kimun-notes 0.18.0

//! Built-in vim emulation: a modal input interpreter over a `TextArea`.
//! Pure over `&mut TextArea` — no component state, no async (adr/0012).

use super::snapshot::EditorMode;
use ratatui::crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
use ratatui_textarea::{CursorMove, TextArea};

/// Screen-level actions the host performs on the engine's behalf (adr/0012).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VimHostAction {
    OpenPalette,                  // `:`
    OpenSearch { forward: bool }, // `/` (true) `?` (false)
    SearchNext,                   // `n`
    SearchPrev,                   // `N`
}

/// What a key did, so the host can bump the right revision counters.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VimKeyOutcome {
    /// Buffer text changed — host calls `bump_content()`.
    TextMutated,
    /// Only the cursor/selection moved — host refreshes view, not content.
    CursorOnly,
    /// Nothing happened (unmapped key in Normal mode).
    NoOp,
    /// Insert mode: defer to the existing `handle_textarea_key` path.
    PassThrough,
    /// The host must perform a screen-level action.
    Host(VimHostAction),
}

// ── Reified command model (adr/0011) ────────────────────────────────────────

/// A cursor motion. Operators consume a motion to form a range.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Motion {
    Left,
    Right,
    Up,
    Down,
    WordForward,
    WordBack,
    WordEnd,
    WordForwardBig,            // W — WORD: any non-blank run
    WordBackBig,               // B
    WordEndBig,                // E
    WordEndBack { big: bool }, // ge / gE
    LineStart,
    FirstNonBlank,
    LastNonBlank, // g_
    LineEnd,
    FileStart,
    FileEnd,
    GotoLine(usize), // 5gg / 5G (1-based)
    ParagraphForward,
    ParagraphBack,
    MatchingPair,                                     // %
    FindChar { ch: char, till: bool, forward: bool }, // f/F/t/T
}

/// An operator awaiting a motion or text object.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Operator {
    Delete,
    Change,
    Yank,
    Indent,
    Outdent,
    Lowercase,  // gu
    Uppercase,  // gU
    ToggleCase, // g~
}

/// How a motion forms an operator range (vim `:h exclusive`).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum SpanKind {
    /// Half-open `[start, end)` char range.
    Exclusive,
    /// Includes the char at `end` (`[start, end]`).
    Inclusive,
    /// Whole lines from `start.row` through `end.row`.
    Linewise,
}

/// A text object (`iw`, `a"`, …).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TextObject {
    Word {
        around: bool,
    },
    Pair {
        open: char,
        close: char,
        around: bool,
    },
    Quote {
        ch: char,
        around: bool,
    },
}

/// Where an insert-entry command places the cursor before entering Insert.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum InsertEntry {
    Here,      // i
    After,     // a
    LineStart, // I
    LineEnd,   // A
    OpenBelow, // o
    OpenAbove, // O
}

/// The fully-parsed unit of work (adr/0011). `apply` is the only door that
/// mutates the buffer; dot-repeat (and future macros) replay these values
/// through that same door, so first press and replay cannot diverge.
#[derive(Debug, Clone)]
pub enum Command {
    Move(Motion, usize),
    OperateMotion(Operator, Motion, usize),      // e.g. 2dw
    OperateLine(Operator, usize),                // dd / cc / yy with count
    OperateObject(Operator, TextObject),         // diw, ci"
    OperateToLineEnd(Operator),                  // D / C / Y
    IndentLines { outdent: bool, count: usize }, // >> / <<
    DeleteChar { forward: bool, count: usize },  // x / X
    ReplaceChar(char),                           // r<ch>
    SubstituteChar(usize),                       // s
    SubstituteLine,                              // S
    JoinLines { count: usize, spaced: bool },    // J (spaced) / gJ (raw)
    ToggleCase(usize),                           // ~
    Paste { after: bool, count: usize },         // p / P
    Undo(usize),                                 // u
    Redo(usize),                                 // Ctrl-r
    EnterInsert(InsertEntry),                    // i a I A o O
    EnterReplace,                                // R — overwrite until Esc
    EnterVisual { line: bool },                  // v / V
    Repeat,                                      // .
}

/// One key of the g-command grammar (the key AFTER a pending `g`). Produced
/// by `g_key_for`, consumed by both the Normal parser and the Visual handler.
enum GKey {
    /// `gg` — file start, or line N when a count is pending.
    GotoLine,
    /// `ge` / `gE` / `g_` — plain motions.
    Motion(Motion),
    /// `gu` / `gU` / `g~` — case operators.
    CaseOp(Operator),
    /// `gJ` — join without space handling.
    Join,
}

/// What one Normal-mode key parsed into. Parsing never touches the buffer;
/// `Cmd` is the only variant that leads to mutation — via `apply`.
enum Parsed {
    /// Accumulated pending state; wait for more keys.
    Pending,
    Cmd(Command),
    Host(VimHostAction),
    /// Esc — pending state cleared, host-side selection cleanup applies.
    Cancel,
    /// Unmapped key.
    Nothing,
}

// ── Pending-state helper types ───────────────────────────────────────────────

#[derive(Debug, Clone, Copy)]
struct PendingFind {
    operator: Option<Operator>,
    till: bool,
    forward: bool,
}

/// A one-key continuation: the parser saw a prefix and waits for exactly one
/// more key. One field holds them all, so every ceremony site (clear,
/// space_leads, the footer hint) checks a single state instead of a drifting
/// list of flags — and a future `q`/`"`/`m` prefix is one new variant.
#[derive(Debug, Clone, Copy)]
enum Awaiting {
    /// `g` — the g-command grammar (`g_key_for`).
    G,
    /// `r` — the replacement char.
    ReplaceChar,
    /// `f`/`F`/`t`/`T` — the find target (the operator was captured at entry).
    Find(PendingFind),
    /// `i`/`a` after an operator (or in charwise Visual) — the object key.
    ObjectScope { around: bool },
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum RegisterKind {
    Charwise,
    Linewise,
}

/// One register's value — content and kind live together so they cannot
/// desync (adr/0011: the register is internal vim state, kept separate from
/// the textarea's yank buffer and the OS clipboard).
#[derive(Debug, Clone)]
struct RegisterValue {
    text: String,
    kind: RegisterKind,
}

/// The engine-owned register file. Only the unnamed register exists today;
/// named registers (v2) add a map alongside without touching operator code.
#[derive(Debug, Default)]
struct Registers {
    unnamed: Option<RegisterValue>,
}

impl Registers {
    /// Vim rule: every yank AND every delete/change fills the unnamed
    /// register. Empty text never overwrites it (a no-op delete keeps the
    /// previous content, matching vim).
    fn fill(&mut self, text: String, kind: RegisterKind) {
        if text.is_empty() {
            return;
        }
        self.unnamed = Some(RegisterValue { text, kind });
    }

    fn read(&self) -> Option<&RegisterValue> {
        self.unnamed.as_ref()
    }
}

#[derive(Debug, Clone)]
struct Change {
    command: Command,
    inserted: Option<String>,
}

#[derive(Debug, Clone)]
struct InsertCapture {
    command: Command,
    start: (usize, usize),
}

// ── VimEngine ────────────────────────────────────────────────────────────────

/// Modal vim state layered over the textarea buffer.
#[derive(Debug)]
pub struct VimEngine {
    mode: EditorMode,
    // pending-state + dot-repeat fields
    pending_count: Option<usize>,
    /// Count typed BEFORE the operator (`2` in `2d3w`); multiplied with the
    /// motion count at completion (vim: `2d3w` deletes 6 words).
    pending_op_count: Option<usize>,
    pending_operator: Option<Operator>,
    /// The one-key continuation the parser is waiting on (g-prefix, find
    /// target, replace char, object key) — mutually exclusive by type.
    awaiting: Option<Awaiting>,
    last_find: Option<(char, bool, bool)>, // (ch, till, forward) for ; and ,
    registers: Registers,
    /// The last mutating command + captured insert delta, for `.` (adr/0011).
    last_change: Option<Change>,
    /// While in Insert via a vim command, the text typed is accumulated here
    /// (resulting delta) so `.` can replay it.
    insert_capture: Option<InsertCapture>,
    /// Replace mode's restore stack: what each overwritten position held
    /// (`None` = the char was appended past EOL). Backspace pops it.
    replace_stack: Vec<Option<char>>,
}

impl Default for VimEngine {
    fn default() -> Self {
        Self {
            mode: EditorMode::Normal,
            pending_count: None,
            pending_op_count: None,
            pending_operator: None,
            awaiting: None,
            last_find: None,
            registers: Registers::default(),
            last_change: None,
            insert_capture: None,
            replace_stack: Vec::new(),
        }
    }
}

impl VimEngine {
    pub fn mode(&self) -> &EditorMode {
        &self.mode
    }

    /// Footer label for the current mode (e.g. "NORMAL").
    pub fn mode_label(&self) -> String {
        self.mode.label().to_string()
    }

    /// The in-progress command sequence, for the footer hint (e.g. "2d", "f").
    /// Returns `None` when nothing is pending (no display needed).
    pub fn pending_hint(&self) -> Option<String> {
        // Fast path: nothing pending — skip all allocation (common idle-frame case).
        if self.pending_count.is_none()
            && self.pending_op_count.is_none()
            && self.pending_operator.is_none()
            && self.awaiting.is_none()
        {
            return None;
        }
        let mut s = String::new();
        if let Some(n) = self.pending_op_count {
            s.push_str(&n.to_string());
        }
        if let Some(op) = self.pending_operator {
            s.push_str(match op {
                Operator::Delete => "d",
                Operator::Change => "c",
                Operator::Yank => "y",
                Operator::Indent => ">",
                Operator::Outdent => "<",
                Operator::Lowercase => "gu",
                Operator::Uppercase => "gU",
                Operator::ToggleCase => "g~",
            });
        }
        if let Some(n) = self.pending_count {
            s.push_str(&n.to_string());
        }
        match self.awaiting {
            Some(Awaiting::G) => s.push('g'),
            Some(Awaiting::ReplaceChar) => s.push('r'),
            Some(Awaiting::Find(pf)) => s.push(match (pf.till, pf.forward) {
                (false, true) => 'f',
                (false, false) => 'F',
                (true, true) => 't',
                (true, false) => 'T',
            }),
            Some(Awaiting::ObjectScope { around }) => s.push(if around { 'a' } else { 'i' }),
            None => {}
        }
        if s.is_empty() { None } else { Some(s) }
    }

    pub fn reset_to_normal(&mut self) {
        self.mode = EditorMode::Normal;
        self.clear_pending();
        // A capture from an interrupted Insert (e.g. note switch mid-`cw`)
        // must not survive: execute() skips dot-recording while one is live,
        // which would silently disable `.` for every later change.
        self.insert_capture = None;
    }

    /// Reconcile mode after a host-driven selection change (mouse). A live
    /// selection means Visual; losing the selection in Visual returns to Normal.
    pub fn sync_mouse_selection(&mut self, has_selection: bool) {
        match (has_selection, &self.mode) {
            (true, EditorMode::Normal) => self.mode = EditorMode::Visual,
            (false, EditorMode::Visual) | (false, EditorMode::VisualLine) => {
                self.mode = EditorMode::Normal
            }
            _ => {}
        }
    }

    /// True when a bare Space should start the leader: Normal mode, nothing
    /// pending (so `d<Space>`, `f<Space>`, counts etc. still take Space as an
    /// argument/motion, not the leader).
    pub fn space_leads(&self) -> bool {
        self.mode == EditorMode::Normal
            && self.pending_count.is_none()
            && self.pending_op_count.is_none()
            && self.pending_operator.is_none()
            && self.awaiting.is_none()
    }

    /// Interpret one key. In Insert mode everything except `Esc` is
    /// `PassThrough` (the host runs the existing direct textarea path).
    /// In Visual/VisualLine mode, motions extend the selection; operators
    /// act on the live selection. In Normal mode, motions move the cursor
    /// and the insert-entry keys switch to Insert mode.
    pub fn handle_key(&mut self, key: &KeyEvent, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        match self.mode {
            EditorMode::Insert => self.handle_insert(key, ta),
            EditorMode::Replace => self.handle_replace(key, ta),
            EditorMode::Visual | EditorMode::VisualLine => self.handle_visual(key, ta),
            _ => self.handle_normal(key, ta),
        }
    }

    // ── Visual + Visual-line mode handler ────────────────────────────────────

    fn handle_visual(&mut self, key: &KeyEvent, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        // One-key continuations consume the next key first: the find target
        // (`vf,` extends through the ','), and the object key after `i`/`a`
        // (`vi(` re-aims the selection at the object). The g continuation is
        // resolved below where the full key context is available.
        match self.awaiting {
            Some(Awaiting::Find(pf)) => {
                self.awaiting = None;
                if let KeyCode::Char(ch) = key.code {
                    self.last_find = Some((ch, pf.till, pf.forward));
                    let cnt = self.take_count();
                    let motion = Motion::FindChar {
                        ch,
                        till: pf.till,
                        forward: pf.forward,
                    };
                    self.apply_motion(motion, cnt, ta);
                    return VimKeyOutcome::CursorOnly;
                }
                self.clear_pending();
                return VimKeyOutcome::NoOp;
            }
            Some(Awaiting::ObjectScope { around }) => {
                self.awaiting = None;
                if let KeyCode::Char(ch) = key.code
                    && let Some(obj) = Self::object_for_char(ch, around)
                {
                    Self::select_object_visual(obj, ta);
                    self.clear_pending();
                    return VimKeyOutcome::CursorOnly;
                }
                self.clear_pending();
                return VimKeyOutcome::NoOp;
            }
            _ => {}
        }

        // Esc: cancel selection and return to Normal.
        if key.code == KeyCode::Esc {
            ta.cancel_selection();
            self.mode = EditorMode::Normal;
            self.clear_pending();
            return VimKeyOutcome::CursorOnly;
        }

        // Arrow keys: extend the selection.
        let plain = key.modifiers == KeyModifiers::NONE || key.modifiers == KeyModifiers::SHIFT;
        let KeyCode::Char(c) = key.code else {
            match key.code {
                KeyCode::Left => {
                    ta.move_cursor(CursorMove::Back);
                    return VimKeyOutcome::CursorOnly;
                }
                KeyCode::Right => {
                    ta.move_cursor(CursorMove::Forward);
                    return VimKeyOutcome::CursorOnly;
                }
                KeyCode::Up => {
                    ta.move_cursor(CursorMove::Up);
                    return VimKeyOutcome::CursorOnly;
                }
                KeyCode::Down => {
                    ta.move_cursor(CursorMove::Down);
                    return VimKeyOutcome::CursorOnly;
                }
                _ => return VimKeyOutcome::NoOp,
            }
        };
        if !plain {
            return VimKeyOutcome::NoOp;
        }

        // Count accumulation.
        if self.accumulate_count(c) {
            return VimKeyOutcome::NoOp;
        }

        // Operators act on the EXISTING live selection (already started by v/V).
        // In VisualLine mode: use linewise deletion (preserves newlines correctly).
        // In Visual mode: use charwise cut on the current selection.
        let op = match c {
            'd' | 'x' => Some(Operator::Delete),
            'c' | 's' => Some(Operator::Change),
            'y' => Some(Operator::Yank),
            // vim visual case ops. `~` stays on the auto-surround
            // PassThrough path below (kimün wraps the selection instead).
            'u' => Some(Operator::Lowercase),
            'U' => Some(Operator::Uppercase),
            _ => None,
        };
        if let Some(op) = op {
            return self.visual_operate(op, ta);
        }

        // 'p'/'P': replace the current visual selection with the register.
        // The register is engine-owned, so the cut below cannot clobber it.
        if c == 'p' || c == 'P' {
            let Some(reg) = self.registers.read().cloned() else {
                ta.cancel_selection();
                self.mode = EditorMode::Normal;
                return VimKeyOutcome::CursorOnly;
            };
            let text = reg.text;
            if self.mode == EditorMode::VisualLine {
                // VisualLine: delete the selected whole lines, then paste the
                // saved content. The delete fills the register with the deleted
                // lines — vim swap behavior — while `text` keeps the original.
                let (start_row, end_row) = if let Some(((sr, _), (er, _))) = ta.selection_range() {
                    (sr, er)
                } else {
                    let (r, _) = super::cursor_tuple(ta);
                    (r, r)
                };
                ta.cancel_selection();
                ta.move_cursor(CursorMove::Jump(start_row as u16, 0));
                let count = end_row - start_row + 1;
                self.apply_operator_linewise(Operator::Delete, count, None, ta);
                let body = text.strip_suffix('\n').unwrap_or(&text);
                ta.move_cursor(CursorMove::Head);
                ta.insert_str(body);
                ta.insert_newline();
                ta.move_cursor(CursorMove::Up);
            } else {
                // Charwise: make an inclusive selection, delete it, and fill
                // the register with the deleted text (vim swap: the replaced
                // selection enters the register), then insert the saved `text`.
                if let Some((start, end)) = ta.selection_range() {
                    ta.cancel_selection();
                    Self::select_range(ta, start, end, true);
                }
                ta.cut(); // cursor lands at the deletion gap
                self.fill_from_textarea(ta, RegisterKind::Charwise);
                // Record where the paste starts so we can leave the cursor there
                // (vim visual-p leaves cursor at the start of the pasted text).
                let paste_start = super::cursor_tuple(ta);
                ta.insert_str(&text); // insert the SAVED content, not the yank buffer
                ta.move_cursor(CursorMove::Jump(paste_start.0 as u16, paste_start.1 as u16));
            }
            self.mode = EditorMode::Normal;
            self.clear_pending();
            return VimKeyOutcome::TextMutated;
        }

        // 'o': swap cursor and anchor (vim: move to the other end of the
        // selection so it can be extended from there).
        if c == 'o' {
            if let Some((start, end)) = ta.selection_range() {
                let cur = super::cursor_tuple(ta);
                let other = if cur == end { start } else { end };
                ta.cancel_selection();
                ta.move_cursor(CursorMove::Jump(cur.0 as u16, cur.1 as u16));
                ta.start_selection();
                ta.move_cursor(CursorMove::Jump(other.0 as u16, other.1 as u16));
            }
            return VimKeyOutcome::CursorOnly;
        }

        // Visual `>`/`<` — indent/outdent the selected line range.
        if c == '>' || c == '<' {
            let outdent = c == '<';
            let line_count = if let Some(((sr, _), (er, _))) = ta.selection_range() {
                er.saturating_sub(sr) + 1
            } else {
                1
            };
            // Cancel selection; jump to first selected row; then indent.
            let start_row = if let Some(((sr, _), _)) = ta.selection_range() {
                sr
            } else {
                super::cursor_tuple(ta).0
            };
            ta.cancel_selection();
            ta.move_cursor(CursorMove::Jump(start_row as u16, 0));
            self.indent_lines(outdent, line_count, ta);
            self.mode = EditorMode::Normal;
            self.clear_pending();
            return VimKeyOutcome::TextMutated;
        }

        // Pair chars: set Normal and return PassThrough so the host's existing
        // auto-surround path wraps the selection. Skipped while a `g` is
        // pending — `g~` (case toggle) must reach the g-block below.
        if !matches!(self.awaiting, Some(Awaiting::G))
            && matches!(
                c,
                '(' | '[' | '{' | '<' | '"' | '\'' | '`' | '*' | '_' | '~'
            )
        {
            self.mode = EditorMode::Normal;
            return VimKeyOutcome::PassThrough;
        }

        // g prefix — the same shared g-command grammar as Normal mode,
        // dispatched against the selection. Case ops run on the selection
        // (bare `~` belongs to auto-surround in kimün, so g~ is the visual
        // toggle-case key); gJ joins the selected lines raw.
        if c == 'g' && !matches!(self.awaiting, Some(Awaiting::G)) {
            self.awaiting = Some(Awaiting::G);
            return VimKeyOutcome::NoOp;
        }
        if matches!(self.awaiting, Some(Awaiting::G)) {
            self.awaiting = None;
            return match Self::g_key_for(c) {
                Some(GKey::GotoLine) => {
                    let m = match self.pending_count.take() {
                        Some(n) => Motion::GotoLine(n),
                        None => Motion::FileStart,
                    };
                    self.apply_motion(m, 1, ta);
                    self.clear_pending();
                    VimKeyOutcome::CursorOnly
                }
                Some(GKey::Motion(m)) => {
                    let cnt = self.take_count();
                    self.apply_motion(m, cnt, ta);
                    self.clear_pending();
                    VimKeyOutcome::CursorOnly
                }
                Some(GKey::CaseOp(op)) => self.visual_operate(op, ta),
                Some(GKey::Join) => self.visual_join(false, ta),
                None => {
                    self.clear_pending();
                    VimKeyOutcome::NoOp
                }
            };
        }

        // J: join the selected lines with vim's space handling.
        if c == 'J' {
            return self.visual_join(true, ta);
        }

        // f/F/t/T: pend a selection-extending find.
        if let Some((till, forward)) = Self::find_spec_for(c) {
            self.awaiting = Some(Awaiting::Find(PendingFind {
                operator: None,
                till,
                forward,
            }));
            return VimKeyOutcome::NoOp;
        }

        // ; and , repeat the last find, extending the selection.
        if c == ';' || c == ',' {
            if let Some(motion) = self.repeat_find_motion(c) {
                let cnt = self.take_count();
                self.apply_motion(motion, cnt, ta);
            }
            self.clear_pending();
            return VimKeyOutcome::CursorOnly;
        }

        // i/a: text-object selection (charwise Visual only — `vi(`, `va"`).
        if (c == 'i' || c == 'a') && self.mode == EditorMode::Visual {
            self.awaiting = Some(Awaiting::ObjectScope { around: c == 'a' });
            return VimKeyOutcome::NoOp;
        }

        // Motions extend the selection. 5G extends to line 5 (count = line
        // number, matching the Normal-mode parser); the count is only
        // consumed for 'G' — every other motion keeps it as a repeat.
        if let Some(m) = Self::motion_for_char(c) {
            let m = if c == 'G' {
                match self.pending_count.take() {
                    Some(n) => Motion::GotoLine(n),
                    None => m,
                }
            } else {
                m
            };
            let count = self.take_count();
            self.apply_motion(m, count, ta);
            self.clear_pending();
            return VimKeyOutcome::CursorOnly;
        }

        self.clear_pending();
        VimKeyOutcome::NoOp
    }

    /// Visual `J` / `gJ`: join all selected lines into one (vim), then
    /// return to Normal mode.
    fn visual_join(&mut self, spaced: bool, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        let (start_row, end_row) = if let Some(((sr, _), (er, _))) = ta.selection_range() {
            (sr, er)
        } else {
            let (r, _) = super::cursor_tuple(ta);
            (r, r)
        };
        ta.cancel_selection();
        ta.move_cursor(CursorMove::Jump(start_row as u16, 0));
        let joins = end_row.saturating_sub(start_row).max(1);
        for _ in 0..joins {
            Self::join_line(ta, spaced);
        }
        self.mode = EditorMode::Normal;
        self.clear_pending();
        VimKeyOutcome::TextMutated
    }

    /// Apply `op` to the live visual selection (charwise or linewise) and
    /// leave Visual mode. Shared by the visual operator keys (d/x/c/s/y/u/U)
    /// and `g~`.
    fn visual_operate(&mut self, op: Operator, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        if self.mode == EditorMode::VisualLine {
            // VisualLine: operate on whole selected lines, preserving newlines.
            let (start_row, end_row) = if let Some(((sr, _), (er, _))) = ta.selection_range() {
                (sr, er)
            } else {
                let (r, _) = super::cursor_tuple(ta);
                (r, r)
            };
            // Cancel the current selection so apply_operator_linewise can
            // re-anchor from the correct start row.
            ta.cancel_selection();
            ta.move_cursor(CursorMove::Jump(start_row as u16, 0));
            let count = end_row - start_row + 1;
            self.apply_operator_linewise(op, count, None, ta);
        } else {
            // Charwise Visual: vim selection is inclusive of the char under
            // the cursor — re-select through select_range's inclusive end.
            let range = ta.selection_range();
            if let Some((start, end)) = range {
                ta.cancel_selection();
                Self::select_range(ta, start, end, true);
            }
            if op == Operator::Change {
                // Honest dot-repeat: `.` after a visual change replays a
                // same-sized change from the cursor (vim semantics) —
                // chars on one row, whole lines across rows.
                let capture_cmd = match range {
                    Some(((sr, sc), (er, ec))) if sr == er => Command::OperateMotion(
                        Operator::Change,
                        Motion::Right,
                        ec.saturating_sub(sc) + 1,
                    ),
                    Some(((sr, _), (er, _))) => {
                        Command::OperateLine(Operator::Change, er.saturating_sub(sr) + 1)
                    }
                    None => Command::OperateMotion(Operator::Change, Motion::Right, 1),
                };
                ta.cut();
                self.fill_from_textarea(ta, RegisterKind::Charwise);
                self.finish_insert_entry(&capture_cmd, None, ta);
            } else {
                self.apply_operator_on_selection(op, ta);
            }
        }
        // Change paths own the Insert transition (via the insert capture);
        // everything else returns to Normal here — one writer per transition.
        if op != Operator::Change {
            self.mode = EditorMode::Normal;
        }
        self.clear_pending();
        Self::outcome_for(op)
    }

    /// Re-aim the charwise visual selection at the text object under the
    /// cursor. The selection end is left ON the object's last char (visual
    /// selections are inclusive; the operator's inclusive `+1` restores the
    /// half-open range `object_range` computed).
    fn select_object_visual(obj: TextObject, ta: &mut TextArea<'static>) {
        let Some((row, start, end)) = Self::object_range_at_cursor(ta, obj) else {
            return;
        };
        if start >= end {
            // Empty object (vi( on "()"): collapsing to one char would make
            // the operator's inclusive +1 grab the closing delimiter. No-op.
            return;
        }
        ta.cancel_selection();
        // Leave the selection end ON the object's last char (visual
        // selections are inclusive; the operator's +1 restores [start, end)).
        Self::select_range(ta, (row, start), (row, end - 1), false);
    }

    // ── Insert + Replace mode handlers ───────────────────────────────────────

    fn handle_insert(&mut self, key: &KeyEvent, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        if key.code == KeyCode::Esc {
            return self.exit_to_normal(ta);
        }
        VimKeyOutcome::PassThrough
    }

    /// Replace (overwrite) mode — vim `R`. Keys are handled by the engine,
    /// never passed to the host textarea path: R is raw overwrite, with no
    /// auto-surround / smart-Enter underneath.
    fn handle_replace(&mut self, key: &KeyEvent, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        // A live selection (mouse drag) would make the textarea's delete/
        // insert calls wipe it wholesale on the next keypress — drop it.
        if ta.selection_range().is_some() {
            ta.cancel_selection();
        }
        let plain = key.modifiers == KeyModifiers::NONE || key.modifiers == KeyModifiers::SHIFT;
        match key.code {
            KeyCode::Esc => self.exit_to_normal(ta),
            KeyCode::Enter => {
                ta.insert_newline();
                // The newline starts a fresh replace extent.
                self.replace_stack.clear();
                VimKeyOutcome::TextMutated
            }
            KeyCode::Backspace => {
                // vim's replace stack: Backspace restores what the position
                // held before it was overwritten; an appended char (None) is
                // simply removed. Past the extent it's a plain step back.
                if super::cursor_tuple(ta).1 > 0 {
                    ta.move_cursor(CursorMove::Back);
                    match self.replace_stack.pop() {
                        Some(Some(orig)) => {
                            ta.delete_next_char();
                            ta.insert_char(orig);
                            ta.move_cursor(CursorMove::Back);
                            return VimKeyOutcome::TextMutated;
                        }
                        Some(None) => {
                            ta.delete_next_char();
                            return VimKeyOutcome::TextMutated;
                        }
                        None => {}
                    }
                }
                VimKeyOutcome::CursorOnly
            }
            KeyCode::Left | KeyCode::Right | KeyCode::Up | KeyCode::Down => {
                // vim allows movement in Replace mode and resets the replace
                // extent — restart the dot capture and the restore stack.
                ta.move_cursor(match key.code {
                    KeyCode::Left => CursorMove::Back,
                    KeyCode::Right => CursorMove::Forward,
                    KeyCode::Up => CursorMove::Up,
                    _ => CursorMove::Down,
                });
                let here = super::cursor_tuple(ta);
                if let Some(cap) = self.insert_capture.as_mut() {
                    cap.start = here;
                }
                self.replace_stack.clear();
                VimKeyOutcome::CursorOnly
            }
            KeyCode::Char(c) if plain => {
                // Record what this position held (None = appended past EOL)
                // so Backspace can restore it.
                let (row, col) = super::cursor_tuple(ta);
                let orig = ta.lines().get(row).and_then(|l| l.chars().nth(col));
                self.replace_stack.push(orig);
                Self::overwrite_char(ta, c);
                VimKeyOutcome::TextMutated
            }
            _ => VimKeyOutcome::NoOp,
        }
    }

    /// Overwrite the char under the cursor (plain insert at EOL — vim R
    /// appends once the line runs out), cursor left after the written char.
    fn overwrite_char(ta: &mut TextArea<'static>, ch: char) {
        if ch == '\n' {
            ta.insert_newline();
            return;
        }
        let (row, col) = super::cursor_tuple(ta);
        let len = ta.lines().get(row).map(|l| l.chars().count()).unwrap_or(0);
        if col < len {
            ta.delete_next_char();
        }
        ta.insert_char(ch);
    }

    /// Esc out of Insert/Replace mode: finalize the dot capture and step the
    /// cursor back (vim).
    fn exit_to_normal(&mut self, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        self.mode = EditorMode::Normal;
        self.replace_stack.clear();
        // A stray selection (mouse drag mid-Insert/Replace) must not survive
        // into Normal mode, where motions would silently extend it.
        ta.cancel_selection();
        // Compute the typed text once at Esc, slicing from the start cursor
        // recorded when Insert/Replace began to the current cursor.
        if let Some(cap) = self.insert_capture.take() {
            let end = super::cursor_tuple(ta);
            let inserted = Self::text_between(ta.lines(), cap.start, end);
            if !inserted.is_empty() || Self::records_when_empty(&cap.command) {
                self.last_change = Some(Change {
                    command: cap.command,
                    inserted: Some(inserted),
                });
            }
        }
        if super::cursor_tuple(ta).1 > 0 {
            ta.move_cursor(CursorMove::Back);
        }
        VimKeyOutcome::CursorOnly
    }

    // ── Normal mode: keys → parse → Command → execute/apply (adr/0011) ───────

    fn handle_normal(&mut self, key: &KeyEvent, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        match self.parse_normal(key) {
            Parsed::Pending | Parsed::Nothing => VimKeyOutcome::NoOp,
            Parsed::Cancel => {
                // Esc also cancels any stray textarea selection left live in
                // Normal mode (e.g. the auto-surround PassThrough path).
                ta.cancel_selection();
                VimKeyOutcome::CursorOnly
            }
            Parsed::Host(action) => {
                self.clear_pending();
                VimKeyOutcome::Host(action)
            }
            Parsed::Cmd(cmd) => self.execute(cmd, ta),
        }
    }

    /// Parse one Normal-mode key into a `Parsed` value. Pure pending-state
    /// accumulation — never touches the buffer (adr/0011).
    fn parse_normal(&mut self, key: &KeyEvent) -> Parsed {
        // One-key continuations (g-prefix, find target, replace char, object
        // key) consume the next key before anything else.
        if let Some(aw) = self.awaiting.take() {
            return self.parse_awaiting(aw, key);
        }

        // Esc cancels any pending sequence (operator, counts).
        if key.code == KeyCode::Esc {
            self.clear_pending();
            return Parsed::Cancel;
        }

        // Ctrl-r → redo (before the plain filter so it isn't stripped).
        if key.code == KeyCode::Char('r') && key.modifiers.contains(KeyModifiers::CONTROL) {
            return Parsed::Cmd(Command::Redo(self.take_total_count()));
        }

        let plain = key.modifiers == KeyModifiers::NONE || key.modifiers == KeyModifiers::SHIFT;
        match key.code {
            KeyCode::Char(c) if plain => self.parse_normal_char(c),
            KeyCode::Left => Parsed::Cmd(Command::Move(Motion::Left, 1)),
            KeyCode::Right => Parsed::Cmd(Command::Move(Motion::Right, 1)),
            KeyCode::Up => Parsed::Cmd(Command::Move(Motion::Up, 1)),
            KeyCode::Down => Parsed::Cmd(Command::Move(Motion::Down, 1)),
            _ => Parsed::Nothing,
        }
    }

    /// Consume the single key a continuation was waiting for. Non-char keys
    /// cancel the whole pending sequence (vim); Esc additionally clears any
    /// stray selection via the `Cancel` path.
    fn parse_awaiting(&mut self, aw: Awaiting, key: &KeyEvent) -> Parsed {
        let KeyCode::Char(c) = key.code else {
            self.clear_pending();
            return if key.code == KeyCode::Esc {
                Parsed::Cancel
            } else {
                Parsed::Nothing
            };
        };
        match aw {
            Awaiting::ReplaceChar => Parsed::Cmd(Command::ReplaceChar(c)),
            Awaiting::Find(pf) => {
                self.last_find = Some((c, pf.till, pf.forward));
                let motion = Motion::FindChar {
                    ch: c,
                    till: pf.till,
                    forward: pf.forward,
                };
                match pf.operator {
                    Some(op) => {
                        Parsed::Cmd(Command::OperateMotion(op, motion, self.take_total_count()))
                    }
                    None => Parsed::Cmd(Command::Move(motion, self.take_count())),
                }
            }
            Awaiting::G => self.parse_g_key(c),
            Awaiting::ObjectScope { around } => {
                if let Some(obj) = Self::object_for_char(c, around)
                    && let Some(op) = self.pending_operator.take()
                {
                    self.clear_pending();
                    return Parsed::Cmd(Command::OperateObject(op, obj));
                }
                self.clear_pending();
                Parsed::Nothing
            }
        }
    }

    /// The key after a pending `g`, dispatched through the shared g-command
    /// grammar (`g_key_for`).
    fn parse_g_key(&mut self, c: char) -> Parsed {
        match Self::g_key_for(c) {
            Some(GKey::GotoLine) => {
                // A count is a line number (5gg → line 5), wherever it was
                // typed relative to a pending operator (d5gg / 5dgg).
                let target = self
                    .pending_count
                    .take()
                    .or_else(|| self.pending_op_count.take());
                let m = match target {
                    Some(n) => Motion::GotoLine(n),
                    None => Motion::FileStart,
                };
                match self.pending_operator.take() {
                    Some(op) => Parsed::Cmd(Command::OperateMotion(op, m, 1)),
                    None => Parsed::Cmd(Command::Move(m, 1)),
                }
            }
            Some(GKey::Motion(m)) => match self.pending_operator.take() {
                Some(op) => Parsed::Cmd(Command::OperateMotion(op, m, self.take_total_count())),
                None => Parsed::Cmd(Command::Move(m, self.take_count())),
            },
            Some(GKey::CaseOp(op)) => {
                // gugu / gUgU / g~g~: the doubled g-form runs linewise.
                if self.pending_operator == Some(op) {
                    self.pending_operator = None;
                    return Parsed::Cmd(Command::OperateLine(op, self.take_total_count()));
                }
                self.pending_operator = Some(op);
                self.pending_op_count = self.pending_count.take();
                Parsed::Pending
            }
            Some(GKey::Join) => Parsed::Cmd(Command::JoinLines {
                count: self.take_count().max(2) - 1,
                spaced: false,
            }),
            None => {
                // Unmapped g-sequence aborts the whole pending state (vim).
                self.clear_pending();
                Parsed::Nothing
            }
        }
    }

    // ── parse_normal_char: pure Normal-mode key parser ───────────────────────

    /// Parse one plain Normal-mode char. Pure pending-state accumulation —
    /// commands come out as values; nothing here touches the buffer.
    fn parse_normal_char(&mut self, c: char) -> Parsed {
        // Count digits accumulate first.
        if self.accumulate_count(c) {
            return Parsed::Pending;
        }

        // g prefix — the next key resolves through the g-command grammar.
        if c == 'g' {
            self.awaiting = Some(Awaiting::G);
            return Parsed::Pending;
        }

        // guu / gUU / g~~: the doubled-key form runs the case op linewise.
        if let Some(op) = self.pending_operator {
            let doubles = matches!(
                (op, c),
                (Operator::Lowercase, 'u')
                    | (Operator::Uppercase, 'U')
                    | (Operator::ToggleCase, '~')
            );
            if doubles {
                self.pending_operator = None;
                return Parsed::Cmd(Command::OperateLine(op, self.take_total_count()));
            }
        }

        // Operator entry (d/c/y set pending; doubled → linewise).
        let op_for_char = match c {
            'd' => Some(Operator::Delete),
            'c' => Some(Operator::Change),
            'y' => Some(Operator::Yank),
            _ => None,
        };
        if let Some(op) = op_for_char {
            if self.pending_operator == Some(op) {
                return Parsed::Cmd(Command::OperateLine(op, self.take_total_count()));
            }
            if self.pending_operator.is_some() {
                // A different operator while one is pending aborts (vim).
                self.clear_pending();
                return Parsed::Nothing;
            }
            self.pending_operator = Some(op);
            // A count typed so far scopes to the operator; the motion gets
            // its own accumulator (vim multiplies the two).
            self.pending_op_count = self.pending_count.take();
            return Parsed::Pending;
        }
        // D / C / Y → operator to line end.
        if let Some(op) = match c {
            'D' => Some(Operator::Delete),
            'C' => Some(Operator::Change),
            'Y' => Some(Operator::Yank),
            _ => None,
        } {
            if self.pending_operator.is_some() {
                self.clear_pending();
                return Parsed::Nothing; // dD etc. abort (vim)
            }
            return Parsed::Cmd(Command::OperateToLineEnd(op));
        }

        // >>/<< indent/outdent: first key sets the pending operator; the
        // doubled key completes linewise. A motion after the first key (e.g.
        // `>j`) instead forms a range via the motion dispatch below.
        if c == '>' || c == '<' {
            let outdent = c == '<';
            if (outdent && self.pending_operator == Some(Operator::Outdent))
                || (!outdent && self.pending_operator == Some(Operator::Indent))
            {
                self.pending_operator = None;
                return Parsed::Cmd(Command::IndentLines {
                    outdent,
                    count: self.take_total_count(),
                });
            }
            if self.pending_operator.is_some() {
                self.clear_pending();
                return Parsed::Nothing; // d> etc. abort (vim)
            }
            self.pending_operator = Some(if outdent {
                Operator::Outdent
            } else {
                Operator::Indent
            });
            self.pending_op_count = self.pending_count.take();
            return Parsed::Pending;
        }

        // Paste.
        if c == 'p' || c == 'P' {
            if self.pending_operator.is_some() {
                self.clear_pending();
                return Parsed::Nothing; // dp etc. abort (vim)
            }
            return Parsed::Cmd(Command::Paste {
                after: c == 'p',
                count: self.take_count(),
            });
        }

        // f/F/t/T — await the find target (captures the operator so `df,` works).
        if let Some((till, forward)) = Self::find_spec_for(c) {
            self.awaiting = Some(Awaiting::Find(PendingFind {
                operator: self.pending_operator.take(),
                till,
                forward,
            }));
            return Parsed::Pending;
        }

        // ; and , — repeat last find (same / opposite direction); with a
        // pending operator (`d;`) forms a range like any motion.
        if c == ';' || c == ',' {
            if let Some(motion) = self.repeat_find_motion(c) {
                return match self.pending_operator.take() {
                    Some(op) => {
                        Parsed::Cmd(Command::OperateMotion(op, motion, self.take_total_count()))
                    }
                    None => Parsed::Cmd(Command::Move(motion, self.take_count())),
                };
            }
            self.clear_pending();
            return Parsed::Nothing;
        }

        // Text objects — `i`/`a` with an operator pending awaits the object
        // key (so `di`/`ci`/`yi` never enter Insert; the object char is
        // consumed by parse_awaiting, not the motion dispatch).
        if self.pending_operator.is_some() && (c == 'i' || c == 'a') {
            self.awaiting = Some(Awaiting::ObjectScope { around: c == 'a' });
            return Parsed::Pending;
        }

        // Motion dispatch (count-aware; with a pending operator, forms a range).
        if let Some(m) = Self::motion_for_char(c) {
            // 5G goes to line 5 — the count is a line number, not a repeat.
            if c == 'G' {
                let target = self
                    .pending_count
                    .take()
                    .or_else(|| self.pending_op_count.take());
                let m = match target {
                    Some(n) => Motion::GotoLine(n),
                    None => m,
                };
                return match self.pending_operator.take() {
                    Some(op) => Parsed::Cmd(Command::OperateMotion(op, m, 1)),
                    None => Parsed::Cmd(Command::Move(m, 1)),
                };
            }
            return match self.pending_operator.take() {
                Some(op) => Parsed::Cmd(Command::OperateMotion(op, m, self.take_total_count())),
                None => Parsed::Cmd(Command::Move(m, self.take_count())),
            };
        }

        // A pending operator followed by a key that forms no motion, object,
        // find, or doubled form aborts the whole sequence (vim beeps and
        // cancels) — `gUu` must not run Undo, `dx` must not delete a char.
        if self.pending_operator.is_some() {
            self.clear_pending();
            return Parsed::Nothing;
        }

        // Single-key edits, dot, visual entry, host actions, insert entry.
        // NOTE: i/a only reach here when NO operator is pending — operator +
        // i/a is the text-object path above.
        let cmd = match c {
            'x' => Command::DeleteChar {
                forward: true,
                count: self.take_count(),
            },
            'X' => Command::DeleteChar {
                forward: false,
                count: self.take_count(),
            },
            'r' => {
                self.awaiting = Some(Awaiting::ReplaceChar);
                return Parsed::Pending;
            }
            's' => Command::SubstituteChar(self.take_count()),
            'S' => Command::SubstituteLine,
            'R' => Command::EnterReplace,
            'J' => Command::JoinLines {
                count: self.take_count().max(2) - 1,
                spaced: true,
            },
            '~' => Command::ToggleCase(self.take_count()),
            'u' => Command::Undo(self.take_count()),
            '.' => Command::Repeat,
            'v' => Command::EnterVisual { line: false },
            'V' => Command::EnterVisual { line: true },
            'i' => Command::EnterInsert(InsertEntry::Here),
            'a' => Command::EnterInsert(InsertEntry::After),
            'I' => Command::EnterInsert(InsertEntry::LineStart),
            'A' => Command::EnterInsert(InsertEntry::LineEnd),
            'o' => Command::EnterInsert(InsertEntry::OpenBelow),
            'O' => Command::EnterInsert(InsertEntry::OpenAbove),
            // Host actions — `:` `/` `?` `n` `N` (adr/0012). `?` backward-first
            // is deferred; `/` and `?` both open the find bar for v1.
            ':' => return Parsed::Host(VimHostAction::OpenPalette),
            '/' => return Parsed::Host(VimHostAction::OpenSearch { forward: true }),
            '?' => return Parsed::Host(VimHostAction::OpenSearch { forward: false }),
            'n' => return Parsed::Host(VimHostAction::SearchNext),
            'N' => return Parsed::Host(VimHostAction::SearchPrev),
            _ => {
                self.clear_pending();
                return Parsed::Nothing;
            }
        };
        Parsed::Cmd(cmd)
    }

    /// Run a freshly-parsed command through the one mutation door, recording
    /// it for `.` when it is a repeatable change. Change-family commands
    /// defer recording to Esc (the insert capture owns it).
    fn execute(&mut self, cmd: Command, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        let outcome = self.apply(&cmd, None, ta);
        if outcome != VimKeyOutcome::NoOp && Self::repeatable(&cmd) && self.insert_capture.is_none()
        {
            self.record(cmd);
        }
        self.clear_pending();
        outcome
    }

    /// Whether `.` repeats this command. Motions, undo/redo, yanks, mode
    /// changes and `.` itself are not changes (vim semantics).
    fn repeatable(cmd: &Command) -> bool {
        match cmd {
            Command::Move(..)
            | Command::Undo(_)
            | Command::Redo(_)
            | Command::EnterVisual { .. }
            | Command::Repeat => false,
            Command::OperateMotion(op, ..)
            | Command::OperateLine(op, _)
            | Command::OperateObject(op, _)
            | Command::OperateToLineEnd(op) => *op != Operator::Yank,
            // Exhaustive on purpose — a new Command variant must decide its
            // dot-repeat policy here, not inherit a silent default.
            Command::IndentLines { .. }
            | Command::DeleteChar { .. }
            | Command::ReplaceChar(_)
            | Command::SubstituteChar(_)
            | Command::SubstituteLine
            | Command::JoinLines { .. }
            | Command::ToggleCase(_)
            | Command::Paste { .. }
            | Command::EnterInsert(_)
            | Command::EnterReplace => true,
        }
    }

    /// Whether Esc with NOTHING typed still records the command for `.`.
    /// Plain insert entries (i/a/I/A, R) don't — an aborted insert is not a
    /// change in vim. o/O do (the opened line IS the change), and the
    /// Change family does (the cut already happened before Insert began).
    /// Exhaustive on purpose, like `repeatable` — a new command must decide.
    fn records_when_empty(cmd: &Command) -> bool {
        match cmd {
            Command::EnterInsert(
                InsertEntry::Here
                | InsertEntry::After
                | InsertEntry::LineStart
                | InsertEntry::LineEnd,
            )
            | Command::EnterReplace => false,
            Command::EnterInsert(InsertEntry::OpenBelow | InsertEntry::OpenAbove)
            | Command::Move(..)
            | Command::OperateMotion(..)
            | Command::OperateLine(..)
            | Command::OperateObject(..)
            | Command::OperateToLineEnd(_)
            | Command::IndentLines { .. }
            | Command::DeleteChar { .. }
            | Command::ReplaceChar(_)
            | Command::SubstituteChar(_)
            | Command::SubstituteLine
            | Command::JoinLines { .. }
            | Command::ToggleCase(_)
            | Command::Paste { .. }
            | Command::Undo(_)
            | Command::Redo(_)
            | Command::EnterVisual { .. }
            | Command::Repeat => true,
        }
    }

    /// The only door that mutates the buffer for Normal-mode commands.
    /// `inserted` is the captured Insert-mode delta when replaying a
    /// Change-family command (dot-repeat); `None` on a first press, which
    /// enters Insert mode and starts capturing instead.
    fn apply(
        &mut self,
        cmd: &Command,
        inserted: Option<&str>,
        ta: &mut TextArea<'static>,
    ) -> VimKeyOutcome {
        match *cmd {
            Command::Move(m, n) => {
                self.apply_motion(m, n, ta);
                VimKeyOutcome::CursorOnly
            }
            Command::OperateMotion(op, m, n) => {
                if self.apply_operator_motion(op, m, n, inserted, ta) {
                    Self::outcome_for(op)
                } else {
                    VimKeyOutcome::NoOp
                }
            }
            Command::OperateLine(op, n) => {
                self.apply_operator_linewise(op, n, inserted, ta);
                Self::outcome_for(op)
            }
            Command::OperateObject(op, obj) => {
                if self.apply_operator_object(op, obj, inserted, ta) {
                    Self::outcome_for(op)
                } else {
                    VimKeyOutcome::NoOp
                }
            }
            Command::OperateToLineEnd(op) => {
                self.apply_operator_to_line_end(op, inserted, ta);
                Self::outcome_for(op)
            }
            Command::IndentLines { outdent, count } => {
                self.indent_lines(outdent, count, ta);
                VimKeyOutcome::TextMutated
            }
            Command::DeleteChar { forward, count } => {
                if self.delete_chars(forward, count, ta) {
                    VimKeyOutcome::TextMutated
                } else {
                    VimKeyOutcome::NoOp
                }
            }
            Command::ReplaceChar(c) => self.replace_char(c, ta),
            Command::SubstituteChar(n) => {
                // vim `s` enters Insert even on an empty line; the delete's
                // success only matters for the outcome's mutation signal.
                let deleted = self.delete_chars(true, n, ta);
                self.finish_insert_entry(cmd, inserted, ta);
                if deleted || inserted.is_some() {
                    VimKeyOutcome::TextMutated
                } else {
                    VimKeyOutcome::CursorOnly
                }
            }
            Command::SubstituteLine => {
                // Linewise register fill (vim: S puts the whole line in the
                // unnamed register, linewise), computed before the cut.
                let (row, _) = super::cursor_tuple(ta);
                if let Some(text) = ta.lines().get(row).map(|l| format!("{l}\n")) {
                    self.registers.fill(text, RegisterKind::Linewise);
                }
                ta.move_cursor(CursorMove::Head);
                ta.start_selection();
                ta.move_cursor(CursorMove::End);
                ta.cut();
                self.finish_insert_entry(cmd, inserted, ta);
                VimKeyOutcome::TextMutated
            }
            Command::JoinLines { count, spaced } => {
                for _ in 0..count.max(1) {
                    Self::join_line(ta, spaced);
                }
                VimKeyOutcome::TextMutated
            }
            Command::ToggleCase(n) => {
                for _ in 0..n {
                    Self::toggle_case_at_cursor(ta);
                }
                VimKeyOutcome::TextMutated
            }
            Command::Paste { after, count } => {
                if self.paste(after, count, ta) {
                    VimKeyOutcome::TextMutated
                } else {
                    VimKeyOutcome::NoOp
                }
            }
            Command::Undo(n) => {
                for _ in 0..n {
                    ta.undo();
                }
                VimKeyOutcome::TextMutated
            }
            Command::Redo(n) => {
                for _ in 0..n {
                    ta.redo();
                }
                VimKeyOutcome::TextMutated
            }
            Command::EnterInsert(entry) => self.apply_enter_insert(entry, cmd, inserted, ta),
            Command::EnterReplace => match inserted {
                Some(text) => {
                    for ch in text.chars() {
                        Self::overwrite_char(ta, ch);
                    }
                    self.mode = EditorMode::Normal;
                    if super::cursor_tuple(ta).1 > 0 {
                        ta.move_cursor(CursorMove::Back);
                    }
                    VimKeyOutcome::TextMutated
                }
                None => {
                    self.enter_insert_capture(cmd.clone(), ta);
                    self.mode = EditorMode::Replace; // the capture helper sets Insert
                    self.replace_stack.clear();
                    VimKeyOutcome::CursorOnly
                }
            },
            Command::EnterVisual { line } => {
                if line {
                    ta.move_cursor(CursorMove::Head);
                    ta.start_selection();
                    ta.move_cursor(CursorMove::End);
                    self.mode = EditorMode::VisualLine;
                } else {
                    ta.start_selection();
                    self.mode = EditorMode::Visual;
                }
                VimKeyOutcome::CursorOnly
            }
            Command::Repeat => match self.last_change.clone() {
                Some(change) => self.apply(&change.command, change.inserted.as_deref(), ta),
                None => VimKeyOutcome::NoOp,
            },
        }
    }

    /// Shared tail of every command that ends in Insert mode: on a first
    /// press, enter Insert and start capturing the typed delta; on replay,
    /// insert the captured text directly and stay in Normal.
    fn finish_insert_entry(
        &mut self,
        cmd: &Command,
        inserted: Option<&str>,
        ta: &mut TextArea<'static>,
    ) {
        match inserted {
            Some(text) => {
                ta.insert_str(text);
                self.mode = EditorMode::Normal;
            }
            None => self.enter_insert_capture(cmd.clone(), ta),
        }
    }

    fn apply_enter_insert(
        &mut self,
        entry: InsertEntry,
        cmd: &Command,
        inserted: Option<&str>,
        ta: &mut TextArea<'static>,
    ) -> VimKeyOutcome {
        let opened_line = match entry {
            InsertEntry::Here => false,
            InsertEntry::After => {
                ta.move_cursor(CursorMove::Forward);
                false
            }
            InsertEntry::LineStart => {
                // vim I: insert before the FIRST NON-BLANK char, not col 0.
                Self::first_non_blank(ta);
                false
            }
            InsertEntry::LineEnd => {
                ta.move_cursor(CursorMove::End);
                false
            }
            InsertEntry::OpenBelow => {
                ta.move_cursor(CursorMove::End);
                ta.insert_newline();
                true
            }
            InsertEntry::OpenAbove => {
                ta.move_cursor(CursorMove::Head);
                ta.insert_newline();
                ta.move_cursor(CursorMove::Up);
                true
            }
        };
        match inserted {
            Some(text) => {
                ta.insert_str(text);
                self.mode = EditorMode::Normal;
                if super::cursor_tuple(ta).1 > 0 {
                    ta.move_cursor(CursorMove::Back);
                }
                VimKeyOutcome::TextMutated
            }
            None => {
                self.enter_insert_capture(cmd.clone(), ta);
                if opened_line {
                    VimKeyOutcome::TextMutated
                } else {
                    VimKeyOutcome::CursorOnly
                }
            }
        }
    }

    /// Map a Normal/Visual motion key to its Motion. Shared by normal_char and handle_visual.
    fn motion_for_char(c: char) -> Option<Motion> {
        match c {
            'h' => Some(Motion::Left),
            'l' => Some(Motion::Right),
            'k' => Some(Motion::Up),
            'j' => Some(Motion::Down),
            'w' => Some(Motion::WordForward),
            'W' => Some(Motion::WordForwardBig),
            'b' => Some(Motion::WordBack),
            'B' => Some(Motion::WordBackBig),
            'e' => Some(Motion::WordEnd),
            'E' => Some(Motion::WordEndBig),
            '0' => Some(Motion::LineStart),
            '^' => Some(Motion::FirstNonBlank),
            '$' => Some(Motion::LineEnd),
            'G' => Some(Motion::FileEnd),
            '{' => Some(Motion::ParagraphBack),
            '}' => Some(Motion::ParagraphForward),
            '%' => Some(Motion::MatchingPair),
            _ => None,
        }
    }

    /// The g-command grammar: what one key after a pending `g` means. Both
    /// the Normal parser and the Visual handler consume this single table
    /// (dispatching per mode), so a new g-command is added exactly once.
    fn g_key_for(c: char) -> Option<GKey> {
        match c {
            'g' => Some(GKey::GotoLine), // gg — file start, or line N with a count
            'e' => Some(GKey::Motion(Motion::WordEndBack { big: false })),
            'E' => Some(GKey::Motion(Motion::WordEndBack { big: true })),
            '_' => Some(GKey::Motion(Motion::LastNonBlank)),
            'u' => Some(GKey::CaseOp(Operator::Lowercase)),
            'U' => Some(GKey::CaseOp(Operator::Uppercase)),
            '~' => Some(GKey::CaseOp(Operator::ToggleCase)),
            'J' => Some(GKey::Join),
            _ => None,
        }
    }

    /// Map a find key to its `(till, forward)` spec. Shared by the Normal
    /// parser and the Visual handler.
    fn find_spec_for(c: char) -> Option<(bool, bool)> {
        match c {
            'f' => Some((false, true)),
            'F' => Some((false, false)),
            't' => Some((true, true)),
            'T' => Some((true, false)),
            _ => None,
        }
    }

    /// The motion `;` / `,` repeats: the last find, same or reversed
    /// direction. Shared by the Normal parser and the Visual handler.
    fn repeat_find_motion(&self, c: char) -> Option<Motion> {
        let (ch, till, fwd) = self.last_find?;
        let forward = if c == ';' { fwd } else { !fwd };
        Some(Motion::FindChar { ch, till, forward })
    }

    // ── count accumulation helpers ───────────────────────────────────────────

    fn take_count(&mut self) -> usize {
        self.pending_count.take().unwrap_or(1)
    }

    /// Operator-scoped count × motion-scoped count (vim: `2d3w` = 6 words).
    fn take_total_count(&mut self) -> usize {
        let op_n = self.pending_op_count.take().unwrap_or(1);
        op_n * self.pending_count.take().unwrap_or(1)
    }

    fn clear_pending(&mut self) {
        self.pending_count = None;
        self.pending_op_count = None;
        self.pending_operator = None;
        self.awaiting = None;
    }

    /// Returns true if `c` was consumed as a count digit.
    fn accumulate_count(&mut self, c: char) -> bool {
        if c.is_ascii_digit() {
            // bare '0' with no pending count is the LineStart motion, not a digit
            if c == '0' && self.pending_count.is_none() {
                return false;
            }
            let d = c as usize - '0' as usize;
            self.pending_count = Some(self.pending_count.unwrap_or(0) * 10 + d);
            return true;
        }
        false
    }

    // ── Motion resolution ────────────────────────────────────────────────────

    /// Where `motion` (× count) would land, as a position value — no net
    /// cursor mutation (the cursor is restored before returning).
    fn resolve_motion(
        &self,
        motion: Motion,
        count: usize,
        ta: &mut TextArea<'static>,
    ) -> (usize, usize) {
        let saved = super::cursor_tuple(ta);
        self.apply_motion(motion, count, ta);
        let target = super::cursor_tuple(ta);
        ta.move_cursor(CursorMove::Jump(saved.0 as u16, saved.1 as u16));
        target
    }

    /// Vim's motion classification: how a motion forms an operator range.
    /// (`:h exclusive` — every vim motion is exclusive, inclusive, or
    /// linewise when consumed by an operator.)
    fn kind_of(motion: Motion) -> SpanKind {
        match motion {
            Motion::Up
            | Motion::Down
            | Motion::FileStart
            | Motion::FileEnd
            | Motion::GotoLine(_) => SpanKind::Linewise,
            Motion::WordEnd
            | Motion::WordEndBig
            | Motion::WordEndBack { .. }
            | Motion::MatchingPair => SpanKind::Inclusive,
            // d$ / dg_ delete through the char they land on (vim: inclusive).
            Motion::LineEnd | Motion::LastNonBlank => SpanKind::Inclusive,
            // f/t are inclusive; F/T (backward) are exclusive.
            Motion::FindChar { forward: true, .. } => SpanKind::Inclusive,
            _ => SpanKind::Exclusive,
        }
    }

    /// Select `[start, end]` (inclusive) or `[start, end)` on the textarea.
    /// The single home of the vim-inclusive → ratatui-half-open `+1`
    /// conversion, clamped to the end line's length.
    fn select_range(
        ta: &mut TextArea<'static>,
        start: (usize, usize),
        end: (usize, usize),
        inclusive: bool,
    ) {
        let (er, ec) = end;
        let end_col = if inclusive {
            let len = ta.lines().get(er).map(|l| l.chars().count()).unwrap_or(ec);
            (ec + 1).min(len)
        } else {
            ec
        };
        ta.move_cursor(CursorMove::Jump(start.0 as u16, start.1 as u16));
        ta.start_selection();
        ta.move_cursor(CursorMove::Jump(er as u16, end_col as u16));
    }

    fn apply_motion(&self, motion: Motion, count: usize, ta: &mut TextArea<'static>) {
        // Count-finds are atomic in vim: `2fx` with one 'x' fails the WHOLE
        // motion (cursor stays put) — never "as far as possible". Handled
        // outside the per-count loop, which can't express that.
        if let Motion::FindChar { ch, till, forward } = motion {
            Self::find_char_count(ta, ch, till, forward, count);
            return;
        }
        for _ in 0..count.max(1) {
            match motion {
                Motion::Left => ta.move_cursor(CursorMove::Back),
                Motion::Right => ta.move_cursor(CursorMove::Forward),
                Motion::Up => ta.move_cursor(CursorMove::Up),
                Motion::Down => ta.move_cursor(CursorMove::Down),
                Motion::WordForward => ta.move_cursor(CursorMove::WordForward),
                Motion::WordBack => ta.move_cursor(CursorMove::WordBack),
                Motion::WordEnd => ta.move_cursor(CursorMove::WordEnd),
                Motion::WordForwardBig => {
                    let (r, c) = Self::word_forward_big(ta.lines(), super::cursor_tuple(ta));
                    ta.move_cursor(CursorMove::Jump(r as u16, c as u16));
                }
                Motion::WordBackBig => {
                    let (r, c) = Self::word_back_big(ta.lines(), super::cursor_tuple(ta));
                    ta.move_cursor(CursorMove::Jump(r as u16, c as u16));
                }
                Motion::WordEndBig => {
                    if let Some((r, c)) = Self::word_end_big(ta.lines(), super::cursor_tuple(ta)) {
                        ta.move_cursor(CursorMove::Jump(r as u16, c as u16));
                    }
                }
                Motion::WordEndBack { big } => {
                    if let Some((r, c)) =
                        Self::word_end_back(ta.lines(), super::cursor_tuple(ta), big)
                    {
                        ta.move_cursor(CursorMove::Jump(r as u16, c as u16));
                    }
                }
                Motion::LineStart => ta.move_cursor(CursorMove::Head),
                Motion::FirstNonBlank => Self::first_non_blank(ta),
                Motion::LastNonBlank => Self::last_non_blank(ta),
                Motion::LineEnd => ta.move_cursor(CursorMove::End),
                Motion::FileStart => ta.move_cursor(CursorMove::Top),
                Motion::FileEnd => ta.move_cursor(CursorMove::Bottom),
                Motion::GotoLine(n) => {
                    let last = ta.lines().len().saturating_sub(1);
                    let row = n.saturating_sub(1).min(last);
                    ta.move_cursor(CursorMove::Jump(row as u16, 0));
                }
                Motion::ParagraphForward => ta.move_cursor(CursorMove::ParagraphForward),
                Motion::ParagraphBack => ta.move_cursor(CursorMove::ParagraphBack),
                Motion::MatchingPair => Self::match_pair(ta),
                Motion::FindChar { .. } => unreachable!("handled atomically above"),
            }
        }
    }

    fn first_non_blank(ta: &mut TextArea<'static>) {
        let (row, _) = super::cursor_tuple(ta);
        if let Some(line) = ta.lines().get(row) {
            let n = line.chars().take_while(|c| c.is_whitespace()).count();
            ta.move_cursor(CursorMove::Jump(row as u16, n as u16));
        }
    }

    /// `g_` — last non-blank char of the line (no-op on a blank line, vim).
    fn last_non_blank(ta: &mut TextArea<'static>) {
        let (row, _) = super::cursor_tuple(ta);
        let idx = ta.lines().get(row).and_then(|line| {
            line.chars()
                .enumerate()
                .filter(|(_, c)| !c.is_whitespace())
                .map(|(i, _)| i)
                .last()
        });
        if let Some(idx) = idx {
            ta.move_cursor(CursorMove::Jump(row as u16, idx as u16));
        }
    }

    /// Char class for small-word motions: blank / word (alnum + `_`) / punct.
    fn char_class(c: char) -> u8 {
        if c.is_whitespace() {
            0
        } else if c.is_alphanumeric() || c == '_' {
            1
        } else {
            2
        }
    }

    /// `W` — the start of the next WORD (any non-blank run) after `pos`.
    /// Crosses lines; an empty line is itself a WORD stop (vim). Pure over
    /// the line slice — the caller jumps the cursor.
    fn word_forward_big(lines: &[String], pos: (usize, usize)) -> (usize, usize) {
        let (mut row, mut col) = pos;
        let last = lines.len().saturating_sub(1);
        let mut chars: Vec<char> = lines[row].chars().collect();
        // Skip the rest of the current WORD.
        while col < chars.len() && !chars[col].is_whitespace() {
            col += 1;
        }
        // Skip blanks to the next WORD start.
        loop {
            if col >= chars.len() {
                if row == last {
                    break; // EOF: rest at line end
                }
                row += 1;
                chars = lines[row].chars().collect();
                col = 0;
                if chars.is_empty() {
                    break;
                }
                continue;
            }
            if chars[col].is_whitespace() {
                col += 1;
            } else {
                break;
            }
        }
        (row, col)
    }

    /// `B` — the start of the current/previous WORD before `pos`. Pure.
    fn word_back_big(lines: &[String], pos: (usize, usize)) -> (usize, usize) {
        let (mut row, mut col) = pos;
        let mut chars: Vec<char> = lines[row].chars().collect();
        // Walk backward to the previous non-blank char, crossing lines; an
        // empty line is itself a stop (vim).
        loop {
            if col == 0 {
                if row == 0 {
                    return pos; // nothing before — motion fails in place
                }
                row -= 1;
                chars = lines[row].chars().collect();
                if chars.is_empty() {
                    return (row, 0);
                }
                col = chars.len() - 1;
            } else {
                col -= 1;
            }
            if !chars[col].is_whitespace() {
                break;
            }
        }
        // Walk to the start of this WORD.
        while col > 0 && !chars[col - 1].is_whitespace() {
            col -= 1;
        }
        (row, col)
    }

    /// `E` — the end of the next WORD after `pos`; `None` when no WORD
    /// follows (vim fails the motion). Pure.
    fn word_end_big(lines: &[String], pos: (usize, usize)) -> Option<(usize, usize)> {
        let (mut row, mut col) = pos;
        let last = lines.len().saturating_sub(1);
        let mut chars: Vec<char> = lines[row].chars().collect();
        // Step one position forward, then find the next non-blank.
        col += 1;
        loop {
            if col >= chars.len() {
                if row == last {
                    return None; // nothing ahead — cursor stays
                }
                row += 1;
                chars = lines[row].chars().collect();
                col = 0;
                continue;
            }
            if chars[col].is_whitespace() {
                col += 1;
            } else {
                break;
            }
        }
        // Advance to the last char of this WORD.
        while col + 1 < chars.len() && !chars[col + 1].is_whitespace() {
            col += 1;
        }
        Some((row, col))
    }

    /// `ge` / `gE` — the nearest previous word end before `pos`: a non-blank
    /// char whose successor is blank/EOL (or, for small words, a different
    /// char class). `None` when none exists. Pure.
    fn word_end_back(lines: &[String], pos: (usize, usize), big: bool) -> Option<(usize, usize)> {
        let (mut row, mut col) = pos;
        let mut chars: Vec<char> = lines[row].chars().collect();
        // The textarea cursor can sit one past the last char ($ / line end);
        // vim's cursor is ON the last char — clamp so "before the cursor"
        // doesn't match the char under the cursor itself.
        if !chars.is_empty() && col >= chars.len() {
            col = chars.len() - 1;
        }
        loop {
            // Step one position back, crossing lines (EOL is a position).
            if col == 0 {
                if row == 0 {
                    return None;
                }
                row -= 1;
                chars = lines[row].chars().collect();
                col = chars.len();
                continue;
            }
            col -= 1;
            let ch = chars[col];
            if ch.is_whitespace() {
                continue;
            }
            let is_end = match chars.get(col + 1) {
                None => true, // EOL after it
                Some(&n) => {
                    n.is_whitespace() || (!big && Self::char_class(n) != Self::char_class(ch))
                }
            };
            if is_end {
                return Some((row, col));
            }
        }
    }

    /// Jump to the bracket that matches the one under the cursor, scanning
    /// across lines. Opening bracket → forward with depth counting to the
    /// matching close; closing bracket → backward to the matching open.
    /// No-op when the cursor is not on a bracket or no match exists.
    fn match_pair(ta: &mut TextArea<'static>) {
        let (row, col) = super::cursor_tuple(ta);
        let lines = ta.lines();
        let here = match lines.get(row).and_then(|l| l.chars().nth(col)) {
            Some(c) => c,
            None => return,
        };
        let pairs = [('(', ')'), ('[', ']'), ('{', '}'), ('<', '>')];
        let target = if let Some(&(_, close)) = pairs.iter().find(|&&(o, _)| o == here) {
            // open → scan forward through the buffer
            let mut depth = 0i32;
            let mut found = None;
            'fwd: for (r, line) in lines.iter().enumerate().skip(row) {
                let start = if r == row { col } else { 0 };
                for (i, ch) in line.chars().enumerate().skip(start) {
                    if ch == here {
                        depth += 1;
                    } else if ch == close {
                        depth -= 1;
                        if depth == 0 {
                            found = Some((r, i));
                            break 'fwd;
                        }
                    }
                }
            }
            found
        } else if let Some(&(open, _)) = pairs.iter().find(|&&(_, c)| c == here) {
            // close → scan backward through the buffer
            let mut depth = 0i32;
            let mut found = None;
            'back: for r in (0..=row).rev() {
                let chars: Vec<char> = lines[r].chars().collect();
                let last = if r == row {
                    col
                } else {
                    chars.len().saturating_sub(1)
                };
                if chars.is_empty() {
                    continue;
                }
                for i in (0..=last.min(chars.len() - 1)).rev() {
                    if chars[i] == here {
                        depth += 1;
                    } else if chars[i] == open {
                        depth -= 1;
                        if depth == 0 {
                            found = Some((r, i));
                            break 'back;
                        }
                    }
                }
            }
            found
        } else {
            None
        };
        if let Some((r, c)) = target {
            ta.move_cursor(CursorMove::Jump(r as u16, c as u16));
        }
    }

    /// Move to the `count`-th occurrence of `ch` on the current line —
    /// atomically: fewer than `count` occurrences fails the whole motion and
    /// the cursor does not move (vim). `forward`: search right from col+1;
    /// otherwise left from col-1. `till`: stop one column short (t/T).
    fn find_char_count(
        ta: &mut TextArea<'static>,
        ch: char,
        till: bool,
        forward: bool,
        count: usize,
    ) {
        let (row, col) = super::cursor_tuple(ta);
        let Some(line) = ta.lines().get(row).cloned() else {
            return;
        };
        let chars: Vec<char> = line.chars().collect();
        let n = count.max(1);
        let pos = if forward {
            ((col + 1)..chars.len())
                .filter(|&i| chars[i] == ch)
                .nth(n - 1)
        } else {
            (0..col).rev().filter(|&i| chars[i] == ch).nth(n - 1)
        };
        let Some(pos) = pos else { return };
        let target = if till {
            if forward {
                pos.saturating_sub(1)
            } else {
                pos + 1
            }
        } else {
            pos
        };
        ta.move_cursor(CursorMove::Jump(row as u16, target as u16));
    }

    // ── Operator framework ───────────────────────────────────────────────────

    fn outcome_for(op: Operator) -> VimKeyOutcome {
        match op {
            Operator::Yank => VimKeyOutcome::CursorOnly, // yank doesn't change text
            _ => VimKeyOutcome::TextMutated,
        }
    }

    /// Operate over the range from the cursor through `motion` (× count).
    /// The range's shape is the motion's `SpanKind`: linewise motions (j/k,
    /// gg/G) operate on whole lines, inclusive motions (e, f/t, %, $) take
    /// the char they land on, exclusive motions stop short of it.
    /// Returns `false` when the motion failed and the whole operation was a
    /// vim no-op (nothing deleted, no Insert entry, register untouched).
    fn apply_operator_motion(
        &mut self,
        op: Operator,
        m: Motion,
        count: usize,
        inserted: Option<&str>,
        ta: &mut TextArea<'static>,
    ) -> bool {
        // Vim `cw`/`cW` semantics: change + word-forward uses word-end (not
        // word-start of the next word), so the trailing space is preserved.
        // This is vim's well-known `cw = ce` behaviour. Other operators (dw, yw)
        // use the motion as-is (including the trailing space).
        let effective_motion = if op == Operator::Change {
            match m {
                Motion::WordForward => Motion::WordEnd,
                Motion::WordForwardBig => Motion::WordEndBig, // cW = cE
                other => other,
            }
        } else {
            m
        };
        let origin = super::cursor_tuple(ta);
        let target = self.resolve_motion(effective_motion, count, ta);
        match Self::kind_of(effective_motion) {
            SpanKind::Linewise => {
                // j/k must actually traverse `count` rows; at a buffer edge
                // the motion fails and vim no-ops the whole operation (dj on
                // the last line deletes nothing). gg/G always resolve —
                // operating on the current line is valid for them.
                if matches!(effective_motion, Motion::Up | Motion::Down)
                    && origin.0.abs_diff(target.0) < count
                {
                    return false;
                }
                let top = origin.0.min(target.0);
                let lines = origin.0.abs_diff(target.0) + 1;
                ta.move_cursor(CursorMove::Jump(top as u16, 0));
                self.apply_operator_linewise(op, lines, inserted, ta);
                true
            }
            kind => {
                if target == origin
                    && (kind == SpanKind::Exclusive
                        || matches!(
                            effective_motion,
                            // Inclusive motions that signal failure by not
                            // moving: failed find/pair-match, ge at buffer
                            // start, E at buffer end.
                            Motion::FindChar { .. }
                                | Motion::MatchingPair
                                | Motion::WordEndBack { .. }
                                | Motion::WordEndBig
                        ))
                {
                    // Failed motion or zero-width exclusive range: vim no-op
                    // — nothing deleted, no Insert, register kept.
                    return false;
                }
                let (start, end) = if target < origin {
                    (target, origin)
                } else {
                    (origin, target)
                };
                Self::select_range(ta, start, end, kind == SpanKind::Inclusive);
                // For Change, capture under the actual command (original
                // motion, not the cw=ce substitute) so `.` replays it right.
                if op == Operator::Change {
                    ta.cut();
                    self.fill_from_textarea(ta, RegisterKind::Charwise);
                    self.finish_insert_entry(&Command::OperateMotion(op, m, count), inserted, ta);
                } else {
                    self.apply_operator_on_selection(op, ta);
                }
                true
            }
        }
    }

    fn apply_operator_linewise(
        &mut self,
        op: Operator,
        count: usize,
        inserted: Option<&str>,
        ta: &mut TextArea<'static>,
    ) {
        let (r0, _) = super::cursor_tuple(ta);
        let last = ta.lines().len().saturating_sub(1);
        let r1 = (r0 + count.saturating_sub(1)).min(last);

        // Register content: the line bodies plus a trailing newline (linewise).
        let body: String = ta.lines()[r0..=r1].join("\n");
        let register_text = format!("{body}\n");

        match op {
            Operator::Yank => {
                self.registers.fill(register_text, RegisterKind::Linewise);
                // cursor stays at start of first yanked line
                ta.move_cursor(CursorMove::Jump(r0 as u16, 0));
            }
            Operator::Delete | Operator::Change => {
                // Select the lines. Include the trailing newline if there is a
                // line after r1; otherwise (last line) include the PRECEDING
                // newline so no empty remnant is left.
                if r1 < last {
                    ta.move_cursor(CursorMove::Jump(r0 as u16, 0));
                    ta.start_selection();
                    ta.move_cursor(CursorMove::Jump((r1 + 1) as u16, 0));
                } else if r0 > 0 {
                    let prev_end = ta.lines()[r0 - 1].chars().count();
                    ta.move_cursor(CursorMove::Jump((r0 - 1) as u16, prev_end as u16));
                    ta.start_selection();
                    let end = ta.lines()[r1].chars().count();
                    ta.move_cursor(CursorMove::Jump(r1 as u16, end as u16));
                } else {
                    // whole buffer: select everything, leaving one empty line
                    ta.move_cursor(CursorMove::Jump(0, 0));
                    ta.start_selection();
                    let end = ta.lines()[r1].chars().count();
                    ta.move_cursor(CursorMove::Jump(r1 as u16, end as u16));
                }
                ta.cut();
                // The cut selection may include a leading newline on the
                // last-line path; fill the register with the proper linewise
                // content computed above instead.
                self.registers.fill(register_text, RegisterKind::Linewise);
                if op == Operator::Change {
                    // cc: open a fresh empty line to type into, at the right spot
                    if r0 == 0 && r1 == last {
                        // whole-buffer case: cut() left [""], the cursor is already
                        // at (0,0) on an empty line — no extra newline needed.
                        ta.move_cursor(CursorMove::Jump(0, 0));
                    } else if r0 > 0 && r1 == last {
                        // we consumed the preceding newline; add a line back
                        ta.move_cursor(CursorMove::End);
                        ta.insert_newline();
                    } else {
                        ta.insert_newline();
                        ta.move_cursor(CursorMove::Up);
                    }
                    self.finish_insert_entry(&Command::OperateLine(op, count), inserted, ta);
                }
            }
            Operator::Indent | Operator::Outdent => {
                // Linewise indent/outdent triggered by e.g. ">>" reaching
                // apply_operator_linewise is handled via normal_char's direct
                // indent_lines path. This arm is a safety net; it should not
                // normally be reached (>> goes through the doubled-operator path).
                let outdent = op == Operator::Outdent;
                self.indent_lines(outdent, count, ta);
            }
            Operator::Lowercase | Operator::Uppercase | Operator::ToggleCase => {
                // guu / gUU / g~~ / guj…: transform whole lines in ONE
                // cut+insert so undo reverts the command in one step, not
                // per line. Case operators never touch the register (vim).
                let transformed = ta.lines()[r0..=r1]
                    .iter()
                    .map(|l| Self::transform_case(l, op))
                    .collect::<Vec<_>>()
                    .join("\n");
                let end_len = ta.lines()[r1].chars().count();
                ta.move_cursor(CursorMove::Jump(r0 as u16, 0));
                ta.start_selection();
                ta.move_cursor(CursorMove::Jump(r1 as u16, end_len as u16));
                ta.cut();
                ta.insert_str(&transformed);
                ta.move_cursor(CursorMove::Jump(r0 as u16, 0));
            }
        }
    }

    fn apply_operator_to_line_end(
        &mut self,
        op: Operator,
        inserted: Option<&str>,
        ta: &mut TextArea<'static>,
    ) {
        ta.start_selection();
        ta.move_cursor(CursorMove::End);
        if op == Operator::Change {
            ta.cut();
            self.fill_from_textarea(ta, RegisterKind::Charwise);
            self.finish_insert_entry(&Command::OperateToLineEnd(op), inserted, ta);
        } else {
            self.apply_operator_on_selection(op, ta);
        }
    }

    /// Indent (add 4 spaces) or outdent (remove up to 4 leading spaces) the
    /// cursor's line, then repeat for `count` lines total (moving down after
    /// each). Used by `>>`, `<<`, and the visual `>`/`<` operators.
    fn indent_lines(&self, outdent: bool, count: usize, ta: &mut TextArea<'static>) {
        let (start_row, start_col) = super::cursor_tuple(ta);
        let mut first_line_delta = 0usize; // indent change on the cursor's own line
        for i in 0..count.max(1) {
            ta.move_cursor(CursorMove::Head);
            if outdent {
                // Remove up to 4 leading spaces.
                let (row, _) = super::cursor_tuple(ta);
                let n = ta
                    .lines()
                    .get(row)
                    .map(|l| l.chars().take(4).take_while(|c| *c == ' ').count())
                    .unwrap_or(0);
                if i == 0 {
                    first_line_delta = n;
                }
                for _ in 0..n {
                    ta.delete_next_char();
                }
            } else {
                if i == 0 {
                    first_line_delta = 4;
                }
                ta.insert_str("    ");
            }
            ta.move_cursor(CursorMove::Down);
        }
        // Keep the cursor over the same character it sat on, shifted by the
        // indent change — matches neovim's >> behavior.
        let col = if outdent {
            start_col.saturating_sub(first_line_delta)
        } else {
            start_col + first_line_delta
        };
        ta.move_cursor(CursorMove::Jump(start_row as u16, col as u16));
    }

    /// Capture the text the textarea just cut/copied (its yank buffer) into
    /// the engine's unnamed register. The textarea yank buffer is only a
    /// transport here — the engine never reads it back at paste time.
    fn fill_from_textarea(&mut self, ta: &TextArea<'static>, kind: RegisterKind) {
        self.registers.fill(ta.yank_text(), kind);
    }

    /// Charwise operator over the live selection. Change never reaches here —
    /// every Change path captures its own command before cutting (so `.`
    /// replays the right thing); linewise flows use apply_operator_linewise.
    fn apply_operator_on_selection(&mut self, op: Operator, ta: &mut TextArea<'static>) {
        match op {
            Operator::Yank => {
                let start = ta.selection_range().map(|(s, _)| s);
                ta.copy();
                self.fill_from_textarea(ta, RegisterKind::Charwise);
                ta.cancel_selection();
                if let Some((r, c)) = start {
                    ta.move_cursor(CursorMove::Jump(r as u16, c as u16));
                }
            }
            Operator::Delete | Operator::Change => {
                ta.cut();
                self.fill_from_textarea(ta, RegisterKind::Charwise);
            }
            Operator::Indent | Operator::Outdent => {
                // Compute the selected row range, cancel the selection, then
                // indent/outdent those rows. This covers operator+motion (e.g.
                // `>j`) and visual `>`/`<` (which call this via handle_visual).
                let outdent = op == Operator::Outdent;
                let (rows, start_row) = if let Some(((sr, _), (er, _))) = ta.selection_range() {
                    (er.saturating_sub(sr) + 1, sr)
                } else {
                    let (r, _) = super::cursor_tuple(ta);
                    (1, r)
                };
                ta.cancel_selection();
                ta.move_cursor(CursorMove::Jump(start_row as u16, 0));
                self.indent_lines(outdent, rows, ta);
            }
            Operator::Lowercase | Operator::Uppercase | Operator::ToggleCase => {
                // Replace the selection with its case-transformed text and
                // leave the cursor at the start (vim). The cut only passes
                // through the textarea yank buffer — the engine register is
                // deliberately NOT filled (vim: case operators don't yank).
                let start = ta.selection_range().map(|(s, _)| s);
                ta.cut();
                let transformed = Self::transform_case(&ta.yank_text(), op);
                ta.insert_str(&transformed);
                if let Some((r, c)) = start {
                    ta.move_cursor(CursorMove::Jump(r as u16, c as u16));
                }
            }
        }
    }

    /// Flip one char's case. The single home of toggle-case semantics,
    /// shared by bare `~`, visual/operator `g~`, and `transform_case`.
    fn flip_case(ch: char) -> String {
        if ch.is_uppercase() {
            ch.to_lowercase().collect()
        } else {
            ch.to_uppercase().collect()
        }
    }

    fn transform_case(text: &str, op: Operator) -> String {
        match op {
            Operator::Lowercase => text.to_lowercase(),
            Operator::Uppercase => text.to_uppercase(),
            _ => text.chars().map(Self::flip_case).collect(),
        }
    }

    /// Slice the buffer text between two cursor positions (row, col), inclusive
    /// of `start` and exclusive of `end`. Works across lines: the result for a
    /// two-line insert is `"line1_suffix\nline2_prefix"`. Returns `""` when
    /// `end <= start`.
    fn text_between(lines: &[String], start: (usize, usize), end: (usize, usize)) -> String {
        if end <= start {
            return String::new();
        }
        let (sr, sc) = start;
        let (er, ec) = end;
        if sr == er {
            return lines
                .get(sr)
                .map(|l| l.chars().skip(sc).take(ec.saturating_sub(sc)).collect())
                .unwrap_or_default();
        }
        let mut out = String::new();
        if let Some(l) = lines.get(sr) {
            out.extend(l.chars().skip(sc));
        }
        out.push('\n');
        for r in (sr + 1)..er {
            if let Some(l) = lines.get(r) {
                out.push_str(l);
            }
            out.push('\n');
        }
        if let Some(l) = lines.get(er) {
            out.extend(l.chars().take(ec));
        }
        out
    }

    fn enter_insert_capture(&mut self, command: Command, ta: &TextArea<'static>) {
        self.mode = EditorMode::Insert;
        self.insert_capture = Some(InsertCapture {
            command,
            start: super::cursor_tuple(ta),
        });
    }

    // ── Dot-repeat recording ─────────────────────────────────────────────────

    /// Record a completed mutating command in `last_change` (no inserted text).
    /// Called at every mutating, non-insert completion point.
    fn record(&mut self, command: Command) {
        self.last_change = Some(Change {
            command,
            inserted: None,
        });
    }

    // ── Paste p/P ────────────────────────────────────────────────────────────

    /// Returns `false` when the register is empty (nothing pasted).
    fn paste(&mut self, after: bool, count: usize, ta: &mut TextArea<'static>) -> bool {
        // Borrow, don't clone — the body only mutates `ta`, never `self`,
        // so a large register isn't copied on every p/P.
        let Some(reg) = self.registers.read() else {
            return false;
        };
        let text = &reg.text;
        match reg.kind {
            RegisterKind::Linewise => {
                let body = text.strip_suffix('\n').unwrap_or(text);
                let n = count.max(1);
                if after {
                    ta.move_cursor(CursorMove::End);
                    for _ in 0..n {
                        ta.insert_newline();
                        ta.insert_str(body);
                    }
                } else {
                    ta.move_cursor(CursorMove::Head);
                    for _ in 0..n {
                        ta.insert_str(body);
                        ta.insert_newline();
                    }
                }
            }
            RegisterKind::Charwise => {
                if after {
                    let (row, col) = super::cursor_tuple(ta);
                    let len = ta
                        .lines()
                        .get(row)
                        .map(|l| l.chars().count())
                        .unwrap_or(col);
                    ta.move_cursor(CursorMove::Jump(row as u16, (col + 1).min(len) as u16));
                }
                for _ in 0..count.max(1) {
                    ta.insert_str(text);
                }
            }
        }
        true
    }

    // ── Text object helpers ──────────────────────────────────────────────────

    /// Map an object char (e.g. `w`, `(`, `"`) to a `TextObject`.
    fn object_for_char(c: char, around: bool) -> Option<TextObject> {
        match c {
            'w' => Some(TextObject::Word { around }),
            '(' | ')' | 'b' => Some(TextObject::Pair {
                open: '(',
                close: ')',
                around,
            }),
            '{' | '}' | 'B' => Some(TextObject::Pair {
                open: '{',
                close: '}',
                around,
            }),
            '[' | ']' => Some(TextObject::Pair {
                open: '[',
                close: ']',
                around,
            }),
            '<' | '>' => Some(TextObject::Pair {
                open: '<',
                close: '>',
                around,
            }),
            '"' => Some(TextObject::Quote { ch: '"', around }),
            '\'' => Some(TextObject::Quote { ch: '\'', around }),
            '`' => Some(TextObject::Quote { ch: '`', around }),
            _ => None,
        }
    }

    /// Apply `op` over the text object `obj` at the current cursor position.
    /// Resolve `obj` at the cursor to `(row, start, end)` — half-open cols on
    /// the cursor's row (text objects are single-line for now). Shared by the
    /// operator path (`diw`) and the visual path (`vi(`).
    fn object_range_at_cursor(
        ta: &TextArea<'static>,
        obj: TextObject,
    ) -> Option<(usize, usize, usize)> {
        let (row, col) = super::cursor_tuple(ta);
        let line = ta.lines().get(row)?;
        let chars: Vec<char> = line.chars().collect();
        let (start, end) = Self::object_range(&chars, col, obj)?;
        Some((row, start, end))
    }

    /// Returns `false` when no object exists at the cursor (vim no-op).
    fn apply_operator_object(
        &mut self,
        op: Operator,
        obj: TextObject,
        inserted: Option<&str>,
        ta: &mut TextArea<'static>,
    ) -> bool {
        let Some((row, start, end)) = Self::object_range_at_cursor(ta, obj) else {
            return false;
        };
        Self::select_range(ta, (row, start), (row, end), false);
        if op == Operator::Change {
            ta.cut();
            self.fill_from_textarea(ta, RegisterKind::Charwise);
            self.finish_insert_entry(&Command::OperateObject(op, obj), inserted, ta);
        } else {
            self.apply_operator_on_selection(op, ta);
        }
        true
    }

    /// Find the innermost enclosing pair `(open, close)` around `col`.
    /// If the cursor is on an open bracket, that bracket is the enclosing open.
    /// Otherwise scans left with depth counting (closing chars raise depth) to
    /// find the nearest unmatched open, then scans right from that open with
    /// depth counting to find the matching close.
    fn find_enclosing_pair(
        chars: &[char],
        col: usize,
        open: char,
        close: char,
    ) -> Option<(usize, usize)> {
        // Locate the open bracket that encloses col.
        let open_idx = if chars.get(col) == Some(&open) {
            col
        } else {
            let mut depth = 0usize;
            let mut found = None;
            for i in (0..col).rev() {
                if chars[i] == close {
                    depth += 1;
                } else if chars[i] == open {
                    if depth == 0 {
                        found = Some(i);
                        break;
                    }
                    depth -= 1;
                }
            }
            found?
        };
        // Find the matching close bracket scanning right from open_idx+1.
        let mut depth = 0usize;
        let mut close_idx = None;
        for (i, &ch) in chars.iter().enumerate().skip(open_idx + 1) {
            if ch == open {
                depth += 1;
            } else if ch == close {
                if depth == 0 {
                    close_idx = Some(i);
                    break;
                }
                depth -= 1;
            }
        }
        Some((open_idx, close_idx?))
    }

    /// Returns the half-open `[start, end)` char range for `obj` centred at
    /// `col` within `chars`.
    ///
    /// NOTE: text objects are **single-line** in this implementation.
    /// Multi-line pair/quote spans are a later enhancement.
    fn object_range(chars: &[char], col: usize, obj: TextObject) -> Option<(usize, usize)> {
        if chars.is_empty() || col >= chars.len() {
            return None;
        }
        match obj {
            TextObject::Word { around } => {
                let is_word = |c: char| c.is_alphanumeric() || c == '_';
                // Expand left to the start of the word.
                let mut s = col;
                while s > 0 && is_word(chars[s - 1]) {
                    s -= 1;
                }
                // Expand right past the end of the word.
                let mut e = col;
                while e < chars.len() && is_word(chars[e]) {
                    e += 1;
                }
                if around {
                    // Also consume trailing whitespace (vim `aw` behaviour).
                    while e < chars.len() && chars[e].is_whitespace() {
                        e += 1;
                    }
                }
                Some((s, e))
            }
            TextObject::Quote { ch, around } => {
                // Collect all positions of the quote character on this line.
                let positions: Vec<usize> = chars
                    .iter()
                    .enumerate()
                    .filter(|&(_, &c)| c == ch)
                    .map(|(i, _)| i)
                    .collect();
                // Find the pair that strictly contains the cursor (p[0] <= col <= p[1]).
                // Cursor in the gap between two quoted spans returns None (no-op).
                let pair = positions
                    .chunks(2)
                    .find(|p| p.len() == 2 && p[0] <= col && col <= p[1])?;
                let (o, c) = (pair[0], pair[1]);
                if around {
                    Some((o, c + 1))
                } else {
                    Some((o + 1, c))
                }
            }
            TextObject::Pair {
                open,
                close,
                around,
            } => {
                let (o, c) = Self::find_enclosing_pair(chars, col, open, close)?;
                if around {
                    Some((o, c + 1))
                } else {
                    Some((o + 1, c))
                }
            }
        }
    }

    // ── Single-key edit helpers ──────────────────────────────────────────────

    /// Delete `count` chars at the cursor (`forward`: under-and-after, vim
    /// `x`; otherwise before, vim `X`), clamped to the current line — vim's
    /// x/X never join lines — filling the unnamed register with the deleted
    /// text (vim rule: every delete fills the register; `xp` swaps chars).
    /// Returns `false` when nothing was deleted (empty line, X at col 0).
    fn delete_chars(&mut self, forward: bool, count: usize, ta: &mut TextArea<'static>) -> bool {
        let (row, col) = super::cursor_tuple(ta);
        // Borrow, don't clone: all reads of `line` finish before the first
        // mutation, so held-down x on a long line doesn't copy it each press.
        let Some(line) = ta.lines().get(row) else {
            return false;
        };
        let line_len = line.chars().count();
        let (n, start) = if forward {
            (count.min(line_len.saturating_sub(col)), col)
        } else {
            let n = count.min(col);
            (n, col - n)
        };
        let deleted: String = line.chars().skip(start).take(n).collect();
        self.registers.fill(deleted, RegisterKind::Charwise);
        for _ in 0..n {
            if forward {
                ta.delete_next_char();
            } else {
                ta.delete_char();
            }
        }
        n > 0
    }

    /// Replace the char under the cursor with `c`, stay in Normal mode.
    fn replace_char(&mut self, c: char, ta: &mut TextArea<'static>) -> VimKeyOutcome {
        if ta.delete_next_char() {
            ta.insert_char(c);
            ta.move_cursor(CursorMove::Back);
            VimKeyOutcome::TextMutated
        } else {
            VimKeyOutcome::NoOp
        }
    }

    /// Join the next line onto the current one. `spaced` (vim `J`): the next
    /// line's leading whitespace is stripped and a single space separates the
    /// parts (none when the current line is empty or already ends in
    /// whitespace), cursor left on the join point. Raw (`gJ`): the newline is
    /// removed verbatim.
    fn join_line(ta: &mut TextArea<'static>, spaced: bool) {
        let (row, _) = super::cursor_tuple(ta);
        let lines = ta.lines();
        if row + 1 >= lines.len() {
            return;
        }
        let cur_empty = lines[row].is_empty();
        let cur_ends_ws = lines[row].chars().last().is_some_and(|c| c.is_whitespace());
        ta.move_cursor(CursorMove::End);
        ta.delete_next_char(); // removes the newline
        if !spaced {
            return;
        }
        let (r, c) = super::cursor_tuple(ta);
        let strip = ta.lines()[r]
            .chars()
            .skip(c)
            .take_while(|ch| ch.is_whitespace())
            .count();
        for _ in 0..strip {
            ta.delete_next_char();
        }
        let rest_nonempty = ta.lines()[r].chars().count() > c;
        if !cur_empty && !cur_ends_ws && rest_nonempty {
            ta.insert_char(' ');
            ta.move_cursor(CursorMove::Back);
        }
    }

    /// Toggle the case of the char under the cursor and advance one char.
    fn toggle_case_at_cursor(ta: &mut TextArea<'static>) {
        let (row, col) = super::cursor_tuple(ta);
        let flipped = ta
            .lines()
            .get(row)
            .and_then(|line| line.chars().nth(col))
            .map(Self::flip_case);
        if let Some(flipped) = flipped {
            ta.delete_next_char();
            ta.insert_str(&flipped);
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use ratatui::crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
    use ratatui_textarea::TextArea;

    fn key(c: char) -> KeyEvent {
        KeyEvent::new(KeyCode::Char(c), KeyModifiers::NONE)
    }
    fn esc() -> KeyEvent {
        KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE)
    }
    fn ta() -> TextArea<'static> {
        TextArea::from(["hello world", "second line"])
    }

    // ── Mode-entry + basic motion tests ──────────────────────────────────────

    #[test]
    fn i_enters_insert_mode() {
        let mut e = VimEngine::default();
        let mut t = ta();
        let out = e.handle_key(&key('i'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        assert_eq!(out, VimKeyOutcome::CursorOnly);
    }

    #[test]
    fn esc_returns_to_normal_and_steps_back() {
        let mut e = VimEngine::default();
        let mut t = ta();
        e.handle_key(&key('i'), &mut t);
        t.move_cursor(ratatui_textarea::CursorMove::Forward);
        t.move_cursor(ratatui_textarea::CursorMove::Forward);
        let col_before = super::super::cursor_tuple(&t).1;
        let out = e.handle_key(&esc(), &mut t);
        assert_eq!(*e.mode(), EditorMode::Normal);
        assert_eq!(out, VimKeyOutcome::CursorOnly);
        assert_eq!(super::super::cursor_tuple(&t).1, col_before - 1);
    }

    #[test]
    fn insert_mode_passes_through() {
        let mut e = VimEngine::default();
        let mut t = ta();
        e.handle_key(&key('i'), &mut t);
        let out = e.handle_key(&key('x'), &mut t);
        assert_eq!(out, VimKeyOutcome::PassThrough);
    }

    #[test]
    fn l_moves_right_cursor_only() {
        let mut e = VimEngine::default();
        let mut t = ta();
        let out = e.handle_key(&key('l'), &mut t);
        assert_eq!(out, VimKeyOutcome::CursorOnly);
        assert_eq!(super::super::cursor_tuple(&t), (0, 1));
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn a_enters_insert_after_cursor() {
        let mut e = VimEngine::default();
        let mut t = ta();
        e.handle_key(&key('a'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        assert_eq!(super::super::cursor_tuple(&t), (0, 1));
    }

    #[test]
    fn o_opens_line_below_in_insert() {
        let mut e = VimEngine::default();
        let mut t = ta();
        let out = e.handle_key(&key('o'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        assert_eq!(out, VimKeyOutcome::TextMutated);
        assert_eq!(t.lines().len(), 3);
        assert_eq!(super::super::cursor_tuple(&t).0, 1);
    }

    #[test]
    fn reset_returns_to_normal_from_insert() {
        let mut e = VimEngine::default();
        let mut t = ta();
        e.handle_key(&key('i'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        e.reset_to_normal();
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn unknown_normal_key_is_noop() {
        let mut e = VimEngine::default();
        let mut t = ta();
        let out = e.handle_key(&key('z'), &mut t);
        assert_eq!(out, VimKeyOutcome::NoOp);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    // ── Count accumulation tests ─────────────────────────────────────────────

    #[test]
    fn count_accumulates_then_moves() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcdef"]);
        e.handle_key(&key('3'), &mut t);
        e.handle_key(&key('l'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 3));
        // pending cleared after the motion
        e.handle_key(&key('l'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 4));
    }

    #[test]
    fn zero_without_count_is_line_start() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcdef"]);
        e.handle_key(&key('l'), &mut t);
        e.handle_key(&key('l'), &mut t);
        e.handle_key(&key('0'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 0));
    }

    // ── gg/G motion tests ────────────────────────────────────────────────────

    #[test]
    #[allow(non_snake_case)]
    fn gg_and_G_jump_file_ends() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('G'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t).0, 2);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('g'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t).0, 0);
    }

    #[test]
    fn pending_g_cancels_on_unmapped_key() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('G'), &mut t); // go to last line
        assert_eq!(super::super::cursor_tuple(&t).0, 2);
        e.handle_key(&key('g'), &mut t); // start gg
        e.handle_key(&key('z'), &mut t); // unmapped → should cancel pending g
        e.handle_key(&key('g'), &mut t); // lone g, NOT gg
        assert_eq!(
            super::super::cursor_tuple(&t).0,
            2,
            "stray g after cancelled prefix must not jump to file start"
        );
    }

    #[test]
    fn pending_g_cleared_through_insert() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('G'), &mut t);
        e.handle_key(&key('g'), &mut t); // start gg
        e.handle_key(&key('a'), &mut t); // enter insert (should clear pending_g)
        e.handle_key(&KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE), &mut t);
        e.handle_key(&key('g'), &mut t); // lone g
        assert_eq!(
            super::super::cursor_tuple(&t).0,
            2,
            "g after insert must not complete a stale gg"
        );
    }

    // ── Operator + motion tests ──────────────────────────────────────────────

    #[test]
    fn dw_deletes_word() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello world"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('w'), &mut t);
        assert_eq!(t.lines(), &["world"]);
    }

    #[test]
    fn dd_deletes_line_linewise() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &["two", "three"]);
        let reg = e.registers.read().expect("dd must fill the register");
        assert_eq!(reg.kind, RegisterKind::Linewise);
        assert_eq!(reg.text, "one\n");
    }

    #[test]
    fn yy_then_p_duplicates_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two"]);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('p'), &mut t);
        assert_eq!(t.lines(), &["one", "one", "two"]);
    }

    #[test]
    fn cw_deletes_word_and_enters_insert() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello world"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('w'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        // Vim `cw` = `ce`: deletes up to end of word (exclusive of trailing
        // space), so " world" remains (space preserved). This matches vim's
        // actual cw = ce behaviour.
        assert_eq!(t.lines(), &[" world"]);
    }

    // ── Linewise delete/paste tests ──────────────────────────────────────────

    #[test]
    fn charwise_p_pastes_after_cursor() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        // yank the first char with `yl`
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('l'), &mut t);
        e.handle_key(&key('p'), &mut t);
        assert_eq!(t.lines(), &["aabc"]);
    }

    #[test]
    fn dd_on_last_line_removes_it() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('G'), &mut t); // to last line
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &["one", "two"]);
    }

    #[test]
    fn dd_on_only_line_leaves_empty() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["only"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &[""]);
    }

    #[test]
    fn linewise_2p_inserts_two_copies() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two"]);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('y'), &mut t); // yank "one" linewise
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('p'), &mut t);
        assert_eq!(t.lines(), &["one", "one", "one", "two"]);
    }

    #[test]
    fn yy_last_line_then_p_duplicates() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two"]);
        e.handle_key(&key('G'), &mut t); // last line "two"
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('p'), &mut t);
        assert_eq!(t.lines(), &["one", "two", "two"]);
    }

    // ── Single-key edit tests ────────────────────────────────────────────────

    #[test]
    fn x_deletes_char_under_cursor() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('x'), &mut t);
        assert_eq!(t.lines(), &["bc"]);
    }

    #[test]
    fn r_replaces_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('r'), &mut t);
        e.handle_key(&key('Z'), &mut t);
        assert_eq!(t.lines(), &["Zbc"]);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn u_undoes_last_edit() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('x'), &mut t);
        e.handle_key(&key('u'), &mut t);
        assert_eq!(t.lines(), &["abc"]);
    }

    #[test]
    fn tilde_toggles_case() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('~'), &mut t);
        assert_eq!(t.lines(), &["Abc"]);
    }

    // ── Find (f/t/;/,) tests ─────────────────────────────────────────────────

    #[test]
    fn f_moves_to_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello, world"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key(','), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 5));
    }

    #[test]
    fn df_deletes_through_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello, world"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key(','), &mut t);
        assert_eq!(t.lines(), &[" world"]);
    }

    #[test]
    fn t_stops_before_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello, world"]);
        e.handle_key(&key('t'), &mut t);
        e.handle_key(&key(','), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 4)); // on 'o', before ','
    }

    #[test]
    fn semicolon_repeats_find() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a.b.c.d"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('.'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t).1, 1);
        e.handle_key(&key(';'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t).1, 3);
    }

    // ── Text object tests ────────────────────────────────────────────────────

    #[test]
    fn diw_deletes_inner_word() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar baz"]);
        // cursor on 'b' of "bar"
        e.handle_key(&key('w'), &mut t);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('w'), &mut t);
        assert_eq!(t.lines(), &["foo  baz"]);
    }

    #[test]
    fn ci_quote_changes_inside_quotes() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["say \"hi\" now"]);
        // move onto the text inside quotes: f then h lands on 'h' (col 5)
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('h'), &mut t);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('"'), &mut t);
        assert_eq!(t.lines(), &["say \"\" now"]);
        assert_eq!(*e.mode(), EditorMode::Insert);
    }

    #[test]
    fn di_paren_deletes_inside_parens() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo(bar)baz"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('('), &mut t); // cursor on '('
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('('), &mut t);
        assert_eq!(t.lines(), &["foo()baz"]);
    }

    #[test]
    fn daw_deletes_word_and_trailing_space() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar baz"]);
        e.handle_key(&key('w'), &mut t); // onto "bar"
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('a'), &mut t);
        e.handle_key(&key('w'), &mut t);
        assert_eq!(t.lines(), &["foo baz"]);
    }

    // ── Matching pair (%) tests ──────────────────────────────────────────────

    #[test]
    fn percent_jumps_to_matching_paren() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo(bar)baz"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('('), &mut t); // cursor on '('
        e.handle_key(&key('%'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 7)); // matching ')'
    }

    #[test]
    fn percent_jumps_back_from_close() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo(bar)baz"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key(')'), &mut t); // cursor on ')'
        e.handle_key(&key('%'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 3)); // back to '('
    }

    #[test]
    fn percent_handles_nested() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["(a(b)c)"]);
        // cursor on outer '(' at col 0
        e.handle_key(&key('%'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 6)); // matching outer ')'
    }

    // ── Visual mode tests ────────────────────────────────────────────────────

    /// Charwise Visual is inclusive of the cursor char. `v` + 2×`l` leaves
    /// the cursor on col 2 ('l'); the inclusive range covers cols 0,1,2 = "hel".
    #[test]
    fn v_motion_d_deletes_selection() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('v'), &mut t); // anchor col 0
        e.handle_key(&key('l'), &mut t); // cursor → col 1
        e.handle_key(&key('l'), &mut t); // cursor → col 2, inclusive covers "hel"
        e.handle_key(&key('d'), &mut t); // delete "hel"
        assert_eq!(t.lines(), &["lo"]); // inclusive: deletes cols 0,1,2 ("hel")
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    #[allow(non_snake_case)]
    fn V_then_d_deletes_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two"]);
        e.handle_key(&key('V'), &mut t);
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &["two"]);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    /// Inclusive yank: v + l (cursor col 1) yanks "he" (2 chars, inclusive).
    /// After p pastes the yanked text, buffer grew by 2.
    #[test]
    fn visual_y_yanks_and_returns_to_normal() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('v'), &mut t); // anchor col 0
        e.handle_key(&key('l'), &mut t); // cursor col 1, inclusive selection "he"
        e.handle_key(&key('y'), &mut t); // yank "he" (2 chars), mode → Normal
        assert_eq!(*e.mode(), EditorMode::Normal);
        // p pastes the yanked "he" after current cursor
        let before_len: usize = t.lines().iter().map(|l| l.len()).sum();
        e.handle_key(&key('p'), &mut t);
        let after_len: usize = t.lines().iter().map(|l| l.len()).sum();
        // buffer grew by exactly 2 chars (the yanked "he")
        assert_eq!(after_len, before_len + 2);
    }

    #[test]
    fn visual_esc_cancels_and_returns_normal() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('l'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Visual);
        e.handle_key(&esc(), &mut t);
        assert_eq!(*e.mode(), EditorMode::Normal);
        // selection should be cancelled
        assert!(t.selection_range().is_none());
    }

    #[test]
    fn visual_c_enters_insert_after_delete() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('v'), &mut t); // anchor col 0
        e.handle_key(&key('l'), &mut t); // cursor col 1, inclusive covers "he"
        e.handle_key(&key('c'), &mut t); // delete "he" (inclusive), enter Insert
        assert_eq!(*e.mode(), EditorMode::Insert);
        assert_eq!(t.lines(), &["llo"]); // inclusive: deletes cols 0,1 ("he")
    }

    // ── Indent/outdent tests ─────────────────────────────────────────────────

    #[test]
    fn indent_line_adds_spaces() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        e.handle_key(&key('>'), &mut t);
        e.handle_key(&key('>'), &mut t);
        assert_eq!(t.lines(), &["    x"]);
    }

    #[test]
    fn indent_keeps_cursor_over_same_char() {
        // regression: >> left the cursor one row BELOW the indented block;
        // the cursor must stay over the char it sat on, shifted with the
        // indent (neovim behavior).
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('l'), &mut t); // onto 'n' (col 1)
        e.handle_key(&key('>'), &mut t);
        e.handle_key(&key('>'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 5)); // still on 'n'
        // counted form too: cursor stays on the first line of the block
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('>'), &mut t);
        e.handle_key(&key('>'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t).0, 0);
    }

    #[test]
    fn outdent_keeps_cursor_over_same_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["    x"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('x'), &mut t); // ON 'x' (col 4)
        e.handle_key(&key('<'), &mut t);
        e.handle_key(&key('<'), &mut t);
        assert_eq!(t.lines(), &["x"]);
        assert_eq!(super::super::cursor_tuple(&t).1, 0); // still on 'x'
    }

    #[test]
    fn outdent_removes_spaces() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["        x"]); // 8 spaces
        e.handle_key(&key('<'), &mut t);
        e.handle_key(&key('<'), &mut t);
        assert_eq!(t.lines(), &["    x"]); // removed 4
    }

    #[test]
    fn pending_hint_shows_operator_and_count() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('d'), &mut t);
        assert_eq!(e.pending_hint().as_deref(), Some("2d"));
    }

    // ── Dot-repeat tests ─────────────────────────────────────────────────────

    #[test]
    fn dot_repeats_x() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcdef"]);
        e.handle_key(&key('x'), &mut t);
        e.handle_key(&key('.'), &mut t);
        assert_eq!(t.lines(), &["cdef"]);
    }

    #[test]
    fn dot_repeats_dw() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one two three four"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('w'), &mut t); // delete "one "
        e.handle_key(&key('.'), &mut t); // delete "two "
        assert_eq!(t.lines(), &["three four"]);
    }

    #[test]
    fn dot_repeats_change_with_typed_text() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar"]);
        // cw -> type "X" -> Esc, then move to next word and dot
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('w'), &mut t); // cw: deletes "foo" (cw=ce keeps trailing space), enters Insert at col 0
        // simulate the user typing "X" via the host PassThrough path:
        t.insert_str("X");
        e.handle_key(&esc(), &mut t); // capture "X"
        e.handle_key(&key('w'), &mut t); // move to "bar"
        e.handle_key(&key('.'), &mut t); // repeat cw+X
        assert_eq!(t.lines(), &["X X"]);
    }

    #[test]
    fn dot_repeats_multiline_change() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('w'), &mut t); // cw on "foo" → Insert at col 0
        t.insert_str("a");
        t.insert_newline();
        t.insert_str("b"); // typed "a\nb"
        e.handle_key(&esc(), &mut t); // captures "a\nb"
        // Buffer is now ["a", "b bar"]; cursor stepped back to col 0 of row 1 ("b bar").
        // Confirm the multi-line buffer state from the insert:
        assert_eq!(t.lines(), &["a", "b bar"]);

        // Verify replay: position on "bar", run `.`, should produce "a\nb" again.
        // Move to word "bar" (it is at col 2 of row 1).
        e.handle_key(&key('w'), &mut t); // move to "bar" (word-forward from "b" → "bar")
        e.handle_key(&key('.'), &mut t); // replay: cw on "bar" → insert "a\nb"
        // After replay the buffer should have "a\nb" inserted in place of "bar":
        // row 1 was "b bar", cw from "bar" removes "bar", inserts "a\nb" → ["a", "b a", "b"]
        assert!(
            t.lines().len() >= 3,
            "replay of multiline insert should produce >=3 lines: {:?}",
            t.lines()
        );
    }

    // ── space_leads predicate tests ──────────────────────────────────────────

    #[test]
    fn space_leads_only_in_clean_normal() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        assert!(e.space_leads());
        e.handle_key(&key('d'), &mut t); // operator pending
        assert!(!e.space_leads());
        e.handle_key(&key('w'), &mut t); // completes dw, clears pending
        assert!(e.space_leads());
        e.handle_key(&key('i'), &mut t); // insert
        assert!(!e.space_leads());
    }

    // ── Host-action tests ────────────────────────────────────────────────────

    #[test]
    fn colon_emits_open_palette() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        assert_eq!(
            e.handle_key(&key(':'), &mut t),
            VimKeyOutcome::Host(VimHostAction::OpenPalette)
        );
    }

    #[test]
    fn slash_emits_open_search_forward() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        assert_eq!(
            e.handle_key(&key('/'), &mut t),
            VimKeyOutcome::Host(VimHostAction::OpenSearch { forward: true })
        );
    }

    #[test]
    #[allow(non_snake_case)]
    fn n_and_N_emit_search_nav() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        assert_eq!(
            e.handle_key(&key('n'), &mut t),
            VimKeyOutcome::Host(VimHostAction::SearchNext)
        );
        assert_eq!(
            e.handle_key(&key('N'), &mut t),
            VimKeyOutcome::Host(VimHostAction::SearchPrev)
        );
    }

    // ── Mouse → Visual mode tests ────────────────────────────────────────────

    #[test]
    fn mouse_selection_enters_and_leaves_visual() {
        let mut e = VimEngine::default();
        e.sync_mouse_selection(true);
        assert_eq!(*e.mode(), EditorMode::Visual);
        e.sync_mouse_selection(false);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn mouse_no_selection_in_normal_stays_normal() {
        let mut e = VimEngine::default();
        e.sync_mouse_selection(false);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn mouse_does_not_disturb_insert() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        e.handle_key(&key('i'), &mut t); // Insert
        e.sync_mouse_selection(true);
        assert_eq!(*e.mode(), EditorMode::Insert); // mouse doesn't yank Insert into Visual
    }

    // ── Bug-fix regression tests ─────────────────────────────────────────────

    #[test]
    fn di_paren_on_empty_line_does_not_panic() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from([""]); // empty line
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('('), &mut t); // must not panic; no-op
        assert_eq!(t.lines(), &[""]);
    }

    #[test]
    fn esc_clears_pending_g_in_normal() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('G'), &mut t); // last line
        assert_eq!(super::super::cursor_tuple(&t).0, 2);
        e.handle_key(&key('g'), &mut t); // start gg
        e.handle_key(&KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE), &mut t); // cancel
        e.handle_key(&key('g'), &mut t); // lone g
        assert_eq!(
            super::super::cursor_tuple(&t).0,
            2,
            "Esc must cancel pending g"
        );
    }

    #[test]
    fn esc_clears_pending_operator_object_in_normal() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar baz"]);
        e.handle_key(&key('d'), &mut t); // operator pending
        e.handle_key(&key('i'), &mut t); // object kind pending (NOT insert — operator pending)
        e.handle_key(&KeyEvent::new(KeyCode::Esc, KeyModifiers::NONE), &mut t); // cancel
        // buffer unchanged (no diw happened)
        assert_eq!(t.lines(), &["foo bar baz"]);
        // and we're back to clean Normal: a plain motion works, mode still Normal
        e.handle_key(&key('w'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Normal);
        assert_eq!(
            t.lines(),
            &["foo bar baz"],
            "w after Esc must be a motion, not diw"
        );
    }

    // ── Bug A: di( on nested parens ─────────────────────────────────────────

    #[test]
    fn di_paren_nested_selects_inner_of_outer() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["((x))"]);
        // cursor at col 0 (outer '(')
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('('), &mut t);
        assert_eq!(t.lines(), &["()"]); // outer kept, inner content "(x)" deleted
    }

    #[test]
    fn di_paren_from_inside_nested() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["((x))"]);
        e.handle_key(&key('l'), &mut t); // col1 (inner '(')
        e.handle_key(&key('l'), &mut t); // col2 ('x')
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('('), &mut t);
        assert_eq!(t.lines(), &["(())"]); // inner content "x" deleted
    }

    // ── Bug B: di" in gap between pairs ─────────────────────────────────────

    #[test]
    fn di_quote_in_gap_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["\"foo\" \"bar\""]);
        // move cursor to the space (col 5) between the two strings
        for _ in 0..5 {
            e.handle_key(&key('l'), &mut t);
        }
        assert_eq!(super::super::cursor_tuple(&t).1, 5);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('"'), &mut t);
        assert_eq!(t.lines(), &["\"foo\" \"bar\""]); // unchanged (no-op)
    }

    #[test]
    fn di_quote_inside_still_works() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["\"foo\" \"bar\""]);
        for _ in 0..7 {
            e.handle_key(&key('l'), &mut t);
        } // inside "bar"
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('"'), &mut t);
        assert_eq!(t.lines(), &["\"foo\" \"\""]); // bar deleted, foo intact
    }

    // ── Bug C: df<last-char> must not join next line ─────────────────────────

    #[test]
    fn df_last_char_does_not_join_next_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc", "xyz"]);
        // cursor at (0,0); df c  → delete through the 'c' (last char of line 0)
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('c'), &mut t);
        assert_eq!(t.lines(), &["", "xyz"]); // line 0 emptied, newline + line 1 intact
    }

    // ── Bug D: cc on a single-line buffer ────────────────────────────────────

    #[test]
    fn cc_single_line_leaves_one_empty_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('c'), &mut t);
        assert_eq!(t.lines(), &[""]);
        assert_eq!(*e.mode(), EditorMode::Insert);
    }

    #[test]
    fn cc_middle_line_still_works() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('j'), &mut t); // line "two"
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('c'), &mut t);
        assert_eq!(t.lines(), &["one", "", "three"]);
        assert_eq!(*e.mode(), EditorMode::Insert);
    }

    // ── Bug E: r on empty line must be no-op ────────────────────────────────

    #[test]
    fn r_on_empty_line_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from([""]);
        e.handle_key(&key('r'), &mut t);
        let out = e.handle_key(&key('Z'), &mut t);
        assert_eq!(out, VimKeyOutcome::NoOp);
        assert_eq!(t.lines(), &[""]);
    }

    // ── P2.G: charwise Visual inclusive tests ────────────────────────────────

    #[test]
    fn visual_v_then_d_deletes_char_under_cursor() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('v'), &mut t); // select just 'a' (cursor col0)
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &["bc"]); // 'a' deleted (inclusive of cursor char)
    }

    #[test]
    fn visual_e_then_d_inclusive() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello world"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t); // cursor on 'o' col4
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &[" world"]); // "hello" deleted inclusive
    }

    // ── Bug fix: vim `e` must land ON the last word char (inclusive) ─────────

    #[test]
    fn e_lands_on_last_word_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello world"]);
        e.handle_key(&key('e'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 4)); // 'o', last char of "hello"
    }

    #[test]
    fn e_twice_reaches_second_word_end() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello world"]);
        e.handle_key(&key('e'), &mut t);
        e.handle_key(&key('e'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 10)); // 'd', last char of "world"
    }

    #[test]
    fn de_deletes_to_word_end_inclusive() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello world"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('e'), &mut t);
        assert_eq!(t.lines(), &[" world"]); // deletes "hello" inclusive of 'o'
    }

    // ── Bug fix: vim yank leaves cursor at selection start; charwise p never wraps ──

    #[test]
    fn visual_y_leaves_cursor_at_selection_start() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar", "baz"]);
        for _ in 0..4 {
            e.handle_key(&key('l'), &mut t);
        } // onto 'b' of "bar" (col 4)
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t); // select "bar"
        e.handle_key(&key('y'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 4)); // cursor at start of selection, not the end
    }

    #[test]
    fn charwise_p_after_eol_word_does_not_touch_next_line() {
        // reproduce the user's bug: yank an end-of-line word, paste, must NOT hit the line below
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar", "baz"]);
        for _ in 0..4 {
            e.handle_key(&key('l'), &mut t);
        } // 'b' of "bar"
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t); // select "bar" (end of line 0)
        e.handle_key(&key('y'), &mut t); // yank; cursor → col 4
        e.handle_key(&key('p'), &mut t); // paste after cursor char 'b'
        assert_eq!(t.lines()[1], "baz"); // line below UNTOUCHED
        assert_eq!(t.lines().len(), 2); // no new line, no merge
        assert_eq!(t.lines()[0], "foo bbarar"); // "bar" pasted after 'b' on line 0 (vim p-after)
    }

    #[test]
    fn charwise_p_at_line_end_appends_same_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab", "cd"]);
        // yank "ab" charwise via v e y
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t); // select "ab"
        e.handle_key(&key('y'), &mut t); // cursor → col 0
        e.handle_key(&key('$'), &mut t); // to last char of line 0 ('b')
        e.handle_key(&key('p'), &mut t); // append "ab" after 'b'
        assert_eq!(t.lines()[0], "abab");
        assert_eq!(t.lines()[1], "cd"); // line below untouched
    }

    // ── Visual p: replace selection with register ────────────────────────────

    #[test]
    fn visual_p_replaces_charwise_selection() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar"]);
        // yank "foo" (v e y at col 0) → register = "foo", cursor back to col 0
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t);
        e.handle_key(&key('y'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 0));
        // select "bar" and paste over it
        for _ in 0..4 {
            e.handle_key(&key('l'), &mut t);
        } // onto 'b' (col 4)
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t); // select "bar"
        e.handle_key(&key('p'), &mut t);
        assert_eq!(t.lines(), &["foo foo"]); // "bar" replaced by "foo"
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn visual_p_yanks_replaced_selection() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar"]);
        // yank "foo"
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t);
        e.handle_key(&key('y'), &mut t); // reg = "foo", cursor col 0
        // select "bar" and paste over it
        for _ in 0..4 {
            e.handle_key(&key('l'), &mut t);
        } // col 4 'b'
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t);
        e.handle_key(&key('p'), &mut t); // "bar" replaced by "foo"; "bar" now yanked
        assert_eq!(t.lines(), &["foo foo"]);
        // now paste the replaced "bar" at end of line to prove it's in the register
        e.handle_key(&key('$'), &mut t); // last char ('o', col 6)
        e.handle_key(&key('p'), &mut t); // append "bar" after it
        assert_eq!(t.lines(), &["foo foobar"]);
    }

    // ── Cheatsheet motions: g_/5G/5gg, ge/gE, WORD (W/E/B) ───────────────────

    #[test]
    fn g_underscore_jumps_to_last_non_blank() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hi there   "]);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('_'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 7)); // the final 'e'
    }

    #[test]
    fn d_g_underscore_deletes_through_last_non_blank() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar  "]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('_'), &mut t);
        assert_eq!(t.lines(), &["  "]); // inclusive of the 'r'
    }

    #[test]
    #[allow(non_snake_case)]
    fn count_G_and_count_gg_go_to_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["1", "2", "3", "4", "5", "6"]);
        e.handle_key(&key('5'), &mut t);
        e.handle_key(&key('G'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t).0, 4); // line 5
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('g'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t).0, 1); // line 2
    }

    #[test]
    #[allow(non_snake_case)]
    fn d_count_G_deletes_lines_through_target() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('G'), &mut t); // delete lines 1..=2 (linewise)
        assert_eq!(t.lines(), &["three"]);
    }

    #[test]
    fn ge_jumps_to_previous_word_end() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar"]);
        e.handle_key(&key('$'), &mut t); // on 'r' (col 6)
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('e'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 2)); // 'o' of foo
    }

    #[test]
    fn ge_stops_at_class_change() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo.bar"]);
        e.handle_key(&key('$'), &mut t); // 'r' (col 6)
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('e'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 3)); // the '.'
    }

    #[test]
    #[allow(non_snake_case)]
    fn gE_ignores_punctuation_boundaries() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["aa bb.cc dd"]);
        e.handle_key(&key('$'), &mut t); // last 'd' (col 10)
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('E'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 7)); // end of "bb.cc"
    }

    #[test]
    fn ge_at_buffer_start_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo"]);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('e'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 0));
    }

    #[test]
    fn dge_deletes_backward_inclusive_of_cursor() {
        // vim: dge eats from the previous word end through the cursor char
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc def"]);
        e.handle_key(&key('$'), &mut t); // on 'f'
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('e'), &mut t);
        assert_eq!(t.lines(), &["ab"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn W_treats_punctuated_run_as_one_word() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo.bar baz"]);
        e.handle_key(&key('W'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 8)); // 'b' of baz
    }

    #[test]
    #[allow(non_snake_case)]
    fn E_jumps_to_end_of_WORD() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo.bar baz"]);
        e.handle_key(&key('E'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 6)); // 'r' of foo.bar
    }

    #[test]
    #[allow(non_snake_case)]
    fn B_jumps_to_WORD_start() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo.bar baz"]);
        e.handle_key(&key('W'), &mut t); // col 8
        e.handle_key(&key('B'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 0));
    }

    #[test]
    #[allow(non_snake_case)]
    fn W_crosses_lines_and_stops_at_empty_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo", "", "bar"]);
        e.handle_key(&key('W'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (1, 0)); // empty line is a stop
        e.handle_key(&key('W'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (2, 0));
    }

    #[test]
    #[allow(non_snake_case)]
    fn dW_deletes_whole_WORD() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo.bar baz"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('W'), &mut t);
        assert_eq!(t.lines(), &["baz"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn cW_acts_like_cE() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo.bar baz"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('W'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        assert_eq!(t.lines(), &[" baz"]); // trailing space preserved (cW = cE)
    }

    // ── Awaiting + replace-stack fixes ───────────────────────────────────────

    #[test]
    fn hint_shows_object_scope_mid_sequence() {
        // regression: `diw` in flight showed "d" instead of "di"
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('i'), &mut t);
        assert_eq!(e.pending_hint().as_deref(), Some("di"));
    }

    #[test]
    fn hint_shows_actual_find_key() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo"]);
        e.handle_key(&key('T'), &mut t);
        assert_eq!(e.pending_hint().as_deref(), Some("T")); // was always 'f'
    }

    #[test]
    fn replace_backspace_restores_overwritten_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('R'), &mut t);
        e.handle_key(&key('X'), &mut t); // 'a' → X
        e.handle_key(&key('Y'), &mut t); // 'b' → Y
        e.handle_key(
            &KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE),
            &mut t,
        );
        e.handle_key(&esc(), &mut t);
        assert_eq!(t.lines(), &["Xbc"]); // 'b' restored (vim replace stack)
    }

    #[test]
    fn replace_backspace_removes_appended_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a"]);
        e.handle_key(&key('R'), &mut t);
        e.handle_key(&key('X'), &mut t); // 'a' → X
        e.handle_key(&key('Y'), &mut t); // appended past EOL
        e.handle_key(
            &KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE),
            &mut t,
        );
        e.handle_key(&esc(), &mut t);
        assert_eq!(t.lines(), &["X"]); // appended char removed, not restored
    }

    // ── Pure WORD-scanner unit tests (no TextArea needed) ────────────────────

    fn buf(lines: &[&str]) -> Vec<String> {
        lines.iter().map(|s| s.to_string()).collect()
    }

    #[test]
    fn pure_word_forward_big_positions() {
        let b = buf(&["foo.bar baz"]);
        assert_eq!(VimEngine::word_forward_big(&b, (0, 0)), (0, 8));
        let b = buf(&["foo", "", "bar"]);
        assert_eq!(VimEngine::word_forward_big(&b, (0, 0)), (1, 0)); // empty-line stop
        assert_eq!(VimEngine::word_forward_big(&b, (1, 0)), (2, 0));
    }

    #[test]
    fn pure_word_back_big_positions() {
        let b = buf(&["foo.bar baz"]);
        assert_eq!(VimEngine::word_back_big(&b, (0, 8)), (0, 0));
        assert_eq!(VimEngine::word_back_big(&b, (0, 0)), (0, 0)); // fails in place
    }

    #[test]
    fn pure_word_end_big_positions() {
        let b = buf(&["foo.bar baz"]);
        assert_eq!(VimEngine::word_end_big(&b, (0, 0)), Some((0, 6)));
        assert_eq!(VimEngine::word_end_big(&b, (0, 10)), None); // nothing ahead
    }

    #[test]
    fn pure_word_end_back_positions() {
        let b = buf(&["foo.bar"]);
        assert_eq!(VimEngine::word_end_back(&b, (0, 6), false), Some((0, 3))); // class change
        assert_eq!(VimEngine::word_end_back(&b, (0, 6), true), None); // one WORD, no prev end
        assert_eq!(VimEngine::word_end_back(&b, (0, 0), false), None); // buffer start
    }

    // ── Holistic-review fixes ────────────────────────────────────────────────

    #[test]
    fn visual_counted_motion_extends_by_count() {
        // regression: the 5G translation consumed the count for EVERY motion
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcdef"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('3'), &mut t);
        e.handle_key(&key('l'), &mut t); // cursor → col 3, inclusive covers "abcd"
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &["ef"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn gUu_aborts_without_running_undo() {
        // vim: a mismatched key after a pending operator cancels everything
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab"]);
        e.handle_key(&key('x'), &mut t); // real change → "b"
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('U'), &mut t); // Uppercase pending
        e.handle_key(&key('u'), &mut t); // mismatch — must NOT run Undo
        assert_eq!(t.lines(), &["b"]); // x not reverted
    }

    #[test]
    fn dx_and_dp_abort_with_operator_pending() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('l'), &mut t); // register = "a"
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('x'), &mut t); // vim aborts — nothing deleted
        assert_eq!(t.lines(), &["abc"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('p'), &mut t); // vim aborts — nothing pasted
        assert_eq!(t.lines(), &["abc"]);
    }

    #[test]
    fn dge_at_buffer_start_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('e'), &mut t); // motion fails → whole op no-op
        assert_eq!(t.lines(), &["foo"]);
    }

    #[test]
    fn gugu_doubled_g_form_runs_linewise() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ABC def"]);
        for c in "gugu".chars() {
            e.handle_key(&key(c), &mut t);
        }
        assert_eq!(t.lines(), &["abc def"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn visual_J_joins_selected_lines_with_space() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a", "b", "c"]);
        e.handle_key(&key('V'), &mut t);
        e.handle_key(&key('j'), &mut t);
        e.handle_key(&key('j'), &mut t); // select all three
        e.handle_key(&key('J'), &mut t);
        assert_eq!(t.lines(), &["a b c"]);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    #[allow(non_snake_case)]
    fn visual_gJ_joins_selected_lines_raw() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a", "  b"]);
        e.handle_key(&key('V'), &mut t);
        e.handle_key(&key('j'), &mut t);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('J'), &mut t);
        assert_eq!(t.lines(), &["a  b"]); // verbatim, indent kept
    }

    #[test]
    #[allow(non_snake_case)]
    fn replace_mode_arrows_move_cursor() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcd"]);
        e.handle_key(&key('R'), &mut t);
        e.handle_key(&KeyEvent::new(KeyCode::Right, KeyModifiers::NONE), &mut t);
        e.handle_key(&KeyEvent::new(KeyCode::Right, KeyModifiers::NONE), &mut t);
        e.handle_key(&key('X'), &mut t); // overwrite 'c'
        e.handle_key(&esc(), &mut t);
        assert_eq!(t.lines(), &["abXd"]);
        // capture restarted at the movement target: '.' overwrites one char
        e.handle_key(&key('0'), &mut t);
        e.handle_key(&key('.'), &mut t);
        assert_eq!(t.lines(), &["XbXd"]);
    }

    #[test]
    fn esc_from_insert_clears_stray_selection() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('i'), &mut t);
        // simulate a mouse drag mid-insert leaving a live selection
        t.start_selection();
        t.move_cursor(ratatui_textarea::CursorMove::Forward);
        e.handle_key(&esc(), &mut t);
        assert!(
            t.selection_range().is_none(),
            "Esc must drop the stray selection"
        );
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn guu_undoes_in_one_step() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["Mixed Case Line"]);
        for c in "guu".chars() {
            e.handle_key(&key(c), &mut t);
        }
        assert_eq!(t.lines(), &["mixed case line"]);
        e.handle_key(&key('u'), &mut t); // single undo restores...
        e.handle_key(&key('u'), &mut t); // (cut+insert = 2 textarea edits)
        assert_eq!(t.lines(), &["Mixed Case Line"]);
    }

    // ── Visual g~ (case toggle; bare ~ is auto-surround) ─────────────────────

    #[test]
    fn visual_g_tilde_toggles_case_of_selection() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["FooBar"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t); // select all of "FooBar"
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('~'), &mut t);
        assert_eq!(t.lines(), &["fOObAR"]);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn visual_bare_tilde_still_passes_through_for_surround() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["FooBar"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('e'), &mut t);
        let out = e.handle_key(&key('~'), &mut t);
        assert_eq!(out, VimKeyOutcome::PassThrough); // host auto-surround wraps
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    // ── Case operators gu/gU/g~ ──────────────────────────────────────────────

    #[test]
    fn guw_lowercases_word() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["HELLO world"]);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('u'), &mut t);
        e.handle_key(&key('w'), &mut t);
        assert_eq!(t.lines(), &["hello world"]);
        assert_eq!(super::super::cursor_tuple(&t), (0, 0)); // cursor at start
    }

    #[test]
    #[allow(non_snake_case)]
    fn gU_iw_uppercases_inner_word() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar baz"]);
        e.handle_key(&key('w'), &mut t); // onto "bar"
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('U'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('w'), &mut t);
        assert_eq!(t.lines(), &["foo BAR baz"]);
    }

    #[test]
    fn g_tilde_toggles_case_to_word_end() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["FooBar baz"]);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('~'), &mut t);
        e.handle_key(&key('e'), &mut t); // inclusive to end of "FooBar"
        assert_eq!(t.lines(), &["fOObAR baz"]);
    }

    #[test]
    fn guu_lowercases_whole_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["HELLO World", "NEXT"]);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('u'), &mut t);
        e.handle_key(&key('u'), &mut t);
        assert_eq!(t.lines(), &["hello world", "NEXT"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn visual_U_uppercases_selection() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('l'), &mut t);
        e.handle_key(&key('l'), &mut t); // select "hel"
        e.handle_key(&key('U'), &mut t);
        assert_eq!(t.lines(), &["HELlo"]);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }

    #[test]
    fn case_op_does_not_touch_register() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["keep CHANGE"]);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('e'), &mut t); // register = "keep"
        e.handle_key(&key('w'), &mut t); // onto "CHANGE"
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('u'), &mut t);
        e.handle_key(&key('w'), &mut t); // lowercase it
        assert_eq!(e.registers.read().unwrap().text, "keep"); // unchanged
    }

    #[test]
    #[allow(non_snake_case)]
    fn dot_repeats_gU_word() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one two"]);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('U'), &mut t);
        e.handle_key(&key('e'), &mut t); // ONE
        e.handle_key(&key('w'), &mut t); // onto "two"
        e.handle_key(&key('.'), &mut t);
        assert_eq!(t.lines(), &["ONE TWO"]);
    }

    // ── Replace mode (R) ─────────────────────────────────────────────────────

    #[test]
    #[allow(non_snake_case)]
    fn R_overwrites_chars() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcdef"]);
        e.handle_key(&key('R'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Replace);
        e.handle_key(&key('X'), &mut t);
        e.handle_key(&key('Y'), &mut t);
        e.handle_key(&esc(), &mut t);
        assert_eq!(t.lines(), &["XYcdef"]); // overwrote, didn't insert
        assert_eq!(*e.mode(), EditorMode::Normal);
        assert_eq!(super::super::cursor_tuple(&t), (0, 1)); // stepped back onto 'Y'
    }

    #[test]
    #[allow(non_snake_case)]
    fn R_appends_past_line_end() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab"]);
        e.handle_key(&key('R'), &mut t);
        for c in "XYZ".chars() {
            e.handle_key(&key(c), &mut t);
        }
        e.handle_key(&esc(), &mut t);
        assert_eq!(t.lines(), &["XYZ"]); // overwrote "ab", appended 'Z'
    }

    #[test]
    #[allow(non_snake_case)]
    fn R_is_dot_repeatable() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["aaaa bbbb"]);
        e.handle_key(&key('R'), &mut t);
        e.handle_key(&key('X'), &mut t);
        e.handle_key(&key('X'), &mut t);
        e.handle_key(&esc(), &mut t); // "XXaa bbbb"
        e.handle_key(&key('w'), &mut t); // onto "bbbb"
        e.handle_key(&key('.'), &mut t); // overwrite "bb"
        assert_eq!(t.lines(), &["XXaa XXbb"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn aborted_R_keeps_dot_register() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('x'), &mut t); // real change
        e.handle_key(&key('R'), &mut t);
        e.handle_key(&esc(), &mut t); // typed nothing
        e.handle_key(&key('.'), &mut t); // must repeat x
        assert_eq!(t.lines(), &["c"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn R_mode_does_not_pass_through() {
        // Replace mode is engine-owned: chars must never reach the host's
        // textarea path (no auto-surround under R).
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab"]);
        e.handle_key(&key('R'), &mut t);
        let out = e.handle_key(&key('('), &mut t);
        assert_eq!(out, VimKeyOutcome::TextMutated); // consumed, not PassThrough
        assert_eq!(t.lines()[0].chars().next(), Some('(')); // raw overwrite
    }

    // ── J / gJ join semantics ────────────────────────────────────────────────

    #[test]
    #[allow(non_snake_case)]
    fn J_joins_with_single_space_stripping_indent() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo", "   bar"]);
        e.handle_key(&key('J'), &mut t);
        assert_eq!(t.lines(), &["foo bar"]);
        // cursor on the join-point space (vim)
        assert_eq!(super::super::cursor_tuple(&t), (0, 3));
    }

    #[test]
    #[allow(non_snake_case)]
    fn J_adds_no_extra_space_when_line_ends_in_whitespace() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo ", "bar"]);
        e.handle_key(&key('J'), &mut t);
        assert_eq!(t.lines(), &["foo bar"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn gJ_joins_without_space() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo", "   bar"]);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('J'), &mut t);
        assert_eq!(t.lines(), &["foo   bar"]); // verbatim, indent kept
    }

    #[test]
    #[allow(non_snake_case)]
    fn three_J_joins_three_lines() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a", "b", "c"]);
        e.handle_key(&key('3'), &mut t);
        e.handle_key(&key('J'), &mut t);
        assert_eq!(t.lines(), &["a b c"]);
    }

    // ── Insert entries ───────────────────────────────────────────────────────

    #[test]
    #[allow(non_snake_case)]
    fn I_inserts_at_first_non_blank() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["    indented"]);
        e.handle_key(&key('$'), &mut t); // away from the start
        e.handle_key(&key('I'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        assert_eq!(super::super::cursor_tuple(&t), (0, 4)); // on 'i', not col 0
    }

    // ── % across lines ───────────────────────────────────────────────────────

    #[test]
    fn percent_matches_across_lines() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo (bar", "baz) qux"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('('), &mut t); // on '(' (0,4)
        e.handle_key(&key('%'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (1, 3)); // ')' on line 2
        e.handle_key(&key('%'), &mut t); // and back
        assert_eq!(super::super::cursor_tuple(&t), (0, 4));
    }

    #[test]
    fn percent_nested_across_lines() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["{a {b", "c}", "d}"]);
        e.handle_key(&key('%'), &mut t); // outer '{' at (0,0)
        assert_eq!(super::super::cursor_tuple(&t), (2, 1)); // outer '}' line 3
    }

    #[test]
    fn d_percent_deletes_across_lines_inclusive() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a(b", "c)d"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('('), &mut t); // on '('
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('%'), &mut t); // delete '(' through ')' inclusive
        assert_eq!(t.lines(), &["ad"]);
    }

    #[test]
    fn percent_unmatched_across_buffer_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["(a", "b"]);
        e.handle_key(&key('%'), &mut t); // no closing paren anywhere
        assert_eq!(super::super::cursor_tuple(&t), (0, 0));
    }

    // ── Review fixes: failed-op no-ops, dot-register protection ─────────────

    #[test]
    fn visual_c_dot_repeats_same_width() {
        // `.` after a visual change replays a same-sized change (vim), not cl
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcde fghij"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('l'), &mut t);
        e.handle_key(&key('l'), &mut t); // select "abc"
        e.handle_key(&key('c'), &mut t); // change it
        t.insert_str("X");
        e.handle_key(&esc(), &mut t); // "Xde fghij"
        e.handle_key(&key('w'), &mut t); // onto 'f'
        e.handle_key(&key('.'), &mut t); // change 3 chars "fgh" → "X"
        assert_eq!(t.lines(), &["Xde Xij"]);
    }

    #[test]
    fn count_find_is_atomic() {
        // vim 2fx with one 'x': whole motion fails, cursor stays
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a x b"]);
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('x'), &mut t);
        assert_eq!(super::super::cursor_tuple(&t), (0, 0)); // did not move
        // and with two: lands on the second
        let mut t2 = TextArea::from(["axbx"]);
        e.handle_key(&key('2'), &mut t2);
        e.handle_key(&key('f'), &mut t2);
        e.handle_key(&key('x'), &mut t2);
        assert_eq!(super::super::cursor_tuple(&t2), (0, 3));
    }

    #[test]
    fn d2fx_with_one_x_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a x b"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('x'), &mut t); // only one 'x' — vim no-ops everything
        assert_eq!(t.lines(), &["a x b"]);
    }

    #[test]
    fn reset_to_normal_clears_insert_capture() {
        // regression: stale capture from interrupted cw silently disabled
        // dot-recording for every later change
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo bar"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('w'), &mut t); // Insert, capture live
        e.reset_to_normal(); // note switch mid-insert
        e.handle_key(&key('x'), &mut t); // must record (deletes ' ')
        e.handle_key(&key('.'), &mut t); // must repeat x (deletes 'b')
        assert_eq!(t.lines(), &["ar"]); // cw left " bar"; x then . removed 2 chars
    }

    #[test]
    fn dj_on_last_line_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["only line"]);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('y'), &mut t); // register = line
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('j'), &mut t); // motion fails → whole op no-op
        assert_eq!(t.lines(), &["only line"]);
        assert_eq!(e.registers.read().unwrap().text, "only line\n"); // register kept
    }

    #[test]
    fn dk_on_first_line_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('k'), &mut t);
        assert_eq!(t.lines(), &["one", "two"]);
    }

    #[test]
    fn failed_find_op_does_not_clobber_dot() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcdef"]);
        e.handle_key(&key('x'), &mut t); // real change: delete 'a'
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('z'), &mut t); // failed find — must not record
        e.handle_key(&key('.'), &mut t); // repeats x, not the failed dfz
        assert_eq!(t.lines(), &["cdef"]);
    }

    #[test]
    fn noop_x_does_not_clobber_dot() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one two three", ""]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('w'), &mut t); // delete "one "
        e.handle_key(&key('j'), &mut t); // empty line
        let out = e.handle_key(&key('x'), &mut t); // no-op
        assert_eq!(out, VimKeyOutcome::NoOp); // host must not bump content
        e.handle_key(&key('k'), &mut t);
        e.handle_key(&key('.'), &mut t); // repeats dw, not the no-op x
        assert_eq!(t.lines(), &["three", ""]);
    }

    #[test]
    fn d_percent_without_pair_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('%'), &mut t); // no bracket under cursor
        assert_eq!(t.lines(), &["abc"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('%'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Normal); // failed c% must not enter Insert
    }

    #[test]
    fn visual_inner_empty_pair_is_noop() {
        // regression: vi( on "()" widened onto the ')' and deleted it
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo()bar"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('('), &mut t); // cursor on '('
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('('), &mut t); // empty object: selection unchanged
        e.handle_key(&esc(), &mut t);
        assert_eq!(t.lines(), &["foo()bar"]);
    }

    #[test]
    fn aborted_insert_keeps_dot_register() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('x'), &mut t); // real change
        e.handle_key(&key('i'), &mut t); // changed mind
        e.handle_key(&esc(), &mut t); // nothing typed — not a change
        e.handle_key(&key('.'), &mut t); // must repeat x
        assert_eq!(t.lines(), &["c"]);
    }

    #[test]
    fn o_then_esc_is_still_dot_repeatable() {
        // vim: o<Esc> IS a change (the opened line); `.` opens another
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        e.handle_key(&key('o'), &mut t);
        e.handle_key(&esc(), &mut t);
        e.handle_key(&key('.'), &mut t);
        assert_eq!(t.lines().len(), 3);
    }

    // ── Visual mode: shared motion/object machinery ──────────────────────────

    #[test]
    fn visual_inner_object_then_delete() {
        // vi( selects inside the parens; d deletes it
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["foo(bar)baz"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('a'), &mut t); // cursor on 'a' of "bar" (col 5)
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('i'), &mut t);
        e.handle_key(&key('('), &mut t); // select "bar"
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &["foo()baz"]);
    }

    #[test]
    fn visual_around_quote_then_yank() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["say \"hi\" now"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('h'), &mut t); // inside quotes
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('a'), &mut t);
        e.handle_key(&key('"'), &mut t); // select "\"hi\""
        e.handle_key(&key('y'), &mut t);
        let reg = e.registers.read().unwrap();
        assert_eq!(reg.text, "\"hi\"");
    }

    #[test]
    fn visual_find_extends_selection() {
        // vf, then d deletes through the ','
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello, world"]);
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key(','), &mut t); // cursor on ',' — selection covers "hello,"
        e.handle_key(&key('d'), &mut t);
        assert_eq!(t.lines(), &[" world"]);
    }

    #[test]
    fn visual_gg_extends_to_file_start() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('j'), &mut t);
        e.handle_key(&key('j'), &mut t); // row 2
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('g'), &mut t); // extend to (0,0)
        e.handle_key(&key('d'), &mut t); // delete from 't' of "three" back to start
        assert_eq!(t.lines(), &["hree"]);
    }

    #[test]
    fn visual_o_swaps_selection_ends() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abcde"]);
        e.handle_key(&key('l'), &mut t);
        e.handle_key(&key('l'), &mut t); // col 2 ('c')
        e.handle_key(&key('v'), &mut t);
        e.handle_key(&key('l'), &mut t); // select c..d, cursor at 'd' (col 3)
        e.handle_key(&key('o'), &mut t); // cursor swaps to 'c' (col 2)
        assert_eq!(super::super::cursor_tuple(&t), (0, 2));
        e.handle_key(&key('h'), &mut t); // extend left from the anchor end
        e.handle_key(&key('d'), &mut t); // delete b..d inclusive
        assert_eq!(t.lines(), &["ae"]);
    }

    // ── Command spine: dot-repeat through the one apply() door ───────────────

    #[test]
    fn dot_repeats_cc_with_typed_text() {
        // previously a silent no-op (replay's `_other` arm)
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('c'), &mut t); // cc on "one"
        t.insert_str("X");
        e.handle_key(&esc(), &mut t); // line 0 = "X"
        e.handle_key(&key('j'), &mut t); // onto "two"
        e.handle_key(&key('.'), &mut t); // repeat cc+X
        assert_eq!(t.lines(), &["X", "X"]);
    }

    #[test]
    fn dot_repeats_substitute_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab cd"]);
        e.handle_key(&key('s'), &mut t); // delete 'a', Insert
        t.insert_str("Z");
        e.handle_key(&esc(), &mut t); // "Zb cd"
        e.handle_key(&key('w'), &mut t); // onto 'c'
        e.handle_key(&key('.'), &mut t); // repeat s+Z on 'c'
        assert_eq!(t.lines(), &["Zb Zd"]);
    }

    #[test]
    fn dot_repeats_plain_insert() {
        // vim: `ihello<Esc>` then `.` inserts "hello" again
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["world"]);
        e.handle_key(&key('i'), &mut t);
        t.insert_str("ab");
        e.handle_key(&esc(), &mut t); // "abworld", cursor on 'b'
        e.handle_key(&key('.'), &mut t); // insert "ab" again before 'b'
        assert_eq!(t.lines(), &["aabbworld"]);
    }

    #[test]
    fn dot_repeats_indent() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["x"]);
        e.handle_key(&key('>'), &mut t);
        e.handle_key(&key('>'), &mut t); // indent
        e.handle_key(&key('.'), &mut t); // repeat
        assert_eq!(t.lines(), &["        x"]);
    }

    #[test]
    fn dot_does_not_repeat_yank() {
        // vim: `.` repeats the last CHANGE; a yank after it must not displace it
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('x'), &mut t); // delete 'a' (the change)
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('l'), &mut t); // yank 'b' — not a change
        e.handle_key(&key('.'), &mut t); // must repeat x, not the yank
        assert_eq!(t.lines(), &["c"]);
    }

    // ── Range model: motion SpanKind classification + count composition ─────

    #[test]
    fn counts_before_and_after_operator_multiply() {
        // vim: 2d3w = 6 words, not count "23"
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a b c d e f g"]);
        e.handle_key(&key('2'), &mut t);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('3'), &mut t);
        e.handle_key(&key('w'), &mut t);
        assert_eq!(t.lines(), &["g"]); // six words deleted
    }

    #[test]
    fn dj_deletes_two_whole_lines_linewise() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('l'), &mut t); // col 1 — must not matter (linewise)
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('j'), &mut t);
        assert_eq!(t.lines(), &["three"]);
        let reg = e.registers.read().unwrap();
        assert_eq!(reg.kind, RegisterKind::Linewise);
        assert_eq!(reg.text, "one\ntwo\n");
    }

    #[test]
    fn dk_deletes_two_whole_lines_upward() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('j'), &mut t); // row 1
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('k'), &mut t);
        assert_eq!(t.lines(), &["three"]);
    }

    #[test]
    #[allow(non_snake_case)]
    fn dG_deletes_to_file_end_linewise() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('j'), &mut t); // row 1
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('G'), &mut t);
        assert_eq!(t.lines(), &["one"]);
    }

    #[test]
    fn d_gg_deletes_to_file_start_linewise() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('j'), &mut t); // row 1
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('g'), &mut t);
        e.handle_key(&key('g'), &mut t);
        assert_eq!(t.lines(), &["three"]);
    }

    #[test]
    fn dt_deletes_up_to_but_not_including_target() {
        // vim t is inclusive of the char BEFORE the target: dtx on "abx" → "x"
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abx"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('t'), &mut t);
        e.handle_key(&key('x'), &mut t);
        assert_eq!(t.lines(), &["x"]);
    }

    #[test]
    fn failed_find_with_operator_is_noop() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["hello"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('z'), &mut t); // no 'z' on the line
        assert_eq!(t.lines(), &["hello"]); // nothing deleted
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('z'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Normal); // failed cf must not enter Insert
    }

    #[test]
    fn d_semicolon_repeats_find_as_operator_range() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["a.b.c"]);
        e.handle_key(&key('f'), &mut t);
        e.handle_key(&key('.'), &mut t); // cursor on first '.' (col 1)
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key(';'), &mut t); // delete through next '.' (inclusive)
        assert_eq!(t.lines(), &["ac"]);
    }

    #[test]
    fn cj_changes_two_lines_and_enters_insert() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two", "three"]);
        e.handle_key(&key('c'), &mut t);
        e.handle_key(&key('j'), &mut t);
        assert_eq!(*e.mode(), EditorMode::Insert);
        assert_eq!(t.lines(), &["", "three"]); // both lines gone, fresh empty line
    }

    // ── Register file: engine-owned unnamed register ────────────────────────

    #[test]
    fn x_then_p_swaps_chars() {
        // the classic vim `xp` idiom: x fills the register with the deleted char
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab"]);
        e.handle_key(&key('x'), &mut t); // delete 'a' → register "a"; line "b"
        e.handle_key(&key('p'), &mut t); // paste "a" after 'b'
        assert_eq!(t.lines(), &["ba"]);
    }

    #[test]
    fn x_at_line_end_does_not_join_next_line() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab", "cd"]);
        e.handle_key(&key('l'), &mut t); // onto 'b' (last char)
        e.handle_key(&key('3'), &mut t);
        e.handle_key(&key('x'), &mut t); // vim: deletes only 'b', never the newline
        assert_eq!(t.lines(), &["a", "cd"]);
    }

    #[test]
    fn s_fills_register_with_deleted_char() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["abc"]);
        e.handle_key(&key('s'), &mut t); // delete 'a', enter Insert
        assert_eq!(*e.mode(), EditorMode::Insert);
        let reg = e.registers.read().expect("s must fill the register");
        assert_eq!(reg.text, "a");
        assert_eq!(reg.kind, RegisterKind::Charwise);
    }

    #[test]
    #[allow(non_snake_case)]
    fn S_fills_register_linewise_no_kind_desync() {
        // regression: S used to cut() (charwise content) while the engine kept
        // a stale Linewise kind from a prior yy — kind and content desynced.
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one", "two"]);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('y'), &mut t); // register = "one\n" linewise
        e.handle_key(&key('j'), &mut t);
        e.handle_key(&key('S'), &mut t); // substitute line "two"
        let reg = e.registers.read().expect("S must fill the register");
        assert_eq!(reg.text, "two\n");
        assert_eq!(reg.kind, RegisterKind::Linewise);
    }

    #[test]
    fn dw_fills_register_charwise() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["one two"]);
        e.handle_key(&key('d'), &mut t);
        e.handle_key(&key('w'), &mut t); // delete "one "
        let reg = e.registers.read().expect("dw must fill the register");
        assert_eq!(reg.text, "one ");
        assert_eq!(reg.kind, RegisterKind::Charwise);
        // and p pastes it back charwise
        e.handle_key(&key('p'), &mut t);
        assert_eq!(t.lines(), &["tone wo"]); // "one " pasted after 't'
    }

    #[test]
    fn empty_delete_keeps_previous_register() {
        let mut e = VimEngine::default();
        let mut t = TextArea::from(["ab", ""]);
        e.handle_key(&key('y'), &mut t);
        e.handle_key(&key('l'), &mut t); // yank "a" charwise
        e.handle_key(&key('j'), &mut t); // empty line
        e.handle_key(&key('x'), &mut t); // no-op delete (empty line)
        let reg = e
            .registers
            .read()
            .expect("register must survive a no-op delete");
        assert_eq!(reg.text, "a");
    }

    #[test]
    fn esc_in_normal_clears_stray_selection() {
        let mut e = VimEngine::default(); // Normal mode
        let mut t = TextArea::from(["hello world"]);
        // simulate a live selection while in Normal mode (as auto-surround/mouse-sync can leave)
        t.start_selection();
        t.move_cursor(ratatui_textarea::CursorMove::Forward);
        t.move_cursor(ratatui_textarea::CursorMove::Forward);
        assert!(t.selection_range().is_some());
        let out = e.handle_key(&esc(), &mut t);
        assert!(
            t.selection_range().is_none(),
            "Esc in Normal must cancel a stray selection"
        );
        assert_eq!(out, VimKeyOutcome::CursorOnly);
        assert_eq!(*e.mode(), EditorMode::Normal);
    }
}