reason,
    });
    ed.vim.mode = Mode::Insert;
}

// ─── Operator × Motion application ─────────────────────────────────────────

fn apply_op_with_motion<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    motion: &Motion,
    count: usize,
) {
    let start = ed.cursor();
    // Tentatively apply motion to find the endpoint. Operator context
    // so `l` on the last char advances past-last (standard vim
    // exclusive-motion endpoint behaviour), enabling `dl` / `cl` /
    // `yl` to cover the final char.
    apply_motion_cursor_ctx(ed, motion, count, true);
    let end = ed.cursor();
    let kind = motion_kind(motion);
    // Restore cursor before selecting (so Yank leaves cursor at start).
    ed.jump_cursor(start.0, start.1);
    run_operator_over_range(ed, op, start, end, kind);
}

fn apply_op_with_text_object<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    obj: TextObject,
    inner: bool,
) {
    let Some((start, end, kind)) = text_object_range(ed, obj, inner) else {
        return;
    };
    ed.jump_cursor(start.0, start.1);
    run_operator_over_range(ed, op, start, end, kind);
}

fn motion_kind(motion: &Motion) -> MotionKind {
    match motion {
        Motion::Up | Motion::Down | Motion::ScreenUp | Motion::ScreenDown => MotionKind::Linewise,
        Motion::FileTop | Motion::FileBottom => MotionKind::Linewise,
        Motion::ViewportTop | Motion::ViewportMiddle | Motion::ViewportBottom => {
            MotionKind::Linewise
        }
        Motion::WordEnd | Motion::BigWordEnd | Motion::WordEndBack | Motion::BigWordEndBack => {
            MotionKind::Inclusive
        }
        Motion::Find { .. } => MotionKind::Inclusive,
        Motion::MatchBracket => MotionKind::Inclusive,
        // `$` now lands on the last char — operator ranges include it.
        Motion::LineEnd => MotionKind::Inclusive,
        _ => MotionKind::Exclusive,
    }
}

fn run_operator_over_range<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    start: (usize, usize),
    end: (usize, usize),
    kind: MotionKind,
) {
    let (top, bot) = order(start, end);
    if top == bot {
        return;
    }

    match op {
        Operator::Yank => {
            let text = read_vim_range(ed, top, bot, kind);
            if !text.is_empty() {
                ed.record_yank_to_host(text.clone());
                ed.record_yank(text, matches!(kind, MotionKind::Linewise));
            }
            // Vim `:h '[` / `:h ']`: after a yank `[` = first yanked char,
            // `]` = last yanked char. Mode-aware: linewise snaps to line
            // edges; charwise uses the actual inclusive endpoint.
            let rbr = match kind {
                MotionKind::Linewise => {
                    let last_col = buf_line_chars(&ed.buffer, bot.0).saturating_sub(1);
                    (bot.0, last_col)
                }
                MotionKind::Inclusive => (bot.0, bot.1),
                MotionKind::Exclusive => (bot.0, bot.1.saturating_sub(1)),
            };
            ed.set_mark('[', top);
            ed.set_mark(']', rbr);
            buf_set_cursor_rc(&mut ed.buffer, top.0, top.1);
            ed.push_buffer_cursor_to_textarea();
        }
        Operator::Delete => {
            ed.push_undo();
            cut_vim_range(ed, top, bot, kind);
            // After a charwise / inclusive delete the buffer cursor is
            // placed at `start` by the edit path. In Normal mode the
            // cursor max col is `line_len - 1`; clamp it here so e.g.
            // `d$` doesn't leave the cursor one past the new line end.
            if !matches!(kind, MotionKind::Linewise) {
                clamp_cursor_to_normal_mode(ed);
            }
            ed.vim.mode = Mode::Normal;
            // Vim `:h '[` / `:h ']`: after a delete both marks park at
            // the cursor position where the deletion collapsed (the join
            // point). Set after the cut and clamp so the position is final.
            let pos = ed.cursor();
            ed.set_mark('[', pos);
            ed.set_mark(']', pos);
        }
        Operator::Change => {
            // Vim `:h '[`: `[` is set to the start of the changed range
            // before the cut. `]` is deferred to insert-exit (AfterChange
            // path in finish_insert_session) where the cursor sits on the
            // last inserted char.
            ed.vim.change_mark_start = Some(top);
            ed.push_undo();
            cut_vim_range(ed, top, bot, kind);
            begin_insert_noundo(ed, 1, InsertReason::AfterChange);
        }
        Operator::Uppercase | Operator::Lowercase | Operator::ToggleCase => {
            apply_case_op_to_selection(ed, op, top, bot, kind);
        }
        Operator::Indent | Operator::Outdent => {
            // Indent / outdent are always linewise even when triggered
            // by a char-wise motion (e.g. `>w` indents the whole line).
            ed.push_undo();
            if op == Operator::Indent {
                indent_rows(ed, top.0, bot.0, 1);
            } else {
                outdent_rows(ed, top.0, bot.0, 1);
            }
            ed.vim.mode = Mode::Normal;
        }
        Operator::Fold => {
            // Always linewise — fold the spanned rows regardless of the
            // motion's natural kind. Cursor lands on `top.0` to mirror
            // the visual `zf` path.
            if bot.0 >= top.0 {
                ed.apply_fold_op(crate::types::FoldOp::Add {
                    start_row: top.0,
                    end_row: bot.0,
                    closed: true,
                });
            }
            buf_set_cursor_rc(&mut ed.buffer, top.0, top.1);
            ed.push_buffer_cursor_to_textarea();
            ed.vim.mode = Mode::Normal;
        }
        Operator::Reflow => {
            ed.push_undo();
            reflow_rows(ed, top.0, bot.0);
            ed.vim.mode = Mode::Normal;
        }
    }
}

/// Greedy word-wrap the rows in `[top, bot]` to `settings.textwidth`.
/// Splits on blank-line boundaries so paragraph structure is
/// preserved. Each paragraph's words are joined with single spaces
/// before re-wrapping.
fn reflow_rows<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    top: usize,
    bot: usize,
) {
    let width = ed.settings().textwidth.max(1);
    let mut lines: Vec<String> = buf_lines_to_vec(&ed.buffer);
    let bot = bot.min(lines.len().saturating_sub(1));
    if top > bot {
        return;
    }
    let original = lines[top..=bot].to_vec();
    let mut wrapped: Vec<String> = Vec::new();
    let mut paragraph: Vec<String> = Vec::new();
    let flush = |para: &mut Vec<String>, out: &mut Vec<String>, width: usize| {
        if para.is_empty() {
            return;
        }
        let words = para.join(" ");
        let mut current = String::new();
        for word in words.split_whitespace() {
            let extra = if current.is_empty() {
                word.chars().count()
            } else {
                current.chars().count() + 1 + word.chars().count()
            };
            if extra > width && !current.is_empty() {
                out.push(std::mem::take(&mut current));
                current.push_str(word);
            } else if current.is_empty() {
                current.push_str(word);
            } else {
                current.push(' ');
                current.push_str(word);
            }
        }
        if !current.is_empty() {
            out.push(current);
        }
        para.clear();
    };
    for line in &original {
        if line.trim().is_empty() {
            flush(&mut paragraph, &mut wrapped, width);
            wrapped.push(String::new());
        } else {
            paragraph.push(line.clone());
        }
    }
    flush(&mut paragraph, &mut wrapped, width);

    // Splice back. push_undo above means `u` reverses.
    let after: Vec<String> = lines.split_off(bot + 1);
    lines.truncate(top);
    lines.extend(wrapped);
    lines.extend(after);
    ed.restore(lines, (top, 0));
    ed.mark_content_dirty();
}

/// Transform the range `[top, bot]` (vim `MotionKind`) in place with
/// the given case operator. Cursor lands on `top` afterward — vim
/// convention for `gU{motion}` / `gu{motion}` / `g~{motion}`.
/// Preserves the textarea yank buffer (vim's case operators don't
/// touch registers).
fn apply_case_op_to_selection<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    top: (usize, usize),
    bot: (usize, usize),
    kind: MotionKind,
) {
    use hjkl_buffer::Edit;
    ed.push_undo();
    let saved_yank = ed.yank().to_string();
    let saved_yank_linewise = ed.vim.yank_linewise;
    let selection = cut_vim_range(ed, top, bot, kind);
    let transformed = match op {
        Operator::Uppercase => selection.to_uppercase(),
        Operator::Lowercase => selection.to_lowercase(),
        Operator::ToggleCase => toggle_case_str(&selection),
        _ => unreachable!(),
    };
    if !transformed.is_empty() {
        let cursor = buf_cursor_pos(&ed.buffer);
        ed.mutate_edit(Edit::InsertStr {
            at: cursor,
            text: transformed,
        });
    }
    buf_set_cursor_rc(&mut ed.buffer, top.0, top.1);
    ed.push_buffer_cursor_to_textarea();
    ed.set_yank(saved_yank);
    ed.vim.yank_linewise = saved_yank_linewise;
    ed.vim.mode = Mode::Normal;
}

/// Prepend `count * shiftwidth` spaces to each row in `[top, bot]`.
/// Rows that are empty are skipped (vim leaves blank lines alone when
/// indenting). `shiftwidth` is read from `editor.settings()` so
/// `:set shiftwidth=N` takes effect on the next operation.
fn indent_rows<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    top: usize,
    bot: usize,
    count: usize,
) {
    ed.sync_buffer_content_from_textarea();
    let width = ed.settings().shiftwidth * count.max(1);
    let pad: String = " ".repeat(width);
    let mut lines: Vec<String> = buf_lines_to_vec(&ed.buffer);
    let bot = bot.min(lines.len().saturating_sub(1));
    for line in lines.iter_mut().take(bot + 1).skip(top) {
        if !line.is_empty() {
            line.insert_str(0, &pad);
        }
    }
    // Restore cursor to first non-blank of the top row so the next
    // vertical motion aims sensibly — matches vim's `>>` convention.
    ed.restore(lines, (top, 0));
    move_first_non_whitespace(ed);
}

/// Remove up to `count * shiftwidth` leading spaces (or tabs) from
/// each row in `[top, bot]`. Rows with less leading whitespace have
/// all their indent stripped, not clipped to zero length.
fn outdent_rows<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    top: usize,
    bot: usize,
    count: usize,
) {
    ed.sync_buffer_content_from_textarea();
    let width = ed.settings().shiftwidth * count.max(1);
    let mut lines: Vec<String> = buf_lines_to_vec(&ed.buffer);
    let bot = bot.min(lines.len().saturating_sub(1));
    for line in lines.iter_mut().take(bot + 1).skip(top) {
        let strip: usize = line
            .chars()
            .take(width)
            .take_while(|c| *c == ' ' || *c == '\t')
            .count();
        if strip > 0 {
            let byte_len: usize = line.chars().take(strip).map(|c| c.len_utf8()).sum();
            line.drain(..byte_len);
        }
    }
    ed.restore(lines, (top, 0));
    move_first_non_whitespace(ed);
}

fn toggle_case_str(s: &str) -> String {
    s.chars()
        .map(|c| {
            if c.is_lowercase() {
                c.to_uppercase().next().unwrap_or(c)
            } else if c.is_uppercase() {
                c.to_lowercase().next().unwrap_or(c)
            } else {
                c
            }
        })
        .collect()
}

fn order(a: (usize, usize), b: (usize, usize)) -> ((usize, usize), (usize, usize)) {
    if a <= b { (a, b) } else { (b, a) }
}

/// Clamp the buffer cursor to normal-mode valid position: col may not
/// exceed `line.chars().count().saturating_sub(1)` (or 0 on an empty
/// line). Vim applies this clamp on every return to Normal mode after an
/// operator or Esc-from-insert.
fn clamp_cursor_to_normal_mode<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    let (row, col) = ed.cursor();
    let line_chars = buf_line_chars(&ed.buffer, row);
    let max_col = line_chars.saturating_sub(1);
    if col > max_col {
        buf_set_cursor_rc(&mut ed.buffer, row, max_col);
        ed.push_buffer_cursor_to_textarea();
    }
}

// ─── dd/cc/yy ──────────────────────────────────────────────────────────────

fn execute_line_op<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    count: usize,
) {
    let (row, col) = ed.cursor();
    let total = buf_row_count(&ed.buffer);
    let end_row = (row + count.saturating_sub(1)).min(total.saturating_sub(1));

    match op {
        Operator::Yank => {
            // yy must not move the cursor.
            let text = read_vim_range(ed, (row, col), (end_row, 0), MotionKind::Linewise);
            if !text.is_empty() {
                ed.record_yank_to_host(text.clone());
                ed.record_yank(text, true);
            }
            // Vim `:h '[` / `:h ']`: yy/Nyy — linewise yank; `[` =
            // (top_row, 0), `]` = (bot_row, last_col).
            let last_col = buf_line_chars(&ed.buffer, end_row).saturating_sub(1);
            ed.set_mark('[', (row, 0));
            ed.set_mark(']', (end_row, last_col));
            buf_set_cursor_rc(&mut ed.buffer, row, col);
            ed.push_buffer_cursor_to_textarea();
            ed.vim.mode = Mode::Normal;
        }
        Operator::Delete => {
            ed.push_undo();
            let deleted_through_last = end_row + 1 >= total;
            cut_vim_range(ed, (row, col), (end_row, 0), MotionKind::Linewise);
            // Vim's `dd` / `Ndd` leaves the cursor on the *first
            // non-blank* of the line that now occupies `row` — or, if
            // the deletion consumed the last line, the line above it.
            let total_after = buf_row_count(&ed.buffer);
            let raw_target = if deleted_through_last {
                row.saturating_sub(1).min(total_after.saturating_sub(1))
            } else {
                row.min(total_after.saturating_sub(1))
            };
            // Clamp off the trailing phantom empty row that arises from a
            // buffer with a trailing newline (stored as ["...", ""]). If
            // the target row is the trailing empty row and there is a real
            // content row above it, use that instead — matching vim's view
            // that the trailing `\n` is a terminator, not a separator.
            let target_row = if raw_target > 0
                && raw_target + 1 == total_after
                && buf_line(&ed.buffer, raw_target)
                    .map(str::is_empty)
                    .unwrap_or(false)
            {
                raw_target - 1
            } else {
                raw_target
            };
            buf_set_cursor_rc(&mut ed.buffer, target_row, 0);
            ed.push_buffer_cursor_to_textarea();
            move_first_non_whitespace(ed);
            ed.sticky_col = Some(ed.cursor().1);
            ed.vim.mode = Mode::Normal;
            // Vim `:h '[` / `:h ']`: dd/Ndd — both marks park at the
            // post-delete cursor position (the join point).
            let pos = ed.cursor();
            ed.set_mark('[', pos);
            ed.set_mark(']', pos);
        }
        Operator::Change => {
            // `cc` / `3cc`: wipe contents of the covered lines but leave
            // a single blank line so insert-mode opens on it. Done as two
            // edits: drop rows past the first, then clear row `row`.
            use hjkl_buffer::{Edit, MotionKind as BufKind, Position};
            // Vim `:h '[`: stash change start for `]` deferral on insert-exit.
            ed.vim.change_mark_start = Some((row, 0));
            ed.push_undo();
            ed.sync_buffer_content_from_textarea();
            // Read the cut payload first so yank reflects every line.
            let payload = read_vim_range(ed, (row, col), (end_row, 0), MotionKind::Linewise);
            if end_row > row {
                ed.mutate_edit(Edit::DeleteRange {
                    start: Position::new(row + 1, 0),
                    end: Position::new(end_row, 0),
                    kind: BufKind::Line,
                });
            }
            let line_chars = buf_line_chars(&ed.buffer, row);
            if line_chars > 0 {
                ed.mutate_edit(Edit::DeleteRange {
                    start: Position::new(row, 0),
                    end: Position::new(row, line_chars),
                    kind: BufKind::Char,
                });
            }
            if !payload.is_empty() {
                ed.record_yank_to_host(payload.clone());
                ed.record_delete(payload, true);
            }
            buf_set_cursor_rc(&mut ed.buffer, row, 0);
            ed.push_buffer_cursor_to_textarea();
            begin_insert_noundo(ed, 1, InsertReason::AfterChange);
        }
        Operator::Uppercase | Operator::Lowercase | Operator::ToggleCase => {
            // `gUU` / `guu` / `g~~` — linewise case transform over
            // [row, end_row]. Preserve cursor on `row` (first non-blank
            // lines up with vim's behaviour).
            apply_case_op_to_selection(ed, op, (row, col), (end_row, 0), MotionKind::Linewise);
            // After case-op on a linewise range vim puts the cursor on
            // the first non-blank of the starting line.
            move_first_non_whitespace(ed);
        }
        Operator::Indent | Operator::Outdent => {
            // `>>` / `N>>` / `<<` / `N<<` — linewise indent / outdent.
            ed.push_undo();
            if op == Operator::Indent {
                indent_rows(ed, row, end_row, 1);
            } else {
                outdent_rows(ed, row, end_row, 1);
            }
            ed.sticky_col = Some(ed.cursor().1);
            ed.vim.mode = Mode::Normal;
        }
        // No doubled form — `zfzf` is two consecutive `zf` chords.
        Operator::Fold => unreachable!("Fold has no line-op double"),
        Operator::Reflow => {
            // `gqq` / `Ngqq` — reflow `count` rows starting at the cursor.
            ed.push_undo();
            reflow_rows(ed, row, end_row);
            move_first_non_whitespace(ed);
            ed.sticky_col = Some(ed.cursor().1);
            ed.vim.mode = Mode::Normal;
        }
    }
}

// ─── Visual mode operators ─────────────────────────────────────────────────

fn apply_visual_operator<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
) {
    match ed.vim.mode {
        Mode::VisualLine => {
            let cursor_row = buf_cursor_pos(&ed.buffer).row;
            let top = cursor_row.min(ed.vim.visual_line_anchor);
            let bot = cursor_row.max(ed.vim.visual_line_anchor);
            ed.vim.yank_linewise = true;
            match op {
                Operator::Yank => {
                    let text = read_vim_range(ed, (top, 0), (bot, 0), MotionKind::Linewise);
                    if !text.is_empty() {
                        ed.record_yank_to_host(text.clone());
                        ed.record_yank(text, true);
                    }
                    buf_set_cursor_rc(&mut ed.buffer, top, 0);
                    ed.push_buffer_cursor_to_textarea();
                    ed.vim.mode = Mode::Normal;
                }
                Operator::Delete => {
                    ed.push_undo();
                    cut_vim_range(ed, (top, 0), (bot, 0), MotionKind::Linewise);
                    ed.vim.mode = Mode::Normal;
                }
                Operator::Change => {
                    // Vim `Vc`: wipe the line contents but leave a blank
                    // line in place so insert-mode starts on an empty row.
                    use hjkl_buffer::{Edit, MotionKind as BufKind, Position};
                    ed.push_undo();
                    ed.sync_buffer_content_from_textarea();
                    let payload = read_vim_range(ed, (top, 0), (bot, 0), MotionKind::Linewise);
                    if bot > top {
                        ed.mutate_edit(Edit::DeleteRange {
                            start: Position::new(top + 1, 0),
                            end: Position::new(bot, 0),
                            kind: BufKind::Line,
                        });
                    }
                    let line_chars = buf_line_chars(&ed.buffer, top);
                    if line_chars > 0 {
                        ed.mutate_edit(Edit::DeleteRange {
                            start: Position::new(top, 0),
                            end: Position::new(top, line_chars),
                            kind: BufKind::Char,
                        });
                    }
                    if !payload.is_empty() {
                        ed.record_yank_to_host(payload.clone());
                        ed.record_delete(payload, true);
                    }
                    buf_set_cursor_rc(&mut ed.buffer, top, 0);
                    ed.push_buffer_cursor_to_textarea();
                    begin_insert_noundo(ed, 1, InsertReason::AfterChange);
                }
                Operator::Uppercase | Operator::Lowercase | Operator::ToggleCase => {
                    let bot = buf_cursor_pos(&ed.buffer)
                        .row
                        .max(ed.vim.visual_line_anchor);
                    apply_case_op_to_selection(ed, op, (top, 0), (bot, 0), MotionKind::Linewise);
                    move_first_non_whitespace(ed);
                }
                Operator::Indent | Operator::Outdent => {
                    ed.push_undo();
                    let (cursor_row, _) = ed.cursor();
                    let bot = cursor_row.max(ed.vim.visual_line_anchor);
                    if op == Operator::Indent {
                        indent_rows(ed, top, bot, 1);
                    } else {
                        outdent_rows(ed, top, bot, 1);
                    }
                    ed.vim.mode = Mode::Normal;
                }
                Operator::Reflow => {
                    ed.push_undo();
                    let (cursor_row, _) = ed.cursor();
                    let bot = cursor_row.max(ed.vim.visual_line_anchor);
                    reflow_rows(ed, top, bot);
                    ed.vim.mode = Mode::Normal;
                }
                // Visual `zf` is handled inline in `handle_after_z`,
                // never routed through this dispatcher.
                Operator::Fold => unreachable!("Visual zf takes its own path"),
            }
        }
        Mode::Visual => {
            ed.vim.yank_linewise = false;
            let anchor = ed.vim.visual_anchor;
            let cursor = ed.cursor();
            let (top, bot) = order(anchor, cursor);
            match op {
                Operator::Yank => {
                    let text = read_vim_range(ed, top, bot, MotionKind::Inclusive);
                    if !text.is_empty() {
                        ed.record_yank_to_host(text.clone());
                        ed.record_yank(text, false);
                    }
                    buf_set_cursor_rc(&mut ed.buffer, top.0, top.1);
                    ed.push_buffer_cursor_to_textarea();
                    ed.vim.mode = Mode::Normal;
                }
                Operator::Delete => {
                    ed.push_undo();
                    cut_vim_range(ed, top, bot, MotionKind::Inclusive);
                    ed.vim.mode = Mode::Normal;
                }
                Operator::Change => {
                    ed.push_undo();
                    cut_vim_range(ed, top, bot, MotionKind::Inclusive);
                    begin_insert_noundo(ed, 1, InsertReason::AfterChange);
                }
                Operator::Uppercase | Operator::Lowercase | Operator::ToggleCase => {
                    // Anchor stays where the visual selection started.
                    let anchor = ed.vim.visual_anchor;
                    let cursor = ed.cursor();
                    let (top, bot) = order(anchor, cursor);
                    apply_case_op_to_selection(ed, op, top, bot, MotionKind::Inclusive);
                }
                Operator::Indent | Operator::Outdent => {
                    ed.push_undo();
                    let anchor = ed.vim.visual_anchor;
                    let cursor = ed.cursor();
                    let (top, bot) = order(anchor, cursor);
                    if op == Operator::Indent {
                        indent_rows(ed, top.0, bot.0, 1);
                    } else {
                        outdent_rows(ed, top.0, bot.0, 1);
                    }
                    ed.vim.mode = Mode::Normal;
                }
                Operator::Reflow => {
                    ed.push_undo();
                    let anchor = ed.vim.visual_anchor;
                    let cursor = ed.cursor();
                    let (top, bot) = order(anchor, cursor);
                    reflow_rows(ed, top.0, bot.0);
                    ed.vim.mode = Mode::Normal;
                }
                Operator::Fold => unreachable!("Visual zf takes its own path"),
            }
        }
        Mode::VisualBlock => apply_block_operator(ed, op),
        _ => {}
    }
}

/// Compute `(top_row, bot_row, left_col, right_col)` for the current
/// VisualBlock selection. Columns are inclusive on both ends. Uses the
/// tracked virtual column (updated by h/l, preserved across j/k) so
/// ragged / empty rows don't collapse the block's width.
fn block_bounds<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
) -> (usize, usize, usize, usize) {
    let (ar, ac) = ed.vim.block_anchor;
    let (cr, _) = ed.cursor();
    let cc = ed.vim.block_vcol;
    let top = ar.min(cr);
    let bot = ar.max(cr);
    let left = ac.min(cc);
    let right = ac.max(cc);
    (top, bot, left, right)
}

/// Update the virtual column after a motion in VisualBlock mode.
/// Horizontal motions sync `block_vcol` to the new cursor column;
/// vertical / non-h/l motions leave it alone so the intended column
/// survives clamping to shorter lines.
fn update_block_vcol<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    motion: &Motion,
) {
    match motion {
        Motion::Left
        | Motion::Right
        | Motion::WordFwd
        | Motion::BigWordFwd
        | Motion::WordBack
        | Motion::BigWordBack
        | Motion::WordEnd
        | Motion::BigWordEnd
        | Motion::WordEndBack
        | Motion::BigWordEndBack
        | Motion::LineStart
        | Motion::FirstNonBlank
        | Motion::LineEnd
        | Motion::Find { .. }
        | Motion::FindRepeat { .. }
        | Motion::MatchBracket => {
            ed.vim.block_vcol = ed.cursor().1;
        }
        // Up / Down / FileTop / FileBottom / Search — preserve vcol.
        _ => {}
    }
}

/// Yank / delete / change / replace a rectangular selection. Yanked text
/// is stored as one string per row joined with `\n` so pasting reproduces
/// the block as sequential lines. (Vim's true block-paste reinserts as
/// columns; we render the content with our char-wise paste path.)
fn apply_block_operator<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
) {
    let (top, bot, left, right) = block_bounds(ed);
    // Snapshot the block text for yank / clipboard.
    let yank = block_yank(ed, top, bot, left, right);

    match op {
        Operator::Yank => {
            if !yank.is_empty() {
                ed.record_yank_to_host(yank.clone());
                ed.record_yank(yank, false);
            }
            ed.vim.mode = Mode::Normal;
            ed.jump_cursor(top, left);
        }
        Operator::Delete => {
            ed.push_undo();
            delete_block_contents(ed, top, bot, left, right);
            if !yank.is_empty() {
                ed.record_yank_to_host(yank.clone());
                ed.record_delete(yank, false);
            }
            ed.vim.mode = Mode::Normal;
            ed.jump_cursor(top, left);
        }
        Operator::Change => {
            ed.push_undo();
            delete_block_contents(ed, top, bot, left, right);
            if !yank.is_empty() {
                ed.record_yank_to_host(yank.clone());
                ed.record_delete(yank, false);
            }
            ed.jump_cursor(top, left);
            begin_insert_noundo(
                ed,
                1,
                InsertReason::BlockChange {
                    top,
                    bot,
                    col: left,
                },
            );
        }
        Operator::Uppercase | Operator::Lowercase | Operator::ToggleCase => {
            ed.push_undo();
            transform_block_case(ed, op, top, bot, left, right);
            ed.vim.mode = Mode::Normal;
            ed.jump_cursor(top, left);
        }
        Operator::Indent | Operator::Outdent => {
            // VisualBlock `>` / `<` falls back to linewise indent over
            // the block's row range — vim does the same (column-wise
            // indent/outdent doesn't make sense).
            ed.push_undo();
            if op == Operator::Indent {
                indent_rows(ed, top, bot, 1);
            } else {
                outdent_rows(ed, top, bot, 1);
            }
            ed.vim.mode = Mode::Normal;
        }
        Operator::Fold => unreachable!("Visual zf takes its own path"),
        Operator::Reflow => {
            // Reflow over the block falls back to linewise reflow over
            // the row range — column slicing for `gq` doesn't make
            // sense.
            ed.push_undo();
            reflow_rows(ed, top, bot);
            ed.vim.mode = Mode::Normal;
        }
    }
}

/// In-place case transform over the rectangular block
/// `(top..=bot, left..=right)`. Rows shorter than `left` are left
/// untouched — vim behaves the same way (ragged blocks).
fn transform_block_case<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    op: Operator,
    top: usize,
    bot: usize,
    left: usize,
    right: usize,
) {
    let mut lines: Vec<String> = buf_lines_to_vec(&ed.buffer);
    for r in top..=bot.min(lines.len().saturating_sub(1)) {
        let chars: Vec<char> = lines[r].chars().collect();
        if left >= chars.len() {
            continue;
        }
        let end = (right + 1).min(chars.len());
        let head: String = chars[..left].iter().collect();
        let mid: String = chars[left..end].iter().collect();
        let tail: String = chars[end..].iter().collect();
        let transformed = match op {
            Operator::Uppercase => mid.to_uppercase(),
            Operator::Lowercase => mid.to_lowercase(),
            Operator::ToggleCase => toggle_case_str(&mid),
            _ => mid,
        };
        lines[r] = format!("{head}{transformed}{tail}");
    }
    let saved_yank = ed.yank().to_string();
    let saved_linewise = ed.vim.yank_linewise;
    ed.restore(lines, (top, left));
    ed.set_yank(saved_yank);
    ed.vim.yank_linewise = saved_linewise;
}

fn block_yank<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    top: usize,
    bot: usize,
    left: usize,
    right: usize,
) -> String {
    let lines = buf_lines_to_vec(&ed.buffer);
    let mut rows: Vec<String> = Vec::new();
    for r in top..=bot {
        let line = match lines.get(r) {
            Some(l) => l,
            None => break,
        };
        let chars: Vec<char> = line.chars().collect();
        let end = (right + 1).min(chars.len());
        if left >= chars.len() {
            rows.push(String::new());
        } else {
            rows.push(chars[left..end].iter().collect());
        }
    }
    rows.join("\n")
}

fn delete_block_contents<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    top: usize,
    bot: usize,
    left: usize,
    right: usize,
) {
    use hjkl_buffer::{Edit, MotionKind, Position};
    ed.sync_buffer_content_from_textarea();
    let last_row = bot.min(buf_row_count(&ed.buffer).saturating_sub(1));
    if last_row < top {
        return;
    }
    ed.mutate_edit(Edit::DeleteRange {
        start: Position::new(top, left),
        end: Position::new(last_row, right),
        kind: MotionKind::Block,
    });
    ed.push_buffer_cursor_to_textarea();
}

/// Replace each character cell in the block with `ch`.
fn block_replace<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>, ch: char) {
    let (top, bot, left, right) = block_bounds(ed);
    ed.push_undo();
    ed.sync_buffer_content_from_textarea();
    let mut lines: Vec<String> = buf_lines_to_vec(&ed.buffer);
    for r in top..=bot.min(lines.len().saturating_sub(1)) {
        let chars: Vec<char> = lines[r].chars().collect();
        if left >= chars.len() {
            continue;
        }
        let end = (right + 1).min(chars.len());
        let before: String = chars[..left].iter().collect();
        let middle: String = std::iter::repeat_n(ch, end - left).collect();
        let after: String = chars[end..].iter().collect();
        lines[r] = format!("{before}{middle}{after}");
    }
    reset_textarea_lines(ed, lines);
    ed.vim.mode = Mode::Normal;
    ed.jump_cursor(top, left);
}

/// Replace buffer content with `lines` while preserving the cursor.
/// Used by indent / outdent / block_replace to wholesale rewrite
/// rows without going through the per-edit funnel.
fn reset_textarea_lines<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    lines: Vec<String>,
) {
    let cursor = ed.cursor();
    crate::types::BufferEdit::replace_all(&mut ed.buffer, &lines.join("\n"));
    buf_set_cursor_rc(&mut ed.buffer, cursor.0, cursor.1);
    ed.mark_content_dirty();
}

// ─── Visual-line helpers ───────────────────────────────────────────────────

// ─── Text-object range computation ─────────────────────────────────────────

/// Cursor position as `(row, col)`.
type Pos = (usize, usize);

/// Returns `(start, end, kind)` where `end` is *exclusive* (one past the
/// last character to act on). `kind` is `Linewise` for line-oriented text
/// objects like paragraphs and `Exclusive` otherwise.
fn text_object_range<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    obj: TextObject,
    inner: bool,
) -> Option<(Pos, Pos, MotionKind)> {
    match obj {
        TextObject::Word { big } => {
            word_text_object(ed, inner, big).map(|(s, e)| (s, e, MotionKind::Exclusive))
        }
        TextObject::Quote(q) => {
            quote_text_object(ed, q, inner).map(|(s, e)| (s, e, MotionKind::Exclusive))
        }
        TextObject::Bracket(open) => bracket_text_object(ed, open, inner),
        TextObject::Paragraph => {
            paragraph_text_object(ed, inner).map(|(s, e)| (s, e, MotionKind::Linewise))
        }
        TextObject::XmlTag => {
            tag_text_object(ed, inner).map(|(s, e)| (s, e, MotionKind::Exclusive))
        }
        TextObject::Sentence => {
            sentence_text_object(ed, inner).map(|(s, e)| (s, e, MotionKind::Exclusive))
        }
    }
}

/// `(` / `)` — walk to the next sentence boundary in `forward` direction.
/// Returns `(row, col)` of the boundary's first non-whitespace cell, or
/// `None` when already at the buffer's edge in that direction.
fn sentence_boundary<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    forward: bool,
) -> Option<(usize, usize)> {
    let lines = buf_lines_to_vec(&ed.buffer);
    if lines.is_empty() {
        return None;
    }
    let pos_to_idx = |pos: (usize, usize)| -> usize {
        let mut idx = 0;
        for line in lines.iter().take(pos.0) {
            idx += line.chars().count() + 1;
        }
        idx + pos.1
    };
    let idx_to_pos = |mut idx: usize| -> (usize, usize) {
        for (r, line) in lines.iter().enumerate() {
            let len = line.chars().count();
            if idx <= len {
                return (r, idx);
            }
            idx -= len + 1;
        }
        let last = lines.len().saturating_sub(1);
        (last, lines[last].chars().count())
    };
    let mut chars: Vec<char> = Vec::new();
    for (r, line) in lines.iter().enumerate() {
        chars.extend(line.chars());
        if r + 1 < lines.len() {
            chars.push('\n');
        }
    }
    if chars.is_empty() {
        return None;
    }
    let total = chars.len();
    let cursor_idx = pos_to_idx(ed.cursor()).min(total - 1);
    let is_terminator = |c: char| matches!(c, '.' | '?' | '!');

    if forward {
        // Walk forward looking for a terminator run followed by
        // whitespace; land on the first non-whitespace cell after.
        let mut i = cursor_idx + 1;
        while i < total {
            if is_terminator(chars[i]) {
                while i + 1 < total && is_terminator(chars[i + 1]) {
                    i += 1;
                }
                if i + 1 >= total {
                    return None;
                }
                if chars[i + 1].is_whitespace() {
                    let mut j = i + 1;
                    while j < total && chars[j].is_whitespace() {
                        j += 1;
                    }
                    if j >= total {
                        return None;
                    }
                    return Some(idx_to_pos(j));
                }
            }
            i += 1;
        }
        None
    } else {
        // Walk backward to find the start of the current sentence (if
        // we're already at the start, jump to the previous sentence's
        // start instead).
        let find_start = |from: usize| -> Option<usize> {
            let mut start = from;
            while start > 0 {
                let prev = chars[start - 1];
                if prev.is_whitespace() {
                    let mut k = start - 1;
                    while k > 0 && chars[k - 1].is_whitespace() {
                        k -= 1;
                    }
                    if k > 0 && is_terminator(chars[k - 1]) {
                        break;
                    }
                }
                start -= 1;
            }
            while start < total && chars[start].is_whitespace() {
                start += 1;
            }
            (start < total).then_some(start)
        };
        let current_start = find_start(cursor_idx)?;
        if current_start < cursor_idx {
            return Some(idx_to_pos(current_start));
        }
        // Already at the sentence start — step over the boundary into
        // the previous sentence and find its start.
        let mut k = current_start;
        while k > 0 && chars[k - 1].is_whitespace() {
            k -= 1;
        }
        if k == 0 {
            return None;
        }
        let prev_start = find_start(k - 1)?;
        Some(idx_to_pos(prev_start))
    }
}

/// `is` / `as` — sentence: text up to and including the next sentence
/// terminator (`.`, `?`, `!`). Vim treats `.`/`?`/`!` followed by
/// whitespace (or end-of-line) as a boundary; runs of consecutive
/// terminators stay attached to the same sentence. `as` extends to
/// include trailing whitespace; `is` does not.
fn sentence_text_object<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    inner: bool,
) -> Option<((usize, usize), (usize, usize))> {
    let lines = buf_lines_to_vec(&ed.buffer);
    if lines.is_empty() {
        return None;
    }
    // Flatten the buffer so a sentence can span lines (vim's behaviour).
    // Newlines count as whitespace for boundary detection.
    let pos_to_idx = |pos: (usize, usize)| -> usize {
        let mut idx = 0;
        for line in lines.iter().take(pos.0) {
            idx += line.chars().count() + 1;
        }
        idx + pos.1
    };
    let idx_to_pos = |mut idx: usize| -> (usize, usize) {
        for (r, line) in lines.iter().enumerate() {
            let len = line.chars().count();
            if idx <= len {
                return (r, idx);
            }
            idx -= len + 1;
        }
        let last = lines.len().saturating_sub(1);
        (last, lines[last].chars().count())
    };
    let mut chars: Vec<char> = Vec::new();
    for (r, line) in lines.iter().enumerate() {
        chars.extend(line.chars());
        if r + 1 < lines.len() {
            chars.push('\n');
        }
    }
    if chars.is_empty() {
        return None;
    }

    let cursor_idx = pos_to_idx(ed.cursor()).min(chars.len() - 1);
    let is_terminator = |c: char| matches!(c, '.' | '?' | '!');

    // Walk backward from cursor to find the start of the current
    // sentence. A boundary is: whitespace immediately after a run of
    // terminators (or start-of-buffer).
    let mut start = cursor_idx;
    while start > 0 {
        let prev = chars[start - 1];
        if prev.is_whitespace() {
            // Check if the whitespace follows a terminator — if so,
            // we've crossed a sentence boundary; the sentence begins
            // at the first non-whitespace cell *after* this run.
            let mut k = start - 1;
            while k > 0 && chars[k - 1].is_whitespace() {
                k -= 1;
            }
            if k > 0 && is_terminator(chars[k - 1]) {
                break;
            }
        }
        start -= 1;
    }
    // Skip leading whitespace (vim doesn't include it in the
    // sentence body).
    while start < chars.len() && chars[start].is_whitespace() {
        start += 1;
    }
    if start >= chars.len() {
        return None;
    }

    // Walk forward to the sentence end (last terminator before the
    // next whitespace boundary).
    let mut end = start;
    while end < chars.len() {
        if is_terminator(chars[end]) {
            // Consume any consecutive terminators (e.g. `?!`).
            while end + 1 < chars.len() && is_terminator(chars[end + 1]) {
                end += 1;
            }
            // If followed by whitespace or end-of-buffer, that's the
            // boundary.
            if end + 1 >= chars.len() || chars[end + 1].is_whitespace() {
                break;
            }
        }
        end += 1;
    }
    // Inclusive end → exclusive end_idx.
    let end_idx = (end + 1).min(chars.len());

    let final_end = if inner {
        end_idx
    } else {
        // `as`: include trailing whitespace (but stop before the next
        // newline so we don't gobble a paragraph break — vim keeps
        // sentences within a paragraph for the trailing-ws extension).
        let mut e = end_idx;
        while e < chars.len() && chars[e].is_whitespace() && chars[e] != '\n' {
            e += 1;
        }
        e
    };

    Some((idx_to_pos(start), idx_to_pos(final_end)))
}

/// `it` / `at` — XML tag pair text object. Builds a flat char index of
/// the buffer, walks `<...>` tokens to pair tags via a stack, and
/// returns the innermost pair containing the cursor.
fn tag_text_object<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    inner: bool,
) -> Option<((usize, usize), (usize, usize))> {
    let lines = buf_lines_to_vec(&ed.buffer);
    if lines.is_empty() {
        return None;
    }
    // Flatten char positions so we can compare cursor against tag
    // ranges without per-row arithmetic. `\n` between lines counts as
    // a single char.
    let pos_to_idx = |pos: (usize, usize)| -> usize {
        let mut idx = 0;
        for line in lines.iter().take(pos.0) {
            idx += line.chars().count() + 1;
        }
        idx + pos.1
    };
    let idx_to_pos = |mut idx: usize| -> (usize, usize) {
        for (r, line) in lines.iter().enumerate() {
            let len = line.chars().count();
            if idx <= len {
                return (r, idx);
            }
            idx -= len + 1;
        }
        let last = lines.len().saturating_sub(1);
        (last, lines[last].chars().count())
    };
    let mut chars: Vec<char> = Vec::new();
    for (r, line) in lines.iter().enumerate() {
        chars.extend(line.chars());
        if r + 1 < lines.len() {
            chars.push('\n');
        }
    }
    let cursor_idx = pos_to_idx(ed.cursor());

    // Walk `<...>` tokens. Track open tags on a stack; on a matching
    // close pop and consider the pair a candidate when the cursor lies
    // inside its content range. Innermost wins (replace whenever a
    // tighter range turns up). Also track the first complete pair that
    // starts at or after the cursor so we can fall back to a forward
    // scan (targets.vim-style) when the cursor isn't inside any tag.
    let mut stack: Vec<(usize, usize, String)> = Vec::new(); // (open_start, content_start, name)
    let mut innermost: Option<(usize, usize, usize, usize)> = None;
    let mut next_after: Option<(usize, usize, usize, usize)> = None;
    let mut i = 0;
    while i < chars.len() {
        if chars[i] != '<' {
            i += 1;
            continue;
        }
        let mut j = i + 1;
        while j < chars.len() && chars[j] != '>' {
            j += 1;
        }
        if j >= chars.len() {
            break;
        }
        let inside: String = chars[i + 1..j].iter().collect();
        let close_end = j + 1;
        let trimmed = inside.trim();
        if trimmed.starts_with('!') || trimmed.starts_with('?') {
            i = close_end;
            continue;
        }
        if let Some(rest) = trimmed.strip_prefix('/') {
            let name = rest.split_whitespace().next().unwrap_or("").to_string();
            if !name.is_empty()
                && let Some(stack_idx) = stack.iter().rposition(|(_, _, n)| *n == name)
            {
                let (open_start, content_start, _) = stack[stack_idx].clone();
                stack.truncate(stack_idx);
                let content_end = i;
                let candidate = (open_start, content_start, content_end, close_end);
                if cursor_idx >= content_start && cursor_idx <= content_end {
                    innermost = match innermost {
                        Some((_, cs, ce, _)) if cs <= content_start && content_end <= ce => {
                            Some(candidate)
                        }
                        None => Some(candidate),
                        existing => existing,
                    };
                } else if open_start >= cursor_idx && next_after.is_none() {
                    next_after = Some(candidate);
                }
            }
        } else if !trimmed.ends_with('/') {
            let name: String = trimmed
                .split(|c: char| c.is_whitespace() || c == '/')
                .next()
                .unwrap_or("")
                .to_string();
            if !name.is_empty() {
                stack.push((i, close_end, name));
            }
        }
        i = close_end;
    }

    let (open_start, content_start, content_end, close_end) = innermost.or(next_after)?;
    if inner {
        Some((idx_to_pos(content_start), idx_to_pos(content_end)))
    } else {
        Some((idx_to_pos(open_start), idx_to_pos(close_end)))
    }
}

fn is_wordchar(c: char) -> bool {
    c.is_alphanumeric() || c == '_'
}

// `is_keyword_char` lives in hjkl-buffer (used by word motions);
// engine re-uses it via `hjkl_buffer::is_keyword_char` so there's
// one parser, one default, one bug surface.
pub(crate) use hjkl_buffer::is_keyword_char;

fn word_text_object<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    inner: bool,
    big: bool,
) -> Option<((usize, usize), (usize, usize))> {
    let (row, col) = ed.cursor();
    let line = buf_line(&ed.buffer, row)?;
    let chars: Vec<char> = line.chars().collect();
    if chars.is_empty() {
        return None;
    }
    let at = col.min(chars.len().saturating_sub(1));
    let classify = |c: char| -> u8 {
        if c.is_whitespace() {
            0
        } else if big || is_wordchar(c) {
            1
        } else {
            2
        }
    };
    let cls = classify(chars[at]);
    let mut start = at;
    while start > 0 && classify(chars[start - 1]) == cls {
        start -= 1;
    }
    let mut end = at;
    while end + 1 < chars.len() && classify(chars[end + 1]) == cls {
        end += 1;
    }
    // Byte-offset helpers.
    let char_byte = |i: usize| {
        if i >= chars.len() {
            line.len()
        } else {
            line.char_indices().nth(i).map(|(b, _)| b).unwrap_or(0)
        }
    };
    let mut start_col = char_byte(start);
    // Exclusive end: byte index of char AFTER the last-included char.
    let mut end_col = char_byte(end + 1);
    if !inner {
        // `aw` — include trailing whitespace; if there's no trailing ws, absorb leading ws.
        let mut t = end + 1;
        let mut included_trailing = false;
        while t < chars.len() && chars[t].is_whitespace() {
            included_trailing = true;
            t += 1;
        }
        if included_trailing {
            end_col = char_byte(t);
        } else {
            let mut s = start;
            while s > 0 && chars[s - 1].is_whitespace() {
                s -= 1;
            }
            start_col = char_byte(s);
        }
    }
    Some(((row, start_col), (row, end_col)))
}

fn quote_text_object<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    q: char,
    inner: bool,
) -> Option<((usize, usize), (usize, usize))> {
    let (row, col) = ed.cursor();
    let line = buf_line(&ed.buffer, row)?;
    let bytes = line.as_bytes();
    let q_byte = q as u8;
    // Find opening and closing quote on the same line.
    let mut positions: Vec<usize> = Vec::new();
    for (i, &b) in bytes.iter().enumerate() {
        if b == q_byte {
            positions.push(i);
        }
    }
    if positions.len() < 2 {
        return None;
    }
    let mut open_idx: Option<usize> = None;
    let mut close_idx: Option<usize> = None;
    for pair in positions.chunks(2) {
        if pair.len() < 2 {
            break;
        }
        if col >= pair[0] && col <= pair[1] {
            open_idx = Some(pair[0]);
            close_idx = Some(pair[1]);
            break;
        }
        if col < pair[0] {
            open_idx = Some(pair[0]);
            close_idx = Some(pair[1]);
            break;
        }
    }
    let open = open_idx?;
    let close = close_idx?;
    // End columns are *exclusive* — one past the last character to act on.
    if inner {
        if close <= open + 1 {
            return None;
        }
        Some(((row, open + 1), (row, close)))
    } else {
        // `da<q>` — "around" includes the surrounding whitespace on one
        // side: trailing whitespace if any exists after the closing quote;
        // otherwise leading whitespace before the opening quote. This
        // matches vim's `:help text-objects` behaviour and avoids leaving
        // a double-space when the quoted span sits mid-sentence.
        let after_close = close + 1; // byte index after closing quote
        if after_close < bytes.len() && bytes[after_close].is_ascii_whitespace() {
            // Eat trailing whitespace run.
            let mut end = after_close;
            while end < bytes.len() && bytes[end].is_ascii_whitespace() {
                end += 1;
            }
            Some(((row, open), (row, end)))
        } else if open > 0 && bytes[open - 1].is_ascii_whitespace() {
            // Eat leading whitespace run.
            let mut start = open;
            while start > 0 && bytes[start - 1].is_ascii_whitespace() {
                start -= 1;
            }
            Some(((row, start), (row, close + 1)))
        } else {
            Some(((row, open), (row, close + 1)))
        }
    }
}

fn bracket_text_object<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    open: char,
    inner: bool,
) -> Option<(Pos, Pos, MotionKind)> {
    let close = match open {
        '(' => ')',
        '[' => ']',
        '{' => '}',
        '<' => '>',
        _ => return None,
    };
    let (row, col) = ed.cursor();
    let lines = buf_lines_to_vec(&ed.buffer);
    let lines = lines.as_slice();
    // Walk backward from cursor to find unbalanced opening. When the
    // cursor isn't inside any pair, fall back to scanning forward for
    // the next opening bracket (targets.vim-style: `ci(` works when
    // cursor is before the `(` on the same line or below).
    let open_pos = find_open_bracket(lines, row, col, open, close)
        .or_else(|| find_next_open(lines, row, col, open))?;
    let close_pos = find_close_bracket(lines, open_pos.0, open_pos.1 + 1, open, close)?;
    // End positions are *exclusive*.
    if inner {
        // Multi-line `iB` / `i{` etc: vim deletes the full lines between
        // the braces (linewise), preserving the `{` and `}` lines
        // themselves and the newlines that directly abut them. E.g.:
        //   {\n    body\n}\n  →  {\n}\n    (cursor on `}` line)
        // Single-line `i{` falls back to charwise exclusive.
        if close_pos.0 > open_pos.0 + 1 {
            // There is at least one line strictly between open and close.
            let inner_row_start = open_pos.0 + 1;
            let inner_row_end = close_pos.0 - 1;
            let end_col = lines
                .get(inner_row_end)
                .map(|l| l.chars().count())
                .unwrap_or(0);
            return Some((
                (inner_row_start, 0),
                (inner_row_end, end_col),
                MotionKind::Linewise,
            ));
        }
        let inner_start = advance_pos(lines, open_pos);
        if inner_start.0 > close_pos.0
            || (inner_start.0 == close_pos.0 && inner_start.1 >= close_pos.1)
        {
            return None;
        }
        Some((inner_start, close_pos, MotionKind::Exclusive))
    } else {
        Some((
            open_pos,
            advance_pos(lines, close_pos),
            MotionKind::Exclusive,
        ))
    }
}

fn find_open_bracket(
    lines: &[String],
    row: usize,
    col: usize,
    open: char,
    close: char,
) -> Option<(usize, usize)> {
    let mut depth: i32 = 0;
    let mut r = row;
    let mut c = col as isize;
    loop {
        let cur = &lines[r];
        let chars: Vec<char> = cur.chars().collect();
        // Clamp `c` to the line length: callers may seed `col` past
        // EOL on virtual-cursor lines (e.g., insert mode after `o`)
        // so direct indexing would panic on empty / short lines.
        if (c as usize) >= chars.len() {
            c = chars.len() as isize - 1;
        }
        while c >= 0 {
            let ch = chars[c as usize];
            if ch == close {
                depth += 1;
            } else if ch == open {
                if depth == 0 {
                    return Some((r, c as usize));
                }
                depth -= 1;
            }
            c -= 1;
        }
        if r == 0 {
            return None;
        }
        r -= 1;
        c = lines[r].chars().count() as isize - 1;
    }
}

fn find_close_bracket(
    lines: &[String],
    row: usize,
    start_col: usize,
    open: char,
    close: char,
) -> Option<(usize, usize)> {
    let mut depth: i32 = 0;
    let mut r = row;
    let mut c = start_col;
    loop {
        let cur = &lines[r];
        let chars: Vec<char> = cur.chars().collect();
        while c < chars.len() {
            let ch = chars[c];
            if ch == open {
                depth += 1;
            } else if ch == close {
                if depth == 0 {
                    return Some((r, c));
                }
                depth -= 1;
            }
            c += 1;
        }
        if r + 1 >= lines.len() {
            return None;
        }
        r += 1;
        c = 0;
    }
}

/// Forward scan from `(row, col)` for the next occurrence of `open`.
/// Multi-line. Used by bracket text objects to support targets.vim-style
/// "search forward when not currently inside a pair" behaviour.
fn find_next_open(lines: &[String], row: usize, col: usize, open: char) -> Option<(usize, usize)> {
    let mut r = row;
    let mut c = col;
    while r < lines.len() {
        let chars: Vec<char> = lines[r].chars().collect();
        while c < chars.len() {
            if chars[c] == open {
                return Some((r, c));
            }
            c += 1;
        }
        r += 1;
        c = 0;
    }
    None
}

fn advance_pos(lines: &[String], pos: (usize, usize)) -> (usize, usize) {
    let (r, c) = pos;
    let line_len = lines[r].chars().count();
    if c < line_len {
        (r, c + 1)
    } else if r + 1 < lines.len() {
        (r + 1, 0)
    } else {
        pos
    }
}

fn paragraph_text_object<H: crate::types::Host>(
    ed: &Editor<hjkl_buffer::Buffer, H>,
    inner: bool,
) -> Option<((usize, usize), (usize, usize))> {
    let (row, _) = ed.cursor();
    let lines = buf_lines_to_vec(&ed.buffer);
    if lines.is_empty() {
        return None;
    }
    // A paragraph is a run of non-blank lines.
    let is_blank = |r: usize| lines.get(r).map(|s| s.trim().is_empty()).unwrap_or(true);
    if is_blank(row) {
        return None;
    }
    let mut top = row;
    while top > 0 && !is_blank(top - 1) {
        top -= 1;
    }
    let mut bot = row;
    while bot + 1 < lines.len() && !is_blank(bot + 1) {
        bot += 1;
    }
    // For `ap`, include one trailing blank line if present.
    if !inner && bot + 1 < lines.len() && is_blank(bot + 1) {
        bot += 1;
    }
    let end_col = lines[bot].chars().count();
    Some(((top, 0), (bot, end_col)))
}

// ─── Individual commands ───────────────────────────────────────────────────

/// Read the text in a vim-shaped range without mutating. Used by
/// `Operator::Yank` so we can pipe the same range translation as
/// [`cut_vim_range`] but skip the delete + inverse extraction.
fn read_vim_range<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    start: (usize, usize),
    end: (usize, usize),
    kind: MotionKind,
) -> String {
    let (top, bot) = order(start, end);
    ed.sync_buffer_content_from_textarea();
    let lines = buf_lines_to_vec(&ed.buffer);
    match kind {
        MotionKind::Linewise => {
            let lo = top.0;
            let hi = bot.0.min(lines.len().saturating_sub(1));
            let mut text = lines[lo..=hi].join("\n");
            text.push('\n');
            text
        }
        MotionKind::Inclusive | MotionKind::Exclusive => {
            let inclusive = matches!(kind, MotionKind::Inclusive);
            // Walk row-by-row collecting chars in `[top, end_exclusive)`.
            let mut out = String::new();
            for row in top.0..=bot.0 {
                let line = lines.get(row).map(String::as_str).unwrap_or("");
                let lo = if row == top.0 { top.1 } else { 0 };
                let hi_unclamped = if row == bot.0 {
                    if inclusive { bot.1 + 1 } else { bot.1 }
                } else {
                    line.chars().count() + 1
                };
                let row_chars: Vec<char> = line.chars().collect();
                let hi = hi_unclamped.min(row_chars.len());
                if lo < hi {
                    out.push_str(&row_chars[lo..hi].iter().collect::<String>());
                }
                if row < bot.0 {
                    out.push('\n');
                }
            }
            out
        }
    }
}

/// Cut a vim-shaped range through the Buffer edit funnel and return
/// the deleted text. Translates vim's `MotionKind`
/// (Linewise/Inclusive/Exclusive) into the buffer's
/// `hjkl_buffer::MotionKind` (Line/Char) and applies the right end-
/// position adjustment so inclusive motions actually include the bot
/// cell. Pushes the cut text into both `last_yank` and the textarea
/// yank buffer (still observed by `p`/`P` until the paste path is
/// ported), and updates `yank_linewise` for linewise cuts.
fn cut_vim_range<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    start: (usize, usize),
    end: (usize, usize),
    kind: MotionKind,
) -> String {
    use hjkl_buffer::{Edit, MotionKind as BufKind, Position};
    let (top, bot) = order(start, end);
    ed.sync_buffer_content_from_textarea();
    let (buf_start, buf_end, buf_kind) = match kind {
        MotionKind::Linewise => (
            Position::new(top.0, 0),
            Position::new(bot.0, 0),
            BufKind::Line,
        ),
        MotionKind::Inclusive => {
            let line_chars = buf_line_chars(&ed.buffer, bot.0);
            // Advance one cell past `bot` so the buffer's exclusive
            // `cut_chars` actually drops the inclusive endpoint. Wrap
            // to the next row when bot already sits on the last char.
            let next = if bot.1 < line_chars {
                Position::new(bot.0, bot.1 + 1)
            } else if bot.0 + 1 < buf_row_count(&ed.buffer) {
                Position::new(bot.0 + 1, 0)
            } else {
                Position::new(bot.0, line_chars)
            };
            (Position::new(top.0, top.1), next, BufKind::Char)
        }
        MotionKind::Exclusive => (
            Position::new(top.0, top.1),
            Position::new(bot.0, bot.1),
            BufKind::Char,
        ),
    };
    let inverse = ed.mutate_edit(Edit::DeleteRange {
        start: buf_start,
        end: buf_end,
        kind: buf_kind,
    });
    let text = match inverse {
        Edit::InsertStr { text, .. } => text,
        _ => String::new(),
    };
    if !text.is_empty() {
        ed.record_yank_to_host(text.clone());
        ed.record_delete(text.clone(), matches!(kind, MotionKind::Linewise));
    }
    ed.push_buffer_cursor_to_textarea();
    text
}

/// `D` / `C` — delete from cursor to end of line through the edit
/// funnel. Mirrors the deleted text into both `ed.last_yank` and the
/// textarea's yank buffer (still observed by `p`/`P` until the paste
/// path is ported). Cursor lands at the deletion start so the caller
/// can decide whether to step it left (`D`) or open insert mode (`C`).
fn delete_to_eol<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    use hjkl_buffer::{Edit, MotionKind, Position};
    ed.sync_buffer_content_from_textarea();
    let cursor = buf_cursor_pos(&ed.buffer);
    let line_chars = buf_line_chars(&ed.buffer, cursor.row);
    if cursor.col >= line_chars {
        return;
    }
    let inverse = ed.mutate_edit(Edit::DeleteRange {
        start: cursor,
        end: Position::new(cursor.row, line_chars),
        kind: MotionKind::Char,
    });
    if let Edit::InsertStr { text, .. } = inverse
        && !text.is_empty()
    {
        ed.record_yank_to_host(text.clone());
        ed.vim.yank_linewise = false;
        ed.set_yank(text);
    }
    buf_set_cursor_pos(&mut ed.buffer, cursor);
    ed.push_buffer_cursor_to_textarea();
}

fn do_char_delete<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    forward: bool,
    count: usize,
) {
    use hjkl_buffer::{Edit, MotionKind, Position};
    ed.push_undo();
    ed.sync_buffer_content_from_textarea();
    // Collect deleted chars so we can write them to the unnamed register
    // (vim's `x`/`X` populate `"` so that `xp` round-trips the char).
    let mut deleted = String::new();
    for _ in 0..count {
        let cursor = buf_cursor_pos(&ed.buffer);
        let line_chars = buf_line_chars(&ed.buffer, cursor.row);
        if forward {
            // `x` — delete the char under the cursor. Vim no-ops on
            // an empty line; the buffer would drop a row otherwise.
            if cursor.col >= line_chars {
                continue;
            }
            let inverse = ed.mutate_edit(Edit::DeleteRange {
                start: cursor,
                end: Position::new(cursor.row, cursor.col + 1),
                kind: MotionKind::Char,
            });
            if let Edit::InsertStr { text, .. } = inverse {
                deleted.push_str(&text);
            }
        } else {
            // `X` — delete the char before the cursor.
            if cursor.col == 0 {
                continue;
            }
            let inverse = ed.mutate_edit(Edit::DeleteRange {
                start: Position::new(cursor.row, cursor.col - 1),
                end: cursor,
                kind: MotionKind::Char,
            });
            if let Edit::InsertStr { text, .. } = inverse {
                // X deletes backwards; prepend so the register text
                // matches reading order (first deleted char first).
                deleted = text + &deleted;
            }
        }
    }
    if !deleted.is_empty() {
        ed.record_yank_to_host(deleted.clone());
        ed.record_delete(deleted, false);
    }
    ed.push_buffer_cursor_to_textarea();
}

/// Vim `Ctrl-a` / `Ctrl-x` — find the next decimal number at or after the
/// cursor on the current line, add `delta`, leave the cursor on the last
/// digit of the result. No-op if the line has no digits to the right.
fn adjust_number<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    delta: i64,
) -> bool {
    use hjkl_buffer::{Edit, MotionKind, Position};
    ed.sync_buffer_content_from_textarea();
    let cursor = buf_cursor_pos(&ed.buffer);
    let row = cursor.row;
    let chars: Vec<char> = match buf_line(&ed.buffer, row) {
        Some(l) => l.chars().collect(),
        None => return false,
    };
    let Some(digit_start) = (cursor.col..chars.len()).find(|&i| chars[i].is_ascii_digit()) else {
        return false;
    };
    let span_start = if digit_start > 0 && chars[digit_start - 1] == '-' {
        digit_start - 1
    } else {
        digit_start
    };
    let mut span_end = digit_start;
    while span_end < chars.len() && chars[span_end].is_ascii_digit() {
        span_end += 1;
    }
    let s: String = chars[span_start..span_end].iter().collect();
    let Ok(n) = s.parse::<i64>() else {
        return false;
    };
    let new_s = n.saturating_add(delta).to_string();

    ed.push_undo();
    let span_start_pos = Position::new(row, span_start);
    let span_end_pos = Position::new(row, span_end);
    ed.mutate_edit(Edit::DeleteRange {
        start: span_start_pos,
        end: span_end_pos,
        kind: MotionKind::Char,
    });
    ed.mutate_edit(Edit::InsertStr {
        at: span_start_pos,
        text: new_s.clone(),
    });
    let new_len = new_s.chars().count();
    buf_set_cursor_rc(&mut ed.buffer, row, span_start + new_len.saturating_sub(1));
    ed.push_buffer_cursor_to_textarea();
    true
}

pub(crate) fn replace_char<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    ch: char,
    count: usize,
) {
    use hjkl_buffer::{Edit, MotionKind, Position};
    ed.push_undo();
    ed.sync_buffer_content_from_textarea();
    for _ in 0..count {
        let cursor = buf_cursor_pos(&ed.buffer);
        let line_chars = buf_line_chars(&ed.buffer, cursor.row);
        if cursor.col >= line_chars {
            break;
        }
        ed.mutate_edit(Edit::DeleteRange {
            start: cursor,
            end: Position::new(cursor.row, cursor.col + 1),
            kind: MotionKind::Char,
        });
        ed.mutate_edit(Edit::InsertChar { at: cursor, ch });
    }
    // Vim leaves the cursor on the last replaced char.
    crate::motions::move_left(&mut ed.buffer, 1);
    ed.push_buffer_cursor_to_textarea();
}

fn toggle_case_at_cursor<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    use hjkl_buffer::{Edit, MotionKind, Position};
    ed.sync_buffer_content_from_textarea();
    let cursor = buf_cursor_pos(&ed.buffer);
    let Some(c) = buf_line(&ed.buffer, cursor.row).and_then(|l| l.chars().nth(cursor.col)) else {
        return;
    };
    let toggled = if c.is_uppercase() {
        c.to_lowercase().next().unwrap_or(c)
    } else {
        c.to_uppercase().next().unwrap_or(c)
    };
    ed.mutate_edit(Edit::DeleteRange {
        start: cursor,
        end: Position::new(cursor.row, cursor.col + 1),
        kind: MotionKind::Char,
    });
    ed.mutate_edit(Edit::InsertChar {
        at: cursor,
        ch: toggled,
    });
}

fn join_line<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    use hjkl_buffer::{Edit, Position};
    ed.sync_buffer_content_from_textarea();
    let row = buf_cursor_pos(&ed.buffer).row;
    if row + 1 >= buf_row_count(&ed.buffer) {
        return;
    }
    let cur_line = buf_line(&ed.buffer, row).unwrap_or("").to_string();
    let next_raw = buf_line(&ed.buffer, row + 1).unwrap_or("").to_string();
    let next_trimmed = next_raw.trim_start();
    let cur_chars = cur_line.chars().count();
    let next_chars = next_raw.chars().count();
    // `J` inserts a single space iff both sides are non-empty after
    // stripping the next line's leading whitespace.
    let separator = if !cur_line.is_empty() && !next_trimmed.is_empty() {
        " "
    } else {
        ""
    };
    let joined = format!("{cur_line}{separator}{next_trimmed}");
    ed.mutate_edit(Edit::Replace {
        start: Position::new(row, 0),
        end: Position::new(row + 1, next_chars),
        with: joined,
    });
    // Vim parks the cursor on the inserted space — or at the join
    // point when no space went in (which is the same column either
    // way, since the space sits exactly at `cur_chars`).
    buf_set_cursor_rc(&mut ed.buffer, row, cur_chars);
    ed.push_buffer_cursor_to_textarea();
}

/// `gJ` — join the next line onto the current one without inserting a
/// separating space or stripping leading whitespace.
fn join_line_raw<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    use hjkl_buffer::Edit;
    ed.sync_buffer_content_from_textarea();
    let row = buf_cursor_pos(&ed.buffer).row;
    if row + 1 >= buf_row_count(&ed.buffer) {
        return;
    }
    let join_col = buf_line_chars(&ed.buffer, row);
    ed.mutate_edit(Edit::JoinLines {
        row,
        count: 1,
        with_space: false,
    });
    // Vim leaves the cursor at the join point (end of original line).
    buf_set_cursor_rc(&mut ed.buffer, row, join_col);
    ed.push_buffer_cursor_to_textarea();
}

fn do_paste<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    before: bool,
    count: usize,
) {
    use hjkl_buffer::{Edit, Position};
    ed.push_undo();
    // Resolve the source register: `"reg` prefix (consumed) or the
    // unnamed register otherwise. Read text + linewise from the
    // selected slot rather than the global `vim.yank_linewise` so
    // pasting from `"0` after a delete still uses the yank's layout.
    let selector = ed.vim.pending_register.take();
    let (yank, linewise) = match selector.and_then(|c| ed.registers().read(c)) {
        Some(slot) => (slot.text.clone(), slot.linewise),
        // Read both fields from the unnamed slot rather than mixing the
        // slot's text with `vim.yank_linewise`. The cached vim flag is
        // per-editor, so a register imported from another editor (e.g.
        // cross-buffer yank/paste) carried the wrong linewise without
        // this — pasting a linewise yank inserted at the char cursor.
        None => {
            let s = &ed.registers().unnamed;
            (s.text.clone(), s.linewise)
        }
    };
    // Vim `:h '[` / `:h ']`: after paste `[` = first inserted char of
    // the final paste, `]` = last inserted char of the final paste.
    // We track (lo, hi) across iterations; the last value wins.
    let mut paste_mark: Option<((usize, usize), (usize, usize))> = None;
    for _ in 0..count {
        ed.sync_buffer_content_from_textarea();
        let yank = yank.clone();
        if yank.is_empty() {
            continue;
        }
        if linewise {
            // Linewise paste: insert payload as fresh row(s) above
            // (`P`) or below (`p`) the cursor's row. Cursor lands on
            // the first non-blank of the first pasted line.
            let text = yank.trim_matches('\n').to_string();
            let row = buf_cursor_pos(&ed.buffer).row;
            let target_row = if before {
                ed.mutate_edit(Edit::InsertStr {
                    at: Position::new(row, 0),
                    text: format!("{text}\n"),
                });
                row
            } else {
                let line_chars = buf_line_chars(&ed.buffer, row);
                ed.mutate_edit(Edit::InsertStr {
                    at: Position::new(row, line_chars),
                    text: format!("\n{text}"),
                });
                row + 1
            };
            buf_set_cursor_rc(&mut ed.buffer, target_row, 0);
            crate::motions::move_first_non_blank(&mut ed.buffer);
            ed.push_buffer_cursor_to_textarea();
            // Linewise: `[` = (target_row, 0), `]` = (bot_row, last_col).
            let payload_lines = text.lines().count().max(1);
            let bot_row = target_row + payload_lines - 1;
            let bot_last_col = buf_line_chars(&ed.buffer, bot_row).saturating_sub(1);
            paste_mark = Some(((target_row, 0), (bot_row, bot_last_col)));
        } else {
            // Charwise paste. `P` inserts at cursor (shifting cell
            // right); `p` inserts after cursor (advance one cell
            // first, clamped to the end of the line).
            let cursor = buf_cursor_pos(&ed.buffer);
            let at = if before {
                cursor
            } else {
                let line_chars = buf_line_chars(&ed.buffer, cursor.row);
                Position::new(cursor.row, (cursor.col + 1).min(line_chars))
            };
            ed.mutate_edit(Edit::InsertStr {
                at,
                text: yank.clone(),
            });
            // Vim parks the cursor on the last char of the pasted
            // text (do_insert_str leaves it one past the end).
            crate::motions::move_left(&mut ed.buffer, 1);
            ed.push_buffer_cursor_to_textarea();
            // Charwise: `[` = insert start, `]` = cursor (last pasted char).
            let lo = (at.row, at.col);
            let hi = ed.cursor();
            paste_mark = Some((lo, hi));
        }
    }
    if let Some((lo, hi)) = paste_mark {
        ed.set_mark('[', lo);
        ed.set_mark(']', hi);
    }
    // Any paste re-anchors the sticky column to the new cursor position.
    ed.sticky_col = Some(buf_cursor_pos(&ed.buffer).col);
}

pub(crate) fn do_undo<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    if let Some((lines, cursor)) = ed.undo_stack.pop() {
        let current = ed.snapshot();
        ed.redo_stack.push(current);
        ed.restore(lines, cursor);
    }
    ed.vim.mode = Mode::Normal;
    // The restored cursor came from a snapshot taken in insert mode
    // (before the insert started) and may be past the last valid
    // normal-mode column. Clamp it now, same as Esc-from-insert does.
    clamp_cursor_to_normal_mode(ed);
}

pub(crate) fn do_redo<H: crate::types::Host>(ed: &mut Editor<hjkl_buffer::Buffer, H>) {
    if let Some((lines, cursor)) = ed.redo_stack.pop() {
        let current = ed.snapshot();
        ed.undo_stack.push(current);
        ed.cap_undo();
        ed.restore(lines, cursor);
    }
    ed.vim.mode = Mode::Normal;
}

// ─── Dot repeat ────────────────────────────────────────────────────────────

/// Replay-side helper: insert `text` at the cursor through the
/// edit funnel, then leave insert mode (the original change ended
/// with Esc, so the dot-repeat must end the same way — including
/// the cursor step-back vim does on Esc-from-insert).
fn replay_insert_and_finish<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    text: &str,
) {
    use hjkl_buffer::{Edit, Position};
    let cursor = ed.cursor();
    ed.mutate_edit(Edit::InsertStr {
        at: Position::new(cursor.0, cursor.1),
        text: text.to_string(),
    });
    if ed.vim.insert_session.take().is_some() {
        if ed.cursor().1 > 0 {
            crate::motions::move_left(&mut ed.buffer, 1);
            ed.push_buffer_cursor_to_textarea();
        }
        ed.vim.mode = Mode::Normal;
    }
}

fn replay_last_change<H: crate::types::Host>(
    ed: &mut Editor<hjkl_buffer::Buffer, H>,
    outer_count: usize,
) {
    let Some(change) = ed.vim.last_change.clone() else {
        return;
    };
    ed.vim.replaying = true;
    let scale = if outer_count > 0 { outer_count } else { 1 };
    match change {
        LastChange::OpMotion {
            op,
            motion,
            count,
            inserted,
        } => {
            let total = count.max(1) * scale;
            apply_op_with_motion(ed, op, &motion, total);
            if let Some(text) = inserted {
                replay_insert_and_finish(ed, &text);
            }
        }
        LastChange::OpTextObj {
            op,
            obj,
            inner,
            inserted,
        } => {
            apply_op_with_text_object(ed, op, obj, inner);
            if let Some(text) = inserted {
                replay_insert_and_finish(ed, &text);
            }
        }
        LastChange::LineOp {
            op,
            count,
            inserted,
        } => {
            let total = count.max(1) * scale;
            execute_line_op(ed, op, total);
            if let Some(text) = inserted {
                replay_insert_and_finish(ed, &text);
            }
        }
        LastChange::CharDel { forward, count } => {
            do_char_delete(ed, forward, count * scale);
        }
        LastChange::ReplaceChar { ch, count } => {
            replace_char(ed, ch, count * scale);
        }
        LastChange::ToggleCase { count } => {
            for _ in 0..count * scale {
                ed.push_undo();
                toggle_case_at_cursor(ed);
            }
        }
        LastChange::JoinLine { count } => {
            for _ in 0..count * scale {
                ed.push_undo();
                join_line(ed);
            }
        }
        LastChange::Paste { before, count } => {
            do_paste(ed, before, count * scale);
        }
        LastChange::DeleteToEol { inserted } => {
            use hjkl_buffer::{Edit, Position};
            ed.push_undo();
            delete_to_eol(ed);
            if let Some(text) = inserted {
                let cursor = ed.cursor();
                ed.mutate_edit(Edit::InsertStr {
                    at: Position::new(cursor.0, cursor.1),
                    text,
                });
            }
        }
        LastChange::OpenLine { above, inserted } => {
            use hjkl_buffer::{Edit, Position};
            ed.push_undo();
            ed.sync_buffer_content_from_textarea();
            let row = buf_cursor_pos(&ed.buffer).row;
            if above {
                ed.mutate_edit(Edit::InsertStr {
                    at: Position::new(row, 0),
                    text: "\n".to_string(),
                });
                let folds = crate::buffer_impl::SnapshotFoldProvider::from_buffer(&ed.buffer);
                crate::motions::move_up(&mut ed.buffer, &folds, 1, &mut ed.sticky_col);
            } else {
                let line_chars = buf_line_chars(&ed.buffer, row);
                ed.mutate_edit(Edit::InsertStr {
                    at: Position::new(row, line_chars),
                    text: "\n".to_string(),
                });
            }
            ed.push_buffer_cursor_to_textarea();
            let cursor = ed.cursor();
            ed.mutate_edit(Edit::InsertStr {
                at: Position::new(cursor.0, cursor.1),
                text: inserted,
            });
        }
        LastChange::InsertAt {
            entry,
            inserted,
            count,
        } => {
            use hjkl_buffer::{Edit, Position};
            ed.push_undo();
            match entry {
                InsertEntry::I => {}
                InsertEntry::ShiftI => move_first_non_whitespace(ed),
                InsertEntry::A => {
                    crate::motions::move_right_to_end(&mut ed.buffer, 1);
                    ed.push_buffer_cursor_to_textarea();
                }
                InsertEntry::ShiftA => {
                    crate::motions::move_line_end(&mut ed.buffer);
                    crate::motions::move_right_to_end(&mut ed.buffer, 1);
                    ed.push_buffer_cursor_to_textarea();
                }
            }
            for _ in 0..count.max(1) {
                let cursor = ed.cursor();
                ed.mutate_edit(Edit::InsertStr {
                    at: Position::new(cursor.0, cursor.1),
                    text: inserted.clone(),
                });
            }
        }
    }
    ed.vim.replaying = false;
}

// ─── Extracting inserted text for replay ───────────────────────────────────

fn extract_inserted(before: &str, after: &str) -> String {
    let before_chars: Vec<char> = before.chars().collect();
    let after_chars: Vec<char> = after.chars().collect();
    if after_chars.len() <= before_chars.len() {
        return String::new();
    }
    let prefix = before_chars
        .iter()
        .zip(after_chars.iter())
        .take_while(|(a, b)| a == b)
        .count();
    let max_suffix = before_chars.len() - prefix;
    let suffix = before_chars
        .iter()
        .rev()
        .zip(after_chars.iter().rev())
        .take(max_suffix)
        .take_while(|(a, b)| a == b)
        .count();
    after_chars[prefix..after_chars.len() - suffix]
        .iter()
        .collect()
}

// ─── Tests ────────────────────────────────────────────────────────────────

#[cfg(all(test, feature = "crossterm"))]
mod tests {
    use crate::VimMode;
    use crate::editor::Editor;
    use crate::types::Host;
    use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};

    fn run_keys<H: crate::types::Host>(e: &mut Editor<hjkl_buffer::Buffer, H>, keys: &str) {
        // Minimal notation:
        //   <Esc> <CR> <BS> <Left/Right/Up/Down> <C-x>
        //   anything else = single char
        let mut iter = keys.chars().peekable();
        while let Some(c) = iter.next() {
            if c == '<' {
                let mut tag = String::new();
                for ch in iter.by_ref() {
                    if ch == '>' {
                        break;
                    }
                    tag.push(ch);
                }
                let ev = match tag.as_str() {
                    "Esc" => KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE),
                    "CR" => KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE),
                    "BS" => KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE),
                    "Space" => KeyEvent::new(KeyCode::Char(' '), KeyModifiers::NONE),
                    "Up" => KeyEvent::new(KeyCode::Up, KeyModifiers::NONE),
                    "Down" => KeyEvent::new(KeyCode::Down, KeyModifiers::NONE),
                    "Left" => KeyEvent::new(KeyCode::Left, KeyModifiers::NONE),
                    "Right" => KeyEvent::new(KeyCode::Right, KeyModifiers::NONE),
                    // Vim-style literal `<` escape so tests can type
                    // the outdent operator without colliding with the
                    // `<tag>` notation this helper uses for special keys.
                    "lt" => KeyEvent::new(KeyCode::Char('<'), KeyModifiers::NONE),
                    s if s.starts_with("C-") => {
                        let ch = s.chars().nth(2).unwrap();
                        KeyEvent::new(KeyCode::Char(ch), KeyModifiers::CONTROL)
                    }
                    _ => continue,
                };
                e.handle_key(ev);
            } else {
                let mods = if c.is_uppercase() {
                    KeyModifiers::SHIFT
                } else {
                    KeyModifiers::NONE
                };
                e.handle_key(KeyEvent::new(KeyCode::Char(c), mods));
            }
        }
    }

    fn editor_with(content: &str) -> Editor {
        // Tests historically assume shiftwidth=2 (sqeel-derived). The 0.1.0
        // SPEC default is shiftwidth=8 (vim-faithful). Keep these tests on
        // the legacy 2-space rhythm so the indent/outdent assertions don't
        // churn.
        let opts = crate::types::Options {
            shiftwidth: 2,
            ..crate::types::Options::default()
        };
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            opts,
        );
        e.set_content(content);
        e
    }

    #[test]
    fn f_char_jumps_on_line() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "fw");
        assert_eq!(e.cursor(), (0, 6));
    }

    #[test]
    fn cap_f_jumps_backward() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 10);
        run_keys(&mut e, "Fo");
        assert_eq!(e.cursor().1, 7);
    }

    #[test]
    fn t_stops_before_char() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "tl");
        assert_eq!(e.cursor(), (0, 1));
    }

    #[test]
    fn semicolon_repeats_find() {
        let mut e = editor_with("aa.bb.cc");
        run_keys(&mut e, "f.");
        assert_eq!(e.cursor().1, 2);
        run_keys(&mut e, ";");
        assert_eq!(e.cursor().1, 5);
    }

    #[test]
    fn comma_repeats_find_reverse() {
        let mut e = editor_with("aa.bb.cc");
        run_keys(&mut e, "f.");
        run_keys(&mut e, ";");
        run_keys(&mut e, ",");
        assert_eq!(e.cursor().1, 2);
    }

    #[test]
    fn di_quote_deletes_content() {
        let mut e = editor_with("foo \"bar\" baz");
        e.jump_cursor(0, 6); // inside quotes
        run_keys(&mut e, "di\"");
        assert_eq!(e.buffer().lines()[0], "foo \"\" baz");
    }

    #[test]
    fn da_quote_deletes_with_quotes() {
        // `da"` eats the trailing space after the closing quote so the
        // result matches vim's "around" text-object whitespace rule.
        let mut e = editor_with("foo \"bar\" baz");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "da\"");
        assert_eq!(e.buffer().lines()[0], "foo baz");
    }

    #[test]
    fn ci_paren_deletes_and_inserts() {
        let mut e = editor_with("fn(a, b, c)");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "ci(");
        assert_eq!(e.vim_mode(), VimMode::Insert);
        assert_eq!(e.buffer().lines()[0], "fn()");
    }

    #[test]
    fn diw_deletes_inner_word() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "diw");
        assert_eq!(e.buffer().lines()[0], " world");
    }

    #[test]
    fn daw_deletes_word_with_trailing_space() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "daw");
        assert_eq!(e.buffer().lines()[0], "world");
    }

    #[test]
    fn percent_jumps_to_matching_bracket() {
        let mut e = editor_with("foo(bar)");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "%");
        assert_eq!(e.cursor().1, 7);
        run_keys(&mut e, "%");
        assert_eq!(e.cursor().1, 3);
    }

    #[test]
    fn dot_repeats_last_change() {
        let mut e = editor_with("aaa bbb ccc");
        run_keys(&mut e, "dw");
        assert_eq!(e.buffer().lines()[0], "bbb ccc");
        run_keys(&mut e, ".");
        assert_eq!(e.buffer().lines()[0], "ccc");
    }

    #[test]
    fn dot_repeats_change_operator_with_text() {
        let mut e = editor_with("foo foo foo");
        run_keys(&mut e, "cwbar<Esc>");
        assert_eq!(e.buffer().lines()[0], "bar foo foo");
        // Move past the space.
        run_keys(&mut e, "w");
        run_keys(&mut e, ".");
        assert_eq!(e.buffer().lines()[0], "bar bar foo");
    }

    #[test]
    fn dot_repeats_x() {
        let mut e = editor_with("abcdef");
        run_keys(&mut e, "x");
        run_keys(&mut e, "..");
        assert_eq!(e.buffer().lines()[0], "def");
    }

    #[test]
    fn count_operator_motion_compose() {
        let mut e = editor_with("one two three four five");
        run_keys(&mut e, "d3w");
        assert_eq!(e.buffer().lines()[0], "four five");
    }

    #[test]
    fn two_dd_deletes_two_lines() {
        let mut e = editor_with("a\nb\nc");
        run_keys(&mut e, "2dd");
        assert_eq!(e.buffer().lines().len(), 1);
        assert_eq!(e.buffer().lines()[0], "c");
    }

    /// Vim's `dd` leaves the cursor on the first non-blank of the line
    /// that now sits at the deleted row — not at the end of the
    /// previous line, which is where tui-textarea's raw cut would
    /// park it.
    #[test]
    fn dd_in_middle_puts_cursor_on_first_non_blank_of_next() {
        let mut e = editor_with("one\ntwo\n    three\nfour");
        e.jump_cursor(1, 2);
        run_keys(&mut e, "dd");
        // Buffer: ["one", "    three", "four"]
        assert_eq!(e.buffer().lines()[1], "    three");
        assert_eq!(e.cursor(), (1, 4));
    }

    #[test]
    fn dd_on_last_line_puts_cursor_on_first_non_blank_of_prev() {
        let mut e = editor_with("one\n  two\nthree");
        e.jump_cursor(2, 0);
        run_keys(&mut e, "dd");
        // Buffer: ["one", "  two"]
        assert_eq!(e.buffer().lines().len(), 2);
        assert_eq!(e.cursor(), (1, 2));
    }

    #[test]
    fn dd_on_only_line_leaves_empty_buffer_and_cursor_at_zero() {
        let mut e = editor_with("lonely");
        run_keys(&mut e, "dd");
        assert_eq!(e.buffer().lines().len(), 1);
        assert_eq!(e.buffer().lines()[0], "");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn count_dd_puts_cursor_on_first_non_blank_of_remaining() {
        let mut e = editor_with("a\nb\nc\n   d\ne");
        // Cursor on row 1, "3dd" deletes b/c/   d → lines become [a, e].
        e.jump_cursor(1, 0);
        run_keys(&mut e, "3dd");
        assert_eq!(e.buffer().lines(), &["a".to_string(), "e".to_string()]);
        assert_eq!(e.cursor(), (1, 0));
    }

    #[test]
    fn dd_then_j_uses_first_non_blank_not_sticky_col() {
        // Buffer: 3 lines with predictable widths.
        // Line 0: "    line one"   (12 chars, first-non-blank at col 4)
        // Line 1: "    line two"   (12 chars, first-non-blank at col 4)
        // Line 2: "  xy"           (4 chars, indices 0-3; last char at col 3)
        //
        // Cursor starts at col 8 on line 0.  After `dd`:
        //   - line 0 is deleted; cursor lands on first-non-blank of new line 0
        //     ("    line two") → col 4.
        //   - sticky_col must be updated to 4.
        //
        // Then `j` moves to "  xy" (4 chars, max col = 3).
        //   - With the fix   : sticky_col=4 → clamps to col 3 (last char).
        //   - Without the fix: sticky_col=8 → clamps to col 3 (same clamp).
        //
        // To make the two cases distinguishable we choose line 2 with
        // exactly 6 chars ("  xyz!") so max col = 5:
        //   - fix   : sticky_col=4 → lands at col 4.
        //   - no fix: sticky_col=8 → clamps to col 5.
        let mut e = editor_with("    line one\n    line two\n  xyz!");
        // Move to col 8 on line 0.
        e.jump_cursor(0, 8);
        assert_eq!(e.cursor(), (0, 8));
        // `dd` deletes line 0; cursor should land on first-non-blank of
        // the new line 0 ("    line two" → col 4).
        run_keys(&mut e, "dd");
        assert_eq!(
            e.cursor(),
            (0, 4),
            "dd must place cursor on first-non-blank"
        );
        // `j` moves to "  xyz!" (6 chars, cols 0-5).
        // Bug: stale sticky_col=8 clamps to col 5 (last char).
        // Fixed: sticky_col=4 → lands at col 4.
        run_keys(&mut e, "j");
        let (row, col) = e.cursor();
        assert_eq!(row, 1);
        assert_eq!(
            col, 4,
            "after dd, j should use the column dd established (4), not pre-dd sticky_col (8)"
        );
    }

    #[test]
    fn gu_lowercases_motion_range() {
        let mut e = editor_with("HELLO WORLD");
        run_keys(&mut e, "guw");
        assert_eq!(e.buffer().lines()[0], "hello WORLD");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn g_u_uppercases_text_object() {
        let mut e = editor_with("hello world");
        // gUiw uppercases the word at the cursor.
        run_keys(&mut e, "gUiw");
        assert_eq!(e.buffer().lines()[0], "HELLO world");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn g_tilde_toggles_case_of_range() {
        let mut e = editor_with("Hello World");
        run_keys(&mut e, "g~iw");
        assert_eq!(e.buffer().lines()[0], "hELLO World");
    }

    #[test]
    fn g_uu_uppercases_current_line() {
        let mut e = editor_with("select 1\nselect 2");
        run_keys(&mut e, "gUU");
        assert_eq!(e.buffer().lines()[0], "SELECT 1");
        assert_eq!(e.buffer().lines()[1], "select 2");
    }

    #[test]
    fn gugu_lowercases_current_line() {
        let mut e = editor_with("FOO BAR\nBAZ");
        run_keys(&mut e, "gugu");
        assert_eq!(e.buffer().lines()[0], "foo bar");
    }

    #[test]
    fn visual_u_uppercases_selection() {
        let mut e = editor_with("hello world");
        // v + e selects "hello" (inclusive of last char), U uppercases.
        run_keys(&mut e, "veU");
        assert_eq!(e.buffer().lines()[0], "HELLO world");
    }

    #[test]
    fn visual_line_u_lowercases_line() {
        let mut e = editor_with("HELLO WORLD\nOTHER");
        run_keys(&mut e, "Vu");
        assert_eq!(e.buffer().lines()[0], "hello world");
        assert_eq!(e.buffer().lines()[1], "OTHER");
    }

    #[test]
    fn g_uu_with_count_uppercases_multiple_lines() {
        let mut e = editor_with("one\ntwo\nthree\nfour");
        // `3gUU` uppercases 3 lines starting from the cursor.
        run_keys(&mut e, "3gUU");
        assert_eq!(e.buffer().lines()[0], "ONE");
        assert_eq!(e.buffer().lines()[1], "TWO");
        assert_eq!(e.buffer().lines()[2], "THREE");
        assert_eq!(e.buffer().lines()[3], "four");
    }

    #[test]
    fn double_gt_indents_current_line() {
        let mut e = editor_with("hello");
        run_keys(&mut e, ">>");
        assert_eq!(e.buffer().lines()[0], "  hello");
        // Cursor lands on first non-blank.
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn double_lt_outdents_current_line() {
        let mut e = editor_with("    hello");
        run_keys(&mut e, "<lt><lt>");
        assert_eq!(e.buffer().lines()[0], "  hello");
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn count_double_gt_indents_multiple_lines() {
        let mut e = editor_with("a\nb\nc\nd");
        // `3>>` indents 3 lines starting at cursor.
        run_keys(&mut e, "3>>");
        assert_eq!(e.buffer().lines()[0], "  a");
        assert_eq!(e.buffer().lines()[1], "  b");
        assert_eq!(e.buffer().lines()[2], "  c");
        assert_eq!(e.buffer().lines()[3], "d");
    }

    #[test]
    fn outdent_clips_ragged_leading_whitespace() {
        // Only one space of indent — outdent should strip what's
        // there, not leave anything negative.
        let mut e = editor_with(" x");
        run_keys(&mut e, "<lt><lt>");
        assert_eq!(e.buffer().lines()[0], "x");
    }

    #[test]
    fn indent_motion_is_always_linewise() {
        // `>w` indents the current line (linewise) — it doesn't
        // insert spaces into the middle of the word.
        let mut e = editor_with("foo bar");
        run_keys(&mut e, ">w");
        assert_eq!(e.buffer().lines()[0], "  foo bar");
    }

    #[test]
    fn indent_text_object_extends_over_paragraph() {
        let mut e = editor_with("a\nb\n\nc\nd");
        // `>ap` indents the whole paragraph (rows 0..=1).
        run_keys(&mut e, ">ap");
        assert_eq!(e.buffer().lines()[0], "  a");
        assert_eq!(e.buffer().lines()[1], "  b");
        assert_eq!(e.buffer().lines()[2], "");
        assert_eq!(e.buffer().lines()[3], "c");
    }

    #[test]
    fn visual_line_indent_shifts_selected_rows() {
        let mut e = editor_with("x\ny\nz");
        // Vj selects rows 0..=1 linewise; `>` indents.
        run_keys(&mut e, "Vj>");
        assert_eq!(e.buffer().lines()[0], "  x");
        assert_eq!(e.buffer().lines()[1], "  y");
        assert_eq!(e.buffer().lines()[2], "z");
    }

    #[test]
    fn outdent_empty_line_is_noop() {
        let mut e = editor_with("\nfoo");
        run_keys(&mut e, "<lt><lt>");
        assert_eq!(e.buffer().lines()[0], "");
    }

    #[test]
    fn indent_skips_empty_lines() {
        // Vim convention: `>>` on an empty line doesn't pad it with
        // trailing whitespace.
        let mut e = editor_with("");
        run_keys(&mut e, ">>");
        assert_eq!(e.buffer().lines()[0], "");
    }

    #[test]
    fn insert_ctrl_t_indents_current_line() {
        let mut e = editor_with("x");
        // Enter insert, Ctrl-t indents the line; cursor advances too.
        run_keys(&mut e, "i<C-t>");
        assert_eq!(e.buffer().lines()[0], "  x");
        // After insert-mode start `i` cursor was at (0, 0); Ctrl-t
        // shifts it by SHIFTWIDTH=2.
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn insert_ctrl_d_outdents_current_line() {
        let mut e = editor_with("    x");
        // Enter insert-at-end `A`, Ctrl-d outdents by shiftwidth.
        run_keys(&mut e, "A<C-d>");
        assert_eq!(e.buffer().lines()[0], "  x");
    }

    #[test]
    fn h_at_col_zero_does_not_wrap_to_prev_line() {
        let mut e = editor_with("first\nsecond");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "h");
        // Cursor must stay on row 1 col 0 — vim default doesn't wrap.
        assert_eq!(e.cursor(), (1, 0));
    }

    #[test]
    fn l_at_last_char_does_not_wrap_to_next_line() {
        let mut e = editor_with("ab\ncd");
        // Move to last char of row 0 (col 1).
        e.jump_cursor(0, 1);
        run_keys(&mut e, "l");
        // Cursor stays on last char — no wrap.
        assert_eq!(e.cursor(), (0, 1));
    }

    #[test]
    fn count_l_clamps_at_line_end() {
        let mut e = editor_with("abcde");
        // 20l starting at col 0 should land on last char (col 4),
        // not overflow / wrap.
        run_keys(&mut e, "20l");
        assert_eq!(e.cursor(), (0, 4));
    }

    #[test]
    fn count_h_clamps_at_col_zero() {
        let mut e = editor_with("abcde");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "20h");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn dl_on_last_char_still_deletes_it() {
        // `dl` / `x`-equivalent at EOL must delete the last char —
        // operator motion allows endpoint past-last even though bare
        // `l` stops before.
        let mut e = editor_with("ab");
        e.jump_cursor(0, 1);
        run_keys(&mut e, "dl");
        assert_eq!(e.buffer().lines()[0], "a");
    }

    #[test]
    fn case_op_preserves_yank_register() {
        let mut e = editor_with("target");
        run_keys(&mut e, "yy");
        let yank_before = e.yank().to_string();
        // gUU changes the line but must not clobber the yank register.
        run_keys(&mut e, "gUU");
        assert_eq!(e.buffer().lines()[0], "TARGET");
        assert_eq!(
            e.yank(),
            yank_before,
            "case ops must preserve the yank buffer"
        );
    }

    #[test]
    fn dap_deletes_paragraph() {
        let mut e = editor_with("a\nb\n\nc\nd");
        run_keys(&mut e, "dap");
        assert_eq!(e.buffer().lines().first().map(String::as_str), Some("c"));
    }

    #[test]
    fn dit_deletes_inner_tag_content() {
        let mut e = editor_with("<b>hello</b>");
        // Cursor on `e`.
        e.jump_cursor(0, 4);
        run_keys(&mut e, "dit");
        assert_eq!(e.buffer().lines()[0], "<b></b>");
    }

    #[test]
    fn dat_deletes_around_tag() {
        let mut e = editor_with("hi <b>foo</b> bye");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "dat");
        assert_eq!(e.buffer().lines()[0], "hi  bye");
    }

    #[test]
    fn dit_picks_innermost_tag() {
        let mut e = editor_with("<a><b>x</b></a>");
        // Cursor on `x`.
        e.jump_cursor(0, 6);
        run_keys(&mut e, "dit");
        // Inner of <b> is removed; <a> wrapping stays.
        assert_eq!(e.buffer().lines()[0], "<a><b></b></a>");
    }

    #[test]
    fn dat_innermost_tag_pair() {
        let mut e = editor_with("<a><b>x</b></a>");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "dat");
        assert_eq!(e.buffer().lines()[0], "<a></a>");
    }

    #[test]
    fn dit_outside_any_tag_no_op() {
        let mut e = editor_with("plain text");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "dit");
        // No tag pair surrounds the cursor — buffer unchanged.
        assert_eq!(e.buffer().lines()[0], "plain text");
    }

    #[test]
    fn cit_changes_inner_tag_content() {
        let mut e = editor_with("<b>hello</b>");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "citNEW<Esc>");
        assert_eq!(e.buffer().lines()[0], "<b>NEW</b>");
    }

    #[test]
    fn cat_changes_around_tag() {
        let mut e = editor_with("hi <b>foo</b> bye");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "catBAR<Esc>");
        assert_eq!(e.buffer().lines()[0], "hi BAR bye");
    }

    #[test]
    fn yit_yanks_inner_tag_content() {
        let mut e = editor_with("<b>hello</b>");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "yit");
        assert_eq!(e.registers().read('"').unwrap().text, "hello");
    }

    #[test]
    fn yat_yanks_full_tag_pair() {
        let mut e = editor_with("hi <b>foo</b> bye");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "yat");
        assert_eq!(e.registers().read('"').unwrap().text, "<b>foo</b>");
    }

    #[test]
    fn vit_visually_selects_inner_tag() {
        let mut e = editor_with("<b>hello</b>");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "vit");
        assert_eq!(e.vim_mode(), VimMode::Visual);
        run_keys(&mut e, "y");
        assert_eq!(e.registers().read('"').unwrap().text, "hello");
    }

    #[test]
    fn vat_visually_selects_around_tag() {
        let mut e = editor_with("x<b>foo</b>y");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "vat");
        assert_eq!(e.vim_mode(), VimMode::Visual);
        run_keys(&mut e, "y");
        assert_eq!(e.registers().read('"').unwrap().text, "<b>foo</b>");
    }

    // ─── Text-object coverage (d operator, inner + around) ───────────

    #[test]
    #[allow(non_snake_case)]
    fn diW_deletes_inner_big_word() {
        let mut e = editor_with("foo.bar baz");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "diW");
        // Big word treats `foo.bar` as one token.
        assert_eq!(e.buffer().lines()[0], " baz");
    }

    #[test]
    #[allow(non_snake_case)]
    fn daW_deletes_around_big_word() {
        let mut e = editor_with("foo.bar baz");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "daW");
        assert_eq!(e.buffer().lines()[0], "baz");
    }

    #[test]
    fn di_double_quote_deletes_inside() {
        let mut e = editor_with("a \"hello\" b");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "di\"");
        assert_eq!(e.buffer().lines()[0], "a \"\" b");
    }

    #[test]
    fn da_double_quote_deletes_around() {
        // `da"` eats the trailing space — matches vim's around-whitespace rule.
        let mut e = editor_with("a \"hello\" b");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "da\"");
        assert_eq!(e.buffer().lines()[0], "a b");
    }

    #[test]
    fn di_single_quote_deletes_inside() {
        let mut e = editor_with("x 'foo' y");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "di'");
        assert_eq!(e.buffer().lines()[0], "x '' y");
    }

    #[test]
    fn da_single_quote_deletes_around() {
        // `da'` eats the trailing space — matches vim's around-whitespace rule.
        let mut e = editor_with("x 'foo' y");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "da'");
        assert_eq!(e.buffer().lines()[0], "x y");
    }

    #[test]
    fn di_backtick_deletes_inside() {
        let mut e = editor_with("p `q` r");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "di`");
        assert_eq!(e.buffer().lines()[0], "p `` r");
    }

    #[test]
    fn da_backtick_deletes_around() {
        // `da`` eats the trailing space — matches vim's around-whitespace rule.
        let mut e = editor_with("p `q` r");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "da`");
        assert_eq!(e.buffer().lines()[0], "p r");
    }

    #[test]
    fn di_paren_deletes_inside() {
        let mut e = editor_with("f(arg)");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "di(");
        assert_eq!(e.buffer().lines()[0], "f()");
    }

    #[test]
    fn di_paren_alias_b_works() {
        let mut e = editor_with("f(arg)");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "dib");
        assert_eq!(e.buffer().lines()[0], "f()");
    }

    #[test]
    fn di_bracket_deletes_inside() {
        let mut e = editor_with("a[b,c]d");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "di[");
        assert_eq!(e.buffer().lines()[0], "a[]d");
    }

    #[test]
    fn da_bracket_deletes_around() {
        let mut e = editor_with("a[b,c]d");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "da[");
        assert_eq!(e.buffer().lines()[0], "ad");
    }

    #[test]
    fn di_brace_deletes_inside() {
        let mut e = editor_with("x{y}z");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "di{");
        assert_eq!(e.buffer().lines()[0], "x{}z");
    }

    #[test]
    fn da_brace_deletes_around() {
        let mut e = editor_with("x{y}z");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "da{");
        assert_eq!(e.buffer().lines()[0], "xz");
    }

    #[test]
    fn di_brace_alias_capital_b_works() {
        let mut e = editor_with("x{y}z");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "diB");
        assert_eq!(e.buffer().lines()[0], "x{}z");
    }

    #[test]
    fn di_angle_deletes_inside() {
        let mut e = editor_with("p<q>r");
        e.jump_cursor(0, 2);
        // `<lt>` so run_keys doesn't treat `<` as the start of a special-key tag.
        run_keys(&mut e, "di<lt>");
        assert_eq!(e.buffer().lines()[0], "p<>r");
    }

    #[test]
    fn da_angle_deletes_around() {
        let mut e = editor_with("p<q>r");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "da<lt>");
        assert_eq!(e.buffer().lines()[0], "pr");
    }

    #[test]
    fn dip_deletes_inner_paragraph() {
        let mut e = editor_with("a\nb\nc\n\nd");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "dip");
        // Inner paragraph (rows 0..=2) drops; the trailing blank
        // separator + remaining paragraph stay.
        assert_eq!(e.buffer().lines(), vec!["".to_string(), "d".into()]);
    }

    // ─── Operator pipeline spot checks (non-tag text objects) ───────

    #[test]
    fn sentence_motion_close_paren_jumps_forward() {
        let mut e = editor_with("Alpha. Beta. Gamma.");
        e.jump_cursor(0, 0);
        run_keys(&mut e, ")");
        // Lands on the start of "Beta".
        assert_eq!(e.cursor(), (0, 7));
        run_keys(&mut e, ")");
        assert_eq!(e.cursor(), (0, 13));
    }

    #[test]
    fn sentence_motion_open_paren_jumps_backward() {
        let mut e = editor_with("Alpha. Beta. Gamma.");
        e.jump_cursor(0, 13);
        run_keys(&mut e, "(");
        // Cursor was at start of "Gamma" (col 13); first `(` walks
        // back to the previous sentence's start.
        assert_eq!(e.cursor(), (0, 7));
        run_keys(&mut e, "(");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn sentence_motion_count() {
        let mut e = editor_with("A. B. C. D.");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "3)");
        // 3 forward jumps land on "D".
        assert_eq!(e.cursor(), (0, 9));
    }

    #[test]
    fn dis_deletes_inner_sentence() {
        let mut e = editor_with("First one. Second one. Third one.");
        e.jump_cursor(0, 13);
        run_keys(&mut e, "dis");
        // Removed "Second one." inclusive of its terminator.
        assert_eq!(e.buffer().lines()[0], "First one.  Third one.");
    }

    #[test]
    fn das_deletes_around_sentence_with_trailing_space() {
        let mut e = editor_with("Alpha. Beta. Gamma.");
        e.jump_cursor(0, 8);
        run_keys(&mut e, "das");
        // `as` swallows the trailing whitespace before the next
        // sentence — exactly one space here.
        assert_eq!(e.buffer().lines()[0], "Alpha. Gamma.");
    }

    #[test]
    fn dis_handles_double_terminator() {
        let mut e = editor_with("Wow!? Next.");
        e.jump_cursor(0, 1);
        run_keys(&mut e, "dis");
        // Run of `!?` collapses into one boundary; sentence body
        // including both terminators is removed.
        assert_eq!(e.buffer().lines()[0], " Next.");
    }

    #[test]
    fn dis_first_sentence_from_cursor_at_zero() {
        let mut e = editor_with("Alpha. Beta.");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "dis");
        assert_eq!(e.buffer().lines()[0], " Beta.");
    }

    #[test]
    fn yis_yanks_inner_sentence() {
        let mut e = editor_with("Hello world. Bye.");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "yis");
        assert_eq!(e.registers().read('"').unwrap().text, "Hello world.");
    }

    #[test]
    fn vis_visually_selects_inner_sentence() {
        let mut e = editor_with("First. Second.");
        e.jump_cursor(0, 1);
        run_keys(&mut e, "vis");
        assert_eq!(e.vim_mode(), VimMode::Visual);
        run_keys(&mut e, "y");
        assert_eq!(e.registers().read('"').unwrap().text, "First.");
    }

    #[test]
    fn ciw_changes_inner_word() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 1);
        run_keys(&mut e, "ciwHEY<Esc>");
        assert_eq!(e.buffer().lines()[0], "HEY world");
    }

    #[test]
    fn yiw_yanks_inner_word() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 1);
        run_keys(&mut e, "yiw");
        assert_eq!(e.registers().read('"').unwrap().text, "hello");
    }

    #[test]
    fn viw_selects_inner_word() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "viw");
        assert_eq!(e.vim_mode(), VimMode::Visual);
        run_keys(&mut e, "y");
        assert_eq!(e.registers().read('"').unwrap().text, "hello");
    }

    #[test]
    fn ci_paren_changes_inside() {
        let mut e = editor_with("f(old)");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "ci(NEW<Esc>");
        assert_eq!(e.buffer().lines()[0], "f(NEW)");
    }

    #[test]
    fn yi_double_quote_yanks_inside() {
        let mut e = editor_with("say \"hi there\" then");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "yi\"");
        assert_eq!(e.registers().read('"').unwrap().text, "hi there");
    }

    #[test]
    fn vap_visual_selects_around_paragraph() {
        let mut e = editor_with("a\nb\n\nc");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "vap");
        assert_eq!(e.vim_mode(), VimMode::VisualLine);
        run_keys(&mut e, "y");
        // Linewise yank includes the paragraph rows + trailing blank.
        let text = e.registers().read('"').unwrap().text.clone();
        assert!(text.starts_with("a\nb"));
    }

    #[test]
    fn star_finds_next_occurrence() {
        let mut e = editor_with("foo bar foo baz");
        run_keys(&mut e, "*");
        assert_eq!(e.cursor().1, 8);
    }

    #[test]
    fn star_skips_substring_match() {
        // `*` uses `\bfoo\b` so `foobar` is *not* a hit; cursor wraps
        // back to the original `foo` at col 0.
        let mut e = editor_with("foo foobar baz");
        run_keys(&mut e, "*");
        assert_eq!(e.cursor().1, 0);
    }

    #[test]
    fn g_star_matches_substring() {
        // `g*` drops the boundary; from `foo` at col 0 the next hit is
        // inside `foobar` (col 4).
        let mut e = editor_with("foo foobar baz");
        run_keys(&mut e, "g*");
        assert_eq!(e.cursor().1, 4);
    }

    #[test]
    fn g_pound_matches_substring_backward() {
        // Start on the last `foo`; `g#` walks backward and lands inside
        // `foobar` (col 4).
        let mut e = editor_with("foo foobar baz foo");
        run_keys(&mut e, "$b");
        assert_eq!(e.cursor().1, 15);
        run_keys(&mut e, "g#");
        assert_eq!(e.cursor().1, 4);
    }

    #[test]
    fn n_repeats_last_search_forward() {
        let mut e = editor_with("foo bar foo baz foo");
        // `/foo<CR>` jumps past the cursor's current cell, so from
        // col 0 the first hit is the second `foo` at col 8.
        run_keys(&mut e, "/foo<CR>");
        assert_eq!(e.cursor().1, 8);
        run_keys(&mut e, "n");
        assert_eq!(e.cursor().1, 16);
    }

    #[test]
    fn shift_n_reverses_search() {
        let mut e = editor_with("foo bar foo baz foo");
        run_keys(&mut e, "/foo<CR>");
        run_keys(&mut e, "n");
        assert_eq!(e.cursor().1, 16);
        run_keys(&mut e, "N");
        assert_eq!(e.cursor().1, 8);
    }

    #[test]
    fn n_noop_without_pattern() {
        let mut e = editor_with("foo bar");
        run_keys(&mut e, "n");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn visual_line_preserves_cursor_column() {
        // V should never drag the cursor off its natural column — the
        // highlight is painted as a post-render overlay instead.
        let mut e = editor_with("hello world\nanother one\nbye");
        run_keys(&mut e, "lllll"); // col 5
        run_keys(&mut e, "V");
        assert_eq!(e.vim_mode(), VimMode::VisualLine);
        assert_eq!(e.cursor(), (0, 5));
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (1, 5));
    }

    #[test]
    fn visual_line_yank_includes_trailing_newline() {
        let mut e = editor_with("aaa\nbbb\nccc");
        run_keys(&mut e, "Vjy");
        // Two lines yanked — must be `aaa\nbbb\n`, trailing newline preserved.
        assert_eq!(e.last_yank.as_deref(), Some("aaa\nbbb\n"));
    }

    #[test]
    fn visual_line_yank_last_line_trailing_newline() {
        let mut e = editor_with("aaa\nbbb\nccc");
        // Move to the last line and yank with V (final buffer line).
        run_keys(&mut e, "jj");
        run_keys(&mut e, "Vy");
        assert_eq!(e.last_yank.as_deref(), Some("ccc\n"));
    }

    #[test]
    fn yy_on_last_line_has_trailing_newline() {
        let mut e = editor_with("aaa\nbbb\nccc");
        run_keys(&mut e, "jj");
        run_keys(&mut e, "yy");
        assert_eq!(e.last_yank.as_deref(), Some("ccc\n"));
    }

    #[test]
    fn yy_in_middle_has_trailing_newline() {
        let mut e = editor_with("aaa\nbbb\nccc");
        run_keys(&mut e, "j");
        run_keys(&mut e, "yy");
        assert_eq!(e.last_yank.as_deref(), Some("bbb\n"));
    }

    #[test]
    fn di_single_quote() {
        let mut e = editor_with("say 'hello world' now");
        e.jump_cursor(0, 7);
        run_keys(&mut e, "di'");
        assert_eq!(e.buffer().lines()[0], "say '' now");
    }

    #[test]
    fn da_single_quote() {
        // `da'` eats the trailing space — matches vim's around-whitespace rule.
        let mut e = editor_with("say 'hello' now");
        e.jump_cursor(0, 7);
        run_keys(&mut e, "da'");
        assert_eq!(e.buffer().lines()[0], "say now");
    }

    #[test]
    fn di_backtick() {
        let mut e = editor_with("say `hi` now");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "di`");
        assert_eq!(e.buffer().lines()[0], "say `` now");
    }

    #[test]
    fn di_brace() {
        let mut e = editor_with("fn { a; b; c }");
        e.jump_cursor(0, 7);
        run_keys(&mut e, "di{");
        assert_eq!(e.buffer().lines()[0], "fn {}");
    }

    #[test]
    fn di_bracket() {
        let mut e = editor_with("arr[1, 2, 3]");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "di[");
        assert_eq!(e.buffer().lines()[0], "arr[]");
    }

    #[test]
    fn dab_deletes_around_paren() {
        let mut e = editor_with("fn(a, b) + 1");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "dab");
        assert_eq!(e.buffer().lines()[0], "fn + 1");
    }

    #[test]
    fn da_big_b_deletes_around_brace() {
        let mut e = editor_with("x = {a: 1}");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "daB");
        assert_eq!(e.buffer().lines()[0], "x = ");
    }

    #[test]
    fn di_big_w_deletes_bigword() {
        let mut e = editor_with("foo-bar baz");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "diW");
        assert_eq!(e.buffer().lines()[0], " baz");
    }

    #[test]
    fn visual_select_inner_word() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 2);
        run_keys(&mut e, "viw");
        assert_eq!(e.vim_mode(), VimMode::Visual);
        run_keys(&mut e, "y");
        assert_eq!(e.last_yank.as_deref(), Some("hello"));
    }

    #[test]
    fn visual_select_inner_quote() {
        let mut e = editor_with("foo \"bar\" baz");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "vi\"");
        run_keys(&mut e, "y");
        assert_eq!(e.last_yank.as_deref(), Some("bar"));
    }

    #[test]
    fn visual_select_inner_paren() {
        let mut e = editor_with("fn(a, b)");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "vi(");
        run_keys(&mut e, "y");
        assert_eq!(e.last_yank.as_deref(), Some("a, b"));
    }

    #[test]
    fn visual_select_outer_brace() {
        let mut e = editor_with("{x}");
        e.jump_cursor(0, 1);
        run_keys(&mut e, "va{");
        run_keys(&mut e, "y");
        assert_eq!(e.last_yank.as_deref(), Some("{x}"));
    }

    #[test]
    fn ci_paren_forward_scans_when_cursor_before_pair() {
        // targets.vim-style: cursor at start of `foo`, ci( jumps to next
        // `(...)` pair on the same line and replaces the contents.
        let mut e = editor_with("foo(bar)");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "ci(NEW<Esc>");
        assert_eq!(e.buffer().lines()[0], "foo(NEW)");
    }

    #[test]
    fn ci_paren_forward_scans_across_lines() {
        let mut e = editor_with("first\nfoo(bar)\nlast");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "ci(NEW<Esc>");
        assert_eq!(e.buffer().lines()[1], "foo(NEW)");
    }

    #[test]
    fn ci_brace_forward_scans_when_cursor_before_pair() {
        let mut e = editor_with("let x = {y};");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "ci{NEW<Esc>");
        assert_eq!(e.buffer().lines()[0], "let x = {NEW};");
    }

    #[test]
    fn cit_forward_scans_when_cursor_before_tag() {
        // Cursor at column 0 (before `<b>`), cit jumps into the next tag
        // pair and replaces its contents.
        let mut e = editor_with("text <b>hello</b> rest");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "citNEW<Esc>");
        assert_eq!(e.buffer().lines()[0], "text <b>NEW</b> rest");
    }

    #[test]
    fn dat_forward_scans_when_cursor_before_tag() {
        // dat = delete around tag — including the `<b>...</b>` markup.
        let mut e = editor_with("text <b>hello</b> rest");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "dat");
        assert_eq!(e.buffer().lines()[0], "text  rest");
    }

    #[test]
    fn ci_paren_still_works_when_cursor_inside() {
        // Regression: forward-scan fallback must not break the
        // canonical "cursor inside the pair" case.
        let mut e = editor_with("fn(a, b)");
        e.jump_cursor(0, 4);
        run_keys(&mut e, "ci(NEW<Esc>");
        assert_eq!(e.buffer().lines()[0], "fn(NEW)");
    }

    #[test]
    fn caw_changes_word_with_trailing_space() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "cawfoo<Esc>");
        assert_eq!(e.buffer().lines()[0], "fooworld");
    }

    #[test]
    fn visual_char_yank_preserves_raw_text() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "vllly");
        assert_eq!(e.last_yank.as_deref(), Some("hell"));
    }

    #[test]
    fn single_line_visual_line_selects_full_line_on_yank() {
        let mut e = editor_with("hello world\nbye");
        run_keys(&mut e, "V");
        // Yank the selection — should include the full line + trailing
        // newline (linewise yank convention).
        run_keys(&mut e, "y");
        assert_eq!(e.last_yank.as_deref(), Some("hello world\n"));
    }

    #[test]
    fn visual_line_extends_both_directions() {
        let mut e = editor_with("aaa\nbbb\nccc\nddd");
        run_keys(&mut e, "jjj"); // row 3, col 0
        run_keys(&mut e, "V");
        assert_eq!(e.cursor(), (3, 0));
        run_keys(&mut e, "k");
        // Cursor is free to sit on its natural column — no forced Jump.
        assert_eq!(e.cursor(), (2, 0));
        run_keys(&mut e, "k");
        assert_eq!(e.cursor(), (1, 0));
    }

    #[test]
    fn visual_char_preserves_cursor_column() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "lllll"); // col 5
        run_keys(&mut e, "v");
        assert_eq!(e.cursor(), (0, 5));
        run_keys(&mut e, "ll");
        assert_eq!(e.cursor(), (0, 7));
    }

    #[test]
    fn visual_char_highlight_bounds_order() {
        let mut e = editor_with("abcdef");
        run_keys(&mut e, "lll"); // col 3
        run_keys(&mut e, "v");
        run_keys(&mut e, "hh"); // col 1
        // Anchor (0, 3), cursor (0, 1). Bounds ordered: start=(0,1) end=(0,3).
        assert_eq!(e.char_highlight(), Some(((0, 1), (0, 3))));
    }

    #[test]
    fn visual_line_highlight_bounds() {
        let mut e = editor_with("a\nb\nc");
        run_keys(&mut e, "V");
        assert_eq!(e.line_highlight(), Some((0, 0)));
        run_keys(&mut e, "j");
        assert_eq!(e.line_highlight(), Some((0, 1)));
        run_keys(&mut e, "j");
        assert_eq!(e.line_highlight(), Some((0, 2)));
    }

    // ─── Basic motions ─────────────────────────────────────────────────────

    #[test]
    fn h_moves_left() {
        let mut e = editor_with("hello");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "h");
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn l_moves_right() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "l");
        assert_eq!(e.cursor(), (0, 1));
    }

    #[test]
    fn k_moves_up() {
        let mut e = editor_with("a\nb\nc");
        e.jump_cursor(2, 0);
        run_keys(&mut e, "k");
        assert_eq!(e.cursor(), (1, 0));
    }

    #[test]
    fn zero_moves_to_line_start() {
        let mut e = editor_with("    hello");
        run_keys(&mut e, "$");
        run_keys(&mut e, "0");
        assert_eq!(e.cursor().1, 0);
    }

    #[test]
    fn caret_moves_to_first_non_blank() {
        let mut e = editor_with("    hello");
        run_keys(&mut e, "0");
        run_keys(&mut e, "^");
        assert_eq!(e.cursor().1, 4);
    }

    #[test]
    fn dollar_moves_to_last_char() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "$");
        assert_eq!(e.cursor().1, 4);
    }

    #[test]
    fn dollar_on_empty_line_stays_at_col_zero() {
        let mut e = editor_with("");
        run_keys(&mut e, "$");
        assert_eq!(e.cursor().1, 0);
    }

    #[test]
    fn w_jumps_to_next_word() {
        let mut e = editor_with("foo bar baz");
        run_keys(&mut e, "w");
        assert_eq!(e.cursor().1, 4);
    }

    #[test]
    fn b_jumps_back_a_word() {
        let mut e = editor_with("foo bar");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "b");
        assert_eq!(e.cursor().1, 4);
    }

    #[test]
    fn e_jumps_to_word_end() {
        let mut e = editor_with("foo bar");
        run_keys(&mut e, "e");
        assert_eq!(e.cursor().1, 2);
    }

    // ─── Operators with line-edge and file-edge motions ───────────────────

    #[test]
    fn d_dollar_deletes_to_eol() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "d$");
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn d_zero_deletes_to_line_start() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "d0");
        assert_eq!(e.buffer().lines()[0], "world");
    }

    #[test]
    fn d_caret_deletes_to_first_non_blank() {
        let mut e = editor_with("    hello");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "d^");
        assert_eq!(e.buffer().lines()[0], "    llo");
    }

    #[test]
    fn d_capital_g_deletes_to_end_of_file() {
        let mut e = editor_with("a\nb\nc\nd");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "dG");
        assert_eq!(e.buffer().lines(), &["a".to_string()]);
    }

    #[test]
    fn d_gg_deletes_to_start_of_file() {
        let mut e = editor_with("a\nb\nc\nd");
        e.jump_cursor(2, 0);
        run_keys(&mut e, "dgg");
        assert_eq!(e.buffer().lines(), &["d".to_string()]);
    }

    #[test]
    fn cw_is_ce_quirk() {
        // `cw` on a non-blank word must NOT eat the trailing whitespace;
        // it behaves like `ce` so the replacement lands before the space.
        let mut e = editor_with("foo bar");
        run_keys(&mut e, "cwxyz<Esc>");
        assert_eq!(e.buffer().lines()[0], "xyz bar");
    }

    // ─── Single-char edits ────────────────────────────────────────────────

    #[test]
    fn big_d_deletes_to_eol() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "D");
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn big_c_deletes_to_eol_and_inserts() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "C!<Esc>");
        assert_eq!(e.buffer().lines()[0], "hello!");
    }

    #[test]
    fn j_joins_next_line_with_space() {
        let mut e = editor_with("hello\nworld");
        run_keys(&mut e, "J");
        assert_eq!(e.buffer().lines(), &["hello world".to_string()]);
    }

    #[test]
    fn j_strips_leading_whitespace_on_join() {
        let mut e = editor_with("hello\n    world");
        run_keys(&mut e, "J");
        assert_eq!(e.buffer().lines(), &["hello world".to_string()]);
    }

    #[test]
    fn big_x_deletes_char_before_cursor() {
        let mut e = editor_with("hello");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "X");
        assert_eq!(e.buffer().lines()[0], "helo");
    }

    #[test]
    fn s_substitutes_char_and_enters_insert() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "sX<Esc>");
        assert_eq!(e.buffer().lines()[0], "Xello");
    }

    #[test]
    fn count_x_deletes_many() {
        let mut e = editor_with("abcdef");
        run_keys(&mut e, "3x");
        assert_eq!(e.buffer().lines()[0], "def");
    }

    // ─── Paste ────────────────────────────────────────────────────────────

    #[test]
    fn p_pastes_charwise_after_cursor() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "yw");
        run_keys(&mut e, "$p");
        assert_eq!(e.buffer().lines()[0], "hellohello");
    }

    #[test]
    fn capital_p_pastes_charwise_before_cursor() {
        let mut e = editor_with("hello");
        // Yank "he" (2 chars) then paste it before the cursor.
        run_keys(&mut e, "v");
        run_keys(&mut e, "l");
        run_keys(&mut e, "y");
        run_keys(&mut e, "$P");
        // After yank cursor is at 0; $ goes to end (col 4), P pastes
        // before cursor — "hell" + "he" + "o" = "hellheo".
        assert_eq!(e.buffer().lines()[0], "hellheo");
    }

    #[test]
    fn p_pastes_linewise_below() {
        let mut e = editor_with("one\ntwo\nthree");
        run_keys(&mut e, "yy");
        run_keys(&mut e, "p");
        assert_eq!(
            e.buffer().lines(),
            &[
                "one".to_string(),
                "one".to_string(),
                "two".to_string(),
                "three".to_string()
            ]
        );
    }

    #[test]
    fn capital_p_pastes_linewise_above() {
        let mut e = editor_with("one\ntwo");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "yy");
        run_keys(&mut e, "P");
        assert_eq!(
            e.buffer().lines(),
            &["one".to_string(), "two".to_string(), "two".to_string()]
        );
    }

    // ─── Reverse word search ──────────────────────────────────────────────

    #[test]
    fn hash_finds_previous_occurrence() {
        let mut e = editor_with("foo bar foo baz foo");
        // Move to the third 'foo' then #.
        e.jump_cursor(0, 16);
        run_keys(&mut e, "#");
        assert_eq!(e.cursor().1, 8);
    }

    // ─── VisualLine delete / change ───────────────────────────────────────

    #[test]
    fn visual_line_delete_removes_full_lines() {
        let mut e = editor_with("a\nb\nc\nd");
        run_keys(&mut e, "Vjd");
        assert_eq!(e.buffer().lines(), &["c".to_string(), "d".to_string()]);
    }

    #[test]
    fn visual_line_change_leaves_blank_line() {
        let mut e = editor_with("a\nb\nc");
        run_keys(&mut e, "Vjc");
        assert_eq!(e.vim_mode(), VimMode::Insert);
        run_keys(&mut e, "X<Esc>");
        // `Vjc` wipes rows 0-1's contents and leaves a blank line in
        // their place (vim convention). Typing `X` lands on that blank
        // first line.
        assert_eq!(e.buffer().lines(), &["X".to_string(), "c".to_string()]);
    }

    #[test]
    fn cc_leaves_blank_line() {
        let mut e = editor_with("a\nb\nc");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "ccX<Esc>");
        assert_eq!(
            e.buffer().lines(),
            &["a".to_string(), "X".to_string(), "c".to_string()]
        );
    }

    // ─── Scrolling ────────────────────────────────────────────────────────

    // ─── WORD motions (W/B/E) ─────────────────────────────────────────────

    #[test]
    fn big_w_skips_hyphens() {
        // `w` stops at `-`; `W` treats the whole `foo-bar` as one WORD.
        let mut e = editor_with("foo-bar baz");
        run_keys(&mut e, "W");
        assert_eq!(e.cursor().1, 8);
    }

    #[test]
    fn big_w_crosses_lines() {
        let mut e = editor_with("foo-bar\nbaz-qux");
        run_keys(&mut e, "W");
        assert_eq!(e.cursor(), (1, 0));
    }

    #[test]
    fn big_b_skips_hyphens() {
        let mut e = editor_with("foo-bar baz");
        e.jump_cursor(0, 9);
        run_keys(&mut e, "B");
        assert_eq!(e.cursor().1, 8);
        run_keys(&mut e, "B");
        assert_eq!(e.cursor().1, 0);
    }

    #[test]
    fn big_e_jumps_to_big_word_end() {
        let mut e = editor_with("foo-bar baz");
        run_keys(&mut e, "E");
        assert_eq!(e.cursor().1, 6);
        run_keys(&mut e, "E");
        assert_eq!(e.cursor().1, 10);
    }

    #[test]
    fn dw_with_big_word_variant() {
        // `dW` uses the WORD motion, so `foo-bar` deletes as a unit.
        let mut e = editor_with("foo-bar baz");
        run_keys(&mut e, "dW");
        assert_eq!(e.buffer().lines()[0], "baz");
    }

    // ─── Insert-mode Ctrl shortcuts ──────────────────────────────────────

    #[test]
    fn insert_ctrl_w_deletes_word_back() {
        let mut e = editor_with("");
        run_keys(&mut e, "i");
        for c in "hello world".chars() {
            e.handle_key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        run_keys(&mut e, "<C-w>");
        assert_eq!(e.buffer().lines()[0], "hello ");
    }

    #[test]
    fn insert_ctrl_w_at_col0_joins_with_prev_word() {
        // Vim with default `backspace=indent,eol,start`: Ctrl-W at the
        // start of a row joins to the previous line and deletes the
        // word now before the cursor.
        let mut e = editor_with("hello\nworld");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "i");
        e.handle_key(KeyEvent::new(KeyCode::Char('w'), KeyModifiers::CONTROL));
        // "hello" was the only word on row 0; it gets deleted, leaving
        // "world" on a single line.
        assert_eq!(e.buffer().lines(), vec!["world".to_string()]);
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn insert_ctrl_w_at_col0_keeps_prefix_words() {
        let mut e = editor_with("foo bar\nbaz");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "i");
        e.handle_key(KeyEvent::new(KeyCode::Char('w'), KeyModifiers::CONTROL));
        // Joins lines, then deletes the trailing "bar" of the prev line.
        assert_eq!(e.buffer().lines(), vec!["foo baz".to_string()]);
        assert_eq!(e.cursor(), (0, 4));
    }

    #[test]
    fn insert_ctrl_u_deletes_to_line_start() {
        let mut e = editor_with("");
        run_keys(&mut e, "i");
        for c in "hello world".chars() {
            e.handle_key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        run_keys(&mut e, "<C-u>");
        assert_eq!(e.buffer().lines()[0], "");
    }

    #[test]
    fn insert_ctrl_o_runs_one_normal_command() {
        let mut e = editor_with("hello world");
        // Enter insert, then Ctrl-o dw (delete a word while in insert).
        run_keys(&mut e, "A");
        assert_eq!(e.vim_mode(), VimMode::Insert);
        // Move cursor back to start of "hello" for the Ctrl-o dw.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.vim_mode(), VimMode::Normal);
        run_keys(&mut e, "dw");
        // After the command completes, back in insert.
        assert_eq!(e.vim_mode(), VimMode::Insert);
        assert_eq!(e.buffer().lines()[0], "world");
    }

    // ─── Sticky column across vertical motion ────────────────────────────

    #[test]
    fn j_through_empty_line_preserves_column() {
        let mut e = editor_with("hello world\n\nanother line");
        // Park cursor at col 6 on row 0.
        run_keys(&mut e, "llllll");
        assert_eq!(e.cursor(), (0, 6));
        // j into the empty line — cursor clamps to (1, 0) visually, but
        // sticky col stays at 6.
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (1, 0));
        // j onto a longer row — sticky col restores us to col 6.
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (2, 6));
    }

    #[test]
    fn j_through_shorter_line_preserves_column() {
        let mut e = editor_with("hello world\nhi\nanother line");
        run_keys(&mut e, "lllllll"); // col 7
        run_keys(&mut e, "j"); // short line — clamps to col 1
        assert_eq!(e.cursor(), (1, 1));
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (2, 7));
    }

    #[test]
    fn esc_from_insert_sticky_matches_visible_cursor() {
        // Cursor at col 12, I (moves to col 4), type "X" (col 5), Esc
        // backs to col 4 — sticky must mirror that visible col so j
        // lands at col 4 of the next row, not col 5 or col 12.
        let mut e = editor_with("    this is a line\n    another one of a similar size");
        e.jump_cursor(0, 12);
        run_keys(&mut e, "I");
        assert_eq!(e.cursor(), (0, 4));
        run_keys(&mut e, "X<Esc>");
        assert_eq!(e.cursor(), (0, 4));
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (1, 4));
    }

    #[test]
    fn esc_from_insert_sticky_tracks_inserted_chars() {
        let mut e = editor_with("xxxxxxx\nyyyyyyy");
        run_keys(&mut e, "i");
        run_keys(&mut e, "abc<Esc>");
        assert_eq!(e.cursor(), (0, 2));
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (1, 2));
    }

    #[test]
    fn esc_from_insert_sticky_tracks_arrow_nav() {
        let mut e = editor_with("xxxxxx\nyyyyyy");
        run_keys(&mut e, "i");
        run_keys(&mut e, "abc");
        for _ in 0..2 {
            e.handle_key(KeyEvent::new(KeyCode::Left, KeyModifiers::NONE));
        }
        run_keys(&mut e, "<Esc>");
        assert_eq!(e.cursor(), (0, 0));
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (1, 0));
    }

    #[test]
    fn esc_from_insert_at_col_14_followed_by_j() {
        // User-reported regression: cursor at col 14, i, type "test "
        // (5 chars → col 19), Esc → col 18. j must land at col 18.
        let line = "x".repeat(30);
        let buf = format!("{line}\n{line}");
        let mut e = editor_with(&buf);
        e.jump_cursor(0, 14);
        run_keys(&mut e, "i");
        for c in "test ".chars() {
            e.handle_key(KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE));
        }
        run_keys(&mut e, "<Esc>");
        assert_eq!(e.cursor(), (0, 18));
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (1, 18));
    }

    #[test]
    fn linewise_paste_resets_sticky_column() {
        // yy then p lands the cursor on the first non-blank of the
        // pasted line; the next j must not drag back to the old
        // sticky column.
        let mut e = editor_with("    hello\naaaaaaaa\nbye");
        run_keys(&mut e, "llllll"); // col 6, sticky = 6
        run_keys(&mut e, "yy");
        run_keys(&mut e, "j"); // into row 1 col 6
        run_keys(&mut e, "p"); // paste below row 1 — cursor on "    hello"
        // Cursor should be at (2, 4) — first non-blank of the pasted line.
        assert_eq!(e.cursor(), (2, 4));
        // j should then preserve col 4, not jump back to 6.
        run_keys(&mut e, "j");
        assert_eq!(e.cursor(), (3, 2));
    }

    #[test]
    fn horizontal_motion_resyncs_sticky_column() {
        // Starting col 6 on row 0, go back to col 3, then down through
        // an empty row. The sticky col should be 3 (from the last `h`
        // sequence), not 6.
        let mut e = editor_with("hello world\n\nanother line");
        run_keys(&mut e, "llllll"); // col 6
        run_keys(&mut e, "hhh"); // col 3
        run_keys(&mut e, "jj");
        assert_eq!(e.cursor(), (2, 3));
    }

    // ─── Visual block ────────────────────────────────────────────────────

    #[test]
    fn ctrl_v_enters_visual_block() {
        let mut e = editor_with("aaa\nbbb\nccc");
        run_keys(&mut e, "<C-v>");
        assert_eq!(e.vim_mode(), VimMode::VisualBlock);
    }

    #[test]
    fn visual_block_esc_returns_to_normal() {
        let mut e = editor_with("aaa\nbbb\nccc");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "<Esc>");
        assert_eq!(e.vim_mode(), VimMode::Normal);
    }

    #[test]
    fn backtick_lt_jumps_to_visual_start_mark() {
        // `` `< `` jumps the cursor to the start of the last visual selection.
        // Regression: pre-0.5.7, handle_goto_mark didn't recognise `<` / `>`
        // as targets even though set_mark stored them correctly.
        let mut e = editor_with("foo bar baz\n");
        run_keys(&mut e, "v");
        run_keys(&mut e, "w"); // cursor advances to col 4
        run_keys(&mut e, "<Esc>"); // sets `<` = (0,0), `>` = (0,4)
        assert_eq!(e.cursor(), (0, 4));
        // `<lt>` is the helper's literal-`<` escape (see run_keys docstring).
        run_keys(&mut e, "`<lt>");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn backtick_gt_jumps_to_visual_end_mark() {
        let mut e = editor_with("foo bar baz\n");
        run_keys(&mut e, "v");
        run_keys(&mut e, "w"); // cursor at col 4
        run_keys(&mut e, "<Esc>");
        run_keys(&mut e, "0"); // cursor at col 0
        run_keys(&mut e, "`>");
        assert_eq!(e.cursor(), (0, 4));
    }

    #[test]
    fn visual_exit_sets_lt_gt_marks() {
        // Vim sets `<` to the start and `>` to the end of the last visual
        // selection on every visual exit. Required for :'<,'> ex ranges.
        let mut e = editor_with("aaa\nbbb\nccc\nddd");
        // V<j><Esc> → selects rows 0..=1 in line-wise visual.
        run_keys(&mut e, "V");
        run_keys(&mut e, "j");
        run_keys(&mut e, "<Esc>");
        let lt = e.mark('<').expect("'<' mark must be set on visual exit");
        let gt = e.mark('>').expect("'>' mark must be set on visual exit");
        assert_eq!(lt.0, 0, "'< row should be the lower bound");
        assert_eq!(gt.0, 1, "'> row should be the upper bound");
    }

    #[test]
    fn visual_exit_marks_use_lower_higher_order() {
        // Selecting upward (cursor < anchor) must still produce `<` = lower,
        // `>` = higher — vim's marks are position-ordered, not selection-
        // ordered.
        let mut e = editor_with("aaa\nbbb\nccc\nddd");
        run_keys(&mut e, "jjj"); // cursor at row 3
        run_keys(&mut e, "V");
        run_keys(&mut e, "k"); // anchor row 3, cursor row 2
        run_keys(&mut e, "<Esc>");
        let lt = e.mark('<').unwrap();
        let gt = e.mark('>').unwrap();
        assert_eq!(lt.0, 2);
        assert_eq!(gt.0, 3);
    }

    #[test]
    fn visualline_exit_marks_snap_to_line_edges() {
        // VisualLine: `<` snaps to col 0, `>` snaps to last col of bot row.
        let mut e = editor_with("aaaaa\nbbbbb\ncc");
        run_keys(&mut e, "lll"); // cursor at row 0, col 3
        run_keys(&mut e, "V");
        run_keys(&mut e, "j"); // VisualLine over rows 0..=1
        run_keys(&mut e, "<Esc>");
        let lt = e.mark('<').unwrap();
        let gt = e.mark('>').unwrap();
        assert_eq!(lt, (0, 0), "'< should snap to (top_row, 0)");
        // Row 1 is "bbbbb" — last col is 4.
        assert_eq!(gt, (1, 4), "'> should snap to (bot_row, last_col)");
    }

    #[test]
    fn visualblock_exit_marks_use_block_corners() {
        // VisualBlock with cursor moving left + down. Corners are not
        // tuple-ordered: top-left is (anchor_row, cursor_col), bottom-right
        // is (cursor_row, anchor_col). `<` must be top-left, `>` bottom-right.
        let mut e = editor_with("aaaaa\nbbbbb\nccccc");
        run_keys(&mut e, "llll"); // row 0, col 4
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "j"); // row 1, col 4
        run_keys(&mut e, "hh"); // row 1, col 2
        run_keys(&mut e, "<Esc>");
        let lt = e.mark('<').unwrap();
        let gt = e.mark('>').unwrap();
        // anchor=(0,4), cursor=(1,2) → corners are (0,2) and (1,4).
        assert_eq!(lt, (0, 2), "'< should be top-left corner");
        assert_eq!(gt, (1, 4), "'> should be bottom-right corner");
    }

    #[test]
    fn visual_block_delete_removes_column_range() {
        let mut e = editor_with("hello\nworld\nhappy");
        // Move off col 0 first so the block starts mid-row.
        run_keys(&mut e, "l");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jj");
        run_keys(&mut e, "ll");
        run_keys(&mut e, "d");
        // Deletes cols 1-3 on every row — "ell" / "orl" / "app".
        assert_eq!(
            e.buffer().lines(),
            &["ho".to_string(), "wd".to_string(), "hy".to_string()]
        );
    }

    #[test]
    fn visual_block_yank_joins_with_newlines() {
        let mut e = editor_with("hello\nworld\nhappy");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jj");
        run_keys(&mut e, "ll");
        run_keys(&mut e, "y");
        assert_eq!(e.last_yank.as_deref(), Some("hel\nwor\nhap"));
    }

    #[test]
    fn visual_block_replace_fills_block() {
        let mut e = editor_with("hello\nworld\nhappy");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jj");
        run_keys(&mut e, "ll");
        run_keys(&mut e, "rx");
        assert_eq!(
            e.buffer().lines(),
            &[
                "xxxlo".to_string(),
                "xxxld".to_string(),
                "xxxpy".to_string()
            ]
        );
    }

    #[test]
    fn visual_block_insert_repeats_across_rows() {
        let mut e = editor_with("hello\nworld\nhappy");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jj");
        run_keys(&mut e, "I");
        run_keys(&mut e, "# <Esc>");
        assert_eq!(
            e.buffer().lines(),
            &[
                "# hello".to_string(),
                "# world".to_string(),
                "# happy".to_string()
            ]
        );
    }

    #[test]
    fn block_highlight_returns_none_outside_block_mode() {
        let mut e = editor_with("abc");
        assert!(e.block_highlight().is_none());
        run_keys(&mut e, "v");
        assert!(e.block_highlight().is_none());
        run_keys(&mut e, "<Esc>V");
        assert!(e.block_highlight().is_none());
    }

    #[test]
    fn block_highlight_bounds_track_anchor_and_cursor() {
        let mut e = editor_with("aaaa\nbbbb\ncccc");
        run_keys(&mut e, "ll"); // cursor (0, 2)
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jh"); // cursor (1, 1)
        // anchor = (0, 2), cursor = (1, 1) → top=0 bot=1 left=1 right=2.
        assert_eq!(e.block_highlight(), Some((0, 1, 1, 2)));
    }

    #[test]
    fn visual_block_delete_handles_short_lines() {
        // Middle row is shorter than the block's right column.
        let mut e = editor_with("hello\nhi\nworld");
        run_keys(&mut e, "l"); // col 1
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jjll"); // cursor (2, 3)
        run_keys(&mut e, "d");
        // Row 0: delete cols 1-3 ("ell") → "ho".
        // Row 1: only 2 chars ("hi"); block starts at col 1, so just "i"
        //        gets removed → "h".
        // Row 2: delete cols 1-3 ("orl") → "wd".
        assert_eq!(
            e.buffer().lines(),
            &["ho".to_string(), "h".to_string(), "wd".to_string()]
        );
    }

    #[test]
    fn visual_block_yank_pads_short_lines_with_empties() {
        let mut e = editor_with("hello\nhi\nworld");
        run_keys(&mut e, "l");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jjll");
        run_keys(&mut e, "y");
        // Row 0 chars 1-3 = "ell"; row 1 chars 1- (only "i"); row 2 "orl".
        assert_eq!(e.last_yank.as_deref(), Some("ell\ni\norl"));
    }

    #[test]
    fn visual_block_replace_skips_past_eol() {
        // Block extends past the end of every row in column range;
        // replace should leave lines shorter than `left` untouched.
        let mut e = editor_with("ab\ncd\nef");
        // Put cursor at col 1 (last char), extend block 5 columns right.
        run_keys(&mut e, "l");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jjllllll");
        run_keys(&mut e, "rX");
        // Every row had only col 0..=1; block covers col 1..=7 → only
        // col 1 is in range on each row, so just that cell changes.
        assert_eq!(
            e.buffer().lines(),
            &["aX".to_string(), "cX".to_string(), "eX".to_string()]
        );
    }

    #[test]
    fn visual_block_with_empty_line_in_middle() {
        let mut e = editor_with("abcd\n\nefgh");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jjll"); // cursor (2, 2)
        run_keys(&mut e, "d");
        // Row 0 cols 0-2 removed → "d". Row 1 empty → untouched.
        // Row 2 cols 0-2 removed → "h".
        assert_eq!(
            e.buffer().lines(),
            &["d".to_string(), "".to_string(), "h".to_string()]
        );
    }

    #[test]
    fn block_insert_pads_empty_lines_to_block_column() {
        // Middle line is empty; block I at column 3 should pad the empty
        // line with spaces so the inserted text lines up.
        let mut e = editor_with("this is a line\n\nthis is a line");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jj");
        run_keys(&mut e, "I");
        run_keys(&mut e, "XX<Esc>");
        assert_eq!(
            e.buffer().lines(),
            &[
                "thiXXs is a line".to_string(),
                "   XX".to_string(),
                "thiXXs is a line".to_string()
            ]
        );
    }

    #[test]
    fn block_insert_pads_short_lines_to_block_column() {
        let mut e = editor_with("aaaaa\nbb\naaaaa");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jj");
        run_keys(&mut e, "I");
        run_keys(&mut e, "Y<Esc>");
        // Row 1 "bb" is shorter than col 3 — pad with one space then Y.
        assert_eq!(
            e.buffer().lines(),
            &[
                "aaaYaa".to_string(),
                "bb Y".to_string(),
                "aaaYaa".to_string()
            ]
        );
    }

    #[test]
    fn visual_block_append_repeats_across_rows() {
        let mut e = editor_with("foo\nbar\nbaz");
        run_keys(&mut e, "<C-v>");
        run_keys(&mut e, "jj");
        // Single-column block (anchor col = cursor col = 0); `A` appends
        // after column 0 on every row.
        run_keys(&mut e, "A");
        run_keys(&mut e, "!<Esc>");
        assert_eq!(
            e.buffer().lines(),
            &["f!oo".to_string(), "b!ar".to_string(), "b!az".to_string()]
        );
    }

    // ─── `/` / `?` search prompt ─────────────────────────────────────────

    #[test]
    fn slash_opens_forward_search_prompt() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "/");
        let p = e.search_prompt().expect("prompt should be active");
        assert!(p.text.is_empty());
        assert!(p.forward);
    }

    #[test]
    fn question_opens_backward_search_prompt() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "?");
        let p = e.search_prompt().expect("prompt should be active");
        assert!(!p.forward);
    }

    #[test]
    fn search_prompt_typing_updates_pattern_live() {
        let mut e = editor_with("foo bar\nbaz");
        run_keys(&mut e, "/bar");
        assert_eq!(e.search_prompt().unwrap().text, "bar");
        // Pattern set on the engine search state for live highlight.
        assert!(e.search_state().pattern.is_some());
    }

    #[test]
    fn search_prompt_backspace_and_enter() {
        let mut e = editor_with("hello world\nagain");
        run_keys(&mut e, "/worlx");
        e.handle_key(KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE));
        assert_eq!(e.search_prompt().unwrap().text, "worl");
        e.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        // Prompt closed, last_search set, cursor advanced to match.
        assert!(e.search_prompt().is_none());
        assert_eq!(e.last_search(), Some("worl"));
        assert_eq!(e.cursor(), (0, 6));
    }

    #[test]
    fn empty_search_prompt_enter_repeats_last_search() {
        let mut e = editor_with("foo bar foo baz foo");
        run_keys(&mut e, "/foo");
        e.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(e.cursor().1, 8);
        // Empty `/<CR>` should advance to the next match, not clear last_search.
        run_keys(&mut e, "/");
        e.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(e.cursor().1, 16);
        assert_eq!(e.last_search(), Some("foo"));
    }

    #[test]
    fn search_history_records_committed_patterns() {
        let mut e = editor_with("alpha beta gamma");
        run_keys(&mut e, "/alpha<CR>");
        run_keys(&mut e, "/beta<CR>");
        // Newest entry at the back.
        let history = e.vim.search_history.clone();
        assert_eq!(history, vec!["alpha", "beta"]);
    }

    #[test]
    fn search_history_dedupes_consecutive_repeats() {
        let mut e = editor_with("foo bar foo");
        run_keys(&mut e, "/foo<CR>");
        run_keys(&mut e, "/foo<CR>");
        run_keys(&mut e, "/bar<CR>");
        run_keys(&mut e, "/bar<CR>");
        // Two distinct entries; the duplicates collapsed.
        assert_eq!(e.vim.search_history.clone(), vec!["foo", "bar"]);
    }

    #[test]
    fn ctrl_p_walks_history_backward() {
        let mut e = editor_with("alpha beta gamma");
        run_keys(&mut e, "/alpha<CR>");
        run_keys(&mut e, "/beta<CR>");
        // Open a fresh prompt; Ctrl-P pulls in the newest entry.
        run_keys(&mut e, "/");
        assert_eq!(e.search_prompt().unwrap().text, "");
        e.handle_key(KeyEvent::new(KeyCode::Char('p'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "beta");
        e.handle_key(KeyEvent::new(KeyCode::Char('p'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "alpha");
        // At the oldest entry; further Ctrl-P is a no-op.
        e.handle_key(KeyEvent::new(KeyCode::Char('p'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "alpha");
    }

    #[test]
    fn ctrl_n_walks_history_forward_after_ctrl_p() {
        let mut e = editor_with("a b c");
        run_keys(&mut e, "/a<CR>");
        run_keys(&mut e, "/b<CR>");
        run_keys(&mut e, "/c<CR>");
        run_keys(&mut e, "/");
        // Walk back to "a", then forward again.
        for _ in 0..3 {
            e.handle_key(KeyEvent::new(KeyCode::Char('p'), KeyModifiers::CONTROL));
        }
        assert_eq!(e.search_prompt().unwrap().text, "a");
        e.handle_key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "b");
        e.handle_key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "c");
        // Past the newest — stays at "c".
        e.handle_key(KeyEvent::new(KeyCode::Char('n'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "c");
    }

    #[test]
    fn typing_after_history_walk_resets_cursor() {
        let mut e = editor_with("foo");
        run_keys(&mut e, "/foo<CR>");
        run_keys(&mut e, "/");
        e.handle_key(KeyEvent::new(KeyCode::Char('p'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "foo");
        // User edits — append a char. Next Ctrl-P should restart from
        // the newest entry, not continue walking older.
        e.handle_key(KeyEvent::new(KeyCode::Char('x'), KeyModifiers::NONE));
        assert_eq!(e.search_prompt().unwrap().text, "foox");
        e.handle_key(KeyEvent::new(KeyCode::Char('p'), KeyModifiers::CONTROL));
        assert_eq!(e.search_prompt().unwrap().text, "foo");
    }

    #[test]
    fn empty_backward_search_prompt_enter_repeats_last_search() {
        let mut e = editor_with("foo bar foo baz foo");
        // Forward to col 8, then `?<CR>` should walk backward to col 0.
        run_keys(&mut e, "/foo");
        e.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(e.cursor().1, 8);
        run_keys(&mut e, "?");
        e.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        assert_eq!(e.cursor().1, 0);
        assert_eq!(e.last_search(), Some("foo"));
    }

    #[test]
    fn search_prompt_esc_cancels_but_keeps_last_search() {
        let mut e = editor_with("foo bar\nbaz");
        run_keys(&mut e, "/bar");
        e.handle_key(KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE));
        assert!(e.search_prompt().is_none());
        assert_eq!(e.last_search(), Some("bar"));
    }

    #[test]
    fn search_then_n_and_shift_n_navigate() {
        let mut e = editor_with("foo bar foo baz foo");
        run_keys(&mut e, "/foo");
        e.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        // `/foo` + Enter jumps forward; we land on the next match after col 0.
        assert_eq!(e.cursor().1, 8);
        run_keys(&mut e, "n");
        assert_eq!(e.cursor().1, 16);
        run_keys(&mut e, "N");
        assert_eq!(e.cursor().1, 8);
    }

    #[test]
    fn question_mark_searches_backward_on_enter() {
        let mut e = editor_with("foo bar foo baz");
        e.jump_cursor(0, 10);
        run_keys(&mut e, "?foo");
        e.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE));
        // Cursor jumps backward to the closest match before col 10.
        assert_eq!(e.cursor(), (0, 8));
    }

    // ─── P6 quick wins (Y, gJ, ge / gE) ──────────────────────────────────

    #[test]
    fn big_y_yanks_to_end_of_line() {
        let mut e = editor_with("hello world");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "Y");
        assert_eq!(e.last_yank.as_deref(), Some("world"));
    }

    #[test]
    fn big_y_from_line_start_yanks_full_line() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "Y");
        assert_eq!(e.last_yank.as_deref(), Some("hello world"));
    }

    #[test]
    fn gj_joins_without_inserting_space() {
        let mut e = editor_with("hello\n    world");
        run_keys(&mut e, "gJ");
        // No space inserted, leading whitespace preserved.
        assert_eq!(e.buffer().lines(), &["hello    world".to_string()]);
    }

    #[test]
    fn gj_noop_on_last_line() {
        let mut e = editor_with("only");
        run_keys(&mut e, "gJ");
        assert_eq!(e.buffer().lines(), &["only".to_string()]);
    }

    #[test]
    fn ge_jumps_to_previous_word_end() {
        let mut e = editor_with("foo bar baz");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "ge");
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn ge_respects_word_class() {
        // Small-word `ge` treats `-` as its own word, so from mid-"bar"
        // it lands on the `-` rather than end of "foo".
        let mut e = editor_with("foo-bar baz");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "ge");
        assert_eq!(e.cursor(), (0, 3));
    }

    #[test]
    fn big_ge_treats_hyphens_as_part_of_word() {
        // `gE` uses WORD (whitespace-delimited) semantics so it skips
        // over the `-` and lands on the end of "foo-bar".
        let mut e = editor_with("foo-bar baz");
        e.jump_cursor(0, 10);
        run_keys(&mut e, "gE");
        assert_eq!(e.cursor(), (0, 6));
    }

    #[test]
    fn ge_crosses_line_boundary() {
        let mut e = editor_with("foo\nbar");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "ge");
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn dge_deletes_to_end_of_previous_word() {
        let mut e = editor_with("foo bar baz");
        e.jump_cursor(0, 8);
        // d + ge from 'b' of "baz": range is ge → col 6 ('r' of bar),
        // inclusive, so cols 6-8 ("r b") are cut.
        run_keys(&mut e, "dge");
        assert_eq!(e.buffer().lines()[0], "foo baaz");
    }

    #[test]
    fn ctrl_scroll_keys_do_not_panic() {
        // Viewport-less test: just exercise the code paths so a regression
        // in the scroll dispatch surfaces as a panic or assertion failure.
        let mut e = editor_with(
            (0..50)
                .map(|i| format!("line{i}"))
                .collect::<Vec<_>>()
                .join("\n")
                .as_str(),
        );
        run_keys(&mut e, "<C-f>");
        run_keys(&mut e, "<C-b>");
        // No explicit assert beyond "didn't panic".
        assert!(!e.buffer().lines().is_empty());
    }

    /// Regression: arrow-navigation during a count-insert session must
    /// not pull unrelated rows into the "inserted" replay string.
    /// Before the fix, `before_lines` only snapshotted the entry row,
    /// so the diff at Esc spuriously saw the navigated-over row as
    /// part of the insert — count-replay then duplicated cross-row
    /// content across the buffer.
    #[test]
    fn count_insert_with_arrow_nav_does_not_leak_rows() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("row0\nrow1\nrow2");
        // `3i`, type X, arrow down, Esc.
        run_keys(&mut e, "3iX<Down><Esc>");
        // Row 0 keeps the originally-typed X.
        assert!(e.buffer().lines()[0].contains('X'));
        // Row 1 must not contain a fragment of row 0 ("row0") — that
        // was the buggy leak from the before-diff window.
        assert!(
            !e.buffer().lines()[1].contains("row0"),
            "row1 leaked row0 contents: {:?}",
            e.buffer().lines()[1]
        );
        // Buffer stays the same number of rows — no extra lines
        // injected by a multi-line "inserted" replay.
        assert_eq!(e.buffer().lines().len(), 3);
    }

    // ─── Viewport scroll / jump tests ─────────────────────────────────

    fn editor_with_rows(n: usize, viewport: u16) -> Editor {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        let body = (0..n)
            .map(|i| format!("  line{}", i))
            .collect::<Vec<_>>()
            .join("\n");
        e.set_content(&body);
        e.set_viewport_height(viewport);
        e
    }

    #[test]
    fn ctrl_d_moves_cursor_half_page_down() {
        let mut e = editor_with_rows(100, 20);
        run_keys(&mut e, "<C-d>");
        assert_eq!(e.cursor().0, 10);
    }

    fn editor_with_wrap_lines(lines: &[&str], viewport: u16, text_width: u16) -> Editor {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content(&lines.join("\n"));
        e.set_viewport_height(viewport);
        let v = e.host_mut().viewport_mut();
        v.height = viewport;
        v.width = text_width;
        v.text_width = text_width;
        v.wrap = hjkl_buffer::Wrap::Char;
        e.settings_mut().wrap = hjkl_buffer::Wrap::Char;
        e
    }

    #[test]
    fn scrolloff_wrap_keeps_cursor_off_bottom_edge() {
        // 10 doc rows, each wraps to 3 segments → 30 screen rows.
        // Viewport height 12, margin = SCROLLOFF.min(11/2) = 5,
        // max bottom = 11 - 5 = 6. Plenty of headroom past row 4.
        let lines = ["aaaabbbbcccc"; 10];
        let mut e = editor_with_wrap_lines(&lines, 12, 4);
        e.jump_cursor(4, 0);
        e.ensure_cursor_in_scrolloff();
        let csr = e.buffer().cursor_screen_row(e.host().viewport()).unwrap();
        assert!(csr <= 6, "csr={csr}");
    }

    #[test]
    fn scrolloff_wrap_keeps_cursor_off_top_edge() {
        let lines = ["aaaabbbbcccc"; 10];
        let mut e = editor_with_wrap_lines(&lines, 12, 4);
        // Force top down then bring cursor up so the top-edge margin
        // path runs.
        e.jump_cursor(7, 0);
        e.ensure_cursor_in_scrolloff();
        e.jump_cursor(2, 0);
        e.ensure_cursor_in_scrolloff();
        let csr = e.buffer().cursor_screen_row(e.host().viewport()).unwrap();
        // SCROLLOFF.min((height - 1) / 2) = 5.min(5) = 5.
        assert!(csr >= 5, "csr={csr}");
    }

    #[test]
    fn scrolloff_wrap_clamps_top_at_buffer_end() {
        let lines = ["aaaabbbbcccc"; 5];
        let mut e = editor_with_wrap_lines(&lines, 12, 4);
        e.jump_cursor(4, 11);
        e.ensure_cursor_in_scrolloff();
        // max_top_for_height(12) on 15 screen rows: row 4 (3 segs) +
        // row 3 (3 segs) + row 2 (3 segs) + row 1 (3 segs) = 12 —
        // max_top = row 1. Margin can't be honoured at EOF (matches
        // vim's behaviour — scrolloff is a soft constraint).
        let top = e.host().viewport().top_row;
        assert_eq!(top, 1);
    }

    #[test]
    fn ctrl_u_moves_cursor_half_page_up() {
        let mut e = editor_with_rows(100, 20);
        e.jump_cursor(50, 0);
        run_keys(&mut e, "<C-u>");
        assert_eq!(e.cursor().0, 40);
    }

    #[test]
    fn ctrl_f_moves_cursor_full_page_down() {
        let mut e = editor_with_rows(100, 20);
        run_keys(&mut e, "<C-f>");
        // One full page ≈ h - 2 (overlap).
        assert_eq!(e.cursor().0, 18);
    }

    #[test]
    fn ctrl_b_moves_cursor_full_page_up() {
        let mut e = editor_with_rows(100, 20);
        e.jump_cursor(50, 0);
        run_keys(&mut e, "<C-b>");
        assert_eq!(e.cursor().0, 32);
    }

    #[test]
    fn ctrl_d_lands_on_first_non_blank() {
        let mut e = editor_with_rows(100, 20);
        run_keys(&mut e, "<C-d>");
        // "  line10" — first non-blank is col 2.
        assert_eq!(e.cursor().1, 2);
    }

    #[test]
    fn ctrl_d_clamps_at_end_of_buffer() {
        let mut e = editor_with_rows(5, 20);
        run_keys(&mut e, "<C-d>");
        assert_eq!(e.cursor().0, 4);
    }

    #[test]
    fn capital_h_jumps_to_viewport_top() {
        let mut e = editor_with_rows(100, 10);
        e.jump_cursor(50, 0);
        e.set_viewport_top(45);
        let top = e.host().viewport().top_row;
        run_keys(&mut e, "H");
        assert_eq!(e.cursor().0, top);
        assert_eq!(e.cursor().1, 2);
    }

    #[test]
    fn capital_l_jumps_to_viewport_bottom() {
        let mut e = editor_with_rows(100, 10);
        e.jump_cursor(50, 0);
        e.set_viewport_top(45);
        let top = e.host().viewport().top_row;
        run_keys(&mut e, "L");
        assert_eq!(e.cursor().0, top + 9);
    }

    #[test]
    fn capital_m_jumps_to_viewport_middle() {
        let mut e = editor_with_rows(100, 10);
        e.jump_cursor(50, 0);
        e.set_viewport_top(45);
        let top = e.host().viewport().top_row;
        run_keys(&mut e, "M");
        // 10-row viewport: middle is top + 4.
        assert_eq!(e.cursor().0, top + 4);
    }

    #[test]
    fn g_capital_m_lands_at_line_midpoint() {
        let mut e = editor_with("hello world!"); // 12 chars
        run_keys(&mut e, "gM");
        // floor(12 / 2) = 6.
        assert_eq!(e.cursor(), (0, 6));
    }

    #[test]
    fn g_capital_m_on_empty_line_stays_at_zero() {
        let mut e = editor_with("");
        run_keys(&mut e, "gM");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn g_capital_m_uses_current_line_only() {
        // Each line's midpoint is independent of others.
        let mut e = editor_with("a\nlonglongline"); // line 1: 12 chars
        e.jump_cursor(1, 0);
        run_keys(&mut e, "gM");
        assert_eq!(e.cursor(), (1, 6));
    }

    #[test]
    fn capital_h_count_offsets_from_top() {
        let mut e = editor_with_rows(100, 10);
        e.jump_cursor(50, 0);
        e.set_viewport_top(45);
        let top = e.host().viewport().top_row;
        run_keys(&mut e, "3H");
        assert_eq!(e.cursor().0, top + 2);
    }

    // ─── Jumplist tests ───────────────────────────────────────────────

    #[test]
    fn ctrl_o_returns_to_pre_g_position() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(5, 2);
        run_keys(&mut e, "G");
        assert_eq!(e.cursor().0, 49);
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.cursor(), (5, 2));
    }

    #[test]
    fn ctrl_i_redoes_jump_after_ctrl_o() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(5, 2);
        run_keys(&mut e, "G");
        let post = e.cursor();
        run_keys(&mut e, "<C-o>");
        run_keys(&mut e, "<C-i>");
        assert_eq!(e.cursor(), post);
    }

    #[test]
    fn new_jump_clears_forward_stack() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(5, 2);
        run_keys(&mut e, "G");
        run_keys(&mut e, "<C-o>");
        run_keys(&mut e, "gg");
        run_keys(&mut e, "<C-i>");
        assert_eq!(e.cursor().0, 0);
    }

    #[test]
    fn ctrl_o_on_empty_stack_is_noop() {
        let mut e = editor_with_rows(10, 20);
        e.jump_cursor(3, 1);
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.cursor(), (3, 1));
    }

    #[test]
    fn asterisk_search_pushes_jump() {
        let mut e = editor_with("foo bar\nbaz foo end");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "*");
        let after = e.cursor();
        assert_ne!(after, (0, 0));
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn h_viewport_jump_is_recorded() {
        let mut e = editor_with_rows(100, 10);
        e.jump_cursor(50, 0);
        e.set_viewport_top(45);
        let pre = e.cursor();
        run_keys(&mut e, "H");
        assert_ne!(e.cursor(), pre);
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.cursor(), pre);
    }

    #[test]
    fn j_k_motion_does_not_push_jump() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(5, 0);
        run_keys(&mut e, "jjj");
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.cursor().0, 8);
    }

    #[test]
    fn jumplist_caps_at_100() {
        let mut e = editor_with_rows(200, 20);
        for i in 0..101 {
            e.jump_cursor(i, 0);
            run_keys(&mut e, "G");
        }
        assert!(e.vim.jump_back.len() <= 100);
    }

    #[test]
    fn tab_acts_as_ctrl_i() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(5, 2);
        run_keys(&mut e, "G");
        let post = e.cursor();
        run_keys(&mut e, "<C-o>");
        e.handle_key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(e.cursor(), post);
    }

    // ─── Mark tests ───────────────────────────────────────────────────

    #[test]
    fn ma_then_backtick_a_jumps_exact() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(5, 3);
        run_keys(&mut e, "ma");
        e.jump_cursor(20, 0);
        run_keys(&mut e, "`a");
        assert_eq!(e.cursor(), (5, 3));
    }

    #[test]
    fn ma_then_apostrophe_a_lands_on_first_non_blank() {
        let mut e = editor_with_rows(50, 20);
        // "  line5" — first non-blank is col 2.
        e.jump_cursor(5, 6);
        run_keys(&mut e, "ma");
        e.jump_cursor(30, 4);
        run_keys(&mut e, "'a");
        assert_eq!(e.cursor(), (5, 2));
    }

    #[test]
    fn goto_mark_pushes_jumplist() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(10, 2);
        run_keys(&mut e, "mz");
        e.jump_cursor(3, 0);
        run_keys(&mut e, "`z");
        assert_eq!(e.cursor(), (10, 2));
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.cursor(), (3, 0));
    }

    #[test]
    fn goto_missing_mark_is_noop() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(3, 1);
        run_keys(&mut e, "`q");
        assert_eq!(e.cursor(), (3, 1));
    }

    #[test]
    fn uppercase_mark_stored_under_uppercase_key() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(5, 3);
        run_keys(&mut e, "mA");
        // 0.0.36: uppercase marks land in the unified `Editor::marks`
        // map under the uppercase key — not under 'a'.
        assert_eq!(e.mark('A'), Some((5, 3)));
        assert!(e.mark('a').is_none());
    }

    #[test]
    fn mark_survives_document_shrink_via_clamp() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(40, 4);
        run_keys(&mut e, "mx");
        // Shrink the buffer to 10 rows.
        e.set_content("a\nb\nc\nd\ne");
        run_keys(&mut e, "`x");
        // Mark clamped to last row, col 0 (short line).
        let (r, _) = e.cursor();
        assert!(r <= 4);
    }

    #[test]
    fn g_semicolon_walks_back_through_edits() {
        let mut e = editor_with("alpha\nbeta\ngamma");
        // Two distinct edits — cells (0, 0) → InsertChar lands cursor
        // at (0, 1), (2, 0) → (2, 1).
        e.jump_cursor(0, 0);
        run_keys(&mut e, "iX<Esc>");
        e.jump_cursor(2, 0);
        run_keys(&mut e, "iY<Esc>");
        // First g; lands on the most recent entry's exact cell.
        run_keys(&mut e, "g;");
        assert_eq!(e.cursor(), (2, 1));
        // Second g; walks to the older entry.
        run_keys(&mut e, "g;");
        assert_eq!(e.cursor(), (0, 1));
        // Past the oldest — no-op.
        run_keys(&mut e, "g;");
        assert_eq!(e.cursor(), (0, 1));
    }

    #[test]
    fn g_comma_walks_forward_after_g_semicolon() {
        let mut e = editor_with("a\nb\nc");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "iX<Esc>");
        e.jump_cursor(2, 0);
        run_keys(&mut e, "iY<Esc>");
        run_keys(&mut e, "g;");
        run_keys(&mut e, "g;");
        assert_eq!(e.cursor(), (0, 1));
        run_keys(&mut e, "g,");
        assert_eq!(e.cursor(), (2, 1));
    }

    #[test]
    fn new_edit_during_walk_trims_forward_entries() {
        let mut e = editor_with("a\nb\nc\nd");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "iX<Esc>"); // entry 0 → (0, 1)
        e.jump_cursor(2, 0);
        run_keys(&mut e, "iY<Esc>"); // entry 1 → (2, 1)
        // Walk back twice to land on entry 0.
        run_keys(&mut e, "g;");
        run_keys(&mut e, "g;");
        assert_eq!(e.cursor(), (0, 1));
        // New edit while walking discards entries forward of the cursor.
        run_keys(&mut e, "iZ<Esc>");
        // No newer entry left to walk to.
        run_keys(&mut e, "g,");
        // Cursor stays where the latest edit landed it.
        assert_ne!(e.cursor(), (2, 1));
    }

    // gq* tests moved to crates/hjkl-editor/tests/vim_ex_integration.rs
    // — they exercise the vim FSM through ex commands which now live in
    // a sibling crate. cargo dev-dep cycles produce duplicate type IDs
    // so the integration must run from the editor side.

    #[test]
    fn capital_mark_set_and_jump() {
        let mut e = editor_with("alpha\nbeta\ngamma\ndelta");
        e.jump_cursor(2, 1);
        run_keys(&mut e, "mA");
        // Move away.
        e.jump_cursor(0, 0);
        // Jump back via `'A`.
        run_keys(&mut e, "'A");
        // Linewise jump → row preserved, col first non-blank (here 0).
        assert_eq!(e.cursor().0, 2);
    }

    #[test]
    fn capital_mark_survives_set_content() {
        let mut e = editor_with("first buffer line\nsecond");
        e.jump_cursor(1, 3);
        run_keys(&mut e, "mA");
        // Swap buffer content (host loading a different tab).
        e.set_content("totally different content\non many\nrows of text");
        // `'A` should still jump to (1, 3) — it survived the swap.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "'A");
        assert_eq!(e.cursor().0, 1);
    }

    // capital_mark_shows_in_marks_listing moved to
    // crates/hjkl-editor/tests/vim_ex_integration.rs (depends on the
    // ex `marks` command).

    #[test]
    fn capital_mark_shifts_with_edit() {
        let mut e = editor_with("a\nb\nc\nd");
        e.jump_cursor(3, 0);
        run_keys(&mut e, "mA");
        // Delete the first row — `A` should shift up to row 2.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "dd");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "'A");
        assert_eq!(e.cursor().0, 2);
    }

    #[test]
    fn mark_below_delete_shifts_up() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        // Set mark `a` on row 3 (the `d`).
        e.jump_cursor(3, 0);
        run_keys(&mut e, "ma");
        // Go back to row 0 and `dd`.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "dd");
        // Mark `a` should now point at row 2 — its content stayed `d`.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "'a");
        assert_eq!(e.cursor().0, 2);
        assert_eq!(e.buffer().line(2).unwrap(), "d");
    }

    #[test]
    fn mark_on_deleted_row_is_dropped() {
        let mut e = editor_with("a\nb\nc\nd");
        // Mark `a` on row 1 (`b`).
        e.jump_cursor(1, 0);
        run_keys(&mut e, "ma");
        // Delete row 1.
        run_keys(&mut e, "dd");
        // The row that held `a` is gone; `'a` should be a no-op now.
        e.jump_cursor(2, 0);
        run_keys(&mut e, "'a");
        // Cursor stays on row 2 — `'a` no-ops on missing marks.
        assert_eq!(e.cursor().0, 2);
    }

    #[test]
    fn mark_above_edit_unchanged() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        // Mark `a` on row 0.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "ma");
        // Delete row 3.
        e.jump_cursor(3, 0);
        run_keys(&mut e, "dd");
        // Mark `a` should still point at row 0.
        e.jump_cursor(2, 0);
        run_keys(&mut e, "'a");
        assert_eq!(e.cursor().0, 0);
    }

    #[test]
    fn mark_shifts_down_after_insert() {
        let mut e = editor_with("a\nb\nc");
        // Mark `a` on row 2 (`c`).
        e.jump_cursor(2, 0);
        run_keys(&mut e, "ma");
        // Open a new line above row 0 with `O\nfoo<Esc>`.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "Onew<Esc>");
        // Buffer is now ["new", "a", "b", "c"]; mark `a` should track
        // the original content row → 3.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "'a");
        assert_eq!(e.cursor().0, 3);
        assert_eq!(e.buffer().line(3).unwrap(), "c");
    }

    // ─── Search / jumplist interaction ───────────────────────────────

    #[test]
    fn forward_search_commit_pushes_jump() {
        let mut e = editor_with("alpha beta\nfoo target end\nmore");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "/target<CR>");
        // Cursor moved to the match.
        assert_ne!(e.cursor(), (0, 0));
        // Ctrl-o returns to the pre-search position.
        run_keys(&mut e, "<C-o>");
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn search_commit_no_match_does_not_push_jump() {
        let mut e = editor_with("alpha beta\nfoo end");
        e.jump_cursor(0, 3);
        let pre_len = e.vim.jump_back.len();
        run_keys(&mut e, "/zzznotfound<CR>");
        // No match → cursor stays, jumplist shouldn't grow.
        assert_eq!(e.vim.jump_back.len(), pre_len);
    }

    // ─── Phase 7b: migration buffer cursor sync ──────────────────────

    #[test]
    fn buffer_cursor_mirrors_textarea_after_horizontal_motion() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "lll");
        let (row, col) = e.cursor();
        assert_eq!(e.buffer.cursor().row, row);
        assert_eq!(e.buffer.cursor().col, col);
    }

    #[test]
    fn buffer_cursor_mirrors_textarea_after_vertical_motion() {
        let mut e = editor_with("aaaa\nbbbb\ncccc");
        run_keys(&mut e, "jj");
        let (row, col) = e.cursor();
        assert_eq!(e.buffer.cursor().row, row);
        assert_eq!(e.buffer.cursor().col, col);
    }

    #[test]
    fn buffer_cursor_mirrors_textarea_after_word_motion() {
        let mut e = editor_with("foo bar baz");
        run_keys(&mut e, "ww");
        let (row, col) = e.cursor();
        assert_eq!(e.buffer.cursor().row, row);
        assert_eq!(e.buffer.cursor().col, col);
    }

    #[test]
    fn buffer_cursor_mirrors_textarea_after_jump_motion() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        run_keys(&mut e, "G");
        let (row, col) = e.cursor();
        assert_eq!(e.buffer.cursor().row, row);
        assert_eq!(e.buffer.cursor().col, col);
    }

    #[test]
    fn editor_sticky_col_tracks_horizontal_motion() {
        let mut e = editor_with("longline\nhi\nlongline");
        // `fl` from col 0 lands on the next `l` past the cursor —
        // "longline" → second `l` is at col 4. Horizontal motion
        // should refresh sticky to that column so the next `j`
        // picks it up across the short row.
        run_keys(&mut e, "fl");
        let landed = e.cursor().1;
        assert!(landed > 0, "fl should have moved");
        run_keys(&mut e, "j");
        // Editor is the single owner of sticky_col (0.0.28). The
        // sticky value was set from the post-`fl` column.
        assert_eq!(e.sticky_col(), Some(landed));
    }

    #[test]
    fn buffer_content_mirrors_textarea_after_insert() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "iXYZ<Esc>");
        let text = e.buffer().lines().join("\n");
        assert_eq!(e.buffer.as_string(), text);
    }

    #[test]
    fn buffer_content_mirrors_textarea_after_delete() {
        let mut e = editor_with("alpha bravo charlie");
        run_keys(&mut e, "dw");
        let text = e.buffer().lines().join("\n");
        assert_eq!(e.buffer.as_string(), text);
    }

    #[test]
    fn buffer_content_mirrors_textarea_after_dd() {
        let mut e = editor_with("a\nb\nc\nd");
        run_keys(&mut e, "jdd");
        let text = e.buffer().lines().join("\n");
        assert_eq!(e.buffer.as_string(), text);
    }

    #[test]
    fn buffer_content_mirrors_textarea_after_open_line() {
        let mut e = editor_with("foo\nbar");
        run_keys(&mut e, "oNEW<Esc>");
        let text = e.buffer().lines().join("\n");
        assert_eq!(e.buffer.as_string(), text);
    }

    #[test]
    fn buffer_content_mirrors_textarea_after_paste() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "yy");
        run_keys(&mut e, "p");
        let text = e.buffer().lines().join("\n");
        assert_eq!(e.buffer.as_string(), text);
    }

    #[test]
    fn buffer_selection_none_in_normal_mode() {
        let e = editor_with("foo bar");
        assert!(e.buffer_selection().is_none());
    }

    #[test]
    fn buffer_selection_char_in_visual_mode() {
        use hjkl_buffer::{Position, Selection};
        let mut e = editor_with("hello world");
        run_keys(&mut e, "vlll");
        assert_eq!(
            e.buffer_selection(),
            Some(Selection::Char {
                anchor: Position::new(0, 0),
                head: Position::new(0, 3),
            })
        );
    }

    #[test]
    fn buffer_selection_line_in_visual_line_mode() {
        use hjkl_buffer::Selection;
        let mut e = editor_with("a\nb\nc\nd");
        run_keys(&mut e, "Vj");
        assert_eq!(
            e.buffer_selection(),
            Some(Selection::Line {
                anchor_row: 0,
                head_row: 1,
            })
        );
    }

    #[test]
    fn wrapscan_off_blocks_wrap_around() {
        let mut e = editor_with("first\nsecond\nthird\n");
        e.settings_mut().wrapscan = false;
        // Place cursor on row 2 ("third") and search for "first".
        e.jump_cursor(2, 0);
        run_keys(&mut e, "/first<CR>");
        // No wrap → cursor stays on row 2.
        assert_eq!(e.cursor().0, 2, "wrapscan off should block wrap");
        // Re-enable wrapscan and try again.
        e.settings_mut().wrapscan = true;
        run_keys(&mut e, "/first<CR>");
        assert_eq!(e.cursor().0, 0, "wrapscan on should wrap to row 0");
    }

    #[test]
    fn smartcase_uppercase_pattern_stays_sensitive() {
        let mut e = editor_with("foo\nFoo\nBAR\n");
        e.settings_mut().ignore_case = true;
        e.settings_mut().smartcase = true;
        // All-lowercase pattern → ignorecase wins → compiled regex
        // is case-insensitive.
        run_keys(&mut e, "/foo<CR>");
        let r1 = e
            .search_state()
            .pattern
            .as_ref()
            .unwrap()
            .as_str()
            .to_string();
        assert!(r1.starts_with("(?i)"), "lowercase under smartcase: {r1}");
        // Uppercase letter → smartcase flips back to case-sensitive.
        run_keys(&mut e, "/Foo<CR>");
        let r2 = e
            .search_state()
            .pattern
            .as_ref()
            .unwrap()
            .as_str()
            .to_string();
        assert!(!r2.starts_with("(?i)"), "mixed-case under smartcase: {r2}");
    }

    #[test]
    fn enter_with_autoindent_copies_leading_whitespace() {
        let mut e = editor_with("    foo");
        e.jump_cursor(0, 7);
        run_keys(&mut e, "i<CR>");
        assert_eq!(e.buffer.line(1).unwrap(), "    ");
    }

    #[test]
    fn enter_without_autoindent_inserts_bare_newline() {
        let mut e = editor_with("    foo");
        e.settings_mut().autoindent = false;
        e.jump_cursor(0, 7);
        run_keys(&mut e, "i<CR>");
        assert_eq!(e.buffer.line(1).unwrap(), "");
    }

    #[test]
    fn iskeyword_default_treats_alnum_underscore_as_word() {
        let mut e = editor_with("foo_bar baz");
        // `*` searches for the word at the cursor — picks up everything
        // matching iskeyword. With default spec, `foo_bar` is one word,
        // so the search pattern should bound that whole token.
        e.jump_cursor(0, 0);
        run_keys(&mut e, "*");
        let p = e
            .search_state()
            .pattern
            .as_ref()
            .unwrap()
            .as_str()
            .to_string();
        assert!(p.contains("foo_bar"), "default iskeyword: {p}");
    }

    #[test]
    fn w_motion_respects_custom_iskeyword() {
        // `foo-bar baz`. With the default spec, `-` is NOT a word char,
        // so `foo` / `-` / `bar` / ` ` / `baz` are 5 transitions and a
        // single `w` from col 0 lands on `-` (col 3).
        let mut e = editor_with("foo-bar baz");
        run_keys(&mut e, "w");
        assert_eq!(e.cursor().1, 3, "default iskeyword: {:?}", e.cursor());
        // Re-set with `-` (45) treated as a word char. Now `foo-bar` is
        // one token; `w` from col 0 should jump to `baz` (col 8).
        let mut e2 = editor_with("foo-bar baz");
        e2.set_iskeyword("@,_,45");
        run_keys(&mut e2, "w");
        assert_eq!(e2.cursor().1, 8, "dash-as-word: {:?}", e2.cursor());
    }

    #[test]
    fn iskeyword_with_dash_treats_dash_as_word_char() {
        let mut e = editor_with("foo-bar baz");
        e.settings_mut().iskeyword = "@,_,45".to_string();
        e.jump_cursor(0, 0);
        run_keys(&mut e, "*");
        let p = e
            .search_state()
            .pattern
            .as_ref()
            .unwrap()
            .as_str()
            .to_string();
        assert!(p.contains("foo-bar"), "dash-as-word: {p}");
    }

    #[test]
    fn timeoutlen_drops_pending_g_prefix() {
        use std::time::{Duration, Instant};
        let mut e = editor_with("a\nb\nc");
        e.jump_cursor(2, 0);
        // First `g` lands us in g-pending state.
        run_keys(&mut e, "g");
        assert!(matches!(e.vim.pending, super::Pending::G));
        // Push last_input timestamps into the past beyond the default
        // timeout. 0.0.29 (Patch B) drives `:set timeoutlen` off
        // `Host::now()` (monotonic Duration), so shrink the timeout
        // window to a nanosecond and zero out the host slot — any
        // wall-clock progress between this line and the next step
        // exceeds it. The Instant-flavoured field is rewound for
        // snapshot tests that still observe it directly.
        e.settings.timeout_len = Duration::from_nanos(0);
        e.vim.last_input_at = Some(Instant::now() - Duration::from_secs(60));
        e.vim.last_input_host_at = Some(Duration::ZERO);
        // Second `g` arrives "late" — timeout fires, prefix is cleared,
        // and the bare `g` is re-dispatched: nothing happens at the
        // engine level because `g` alone isn't a complete command.
        run_keys(&mut e, "g");
        // Cursor must still be at row 2 — `gg` was NOT completed.
        assert_eq!(e.cursor().0, 2, "timeout must abandon g-prefix");
    }

    #[test]
    fn undobreak_on_breaks_group_at_arrow_motion() {
        let mut e = editor_with("");
        // i a a a <Left> b b b <Esc> u
        run_keys(&mut e, "iaaa<Left>bbb<Esc>u");
        // Default settings.undo_break_on_motion = true, so `u` only
        // reverses the `bbb` run; `aaa` remains.
        let line = e.buffer.line(0).unwrap_or("").to_string();
        assert!(line.contains("aaa"), "after undobreak: {line:?}");
        assert!(!line.contains("bbb"), "bbb should be undone: {line:?}");
    }

    #[test]
    fn undobreak_off_keeps_full_run_in_one_group() {
        let mut e = editor_with("");
        e.settings_mut().undo_break_on_motion = false;
        run_keys(&mut e, "iaaa<Left>bbb<Esc>u");
        // With undobreak off, the whole insert (aaa<Left>bbb) is one
        // group — `u` reverts back to empty.
        assert_eq!(e.buffer.line(0).unwrap_or(""), "");
    }

    #[test]
    fn undobreak_round_trips_through_options() {
        let e = editor_with("");
        let opts = e.current_options();
        assert!(opts.undo_break_on_motion);
        let mut e2 = editor_with("");
        let mut new_opts = opts.clone();
        new_opts.undo_break_on_motion = false;
        e2.apply_options(&new_opts);
        assert!(!e2.current_options().undo_break_on_motion);
    }

    #[test]
    fn undo_levels_cap_drops_oldest() {
        let mut e = editor_with("abcde");
        e.settings_mut().undo_levels = 3;
        run_keys(&mut e, "ra");
        run_keys(&mut e, "lrb");
        run_keys(&mut e, "lrc");
        run_keys(&mut e, "lrd");
        run_keys(&mut e, "lre");
        assert_eq!(e.undo_stack_len(), 3);
    }

    #[test]
    fn tab_inserts_literal_tab_when_noexpandtab() {
        let mut e = editor_with("");
        // 0.2.0: expandtab now defaults on (modern). Opt out for the
        // literal-tab test.
        e.settings_mut().expandtab = false;
        e.settings_mut().softtabstop = 0;
        run_keys(&mut e, "i");
        e.handle_key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(e.buffer.line(0).unwrap(), "\t");
    }

    #[test]
    fn tab_inserts_spaces_when_expandtab() {
        let mut e = editor_with("");
        e.settings_mut().expandtab = true;
        e.settings_mut().tabstop = 4;
        run_keys(&mut e, "i");
        e.handle_key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(e.buffer.line(0).unwrap(), "    ");
    }

    #[test]
    fn tab_with_softtabstop_fills_to_next_boundary() {
        // sts=4, cursor at col 2 → Tab inserts 2 spaces (to col 4).
        let mut e = editor_with("ab");
        e.settings_mut().expandtab = true;
        e.settings_mut().tabstop = 8;
        e.settings_mut().softtabstop = 4;
        run_keys(&mut e, "A"); // append at end (col 2)
        e.handle_key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE));
        assert_eq!(e.buffer.line(0).unwrap(), "ab  ");
    }

    #[test]
    fn backspace_deletes_softtab_run() {
        // sts=4, line "    x" with cursor at col 4 → Backspace deletes
        // the whole 4-space run instead of one char.
        let mut e = editor_with("    x");
        e.settings_mut().softtabstop = 4;
        // Move to col 4 (start of 'x'), then enter insert.
        run_keys(&mut e, "fxi");
        e.handle_key(KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE));
        assert_eq!(e.buffer.line(0).unwrap(), "x");
    }

    #[test]
    fn backspace_falls_back_to_single_char_when_run_not_aligned() {
        // sts=4, but cursor at col 5 (one space past the boundary) →
        // Backspace deletes only the one trailing space.
        let mut e = editor_with("     x");
        e.settings_mut().softtabstop = 4;
        run_keys(&mut e, "fxi");
        e.handle_key(KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE));
        assert_eq!(e.buffer.line(0).unwrap(), "    x");
    }

    #[test]
    fn readonly_blocks_insert_mutation() {
        let mut e = editor_with("hello");
        e.settings_mut().readonly = true;
        run_keys(&mut e, "iX<Esc>");
        assert_eq!(e.buffer.line(0).unwrap(), "hello");
    }

    #[cfg(feature = "ratatui")]
    #[test]
    fn intern_ratatui_style_dedups_repeated_styles() {
        use ratatui::style::{Color, Style};
        let mut e = editor_with("");
        let red = Style::default().fg(Color::Red);
        let blue = Style::default().fg(Color::Blue);
        let id_r1 = e.intern_ratatui_style(red);
        let id_r2 = e.intern_ratatui_style(red);
        let id_b = e.intern_ratatui_style(blue);
        assert_eq!(id_r1, id_r2);
        assert_ne!(id_r1, id_b);
        assert_eq!(e.style_table().len(), 2);
    }

    #[cfg(feature = "ratatui")]
    #[test]
    fn install_ratatui_syntax_spans_translates_styled_spans() {
        use ratatui::style::{Color, Style};
        let mut e = editor_with("SELECT foo");
        e.install_ratatui_syntax_spans(vec![vec![(0, 6, Style::default().fg(Color::Red))]]);
        let by_row = e.buffer_spans();
        assert_eq!(by_row.len(), 1);
        assert_eq!(by_row[0].len(), 1);
        assert_eq!(by_row[0][0].start_byte, 0);
        assert_eq!(by_row[0][0].end_byte, 6);
        let id = by_row[0][0].style;
        assert_eq!(e.style_table()[id as usize].fg, Some(Color::Red));
    }

    #[cfg(feature = "ratatui")]
    #[test]
    fn install_ratatui_syntax_spans_clamps_sentinel_end() {
        use ratatui::style::{Color, Style};
        let mut e = editor_with("hello");
        e.install_ratatui_syntax_spans(vec![vec![(
            0,
            usize::MAX,
            Style::default().fg(Color::Blue),
        )]]);
        let by_row = e.buffer_spans();
        assert_eq!(by_row[0][0].end_byte, 5);
    }

    #[cfg(feature = "ratatui")]
    #[test]
    fn install_ratatui_syntax_spans_drops_zero_width() {
        use ratatui::style::{Color, Style};
        let mut e = editor_with("abc");
        e.install_ratatui_syntax_spans(vec![vec![(2, 2, Style::default().fg(Color::Red))]]);
        assert!(e.buffer_spans()[0].is_empty());
    }

    #[test]
    fn named_register_yank_into_a_then_paste_from_a() {
        let mut e = editor_with("hello world\nsecond");
        run_keys(&mut e, "\"ayw");
        // `yw` over "hello world" yanks "hello " (word + trailing space).
        assert_eq!(e.registers().read('a').unwrap().text, "hello ");
        // Move to second line then paste from "a.
        run_keys(&mut e, "j0\"aP");
        assert_eq!(e.buffer().lines()[1], "hello second");
    }

    #[test]
    fn capital_r_overstrikes_chars() {
        let mut e = editor_with("hello");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "RXY<Esc>");
        // 'h' and 'e' replaced; 'llo' kept.
        assert_eq!(e.buffer().lines()[0], "XYllo");
    }

    #[test]
    fn capital_r_at_eol_appends() {
        let mut e = editor_with("hi");
        e.jump_cursor(0, 1);
        // Cursor on the final 'i'; replace it then keep typing past EOL.
        run_keys(&mut e, "RXYZ<Esc>");
        assert_eq!(e.buffer().lines()[0], "hXYZ");
    }

    #[test]
    fn capital_r_count_does_not_repeat_overstrike_char_by_char() {
        // Vim's `2R` replays the *whole session* on Esc, not each char.
        // We don't model that fully, but the basic R should at least
        // not crash on empty session count handling.
        let mut e = editor_with("abc");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "RX<Esc>");
        assert_eq!(e.buffer().lines()[0], "Xbc");
    }

    #[test]
    fn ctrl_r_in_insert_pastes_named_register() {
        let mut e = editor_with("hello world");
        // Yank "hello " into "a".
        run_keys(&mut e, "\"ayw");
        assert_eq!(e.registers().read('a').unwrap().text, "hello ");
        // Open a fresh line, enter insert, Ctrl-R a.
        run_keys(&mut e, "o");
        assert_eq!(e.vim_mode(), VimMode::Insert);
        e.handle_key(KeyEvent::new(KeyCode::Char('r'), KeyModifiers::CONTROL));
        e.handle_key(KeyEvent::new(KeyCode::Char('a'), KeyModifiers::NONE));
        assert_eq!(e.buffer().lines()[1], "hello ");
        // Cursor sits at end of inserted payload (col 6).
        assert_eq!(e.cursor(), (1, 6));
        // Stayed in insert mode; next char appends.
        assert_eq!(e.vim_mode(), VimMode::Insert);
        e.handle_key(KeyEvent::new(KeyCode::Char('X'), KeyModifiers::NONE));
        assert_eq!(e.buffer().lines()[1], "hello X");
    }

    #[test]
    fn ctrl_r_with_unnamed_register() {
        let mut e = editor_with("foo");
        run_keys(&mut e, "yiw");
        run_keys(&mut e, "A ");
        // Unnamed register paste via `"`.
        e.handle_key(KeyEvent::new(KeyCode::Char('r'), KeyModifiers::CONTROL));
        e.handle_key(KeyEvent::new(KeyCode::Char('"'), KeyModifiers::NONE));
        assert_eq!(e.buffer().lines()[0], "foo foo");
    }

    #[test]
    fn ctrl_r_unknown_selector_is_no_op() {
        let mut e = editor_with("abc");
        run_keys(&mut e, "A");
        e.handle_key(KeyEvent::new(KeyCode::Char('r'), KeyModifiers::CONTROL));
        // `?` isn't a valid register selector — paste skipped, the
        // armed flag still clears so the next key types normally.
        e.handle_key(KeyEvent::new(KeyCode::Char('?'), KeyModifiers::NONE));
        e.handle_key(KeyEvent::new(KeyCode::Char('Z'), KeyModifiers::NONE));
        assert_eq!(e.buffer().lines()[0], "abcZ");
    }

    #[test]
    fn ctrl_r_multiline_register_pastes_with_newlines() {
        let mut e = editor_with("alpha\nbeta\ngamma");
        // Yank two whole lines into "b".
        run_keys(&mut e, "\"byy");
        run_keys(&mut e, "j\"byy");
        // Linewise yanks include trailing \n; second yank into uppercase
        // would append, but lowercase "b" overwrote — ensure we have a
        // multi-line payload by yanking 2 lines linewise via V.
        run_keys(&mut e, "ggVj\"by");
        let payload = e.registers().read('b').unwrap().text.clone();
        assert!(payload.contains('\n'));
        run_keys(&mut e, "Go");
        e.handle_key(KeyEvent::new(KeyCode::Char('r'), KeyModifiers::CONTROL));
        e.handle_key(KeyEvent::new(KeyCode::Char('b'), KeyModifiers::NONE));
        // The buffer should now contain the original 3 lines plus the
        // pasted 2-line payload (with its own newline) on its own line.
        let total_lines = e.buffer().lines().len();
        assert!(total_lines >= 5);
    }

    #[test]
    fn yank_zero_holds_last_yank_after_delete() {
        let mut e = editor_with("hello world");
        run_keys(&mut e, "yw");
        let yanked = e.registers().read('0').unwrap().text.clone();
        assert!(!yanked.is_empty());
        // Delete a word; "0 should still hold the original yank.
        run_keys(&mut e, "dw");
        assert_eq!(e.registers().read('0').unwrap().text, yanked);
        // "1 holds the just-deleted text (non-empty, regardless of exact contents).
        assert!(!e.registers().read('1').unwrap().text.is_empty());
    }

    #[test]
    fn delete_ring_rotates_through_one_through_nine() {
        let mut e = editor_with("a b c d e f g h i j");
        // Delete each word — each delete pushes onto "1, shifting older.
        for _ in 0..3 {
            run_keys(&mut e, "dw");
        }
        // Most recent delete is in "1.
        let r1 = e.registers().read('1').unwrap().text.clone();
        let r2 = e.registers().read('2').unwrap().text.clone();
        let r3 = e.registers().read('3').unwrap().text.clone();
        assert!(!r1.is_empty() && !r2.is_empty() && !r3.is_empty());
        assert_ne!(r1, r2);
        assert_ne!(r2, r3);
    }

    #[test]
    fn capital_register_appends_to_lowercase() {
        let mut e = editor_with("foo bar");
        run_keys(&mut e, "\"ayw");
        let first = e.registers().read('a').unwrap().text.clone();
        assert!(first.contains("foo"));
        // Yank again into "A — appends to "a.
        run_keys(&mut e, "w\"Ayw");
        let combined = e.registers().read('a').unwrap().text.clone();
        assert!(combined.starts_with(&first));
        assert!(combined.contains("bar"));
    }

    #[test]
    fn zf_in_visual_line_creates_closed_fold() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        // VisualLine over rows 1..=3 then zf.
        e.jump_cursor(1, 0);
        run_keys(&mut e, "Vjjzf");
        assert_eq!(e.buffer().folds().len(), 1);
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 1);
        assert_eq!(f.end_row, 3);
        assert!(f.closed);
    }

    #[test]
    fn zfj_in_normal_creates_two_row_fold() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "zfj");
        assert_eq!(e.buffer().folds().len(), 1);
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 1);
        assert_eq!(f.end_row, 2);
        assert!(f.closed);
        // Cursor stays where it started.
        assert_eq!(e.cursor().0, 1);
    }

    #[test]
    fn zf_with_count_folds_count_rows() {
        let mut e = editor_with("a\nb\nc\nd\ne\nf");
        e.jump_cursor(0, 0);
        // `zf3j` — fold rows 0..=3.
        run_keys(&mut e, "zf3j");
        assert_eq!(e.buffer().folds().len(), 1);
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 0);
        assert_eq!(f.end_row, 3);
    }

    #[test]
    fn zfk_folds_upward_range() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        e.jump_cursor(3, 0);
        run_keys(&mut e, "zfk");
        let f = e.buffer().folds()[0];
        // start_row = min(3, 2) = 2, end_row = max(3, 2) = 3.
        assert_eq!(f.start_row, 2);
        assert_eq!(f.end_row, 3);
    }

    #[test]
    fn zf_capital_g_folds_to_bottom() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        e.jump_cursor(1, 0);
        // `G` is a single-char motion; folds rows 1..=4.
        run_keys(&mut e, "zfG");
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 1);
        assert_eq!(f.end_row, 4);
    }

    #[test]
    fn zfgg_folds_to_top_via_operator_pipeline() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        e.jump_cursor(3, 0);
        // `gg` is a 2-key chord (Pending::OpG path) — `zfgg` works
        // because `zf` arms `Pending::Op { Fold }` which already knows
        // how to wait for `g` then `g`.
        run_keys(&mut e, "zfgg");
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 0);
        assert_eq!(f.end_row, 3);
    }

    #[test]
    fn zfip_folds_paragraph_via_text_object() {
        let mut e = editor_with("alpha\nbeta\ngamma\n\ndelta\nepsilon");
        e.jump_cursor(1, 0);
        // `ip` is a text object — same operator pipeline routes it.
        run_keys(&mut e, "zfip");
        assert_eq!(e.buffer().folds().len(), 1);
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 0);
        assert_eq!(f.end_row, 2);
    }

    #[test]
    fn zfap_folds_paragraph_with_trailing_blank() {
        let mut e = editor_with("alpha\nbeta\ngamma\n\ndelta");
        e.jump_cursor(0, 0);
        // `ap` includes the trailing blank line.
        run_keys(&mut e, "zfap");
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 0);
        assert_eq!(f.end_row, 3);
    }

    #[test]
    fn zf_paragraph_motion_folds_to_blank() {
        let mut e = editor_with("alpha\nbeta\n\ngamma");
        e.jump_cursor(0, 0);
        // `}` jumps to the blank-line boundary; fold spans rows 0..=2.
        run_keys(&mut e, "zf}");
        let f = e.buffer().folds()[0];
        assert_eq!(f.start_row, 0);
        assert_eq!(f.end_row, 2);
    }

    #[test]
    fn za_toggles_fold_under_cursor() {
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(1, 2, true);
        e.jump_cursor(1, 0);
        run_keys(&mut e, "za");
        assert!(!e.buffer().folds()[0].closed);
        run_keys(&mut e, "za");
        assert!(e.buffer().folds()[0].closed);
    }

    #[test]
    fn zr_opens_all_folds_zm_closes_all() {
        let mut e = editor_with("a\nb\nc\nd\ne\nf");
        e.buffer_mut().add_fold(0, 1, true);
        e.buffer_mut().add_fold(2, 3, true);
        e.buffer_mut().add_fold(4, 5, true);
        run_keys(&mut e, "zR");
        assert!(e.buffer().folds().iter().all(|f| !f.closed));
        run_keys(&mut e, "zM");
        assert!(e.buffer().folds().iter().all(|f| f.closed));
    }

    #[test]
    fn ze_clears_all_folds() {
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(0, 1, true);
        e.buffer_mut().add_fold(2, 3, false);
        run_keys(&mut e, "zE");
        assert!(e.buffer().folds().is_empty());
    }

    #[test]
    fn g_underscore_jumps_to_last_non_blank() {
        let mut e = editor_with("hello world   ");
        run_keys(&mut e, "g_");
        // Last non-blank is 'd' at col 10.
        assert_eq!(e.cursor().1, 10);
    }

    #[test]
    fn gj_and_gk_alias_j_and_k() {
        let mut e = editor_with("a\nb\nc");
        run_keys(&mut e, "gj");
        assert_eq!(e.cursor().0, 1);
        run_keys(&mut e, "gk");
        assert_eq!(e.cursor().0, 0);
    }

    #[test]
    fn paragraph_motions_walk_blank_lines() {
        let mut e = editor_with("first\nblock\n\nsecond\nblock\n\nthird");
        run_keys(&mut e, "}");
        assert_eq!(e.cursor().0, 2);
        run_keys(&mut e, "}");
        assert_eq!(e.cursor().0, 5);
        run_keys(&mut e, "{");
        assert_eq!(e.cursor().0, 2);
    }

    #[test]
    fn gv_reenters_last_visual_selection() {
        let mut e = editor_with("alpha\nbeta\ngamma");
        run_keys(&mut e, "Vj");
        // Exit visual.
        run_keys(&mut e, "<Esc>");
        assert_eq!(e.vim_mode(), VimMode::Normal);
        // gv re-enters VisualLine.
        run_keys(&mut e, "gv");
        assert_eq!(e.vim_mode(), VimMode::VisualLine);
    }

    #[test]
    fn o_in_visual_swaps_anchor_and_cursor() {
        let mut e = editor_with("hello world");
        // v then move right 4 — anchor at col 0, cursor at col 4.
        run_keys(&mut e, "vllll");
        assert_eq!(e.cursor().1, 4);
        // o swaps; cursor jumps to anchor (col 0).
        run_keys(&mut e, "o");
        assert_eq!(e.cursor().1, 0);
        // Anchor now at original cursor (col 4).
        assert_eq!(e.vim.visual_anchor, (0, 4));
    }

    #[test]
    fn editing_inside_fold_invalidates_it() {
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(1, 2, true);
        e.jump_cursor(1, 0);
        // Insert a char on a row covered by the fold.
        run_keys(&mut e, "iX<Esc>");
        // Fold should be gone — vim opens (drops) folds on edit.
        assert!(e.buffer().folds().is_empty());
    }

    #[test]
    fn zd_removes_fold_under_cursor() {
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(1, 2, true);
        e.jump_cursor(2, 0);
        run_keys(&mut e, "zd");
        assert!(e.buffer().folds().is_empty());
    }

    #[test]
    fn take_fold_ops_observes_z_keystroke_dispatch() {
        // 0.0.38 (Patch C-δ.4): every `z…` keystroke routes through
        // `Editor::apply_fold_op`, which queues a `FoldOp` for hosts to
        // observe via `take_fold_ops` AND applies the op locally so
        // buffer fold storage stays in sync.
        use crate::types::FoldOp;
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(1, 2, true);
        e.jump_cursor(1, 0);
        // Drain any queue from the buffer setup above (none expected,
        // but be defensive).
        let _ = e.take_fold_ops();
        run_keys(&mut e, "zo");
        run_keys(&mut e, "zM");
        let ops = e.take_fold_ops();
        assert_eq!(ops.len(), 2);
        assert!(matches!(ops[0], FoldOp::OpenAt(1)));
        assert!(matches!(ops[1], FoldOp::CloseAll));
        // Second drain returns empty.
        assert!(e.take_fold_ops().is_empty());
    }

    #[test]
    fn edit_pipeline_emits_invalidate_fold_op() {
        // The edit pipeline routes its fold invalidation through
        // `apply_fold_op` so hosts can observe + dedupe.
        use crate::types::FoldOp;
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(1, 2, true);
        e.jump_cursor(1, 0);
        let _ = e.take_fold_ops();
        run_keys(&mut e, "iX<Esc>");
        let ops = e.take_fold_ops();
        assert!(
            ops.iter().any(|op| matches!(op, FoldOp::Invalidate { .. })),
            "expected at least one Invalidate op, got {ops:?}"
        );
    }

    #[test]
    fn dot_mark_jumps_to_last_edit_position() {
        let mut e = editor_with("alpha\nbeta\ngamma\ndelta");
        e.jump_cursor(2, 0);
        // Insert at line 2 — sets last_edit_pos.
        run_keys(&mut e, "iX<Esc>");
        let after_edit = e.cursor();
        // Move away.
        run_keys(&mut e, "gg");
        assert_eq!(e.cursor().0, 0);
        // `'.` jumps back to the edit's row (linewise variant).
        run_keys(&mut e, "'.");
        assert_eq!(e.cursor().0, after_edit.0);
    }

    #[test]
    fn quote_quote_returns_to_pre_jump_position() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(10, 2);
        let before = e.cursor();
        // `G` is a big jump — pushes (10, 2) onto jump_back.
        run_keys(&mut e, "G");
        assert_ne!(e.cursor(), before);
        // `''` jumps back to the pre-jump position (linewise).
        run_keys(&mut e, "''");
        assert_eq!(e.cursor().0, before.0);
    }

    #[test]
    fn backtick_backtick_restores_exact_pre_jump_pos() {
        let mut e = editor_with_rows(50, 20);
        e.jump_cursor(7, 3);
        let before = e.cursor();
        run_keys(&mut e, "G");
        run_keys(&mut e, "``");
        assert_eq!(e.cursor(), before);
    }

    #[test]
    fn macro_record_and_replay_basic() {
        let mut e = editor_with("foo\nbar\nbaz");
        // Record into "a": insert "X" at line start, exit insert.
        run_keys(&mut e, "qaIX<Esc>jq");
        assert_eq!(e.buffer().lines()[0], "Xfoo");
        // Replay on the next two lines.
        run_keys(&mut e, "@a");
        assert_eq!(e.buffer().lines()[1], "Xbar");
        // @@ replays the last-played macro.
        run_keys(&mut e, "j@@");
        assert_eq!(e.buffer().lines()[2], "Xbaz");
    }

    #[test]
    fn macro_count_replays_n_times() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        // Record "j" — move down once.
        run_keys(&mut e, "qajq");
        assert_eq!(e.cursor().0, 1);
        // Replay 3 times via 3@a.
        run_keys(&mut e, "3@a");
        assert_eq!(e.cursor().0, 4);
    }

    #[test]
    fn macro_capital_q_appends_to_lowercase_register() {
        let mut e = editor_with("hello");
        run_keys(&mut e, "qall<Esc>q");
        run_keys(&mut e, "qAhh<Esc>q");
        // Macros + named registers share storage now: register `a`
        // holds the encoded keystrokes from both recordings.
        let text = e.registers().read('a').unwrap().text.clone();
        assert!(text.contains("ll<Esc>"));
        assert!(text.contains("hh<Esc>"));
    }

    #[test]
    fn buffer_selection_block_in_visual_block_mode() {
        use hjkl_buffer::{Position, Selection};
        let mut e = editor_with("aaaa\nbbbb\ncccc");
        run_keys(&mut e, "<C-v>jl");
        assert_eq!(
            e.buffer_selection(),
            Some(Selection::Block {
                anchor: Position::new(0, 0),
                head: Position::new(1, 1),
            })
        );
    }

    // ─── Audit batch: lock in known-good behaviour ───────────────────────

    #[test]
    fn n_after_question_mark_keeps_walking_backward() {
        // After committing a `?` search, `n` should continue in the
        // backward direction; `N` flips forward.
        let mut e = editor_with("foo bar foo baz foo end");
        e.jump_cursor(0, 22);
        run_keys(&mut e, "?foo<CR>");
        assert_eq!(e.cursor().1, 16);
        run_keys(&mut e, "n");
        assert_eq!(e.cursor().1, 8);
        run_keys(&mut e, "N");
        assert_eq!(e.cursor().1, 16);
    }

    #[test]
    fn nested_macro_chord_records_literal_keys() {
        // `qa@bq` should capture `@` and `b` as literal keys in `a`,
        // not as a macro-replay invocation. Replay then re-runs them.
        let mut e = editor_with("alpha\nbeta\ngamma");
        // First record `b` as a noop-ish macro: just `l` (move right).
        run_keys(&mut e, "qblq");
        // Now record `a` as: enter insert, type X, exit, then trigger
        // `@b` which should run the macro inline during recording too.
        run_keys(&mut e, "qaIX<Esc>q");
        // `@a` re-runs the captured key sequence on a different line.
        e.jump_cursor(1, 0);
        run_keys(&mut e, "@a");
        assert_eq!(e.buffer().lines()[1], "Xbeta");
    }

    #[test]
    fn shift_gt_motion_indents_one_line() {
        // `>w` over a single-line buffer should indent that line by
        // one shiftwidth — operator routes through the operator
        // pipeline like `dw` / `cw`.
        let mut e = editor_with("hello world");
        run_keys(&mut e, ">w");
        assert_eq!(e.buffer().lines()[0], "  hello world");
    }

    #[test]
    fn shift_lt_motion_outdents_one_line() {
        let mut e = editor_with("    hello world");
        run_keys(&mut e, "<lt>w");
        // Outdent strips up to one shiftwidth (default 2).
        assert_eq!(e.buffer().lines()[0], "  hello world");
    }

    #[test]
    fn shift_gt_text_object_indents_paragraph() {
        let mut e = editor_with("alpha\nbeta\ngamma\n\nrest");
        e.jump_cursor(0, 0);
        run_keys(&mut e, ">ip");
        assert_eq!(e.buffer().lines()[0], "  alpha");
        assert_eq!(e.buffer().lines()[1], "  beta");
        assert_eq!(e.buffer().lines()[2], "  gamma");
        // Blank separator + the next paragraph stay untouched.
        assert_eq!(e.buffer().lines()[4], "rest");
    }

    #[test]
    fn ctrl_o_runs_exactly_one_normal_command() {
        // `Ctrl-O dw` returns to insert after the single `dw`. A
        // second `Ctrl-O` is needed for another normal command.
        let mut e = editor_with("alpha beta gamma");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "i");
        e.handle_key(KeyEvent::new(KeyCode::Char('o'), KeyModifiers::CONTROL));
        run_keys(&mut e, "dw");
        // First `dw` ran in normal; we're back in insert.
        assert_eq!(e.vim_mode(), VimMode::Insert);
        // Typing a char now inserts.
        run_keys(&mut e, "X");
        assert_eq!(e.buffer().lines()[0], "Xbeta gamma");
    }

    #[test]
    fn macro_replay_respects_mode_switching() {
        // Recording `iX<Esc>0` should leave us in normal mode at col 0
        // after replay — the embedded Esc in the macro must drop the
        // replayed insert session.
        let mut e = editor_with("hi");
        run_keys(&mut e, "qaiX<Esc>0q");
        assert_eq!(e.vim_mode(), VimMode::Normal);
        // Replay on a fresh line.
        e.set_content("yo");
        run_keys(&mut e, "@a");
        assert_eq!(e.vim_mode(), VimMode::Normal);
        assert_eq!(e.cursor().1, 0);
        assert_eq!(e.buffer().lines()[0], "Xyo");
    }

    #[test]
    fn macro_recorded_text_round_trips_through_register() {
        // After the macros-in-registers unification, recording into
        // `a` writes the encoded keystroke text into register `a`'s
        // slot. `@a` decodes back to inputs and replays.
        let mut e = editor_with("");
        run_keys(&mut e, "qaiX<Esc>q");
        let text = e.registers().read('a').unwrap().text.clone();
        assert!(text.starts_with("iX"));
        // Replay inserts another X at the cursor.
        run_keys(&mut e, "@a");
        assert_eq!(e.buffer().lines()[0], "XX");
    }

    #[test]
    fn dot_after_macro_replays_macros_last_change() {
        // After `@a` runs a macro whose last mutation was an insert,
        // `.` should repeat that final change, not the whole macro.
        let mut e = editor_with("ab\ncd\nef");
        // Record: insert 'X' at line start, then move down. The last
        // mutation is the insert — `.` should re-apply just that.
        run_keys(&mut e, "qaIX<Esc>jq");
        assert_eq!(e.buffer().lines()[0], "Xab");
        run_keys(&mut e, "@a");
        assert_eq!(e.buffer().lines()[1], "Xcd");
        // `.` from the new cursor row repeats the last edit (the
        // insert `X`), not the whole macro (which would also `j`).
        let row_before_dot = e.cursor().0;
        run_keys(&mut e, ".");
        assert!(e.buffer().lines()[row_before_dot].starts_with('X'));
    }

    // ── smartindent tests ────────────────────────────────────────────────

    /// Build an editor with 4-space settings (expandtab, shiftwidth=4,
    /// softtabstop=4) for smartindent tests. Does NOT inherit the
    /// shiftwidth=2 override from `editor_with`.
    fn si_editor(content: &str) -> Editor {
        let opts = crate::types::Options {
            shiftwidth: 4,
            softtabstop: 4,
            expandtab: true,
            smartindent: true,
            autoindent: true,
            ..crate::types::Options::default()
        };
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            opts,
        );
        e.set_content(content);
        e
    }

    #[test]
    fn smartindent_bumps_indent_after_open_brace() {
        // "fn foo() {" + Enter → new line has 4 spaces of indent
        let mut e = si_editor("fn foo() {");
        e.jump_cursor(0, 10); // after the `{`
        run_keys(&mut e, "i<CR>");
        assert_eq!(
            e.buffer().lines()[1],
            "    ",
            "smartindent should bump one shiftwidth after {{"
        );
    }

    #[test]
    fn smartindent_no_bump_when_off() {
        // Same input but smartindent=false → just copies prev leading ws
        // (which is empty on "fn foo() {"), so new line is empty.
        let mut e = si_editor("fn foo() {");
        e.settings_mut().smartindent = false;
        e.jump_cursor(0, 10);
        run_keys(&mut e, "i<CR>");
        assert_eq!(
            e.buffer().lines()[1],
            "",
            "without smartindent, no bump: new line copies empty leading ws"
        );
    }

    #[test]
    fn smartindent_uses_tab_when_noexpandtab() {
        // noexpandtab + prev line ends in `{` → new line starts with `\t`
        let opts = crate::types::Options {
            shiftwidth: 4,
            softtabstop: 0,
            expandtab: false,
            smartindent: true,
            autoindent: true,
            ..crate::types::Options::default()
        };
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            opts,
        );
        e.set_content("fn foo() {");
        e.jump_cursor(0, 10);
        run_keys(&mut e, "i<CR>");
        assert_eq!(
            e.buffer().lines()[1],
            "\t",
            "noexpandtab: smartindent bump inserts a literal tab"
        );
    }

    #[test]
    fn smartindent_dedent_on_close_brace() {
        // Line is "    " (4 spaces), cursor at col 4, type `}` →
        // leading spaces stripped, `}` at col 0.
        let mut e = si_editor("fn foo() {");
        // Add a second line with only indentation.
        e.set_content("fn foo() {\n    ");
        e.jump_cursor(1, 4); // end of "    "
        run_keys(&mut e, "i}");
        assert_eq!(
            e.buffer().lines()[1],
            "}",
            "close brace on whitespace-only line should dedent"
        );
        assert_eq!(e.cursor(), (1, 1), "cursor should be after the `}}`");
    }

    #[test]
    fn smartindent_no_dedent_when_off() {
        // Same setup but smartindent=false → `}` appended normally.
        let mut e = si_editor("fn foo() {\n    ");
        e.settings_mut().smartindent = false;
        e.jump_cursor(1, 4);
        run_keys(&mut e, "i}");
        assert_eq!(
            e.buffer().lines()[1],
            "    }",
            "without smartindent, `}}` just appends at cursor"
        );
    }

    #[test]
    fn smartindent_no_dedent_mid_line() {
        // Line has "    let x = 1", cursor after `1`; type `}` → no
        // dedent because chars before cursor aren't all whitespace.
        let mut e = si_editor("    let x = 1");
        e.jump_cursor(0, 13); // after `1`
        run_keys(&mut e, "i}");
        assert_eq!(
            e.buffer().lines()[0],
            "    let x = 1}",
            "mid-line `}}` should not dedent"
        );
    }

    // ─── Vim-compat divergence fixes (issue #24) ─────────────────────

    // Fix #1: x/X populate the unnamed register.
    #[test]
    fn count_5x_fills_unnamed_register() {
        let mut e = editor_with("hello world\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "5x");
        assert_eq!(e.buffer().lines()[0], " world");
        assert_eq!(e.cursor(), (0, 0));
        assert_eq!(e.yank(), "hello");
    }

    #[test]
    fn x_fills_unnamed_register_single_char() {
        let mut e = editor_with("abc\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "x");
        assert_eq!(e.buffer().lines()[0], "bc");
        assert_eq!(e.yank(), "a");
    }

    #[test]
    fn big_x_fills_unnamed_register() {
        let mut e = editor_with("hello\n");
        e.jump_cursor(0, 3);
        run_keys(&mut e, "X");
        assert_eq!(e.buffer().lines()[0], "helo");
        assert_eq!(e.yank(), "l");
    }

    // Fix #2: G lands on last content row, not phantom trailing-empty row.
    #[test]
    fn g_motion_trailing_newline_lands_on_last_content_row() {
        let mut e = editor_with("foo\nbar\nbaz\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "G");
        // buffer is stored as ["foo","bar","baz",""] — G must land on row 2 ("baz").
        assert_eq!(
            e.cursor().0,
            2,
            "G should land on row 2 (baz), not row 3 (phantom empty)"
        );
    }

    // Fix #3: dd on last line clamps cursor to new last content row.
    #[test]
    fn dd_last_line_clamps_cursor_to_new_last_row() {
        let mut e = editor_with("foo\nbar\n");
        e.jump_cursor(1, 0);
        run_keys(&mut e, "dd");
        assert_eq!(e.buffer().lines()[0], "foo");
        assert_eq!(
            e.cursor(),
            (0, 0),
            "cursor should clamp to row 0 after dd on last content line"
        );
    }

    // Fix #4: d$ cursor lands on last char, not one past.
    #[test]
    fn d_dollar_cursor_on_last_char() {
        let mut e = editor_with("hello world\n");
        e.jump_cursor(0, 5);
        run_keys(&mut e, "d$");
        assert_eq!(e.buffer().lines()[0], "hello");
        assert_eq!(
            e.cursor(),
            (0, 4),
            "d$ should leave cursor on col 4, not col 5"
        );
    }

    // Fix #5: undo clamps cursor to last valid normal-mode col.
    #[test]
    fn undo_insert_clamps_cursor_to_last_valid_col() {
        let mut e = editor_with("hello\n");
        e.jump_cursor(0, 5); // one-past-last, as in oracle initial_cursor
        run_keys(&mut e, "a world<Esc>u");
        assert_eq!(e.buffer().lines()[0], "hello");
        assert_eq!(
            e.cursor(),
            (0, 4),
            "undo should clamp cursor to col 4 on 'hello'"
        );
    }

    // Fix #6: da" eats trailing whitespace when present.
    #[test]
    fn da_doublequote_eats_trailing_whitespace() {
        let mut e = editor_with("say \"hello\" there\n");
        e.jump_cursor(0, 6);
        run_keys(&mut e, "da\"");
        assert_eq!(e.buffer().lines()[0], "say there");
        assert_eq!(e.cursor().1, 4, "cursor should be at col 4 after da\"");
    }

    // Fix #7: daB cursor off-by-one — clamp to new last col.
    #[test]
    fn dab_cursor_col_clamped_after_delete() {
        let mut e = editor_with("fn x() {\n    body\n}\n");
        e.jump_cursor(1, 4);
        run_keys(&mut e, "daB");
        assert_eq!(e.buffer().lines()[0], "fn x() ");
        assert_eq!(
            e.cursor(),
            (0, 6),
            "daB should leave cursor at col 6, not 7"
        );
    }

    // Fix #8: diB preserves surrounding newlines on multi-line block.
    #[test]
    fn dib_preserves_surrounding_newlines() {
        let mut e = editor_with("{\n    body\n}\n");
        e.jump_cursor(1, 4);
        run_keys(&mut e, "diB");
        assert_eq!(e.buffer().lines()[0], "{");
        assert_eq!(e.buffer().lines()[1], "}");
        assert_eq!(e.cursor().0, 1, "cursor should be on the '}}' line");
    }

    #[test]
    fn is_chord_pending_tracks_replace_state() {
        let mut e = editor_with("abc\n");
        assert!(!e.is_chord_pending());
        // Press `r` — engine enters Pending::Replace.
        e.handle_key(KeyEvent::new(KeyCode::Char('r'), KeyModifiers::NONE));
        assert!(e.is_chord_pending(), "engine should be pending after r");
        // Press a char to complete — pending clears.
        e.handle_key(KeyEvent::new(KeyCode::Char('x'), KeyModifiers::NONE));
        assert!(
            !e.is_chord_pending(),
            "engine pending should clear after replace"
        );
    }

    // ─── Special marks `[` / `]` (vim `:h '[` / `:h ']`) ────────────────────

    #[test]
    fn yiw_sets_lbr_rbr_marks_around_word() {
        // `yiw` on "hello" — charwise exclusive range. `[` = col 0,
        // `]` = col 4 (last char of "hello").
        let mut e = editor_with("hello world");
        run_keys(&mut e, "yiw");
        let lo = e.mark('[').expect("'[' must be set after yiw");
        let hi = e.mark(']').expect("']' must be set after yiw");
        assert_eq!(lo, (0, 0), "'[ should be first char of yanked word");
        assert_eq!(hi, (0, 4), "'] should be last char of yanked word");
    }

    #[test]
    fn yj_linewise_sets_marks_at_line_edges() {
        // `yj` yanks 2 lines linewise. `[` = (0, 0), `]` = (1, last_col).
        // "bbbbb" is 5 chars — last_col = 4.
        let mut e = editor_with("aaaaa\nbbbbb\nccc");
        run_keys(&mut e, "yj");
        let lo = e.mark('[').expect("'[' must be set after yj");
        let hi = e.mark(']').expect("']' must be set after yj");
        assert_eq!(lo, (0, 0), "'[ snaps to (top_row, 0) for linewise yank");
        assert_eq!(
            hi,
            (1, 4),
            "'] snaps to (bot_row, last_col) for linewise yank"
        );
    }

    #[test]
    fn dd_sets_lbr_rbr_marks_to_cursor() {
        // `dd` on the first of two lines — post-delete cursor is row 0.
        // Both marks must park there (vim `:h '[` delete rule).
        let mut e = editor_with("aaa\nbbb");
        run_keys(&mut e, "dd");
        let lo = e.mark('[').expect("'[' must be set after dd");
        let hi = e.mark(']').expect("']' must be set after dd");
        assert_eq!(lo, hi, "after delete both marks are at the same position");
        assert_eq!(lo.0, 0, "post-delete cursor row should be 0");
    }

    #[test]
    fn dw_sets_lbr_rbr_marks_to_cursor() {
        // `dw` on "hello world" — deletes "hello ". Post-delete cursor
        // stays at col 0. Both marks land there.
        let mut e = editor_with("hello world");
        run_keys(&mut e, "dw");
        let lo = e.mark('[').expect("'[' must be set after dw");
        let hi = e.mark(']').expect("']' must be set after dw");
        assert_eq!(lo, hi, "after delete both marks are at the same position");
        assert_eq!(lo, (0, 0), "post-dw cursor is at col 0");
    }

    #[test]
    fn cw_then_esc_sets_lbr_at_start_rbr_at_inserted_text_end() {
        // `cw` on "hello world" → deletes "hello", enters insert, types
        // "foo", then Esc. `[` = start of change = (0,0). `]` = last
        // typed char = (0,2) ("foo" spans cols 0-2; cursor is at col 2
        // during finish_insert_session, before the Esc step-back).
        let mut e = editor_with("hello world");
        run_keys(&mut e, "cwfoo<Esc>");
        let lo = e.mark('[').expect("'[' must be set after cw");
        let hi = e.mark(']').expect("']' must be set after cw");
        assert_eq!(lo, (0, 0), "'[ should be start of change");
        // "foo" is 3 chars; cursor was at col 3 (past end) at finish_insert_session
        // before step-back. `]` = col 3 (the position during finish).
        assert_eq!(hi.0, 0, "'] should be on row 0");
        assert!(hi.1 >= 2, "'] should be at or past last char of 'foo'");
    }

    #[test]
    fn cw_with_no_insertion_sets_marks_at_change_start() {
        // `cw<Esc>` with no chars typed. Both marks land at the change
        // start (cursor parks at col 0 after cut).
        let mut e = editor_with("hello world");
        run_keys(&mut e, "cw<Esc>");
        let lo = e.mark('[').expect("'[' must be set after cw<Esc>");
        let hi = e.mark(']').expect("']' must be set after cw<Esc>");
        assert_eq!(lo.0, 0, "'[ should be on row 0");
        assert_eq!(hi.0, 0, "'] should be on row 0");
        // Both marks at the same position when nothing was typed.
        assert_eq!(lo, hi, "marks coincide when insert is empty");
    }

    #[test]
    fn p_charwise_sets_marks_around_pasted_text() {
        // `yiw` yanks "abc", then `p` pastes after the cursor.
        // `[` = first pasted char position, `]` = last pasted char.
        let mut e = editor_with("abc xyz");
        run_keys(&mut e, "yiw"); // yank "abc" (exclusive, last yanked = col 2)
        run_keys(&mut e, "p"); // paste after cursor (at col 1, the 'b')
        let lo = e.mark('[').expect("'[' set after charwise paste");
        let hi = e.mark(']').expect("']' set after charwise paste");
        assert!(lo <= hi, "'[ must not exceed ']'");
        // The pasted text is "abc" (3 chars). Marks bracket exactly 3 cols.
        assert_eq!(
            hi.1.wrapping_sub(lo.1),
            2,
            "'] - '[ should span 2 cols for a 3-char paste"
        );
    }

    #[test]
    fn p_linewise_sets_marks_at_line_edges() {
        // Yank 2 lines linewise (`yj`), paste below (`p`).
        // `[` = (target_row, 0), `]` = (target_row+1, last_col_of_second_line).
        let mut e = editor_with("aaa\nbbb\nccc");
        run_keys(&mut e, "yj"); // yank rows 0-1 linewise
        run_keys(&mut e, "j"); // cursor to row 1
        run_keys(&mut e, "p"); // paste below row 1
        let lo = e.mark('[').expect("'[' set after linewise paste");
        let hi = e.mark(']').expect("']' set after linewise paste");
        assert_eq!(lo.1, 0, "'[ col must be 0 for linewise paste");
        assert!(hi.0 > lo.0, "'] row must be below '[ row for 2-line paste");
        assert_eq!(hi.0 - lo.0, 1, "exactly 1 row gap for a 2-line payload");
    }

    #[test]
    fn backtick_lbr_v_backtick_rbr_reselects_yanked_text() {
        // Vim idiom: after `yiw`, `` `[v`] `` re-selects exactly the
        // yanked word in charwise visual. The marks must bracket the
        // yanked text end-to-end for this idiom to work.
        let mut e = editor_with("hello world");
        run_keys(&mut e, "yiw"); // yank "hello"
        // Jump to `[`, enter visual, jump to `]`.
        // run_keys uses backtick as a plain char in goto-mark-char path.
        run_keys(&mut e, "`[v`]");
        // Cursor should now be on col 4 (last char of "hello").
        assert_eq!(
            e.cursor(),
            (0, 4),
            "visual `[v`] should land on last yanked char"
        );
        // The mode should be Visual (selection active).
        assert_eq!(
            e.vim_mode(),
            crate::VimMode::Visual,
            "should be in Visual mode"
        );
    }

    // ── Vim-compat divergence regression tests (kryptic-sh/hjkl#83) ──────────

    /// Bug 1: `` `. `` after `iX<Esc>` should land at the *start* of the
    /// insert (col 0), not one past the last inserted char. vim's `:h '.`
    /// says the mark is the position where the last change was made.
    #[test]
    fn mark_dot_jump_to_last_edit_pre_edit_cursor() {
        // "hello\nworld\n", cursor (0,0). `iX<Esc>` inserts "X" at col 0;
        // dot mark should land on col 0 (change start), not col 1 (post-insert).
        let mut e = editor_with("hello\nworld\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "iX<Esc>j`.");
        assert_eq!(
            e.cursor(),
            (0, 0),
            "dot mark should jump to the change-start (col 0), not post-insert col"
        );
    }

    /// Bug 2: `100G` on a buffer with a trailing newline should clamp to the
    /// last content row, not land on the phantom empty row after the `\n`.
    #[test]
    fn count_100g_clamps_to_last_content_row() {
        // "foo\nbar\nbaz\n" has 4 rows in the buffer (row 3 is the phantom
        // empty row after the trailing \n). `100G` should land on row 2.
        let mut e = editor_with("foo\nbar\nbaz\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "100G");
        assert_eq!(
            e.cursor(),
            (2, 0),
            "100G on trailing-newline buffer must clamp to row 2 (last content row)"
        );
    }

    /// Bug 3: `gi` should return to the row *and* column where insert mode
    /// was last active (the pre-step-back position), then enter insert.
    #[test]
    fn gi_resumes_last_insert_position() {
        // "world\nhello\n", cursor (0,0).
        // `iHi<Esc>` inserts "Hi" at (0,0); Esc steps back to (0,1).
        // `j` moves to row 1. `gi` should jump back to (0,2) — the position
        // that was live during insert — and enter insert. `<Esc>` then steps
        // back to (0,1), leaving the cursor at (0,1) in Normal mode.
        let mut e = editor_with("world\nhello\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "iHi<Esc>jgi<Esc>");
        assert_eq!(
            e.vim_mode(),
            crate::VimMode::Normal,
            "should be in Normal mode after gi<Esc>"
        );
        assert_eq!(
            e.cursor(),
            (0, 1),
            "gi<Esc> cursor should be at (0,1) — the insert row, step-back col"
        );
    }

    /// Bug 4: `<C-v>jlc<text><Esc>` — after blockwise change the cursor
    /// should sit on the last char of the inserted text (`col 1` for "ZZ"),
    /// not at the block start (`col 0`). Buffer result must still be correct.
    #[test]
    fn visual_block_change_cursor_on_last_inserted_char() {
        // "foo\nbar\nbaz\n", cursor (0,0). Block covers rows 0-1, cols 0-1.
        // `cZZ` replaces cols 0-1 on each row with "ZZ". Buffer becomes
        // "ZZo\nZZr\nbaz\n". Cursor should be at (0,1) — last char of "ZZ".
        let mut e = editor_with("foo\nbar\nbaz\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "<C-v>jlcZZ<Esc>");
        let lines = e.buffer().lines().to_vec();
        assert_eq!(lines[0], "ZZo", "row 0 should be 'ZZo'");
        assert_eq!(lines[1], "ZZr", "row 1 should be 'ZZr'");
        assert_eq!(
            e.cursor(),
            (0, 1),
            "cursor should be on last char of inserted 'ZZ' (col 1)"
        );
    }

    /// Bug 5: `"_dw` (black-hole delete) must not overwrite the unnamed
    /// register. After `yiw` the unnamed register holds "foo". A subsequent
    /// `"_dw` discards "bar " into the void, leaving "foo" intact. `b p`
    /// then pastes "foo" to produce "ffoooo baz\n".
    #[test]
    fn register_blackhole_delete_preserves_unnamed_register() {
        // "foo bar baz\n", cursor (0,0).
        // `yiw` — yank "foo" into " and "0.
        // `w`   — cursor to (0,4) = 'b'.
        // `"_dw` — black-hole delete "bar "; unnamed must still be "foo".
        // `b`   — back to (0,0).
        // `p`   — paste "foo" after 'f' → "ffoooo baz\n".
        let mut e = editor_with("foo bar baz\n");
        e.jump_cursor(0, 0);
        run_keys(&mut e, "yiww\"_dwbp");
        let lines = e.buffer().lines().to_vec();
        assert_eq!(
            lines[0], "ffoooo baz",
            "black-hole delete must not corrupt unnamed register"
        );
        assert_eq!(
            e.cursor(),
            (0, 3),
            "cursor should be on last pasted char (col 3)"
        );
    }

    // ── after_z controller API (Phase 2b-iii) ───────────────────────────────

    #[test]
    fn after_z_zz_sets_viewport_pinned() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        e.jump_cursor(2, 0);
        e.after_z('z', 1);
        assert!(e.vim.viewport_pinned, "zz must set viewport_pinned");
    }

    #[test]
    fn after_z_zo_opens_fold_at_cursor() {
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(1, 2, true);
        e.jump_cursor(1, 0);
        e.after_z('o', 1);
        assert!(
            !e.buffer().folds()[0].closed,
            "zo must open the fold at the cursor row"
        );
    }

    #[test]
    fn after_z_zm_closes_all_folds() {
        let mut e = editor_with("a\nb\nc\nd\ne\nf");
        e.buffer_mut().add_fold(0, 1, false);
        e.buffer_mut().add_fold(4, 5, false);
        e.after_z('M', 1);
        assert!(
            e.buffer().folds().iter().all(|f| f.closed),
            "zM must close all folds"
        );
    }

    #[test]
    fn after_z_zd_removes_fold_at_cursor() {
        let mut e = editor_with("a\nb\nc\nd");
        e.buffer_mut().add_fold(1, 2, true);
        e.jump_cursor(1, 0);
        e.after_z('d', 1);
        assert!(
            e.buffer().folds().is_empty(),
            "zd must remove the fold at the cursor row"
        );
    }

    #[test]
    fn after_z_zf_in_visual_creates_fold() {
        let mut e = editor_with("a\nb\nc\nd\ne");
        // Enter visual mode spanning rows 1..=3.
        e.jump_cursor(1, 0);
        run_keys(&mut e, "V2j");
        // Now call after_z('f') — reads visual mode + anchors internally.
        e.after_z('f', 1);
        let folds = e.buffer().folds();
        assert_eq!(folds.len(), 1, "zf in visual must create exactly one fold");
        assert_eq!(folds[0].start_row, 1);
        assert_eq!(folds[0].end_row, 3);
        assert!(folds[0].closed);
    }

    // ── apply_op_motion_key / apply_op_double / enter_op_* unit tests ─────────

    #[test]
    fn apply_op_motion_dw_deletes_word() {
        // "hello world" — dw should delete "hello ".
        let mut e = editor_with("hello world");
        e.apply_op_motion(crate::vim::Operator::Delete, 'w', 1);
        assert_eq!(
            e.buffer().lines().first().cloned().unwrap_or_default(),
            "world"
        );
    }

    #[test]
    fn apply_op_motion_cw_quirk_leaves_trailing_space() {
        // "hello world" — cw uses ce quirk: deletes "hello" not "hello ".
        let mut e = editor_with("hello world");
        e.apply_op_motion(crate::vim::Operator::Change, 'w', 1);
        // After ce, cursor is at 0; mode enters Insert. Line should be " world"
        // (trailing space from original gap preserved).
        let line = e.buffer().lines().first().cloned().unwrap_or_default();
        assert!(
            line.starts_with(' ') || line == " world",
            "cw quirk: got {line:?}"
        );
        assert_eq!(e.vim_mode(), VimMode::Insert);
    }

    #[test]
    fn apply_op_double_dd_deletes_line() {
        let mut e = editor_with("line1\nline2\nline3");
        // dd on first line.
        e.apply_op_double(crate::vim::Operator::Delete, 1);
        let lines: Vec<_> = e.buffer().lines().to_vec();
        assert_eq!(lines, vec!["line2", "line3"], "dd should delete line1");
    }

    #[test]
    fn apply_op_double_yy_does_not_modify_buffer() {
        let mut e = editor_with("hello");
        e.apply_op_double(crate::vim::Operator::Yank, 1);
        assert_eq!(
            e.buffer().lines().first().cloned().unwrap_or_default(),
            "hello"
        );
    }

    #[test]
    fn enter_op_text_obj_sets_pending() {
        let mut e = editor_with("hello world");
        e.enter_op_text_obj(crate::vim::Operator::Delete, 1, true);
        assert!(e.is_chord_pending(), "OpTextObj should set chord pending");
    }

    #[test]
    fn enter_op_g_sets_pending() {
        let mut e = editor_with("hello world");
        e.enter_op_g(crate::vim::Operator::Delete, 1);
        assert!(e.is_chord_pending(), "OpG should set chord pending");
    }

    #[test]
    fn enter_op_find_sets_pending() {
        let mut e = editor_with("hello world");
        e.enter_op_find(crate::vim::Operator::Delete, 1, true, false);
        assert!(e.is_chord_pending(), "OpFind should set chord pending");
    }

    #[test]
    fn apply_op_double_dd_count2_deletes_two_lines() {
        let mut e = editor_with("line1\nline2\nline3");
        e.apply_op_double(crate::vim::Operator::Delete, 2);
        let lines: Vec<_> = e.buffer().lines().to_vec();
        assert_eq!(lines, vec!["line3"], "2dd should delete two lines");
    }

    #[test]
    fn apply_op_motion_unknown_key_is_noop() {
        // A key that parse_motion returns None for — should be a no-op.
        let mut e = editor_with("hello");
        let before = e.cursor();
        e.apply_op_motion(crate::vim::Operator::Delete, 'X', 1); // 'X' is not a motion
        assert_eq!(e.cursor(), before);
        assert_eq!(
            e.buffer().lines().first().cloned().unwrap_or_default(),
            "hello"
        );
    }
}