hjkl_engine/

editor.rs

//! Editor — the public sqeel-vim type, layered over `hjkl_buffer::Buffer`.
//!
//! This file owns the public Editor API — construction, content access,
//! mouse and goto helpers, the (buffer-level) undo stack, and insert-mode
//! session bookkeeping. All vim-specific keyboard handling lives in
//! [`vim`] and communicates with Editor through a small internal API
//! exposed via `pub(super)` fields and helper methods.

use crate::input::Input;
#[cfg(feature = "crossterm")]
use crate::input::Key;
use crate::vim::{self, VimState};
use crate::{KeybindingMode, VimMode};
#[cfg(feature = "crossterm")]
use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
#[cfg(feature = "ratatui")]
use ratatui::layout::Rect;
use std::sync::atomic::{AtomicU16, Ordering};

/// Convert a SPEC [`crate::types::Style`] to a [`ratatui::style::Style`].
///
/// Lossless within the styles each library represents. Lives behind the
/// `ratatui` feature so wasm / no_std consumers that opt out don't pay
/// for the dep. Use the engine-native [`crate::types::Style`] +
/// [`Editor::intern_engine_style`] surface from feature-disabled hosts.
#[cfg(feature = "ratatui")]
pub(crate) fn engine_style_to_ratatui(s: crate::types::Style) -> ratatui::style::Style {
    use crate::types::Attrs;
    use ratatui::style::{Color as RColor, Modifier as RMod, Style as RStyle};
    let mut out = RStyle::default();
    if let Some(c) = s.fg {
        out = out.fg(RColor::Rgb(c.0, c.1, c.2));
    }
    if let Some(c) = s.bg {
        out = out.bg(RColor::Rgb(c.0, c.1, c.2));
    }
    let mut m = RMod::empty();
    if s.attrs.contains(Attrs::BOLD) {
        m |= RMod::BOLD;
    }
    if s.attrs.contains(Attrs::ITALIC) {
        m |= RMod::ITALIC;
    }
    if s.attrs.contains(Attrs::UNDERLINE) {
        m |= RMod::UNDERLINED;
    }
    if s.attrs.contains(Attrs::REVERSE) {
        m |= RMod::REVERSED;
    }
    if s.attrs.contains(Attrs::DIM) {
        m |= RMod::DIM;
    }
    if s.attrs.contains(Attrs::STRIKE) {
        m |= RMod::CROSSED_OUT;
    }
    out.add_modifier(m)
}

/// Inverse of [`engine_style_to_ratatui`]. Lossy for ratatui colors
/// the engine doesn't model (Indexed, named ANSI) — flattens to
/// nearest RGB. Behind the `ratatui` feature.
#[cfg(feature = "ratatui")]
pub(crate) fn ratatui_style_to_engine(s: ratatui::style::Style) -> crate::types::Style {
    use crate::types::{Attrs, Color, Style};
    use ratatui::style::{Color as RColor, Modifier as RMod};
    fn c(rc: RColor) -> Color {
        match rc {
            RColor::Rgb(r, g, b) => Color(r, g, b),
            RColor::Black => Color(0, 0, 0),
            RColor::Red => Color(205, 49, 49),
            RColor::Green => Color(13, 188, 121),
            RColor::Yellow => Color(229, 229, 16),
            RColor::Blue => Color(36, 114, 200),
            RColor::Magenta => Color(188, 63, 188),
            RColor::Cyan => Color(17, 168, 205),
            RColor::Gray => Color(229, 229, 229),
            RColor::DarkGray => Color(102, 102, 102),
            RColor::LightRed => Color(241, 76, 76),
            RColor::LightGreen => Color(35, 209, 139),
            RColor::LightYellow => Color(245, 245, 67),
            RColor::LightBlue => Color(59, 142, 234),
            RColor::LightMagenta => Color(214, 112, 214),
            RColor::LightCyan => Color(41, 184, 219),
            RColor::White => Color(255, 255, 255),
            _ => Color(0, 0, 0),
        }
    }
    let mut attrs = Attrs::empty();
    if s.add_modifier.contains(RMod::BOLD) {
        attrs |= Attrs::BOLD;
    }
    if s.add_modifier.contains(RMod::ITALIC) {
        attrs |= Attrs::ITALIC;
    }
    if s.add_modifier.contains(RMod::UNDERLINED) {
        attrs |= Attrs::UNDERLINE;
    }
    if s.add_modifier.contains(RMod::REVERSED) {
        attrs |= Attrs::REVERSE;
    }
    if s.add_modifier.contains(RMod::DIM) {
        attrs |= Attrs::DIM;
    }
    if s.add_modifier.contains(RMod::CROSSED_OUT) {
        attrs |= Attrs::STRIKE;
    }
    Style {
        fg: s.fg.map(c),
        bg: s.bg.map(c),
        attrs,
    }
}

/// Map a [`hjkl_buffer::Edit`] to one or more SPEC
/// [`crate::types::Edit`] (`EditOp`) records.
///
/// Most buffer edits map to a single EditOp. Block ops
/// ([`hjkl_buffer::Edit::InsertBlock`] /
/// [`hjkl_buffer::Edit::DeleteBlockChunks`]) emit one EditOp per row
/// touched — they edit non-contiguous cells and a single
/// `range..range` can't represent the rectangle.
///
/// Returns an empty vec when the edit isn't representable (no buffer
/// variant currently fails this check).
fn edit_to_editops(edit: &hjkl_buffer::Edit) -> Vec<crate::types::Edit> {
    use crate::types::{Edit as Op, Pos};
    use hjkl_buffer::Edit as B;
    let to_pos = |p: hjkl_buffer::Position| Pos {
        line: p.row as u32,
        col: p.col as u32,
    };
    match edit {
        B::InsertChar { at, ch } => vec![Op {
            range: to_pos(*at)..to_pos(*at),
            replacement: ch.to_string(),
        }],
        B::InsertStr { at, text } => vec![Op {
            range: to_pos(*at)..to_pos(*at),
            replacement: text.clone(),
        }],
        B::DeleteRange { start, end, .. } => vec![Op {
            range: to_pos(*start)..to_pos(*end),
            replacement: String::new(),
        }],
        B::Replace { start, end, with } => vec![Op {
            range: to_pos(*start)..to_pos(*end),
            replacement: with.clone(),
        }],
        B::JoinLines {
            row,
            count,
            with_space,
        } => {
            // Joining `count` rows after `row` collapses
            // [(row+1, 0) .. (row+count, EOL)] into the joined
            // sentinel. The replacement is either an empty string
            // (gJ) or " " between segments (J).
            let start = Pos {
                line: *row as u32 + 1,
                col: 0,
            };
            let end = Pos {
                line: (*row + *count) as u32,
                col: u32::MAX, // covers to EOL of the last source row
            };
            vec![Op {
                range: start..end,
                replacement: if *with_space {
                    " ".into()
                } else {
                    String::new()
                },
            }]
        }
        B::SplitLines {
            row,
            cols,
            inserted_space: _,
        } => {
            // SplitLines reverses a JoinLines: insert a `\n`
            // (and optional dropped space) at each col on `row`.
            cols.iter()
                .map(|c| {
                    let p = Pos {
                        line: *row as u32,
                        col: *c as u32,
                    };
                    Op {
                        range: p..p,
                        replacement: "\n".into(),
                    }
                })
                .collect()
        }
        B::InsertBlock { at, chunks } => {
            // One EditOp per row in the block — non-contiguous edits.
            chunks
                .iter()
                .enumerate()
                .map(|(i, chunk)| {
                    let p = Pos {
                        line: at.row as u32 + i as u32,
                        col: at.col as u32,
                    };
                    Op {
                        range: p..p,
                        replacement: chunk.clone(),
                    }
                })
                .collect()
        }
        B::DeleteBlockChunks { at, widths } => {
            // One EditOp per row, deleting `widths[i]` chars at
            // `(at.row + i, at.col)`.
            widths
                .iter()
                .enumerate()
                .map(|(i, w)| {
                    let start = Pos {
                        line: at.row as u32 + i as u32,
                        col: at.col as u32,
                    };
                    let end = Pos {
                        line: at.row as u32 + i as u32,
                        col: at.col as u32 + *w as u32,
                    };
                    Op {
                        range: start..end,
                        replacement: String::new(),
                    }
                })
                .collect()
        }
    }
}

/// Sum of bytes from the start of the buffer to the start of `row`.
/// Walks lines + their separating `\n` bytes — matches the canonical
/// `lines().join("\n")` byte rendering used by syntax tooling.
#[inline]
fn buffer_byte_of_row(buf: &hjkl_buffer::Buffer, row: usize) -> usize {
    let n = buf.row_count();
    let row = row.min(n);
    let mut acc = 0usize;
    for r in 0..row {
        acc += buf.line(r).map(str::len).unwrap_or(0);
        if r + 1 < n {
            acc += 1; // separator '\n'
        }
    }
    acc
}

/// Convert an `hjkl_buffer::Position` (char-indexed col) into byte
/// coordinates `(byte_within_buffer, (row, col_byte))` against the
/// **pre-edit** buffer.
fn position_to_byte_coords(
    buf: &hjkl_buffer::Buffer,
    pos: hjkl_buffer::Position,
) -> (usize, (u32, u32)) {
    let row = pos.row.min(buf.row_count().saturating_sub(1));
    let line = buf.line(row).unwrap_or("");
    let col_byte = pos.byte_offset(line);
    let byte = buffer_byte_of_row(buf, row) + col_byte;
    (byte, (row as u32, col_byte as u32))
}

/// Compute the byte position after inserting `text` starting at
/// `start_byte` / `start_pos`. Returns `(end_byte, end_position)`.
fn advance_by_text(text: &str, start_byte: usize, start_pos: (u32, u32)) -> (usize, (u32, u32)) {
    let new_end_byte = start_byte + text.len();
    let newlines = text.bytes().filter(|&b| b == b'\n').count();
    let end_pos = if newlines == 0 {
        (start_pos.0, start_pos.1 + text.len() as u32)
    } else {
        // Bytes after the last newline determine the trailing column.
        let last_nl = text.rfind('\n').unwrap();
        let tail_bytes = (text.len() - last_nl - 1) as u32;
        (start_pos.0 + newlines as u32, tail_bytes)
    };
    (new_end_byte, end_pos)
}

/// Translate a single `hjkl_buffer::Edit` into one or more
/// [`crate::types::ContentEdit`] records using the **pre-edit** buffer
/// state for byte/position lookups. Block ops fan out to one entry per
/// touched row (matches `edit_to_editops`).
fn content_edits_from_buffer_edit(
    buf: &hjkl_buffer::Buffer,
    edit: &hjkl_buffer::Edit,
) -> Vec<crate::types::ContentEdit> {
    use hjkl_buffer::Edit as B;
    use hjkl_buffer::Position;

    let mut out: Vec<crate::types::ContentEdit> = Vec::new();

    match edit {
        B::InsertChar { at, ch } => {
            let (start_byte, start_pos) = position_to_byte_coords(buf, *at);
            let new_end_byte = start_byte + ch.len_utf8();
            let new_end_pos = (start_pos.0, start_pos.1 + ch.len_utf8() as u32);
            out.push(crate::types::ContentEdit {
                start_byte,
                old_end_byte: start_byte,
                new_end_byte,
                start_position: start_pos,
                old_end_position: start_pos,
                new_end_position: new_end_pos,
            });
        }
        B::InsertStr { at, text } => {
            let (start_byte, start_pos) = position_to_byte_coords(buf, *at);
            let (new_end_byte, new_end_pos) = advance_by_text(text, start_byte, start_pos);
            out.push(crate::types::ContentEdit {
                start_byte,
                old_end_byte: start_byte,
                new_end_byte,
                start_position: start_pos,
                old_end_position: start_pos,
                new_end_position: new_end_pos,
            });
        }
        B::DeleteRange { start, end, kind } => {
            let (start, end) = if start <= end {
                (*start, *end)
            } else {
                (*end, *start)
            };
            match kind {
                hjkl_buffer::MotionKind::Char => {
                    let (start_byte, start_pos) = position_to_byte_coords(buf, start);
                    let (old_end_byte, old_end_pos) = position_to_byte_coords(buf, end);
                    out.push(crate::types::ContentEdit {
                        start_byte,
                        old_end_byte,
                        new_end_byte: start_byte,
                        start_position: start_pos,
                        old_end_position: old_end_pos,
                        new_end_position: start_pos,
                    });
                }
                hjkl_buffer::MotionKind::Line => {
                    // Linewise delete drops rows [start.row..=end.row]. Map
                    // to a span from start of `start.row` through start of
                    // (end.row + 1). The buffer's own `do_delete_range`
                    // collapses to row `start.row` after dropping.
                    let lo = start.row;
                    let hi = end.row.min(buf.row_count().saturating_sub(1));
                    let start_byte = buffer_byte_of_row(buf, lo);
                    let next_row_byte = if hi + 1 < buf.row_count() {
                        buffer_byte_of_row(buf, hi + 1)
                    } else {
                        // No row after; clamp to end-of-buffer byte.
                        buffer_byte_of_row(buf, buf.row_count())
                            + buf
                                .line(buf.row_count().saturating_sub(1))
                                .map(str::len)
                                .unwrap_or(0)
                    };
                    out.push(crate::types::ContentEdit {
                        start_byte,
                        old_end_byte: next_row_byte,
                        new_end_byte: start_byte,
                        start_position: (lo as u32, 0),
                        old_end_position: ((hi + 1) as u32, 0),
                        new_end_position: (lo as u32, 0),
                    });
                }
                hjkl_buffer::MotionKind::Block => {
                    // Block delete removes a rectangle of chars per row.
                    // Fan out to one ContentEdit per row.
                    let (left_col, right_col) = (start.col.min(end.col), start.col.max(end.col));
                    for row in start.row..=end.row {
                        let row_start_pos = Position::new(row, left_col);
                        let row_end_pos = Position::new(row, right_col + 1);
                        let (sb, sp) = position_to_byte_coords(buf, row_start_pos);
                        let (eb, ep) = position_to_byte_coords(buf, row_end_pos);
                        if eb <= sb {
                            continue;
                        }
                        out.push(crate::types::ContentEdit {
                            start_byte: sb,
                            old_end_byte: eb,
                            new_end_byte: sb,
                            start_position: sp,
                            old_end_position: ep,
                            new_end_position: sp,
                        });
                    }
                }
            }
        }
        B::Replace { start, end, with } => {
            let (start, end) = if start <= end {
                (*start, *end)
            } else {
                (*end, *start)
            };
            let (start_byte, start_pos) = position_to_byte_coords(buf, start);
            let (old_end_byte, old_end_pos) = position_to_byte_coords(buf, end);
            let (new_end_byte, new_end_pos) = advance_by_text(with, start_byte, start_pos);
            out.push(crate::types::ContentEdit {
                start_byte,
                old_end_byte,
                new_end_byte,
                start_position: start_pos,
                old_end_position: old_end_pos,
                new_end_position: new_end_pos,
            });
        }
        B::JoinLines {
            row,
            count,
            with_space,
        } => {
            // Joining `count` rows after `row` collapses the bytes
            // between EOL of `row` and EOL of `row + count` into either
            // an empty string (gJ) or a single space per join (J — but
            // only when both sides are non-empty; we approximate with
            // a single space for simplicity).
            let row = (*row).min(buf.row_count().saturating_sub(1));
            let last_join_row = (row + count).min(buf.row_count().saturating_sub(1));
            let line = buf.line(row).unwrap_or("");
            let row_eol_byte = buffer_byte_of_row(buf, row) + line.len();
            let row_eol_col = line.len() as u32;
            let next_row_after = last_join_row + 1;
            let old_end_byte = if next_row_after < buf.row_count() {
                buffer_byte_of_row(buf, next_row_after).saturating_sub(1)
            } else {
                buffer_byte_of_row(buf, buf.row_count())
                    + buf
                        .line(buf.row_count().saturating_sub(1))
                        .map(str::len)
                        .unwrap_or(0)
            };
            let last_line = buf.line(last_join_row).unwrap_or("");
            let old_end_pos = (last_join_row as u32, last_line.len() as u32);
            let replacement_len = if *with_space { 1 } else { 0 };
            let new_end_byte = row_eol_byte + replacement_len;
            let new_end_pos = (row as u32, row_eol_col + replacement_len as u32);
            out.push(crate::types::ContentEdit {
                start_byte: row_eol_byte,
                old_end_byte,
                new_end_byte,
                start_position: (row as u32, row_eol_col),
                old_end_position: old_end_pos,
                new_end_position: new_end_pos,
            });
        }
        B::SplitLines {
            row,
            cols,
            inserted_space,
        } => {
            // Splits insert "\n" (or "\n " inverse) at each col on `row`.
            // The buffer applies all splits left-to-right via the
            // do_split_lines path; we emit one ContentEdit per col,
            // each treated as an insert at that col on `row`. Note: the
            // buffer state during emission is *pre-edit*, so all cols
            // index into the same pre-edit row.
            let row = (*row).min(buf.row_count().saturating_sub(1));
            let line = buf.line(row).unwrap_or("");
            let row_byte = buffer_byte_of_row(buf, row);
            let insert = if *inserted_space { "\n " } else { "\n" };
            for &c in cols {
                let pos = Position::new(row, c);
                let col_byte = pos.byte_offset(line);
                let start_byte = row_byte + col_byte;
                let start_pos = (row as u32, col_byte as u32);
                let (new_end_byte, new_end_pos) = advance_by_text(insert, start_byte, start_pos);
                out.push(crate::types::ContentEdit {
                    start_byte,
                    old_end_byte: start_byte,
                    new_end_byte,
                    start_position: start_pos,
                    old_end_position: start_pos,
                    new_end_position: new_end_pos,
                });
            }
        }
        B::InsertBlock { at, chunks } => {
            // One ContentEdit per chunk; each lands at `(at.row + i,
            // at.col)` in the pre-edit buffer.
            for (i, chunk) in chunks.iter().enumerate() {
                let pos = Position::new(at.row + i, at.col);
                let (start_byte, start_pos) = position_to_byte_coords(buf, pos);
                let (new_end_byte, new_end_pos) = advance_by_text(chunk, start_byte, start_pos);
                out.push(crate::types::ContentEdit {
                    start_byte,
                    old_end_byte: start_byte,
                    new_end_byte,
                    start_position: start_pos,
                    old_end_position: start_pos,
                    new_end_position: new_end_pos,
                });
            }
        }
        B::DeleteBlockChunks { at, widths } => {
            for (i, w) in widths.iter().enumerate() {
                let row = at.row + i;
                let start_pos = Position::new(row, at.col);
                let end_pos = Position::new(row, at.col + *w);
                let (sb, sp) = position_to_byte_coords(buf, start_pos);
                let (eb, ep) = position_to_byte_coords(buf, end_pos);
                if eb <= sb {
                    continue;
                }
                out.push(crate::types::ContentEdit {
                    start_byte: sb,
                    old_end_byte: eb,
                    new_end_byte: sb,
                    start_position: sp,
                    old_end_position: ep,
                    new_end_position: sp,
                });
            }
        }
    }

    out
}

/// Where the cursor should land in the viewport after a `z`-family
/// scroll (`zz` / `zt` / `zb`).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(super) enum CursorScrollTarget {
    Center,
    Top,
    Bottom,
}

// ── Trait-surface cast helpers ────────────────────────────────────
//
// 0.0.42 (Patch C-δ.7): the helpers introduced in 0.0.41 were
// promoted to [`crate::buf_helpers`] so `vim.rs` free fns can route
// their reaches through the same primitives. Re-import via
// `use` so the editor body keeps its terse call shape.

use crate::buf_helpers::{
    apply_buffer_edit, buf_cursor_pos, buf_cursor_rc, buf_cursor_row, buf_line, buf_line_chars,
    buf_lines_to_vec, buf_row_count, buf_set_cursor_rc,
};

pub struct Editor<
    B: crate::types::Buffer = hjkl_buffer::Buffer,
    H: crate::types::Host = crate::types::DefaultHost,
> {
    pub keybinding_mode: KeybindingMode,
    /// Set when the user yanks/cuts; caller drains this to write to OS clipboard.
    pub last_yank: Option<String>,
    /// All vim-specific state (mode, pending operator, count, dot-repeat, ...).
    /// Internal — exposed via Editor accessor methods
    /// ([`Editor::buffer_mark`], [`Editor::last_jump_back`],
    /// [`Editor::last_edit_pos`], [`Editor::take_lsp_intent`], …).
    pub(crate) vim: VimState,
    /// Undo history: each entry is (lines, cursor) before the edit.
    /// Internal — managed by [`Editor::push_undo`] / [`Editor::restore`]
    /// / [`Editor::pop_last_undo`].
    pub(crate) undo_stack: Vec<(Vec<String>, (usize, usize))>,
    /// Redo history: entries pushed when undoing.
    pub(super) redo_stack: Vec<(Vec<String>, (usize, usize))>,
    /// Set whenever the buffer content changes; cleared by `take_dirty`.
    pub(super) content_dirty: bool,
    /// Cached snapshot of `lines().join("\n") + "\n"` wrapped in an Arc
    /// so repeated `content_arc()` calls within the same un-mutated
    /// window are free (ref-count bump instead of a full-buffer join).
    /// Invalidated by every [`mark_content_dirty`] call.
    pub(super) cached_content: Option<std::sync::Arc<String>>,
    /// Last rendered viewport height (text rows only, no chrome). Written
    /// by the draw path via [`set_viewport_height`] so the scroll helpers
    /// can clamp the cursor to stay visible without plumbing the height
    /// through every call.
    pub(super) viewport_height: AtomicU16,
    /// Pending LSP intent set by a normal-mode chord (e.g. `gd` for
    /// goto-definition). The host app drains this each step and fires
    /// the matching request against its own LSP client.
    pub(super) pending_lsp: Option<LspIntent>,
    /// Pending [`crate::types::FoldOp`]s raised by `z…` keystrokes,
    /// the `:fold*` Ex commands, or the edit pipeline's
    /// "edits-inside-a-fold open it" invalidation. Drained by hosts
    /// via [`Editor::take_fold_ops`]; the engine also applies each op
    /// locally through [`crate::buffer_impl::BufferFoldProviderMut`]
    /// so the in-tree buffer fold storage stays in sync without host
    /// cooperation. Introduced in 0.0.38 (Patch C-δ.4).
    pub(super) pending_fold_ops: Vec<crate::types::FoldOp>,
    /// Buffer storage.
    ///
    /// 0.1.0 (Patch C-δ): generic over `B: Buffer` per SPEC §"Editor
    /// surface". Default `B = hjkl_buffer::Buffer`. The vim FSM body
    /// and `Editor::mutate_edit` are concrete on `hjkl_buffer::Buffer`
    /// for 0.1.0 — see `crate::buf_helpers::apply_buffer_edit`.
    pub(super) buffer: B,
    /// Style intern table for the migration buffer's opaque
    /// `Span::style` ids. Phase 7d-ii-a wiring — `apply_window_spans`
    /// produces `(start, end, Style)` tuples for the textarea; we
    /// translate those to `hjkl_buffer::Span` by interning the
    /// `Style` here and storing the table index. The render path's
    /// `StyleResolver` looks the style back up by id.
    ///
    /// Behind the `ratatui` feature; non-ratatui hosts use the
    /// engine-native [`crate::types::Style`] surface via
    /// [`Editor::intern_engine_style`] (which lives on a parallel
    /// engine-side table when ratatui is off).
    #[cfg(feature = "ratatui")]
    pub(super) style_table: Vec<ratatui::style::Style>,
    /// Engine-native style intern table. Used directly by
    /// [`Editor::intern_engine_style`] when the `ratatui` feature is
    /// off; when it's on, the table is derived from `style_table` via
    /// [`ratatui_style_to_engine`] / [`engine_style_to_ratatui`].
    #[cfg(not(feature = "ratatui"))]
    pub(super) engine_style_table: Vec<crate::types::Style>,
    /// Vim-style register bank — `"`, `"0`–`"9`, `"a`–`"z`. Sources
    /// every `p` / `P` via the active selector (default unnamed).
    /// Internal — read via [`Editor::registers`]; mutated by yank /
    /// delete / paste FSM paths and by [`Editor::seed_yank`].
    pub(crate) registers: crate::registers::Registers,
    /// Per-row syntax styling, kept here so the host can do
    /// incremental window updates (see `apply_window_spans` in
    /// the host). Same `(start_byte, end_byte, Style)` tuple shape
    /// the textarea used to host. The Buffer-side opaque-id spans are
    /// derived from this on every install. Behind the `ratatui`
    /// feature.
    #[cfg(feature = "ratatui")]
    pub styled_spans: Vec<Vec<(usize, usize, ratatui::style::Style)>>,
    /// Per-editor settings tweakable via `:set`. Exposed by reference
    /// so handlers (indent, search) read the live value rather than a
    /// snapshot taken at startup. Read via [`Editor::settings`];
    /// mutate via [`Editor::settings_mut`].
    pub(crate) settings: Settings,
    /// Unified named-marks map. Lowercase letters (`'a`–`'z`) are
    /// per-Editor / "buffer-scope-equivalent" — set by `m{a-z}`, read
    /// by `'{a-z}` / `` `{a-z} ``. Uppercase letters (`'A`–`'Z`) are
    /// "file marks" that survive [`Editor::set_content`] calls so
    /// they persist across tab swaps within the same Editor.
    ///
    /// 0.0.36: consolidated from three former storages:
    /// - `hjkl_buffer::Buffer::marks` (deleted; was unused dead code).
    /// - `vim::VimState::marks` (lowercase) (deleted).
    /// - `Editor::file_marks` (uppercase) (replaced by this map).
    ///
    /// `BTreeMap` so iteration is deterministic for snapshot tests
    /// and the `:marks` ex command. Mark-shift on edits is handled
    /// by [`Editor::shift_marks_after_edit`].
    pub(crate) marks: std::collections::BTreeMap<char, (usize, usize)>,
    /// Block ranges (`(start_row, end_row)` inclusive) the host has
    /// extracted from a syntax tree. `:foldsyntax` reads these to
    /// populate folds. The host refreshes them on every re-parse via
    /// [`Editor::set_syntax_fold_ranges`]; ex commands read them via
    /// [`Editor::syntax_fold_ranges`].
    pub(crate) syntax_fold_ranges: Vec<(usize, usize)>,
    /// Pending edit log drained by [`Editor::take_changes`]. Each entry
    /// is a SPEC [`crate::types::Edit`] mapped from the underlying
    /// `hjkl_buffer::Edit` operation. Compound ops (JoinLines,
    /// SplitLines, InsertBlock, DeleteBlockChunks) emit a single
    /// best-effort EditOp covering the touched range; hosts wanting
    /// per-cell deltas should diff their own snapshot of `lines()`.
    /// Sealed at 0.1.0 trait extraction.
    /// Drained by [`Editor::take_changes`].
    pub(crate) change_log: Vec<crate::types::Edit>,
    /// Vim's "sticky column" (curswant). `None` before the first
    /// motion — the next vertical motion bootstraps from the live
    /// cursor column. Horizontal motions refresh this to the new
    /// column; vertical motions read it back so bouncing through a
    /// shorter row doesn't drag the cursor to col 0. Hoisted out of
    /// `hjkl_buffer::Buffer` (and `VimState`) in 0.0.28 — Editor is
    /// the single owner now. Buffer motion methods that need it
    /// take a `&mut Option<usize>` parameter.
    pub(crate) sticky_col: Option<usize>,
    /// Host adapter for clipboard, cursor-shape, time, viewport, and
    /// search-prompt / cancellation side-channels.
    ///
    /// 0.1.0 (Patch C-δ): generic over `H: Host` per SPEC §"Editor
    /// surface". Default `H = DefaultHost`. The pre-0.1.0 `EngineHost`
    /// dyn-shim is gone — every method now dispatches through `H`'s
    /// `Host` trait surface directly.
    pub(crate) host: H,
    /// Last public mode the cursor-shape emitter saw. Drives
    /// [`Editor::emit_cursor_shape_if_changed`] so `Host::emit_cursor_shape`
    /// fires exactly once per mode transition without sprinkling the
    /// call across every `vim.mode = ...` site.
    pub(crate) last_emitted_mode: crate::VimMode,
    /// Search FSM state (pattern + per-row match cache + wrapscan).
    /// 0.0.35: relocated out of `hjkl_buffer::Buffer` per
    /// `DESIGN_33_METHOD_CLASSIFICATION.md` step 1.
    /// 0.0.37: the buffer-side bridge (`Buffer::search_pattern`) is
    /// gone; `BufferView` now takes the active regex as a `&Regex`
    /// parameter, sourced from `Editor::search_state().pattern`.
    pub(crate) search_state: crate::search::SearchState,
    /// Per-row syntax span overlay. Source of truth for the host's
    /// renderer ([`hjkl_buffer::BufferView::spans`]). Populated by
    /// [`Editor::install_syntax_spans`] /
    /// [`Editor::install_ratatui_syntax_spans`] (and, in due course,
    /// by `Host::syntax_highlights` once the engine drives that path
    /// directly).
    ///
    /// 0.0.37: lifted out of `hjkl_buffer::Buffer` per step 3 of
    /// `DESIGN_33_METHOD_CLASSIFICATION.md`. The buffer-side cache +
    /// `Buffer::set_spans` / `Buffer::spans` accessors are gone.
    pub(crate) buffer_spans: Vec<Vec<hjkl_buffer::Span>>,
    /// Pending `ContentEdit` records emitted by `mutate_edit`. Drained by
    /// hosts via [`Editor::take_content_edits`] for fan-in to a syntax
    /// tree (or any other content-change observer that needs byte-level
    /// position deltas). Edges are byte-indexed and `(row, col_byte)`.
    pub(crate) pending_content_edits: Vec<crate::types::ContentEdit>,
    /// Pending "reset" flag set when the entire buffer is replaced
    /// (e.g. `set_content` / `restore`). Supersedes any queued
    /// `pending_content_edits` on the same frame: hosts call
    /// [`Editor::take_content_reset`] before draining edits.
    pub(crate) pending_content_reset: bool,
    /// Row range touched by the most recent `auto_indent_rows` call.
    /// `(top_row, bot_row)` inclusive. Set by the engine after every
    /// auto-indent operation; drained (and cleared) by the host via
    /// [`Editor::take_last_indent_range`] so it can display a brief
    /// visual flash over the reindented rows.
    pub(crate) last_indent_range: Option<(usize, usize)>,
}

/// Vim-style options surfaced by `:set`. New fields land here as
/// individual ex commands gain `:set` plumbing.
#[derive(Debug, Clone)]
pub struct Settings {
    /// Spaces per shift step for `>>` / `<<` / `Ctrl-T` / `Ctrl-D`.
    pub shiftwidth: usize,
    /// Visual width of a `\t` character. Stored for future render
    /// hookup; not yet consumed by the buffer renderer.
    pub tabstop: usize,
    /// When true, `/` / `?` patterns and `:s/.../.../` ignore case
    /// without an explicit `i` flag.
    pub ignore_case: bool,
    /// When true *and* `ignore_case` is true, an uppercase letter in
    /// the pattern flips that search back to case-sensitive. Matches
    /// vim's `:set smartcase`. Default `false`.
    pub smartcase: bool,
    /// Wrap searches past buffer ends. Matches vim's `:set wrapscan`.
    /// Default `true`.
    pub wrapscan: bool,
    /// Wrap column for `gq{motion}` text reflow. Vim's default is 79.
    pub textwidth: usize,
    /// When `true`, the Tab key in insert mode inserts `tabstop` spaces
    /// instead of a literal `\t`. Matches vim's `:set expandtab`.
    /// Default `false`.
    pub expandtab: bool,
    /// Soft tab stop in spaces. When `> 0`, Tab inserts spaces to the
    /// next softtabstop boundary (when `expandtab`), and Backspace at the
    /// end of a softtabstop-aligned space run deletes the entire run as
    /// if it were one tab. `0` disables. Matches vim's `:set softtabstop`.
    pub softtabstop: usize,
    /// Soft-wrap mode the renderer + scroll math + `gj` / `gk` use.
    /// Default is [`hjkl_buffer::Wrap::None`] — long lines extend
    /// past the right edge and `top_col` clips the left side.
    /// `:set wrap` flips to char-break wrap; `:set linebreak` flips
    /// to word-break wrap; `:set nowrap` resets.
    pub wrap: hjkl_buffer::Wrap,
    /// When true, the engine drops every edit before it touches the
    /// buffer — undo, dirty flag, and change log all stay clean.
    /// Matches vim's `:set readonly` / `:set ro`. Default `false`.
    pub readonly: bool,
    /// When `true`, pressing Enter in insert mode copies the leading
    /// whitespace of the current line onto the new line. Matches vim's
    /// `:set autoindent`. Default `true` (vim parity).
    pub autoindent: bool,
    /// When `true`, bumps indent by one `shiftwidth` after a line ending
    /// in `{` / `(` / `[`, and strips one indent unit when the user types
    /// `}` / `)` / `]` on a whitespace-only line. See `compute_enter_indent`
    /// in `vim.rs` for the tree-sitter plug-in seam. Default `true`.
    pub smartindent: bool,
    /// Cap on undo-stack length. Older entries are pruned past this
    /// bound. `0` means unlimited. Matches vim's `:set undolevels`.
    /// Default `1000`.
    pub undo_levels: u32,
    /// When `true`, cursor motions inside insert mode break the
    /// current undo group (so a single `u` only reverses the run of
    /// keystrokes that preceded the motion). Default `true`.
    /// Currently a no-op — engine doesn't yet break the undo group
    /// on insert-mode motions; field is wired through `:set
    /// undobreak` for forward compatibility.
    pub undo_break_on_motion: bool,
    /// Vim-flavoured "what counts as a word" character class.
    /// Comma-separated tokens: `@` = `is_alphabetic()`, `_` = literal
    /// `_`, `48-57` = decimal char range, bare integer = single char
    /// code, single ASCII punctuation = literal. Default
    /// `"@,48-57,_,192-255"` matches vim.
    pub iskeyword: String,
    /// Multi-key sequence timeout (e.g. `gg`, `dd`). When the user
    /// pauses longer than this between keys, any pending prefix is
    /// abandoned and the next key starts a fresh sequence. Matches
    /// vim's `:set timeoutlen` / `:set tm` (millis). Default 1000ms.
    pub timeout_len: core::time::Duration,
    /// When true, render absolute line numbers in the gutter. Matches
    /// vim's `:set number` / `:set nu`. Default `true`.
    pub number: bool,
    /// When true, render line numbers as offsets from the cursor row.
    /// Combined with `number`, the cursor row shows its absolute number
    /// while other rows show the relative offset (vim's `nu+rnu` hybrid).
    /// Matches vim's `:set relativenumber` / `:set rnu`. Default `false`.
    pub relativenumber: bool,
    /// Minimum gutter width in cells for the line-number column.
    /// Width grows past this to fit the largest displayed number.
    /// Matches vim's `:set numberwidth` / `:set nuw`. Default `4`.
    /// Range 1..=20.
    pub numberwidth: usize,
    /// Highlight the row where the cursor sits. Matches vim's `:set cursorline`.
    /// Default `false`.
    pub cursorline: bool,
    /// Highlight the column where the cursor sits. Matches vim's `:set cursorcolumn`.
    /// Default `false`.
    pub cursorcolumn: bool,
    /// Sign-column display mode. Matches vim's `:set signcolumn`.
    /// Default [`crate::types::SignColumnMode::Auto`].
    pub signcolumn: crate::types::SignColumnMode,
    /// Number of cells reserved for a fold-marker gutter.
    /// Matches vim's `:set foldcolumn`. Default `0`.
    pub foldcolumn: u32,
    /// Comma-separated 1-based column indices for vertical rulers.
    /// Matches vim's `:set colorcolumn`. Default `""`.
    pub colorcolumn: String,
}

impl Default for Settings {
    fn default() -> Self {
        Self {
            shiftwidth: 4,
            tabstop: 4,
            softtabstop: 4,
            ignore_case: false,
            smartcase: false,
            wrapscan: true,
            textwidth: 79,
            expandtab: true,
            wrap: hjkl_buffer::Wrap::None,
            readonly: false,
            autoindent: true,
            smartindent: true,
            undo_levels: 1000,
            undo_break_on_motion: true,
            iskeyword: "@,48-57,_,192-255".to_string(),
            timeout_len: core::time::Duration::from_millis(1000),
            number: true,
            relativenumber: false,
            numberwidth: 4,
            cursorline: false,
            cursorcolumn: false,
            signcolumn: crate::types::SignColumnMode::Auto,
            foldcolumn: 0,
            colorcolumn: String::new(),
        }
    }
}

/// Translate a SPEC [`crate::types::Options`] into the engine's
/// internal [`Settings`] representation. Field-by-field map; the
/// shapes are isomorphic except for type widths
/// (`u32` vs `usize`, [`crate::types::WrapMode`] vs
/// [`hjkl_buffer::Wrap`]). 0.1.0 (Patch C-δ) collapses both into one
/// type once the `Editor<B, H>::new(buffer, host, options)` constructor
/// is the canonical entry point.
fn settings_from_options(o: &crate::types::Options) -> Settings {
    Settings {
        shiftwidth: o.shiftwidth as usize,
        tabstop: o.tabstop as usize,
        softtabstop: o.softtabstop as usize,
        ignore_case: o.ignorecase,
        smartcase: o.smartcase,
        wrapscan: o.wrapscan,
        textwidth: o.textwidth as usize,
        expandtab: o.expandtab,
        wrap: match o.wrap {
            crate::types::WrapMode::None => hjkl_buffer::Wrap::None,
            crate::types::WrapMode::Char => hjkl_buffer::Wrap::Char,
            crate::types::WrapMode::Word => hjkl_buffer::Wrap::Word,
        },
        readonly: o.readonly,
        autoindent: o.autoindent,
        smartindent: o.smartindent,
        undo_levels: o.undo_levels,
        undo_break_on_motion: o.undo_break_on_motion,
        iskeyword: o.iskeyword.clone(),
        timeout_len: o.timeout_len,
        number: o.number,
        relativenumber: o.relativenumber,
        numberwidth: o.numberwidth,
        cursorline: o.cursorline,
        cursorcolumn: o.cursorcolumn,
        signcolumn: o.signcolumn,
        foldcolumn: o.foldcolumn,
        colorcolumn: o.colorcolumn.clone(),
    }
}

/// Host-observable LSP requests triggered by editor bindings. The
/// hjkl-engine crate doesn't talk to an LSP itself — it just raises an
/// intent that the TUI layer picks up and routes to `sqls`.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum LspIntent {
    /// `gd` — textDocument/definition at the cursor.
    GotoDefinition,
}

impl<H: crate::types::Host> Editor<hjkl_buffer::Buffer, H> {
    /// Build an [`Editor`] from a buffer, host adapter, and SPEC options.
    ///
    /// 0.1.0 (Patch C-δ): canonical, frozen constructor per SPEC §"Editor
    /// surface". Replaces the pre-0.1.0 `Editor::new(KeybindingMode)` /
    /// `with_host` / `with_options` triad — there is no shim.
    ///
    /// Consumers that don't need a custom host pass
    /// [`crate::types::DefaultHost::new()`]; consumers that don't need
    /// custom options pass [`crate::types::Options::default()`].
    pub fn new(buffer: hjkl_buffer::Buffer, host: H, options: crate::types::Options) -> Self {
        let settings = settings_from_options(&options);
        Self {
            keybinding_mode: KeybindingMode::Vim,
            last_yank: None,
            vim: VimState::default(),
            undo_stack: Vec::new(),
            redo_stack: Vec::new(),
            content_dirty: false,
            cached_content: None,
            viewport_height: AtomicU16::new(0),
            pending_lsp: None,
            pending_fold_ops: Vec::new(),
            buffer,
            #[cfg(feature = "ratatui")]
            style_table: Vec::new(),
            #[cfg(not(feature = "ratatui"))]
            engine_style_table: Vec::new(),
            registers: crate::registers::Registers::default(),
            #[cfg(feature = "ratatui")]
            styled_spans: Vec::new(),
            settings,
            marks: std::collections::BTreeMap::new(),
            syntax_fold_ranges: Vec::new(),
            change_log: Vec::new(),
            sticky_col: None,
            host,
            last_emitted_mode: crate::VimMode::Normal,
            search_state: crate::search::SearchState::new(),
            buffer_spans: Vec::new(),
            pending_content_edits: Vec::new(),
            pending_content_reset: false,
            last_indent_range: None,
        }
    }
}

impl<B: crate::types::Buffer, H: crate::types::Host> Editor<B, H> {
    /// Borrow the buffer (typed `&B`). Host renders through this via
    /// `hjkl_buffer::BufferView` when `B = hjkl_buffer::Buffer`.
    pub fn buffer(&self) -> &B {
        &self.buffer
    }

    /// Mutably borrow the buffer (typed `&mut B`).
    pub fn buffer_mut(&mut self) -> &mut B {
        &mut self.buffer
    }

    /// Borrow the host adapter directly (typed `&H`).
    pub fn host(&self) -> &H {
        &self.host
    }

    /// Mutably borrow the host adapter (typed `&mut H`).
    pub fn host_mut(&mut self) -> &mut H {
        &mut self.host
    }
}

impl<H: crate::types::Host> Editor<hjkl_buffer::Buffer, H> {
    /// Update the active `iskeyword` spec for word motions
    /// (`w`/`b`/`e`/`ge` and engine-side `*`/`#` pickup). 0.0.28
    /// hoisted iskeyword storage out of `Buffer` — `Editor` is the
    /// single owner now. Equivalent to assigning
    /// `settings_mut().iskeyword` directly; the dedicated setter is
    /// retained for source-compatibility with 0.0.27 callers.
    pub fn set_iskeyword(&mut self, spec: impl Into<String>) {
        self.settings.iskeyword = spec.into();
    }

    /// Emit `Host::emit_cursor_shape` if the public mode has changed
    /// since the last emit. Engine calls this at the end of every input
    /// step so mode transitions surface to the host without sprinkling
    /// the call across every `vim.mode = ...` site.
    pub fn emit_cursor_shape_if_changed(&mut self) {
        let mode = self.vim_mode();
        if mode == self.last_emitted_mode {
            return;
        }
        let shape = match mode {
            crate::VimMode::Insert => crate::types::CursorShape::Bar,
            _ => crate::types::CursorShape::Block,
        };
        self.host.emit_cursor_shape(shape);
        self.last_emitted_mode = mode;
    }

    /// Record a yank/cut payload. Writes both the legacy
    /// [`Editor::last_yank`] field (drained directly by 0.0.28-era
    /// hosts) and the new [`crate::types::Host::write_clipboard`]
    /// side-channel (Patch B). Consumers should migrate to a `Host`
    /// impl whose `write_clipboard` queues the platform-clipboard
    /// write; the `last_yank` mirror will be removed at 0.1.0.
    pub(crate) fn record_yank_to_host(&mut self, text: String) {
        self.host.write_clipboard(text.clone());
        self.last_yank = Some(text);
    }

    /// Vim's sticky column (curswant). `None` before the first motion;
    /// hosts shouldn't normally need to read this directly — it's
    /// surfaced for migration off `Buffer::sticky_col` and for
    /// snapshot tests.
    pub fn sticky_col(&self) -> Option<usize> {
        self.sticky_col
    }

    /// Replace the sticky column. Hosts should rarely touch this —
    /// motion code maintains it through the standard horizontal /
    /// vertical motion paths.
    pub fn set_sticky_col(&mut self, col: Option<usize>) {
        self.sticky_col = col;
    }

    /// Host hook: replace the cached syntax-derived block ranges that
    /// `:foldsyntax` consumes. the host calls this on every re-parse;
    /// the cost is just a `Vec` swap.
    /// Look up a named mark by character. Returns `(row, col)` if
    /// set; `None` otherwise. Both lowercase (`'a`–`'z`) and
    /// uppercase (`'A`–`'Z`) marks live in the same unified
    /// [`Editor::marks`] map as of 0.0.36.
    pub fn mark(&self, c: char) -> Option<(usize, usize)> {
        self.marks.get(&c).copied()
    }

    /// Set the named mark `c` to `(row, col)`. Used by the FSM's
    /// `m{a-zA-Z}` keystroke and by [`Editor::restore_snapshot`].
    pub fn set_mark(&mut self, c: char, pos: (usize, usize)) {
        self.marks.insert(c, pos);
    }

    /// Remove the named mark `c` (no-op if unset).
    pub fn clear_mark(&mut self, c: char) {
        self.marks.remove(&c);
    }

    /// Look up a buffer-local lowercase mark (`'a`–`'z`). Kept as a
    /// thin wrapper over [`Editor::mark`] for source compatibility
    /// with pre-0.0.36 callers; new code should call
    /// [`Editor::mark`] directly.
    #[deprecated(
        since = "0.0.36",
        note = "use Editor::mark — lowercase + uppercase marks now live in a single map"
    )]
    pub fn buffer_mark(&self, c: char) -> Option<(usize, usize)> {
        self.mark(c)
    }

    /// Discard the most recent undo entry. Used by ex commands that
    /// pre-emptively pushed an undo state (`:s`, `:r`) but ended up
    /// matching nothing — popping prevents a no-op undo step from
    /// polluting the user's history.
    ///
    /// Returns `true` if an entry was discarded.
    pub fn pop_last_undo(&mut self) -> bool {
        self.undo_stack.pop().is_some()
    }

    /// Read all named marks set this session — both lowercase
    /// (`'a`–`'z`) and uppercase (`'A`–`'Z`). Iteration is
    /// deterministic (BTreeMap-ordered) so snapshot / `:marks`
    /// output is stable.
    pub fn marks(&self) -> impl Iterator<Item = (char, (usize, usize))> + '_ {
        self.marks.iter().map(|(c, p)| (*c, *p))
    }

    /// Read all buffer-local lowercase marks. Kept for source
    /// compatibility with pre-0.0.36 callers (e.g. `:marks` ex
    /// command); new code should use [`Editor::marks`] which
    /// iterates the unified map.
    #[deprecated(
        since = "0.0.36",
        note = "use Editor::marks — lowercase + uppercase marks now live in a single map"
    )]
    pub fn buffer_marks(&self) -> impl Iterator<Item = (char, (usize, usize))> + '_ {
        self.marks
            .iter()
            .filter(|(c, _)| c.is_ascii_lowercase())
            .map(|(c, p)| (*c, *p))
    }

    /// Position the cursor was at when the user last jumped via
    /// `<C-o>` / `g;` / similar. `None` before any jump.
    pub fn last_jump_back(&self) -> Option<(usize, usize)> {
        self.vim.jump_back.last().copied()
    }

    /// Position of the last edit (where `.` would replay). `None` if
    /// no edit has happened yet in this session.
    pub fn last_edit_pos(&self) -> Option<(usize, usize)> {
        self.vim.last_edit_pos
    }

    /// Read-only view of the file-marks table — uppercase / "file"
    /// marks (`'A`–`'Z`) the host has set this session. Returns an
    /// iterator of `(mark_char, (row, col))` pairs.
    ///
    /// Mutate via the FSM (`m{A-Z}` keystroke) or via
    /// [`Editor::restore_snapshot`].
    ///
    /// 0.0.36: file marks now live in the unified [`Editor::marks`]
    /// map; this accessor is kept for source compatibility and
    /// filters the unified map to uppercase entries.
    pub fn file_marks(&self) -> impl Iterator<Item = (char, (usize, usize))> + '_ {
        self.marks
            .iter()
            .filter(|(c, _)| c.is_ascii_uppercase())
            .map(|(c, p)| (*c, *p))
    }

    /// Read-only view of the cached syntax-derived block ranges that
    /// `:foldsyntax` consumes. Returns the slice the host last
    /// installed via [`Editor::set_syntax_fold_ranges`]; empty when
    /// no syntax integration is active.
    pub fn syntax_fold_ranges(&self) -> &[(usize, usize)] {
        &self.syntax_fold_ranges
    }

    pub fn set_syntax_fold_ranges(&mut self, ranges: Vec<(usize, usize)>) {
        self.syntax_fold_ranges = ranges;
    }

    /// Live settings (read-only). `:set` mutates these via
    /// [`Editor::settings_mut`].
    pub fn settings(&self) -> &Settings {
        &self.settings
    }

    /// Live settings (mutable). `:set` flows through here to mutate
    /// shiftwidth / tabstop / textwidth / ignore_case / wrap. Hosts
    /// configuring at startup typically construct a [`Settings`]
    /// snapshot and overwrite via `*editor.settings_mut() = …`.
    pub fn settings_mut(&mut self) -> &mut Settings {
        &mut self.settings
    }

    /// Returns `true` when `:set readonly` is active. Convenience
    /// accessor for hosts that cannot import the internal [`Settings`]
    /// type. Phase 5 binary uses this to gate `:w` writes.
    pub fn is_readonly(&self) -> bool {
        self.settings.readonly
    }

    /// Borrow the engine search state. Hosts inspecting the
    /// committed `/` / `?` pattern (e.g. for status-line display) or
    /// feeding the active regex into `BufferView::search_pattern`
    /// read it from here.
    pub fn search_state(&self) -> &crate::search::SearchState {
        &self.search_state
    }

    /// Mutable engine search state. Hosts driving search
    /// programmatically (test fixtures, scripted demos) write the
    /// pattern through here.
    pub fn search_state_mut(&mut self) -> &mut crate::search::SearchState {
        &mut self.search_state
    }

    /// Install `pattern` as the active search regex on the engine
    /// state and clear the cached row matches. Pass `None` to clear.
    /// 0.0.37: dropped the buffer-side mirror that 0.0.35 introduced
    /// — `BufferView` now takes the regex through its `search_pattern`
    /// field per step 3 of `DESIGN_33_METHOD_CLASSIFICATION.md`.
    pub fn set_search_pattern(&mut self, pattern: Option<regex::Regex>) {
        self.search_state.set_pattern(pattern);
    }

    /// Drive `n` (or the `/` commit equivalent) — advance the cursor
    /// to the next match of `search_state.pattern` from the cursor's
    /// current position. Returns `true` when a match was found.
    /// `skip_current = true` excludes a match the cursor sits on.
    pub fn search_advance_forward(&mut self, skip_current: bool) -> bool {
        crate::search::search_forward(&mut self.buffer, &mut self.search_state, skip_current)
    }

    /// Drive `N` — symmetric counterpart of [`Editor::search_advance_forward`].
    pub fn search_advance_backward(&mut self, skip_current: bool) -> bool {
        crate::search::search_backward(&mut self.buffer, &mut self.search_state, skip_current)
    }

    /// Install styled syntax spans using `ratatui::style::Style`. The
    /// ratatui-flavoured variant of [`Editor::install_syntax_spans`].
    /// Drops zero-width runs and clamps `end` to the line's char length
    /// so the buffer cache doesn't see runaway ranges. Behind the
    /// `ratatui` feature; non-ratatui hosts use the unprefixed
    /// [`Editor::install_syntax_spans`] (engine-native `Style`).
    ///
    /// Renamed from `install_syntax_spans` in 0.0.32 — the unprefixed
    /// name now belongs to the engine-native variant per SPEC 0.1.0
    /// freeze ("engine never imports ratatui").
    #[cfg(feature = "ratatui")]
    pub fn install_ratatui_syntax_spans(
        &mut self,
        spans: Vec<Vec<(usize, usize, ratatui::style::Style)>>,
    ) {
        // Look up `line_byte_lens` lazily — only fetch a row's length
        // when it has at least one span. On a 100k-line file with
        // ~50 visible rows, this avoids an O(N) buffer walk per frame.
        let mut by_row: Vec<Vec<hjkl_buffer::Span>> = Vec::with_capacity(spans.len());
        for (row, row_spans) in spans.iter().enumerate() {
            if row_spans.is_empty() {
                by_row.push(Vec::new());
                continue;
            }
            let line_len = buf_line(&self.buffer, row).map(str::len).unwrap_or(0);
            let mut translated = Vec::with_capacity(row_spans.len());
            for (start, end, style) in row_spans {
                let end_clamped = (*end).min(line_len);
                if end_clamped <= *start {
                    continue;
                }
                let id = self.intern_ratatui_style(*style);
                translated.push(hjkl_buffer::Span::new(*start, end_clamped, id));
            }
            by_row.push(translated);
        }
        self.buffer_spans = by_row;
        self.styled_spans = spans;
    }

    /// Snapshot of the unnamed register (the default `p` / `P` source).
    pub fn yank(&self) -> &str {
        &self.registers.unnamed.text
    }

    /// Borrow the full register bank — `"`, `"0`–`"9`, `"a`–`"z`.
    pub fn registers(&self) -> &crate::registers::Registers {
        &self.registers
    }

    /// Mutably borrow the full register bank. Hosts that share registers
    /// across multiple editors (e.g. multi-buffer `yy` / `p`) overwrite
    /// the slots here on buffer switch.
    pub fn registers_mut(&mut self) -> &mut crate::registers::Registers {
        &mut self.registers
    }

    /// Host hook: load the OS clipboard's contents into the `"+` / `"*`
    /// register slot. the host calls this before letting vim consume a
    /// paste so `"*p` / `"+p` reflect the live clipboard rather than a
    /// stale snapshot from the last yank.
    pub fn sync_clipboard_register(&mut self, text: String, linewise: bool) {
        self.registers.set_clipboard(text, linewise);
    }

    /// Return the user's pending register selection (set via `"<reg>` chord
    /// before an operator). `None` if no register was selected — caller should
    /// use the unnamed register `"`.
    ///
    /// Read-only — does not consume / clear the pending selection. The
    /// register is cleared by the engine after the next operator fires.
    ///
    /// Promoted in 0.6.X for Phase 4e to let the App's visual-op dispatch arm
    /// honor `"a` + visual op chord sequences.
    pub fn pending_register(&self) -> Option<char> {
        self.vim.pending_register
    }

    /// True when the user's pending register selector is `+` or `*`.
    /// the host peeks this so it can refresh `sync_clipboard_register`
    /// only when a clipboard read is actually about to happen.
    pub fn pending_register_is_clipboard(&self) -> bool {
        matches!(self.vim.pending_register, Some('+') | Some('*'))
    }

    /// Register currently being recorded into via `q{reg}`. `None` when
    /// no recording is active. Hosts use this to surface a "recording @r"
    /// indicator in the status line.
    pub fn recording_register(&self) -> Option<char> {
        self.vim.recording_macro
    }

    /// Pending repeat count the user has typed but not yet resolved
    /// (e.g. pressing `5` before `d`). `None` when nothing is pending.
    /// Hosts surface this in a "showcmd" area.
    pub fn pending_count(&self) -> Option<u32> {
        self.vim.pending_count_val()
    }

    /// The operator character for any in-flight operator that is waiting
    /// for a motion (e.g. `d` after the user types `d` but before a
    /// motion). Returns `None` when no operator is pending.
    pub fn pending_op(&self) -> Option<char> {
        self.vim.pending_op_char()
    }

    /// `true` when the engine is in any pending chord state — waiting for
    /// the next key to complete a command (e.g. `r<char>` replace,
    /// `f<char>` find, `m<a>` set-mark, `'<a>` goto-mark, operator-pending
    /// after `d` / `c` / `y`, `g`-prefix continuation, `z`-prefix continuation,
    /// register selection `"<reg>`, macro recording target, etc).
    ///
    /// Hosts use this to bypass their own chord dispatch (keymap tries, etc.)
    /// and forward keys directly to the engine so in-flight commands can
    /// complete without the host eating their continuation keys.
    pub fn is_chord_pending(&self) -> bool {
        self.vim.is_chord_pending()
    }

    /// `true` when `insert_ctrl_r_arm()` has been called and the dispatcher
    /// is waiting for the next typed character to name the register to paste.
    /// The dispatcher should call `insert_paste_register(c)` instead of
    /// `insert_char(c)` for the next printable key, then the flag auto-clears.
    ///
    /// Phase 6.5: exposed so the app-level `dispatch_insert_key` can branch
    /// without having to drive the full FSM.
    pub fn is_insert_register_pending(&self) -> bool {
        self.vim.insert_pending_register
    }

    /// Clear the `Ctrl-R` register-paste pending flag. Call this immediately
    /// before `insert_paste_register(c)` in app-level dispatchers so that the
    /// flag does not persist into the next key. Call before
    /// `insert_paste_register_bridge` (which `hjkl_vim::insert` does).
    ///
    /// Phase 6.5: used by `dispatch_insert_key` in the app crate.
    pub fn clear_insert_register_pending(&mut self) {
        self.vim.insert_pending_register = false;
    }

    /// Read-only view of the jump-back list (positions pushed on "big"
    /// motions). Newest entry is at the back — `Ctrl-o` pops from there.
    #[allow(clippy::type_complexity)]
    pub fn jump_list(&self) -> (&[(usize, usize)], &[(usize, usize)]) {
        (&self.vim.jump_back, &self.vim.jump_fwd)
    }

    /// Read-only view of the change list (positions of recent edits) plus
    /// the current walk cursor. Newest entry is at the back.
    pub fn change_list(&self) -> (&[(usize, usize)], Option<usize>) {
        (&self.vim.change_list, self.vim.change_list_cursor)
    }

    /// Replace the unnamed register without touching any other slot.
    /// For host-driven imports (e.g. system clipboard); operator
    /// code uses [`record_yank`] / [`record_delete`].
    pub fn set_yank(&mut self, text: impl Into<String>) {
        let text = text.into();
        let linewise = self.vim.yank_linewise;
        self.registers.unnamed = crate::registers::Slot { text, linewise };
    }

    /// Record a yank into `"` and `"0`, plus the named target if the
    /// user prefixed `"reg`. Updates `vim.yank_linewise` for the
    /// paste path.
    pub(crate) fn record_yank(&mut self, text: String, linewise: bool) {
        self.vim.yank_linewise = linewise;
        let target = self.vim.pending_register.take();
        self.registers.record_yank(text, linewise, target);
    }

    /// Direct write to a named register slot — bypasses the unnamed
    /// `"` and `"0` updates that `record_yank` does. Used by the
    /// macro recorder so finishing a `q{reg}` recording doesn't
    /// pollute the user's last yank.
    pub(crate) fn set_named_register_text(&mut self, reg: char, text: String) {
        if let Some(slot) = match reg {
            'a'..='z' => Some(&mut self.registers.named[(reg as u8 - b'a') as usize]),
            'A'..='Z' => {
                Some(&mut self.registers.named[(reg.to_ascii_lowercase() as u8 - b'a') as usize])
            }
            _ => None,
        } {
            slot.text = text;
            slot.linewise = false;
        }
    }

    /// Record a delete / change into `"` and the `"1`–`"9` ring.
    /// Honours the active named-register prefix.
    pub(crate) fn record_delete(&mut self, text: String, linewise: bool) {
        self.vim.yank_linewise = linewise;
        let target = self.vim.pending_register.take();
        self.registers.record_delete(text, linewise, target);
    }

    /// Install styled syntax spans using the engine-native
    /// [`crate::types::Style`]. Always available, regardless of the
    /// `ratatui` feature. Hosts depending on ratatui can use the
    /// ratatui-flavoured [`Editor::install_ratatui_syntax_spans`].
    ///
    /// Renamed from `install_engine_syntax_spans` in 0.0.32 — at the
    /// 0.1.0 freeze the unprefixed name is the universally-available
    /// engine-native variant ("engine never imports ratatui").
    pub fn install_syntax_spans(&mut self, spans: Vec<Vec<(usize, usize, crate::types::Style)>>) {
        let line_byte_lens: Vec<usize> = (0..buf_row_count(&self.buffer))
            .map(|r| buf_line(&self.buffer, r).map(str::len).unwrap_or(0))
            .collect();
        let mut by_row: Vec<Vec<hjkl_buffer::Span>> = Vec::with_capacity(spans.len());
        #[cfg(feature = "ratatui")]
        let mut ratatui_spans: Vec<Vec<(usize, usize, ratatui::style::Style)>> =
            Vec::with_capacity(spans.len());
        for (row, row_spans) in spans.iter().enumerate() {
            let line_len = line_byte_lens.get(row).copied().unwrap_or(0);
            let mut translated = Vec::with_capacity(row_spans.len());
            #[cfg(feature = "ratatui")]
            let mut translated_r = Vec::with_capacity(row_spans.len());
            for (start, end, style) in row_spans {
                let end_clamped = (*end).min(line_len);
                if end_clamped <= *start {
                    continue;
                }
                let id = self.intern_style(*style);
                translated.push(hjkl_buffer::Span::new(*start, end_clamped, id));
                #[cfg(feature = "ratatui")]
                translated_r.push((*start, end_clamped, engine_style_to_ratatui(*style)));
            }
            by_row.push(translated);
            #[cfg(feature = "ratatui")]
            ratatui_spans.push(translated_r);
        }
        self.buffer_spans = by_row;
        #[cfg(feature = "ratatui")]
        {
            self.styled_spans = ratatui_spans;
        }
    }

    /// Intern a `ratatui::style::Style` and return the opaque id used
    /// in `hjkl_buffer::Span::style`. The ratatui-flavoured variant of
    /// [`Editor::intern_style`]. Linear-scan dedup — the table grows
    /// only as new tree-sitter token kinds appear, so it stays tiny.
    /// Behind the `ratatui` feature.
    ///
    /// Renamed from `intern_style` in 0.0.32 — at 0.1.0 freeze the
    /// unprefixed name belongs to the engine-native variant.
    #[cfg(feature = "ratatui")]
    pub fn intern_ratatui_style(&mut self, style: ratatui::style::Style) -> u32 {
        if let Some(idx) = self.style_table.iter().position(|s| *s == style) {
            return idx as u32;
        }
        self.style_table.push(style);
        (self.style_table.len() - 1) as u32
    }

    /// Read-only view of the style table — id `i` → `style_table[i]`.
    /// The render path passes a closure backed by this slice as the
    /// `StyleResolver` for `BufferView`. Behind the `ratatui` feature.
    #[cfg(feature = "ratatui")]
    pub fn style_table(&self) -> &[ratatui::style::Style] {
        &self.style_table
    }

    /// Per-row syntax span overlay, one `Vec<Span>` per buffer row.
    /// Hosts feed this slice into [`hjkl_buffer::BufferView::spans`]
    /// per draw frame.
    ///
    /// 0.0.37: replaces `editor.buffer().spans()` per step 3 of
    /// `DESIGN_33_METHOD_CLASSIFICATION.md`. The buffer no longer
    /// caches spans; they live on the engine and route through the
    /// `Host::syntax_highlights` pipeline.
    pub fn buffer_spans(&self) -> &[Vec<hjkl_buffer::Span>] {
        &self.buffer_spans
    }

    /// Intern a SPEC [`crate::types::Style`] and return its opaque id.
    /// With the `ratatui` feature on, the id matches the one
    /// [`Editor::intern_ratatui_style`] would return for the equivalent
    /// `ratatui::Style` (both share the underlying table). With it off,
    /// the engine keeps a parallel `crate::types::Style`-keyed table
    /// — ids are still stable per-editor.
    ///
    /// Hosts that don't depend on ratatui (buffr, future GUI shells)
    /// reach this method to populate the table during syntax span
    /// installation.
    ///
    /// Renamed from `intern_engine_style` in 0.0.32 — at 0.1.0 freeze
    /// the unprefixed name is the universally-available engine-native
    /// variant.
    pub fn intern_style(&mut self, style: crate::types::Style) -> u32 {
        #[cfg(feature = "ratatui")]
        {
            let r = engine_style_to_ratatui(style);
            self.intern_ratatui_style(r)
        }
        #[cfg(not(feature = "ratatui"))]
        {
            if let Some(idx) = self.engine_style_table.iter().position(|s| *s == style) {
                return idx as u32;
            }
            self.engine_style_table.push(style);
            (self.engine_style_table.len() - 1) as u32
        }
    }

    /// Look up an interned style by id and return it as a SPEC
    /// [`crate::types::Style`]. Returns `None` for ids past the end
    /// of the table.
    pub fn engine_style_at(&self, id: u32) -> Option<crate::types::Style> {
        #[cfg(feature = "ratatui")]
        {
            let r = self.style_table.get(id as usize).copied()?;
            Some(ratatui_style_to_engine(r))
        }
        #[cfg(not(feature = "ratatui"))]
        {
            self.engine_style_table.get(id as usize).copied()
        }
    }

    /// Historical reverse-sync hook from when the textarea mirrored
    /// the buffer. Now that Buffer is the cursor authority this is a
    /// no-op; call sites can remain in place during the migration.
    pub fn push_buffer_cursor_to_textarea(&mut self) {}

    /// Force the host viewport's top row without touching the
    /// cursor. Used by tests that simulate a scroll without the
    /// SCROLLOFF cursor adjustment that `scroll_down` / `scroll_up`
    /// apply.
    ///
    /// 0.0.34 (Patch C-δ.1): writes through `Host::viewport_mut`
    /// instead of the (now-deleted) `Buffer::viewport_mut`.
    pub fn set_viewport_top(&mut self, row: usize) {
        let last = buf_row_count(&self.buffer).saturating_sub(1);
        let target = row.min(last);
        self.host.viewport_mut().top_row = target;
    }

    /// Set the cursor to `(row, col)`, clamped to the buffer's
    /// content. Hosts use this for goto-line, jump-to-mark, and
    /// programmatic cursor placement.
    pub fn jump_cursor(&mut self, row: usize, col: usize) {
        buf_set_cursor_rc(&mut self.buffer, row, col);
    }

    /// `(row, col)` cursor read sourced from the migration buffer.
    /// Equivalent to `self.textarea.cursor()` when the two are in
    /// sync — which is the steady state during Phase 7f because
    /// every step opens with `sync_buffer_content_from_textarea` and
    /// every ported motion pushes the result back. Prefer this over
    /// `self.textarea.cursor()` so call sites keep working unchanged
    /// once the textarea field is ripped.
    pub fn cursor(&self) -> (usize, usize) {
        buf_cursor_rc(&self.buffer)
    }

    /// Drain any pending LSP intent raised by the last key. Returns
    /// `None` when no intent is armed.
    pub fn take_lsp_intent(&mut self) -> Option<LspIntent> {
        self.pending_lsp.take()
    }

    /// Drain every [`crate::types::FoldOp`] raised since the last
    /// call. Hosts that mirror the engine's fold storage (or that
    /// project folds onto a separate fold tree, LSP folding ranges,
    /// …) drain this each step and dispatch as their own
    /// [`crate::types::Host::Intent`] requires.
    ///
    /// The engine has already applied every op locally against the
    /// in-tree [`hjkl_buffer::Buffer`] fold storage via
    /// [`crate::buffer_impl::BufferFoldProviderMut`], so hosts that
    /// don't track folds independently can ignore the queue
    /// (or simply never call this drain).
    ///
    /// Introduced in 0.0.38 (Patch C-δ.4).
    pub fn take_fold_ops(&mut self) -> Vec<crate::types::FoldOp> {
        std::mem::take(&mut self.pending_fold_ops)
    }

    /// Dispatch a [`crate::types::FoldOp`] through the canonical fold
    /// surface: queue it for host observation (drained by
    /// [`Editor::take_fold_ops`]) and apply it locally against the
    /// in-tree buffer fold storage via
    /// [`crate::buffer_impl::BufferFoldProviderMut`]. Engine call sites
    /// (vim FSM `z…` chords, `:fold*` Ex commands, edit-pipeline
    /// invalidation) route every fold mutation through this method.
    ///
    /// Introduced in 0.0.38 (Patch C-δ.4).
    pub fn apply_fold_op(&mut self, op: crate::types::FoldOp) {
        use crate::types::FoldProvider;
        self.pending_fold_ops.push(op);
        let mut provider = crate::buffer_impl::BufferFoldProviderMut::new(&mut self.buffer);
        provider.apply(op);
    }

    /// Refresh the host viewport's height from the cached
    /// `viewport_height_value()`. Called from the per-step
    /// boilerplate; was the textarea → buffer mirror before Phase 7f
    /// put Buffer in charge. 0.0.28 hoisted sticky_col out of
    /// `Buffer`. 0.0.34 (Patch C-δ.1) routes the height write through
    /// `Host::viewport_mut`.
    pub(crate) fn sync_buffer_from_textarea(&mut self) {
        let height = self.viewport_height_value();
        self.host.viewport_mut().height = height;
    }

    /// Was the full textarea → buffer content sync. Buffer is the
    /// content authority now; this remains as a no-op so the per-step
    /// call sites don't have to be ripped in the same patch.
    pub(crate) fn sync_buffer_content_from_textarea(&mut self) {
        self.sync_buffer_from_textarea();
    }

    /// Push a `(row, col)` onto the back-jumplist so `Ctrl-o` returns
    /// to it later. Used by host-driven jumps (e.g. `gd`) that move
    /// the cursor without going through the vim engine's motion
    /// machinery, where push_jump fires automatically.
    pub fn record_jump(&mut self, pos: (usize, usize)) {
        const JUMPLIST_MAX: usize = 100;
        self.vim.jump_back.push(pos);
        if self.vim.jump_back.len() > JUMPLIST_MAX {
            self.vim.jump_back.remove(0);
        }
        self.vim.jump_fwd.clear();
    }

    /// Host apps call this each draw with the current text area height so
    /// scroll helpers can clamp the cursor without recomputing layout.
    pub fn set_viewport_height(&self, height: u16) {
        self.viewport_height.store(height, Ordering::Relaxed);
    }

    /// Last height published by `set_viewport_height` (in rows).
    pub fn viewport_height_value(&self) -> u16 {
        self.viewport_height.load(Ordering::Relaxed)
    }

    /// Apply `edit` against the buffer and return the inverse so the
    /// host can push it onto an undo stack. Side effects: dirty
    /// flag, change-list ring, mark / jump-list shifts, change_log
    /// append, fold invalidation around the touched rows.
    ///
    /// The primary edit funnel — both FSM operators and ex commands
    /// route mutations through here so the side effects fire
    /// uniformly.
    pub fn mutate_edit(&mut self, edit: hjkl_buffer::Edit) -> hjkl_buffer::Edit {
        // `:set readonly` short-circuits every mutation funnel: no
        // buffer change, no dirty flag, no undo entry, no change-log
        // emission. We swallow the requested `edit` and hand back a
        // self-inverse no-op (`InsertStr` of an empty string at the
        // current cursor) so callers that push the return value onto
        // an undo stack still get a structurally valid round trip.
        if self.settings.readonly {
            let _ = edit;
            return hjkl_buffer::Edit::InsertStr {
                at: buf_cursor_pos(&self.buffer),
                text: String::new(),
            };
        }
        let pre_row = buf_cursor_row(&self.buffer);
        let pre_rows = buf_row_count(&self.buffer);
        // Capture the pre-edit cursor for the dot mark (`'.` / `` `. ``).
        // Vim's `:h '.` says "the position where the last change was made",
        // meaning the change-start, not the post-insert cursor. We snap it
        // here before `apply_buffer_edit` moves the cursor.
        let (pre_edit_row, pre_edit_col) = buf_cursor_rc(&self.buffer);
        // Map the underlying buffer edit to a SPEC EditOp for
        // change-log emission before consuming it. Coarse — see
        // change_log field doc on the struct.
        self.change_log.extend(edit_to_editops(&edit));
        // Compute ContentEdit fan-out from the pre-edit buffer state.
        // Done before `apply_buffer_edit` consumes `edit` so we can
        // inspect the operation's fields and the buffer's pre-edit row
        // bytes (needed for byte_of_row / col_byte conversion). Edits
        // are pushed onto `pending_content_edits` for host drain.
        let content_edits = content_edits_from_buffer_edit(&self.buffer, &edit);
        self.pending_content_edits.extend(content_edits);
        // 0.0.42 (Patch C-δ.7): the `apply_edit` reach is centralized
        // in [`crate::buf_helpers::apply_buffer_edit`] (option (c) of
        // the 0.0.42 plan — see that fn's doc comment). The free fn
        // takes `&mut hjkl_buffer::Buffer` so the editor body itself
        // no longer carries a `self.buffer.<inherent>` hop.
        let inverse = apply_buffer_edit(&mut self.buffer, edit);
        let (pos_row, pos_col) = buf_cursor_rc(&self.buffer);
        // Drop any folds the edit's range overlapped — vim opens the
        // surrounding fold automatically when you edit inside it. The
        // approximation here invalidates folds covering either the
        // pre-edit cursor row or the post-edit cursor row, which
        // catches the common single-line / multi-line edit shapes.
        let lo = pre_row.min(pos_row);
        let hi = pre_row.max(pos_row);
        self.apply_fold_op(crate::types::FoldOp::Invalidate {
            start_row: lo,
            end_row: hi,
        });
        // Dot mark records the PRE-edit position (change start), matching
        // vim's `:h '.` semantics. Previously this stored the post-edit
        // cursor, which diverged from nvim on `iX<Esc>j`.
        self.vim.last_edit_pos = Some((pre_edit_row, pre_edit_col));
        // Append to the change-list ring (skip when the cursor sits on
        // the same cell as the last entry — back-to-back keystrokes on
        // one column shouldn't pollute the ring). A new edit while
        // walking the ring trims the forward half, vim style.
        let entry = (pos_row, pos_col);
        if self.vim.change_list.last() != Some(&entry) {
            if let Some(idx) = self.vim.change_list_cursor.take() {
                self.vim.change_list.truncate(idx + 1);
            }
            self.vim.change_list.push(entry);
            let len = self.vim.change_list.len();
            if len > crate::vim::CHANGE_LIST_MAX {
                self.vim
                    .change_list
                    .drain(0..len - crate::vim::CHANGE_LIST_MAX);
            }
        }
        self.vim.change_list_cursor = None;
        // Shift / drop marks + jump-list entries to track the row
        // delta the edit produced. Without this, every line-changing
        // edit silently invalidates `'a`-style positions.
        let post_rows = buf_row_count(&self.buffer);
        let delta = post_rows as isize - pre_rows as isize;
        if delta != 0 {
            self.shift_marks_after_edit(pre_row, delta);
        }
        self.push_buffer_content_to_textarea();
        self.mark_content_dirty();
        inverse
    }

    /// Migrate user marks + jumplist entries when an edit at row
    /// `edit_start` changes the buffer's row count by `delta` (positive
    /// for inserts, negative for deletes). Marks tied to a deleted row
    /// are dropped; marks past the affected band shift by `delta`.
    fn shift_marks_after_edit(&mut self, edit_start: usize, delta: isize) {
        if delta == 0 {
            return;
        }
        // Deleted-row band (only meaningful for delta < 0). Inclusive
        // start, exclusive end.
        let drop_end = if delta < 0 {
            edit_start.saturating_add((-delta) as usize)
        } else {
            edit_start
        };
        let shift_threshold = drop_end.max(edit_start.saturating_add(1));

        // 0.0.36: lowercase + uppercase marks share the unified
        // `marks` map; one pass migrates both.
        let mut to_drop: Vec<char> = Vec::new();
        for (c, (row, _col)) in self.marks.iter_mut() {
            if (edit_start..drop_end).contains(row) {
                to_drop.push(*c);
            } else if *row >= shift_threshold {
                *row = ((*row as isize) + delta).max(0) as usize;
            }
        }
        for c in to_drop {
            self.marks.remove(&c);
        }

        let shift_jumps = |entries: &mut Vec<(usize, usize)>| {
            entries.retain(|(row, _)| !(edit_start..drop_end).contains(row));
            for (row, _) in entries.iter_mut() {
                if *row >= shift_threshold {
                    *row = ((*row as isize) + delta).max(0) as usize;
                }
            }
        };
        shift_jumps(&mut self.vim.jump_back);
        shift_jumps(&mut self.vim.jump_fwd);
    }

    /// Reverse-sync helper paired with [`Editor::mutate_edit`]: rebuild
    /// the textarea from the buffer's lines + cursor, preserving yank
    /// text. Heavy (allocates a fresh `TextArea`) but correct; the
    /// textarea field disappears at the end of Phase 7f anyway.
    /// No-op since Buffer is the content authority. Retained as a
    /// shim so call sites in `mutate_edit` and friends don't have to
    /// be ripped in lockstep with the field removal.
    pub(crate) fn push_buffer_content_to_textarea(&mut self) {}

    /// Single choke-point for "the buffer just changed". Sets the
    /// dirty flag and drops the cached `content_arc` snapshot so
    /// subsequent reads rebuild from the live textarea. Callers
    /// mutating `textarea` directly (e.g. the TUI's bracketed-paste
    /// path) must invoke this to keep the cache honest.
    pub fn mark_content_dirty(&mut self) {
        self.content_dirty = true;
        self.cached_content = None;
    }

    /// Returns true if content changed since the last call, then clears the flag.
    pub fn take_dirty(&mut self) -> bool {
        let dirty = self.content_dirty;
        self.content_dirty = false;
        dirty
    }

    /// Drain the queue of [`crate::types::ContentEdit`]s emitted since
    /// the last call. Each entry corresponds to a single buffer
    /// mutation funnelled through [`Editor::mutate_edit`]; block edits
    /// fan out to one entry per row touched.
    ///
    /// Hosts call this each frame (after [`Editor::take_content_reset`])
    /// to fan edits into a tree-sitter parser via `Tree::edit`.
    pub fn take_content_edits(&mut self) -> Vec<crate::types::ContentEdit> {
        std::mem::take(&mut self.pending_content_edits)
    }

    /// Returns `true` if a bulk buffer replacement happened since the
    /// last call (e.g. `set_content` / `restore` / undo restore), then
    /// clears the flag. When this returns `true`, hosts should drop
    /// any retained syntax tree before consuming
    /// [`Editor::take_content_edits`].
    pub fn take_content_reset(&mut self) -> bool {
        let r = self.pending_content_reset;
        self.pending_content_reset = false;
        r
    }

    /// Pull-model coarse change observation. If content changed since
    /// the last call, returns `Some(Arc<String>)` with the new content
    /// and clears the dirty flag; otherwise returns `None`.
    ///
    /// Hosts that need fine-grained edit deltas (e.g., DOM patching at
    /// the character level) should diff against their own previous
    /// snapshot. The SPEC `take_changes() -> Vec<EditOp>` API lands
    /// once every edit path inside the engine is instrumented; this
    /// coarse form covers the pull-model use case in the meantime.
    pub fn take_content_change(&mut self) -> Option<std::sync::Arc<String>> {
        if !self.content_dirty {
            return None;
        }
        let arc = self.content_arc();
        self.content_dirty = false;
        Some(arc)
    }

    /// Returns the cursor's row within the visible textarea (0-based), updating
    /// the stored viewport top so subsequent calls remain accurate.
    pub fn cursor_screen_row(&mut self, height: u16) -> u16 {
        let cursor = buf_cursor_row(&self.buffer);
        let top = self.host.viewport().top_row;
        cursor.saturating_sub(top).min(height as usize - 1) as u16
    }

    /// Returns the cursor's screen position `(x, y)` for the textarea
    /// described by `(area_x, area_y, area_width, area_height)`.
    /// Accounts for line-number gutter, viewport scroll, and any extra
    /// gutter width to the left of the number column (sign column, fold
    /// column). Returns `None` if the cursor is outside the visible
    /// viewport. Always available (engine-native; no ratatui dependency).
    ///
    /// `extra_gutter_width` is added to the number-column width before
    /// computing the cursor x position. Callers (e.g. `apps/hjkl/src/render.rs`)
    /// pass `sign_w + fold_w` here so the cursor lands on the correct cell
    /// when a dedicated sign or fold column is present.
    ///
    /// Renamed from `cursor_screen_pos_xywh` in 0.0.32 — the
    /// ratatui-flavoured `Rect` variant is now
    /// [`Editor::cursor_screen_pos_in_rect`] (cfg `ratatui`).
    pub fn cursor_screen_pos(
        &self,
        area_x: u16,
        area_y: u16,
        area_width: u16,
        area_height: u16,
        extra_gutter_width: u16,
    ) -> Option<(u16, u16)> {
        let (pos_row, pos_col) = buf_cursor_rc(&self.buffer);
        let v = self.host.viewport();
        if pos_row < v.top_row || pos_col < v.top_col {
            return None;
        }
        let lnum_width = if self.settings.number || self.settings.relativenumber {
            let needed = buf_row_count(&self.buffer).to_string().len() + 1;
            needed.max(self.settings.numberwidth) as u16
        } else {
            0
        };
        // Full offset from the left edge of the window to the first text cell.
        let gutter_total = lnum_width + extra_gutter_width;
        let dy = (pos_row - v.top_row) as u16;
        // Convert char column to visual column so cursor lands on the
        // correct cell when the line contains tabs (which the renderer
        // expands to TAB_WIDTH stops). Tab width must match the renderer.
        let line = self.buffer.line(pos_row).unwrap_or("");
        let tab_width = if v.tab_width == 0 {
            4
        } else {
            v.tab_width as usize
        };
        let visual_pos = visual_col_for_char(line, pos_col, tab_width);
        let visual_top = visual_col_for_char(line, v.top_col, tab_width);
        let dx = (visual_pos - visual_top) as u16;
        if dy >= area_height || dx + gutter_total >= area_width {
            return None;
        }
        Some((area_x + gutter_total + dx, area_y + dy))
    }

    /// Ratatui [`Rect`]-flavoured wrapper around
    /// [`Editor::cursor_screen_pos`]. Behind the `ratatui` feature.
    ///
    /// Renamed from `cursor_screen_pos` in 0.0.32 — the unprefixed
    /// name now belongs to the engine-native variant.
    ///
    /// `extra_gutter_width` is the combined width of the sign column and
    /// fold column that sit to the left of the number column (and thus
    /// to the left of the text area). Pass `sign_w + fold_w` from the
    /// render layer.
    #[cfg(feature = "ratatui")]
    pub fn cursor_screen_pos_in_rect(
        &self,
        area: Rect,
        extra_gutter_width: u16,
    ) -> Option<(u16, u16)> {
        self.cursor_screen_pos(area.x, area.y, area.width, area.height, extra_gutter_width)
    }

    /// Returns the current vim mode. Phase 6.3: reads from the stable
    /// `current_mode` field (kept in sync by both the FSM step loop and
    /// the Phase 6.3 primitive bridges) rather than deriving from the
    /// FSM-internal `mode` field via `public_mode()`.
    pub fn vim_mode(&self) -> VimMode {
        self.vim.current_mode
    }

    /// Bounds of the active visual-block rectangle as
    /// `(top_row, bot_row, left_col, right_col)` — all inclusive.
    /// `None` when we're not in VisualBlock mode.
    /// Read-only view of the live `/` or `?` prompt. `None` outside
    /// search-prompt mode.
    pub fn search_prompt(&self) -> Option<&crate::vim::SearchPrompt> {
        self.vim.search_prompt.as_ref()
    }

    /// Most recent committed search pattern (persists across `n` / `N`
    /// and across prompt exits). `None` before the first search.
    pub fn last_search(&self) -> Option<&str> {
        self.vim.last_search.as_deref()
    }

    /// Whether the last committed search was a forward `/` (`true`) or
    /// a backward `?` (`false`). `n` and `N` consult this to honour the
    /// direction the user committed.
    pub fn last_search_forward(&self) -> bool {
        self.vim.last_search_forward
    }

    /// Set the most recent committed search text + direction. Used by
    /// host-driven prompts (e.g. apps/hjkl's `/` `?` prompt that lives
    /// outside the engine's vim FSM) so `n` / `N` repeat the host's
    /// most recent commit with the right direction. Pass `None` /
    /// `true` to clear.
    pub fn set_last_search(&mut self, text: Option<String>, forward: bool) {
        self.vim.last_search = text;
        self.vim.last_search_forward = forward;
    }

    /// Start/end `(row, col)` of the active char-wise Visual selection
    /// (inclusive on both ends, positionally ordered). `None` when not
    /// in Visual mode.
    pub fn char_highlight(&self) -> Option<((usize, usize), (usize, usize))> {
        if self.vim_mode() != VimMode::Visual {
            return None;
        }
        let anchor = self.vim.visual_anchor;
        let cursor = self.cursor();
        let (start, end) = if anchor <= cursor {
            (anchor, cursor)
        } else {
            (cursor, anchor)
        };
        Some((start, end))
    }

    /// Top/bottom rows of the active VisualLine selection (inclusive).
    /// `None` when we're not in VisualLine mode.
    pub fn line_highlight(&self) -> Option<(usize, usize)> {
        if self.vim_mode() != VimMode::VisualLine {
            return None;
        }
        let anchor = self.vim.visual_line_anchor;
        let cursor = buf_cursor_row(&self.buffer);
        Some((anchor.min(cursor), anchor.max(cursor)))
    }

    pub fn block_highlight(&self) -> Option<(usize, usize, usize, usize)> {
        if self.vim_mode() != VimMode::VisualBlock {
            return None;
        }
        let (ar, ac) = self.vim.block_anchor;
        let cr = buf_cursor_row(&self.buffer);
        let cc = self.vim.block_vcol;
        let top = ar.min(cr);
        let bot = ar.max(cr);
        let left = ac.min(cc);
        let right = ac.max(cc);
        Some((top, bot, left, right))
    }

    /// Active selection in `hjkl_buffer::Selection` shape. `None` when
    /// not in a Visual mode. Phase 7d-i wiring — the host hands this
    /// straight to `BufferView` once render flips off textarea
    /// (Phase 7d-ii drops the `paint_*_overlay` calls on the same
    /// switch).
    pub fn buffer_selection(&self) -> Option<hjkl_buffer::Selection> {
        use hjkl_buffer::{Position, Selection};
        match self.vim_mode() {
            VimMode::Visual => {
                let (ar, ac) = self.vim.visual_anchor;
                let head = buf_cursor_pos(&self.buffer);
                Some(Selection::Char {
                    anchor: Position::new(ar, ac),
                    head,
                })
            }
            VimMode::VisualLine => {
                let anchor_row = self.vim.visual_line_anchor;
                let head_row = buf_cursor_row(&self.buffer);
                Some(Selection::Line {
                    anchor_row,
                    head_row,
                })
            }
            VimMode::VisualBlock => {
                let (ar, ac) = self.vim.block_anchor;
                let cr = buf_cursor_row(&self.buffer);
                let cc = self.vim.block_vcol;
                Some(Selection::Block {
                    anchor: Position::new(ar, ac),
                    head: Position::new(cr, cc),
                })
            }
            _ => None,
        }
    }

    /// Force back to normal mode (used when dismissing completions etc.)
    pub fn force_normal(&mut self) {
        self.vim.force_normal();
    }

    pub fn content(&self) -> String {
        let n = buf_row_count(&self.buffer);
        let mut s = String::new();
        for r in 0..n {
            if r > 0 {
                s.push('\n');
            }
            s.push_str(crate::types::Query::line(&self.buffer, r as u32));
        }
        s.push('\n');
        s
    }

    /// Same logical output as [`content`], but returns a cached
    /// `Arc<String>` so back-to-back reads within an un-mutated window
    /// are ref-count bumps instead of multi-MB joins. The cache is
    /// invalidated by every [`mark_content_dirty`] call.
    pub fn content_arc(&mut self) -> std::sync::Arc<String> {
        if let Some(arc) = &self.cached_content {
            return std::sync::Arc::clone(arc);
        }
        let arc = std::sync::Arc::new(self.content());
        self.cached_content = Some(std::sync::Arc::clone(&arc));
        arc
    }

    pub fn set_content(&mut self, text: &str) {
        let mut lines: Vec<String> = text.lines().map(|l| l.to_string()).collect();
        while lines.last().map(|l| l.is_empty()).unwrap_or(false) {
            lines.pop();
        }
        if lines.is_empty() {
            lines.push(String::new());
        }
        let _ = lines;
        crate::types::BufferEdit::replace_all(&mut self.buffer, text);
        self.undo_stack.clear();
        self.redo_stack.clear();
        // Whole-buffer replace supersedes any queued ContentEdits.
        self.pending_content_edits.clear();
        self.pending_content_reset = true;
        self.mark_content_dirty();
    }

    /// Whole-buffer replace that **preserves the undo history**.
    ///
    /// Equivalent to [`Editor::set_content`] but pushes the current buffer
    /// state onto the undo stack first, so a subsequent `u` walks back to
    /// the pre-replacement content. Use this for any operation the user
    /// expects to undo as a single step — e.g. external formatter output
    /// (`hjkl-mangler`) installed via the async [`crate::app::FormatWorker`].
    ///
    /// Like `push_undo`, this clears the redo stack (vim semantics: any
    /// new edit invalidates redo).
    pub fn set_content_undoable(&mut self, text: &str) {
        self.push_undo();
        let mut lines: Vec<String> = text.lines().map(|l| l.to_string()).collect();
        while lines.last().map(|l| l.is_empty()).unwrap_or(false) {
            lines.pop();
        }
        if lines.is_empty() {
            lines.push(String::new());
        }
        let _ = lines;
        crate::types::BufferEdit::replace_all(&mut self.buffer, text);
        // Whole-buffer replace supersedes any queued ContentEdits.
        self.pending_content_edits.clear();
        self.pending_content_reset = true;
        self.mark_content_dirty();
    }

    /// Drain the pending change log produced by buffer mutations.
    ///
    /// Returns a `Vec<EditOp>` covering edits applied since the last
    /// call. Empty when no edits ran. Pull-model, complementary to
    /// [`Editor::take_content_change`] which gives back the new full
    /// content.
    ///
    /// Mapping coverage:
    /// - InsertChar / InsertStr → exact `EditOp` with empty range +
    ///   replacement.
    /// - DeleteRange (`Char` kind) → exact range + empty replacement.
    /// - Replace → exact range + new replacement.
    /// - DeleteRange (`Line`/`Block`), JoinLines, SplitLines,
    ///   InsertBlock, DeleteBlockChunks → best-effort placeholder
    ///   covering the touched range. Hosts wanting per-cell deltas
    ///   should diff their own `lines()` snapshot.
    pub fn take_changes(&mut self) -> Vec<crate::types::Edit> {
        std::mem::take(&mut self.change_log)
    }

    /// Read the engine's current settings as a SPEC
    /// [`crate::types::Options`].
    ///
    /// Bridges between the legacy [`Settings`] (which carries fewer
    /// fields than SPEC) and the planned 0.1.0 trait surface. Fields
    /// not present in `Settings` fall back to vim defaults (e.g.,
    /// `expandtab=false`, `wrapscan=true`, `timeout_len=1000ms`).
    /// Once trait extraction lands, this becomes the canonical config
    /// reader and `Settings` retires.
    pub fn current_options(&self) -> crate::types::Options {
        crate::types::Options {
            shiftwidth: self.settings.shiftwidth as u32,
            tabstop: self.settings.tabstop as u32,
            softtabstop: self.settings.softtabstop as u32,
            textwidth: self.settings.textwidth as u32,
            expandtab: self.settings.expandtab,
            ignorecase: self.settings.ignore_case,
            smartcase: self.settings.smartcase,
            wrapscan: self.settings.wrapscan,
            wrap: match self.settings.wrap {
                hjkl_buffer::Wrap::None => crate::types::WrapMode::None,
                hjkl_buffer::Wrap::Char => crate::types::WrapMode::Char,
                hjkl_buffer::Wrap::Word => crate::types::WrapMode::Word,
            },
            readonly: self.settings.readonly,
            autoindent: self.settings.autoindent,
            smartindent: self.settings.smartindent,
            undo_levels: self.settings.undo_levels,
            undo_break_on_motion: self.settings.undo_break_on_motion,
            iskeyword: self.settings.iskeyword.clone(),
            timeout_len: self.settings.timeout_len,
            ..crate::types::Options::default()
        }
    }

    /// Apply a SPEC [`crate::types::Options`] to the engine's settings.
    /// Only the fields backed by today's [`Settings`] take effect;
    /// remaining options become live once trait extraction wires them
    /// through.
    pub fn apply_options(&mut self, opts: &crate::types::Options) {
        self.settings.shiftwidth = opts.shiftwidth as usize;
        self.settings.tabstop = opts.tabstop as usize;
        self.settings.softtabstop = opts.softtabstop as usize;
        self.settings.textwidth = opts.textwidth as usize;
        self.settings.expandtab = opts.expandtab;
        self.settings.ignore_case = opts.ignorecase;
        self.settings.smartcase = opts.smartcase;
        self.settings.wrapscan = opts.wrapscan;
        self.settings.wrap = match opts.wrap {
            crate::types::WrapMode::None => hjkl_buffer::Wrap::None,
            crate::types::WrapMode::Char => hjkl_buffer::Wrap::Char,
            crate::types::WrapMode::Word => hjkl_buffer::Wrap::Word,
        };
        self.settings.readonly = opts.readonly;
        self.settings.autoindent = opts.autoindent;
        self.settings.smartindent = opts.smartindent;
        self.settings.undo_levels = opts.undo_levels;
        self.settings.undo_break_on_motion = opts.undo_break_on_motion;
        self.set_iskeyword(opts.iskeyword.clone());
        self.settings.timeout_len = opts.timeout_len;
        self.settings.number = opts.number;
        self.settings.relativenumber = opts.relativenumber;
        self.settings.numberwidth = opts.numberwidth;
        self.settings.cursorline = opts.cursorline;
        self.settings.cursorcolumn = opts.cursorcolumn;
        self.settings.signcolumn = opts.signcolumn;
        self.settings.foldcolumn = opts.foldcolumn;
        self.settings.colorcolumn = opts.colorcolumn.clone();
    }

    /// Active visual selection as a SPEC [`crate::types::Highlight`]
    /// with [`crate::types::HighlightKind::Selection`].
    ///
    /// Returns `None` when the editor isn't in a Visual mode.
    /// Visual-line and visual-block selections collapse to the
    /// bounding char range of the selection — the SPEC `Selection`
    /// kind doesn't carry sub-line info today; hosts that need full
    /// line / block geometry continue to read [`buffer_selection`]
    /// (the legacy [`hjkl_buffer::Selection`] shape).
    pub fn selection_highlight(&self) -> Option<crate::types::Highlight> {
        use crate::types::{Highlight, HighlightKind, Pos};
        let sel = self.buffer_selection()?;
        let (start, end) = match sel {
            hjkl_buffer::Selection::Char { anchor, head } => {
                let a = (anchor.row, anchor.col);
                let h = (head.row, head.col);
                if a <= h { (a, h) } else { (h, a) }
            }
            hjkl_buffer::Selection::Line {
                anchor_row,
                head_row,
            } => {
                let (top, bot) = if anchor_row <= head_row {
                    (anchor_row, head_row)
                } else {
                    (head_row, anchor_row)
                };
                let last_col = buf_line(&self.buffer, bot).map(|l| l.len()).unwrap_or(0);
                ((top, 0), (bot, last_col))
            }
            hjkl_buffer::Selection::Block { anchor, head } => {
                let (top, bot) = if anchor.row <= head.row {
                    (anchor.row, head.row)
                } else {
                    (head.row, anchor.row)
                };
                let (left, right) = if anchor.col <= head.col {
                    (anchor.col, head.col)
                } else {
                    (head.col, anchor.col)
                };
                ((top, left), (bot, right))
            }
        };
        Some(Highlight {
            range: Pos {
                line: start.0 as u32,
                col: start.1 as u32,
            }..Pos {
                line: end.0 as u32,
                col: end.1 as u32,
            },
            kind: HighlightKind::Selection,
        })
    }

    /// SPEC-typed highlights for `line`.
    ///
    /// Two emission modes:
    ///
    /// - **IncSearch**: the user is typing a `/` or `?` prompt and
    ///   `Editor::search_prompt` is `Some`. Live-preview matches of
    ///   the in-flight pattern surface as
    ///   [`crate::types::HighlightKind::IncSearch`].
    /// - **SearchMatch**: the prompt has been committed (or absent)
    ///   and the buffer's armed pattern is non-empty. Matches surface
    ///   as [`crate::types::HighlightKind::SearchMatch`].
    ///
    /// Selection / MatchParen / Syntax(id) variants land once the
    /// trait extraction routes the FSM's selection set + the host's
    /// syntax pipeline through the [`crate::types::Host`] trait.
    ///
    /// Returns an empty vec when there is nothing to highlight or
    /// `line` is out of bounds.
    pub fn highlights_for_line(&mut self, line: u32) -> Vec<crate::types::Highlight> {
        use crate::types::{Highlight, HighlightKind, Pos};
        let row = line as usize;
        if row >= buf_row_count(&self.buffer) {
            return Vec::new();
        }

        // Live preview while the prompt is open beats the committed
        // pattern.
        if let Some(prompt) = self.search_prompt() {
            if prompt.text.is_empty() {
                return Vec::new();
            }
            let Ok(re) = regex::Regex::new(&prompt.text) else {
                return Vec::new();
            };
            let Some(haystack) = buf_line(&self.buffer, row) else {
                return Vec::new();
            };
            return re
                .find_iter(haystack)
                .map(|m| Highlight {
                    range: Pos {
                        line,
                        col: m.start() as u32,
                    }..Pos {
                        line,
                        col: m.end() as u32,
                    },
                    kind: HighlightKind::IncSearch,
                })
                .collect();
        }

        if self.search_state.pattern.is_none() {
            return Vec::new();
        }
        let dgen = crate::types::Query::dirty_gen(&self.buffer);
        crate::search::search_matches(&self.buffer, &mut self.search_state, dgen, row)
            .into_iter()
            .map(|(start, end)| Highlight {
                range: Pos {
                    line,
                    col: start as u32,
                }..Pos {
                    line,
                    col: end as u32,
                },
                kind: HighlightKind::SearchMatch,
            })
            .collect()
    }

    /// Build the engine's [`crate::types::RenderFrame`] for the
    /// current state. Hosts call this once per redraw and diff
    /// across frames.
    ///
    /// Coarse today — covers mode + cursor + cursor shape + viewport
    /// top + line count. SPEC-target fields (selections, highlights,
    /// command line, search prompt, status line) land once trait
    /// extraction routes them through `SelectionSet` and the
    /// `Highlight` pipeline.
    pub fn render_frame(&self) -> crate::types::RenderFrame {
        use crate::types::{CursorShape, RenderFrame, SnapshotMode};
        let (cursor_row, cursor_col) = self.cursor();
        let (mode, shape) = match self.vim_mode() {
            crate::VimMode::Normal => (SnapshotMode::Normal, CursorShape::Block),
            crate::VimMode::Insert => (SnapshotMode::Insert, CursorShape::Bar),
            crate::VimMode::Visual => (SnapshotMode::Visual, CursorShape::Block),
            crate::VimMode::VisualLine => (SnapshotMode::VisualLine, CursorShape::Block),
            crate::VimMode::VisualBlock => (SnapshotMode::VisualBlock, CursorShape::Block),
        };
        RenderFrame {
            mode,
            cursor_row: cursor_row as u32,
            cursor_col: cursor_col as u32,
            cursor_shape: shape,
            viewport_top: self.host.viewport().top_row as u32,
            line_count: crate::types::Query::line_count(&self.buffer),
        }
    }

    /// Capture the editor's coarse state into a serde-friendly
    /// [`crate::types::EditorSnapshot`].
    ///
    /// Today's snapshot covers mode, cursor, lines, viewport top.
    /// Registers, marks, jump list, undo tree, and full options arrive
    /// once phase 5 trait extraction lands the generic
    /// `Editor<B: Buffer, H: Host>` constructor — this method's surface
    /// stays stable; only the snapshot's internal fields grow.
    ///
    /// Distinct from the internal `snapshot` used by undo (which
    /// returns `(Vec<String>, (usize, usize))`); host-facing
    /// persistence goes through this one.
    pub fn take_snapshot(&self) -> crate::types::EditorSnapshot {
        use crate::types::{EditorSnapshot, SnapshotMode};
        let mode = match self.vim_mode() {
            crate::VimMode::Normal => SnapshotMode::Normal,
            crate::VimMode::Insert => SnapshotMode::Insert,
            crate::VimMode::Visual => SnapshotMode::Visual,
            crate::VimMode::VisualLine => SnapshotMode::VisualLine,
            crate::VimMode::VisualBlock => SnapshotMode::VisualBlock,
        };
        let cursor = self.cursor();
        let cursor = (cursor.0 as u32, cursor.1 as u32);
        let lines: Vec<String> = buf_lines_to_vec(&self.buffer);
        let viewport_top = self.host.viewport().top_row as u32;
        let marks = self
            .marks
            .iter()
            .map(|(c, (r, col))| (*c, (*r as u32, *col as u32)))
            .collect();
        EditorSnapshot {
            version: EditorSnapshot::VERSION,
            mode,
            cursor,
            lines,
            viewport_top,
            registers: self.registers.clone(),
            marks,
        }
    }

    /// Restore editor state from an [`EditorSnapshot`]. Returns
    /// [`crate::EngineError::SnapshotVersion`] if the snapshot's
    /// `version` doesn't match [`EditorSnapshot::VERSION`].
    ///
    /// Mode is best-effort: `SnapshotMode` only round-trips the
    /// status-line summary, not the full FSM state. Visual / Insert
    /// mode entry happens through synthetic key dispatch when needed.
    pub fn restore_snapshot(
        &mut self,
        snap: crate::types::EditorSnapshot,
    ) -> Result<(), crate::EngineError> {
        use crate::types::EditorSnapshot;
        if snap.version != EditorSnapshot::VERSION {
            return Err(crate::EngineError::SnapshotVersion(
                snap.version,
                EditorSnapshot::VERSION,
            ));
        }
        let text = snap.lines.join("\n");
        self.set_content(&text);
        self.jump_cursor(snap.cursor.0 as usize, snap.cursor.1 as usize);
        self.host.viewport_mut().top_row = snap.viewport_top as usize;
        self.registers = snap.registers;
        self.marks = snap
            .marks
            .into_iter()
            .map(|(c, (r, col))| (c, (r as usize, col as usize)))
            .collect();
        Ok(())
    }

    /// Install `text` as the pending yank buffer so the next `p`/`P` pastes
    /// it. Linewise is inferred from a trailing newline, matching how `yy`/`dd`
    /// shape their payload.
    pub fn seed_yank(&mut self, text: String) {
        let linewise = text.ends_with('\n');
        self.vim.yank_linewise = linewise;
        self.registers.unnamed = crate::registers::Slot { text, linewise };
    }

    /// Scroll the viewport down by `rows`. The cursor stays on its
    /// absolute line (vim convention) unless the scroll would take it
    /// off-screen — in that case it's clamped to the first row still
    /// visible.
    pub fn scroll_down(&mut self, rows: i16) {
        self.scroll_viewport(rows);
    }

    /// Scroll the viewport up by `rows`. Cursor stays unless it would
    /// fall off the bottom of the new viewport, then clamp to the
    /// bottom-most visible row.
    pub fn scroll_up(&mut self, rows: i16) {
        self.scroll_viewport(-rows);
    }

    /// Scroll the viewport right by `cols` columns. Only the horizontal
    /// offset (`top_col`) moves — the cursor is NOT adjusted (matches
    /// vim's `zl` behaviour for horizontal scroll without wrap).
    pub fn scroll_right(&mut self, cols: i16) {
        let vp = self.host.viewport_mut();
        let cols_i = cols as isize;
        let new_top = (vp.top_col as isize + cols_i).max(0) as usize;
        vp.top_col = new_top;
    }

    /// Scroll the viewport left by `cols` columns. Delegates to
    /// `scroll_right` with a negated argument so the floor-at-zero
    /// clamp is shared.
    pub fn scroll_left(&mut self, cols: i16) {
        self.scroll_right(-cols);
    }

    /// Vim's `scrolloff` default — keep the cursor at least this many
    /// rows away from the top / bottom edge of the viewport while
    /// scrolling. Collapses to `height / 2` for tiny viewports.
    const SCROLLOFF: usize = 5;

    /// Scroll the viewport so the cursor stays at least `SCROLLOFF`
    /// rows from each edge. Replaces the bare
    /// `Buffer::ensure_cursor_visible` call at end-of-step so motions
    /// don't park the cursor on the very last visible row.
    pub fn ensure_cursor_in_scrolloff(&mut self) {
        let height = self.viewport_height.load(Ordering::Relaxed) as usize;
        if height == 0 {
            // 0.0.42 (Patch C-δ.7): viewport math lifted onto engine
            // free fns over `B: Query [+ Cursor]` + `&dyn FoldProvider`.
            // Disjoint-field borrow split: `self.buffer` (immutable via
            // `folds` snapshot + cursor) and `self.host` (mutable
            // viewport ref) live on distinct struct fields, so one
            // statement satisfies the borrow checker.
            let folds = crate::buffer_impl::BufferFoldProvider::new(&self.buffer);
            crate::viewport_math::ensure_cursor_visible(
                &self.buffer,
                &folds,
                self.host.viewport_mut(),
            );
            return;
        }
        // Cap margin at (height - 1) / 2 so the upper + lower bands
        // can't overlap on tiny windows (margin=5 + height=10 would
        // otherwise produce contradictory clamp ranges).
        let margin = Self::SCROLLOFF.min(height.saturating_sub(1) / 2);
        // Soft-wrap path: scrolloff math runs in *screen rows*, not
        // doc rows, since a wrapped doc row spans many visual lines.
        if !matches!(self.host.viewport().wrap, hjkl_buffer::Wrap::None) {
            self.ensure_scrolloff_wrap(height, margin);
            return;
        }
        let cursor_row = buf_cursor_row(&self.buffer);
        let last_row = buf_row_count(&self.buffer).saturating_sub(1);
        let v = self.host.viewport_mut();
        // Top edge: cursor_row should sit at >= top_row + margin.
        if cursor_row < v.top_row + margin {
            v.top_row = cursor_row.saturating_sub(margin);
        }
        // Bottom edge: cursor_row should sit at <= top_row + height - 1 - margin.
        let max_bottom = height.saturating_sub(1).saturating_sub(margin);
        if cursor_row > v.top_row + max_bottom {
            v.top_row = cursor_row.saturating_sub(max_bottom);
        }
        // Clamp top_row so we never scroll past the buffer's bottom.
        let max_top = last_row.saturating_sub(height.saturating_sub(1));
        if v.top_row > max_top {
            v.top_row = max_top;
        }
        // Defer to Buffer for column-side scroll (no scrolloff for
        // horizontal scrolling — vim default `sidescrolloff = 0`).
        let cursor = buf_cursor_pos(&self.buffer);
        self.host.viewport_mut().ensure_visible(cursor);
    }

    /// Soft-wrap-aware scrolloff. Walks `top_row` one visible doc row
    /// at a time so the cursor's *screen* row stays inside
    /// `[margin, height - 1 - margin]`, then clamps `top_row` so the
    /// buffer's bottom never leaves blank rows below it.
    fn ensure_scrolloff_wrap(&mut self, height: usize, margin: usize) {
        let cursor_row = buf_cursor_row(&self.buffer);
        // Step 1 — cursor above viewport: snap top to cursor row,
        // then we'll fix up the margin below.
        if cursor_row < self.host.viewport().top_row {
            let v = self.host.viewport_mut();
            v.top_row = cursor_row;
            v.top_col = 0;
        }
        // Step 2 — push top forward until cursor's screen row is
        // within the bottom margin (`csr <= height - 1 - margin`).
        // 0.0.33 (Patch C-γ): fold-iteration goes through the
        // [`crate::types::FoldProvider`] surface via
        // [`crate::buffer_impl::BufferFoldProvider`]. 0.0.34 (Patch
        // C-δ.1): `cursor_screen_row` / `max_top_for_height` now take
        // a `&Viewport` parameter; the host owns the viewport, so the
        // disjoint `(self.host, self.buffer)` borrows split cleanly.
        let max_csr = height.saturating_sub(1).saturating_sub(margin);
        loop {
            let folds = crate::buffer_impl::BufferFoldProvider::new(&self.buffer);
            let csr =
                crate::viewport_math::cursor_screen_row(&self.buffer, &folds, self.host.viewport())
                    .unwrap_or(0);
            if csr <= max_csr {
                break;
            }
            let top = self.host.viewport().top_row;
            let row_count = buf_row_count(&self.buffer);
            let next = {
                let folds = crate::buffer_impl::BufferFoldProvider::new(&self.buffer);
                <crate::buffer_impl::BufferFoldProvider<'_> as crate::types::FoldProvider>::next_visible_row(&folds, top, row_count)
            };
            let Some(next) = next else {
                break;
            };
            // Don't walk past the cursor's row.
            if next > cursor_row {
                self.host.viewport_mut().top_row = cursor_row;
                break;
            }
            self.host.viewport_mut().top_row = next;
        }
        // Step 3 — pull top backward until cursor's screen row is
        // past the top margin (`csr >= margin`).
        loop {
            let folds = crate::buffer_impl::BufferFoldProvider::new(&self.buffer);
            let csr =
                crate::viewport_math::cursor_screen_row(&self.buffer, &folds, self.host.viewport())
                    .unwrap_or(0);
            if csr >= margin {
                break;
            }
            let top = self.host.viewport().top_row;
            let prev = {
                let folds = crate::buffer_impl::BufferFoldProvider::new(&self.buffer);
                <crate::buffer_impl::BufferFoldProvider<'_> as crate::types::FoldProvider>::prev_visible_row(&folds, top)
            };
            let Some(prev) = prev else {
                break;
            };
            self.host.viewport_mut().top_row = prev;
        }
        // Step 4 — clamp top so the buffer's bottom doesn't leave
        // blank rows below it. `max_top_for_height` walks segments
        // backward from the last row until it accumulates `height`
        // screen rows.
        let max_top = {
            let folds = crate::buffer_impl::BufferFoldProvider::new(&self.buffer);
            crate::viewport_math::max_top_for_height(
                &self.buffer,
                &folds,
                self.host.viewport(),
                height,
            )
        };
        if self.host.viewport().top_row > max_top {
            self.host.viewport_mut().top_row = max_top;
        }
        self.host.viewport_mut().top_col = 0;
    }

    fn scroll_viewport(&mut self, delta: i16) {
        if delta == 0 {
            return;
        }
        // Bump the host viewport's top within bounds.
        let total_rows = buf_row_count(&self.buffer) as isize;
        let height = self.viewport_height.load(Ordering::Relaxed) as usize;
        let cur_top = self.host.viewport().top_row as isize;
        let new_top = (cur_top + delta as isize)
            .max(0)
            .min((total_rows - 1).max(0)) as usize;
        self.host.viewport_mut().top_row = new_top;
        // Mirror to textarea so its viewport reads (still consumed by
        // a couple of helpers) stay accurate.
        let _ = cur_top;
        if height == 0 {
            return;
        }
        // Apply scrolloff: keep the cursor at least SCROLLOFF rows
        // from the visible viewport edges.
        let (cursor_row, cursor_col) = buf_cursor_rc(&self.buffer);
        let margin = Self::SCROLLOFF.min(height / 2);
        let min_row = new_top + margin;
        let max_row = new_top + height.saturating_sub(1).saturating_sub(margin);
        let target_row = cursor_row.clamp(min_row, max_row.max(min_row));
        if target_row != cursor_row {
            let line_len = buf_line(&self.buffer, target_row)
                .map(|l| l.chars().count())
                .unwrap_or(0);
            let target_col = cursor_col.min(line_len.saturating_sub(1));
            buf_set_cursor_rc(&mut self.buffer, target_row, target_col);
        }
    }

    pub fn goto_line(&mut self, line: usize) {
        let row = line.saturating_sub(1);
        let max = buf_row_count(&self.buffer).saturating_sub(1);
        let target = row.min(max);
        buf_set_cursor_rc(&mut self.buffer, target, 0);
        // Vim: `:N` / `+N` jump scrolls the viewport too — without this
        // the cursor lands off-screen and the user has to scroll
        // manually to see it.
        self.ensure_cursor_in_scrolloff();
    }

    /// Scroll so the cursor row lands at the given viewport position:
    /// `Center` → middle row, `Top` → first row, `Bottom` → last row.
    /// Cursor stays on its absolute line; only the viewport moves.
    pub(super) fn scroll_cursor_to(&mut self, pos: CursorScrollTarget) {
        let height = self.viewport_height.load(Ordering::Relaxed) as usize;
        if height == 0 {
            return;
        }
        let cur_row = buf_cursor_row(&self.buffer);
        let cur_top = self.host.viewport().top_row;
        // Scrolloff awareness: `zt` lands the cursor at the top edge
        // of the viable area (top + margin), `zb` at the bottom edge
        // (top + height - 1 - margin). Match the cap used by
        // `ensure_cursor_in_scrolloff` so contradictory bounds are
        // impossible on tiny viewports.
        let margin = Self::SCROLLOFF.min(height.saturating_sub(1) / 2);
        let new_top = match pos {
            CursorScrollTarget::Center => cur_row.saturating_sub(height / 2),
            CursorScrollTarget::Top => cur_row.saturating_sub(margin),
            CursorScrollTarget::Bottom => {
                cur_row.saturating_sub(height.saturating_sub(1).saturating_sub(margin))
            }
        };
        if new_top == cur_top {
            return;
        }
        self.host.viewport_mut().top_row = new_top;
    }

    /// Jump the cursor to the given 1-based line/column, clamped to the document.
    pub fn jump_to(&mut self, line: usize, col: usize) {
        let r = line.saturating_sub(1);
        let max_row = buf_row_count(&self.buffer).saturating_sub(1);
        let r = r.min(max_row);
        let line_len = buf_line(&self.buffer, r)
            .map(|l| l.chars().count())
            .unwrap_or(0);
        let c = col.saturating_sub(1).min(line_len);
        buf_set_cursor_rc(&mut self.buffer, r, c);
    }

    // ── Host-agnostic doc-coord mouse primitives (Phase 1 of issue #114) ─────
    //
    // These primitives operate on document (row, col) coordinates that the HOST
    // computes from its own layout knowledge (cell geometry for the TUI host,
    // pixel geometry for the future GUI host). The engine has no u16 terminal
    // assumption here — it just moves the cursor in doc-space.

    /// Set the cursor to the given doc-space `(row, col)`, clamped to the
    /// document bounds. Hosts use this for programmatic cursor placement and
    /// as the building block for the mouse-click path.
    ///
    /// `col` may equal `line.chars().count()` (Insert-mode "one past end"
    /// position); values beyond that are clamped to `char_count`.
    pub fn set_cursor_doc(&mut self, row: usize, col: usize) {
        let max_row = buf_row_count(&self.buffer).saturating_sub(1);
        let r = row.min(max_row);
        let line_len = buf_line(&self.buffer, r)
            .map(|l| l.chars().count())
            .unwrap_or(0);
        let c = col.min(line_len);
        buf_set_cursor_rc(&mut self.buffer, r, c);
    }

    /// Handle a left-button click at doc-space `(row, col)`.
    ///
    /// Exits Visual mode if active, breaks the insert-mode undo group (Vim
    /// parity for `undo_break_on_motion`), then moves the cursor. The host
    /// performs cell→doc or pixel→doc translation before calling this.
    ///
    /// Mode-aware EOL clamp (neovim parity): in Normal / Visual modes the
    /// cursor lives on chars and never on the implicit `\n` — `col` is
    /// capped at `line.chars().count().saturating_sub(1)`. Insert mode
    /// allows the one-past-EOL insert position (`col == chars().count()`).
    ///
    /// Resets `sticky_col` to the clicked column so the next `j`/`k`
    /// motion uses the clicked column as the intended visual column
    /// (otherwise the cursor would snap back to the keyboard-tracked
    /// column on the first vertical motion after a click).
    pub fn mouse_click_doc(&mut self, row: usize, col: usize) {
        if self.vim.is_visual() {
            self.vim.force_normal();
        }
        // Mouse-position click counts as a motion — break the active
        // insert-mode undo group when the toggle is on (vim parity).
        crate::vim::break_undo_group_in_insert(self);

        let max_row = buf_row_count(&self.buffer).saturating_sub(1);
        let r = row.min(max_row);
        let line_len = buf_line(&self.buffer, r)
            .map(|l| l.chars().count())
            .unwrap_or(0);
        let cap = if self.vim.current_mode == crate::VimMode::Insert {
            line_len
        } else {
            line_len.saturating_sub(1)
        };
        let c = col.min(cap);
        buf_set_cursor_rc(&mut self.buffer, r, c);
        self.sticky_col = Some(c);
    }

    /// Begin a mouse-drag selection: anchor at the current cursor and enter
    /// Visual-char mode. Idempotent if already in Visual-char mode.
    pub fn mouse_begin_drag(&mut self) {
        if !self.vim.is_visual_char() {
            vim::enter_visual_char_bridge(self);
        }
    }

    /// Extend an in-progress mouse drag to doc-space `(row, col)`.
    ///
    /// Moves the live cursor; the Visual anchor stays where
    /// [`Editor::mouse_begin_drag`] set it. Call after the host has
    /// translated the drag position to doc coordinates.
    pub fn mouse_extend_drag_doc(&mut self, row: usize, col: usize) {
        self.set_cursor_doc(row, col);
    }

    pub fn insert_str(&mut self, text: &str) {
        let pos = crate::types::Cursor::cursor(&self.buffer);
        crate::types::BufferEdit::insert_at(&mut self.buffer, pos, text);
        self.push_buffer_content_to_textarea();
        self.mark_content_dirty();
    }

    pub fn accept_completion(&mut self, completion: &str) {
        use crate::types::{BufferEdit, Cursor as CursorTrait, Pos};
        let cursor_pos = CursorTrait::cursor(&self.buffer);
        let cursor_row = cursor_pos.line as usize;
        let cursor_col = cursor_pos.col as usize;
        let line = buf_line(&self.buffer, cursor_row).unwrap_or("").to_string();
        let chars: Vec<char> = line.chars().collect();
        let prefix_len = chars[..cursor_col.min(chars.len())]
            .iter()
            .rev()
            .take_while(|c| c.is_alphanumeric() || **c == '_')
            .count();
        if prefix_len > 0 {
            let start = Pos {
                line: cursor_row as u32,
                col: (cursor_col - prefix_len) as u32,
            };
            BufferEdit::delete_range(&mut self.buffer, start..cursor_pos);
        }
        let cursor = CursorTrait::cursor(&self.buffer);
        BufferEdit::insert_at(&mut self.buffer, cursor, completion);
        self.push_buffer_content_to_textarea();
        self.mark_content_dirty();
    }

    pub(super) fn snapshot(&self) -> (Vec<String>, (usize, usize)) {
        let rc = buf_cursor_rc(&self.buffer);
        (buf_lines_to_vec(&self.buffer), rc)
    }

    /// Walk one step back through the undo history. Equivalent to the
    /// user pressing `u` in normal mode. Drains the most recent undo
    /// entry and pushes it onto the redo stack.
    pub fn undo(&mut self) {
        crate::vim::do_undo(self);
    }

    /// Walk one step forward through the redo history. Equivalent to
    /// `<C-r>` in normal mode.
    pub fn redo(&mut self) {
        crate::vim::do_redo(self);
    }

    /// Snapshot current buffer state onto the undo stack and clear
    /// the redo stack. Bounded by `settings.undo_levels` — older
    /// entries pruned. Call before any group of buffer mutations the
    /// user might want to undo as a single step.
    pub fn push_undo(&mut self) {
        let snap = self.snapshot();
        self.undo_stack.push(snap);
        self.cap_undo();
        self.redo_stack.clear();
    }

    /// Trim the undo stack down to `settings.undo_levels`, dropping
    /// the oldest entries. `undo_levels == 0` is treated as
    /// "unlimited" (vim's 0-means-no-undo semantics intentionally
    /// skipped — guarding with `> 0` is one line shorter than gating
    /// the cap path with an explicit zero-check above the call site).
    pub(crate) fn cap_undo(&mut self) {
        let cap = self.settings.undo_levels as usize;
        if cap > 0 && self.undo_stack.len() > cap {
            let diff = self.undo_stack.len() - cap;
            self.undo_stack.drain(..diff);
        }
    }

    /// Test-only accessor for the undo stack length.
    #[doc(hidden)]
    pub fn undo_stack_len(&self) -> usize {
        self.undo_stack.len()
    }

    /// Replace the buffer with `lines` joined by `\n` and set the
    /// cursor to `cursor`. Used by undo / `:e!` / snapshot restore
    /// paths. Marks the editor dirty.
    pub fn restore(&mut self, lines: Vec<String>, cursor: (usize, usize)) {
        let text = lines.join("\n");
        crate::types::BufferEdit::replace_all(&mut self.buffer, &text);
        buf_set_cursor_rc(&mut self.buffer, cursor.0, cursor.1);
        // Bulk replace — supersedes any queued ContentEdits.
        self.pending_content_edits.clear();
        self.pending_content_reset = true;
        self.mark_content_dirty();
    }

    /// Returns true if the key was consumed by the editor.
    /// Replace the char under the cursor with `ch`, `count` times. Matches
    /// vim `r<x>` semantics: cursor ends on the last replaced char, undo
    /// snapshot taken once at start. Promoted to public surface in 0.5.5
    /// so hjkl-vim's pending-state reducer can dispatch `Replace` without
    /// re-entering the FSM.
    pub fn replace_char_at(&mut self, ch: char, count: usize) {
        vim::replace_char(self, ch, count);
    }

    /// Apply vim's `f<x>` / `F<x>` / `t<x>` / `T<x>` motion. Moves the cursor
    /// to the `count`-th occurrence of `ch` on the current line, respecting
    /// `forward` (direction) and `till` (stop one char before target).
    /// Records `last_find` so `;` / `,` repeat work.
    ///
    /// No-op if the target char isn't on the current line within range.
    /// Cursor / scroll / sticky-col semantics match `f<x>` via `execute_motion`.
    pub fn find_char(&mut self, ch: char, forward: bool, till: bool, count: usize) {
        vim::apply_find_char(self, ch, forward, till, count.max(1));
    }

    /// Apply the g-chord effect for `g<ch>` with a pre-captured `count`.
    /// Mirrors the full `handle_after_g` dispatch table — `gg`, `gj`, `gk`,
    /// `gv`, `gU` / `gu` / `g~` (→ operator-pending), `gi`, `g*`, `g#`, etc.
    ///
    /// Promoted to public surface in 0.5.10 so hjkl-vim's
    /// `PendingState::AfterG` reducer can dispatch `AfterGChord` without
    /// re-entering the engine FSM.
    pub fn after_g(&mut self, ch: char, count: usize) {
        vim::apply_after_g(self, ch, count);
    }

    /// Apply the z-chord effect for `z<ch>` with a pre-captured `count`.
    /// Mirrors the full `handle_after_z` dispatch table — `zz` / `zt` / `zb`
    /// (scroll-cursor), `zo` / `zc` / `za` / `zR` / `zM` / `zE` / `zd`
    /// (fold ops), and `zf` (fold-add over visual selection or → op-pending).
    ///
    /// Promoted to public surface in 0.5.11 so hjkl-vim's
    /// `PendingState::AfterZ` reducer can dispatch `AfterZChord` without
    /// re-entering the engine FSM.
    pub fn after_z(&mut self, ch: char, count: usize) {
        vim::apply_after_z(self, ch, count);
    }

    /// Apply an operator over a single-key motion. `op` is the engine `Operator`
    /// and `motion_key` is the raw character (e.g. `'w'`, `'$'`, `'G'`). The
    /// engine resolves the char to a [`vim::Motion`] via `parse_motion`, applies
    /// the vim quirks (`cw` → `ce`, `cW` → `cE`, `FindRepeat` → stored find),
    /// then calls `apply_op_with_motion`. `total_count` is already the product of
    /// the prefix count and any inner count accumulated by the reducer.
    ///
    /// No-op when `motion_key` does not map to a known motion (engine silently
    /// cancels the operator, matching vim's behaviour on unknown motions).
    ///
    /// Promoted to the public surface in 0.5.12 so the hjkl-vim
    /// `PendingState::AfterOp` reducer can dispatch `ApplyOpMotion` without
    /// re-entering the engine FSM.
    pub fn apply_op_motion(
        &mut self,
        op: crate::vim::Operator,
        motion_key: char,
        total_count: usize,
    ) {
        vim::apply_op_motion_key(self, op, motion_key, total_count);
    }

    /// Apply a doubled-letter line op (`dd` / `yy` / `cc` / `>>` / `<<`).
    /// `total_count` is the product of prefix count and inner count.
    ///
    /// Promoted to the public surface in 0.5.12 so the hjkl-vim
    /// `PendingState::AfterOp` reducer can dispatch `ApplyOpDouble` without
    /// re-entering the engine FSM.
    pub fn apply_op_double(&mut self, op: crate::vim::Operator, total_count: usize) {
        vim::apply_op_double(self, op, total_count);
    }

    /// Apply an operator over a find motion (`df<x>` / `dF<x>` / `dt<x>` /
    /// `dT<x>`). Builds `Motion::Find { ch, forward, till }`, applies it via
    /// `apply_op_with_motion`, records `last_find` for `;` / `,` repeat, and
    /// updates `last_change` when `op` is Change (for dot-repeat).
    ///
    /// `total_count` is the product of prefix count and any inner count
    /// accumulated by the reducer — already folded at transition time.
    ///
    /// Promoted to the public surface in 0.5.14 so the hjkl-vim
    /// `PendingState::OpFind` reducer can dispatch `ApplyOpFind` without
    /// re-entering the engine FSM. `handle_op_find_target` (used by the
    /// chord-init op path) delegates here to avoid logic duplication.
    pub fn apply_op_find(
        &mut self,
        op: crate::vim::Operator,
        ch: char,
        forward: bool,
        till: bool,
        total_count: usize,
    ) {
        vim::apply_op_find_motion(self, op, ch, forward, till, total_count);
    }

    /// Apply an operator over a text-object range (`diw` / `daw` / `di"` etc.).
    /// Maps `ch` to a `TextObject` per the standard vim table, calls
    /// `apply_op_with_text_object`, and records `last_change` when `op` is
    /// Change (dot-repeat). Unknown `ch` values are silently ignored (no-op),
    /// matching the engine FSM's behaviour on unrecognised text-object chars.
    ///
    /// `total_count` is accepted for API symmetry with `apply_op_motion` /
    /// `apply_op_find` but is currently unused — text objects don't repeat in
    /// vim's current grammar. Kept for future-proofing.
    ///
    /// Promoted to the public surface in 0.5.15 so the hjkl-vim
    /// `PendingState::OpTextObj` reducer can dispatch `ApplyOpTextObj` without
    /// re-entering the engine FSM. `handle_text_object` (chord-init op path)
    /// delegates to the shared `apply_op_text_obj_inner` helper to avoid logic
    /// duplication.
    pub fn apply_op_text_obj(
        &mut self,
        op: crate::vim::Operator,
        ch: char,
        inner: bool,
        total_count: usize,
    ) {
        vim::apply_op_text_obj_inner(self, op, ch, inner, total_count);
    }

    /// Apply an operator over a g-chord motion or case-op linewise form
    /// (`dgg` / `dge` / `dgE` / `dgj` / `dgk` / `gUgU` etc.).
    ///
    /// - If `op` is Uppercase/Lowercase/ToggleCase and `ch` matches the op's
    ///   letter (`U`/`u`/`~`), executes the line op (linewise form).
    /// - Otherwise maps `ch` to a motion:
    ///   - `'g'` → `Motion::FileTop` (gg)
    ///   - `'e'` → `Motion::WordEndBack` (ge)
    ///   - `'E'` → `Motion::BigWordEndBack` (gE)
    ///   - `'j'` → `Motion::ScreenDown` (gj)
    ///   - `'k'` → `Motion::ScreenUp` (gk)
    ///   - unknown → no-op (silently ignored, matching engine FSM behaviour)
    /// - Updates `last_change` for dot-repeat when `op` is a change operator.
    ///
    /// `total_count` is the already-folded product of prefix and inner counts.
    ///
    /// Promoted to the public surface in 0.5.16 so the hjkl-vim
    /// `PendingState::OpG` reducer can dispatch `ApplyOpG` without
    /// re-entering the engine FSM. `handle_op_after_g` (chord-init op path)
    /// delegates to the shared `apply_op_g_inner` helper to avoid logic
    /// duplication.
    pub fn apply_op_g(&mut self, op: crate::vim::Operator, ch: char, total_count: usize) {
        vim::apply_op_g_inner(self, op, ch, total_count);
    }

    // ─── Range-query helpers for partial-format dispatch (#119) ─────────────

    /// Dry-run `motion_key` and return `(min_row, max_row)` between the cursor
    /// row and the motion's target row. Used by the app layer to compute the
    /// [`hjkl_mangler::RangeSpec`] for `=<motion>` before submitting the async
    /// format job.
    ///
    /// Returns `None` when `motion_key` does not map to a known motion (same
    /// condition that makes `apply_op_motion` a no-op).
    ///
    /// The cursor is restored to its original position after the probe —
    /// the buffer content is not touched.
    pub fn range_for_op_motion(
        &mut self,
        motion_key: char,
        total_count: usize,
    ) -> Option<(usize, usize)> {
        let start = self.cursor();
        // Reuse the same logic as apply_op_motion_key but only read the
        // target row — we parse the motion, apply it to move the cursor,
        // then immediately restore.
        let input = crate::input::Input {
            key: crate::input::Key::Char(motion_key),
            ctrl: false,
            alt: false,
            shift: false,
        };
        let motion = vim::parse_motion(&input)?;
        // Resolve FindRepeat and cw/cW quirks just like apply_op_motion_key.
        let motion = match motion {
            vim::Motion::FindRepeat { reverse } => match self.vim.last_find {
                Some((ch, forward, till)) => vim::Motion::Find {
                    ch,
                    forward: if reverse { !forward } else { forward },
                    till,
                },
                None => return None,
            },
            m => m,
        };
        vim::apply_motion_cursor_ctx(self, &motion, total_count, true);
        let end = self.cursor();
        // Restore cursor.
        buf_set_cursor_rc(&mut self.buffer, start.0, start.1);
        let (r0, r1) = (start.0.min(end.0), start.0.max(end.0));
        Some((r0, r1))
    }

    /// Dry-run a `g`-prefixed motion and return `(min_row, max_row)`. Used for
    /// `=gg` / `=gj` etc. Returns `None` for unknown `ch` values or case-op
    /// linewise forms that don't map to a row range.
    ///
    /// The cursor is restored after the probe.
    pub fn range_for_op_g(&mut self, ch: char, total_count: usize) -> Option<(usize, usize)> {
        let start = self.cursor();
        let motion = match ch {
            'g' => vim::Motion::FileTop,
            'e' => vim::Motion::WordEndBack,
            'E' => vim::Motion::BigWordEndBack,
            'j' => vim::Motion::ScreenDown,
            'k' => vim::Motion::ScreenUp,
            _ => return None,
        };
        vim::apply_motion_cursor_ctx(self, &motion, total_count, true);
        let end = self.cursor();
        buf_set_cursor_rc(&mut self.buffer, start.0, start.1);
        let (r0, r1) = (start.0.min(end.0), start.0.max(end.0));
        Some((r0, r1))
    }

    /// Dry-run a text-object lookup and return `(min_row, max_row)` for the
    /// matched region. Returns `None` when `ch` is not a known text-object
    /// kind or the text object could not be resolved (e.g. no enclosing bracket).
    ///
    /// The buffer is not mutated.
    pub fn range_for_op_text_obj(
        &self,
        ch: char,
        inner: bool,
        _total_count: usize,
    ) -> Option<(usize, usize)> {
        let obj = match ch {
            'w' => vim::TextObject::Word { big: false },
            'W' => vim::TextObject::Word { big: true },
            '"' | '\'' | '`' => vim::TextObject::Quote(ch),
            '(' | ')' | 'b' => vim::TextObject::Bracket('('),
            '[' | ']' => vim::TextObject::Bracket('['),
            '{' | '}' | 'B' => vim::TextObject::Bracket('{'),
            '<' | '>' => vim::TextObject::Bracket('<'),
            'p' => vim::TextObject::Paragraph,
            't' => vim::TextObject::XmlTag,
            's' => vim::TextObject::Sentence,
            _ => return None,
        };
        let (start, end, _kind) = vim::text_object_range(self, obj, inner)?;
        let (r0, r1) = (start.0.min(end.0), start.0.max(end.0));
        Some((r0, r1))
    }

    // ─── Phase 4a: pub range-mutation primitives (hjkl#70) ──────────────────
    //
    // These do not consume input — the caller (hjkl-vim's visual-mode operator
    // path, chunk 4e) has already resolved the range from the visual selection
    // before calling in. Normal-mode op dispatch continues to use
    // `apply_op_motion` / `apply_op_double` / `apply_op_find` / `apply_op_text_obj`.

    /// Delete the region `[start, end)` and stash the removed text in
    /// `register`. `'"'` selects the unnamed register (vim default); `'a'`–`'z'`
    /// select named registers.
    ///
    /// Pure range-mutation primitive — does not consume input. Called by
    /// hjkl-vim's visual-mode operator path which has already resolved the range
    /// from the visual selection.
    ///
    /// Promoted to the public surface in 0.6.7 for Phase 4 visual-mode op
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn delete_range(
        &mut self,
        start: (usize, usize),
        end: (usize, usize),
        kind: crate::vim::RangeKind,
        register: char,
    ) {
        vim::delete_range_bridge(self, start, end, kind, register);
    }

    /// Yank (copy) the region `[start, end)` into `register` without mutating
    /// the buffer. `'"'` selects the unnamed register; `'0'` the yank-only
    /// register; `'a'`–`'z'` select named registers.
    ///
    /// Pure range-mutation primitive — does not consume input. Called by
    /// hjkl-vim's visual-mode operator path which has already resolved the range
    /// from the visual selection.
    ///
    /// Promoted to the public surface in 0.6.7 for Phase 4 visual-mode op
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn yank_range(
        &mut self,
        start: (usize, usize),
        end: (usize, usize),
        kind: crate::vim::RangeKind,
        register: char,
    ) {
        vim::yank_range_bridge(self, start, end, kind, register);
    }

    /// Delete the region `[start, end)` and transition to Insert mode (vim `c`
    /// operator). The deleted text is stashed in `register`. On return the
    /// editor is in Insert mode; the caller must not issue further normal-mode
    /// ops until the insert session ends.
    ///
    /// Pure range-mutation primitive — does not consume input. Called by
    /// hjkl-vim's visual-mode operator path which has already resolved the range
    /// from the visual selection.
    ///
    /// Promoted to the public surface in 0.6.7 for Phase 4 visual-mode op
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn change_range(
        &mut self,
        start: (usize, usize),
        end: (usize, usize),
        kind: crate::vim::RangeKind,
        register: char,
    ) {
        vim::change_range_bridge(self, start, end, kind, register);
    }

    /// Indent (`count > 0`) or outdent (`count < 0`) the row span
    /// `[start.0, end.0]`. Column components are ignored — indent is always
    /// linewise. `shiftwidth` overrides the editor's configured shiftwidth for
    /// this call; pass `0` to use the current editor setting. `count == 0` is a
    /// no-op.
    ///
    /// Pure range-mutation primitive — does not consume input. Called by
    /// hjkl-vim's visual-mode operator path which has already resolved the range
    /// from the visual selection.
    ///
    /// Promoted to the public surface in 0.6.7 for Phase 4 visual-mode op
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn indent_range(
        &mut self,
        start: (usize, usize),
        end: (usize, usize),
        count: i32,
        shiftwidth: u32,
    ) {
        vim::indent_range_bridge(self, start, end, count, shiftwidth);
    }

    /// Apply a case transformation (`Operator::Uppercase` /
    /// `Operator::Lowercase` / `Operator::ToggleCase`) to the region
    /// `[start, end)`. Other `Operator` variants are silently ignored (no-op).
    /// Yanks registers are left untouched — vim's case operators do not write
    /// to registers.
    ///
    /// Pure range-mutation primitive — does not consume input. Called by
    /// hjkl-vim's visual-mode operator path which has already resolved the range
    /// from the visual selection.
    ///
    /// Promoted to the public surface in 0.6.7 for Phase 4 visual-mode op
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn case_range(
        &mut self,
        start: (usize, usize),
        end: (usize, usize),
        kind: crate::vim::RangeKind,
        op: crate::vim::Operator,
    ) {
        vim::case_range_bridge(self, start, end, kind, op);
    }

    // ─── Phase 4e: pub block-shape range-mutation primitives (hjkl#70) ──────
    //
    // Rectangular VisualBlock operations. `top_row`/`bot_row` are inclusive
    // line indices; `left_col`/`right_col` are inclusive char-column bounds.
    // Ragged-edge handling (short lines not reaching `right_col`) matches the
    // engine FSM's `apply_block_operator` path — short lines lose only the
    // chars that exist.
    //
    // `register` is the target register; `'"'` selects the unnamed register.

    /// Delete a rectangular VisualBlock selection. `top_row` / `bot_row` are
    /// inclusive line bounds; `left_col` / `right_col` are inclusive column
    /// bounds at the visual (display) column level. Ragged-edge handling
    /// matches engine FSM's VisualBlock op behavior — short lines that don't
    /// reach `right_col` lose only the chars that exist.
    ///
    /// `register` honors the user's pending register selection.
    ///
    /// Promoted in 0.6.X for Phase 4e block-op grammar migration.
    pub fn delete_block(
        &mut self,
        top_row: usize,
        bot_row: usize,
        left_col: usize,
        right_col: usize,
        register: char,
    ) {
        vim::delete_block_bridge(self, top_row, bot_row, left_col, right_col, register);
    }

    /// Yank a rectangular VisualBlock selection into `register` without
    /// mutating the buffer. `'"'` selects the unnamed register.
    ///
    /// Promoted in 0.6.X for Phase 4e block-op grammar migration.
    pub fn yank_block(
        &mut self,
        top_row: usize,
        bot_row: usize,
        left_col: usize,
        right_col: usize,
        register: char,
    ) {
        vim::yank_block_bridge(self, top_row, bot_row, left_col, right_col, register);
    }

    /// Delete a rectangular VisualBlock selection and enter Insert mode (`c`
    /// operator). The deleted text is stashed in `register`. Mode is Insert
    /// on return; the caller must not issue further normal-mode ops until the
    /// insert session ends.
    ///
    /// Promoted in 0.6.X for Phase 4e block-op grammar migration.
    pub fn change_block(
        &mut self,
        top_row: usize,
        bot_row: usize,
        left_col: usize,
        right_col: usize,
        register: char,
    ) {
        vim::change_block_bridge(self, top_row, bot_row, left_col, right_col, register);
    }

    /// Indent (`count > 0`) or outdent (`count < 0`) rows `top_row..=bot_row`.
    /// Column bounds are ignored — vim's block indent is always linewise.
    /// `count == 0` is a no-op.
    ///
    /// Promoted in 0.6.X for Phase 4e block-op grammar migration.
    pub fn indent_block(
        &mut self,
        top_row: usize,
        bot_row: usize,
        _left_col: usize,
        _right_col: usize,
        count: i32,
    ) {
        vim::indent_block_bridge(self, top_row, bot_row, count);
    }

    /// Auto-indent (v1 dumb shiftwidth) the row span `[start.0, end.0]`.
    /// Column components are ignored — auto-indent is always linewise.
    ///
    /// The algorithm is a naive bracket-depth counter: it scans the buffer from
    /// row 0 to compute the correct depth at `start.0`, then for each line in
    /// the target range strips existing leading whitespace and prepends
    /// `depth × indent_unit` where `indent_unit` is `"\t"` when `expandtab`
    /// is `false`, or `" " × shiftwidth` when `expandtab` is `true`. Lines
    /// whose first non-whitespace character is a close bracket (`}`, `)`, `]`)
    /// get one fewer indent level. Empty / whitespace-only lines are cleared.
    ///
    /// After the operation the cursor lands on the first non-whitespace
    /// character of `start_row` (vim parity for `==`).
    ///
    /// **v1 limitation**: the bracket scan does not detect brackets inside
    /// string literals or comments. Code such as `let s = "{";` will increment
    /// the depth counter even though the brace is not a structural opener.
    /// Tree-sitter / LSP indentation is deferred to a follow-up.
    pub fn auto_indent_range(&mut self, start: (usize, usize), end: (usize, usize)) {
        vim::auto_indent_range_bridge(self, start, end);
    }

    /// Drain the row range set by the most recent auto-indent operation.
    ///
    /// Returns `Some((top_row, bot_row))` (inclusive) on the first call after
    /// an `=` / `==` / `=G` / Visual-`=` operator, then clears the stored
    /// value so a subsequent call returns `None`. The host (e.g. `apps/hjkl`)
    /// uses this to arm a brief visual flash over the reindented rows.
    pub fn take_last_indent_range(&mut self) -> Option<(usize, usize)> {
        self.last_indent_range.take()
    }

    // ─── Phase 4b: pub text-object resolution (hjkl#70) ─────────────────────
    //
    // Pure functions — no cursor mutation, no mode change, no register write.
    // Each method delegates to `vim::text_object_*_bridge`, which in turn calls
    // the existing `word_text_object` private resolver in vim.rs.
    //
    // Called by hjkl-vim's `OpTextObj` reducer (chunk 4e) to resolve the range
    // before invoking a range-mutation primitive (`delete_range`, etc.).
    //
    // Return value: `Some((start, end))` where both positions are `(row, col)`
    // byte-column pairs and `end` is *exclusive* (one past the last byte to act
    // on), matching the convention used by `delete_range` / `yank_range` / etc.
    // Returns `None` when the cursor is on an empty line or the resolver cannot
    // find a word boundary.

    /// Resolve the range of `iw` (inner word) at the current cursor position.
    ///
    /// An inner word is the contiguous run of keyword characters (or punctuation
    /// characters if the cursor is on punctuation) under the cursor, without any
    /// surrounding whitespace. Whitespace-only positions return `None`.
    ///
    /// Pure function — does not move the cursor or change any editor state.
    /// Called by hjkl-vim's `OpTextObj` reducer to resolve the range before
    /// invoking a range-mutation primitive (`delete_range`, etc.).
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4b text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_inner_word(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_inner_word_bridge(self)
    }

    /// Resolve the range of `aw` (around word) at the current cursor position.
    ///
    /// Like `iw` but extends the range to include trailing whitespace after the
    /// word. If no trailing whitespace exists, leading whitespace before the word
    /// is absorbed instead (vim `:help text-objects` behaviour).
    ///
    /// Pure function — does not move the cursor or change any editor state.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4b text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_around_word(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_around_word_bridge(self)
    }

    /// Resolve the range of `iW` (inner WORD) at the current cursor position.
    ///
    /// A WORD is any contiguous run of non-whitespace characters — punctuation
    /// is not treated as a word boundary. Returns the span of the WORD under the
    /// cursor, without surrounding whitespace.
    ///
    /// Pure function — does not move the cursor or change any editor state.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4b text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_inner_big_word(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_inner_big_word_bridge(self)
    }

    /// Resolve the range of `aW` (around WORD) at the current cursor position.
    ///
    /// Like `iW` but extends the range to include trailing whitespace after the
    /// WORD. If no trailing whitespace exists, leading whitespace before the WORD
    /// is absorbed instead.
    ///
    /// Pure function — does not move the cursor or change any editor state.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4b text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_around_big_word(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_around_big_word_bridge(self)
    }

    // ─── Phase 4c: pub text-object resolution — quote + bracket (hjkl#70) ───
    //
    // Pure functions — no cursor mutation, no mode change, no register write.
    // Each method delegates to `vim::text_object_*_bridge`, which in turn calls
    // the existing private resolvers (`quote_text_object`, `bracket_text_object`)
    // in vim.rs.
    //
    // Quote methods take the quote char itself (`'"'`, `'\''`, `` '`' ``).
    // Bracket methods take the OPEN bracket char (`'('`, `'{'`, `'['`, `'<'`);
    // close-bracket variants (`)`, `}`, `]`, `>`) are NOT accepted here — the
    // hjkl-vim grammar layer normalises close→open before calling these methods.
    //
    // Return value: `Some((start, end))` where both positions are `(row, col)`
    // byte-column pairs and `end` is *exclusive* (one past the last byte to act
    // on), matching the convention used by `delete_range` / `yank_range` / etc.
    // `bracket_text_object` internally distinguishes Linewise vs Exclusive
    // ranges for multi-line pairs; that tag is stripped here — callers receive
    // the same flat shape as all other text-object resolvers.

    /// Resolve the range of `i<quote>` (inner quote) at the cursor position.
    ///
    /// `quote` is one of `'"'`, `'\''`, or `` '`' ``. Returns `None` when the
    /// cursor's line contains fewer than two occurrences of `quote`, or when no
    /// matching pair can be found around or ahead of the cursor.
    ///
    /// Inner range excludes the quote characters themselves.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4c text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_inner_quote(&self, quote: char) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_inner_quote_bridge(self, quote)
    }

    /// Resolve the range of `a<quote>` (around quote) at the cursor position.
    ///
    /// Like `i<quote>` but includes the quote characters themselves plus
    /// surrounding whitespace on one side: trailing whitespace after the closing
    /// quote if any exists; otherwise leading whitespace before the opening
    /// quote. This matches vim `:help text-objects` behaviour.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4c text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_around_quote(
        &self,
        quote: char,
    ) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_around_quote_bridge(self, quote)
    }

    /// Resolve the range of `i<bracket>` (inner bracket pair) at the cursor.
    ///
    /// `open` must be one of `'('`, `'{'`, `'['`, `'<'` — the corresponding
    /// close bracket is derived automatically. Close-bracket chars (`)`, `}`,
    /// `]`, `>`) are **not** accepted; hjkl-vim normalises close→open before
    /// calling this method. Returns `None` when no enclosing pair is found.
    ///
    /// The cursor may be anywhere inside the pair or on a bracket character
    /// itself. When not inside any pair the resolver falls back to a forward
    /// scan (targets.vim-style: `ci(` works when the cursor is before `(`).
    ///
    /// Inner range excludes the bracket characters. Multi-line pairs are
    /// supported; the returned range spans the full content between the
    /// brackets.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// `ib` / `iB` aliases live in the hjkl-vim grammar layer and are not
    /// handled here.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4c text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_inner_bracket(
        &self,
        open: char,
    ) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_inner_bracket_bridge(self, open)
    }

    /// Resolve the range of `a<bracket>` (around bracket pair) at the cursor.
    ///
    /// Like `i<bracket>` but includes the bracket characters themselves.
    /// `open` must be one of `'('`, `'{'`, `'['`, `'<'`.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// `aB` alias lives in the hjkl-vim grammar layer and is not handled here.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4c text-object grammar
    /// migration (kryptic-sh/hjkl#70).
    pub fn text_object_around_bracket(
        &self,
        open: char,
    ) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_around_bracket_bridge(self, open)
    }

    // ── Sentence text objects (is / as) ───────────────────────────────────

    /// Resolve `is` (inner sentence) at the cursor position.
    ///
    /// Returns the range of the current sentence, excluding trailing
    /// whitespace. Sentence boundaries follow vim's `is` semantics (period /
    /// `?` / `!` followed by whitespace or end-of-paragraph).
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4d text-object
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn text_object_inner_sentence(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_inner_sentence_bridge(self)
    }

    /// Resolve `as` (around sentence) at the cursor position.
    ///
    /// Like `is` but includes trailing whitespace after the sentence
    /// terminator.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4d text-object
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn text_object_around_sentence(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_around_sentence_bridge(self)
    }

    // ── Paragraph text objects (ip / ap) ──────────────────────────────────

    /// Resolve `ip` (inner paragraph) at the cursor position.
    ///
    /// A paragraph is a block of non-blank lines bounded by blank lines or
    /// buffer edges. Returns `None` when the cursor is on a blank line.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4d text-object
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn text_object_inner_paragraph(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_inner_paragraph_bridge(self)
    }

    /// Resolve `ap` (around paragraph) at the cursor position.
    ///
    /// Like `ip` but includes one trailing blank line when present.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4d text-object
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn text_object_around_paragraph(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_around_paragraph_bridge(self)
    }

    // ── Tag text objects (it / at) ────────────────────────────────────────

    /// Resolve `it` (inner tag) at the cursor position.
    ///
    /// Matches XML/HTML-style `<tag>...</tag>` pairs. Returns the range of
    /// inner content between the open and close tags (excluding the tags
    /// themselves).
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4d text-object
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn text_object_inner_tag(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_inner_tag_bridge(self)
    }

    /// Resolve `at` (around tag) at the cursor position.
    ///
    /// Like `it` but includes the open and close tag delimiters themselves.
    ///
    /// Pure function — no cursor mutation.
    ///
    /// Promoted to the public surface in 0.6.X for Phase 4d text-object
    /// grammar migration (kryptic-sh/hjkl#70).
    pub fn text_object_around_tag(&self) -> Option<((usize, usize), (usize, usize))> {
        vim::text_object_around_tag_bridge(self)
    }

    /// Execute a named cursor motion `kind` repeated `count` times.
    ///
    /// Maps the keymap-layer `crate::MotionKind` to the engine's internal
    /// motion primitives, bypassing the engine FSM. Identical cursor semantics
    /// to the FSM path — sticky column, scroll sync, and big-jump tracking are
    /// all applied via `vim::execute_motion` (for Down/Up) or the same helpers
    /// used by the FSM arms.
    ///
    /// Introduced in 0.6.1 as the host entry point for Phase 3a of
    /// kryptic-sh/hjkl#69: the app keymap dispatches `AppAction::Motion` and
    /// calls this method rather than re-entering the engine FSM.
    ///
    /// Engine FSM arms for `h`/`j`/`k`/`l`/`<BS>`/`<Space>`/`+`/`-` remain
    /// intact for macro-replay coverage (macros re-feed raw keys through the
    /// FSM). This method is the keymap / controller path only.
    pub fn apply_motion(&mut self, kind: crate::MotionKind, count: usize) {
        vim::apply_motion_kind(self, kind, count);
    }

    /// Set `vim.pending_register` to `Some(reg)` if `reg` is a valid register
    /// selector (`a`–`z`, `A`–`Z`, `0`–`9`, `"`, `+`, `*`, `_`). Invalid
    /// chars are silently ignored (no-op), matching the engine FSM's
    /// `handle_select_register` behaviour.
    ///
    /// Promoted to the public surface in 0.5.17 so the hjkl-vim
    /// `PendingState::SelectRegister` reducer can dispatch `SetPendingRegister`
    /// without re-entering the engine FSM. `handle_select_register` (engine FSM
    /// path for macro-replay / defensive coverage) delegates here to avoid
    /// logic duplication.
    pub fn set_pending_register(&mut self, reg: char) {
        if reg.is_ascii_alphanumeric() || matches!(reg, '"' | '+' | '*' | '_') {
            self.vim.pending_register = Some(reg);
        }
        // Invalid chars silently no-op (matches engine FSM behavior).
    }

    /// Record a mark named `ch` at the current cursor position.
    ///
    /// Validates `ch` (must be `a`–`z` or `A`–`Z` to match vim's mark-name
    /// rules). Invalid chars are silently ignored (no-op), matching the engine
    /// FSM's `handle_set_mark` behaviour.
    ///
    /// Promoted to the public surface in 0.6.7 so the hjkl-vim
    /// `PendingState::SetMark` reducer can dispatch `EngineCmd::SetMark`
    /// without re-entering the engine FSM. `handle_set_mark` delegates here.
    pub fn set_mark_at_cursor(&mut self, ch: char) {
        vim::set_mark_at_cursor(self, ch);
    }

    /// `.` dot-repeat: replay the last buffered change at the current cursor.
    /// `count` scales repeats (e.g. `3.` runs the last change 3 times). When
    /// `count` is 0, defaults to 1. No-op when no change has been buffered yet.
    ///
    /// Storage of `LastChange` stays inside engine for now; Phase 5c of
    /// kryptic-sh/hjkl#71 just lifts the `.` chord binding into the app
    /// keymap so the engine FSM `.` arm is no longer the entry point. Engine
    /// FSM `.` arm stays for macro-replay defensive coverage.
    pub fn replay_last_change(&mut self, count: usize) {
        vim::replay_last_change(self, count);
    }

    /// Jump to the mark named `ch`, linewise (row only; col snaps to first
    /// non-blank). Pushes the pre-jump position onto the jumplist if the
    /// cursor actually moved.
    ///
    /// Accepts the same mark chars as vim's `'<ch>` command: `a`–`z`,
    /// `A`–`Z`, `'`/`` ` `` (jump-back peek), `.` (last edit), and the
    /// special auto-marks `[`, `]`, `<`, `>`. Unset marks and invalid chars
    /// are silently ignored (no-op), matching the engine FSM's
    /// `handle_goto_mark` behaviour.
    ///
    /// Promoted to the public surface in 0.6.7 so the hjkl-vim
    /// `PendingState::GotoMarkLine` reducer can dispatch
    /// `EngineCmd::GotoMarkLine` without re-entering the engine FSM.
    pub fn goto_mark_line(&mut self, ch: char) {
        vim::goto_mark(self, ch, true);
    }

    /// Jump to the mark named `ch`, charwise (exact row + col). Pushes the
    /// pre-jump position onto the jumplist if the cursor actually moved.
    ///
    /// Accepts the same mark chars as vim's `` `<ch> `` command: `a`–`z`,
    /// `A`–`Z`, `'`/`` ` `` (jump-back peek), `.` (last edit), and the
    /// special auto-marks `[`, `]`, `<`, `>`. Unset marks and invalid chars
    /// are silently ignored (no-op), matching the engine FSM's
    /// `handle_goto_mark` behaviour.
    ///
    /// Promoted to the public surface in 0.6.7 so the hjkl-vim
    /// `PendingState::GotoMarkChar` reducer can dispatch
    /// `EngineCmd::GotoMarkChar` without re-entering the engine FSM.
    pub fn goto_mark_char(&mut self, ch: char) {
        vim::goto_mark(self, ch, false);
    }

    // ── Macro controller API (Phase 5b) ──────────────────────────────────────

    /// Begin recording keystrokes into register `reg`. The caller (app) is
    /// responsible for stopping the recording via `stop_macro_record` when the
    /// user presses bare `q`.
    ///
    /// - Uppercase `reg` (e.g. `'A'`) appends to the existing lowercase
    ///   recording by pre-seeding `recording_keys` with the decoded text of the
    ///   matching lowercase register, matching vim's capital-register append
    ///   semantics.
    /// - Lowercase `reg` clears `recording_keys` (fresh recording).
    /// - Invalid chars (non-alphabetic, non-digit) are silently ignored.
    ///
    /// Promoted to the public surface in Phase 5b so the app's
    /// `route_chord_key` can start a recording without re-entering the engine
    /// FSM. `handle_record_macro_target` (engine FSM path for macro-replay
    /// defensive coverage) continues to use the same logic via delegation.
    pub fn start_macro_record(&mut self, reg: char) {
        if !(reg.is_ascii_alphabetic() || reg.is_ascii_digit()) {
            return;
        }
        self.vim.recording_macro = Some(reg);
        if reg.is_ascii_uppercase() {
            // Seed recording_keys with the existing lowercase register's text
            // decoded back to inputs so capital-register append continues from
            // where the previous recording left off.
            let lower = reg.to_ascii_lowercase();
            let text = self
                .registers
                .read(lower)
                .map(|s| s.text.clone())
                .unwrap_or_default();
            self.vim.recording_keys = crate::input::decode_macro(&text);
        } else {
            self.vim.recording_keys.clear();
        }
    }

    /// Finalize the active recording: encode `recording_keys` as text and write
    /// to the matching (lowercase) named register. Clears both `recording_macro`
    /// and `recording_keys`. No-ops if no recording is active.
    ///
    /// Promoted to the public surface in Phase 5b so the app's `QChord` action
    /// can stop a recording when the user presses bare `q` without re-entering
    /// the engine FSM.
    pub fn stop_macro_record(&mut self) {
        let Some(reg) = self.vim.recording_macro.take() else {
            return;
        };
        let keys = std::mem::take(&mut self.vim.recording_keys);
        let text = crate::input::encode_macro(&keys);
        self.set_named_register_text(reg.to_ascii_lowercase(), text);
    }

    /// Returns `true` while a `q{reg}` recording is in progress.
    /// Hosts use this to show a "recording @r" status indicator and to decide
    /// whether bare `q` should stop the recording or open the `RecordMacroTarget`
    /// chord.
    pub fn is_recording_macro(&self) -> bool {
        self.vim.recording_macro.is_some()
    }

    /// Returns `true` while a macro is being replayed. The app sets this flag
    /// (via `play_macro`) and clears it (via `end_macro_replay`) around the
    /// re-feed loop so the recorder hook can skip double-capture.
    pub fn is_replaying_macro(&self) -> bool {
        self.vim.replaying_macro
    }

    /// Decode the named register `reg` into a `Vec<crate::input::Input>` and
    /// prepare for replay, returning the inputs the app should re-feed through
    /// `route_chord_key`.
    ///
    /// Resolves `reg`:
    /// - `'@'` → use `vim.last_macro`; returns empty vec if none.
    /// - Any other char → lowercase it, read the register, decode.
    ///
    /// Side-effects:
    /// - Sets `vim.last_macro` to the resolved register.
    /// - Sets `vim.replaying_macro = true` so the recorder hook skips during
    ///   replay. The app calls `end_macro_replay` after the loop finishes.
    ///
    /// Returns an empty vec (and no side-effects for `'@'`) if the register is
    /// unset or empty.
    pub fn play_macro(&mut self, reg: char, count: usize) -> Vec<crate::input::Input> {
        let resolved = if reg == '@' {
            match self.vim.last_macro {
                Some(r) => r,
                None => return vec![],
            }
        } else {
            reg.to_ascii_lowercase()
        };
        let text = match self.registers.read(resolved) {
            Some(slot) if !slot.text.is_empty() => slot.text.clone(),
            _ => return vec![],
        };
        let keys = crate::input::decode_macro(&text);
        self.vim.last_macro = Some(resolved);
        self.vim.replaying_macro = true;
        // Multiply by count (minimum 1).
        keys.repeat(count.max(1))
    }

    /// Clear the `replaying_macro` flag. Called by the app after the
    /// re-feed loop in the `PlayMacro` commit arm completes (or aborts).
    pub fn end_macro_replay(&mut self) {
        self.vim.replaying_macro = false;
    }

    /// Append `input` to the active recording (`recording_keys`) if and only
    /// if a recording is in progress AND we are not currently replaying.
    /// Called by the app's `route_chord_key` recorder hook so that user
    /// keystrokes captured through the app-level chord path are recorded
    /// (rather than relying solely on the engine FSM's in-step hook).
    pub fn record_input(&mut self, input: crate::input::Input) {
        if self.vim.recording_macro.is_some() && !self.vim.replaying_macro {
            self.vim.recording_keys.push(input);
        }
    }

    // ─── Phase 6.1: public insert-mode primitives (kryptic-sh/hjkl#87) ────────
    //
    // Each method is the publicly callable form of one insert-mode action.
    // All logic lives in the corresponding `vim::*_bridge` free function;
    // these methods are thin delegators so the public surface stays on `Editor`.
    //
    // Invariants (enforced by the bridge fns):
    //   - Buffer mutations go through `mutate_edit` (dirty/undo/change-list).
    //   - Navigation keys call `break_undo_group_in_insert` when the FSM did.
    //   - `push_buffer_cursor_to_textarea` is called after every mutation
    //     (currently a no-op, kept for migration hygiene).

    /// Insert `ch` at the cursor. In Replace mode, overstrike the cell under
    /// the cursor instead of inserting; at end-of-line, always appends. With
    /// `smartindent` on, closing brackets (`}`/`)`/`]`) trigger one-unit
    /// dedent on an otherwise-whitespace line.
    ///
    /// Callers must ensure the editor is in Insert or Replace mode before
    /// calling this method.
    pub fn insert_char(&mut self, ch: char) {
        let mutated = vim::insert_char_bridge(self, ch);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Insert a newline at the cursor, applying autoindent / smartindent to
    /// prefix the new line with the appropriate leading whitespace.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_newline(&mut self) {
        let mutated = vim::insert_newline_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Insert a tab character (or spaces up to the next `softtabstop` boundary
    /// when `expandtab` is set).
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_tab(&mut self) {
        let mutated = vim::insert_tab_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Delete the character before the cursor (Backspace). With `softtabstop`
    /// active, deletes the entire soft-tab run at an aligned boundary. Joins
    /// with the previous line when at column 0.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_backspace(&mut self) {
        let mutated = vim::insert_backspace_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Delete the character under the cursor (Delete key). Joins with the
    /// next line when at end-of-line.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_delete(&mut self) {
        let mutated = vim::insert_delete_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Move the cursor one step in `dir` (arrow key), breaking the undo group
    /// per `undo_break_on_motion`.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_arrow(&mut self, dir: vim::InsertDir) {
        vim::insert_arrow_bridge(self, dir);
        let (row, _) = self.cursor();
        self.vim.widen_insert_row(row);
    }

    /// Move the cursor to the start of the current line (Home key), breaking
    /// the undo group.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_home(&mut self) {
        vim::insert_home_bridge(self);
        let (row, _) = self.cursor();
        self.vim.widen_insert_row(row);
    }

    /// Move the cursor to the end of the current line (End key), breaking the
    /// undo group.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_end(&mut self) {
        vim::insert_end_bridge(self);
        let (row, _) = self.cursor();
        self.vim.widen_insert_row(row);
    }

    /// Scroll up one full viewport height (PageUp), moving the cursor with it.
    /// `viewport_h` is the current viewport height in rows; pass
    /// `self.viewport_height_value()` if the stored value is current.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_pageup(&mut self, viewport_h: u16) {
        vim::insert_pageup_bridge(self, viewport_h);
        let (row, _) = self.cursor();
        self.vim.widen_insert_row(row);
    }

    /// Scroll down one full viewport height (PageDown), moving the cursor with
    /// it. `viewport_h` is the current viewport height in rows.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_pagedown(&mut self, viewport_h: u16) {
        vim::insert_pagedown_bridge(self, viewport_h);
        let (row, _) = self.cursor();
        self.vim.widen_insert_row(row);
    }

    /// Delete from the cursor back to the start of the previous word (`Ctrl-W`).
    /// At column 0, joins with the previous line (vim `b`-motion semantics).
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_ctrl_w(&mut self) {
        let mutated = vim::insert_ctrl_w_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Delete from the cursor back to the start of the current line (`Ctrl-U`).
    /// No-op when already at column 0.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_ctrl_u(&mut self) {
        let mutated = vim::insert_ctrl_u_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Delete one character backwards (`Ctrl-H`) — alias for Backspace in
    /// insert mode. Joins with the previous line when at col 0.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_ctrl_h(&mut self) {
        let mutated = vim::insert_ctrl_h_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Enter "one-shot normal" mode (`Ctrl-O`): suspend insert for the next
    /// complete normal-mode command, then return to insert automatically.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_ctrl_o_arm(&mut self) {
        vim::insert_ctrl_o_bridge(self);
    }

    /// Arm the register-paste selector (`Ctrl-R`). The next call to
    /// `insert_paste_register(reg)` will insert the register contents.
    /// Alternatively, feeding a `Key::Char(c)` through the FSM will consume
    /// the armed state and paste register `c`.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_ctrl_r_arm(&mut self) {
        vim::insert_ctrl_r_bridge(self);
    }

    /// Indent the current line by one `shiftwidth` and shift the cursor right
    /// by the same amount (`Ctrl-T`).
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_ctrl_t(&mut self) {
        let mutated = vim::insert_ctrl_t_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Outdent the current line by up to one `shiftwidth` and shift the cursor
    /// left by the amount stripped (`Ctrl-D`).
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_ctrl_d(&mut self) {
        let mutated = vim::insert_ctrl_d_bridge(self);
        if mutated {
            self.mark_content_dirty();
            let (row, _) = self.cursor();
            self.vim.widen_insert_row(row);
        }
    }

    /// Paste the contents of register `reg` at the cursor (the commit arm of
    /// `Ctrl-R {reg}`). Unknown or empty registers are a no-op.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn insert_paste_register(&mut self, reg: char) {
        vim::insert_paste_register_bridge(self, reg);
        let (row, _) = self.cursor();
        self.vim.widen_insert_row(row);
    }

    /// Exit insert mode to Normal: finish the insert session, step the cursor
    /// one cell left (vim convention on Esc), record the `gi` target position,
    /// and update the sticky column.
    ///
    /// Callers must ensure the editor is in Insert mode before calling.
    pub fn leave_insert_to_normal(&mut self) {
        vim::leave_insert_to_normal_bridge(self);
    }

    // ── Phase 6.2: normal-mode primitive controller methods ───────────────────
    //
    // Each method is a thin wrapper around a `pub(crate) fn *_bridge` in
    // `vim.rs` following the same pattern as Phase 6.1. The FSM's
    // `handle_normal_only` now calls the same bridges so both paths are
    // identical. See kryptic-sh/hjkl#88 for the full promotion plan.

    /// `i` — transition to Insert mode at the current cursor position.
    /// `count` is stored in the insert session and replayed by dot-repeat
    /// as a repeat count on the inserted text.
    pub fn enter_insert_i(&mut self, count: usize) {
        vim::enter_insert_i_bridge(self, count);
    }

    /// `I` — move to the first non-blank character on the line, then
    /// transition to Insert mode. `count` is stored for dot-repeat.
    pub fn enter_insert_shift_i(&mut self, count: usize) {
        vim::enter_insert_shift_i_bridge(self, count);
    }

    /// `a` — advance the cursor one cell past the current position, then
    /// transition to Insert mode (append). `count` is stored for dot-repeat.
    pub fn enter_insert_a(&mut self, count: usize) {
        vim::enter_insert_a_bridge(self, count);
    }

    /// `A` — move the cursor to the end of the line, then transition to
    /// Insert mode (append at end). `count` is stored for dot-repeat.
    pub fn enter_insert_shift_a(&mut self, count: usize) {
        vim::enter_insert_shift_a_bridge(self, count);
    }

    /// `o` — open a new line below the current line with smart-indent, then
    /// transition to Insert mode. `count` is stored for dot-repeat replay.
    pub fn open_line_below(&mut self, count: usize) {
        vim::open_line_below_bridge(self, count);
    }

    /// `O` — open a new line above the current line with smart-indent, then
    /// transition to Insert mode. `count` is stored for dot-repeat replay.
    pub fn open_line_above(&mut self, count: usize) {
        vim::open_line_above_bridge(self, count);
    }

    /// `R` — enter Replace mode: subsequent typed characters overstrike the
    /// cell under the cursor rather than inserting. `count` is for replay.
    pub fn enter_replace_mode(&mut self, count: usize) {
        vim::enter_replace_mode_bridge(self, count);
    }

    /// `x` — delete `count` characters forward from the cursor and write them
    /// to the unnamed register. No-op on an empty line. Records for `.`.
    pub fn delete_char_forward(&mut self, count: usize) {
        vim::delete_char_forward_bridge(self, count);
    }

    /// `X` — delete `count` characters backward from the cursor and write
    /// them to the unnamed register. No-op at column 0. Records for `.`.
    pub fn delete_char_backward(&mut self, count: usize) {
        vim::delete_char_backward_bridge(self, count);
    }

    /// `s` — substitute `count` characters: delete them (writing to the
    /// unnamed register) then enter Insert mode. Equivalent to `cl`.
    /// Records as `OpMotion { Change, Right }` for dot-repeat.
    pub fn substitute_char(&mut self, count: usize) {
        vim::substitute_char_bridge(self, count);
    }

    /// `S` — substitute the current line: wipe its contents (writing to the
    /// unnamed register) then enter Insert mode. Equivalent to `cc`.
    /// Records as `LineOp { Change }` for dot-repeat.
    pub fn substitute_line(&mut self, count: usize) {
        vim::substitute_line_bridge(self, count);
    }

    /// `D` — delete from the cursor to end-of-line, writing to the unnamed
    /// register. The cursor parks on the new last character. Records for `.`.
    pub fn delete_to_eol(&mut self) {
        vim::delete_to_eol_bridge(self);
    }

    /// `C` — change from the cursor to end-of-line: delete to EOL then enter
    /// Insert mode. Equivalent to `c$`. Does not record its own `last_change`
    /// (the insert session records `DeleteToEol` on exit, like `c` motions).
    pub fn change_to_eol(&mut self) {
        vim::change_to_eol_bridge(self);
    }

    /// `Y` — yank from the cursor to end-of-line into the unnamed register.
    /// Vim 8 default: equivalent to `y$`. `count` multiplies the motion.
    pub fn yank_to_eol(&mut self, count: usize) {
        vim::yank_to_eol_bridge(self, count);
    }

    /// `J` — join `count` lines (default 2) onto the current line, inserting
    /// a single space between each non-empty pair. Records for dot-repeat.
    pub fn join_line(&mut self, count: usize) {
        vim::join_line_bridge(self, count);
    }

    /// `~` — toggle the case of `count` characters from the cursor, advancing
    /// right after each toggle. Records `ToggleCase` for dot-repeat.
    pub fn toggle_case_at_cursor(&mut self, count: usize) {
        vim::toggle_case_at_cursor_bridge(self, count);
    }

    /// `p` — paste the unnamed register (or the register selected via `"r`)
    /// after the cursor. Linewise content opens a new line below; charwise
    /// content is inserted inline. Records `Paste { before: false }` for `.`.
    pub fn paste_after(&mut self, count: usize) {
        vim::paste_after_bridge(self, count);
    }

    /// `P` — paste the unnamed register (or the `"r` register) before the
    /// cursor. Linewise content opens a new line above; charwise is inline.
    /// Records `Paste { before: true }` for dot-repeat.
    pub fn paste_before(&mut self, count: usize) {
        vim::paste_before_bridge(self, count);
    }

    /// `<C-o>` — jump back `count` entries in the jumplist, saving the
    /// current position on the forward stack so `<C-i>` can return.
    pub fn jump_back(&mut self, count: usize) {
        vim::jump_back_bridge(self, count);
    }

    /// `<C-i>` / `Tab` — redo `count` entries on the forward jumplist stack,
    /// saving the current position on the backward stack.
    pub fn jump_forward(&mut self, count: usize) {
        vim::jump_forward_bridge(self, count);
    }

    /// `<C-f>` / `<C-b>` — scroll the cursor by one full viewport height
    /// (height − 2 rows, preserving two-line overlap). `count` multiplies.
    /// `dir = Down` for `<C-f>`, `Up` for `<C-b>`.
    pub fn scroll_full_page(&mut self, dir: vim::ScrollDir, count: usize) {
        vim::scroll_full_page_bridge(self, dir, count);
    }

    /// `<C-d>` / `<C-u>` — scroll the cursor by half the viewport height.
    /// `count` multiplies the step. `dir = Down` for `<C-d>`, `Up` for `<C-u>`.
    pub fn scroll_half_page(&mut self, dir: vim::ScrollDir, count: usize) {
        vim::scroll_half_page_bridge(self, dir, count);
    }

    /// `<C-e>` / `<C-y>` — scroll the viewport `count` lines without moving
    /// the cursor (cursor is clamped to the new visible region if necessary).
    /// `dir = Down` for `<C-e>` (scroll text up), `Up` for `<C-y>`.
    pub fn scroll_line(&mut self, dir: vim::ScrollDir, count: usize) {
        vim::scroll_line_bridge(self, dir, count);
    }

    /// `n` — repeat the last `/` or `?` search `count` times in its original
    /// direction. `forward = true` keeps the direction; `false` inverts (`N`).
    pub fn search_repeat(&mut self, forward: bool, count: usize) {
        vim::search_repeat_bridge(self, forward, count);
    }

    /// `*` / `#` / `g*` / `g#` — search for the word under the cursor.
    /// `forward` chooses direction; `whole_word` wraps the pattern in `\b`
    /// anchors (true for `*` / `#`, false for `g*` / `g#`). `count` repeats.
    pub fn word_search(&mut self, forward: bool, whole_word: bool, count: usize) {
        vim::word_search_bridge(self, forward, whole_word, count);
    }

    // ── Phase 6.3: visual-mode primitive controller methods ──────────────────
    //
    // Each method is a thin wrapper around a `pub(crate) fn *_bridge` in
    // `vim.rs` following the same pattern as Phase 6.1 / 6.2. Both the FSM
    // and these wrappers write `current_mode` so `vim_mode()` returns correct
    // values regardless of which path performed the transition.
    // See kryptic-sh/hjkl#89 for the full promotion plan.

    /// `v` from Normal — enter charwise Visual mode, anchoring the selection
    /// at the current cursor position.
    pub fn enter_visual_char(&mut self) {
        vim::enter_visual_char_bridge(self);
    }

    /// `V` from Normal — enter linewise Visual mode, anchoring on the current
    /// line. Motions extend the selection by whole lines.
    pub fn enter_visual_line(&mut self) {
        vim::enter_visual_line_bridge(self);
    }

    /// `<C-v>` from Normal — enter Visual-block mode. The selection is a
    /// rectangle whose corners are the anchor and the live cursor.
    pub fn enter_visual_block(&mut self) {
        vim::enter_visual_block_bridge(self);
    }

    /// Esc from any visual mode — set `<` / `>` marks, stash the selection
    /// for `gv` re-entry, then return to Normal mode.
    pub fn exit_visual_to_normal(&mut self) {
        vim::exit_visual_to_normal_bridge(self);
    }

    /// `o` in Visual / VisualLine / VisualBlock — swap the cursor and anchor
    /// so the user can extend the other end of the selection. Does NOT
    /// mutate the selection range; only the active endpoint changes.
    pub fn visual_o_toggle(&mut self) {
        vim::visual_o_toggle_bridge(self);
    }

    /// `gv` — restore the last visual selection (mode + anchor + cursor
    /// position). No-op when no visual selection has been exited yet.
    pub fn reenter_last_visual(&mut self) {
        vim::reenter_last_visual_bridge(self);
    }

    /// Direct mode-transition entry point. Sets both the internal FSM mode
    /// and the stable `current_mode` field read by [`Editor::vim_mode`].
    ///
    /// Prefer the semantic primitives (`enter_visual_char`, `enter_insert_i`,
    /// …) which also set up required bookkeeping (anchors, sessions, …).
    /// Use `set_mode` only when you need a raw mode flip without side-effects.
    pub fn set_mode(&mut self, mode: VimMode) {
        vim::set_mode_bridge(self, mode);
    }
}

// ── Phase 6.6b: FSM state accessors (for hjkl-vim ownership) ─────────────────
//
// The FSM (now in hjkl-vim) reads/writes `VimState` fields through public
// `Editor` accessors and mutators defined in this block. Each method gets a
// one-line `///` rustdoc. Fields mutated as a unit get a combined action method
// rather than individual getters + setters (e.g. `accumulate_count_digit`).

/// State carried between [`Editor::begin_step`] and [`Editor::end_step`].
///
/// Treat as opaque — construct by calling `begin_step` and pass the
/// returned value directly into `end_step` without modification.
/// The fields capture per-step pre-dispatch state that the epilogue
/// needs to run its invariants correctly.
pub struct StepBookkeeping {
    /// True when the pending chord before this step was a macro-chord
    /// (`q{reg}` or `@{reg}`). The recorder hook skips these bookkeeping
    /// keys so that only the *payload* keys enter `recording_keys`.
    pub pending_was_macro_chord: bool,
    /// True when the mode was Insert *before* the FSM body ran. Used by
    /// the Ctrl-o one-shot-normal epilogue to decide whether to bounce
    /// back into Insert.
    pub was_insert: bool,
    /// Pre-dispatch visual snapshot. When the FSM body transitions out of
    /// a visual mode the epilogue uses this to set the `<`/`>` marks and
    /// store `last_visual` for `gv`.
    pub pre_visual_snapshot: Option<vim::LastVisual>,
}

impl<H: crate::types::Host> Editor<hjkl_buffer::Buffer, H> {
    // ── Pending chord ─────────────────────────────────────────────────────────

    /// Return a clone of the current pending chord state.
    pub fn pending(&self) -> vim::Pending {
        self.vim.pending.clone()
    }

    /// Overwrite the pending chord state.
    pub fn set_pending(&mut self, p: vim::Pending) {
        self.vim.pending = p;
    }

    /// Atomically take the pending chord, replacing it with `Pending::None`.
    pub fn take_pending(&mut self) -> vim::Pending {
        std::mem::take(&mut self.vim.pending)
    }

    // ── Count prefix ──────────────────────────────────────────────────────────

    /// Return the raw digit-prefix count (`0` = no prefix typed yet).
    pub fn count(&self) -> usize {
        self.vim.count
    }

    /// Overwrite the digit-prefix count directly.
    pub fn set_count(&mut self, c: usize) {
        self.vim.count = c;
    }

    /// Accumulate one more digit into the count prefix (mirrors `count * 10 + digit`).
    pub fn accumulate_count_digit(&mut self, digit: usize) {
        self.vim.count = self.vim.count.saturating_mul(10) + digit;
    }

    /// Reset the count prefix to zero (no pending count).
    pub fn reset_count(&mut self) {
        self.vim.count = 0;
    }

    /// Consume the count and return it; resets to zero. Returns `1` when no
    /// prefix was typed (mirrors `take_count` in vim.rs).
    pub fn take_count(&mut self) -> usize {
        if self.vim.count > 0 {
            let n = self.vim.count;
            self.vim.count = 0;
            n
        } else {
            1
        }
    }

    // ── Internal FSM mode ─────────────────────────────────────────────────────

    /// Return the FSM-internal mode (Normal / Insert / Visual / …).
    pub fn fsm_mode(&self) -> vim::Mode {
        self.vim.mode
    }

    /// Overwrite the FSM-internal mode without side-effects. Prefer the
    /// semantic primitives (`enter_insert_i`, `enter_visual_char`, …).
    pub fn set_fsm_mode(&mut self, m: vim::Mode) {
        self.vim.mode = m;
        self.vim.current_mode = self.vim.public_mode();
    }

    // ── Replaying flag ────────────────────────────────────────────────────────

    /// `true` while the `.` dot-repeat replay is running.
    pub fn is_replaying(&self) -> bool {
        self.vim.replaying
    }

    /// Set or clear the dot-replay flag.
    pub fn set_replaying(&mut self, v: bool) {
        self.vim.replaying = v;
    }

    // ── One-shot normal (Ctrl-o) ──────────────────────────────────────────────

    /// `true` when we entered Normal from Insert via `Ctrl-o` and will return
    /// to Insert after the next complete command.
    pub fn is_one_shot_normal(&self) -> bool {
        self.vim.one_shot_normal
    }

    /// Set or clear the Ctrl-o one-shot-normal flag.
    pub fn set_one_shot_normal(&mut self, v: bool) {
        self.vim.one_shot_normal = v;
    }

    // ── Last find (f/F/t/T target) ────────────────────────────────────────────

    /// Return the last `f`/`F`/`t`/`T` target as `(char, forward, till)`, or
    /// `None` before any find command was executed.
    pub fn last_find(&self) -> Option<(char, bool, bool)> {
        self.vim.last_find
    }

    /// Overwrite the stored last-find target.
    pub fn set_last_find(&mut self, target: Option<(char, bool, bool)>) {
        self.vim.last_find = target;
    }

    // ── Last change (dot-repeat payload) ─────────────────────────────────────

    /// Return a clone of the last recorded mutating change, or `None` before
    /// any change has been made.
    pub fn last_change(&self) -> Option<vim::LastChange> {
        self.vim.last_change.clone()
    }

    /// Overwrite the stored last-change record.
    pub fn set_last_change(&mut self, lc: Option<vim::LastChange>) {
        self.vim.last_change = lc;
    }

    /// Borrow the last-change record mutably (e.g. to fill in an `inserted`
    /// field after the insert session completes).
    pub fn last_change_mut(&mut self) -> Option<&mut vim::LastChange> {
        self.vim.last_change.as_mut()
    }

    // ── Insert session ────────────────────────────────────────────────────────

    /// Borrow the active insert session, or `None` when not in Insert mode.
    pub fn insert_session(&self) -> Option<&vim::InsertSession> {
        self.vim.insert_session.as_ref()
    }

    /// Borrow the active insert session mutably.
    pub fn insert_session_mut(&mut self) -> Option<&mut vim::InsertSession> {
        self.vim.insert_session.as_mut()
    }

    /// Atomically take the insert session out, leaving `None`.
    pub fn take_insert_session(&mut self) -> Option<vim::InsertSession> {
        self.vim.insert_session.take()
    }

    /// Install a new insert session, replacing any existing one.
    pub fn set_insert_session(&mut self, s: Option<vim::InsertSession>) {
        self.vim.insert_session = s;
    }

    // ── Visual anchors ────────────────────────────────────────────────────────

    /// Return the charwise Visual-mode anchor `(row, col)`.
    pub fn visual_anchor(&self) -> (usize, usize) {
        self.vim.visual_anchor
    }

    /// Overwrite the charwise Visual-mode anchor.
    pub fn set_visual_anchor(&mut self, anchor: (usize, usize)) {
        self.vim.visual_anchor = anchor;
    }

    /// Return the VisualLine anchor row.
    pub fn visual_line_anchor(&self) -> usize {
        self.vim.visual_line_anchor
    }

    /// Overwrite the VisualLine anchor row.
    pub fn set_visual_line_anchor(&mut self, row: usize) {
        self.vim.visual_line_anchor = row;
    }

    /// Return the VisualBlock anchor `(row, col)`.
    pub fn block_anchor(&self) -> (usize, usize) {
        self.vim.block_anchor
    }

    /// Overwrite the VisualBlock anchor.
    pub fn set_block_anchor(&mut self, anchor: (usize, usize)) {
        self.vim.block_anchor = anchor;
    }

    /// Return the VisualBlock virtual column used to survive j/k row clamping.
    pub fn block_vcol(&self) -> usize {
        self.vim.block_vcol
    }

    /// Overwrite the VisualBlock virtual column.
    pub fn set_block_vcol(&mut self, vcol: usize) {
        self.vim.block_vcol = vcol;
    }

    // ── Yank linewise flag ────────────────────────────────────────────────────

    /// `true` when the last yank/cut was linewise (affects `p`/`P` layout).
    pub fn yank_linewise(&self) -> bool {
        self.vim.yank_linewise
    }

    /// Set or clear the linewise-yank flag.
    pub fn set_yank_linewise(&mut self, v: bool) {
        self.vim.yank_linewise = v;
    }

    // ── Pending register selector ─────────────────────────────────────────────
    // Note: `pending_register()` getter already exists at line ~1254 (Phase 4e).
    // Only the mutators are new here.

    /// Overwrite the pending register selector (Phase 6.6b mutator companion to
    /// the existing `pending_register()` getter).
    pub fn set_pending_register_raw(&mut self, reg: Option<char>) {
        self.vim.pending_register = reg;
    }

    /// Atomically take the pending register, returning `None` afterward.
    pub fn take_pending_register_raw(&mut self) -> Option<char> {
        self.vim.pending_register.take()
    }

    // ── Macro recording ───────────────────────────────────────────────────────

    /// Return the register currently being recorded into, or `None`.
    pub fn recording_macro(&self) -> Option<char> {
        self.vim.recording_macro
    }

    /// Overwrite the recording-macro target register.
    pub fn set_recording_macro(&mut self, reg: Option<char>) {
        self.vim.recording_macro = reg;
    }

    /// Append one input to the in-progress macro recording buffer.
    pub fn push_recording_key(&mut self, input: crate::input::Input) {
        self.vim.recording_keys.push(input);
    }

    /// Atomically take the recorded key sequence, leaving an empty vec.
    pub fn take_recording_keys(&mut self) -> Vec<crate::input::Input> {
        std::mem::take(&mut self.vim.recording_keys)
    }

    /// Overwrite the recording-keys buffer (e.g. to seed from a register).
    pub fn set_recording_keys(&mut self, keys: Vec<crate::input::Input>) {
        self.vim.recording_keys = keys;
    }

    // ── Macro replay flag ─────────────────────────────────────────────────────

    /// `true` while `@reg` macro replay is running (suppresses re-recording).
    pub fn is_replaying_macro_raw(&self) -> bool {
        self.vim.replaying_macro
    }

    /// Set or clear the macro-replay-in-progress flag.
    pub fn set_replaying_macro_raw(&mut self, v: bool) {
        self.vim.replaying_macro = v;
    }

    // ── Last macro register ───────────────────────────────────────────────────

    /// Return the register of the most recently played macro (`@@` source).
    pub fn last_macro(&self) -> Option<char> {
        self.vim.last_macro
    }

    /// Overwrite the last-played-macro register.
    pub fn set_last_macro(&mut self, reg: Option<char>) {
        self.vim.last_macro = reg;
    }

    // ── Last insert position ──────────────────────────────────────────────────

    /// Return the cursor position when Insert mode was last exited (for `gi`).
    pub fn last_insert_pos(&self) -> Option<(usize, usize)> {
        self.vim.last_insert_pos
    }

    /// Overwrite the stored last-insert position.
    pub fn set_last_insert_pos(&mut self, pos: Option<(usize, usize)>) {
        self.vim.last_insert_pos = pos;
    }

    // ── Last visual selection ─────────────────────────────────────────────────

    /// Return the saved visual selection snapshot for `gv`, or `None`.
    pub fn last_visual(&self) -> Option<vim::LastVisual> {
        self.vim.last_visual
    }

    /// Overwrite the saved visual selection snapshot.
    pub fn set_last_visual(&mut self, snap: Option<vim::LastVisual>) {
        self.vim.last_visual = snap;
    }

    // ── Viewport-pinned flag ──────────────────────────────────────────────────

    /// `true` when `zz`/`zt`/`zb` pinned the viewport this step (suppresses
    /// the end-of-step scrolloff pass).
    pub fn viewport_pinned(&self) -> bool {
        self.vim.viewport_pinned
    }

    /// Set or clear the viewport-pinned flag.
    pub fn set_viewport_pinned(&mut self, v: bool) {
        self.vim.viewport_pinned = v;
    }

    // ── Insert pending register (Ctrl-R wait) ─────────────────────────────────

    /// `true` while waiting for the register-name key after `Ctrl-R` in
    /// Insert mode.
    pub fn insert_pending_register(&self) -> bool {
        self.vim.insert_pending_register
    }

    /// Set or clear the `Ctrl-R` register-wait flag.
    pub fn set_insert_pending_register(&mut self, v: bool) {
        self.vim.insert_pending_register = v;
    }

    // ── Change-mark start ─────────────────────────────────────────────────────

    /// Return the stashed `[` mark start for a Change operation, or `None`.
    pub fn change_mark_start(&self) -> Option<(usize, usize)> {
        self.vim.change_mark_start
    }

    /// Atomically take the change-mark start, leaving `None`.
    pub fn take_change_mark_start(&mut self) -> Option<(usize, usize)> {
        self.vim.change_mark_start.take()
    }

    /// Overwrite the change-mark start.
    pub fn set_change_mark_start(&mut self, pos: Option<(usize, usize)>) {
        self.vim.change_mark_start = pos;
    }

    // ── Timeout tracking ──────────────────────────────────────────────────────

    /// Return the wall-clock `Instant` of the last keystroke.
    pub fn last_input_at(&self) -> Option<std::time::Instant> {
        self.vim.last_input_at
    }

    /// Overwrite the wall-clock last-input timestamp.
    pub fn set_last_input_at(&mut self, t: Option<std::time::Instant>) {
        self.vim.last_input_at = t;
    }

    /// Return the `Host::now()` duration at the last keystroke.
    pub fn last_input_host_at(&self) -> Option<core::time::Duration> {
        self.vim.last_input_host_at
    }

    /// Overwrite the host-clock last-input timestamp.
    pub fn set_last_input_host_at(&mut self, d: Option<core::time::Duration>) {
        self.vim.last_input_host_at = d;
    }

    // ── Search prompt ──────────────────────────────────────────────────────────

    /// Borrow the live search prompt, or `None` when not in search-prompt mode.
    pub fn search_prompt_state(&self) -> Option<&vim::SearchPrompt> {
        self.vim.search_prompt.as_ref()
    }

    /// Borrow the live search prompt mutably.
    pub fn search_prompt_state_mut(&mut self) -> Option<&mut vim::SearchPrompt> {
        self.vim.search_prompt.as_mut()
    }

    /// Atomically take the search prompt, leaving `None`.
    pub fn take_search_prompt_state(&mut self) -> Option<vim::SearchPrompt> {
        self.vim.search_prompt.take()
    }

    /// Install a new search prompt (entering search-prompt mode).
    pub fn set_search_prompt_state(&mut self, prompt: Option<vim::SearchPrompt>) {
        self.vim.search_prompt = prompt;
    }

    // ── Last search pattern / direction ───────────────────────────────────────
    // Note: `last_search_forward()` getter already exists at line ~1909.
    // `set_last_search()` combined mutator exists at line ~1918.
    // Only new / complementary accessors are added here.

    /// Return the most recently committed search pattern, or `None`.
    pub fn last_search_pattern(&self) -> Option<&str> {
        self.vim.last_search.as_deref()
    }

    /// Overwrite the stored last-search pattern without changing direction
    /// (use the existing `set_last_search` for the combined update).
    pub fn set_last_search_pattern_only(&mut self, pattern: Option<String>) {
        self.vim.last_search = pattern;
    }

    /// Overwrite only the last-search direction flag.
    pub fn set_last_search_forward_only(&mut self, forward: bool) {
        self.vim.last_search_forward = forward;
    }

    // ── Search history ────────────────────────────────────────────────────────

    /// Borrow the committed search-pattern history (oldest first).
    pub fn search_history(&self) -> &[String] {
        &self.vim.search_history
    }

    /// Borrow the search history mutably (e.g. to push a new entry).
    pub fn search_history_mut(&mut self) -> &mut Vec<String> {
        &mut self.vim.search_history
    }

    /// Return the current search-history navigation cursor index.
    pub fn search_history_cursor(&self) -> Option<usize> {
        self.vim.search_history_cursor
    }

    /// Overwrite the search-history navigation cursor.
    pub fn set_search_history_cursor(&mut self, idx: Option<usize>) {
        self.vim.search_history_cursor = idx;
    }

    // ── Jump lists ────────────────────────────────────────────────────────────

    /// Borrow the back half of the jump list (entries Ctrl-o pops from).
    pub fn jump_back_list(&self) -> &[(usize, usize)] {
        &self.vim.jump_back
    }

    /// Borrow the back jump list mutably (push / pop).
    pub fn jump_back_list_mut(&mut self) -> &mut Vec<(usize, usize)> {
        &mut self.vim.jump_back
    }

    /// Borrow the forward half of the jump list (entries Ctrl-i pops from).
    pub fn jump_fwd_list(&self) -> &[(usize, usize)] {
        &self.vim.jump_fwd
    }

    /// Borrow the forward jump list mutably (push / pop / clear).
    pub fn jump_fwd_list_mut(&mut self) -> &mut Vec<(usize, usize)> {
        &mut self.vim.jump_fwd
    }

    // ── Phase 6.6c: search + jump helpers (public Editor API) ───────────────
    //
    // `push_search_pattern`, `push_jump`, `record_search_history`, and
    // `walk_search_history` are public `Editor` methods so that `hjkl-vim`'s
    // search-prompt and normal-mode FSM can call them via the public API.

    /// Compile `pattern` into a regex and install it as the active search
    /// pattern. Respects `:set ignorecase` / `:set smartcase`. An empty or
    /// invalid pattern clears the highlight without raising an error.
    pub fn push_search_pattern(&mut self, pattern: &str) {
        let compiled = if pattern.is_empty() {
            None
        } else {
            let case_insensitive = self.settings().ignore_case
                && !(self.settings().smartcase && pattern.chars().any(|c| c.is_uppercase()));
            let effective: std::borrow::Cow<'_, str> = if case_insensitive {
                std::borrow::Cow::Owned(format!("(?i){pattern}"))
            } else {
                std::borrow::Cow::Borrowed(pattern)
            };
            regex::Regex::new(&effective).ok()
        };
        let wrap = self.settings().wrapscan;
        self.set_search_pattern(compiled);
        self.search_state_mut().wrap_around = wrap;
    }

    /// Record a pre-jump cursor position onto the back jumplist. Called
    /// before any "big jump" motion (`gg`/`G`, `%`, `*`/`#`, `n`/`N`,
    /// committed `/` or `?`, …). Branching off the history clears the
    /// forward half, matching vim's "redo-is-lost" semantics.
    pub fn push_jump(&mut self, from: (usize, usize)) {
        self.vim.jump_back.push(from);
        if self.vim.jump_back.len() > vim::JUMPLIST_MAX {
            self.vim.jump_back.remove(0);
        }
        self.vim.jump_fwd.clear();
    }

    /// Push `pattern` onto the committed search history. Skips if the
    /// most recent entry already matches (consecutive dedupe) and trims
    /// the oldest entries beyond the history cap.
    pub fn record_search_history(&mut self, pattern: &str) {
        if pattern.is_empty() {
            return;
        }
        if self.vim.search_history.last().map(String::as_str) == Some(pattern) {
            return;
        }
        self.vim.search_history.push(pattern.to_string());
        let len = self.vim.search_history.len();
        if len > vim::SEARCH_HISTORY_MAX {
            self.vim
                .search_history
                .drain(0..len - vim::SEARCH_HISTORY_MAX);
        }
    }

    /// Walk the search-prompt history by `dir` steps. `dir = -1` moves
    /// toward older entries (Ctrl-P / Up); `dir = 1` toward newer ones
    /// (Ctrl-N / Down). Stops at the ends; does nothing if there is no
    /// active search prompt.
    pub fn walk_search_history(&mut self, dir: isize) {
        if self.vim.search_history.is_empty() || self.vim.search_prompt.is_none() {
            return;
        }
        let len = self.vim.search_history.len();
        let next_idx = match (self.vim.search_history_cursor, dir) {
            (None, -1) => Some(len - 1),
            (None, 1) => return,
            (Some(i), -1) => i.checked_sub(1),
            (Some(i), 1) if i + 1 < len => Some(i + 1),
            _ => None,
        };
        let Some(idx) = next_idx else {
            return;
        };
        self.vim.search_history_cursor = Some(idx);
        let text = self.vim.search_history[idx].clone();
        if let Some(prompt) = self.vim.search_prompt.as_mut() {
            prompt.cursor = text.chars().count();
            prompt.text = text.clone();
        }
        self.push_search_pattern(&text);
    }

    // ── Phase 6.6d: pre/post FSM bookkeeping ────────────────────────────────
    //
    // `begin_step` and `end_step` are the bookkeeping prelude/epilogue that
    // `hjkl_vim::dispatch_input` wraps around its per-mode FSM dispatch.

    /// Pre-dispatch bookkeeping that must run before every per-mode FSM step.
    ///
    /// Call this at the start of every step; pass the returned
    /// [`StepBookkeeping`] to [`end_step`] after the FSM body finishes.
    ///
    /// Returns `Ok(bk)` when the caller should proceed with FSM dispatch.
    /// Returns `Err(consumed)` when the prelude itself handled the input
    /// (macro-stop chord); in that case skip the FSM body and do NOT call
    /// `end_step` — the macro-stop path is a true short-circuit with no
    /// epilogue needed.
    ///
    /// This method does NOT handle the search-prompt intercept — callers
    /// must check `search_prompt_state().is_some()` before calling `begin_step`
    /// and dispatch to the search-prompt FSM body directly.
    pub fn begin_step(&mut self, input: Input) -> Result<StepBookkeeping, bool> {
        use crate::input::Key;
        use vim::{Mode, Pending};
        // ── Timestamps ───────────────────────────────────────────────────────
        // Phase 7f: sync buffer before motion handlers see it.
        self.sync_buffer_content_from_textarea();
        // `:set timeoutlen` chord-timeout handling.
        let now = std::time::Instant::now();
        let host_now = self.host.now();
        let timed_out = match self.vim.last_input_host_at {
            Some(prev) => host_now.saturating_sub(prev) > self.settings.timeout_len,
            None => false,
        };
        if timed_out {
            let chord_in_flight = !matches!(self.vim.pending, Pending::None)
                || self.vim.count != 0
                || self.vim.pending_register.is_some()
                || self.vim.insert_pending_register;
            if chord_in_flight {
                self.vim.clear_pending_prefix();
            }
        }
        self.vim.last_input_at = Some(now);
        self.vim.last_input_host_at = Some(host_now);
        // ── Macro-stop: bare `q` outside Insert ends the recording ───────────
        if self.vim.recording_macro.is_some()
            && !self.vim.replaying_macro
            && matches!(self.vim.pending, Pending::None)
            && self.vim.mode != Mode::Insert
            && input.key == Key::Char('q')
            && !input.ctrl
            && !input.alt
        {
            let reg = self.vim.recording_macro.take().unwrap();
            let keys = std::mem::take(&mut self.vim.recording_keys);
            let text = crate::input::encode_macro(&keys);
            self.set_named_register_text(reg.to_ascii_lowercase(), text);
            return Err(true);
        }
        // ── Snapshots for epilogue ────────────────────────────────────────────
        let pending_was_macro_chord = matches!(
            self.vim.pending,
            Pending::RecordMacroTarget | Pending::PlayMacroTarget { .. }
        );
        let was_insert = self.vim.mode == Mode::Insert;
        let pre_visual_snapshot = match self.vim.mode {
            Mode::Visual => Some(vim::LastVisual {
                mode: Mode::Visual,
                anchor: self.vim.visual_anchor,
                cursor: self.cursor(),
                block_vcol: 0,
            }),
            Mode::VisualLine => Some(vim::LastVisual {
                mode: Mode::VisualLine,
                anchor: (self.vim.visual_line_anchor, 0),
                cursor: self.cursor(),
                block_vcol: 0,
            }),
            Mode::VisualBlock => Some(vim::LastVisual {
                mode: Mode::VisualBlock,
                anchor: self.vim.block_anchor,
                cursor: self.cursor(),
                block_vcol: self.vim.block_vcol,
            }),
            _ => None,
        };
        Ok(StepBookkeeping {
            pending_was_macro_chord,
            was_insert,
            pre_visual_snapshot,
        })
    }

    /// Post-dispatch bookkeeping that must run after every per-mode FSM step.
    ///
    /// `input` is the same input that was passed to `begin_step`.
    /// `bk` is the [`StepBookkeeping`] returned by `begin_step`.
    /// `consumed` is the return value of the FSM body; this method returns
    /// it after running all epilogue invariants.
    ///
    /// Must NOT be called when `begin_step` returned `Err(...)`.
    pub fn end_step(&mut self, input: Input, bk: StepBookkeeping, consumed: bool) -> bool {
        use crate::input::Key;
        use vim::{Mode, Pending};
        let StepBookkeeping {
            pending_was_macro_chord,
            was_insert,
            pre_visual_snapshot,
        } = bk;
        // ── Visual-exit: set `<`/`>` marks and stash `last_visual` ───────────
        if let Some(snap) = pre_visual_snapshot
            && !matches!(
                self.vim.mode,
                Mode::Visual | Mode::VisualLine | Mode::VisualBlock
            )
        {
            let (lo, hi) = match snap.mode {
                Mode::Visual => {
                    if snap.anchor <= snap.cursor {
                        (snap.anchor, snap.cursor)
                    } else {
                        (snap.cursor, snap.anchor)
                    }
                }
                Mode::VisualLine => {
                    let r_lo = snap.anchor.0.min(snap.cursor.0);
                    let r_hi = snap.anchor.0.max(snap.cursor.0);
                    let last_col = self
                        .buffer()
                        .lines()
                        .get(r_hi)
                        .map(|l| l.chars().count().saturating_sub(1))
                        .unwrap_or(0);
                    ((r_lo, 0), (r_hi, last_col))
                }
                Mode::VisualBlock => {
                    let (r1, c1) = snap.anchor;
                    let (r2, c2) = snap.cursor;
                    ((r1.min(r2), c1.min(c2)), (r1.max(r2), c1.max(c2)))
                }
                _ => {
                    if snap.anchor <= snap.cursor {
                        (snap.anchor, snap.cursor)
                    } else {
                        (snap.cursor, snap.anchor)
                    }
                }
            };
            self.set_mark('<', lo);
            self.set_mark('>', hi);
            self.vim.last_visual = Some(snap);
        }
        // ── Ctrl-o one-shot-normal return to Insert ───────────────────────────
        if !was_insert
            && self.vim.one_shot_normal
            && self.vim.mode == Mode::Normal
            && matches!(self.vim.pending, Pending::None)
        {
            self.vim.one_shot_normal = false;
            self.vim.mode = Mode::Insert;
        }
        // ── Content + viewport sync ───────────────────────────────────────────
        self.sync_buffer_content_from_textarea();
        if !self.vim.viewport_pinned {
            self.ensure_cursor_in_scrolloff();
        }
        self.vim.viewport_pinned = false;
        // ── Recorder hook ─────────────────────────────────────────────────────
        if self.vim.recording_macro.is_some()
            && !self.vim.replaying_macro
            && input.key != Key::Char('q')
            && !pending_was_macro_chord
        {
            self.vim.recording_keys.push(input);
        }
        // ── Phase 6.3: current_mode sync ─────────────────────────────────────
        self.vim.current_mode = self.vim.public_mode();
        consumed
    }

    // ── Phase 6.6e: additional public primitives for hjkl-vim::normal ─────────

    /// `true` when the editor is in any visual mode (Visual / VisualLine /
    /// VisualBlock). Convenience wrapper around `vim_mode()` for hjkl-vim.
    pub fn is_visual(&self) -> bool {
        matches!(
            self.vim.mode,
            vim::Mode::Visual | vim::Mode::VisualLine | vim::Mode::VisualBlock
        )
    }

    /// Compute the VisualBlock rectangle corners: `(top_row, bot_row,
    /// left_col, right_col)`. Uses `block_anchor` and `block_vcol` (the
    /// virtual column, which survives j/k clamping to shorter rows).
    ///
    /// Promoted in Phase 6.6e so `hjkl-vim::normal` can compute the block
    /// extents needed for VisualBlock `I` / `A` / `r` without accessing
    /// engine-private helpers.
    pub fn visual_block_bounds(&self) -> (usize, usize, usize, usize) {
        let (ar, ac) = self.vim.block_anchor;
        let (cr, _) = self.cursor();
        let cc = self.vim.block_vcol;
        let top = ar.min(cr);
        let bot = ar.max(cr);
        let left = ac.min(cc);
        let right = ac.max(cc);
        (top, bot, left, right)
    }

    /// Return the character count (code-point count) of line `row`, or `0`
    /// when `row` is out of range. Used by hjkl-vim::normal for VisualBlock
    /// I / A column computations.
    pub fn line_char_count(&self, row: usize) -> usize {
        buf_line_chars(&self.buffer, row)
    }

    /// Apply operator over `motion` with `count` repetitions. The full
    /// vim-quirks path (operator context for `l`, clamping, etc.) is applied.
    ///
    /// Promoted to the public surface in Phase 6.6e so `hjkl-vim::normal`'s
    /// relocated `handle_after_op` can call it directly with a parsed `Motion`
    /// without re-entering the engine FSM.
    pub fn apply_op_with_motion_direct(
        &mut self,
        op: crate::vim::Operator,
        motion: &crate::vim::Motion,
        count: usize,
    ) {
        vim::apply_op_with_motion(self, op, motion, count);
    }

    /// `Ctrl-a` / `Ctrl-x` — adjust the number under or after the cursor.
    /// `delta = 1` increments; `delta = -1` decrements; larger deltas
    /// multiply as in vim's `5<C-a>`. Promoted in Phase 6.6e so
    /// `hjkl-vim::normal` can dispatch `Ctrl-a` / `Ctrl-x`.
    pub fn adjust_number(&mut self, delta: i64) {
        vim::adjust_number(self, delta);
    }

    /// Open the `/` or `?` search prompt. `forward = true` for `/`,
    /// `false` for `?`. Promoted in Phase 6.6e so `hjkl-vim::normal` can
    /// dispatch `/` and `?` without re-entering the engine FSM.
    pub fn enter_search(&mut self, forward: bool) {
        vim::enter_search(self, forward);
    }

    /// Enter Insert mode at the left edge of a VisualBlock selection for
    /// `I`. Moves the cursor to `(top, col)`, resets to Normal internally,
    /// then begins an insert session with `InsertReason::BlockEdge`.
    ///
    /// Promoted in Phase 6.6e so `hjkl-vim::normal` can dispatch the
    /// VisualBlock `I` command without accessing engine-private helpers.
    pub fn visual_block_insert_at_left(&mut self, top: usize, bot: usize, col: usize) {
        self.jump_cursor(top, col);
        self.vim.mode = vim::Mode::Normal;
        vim::begin_insert(self, 1, vim::InsertReason::BlockEdge { top, bot, col });
    }

    /// Enter Insert mode at the right edge of a VisualBlock selection for
    /// `A`. Moves the cursor to `(top, col)`, resets to Normal internally,
    /// then begins an insert session with `InsertReason::BlockEdge`.
    ///
    /// Promoted in Phase 6.6e so `hjkl-vim::normal` can dispatch the
    /// VisualBlock `A` command without accessing engine-private helpers.
    pub fn visual_block_append_at_right(&mut self, top: usize, bot: usize, col: usize) {
        self.jump_cursor(top, col);
        self.vim.mode = vim::Mode::Normal;
        vim::begin_insert(self, 1, vim::InsertReason::BlockEdge { top, bot, col });
    }

    /// Execute a motion (cursor movement), push to the jumplist for big jumps,
    /// and update the sticky column. Mirrors the engine FSM's `execute_motion`
    /// free function. Promoted in Phase 6.6e for `hjkl-vim::normal`.
    pub fn execute_motion(&mut self, motion: crate::vim::Motion, count: usize) {
        vim::execute_motion(self, motion, count);
    }

    /// Update the VisualBlock virtual column after a motion in VisualBlock mode.
    /// Horizontal motions sync `block_vcol` to the cursor column; vertical /
    /// non-h/l motions leave it alone so the intended column survives clamping
    /// to shorter rows. Promoted in Phase 6.6e for `hjkl-vim::normal`.
    pub fn update_block_vcol(&mut self, motion: &crate::vim::Motion) {
        vim::update_block_vcol(self, motion);
    }

    /// Apply `op` over the current visual selection (char-wise, linewise, or
    /// block). Mirrors the engine's internal `apply_visual_operator` free fn.
    /// Promoted in Phase 6.6e for `hjkl-vim::normal`.
    pub fn apply_visual_operator(&mut self, op: crate::vim::Operator) {
        vim::apply_visual_operator(self, op);
    }

    /// Replace each character cell in the current VisualBlock selection with
    /// `ch`. Mirrors the engine's `block_replace` free fn. Promoted in Phase
    /// 6.6e for the VisualBlock `r<ch>` command in `hjkl-vim::normal`.
    pub fn replace_block_char(&mut self, ch: char) {
        vim::block_replace(self, ch);
    }

    /// Extend the current visual selection to cover the text object identified
    /// by `ch` and `inner`. Maps `ch` to a `TextObject`, resolves its range
    /// via `text_object_range`, then updates the visual anchor and cursor.
    ///
    /// Promoted in Phase 6.6e for the visual-mode `i<ch>` / `a<ch>` commands
    /// in `hjkl-vim::normal::handle_visual_text_obj`.
    pub fn visual_text_obj_extend(&mut self, ch: char, inner: bool) {
        use crate::vim::{Mode, TextObject};
        let obj = match ch {
            'w' => TextObject::Word { big: false },
            'W' => TextObject::Word { big: true },
            '"' | '\'' | '`' => TextObject::Quote(ch),
            '(' | ')' | 'b' => TextObject::Bracket('('),
            '[' | ']' => TextObject::Bracket('['),
            '{' | '}' | 'B' => TextObject::Bracket('{'),
            '<' | '>' => TextObject::Bracket('<'),
            'p' => TextObject::Paragraph,
            't' => TextObject::XmlTag,
            's' => TextObject::Sentence,
            _ => return,
        };
        let Some((start, end, kind)) = vim::text_object_range(self, obj, inner) else {
            return;
        };
        match kind {
            crate::vim::RangeKind::Linewise => {
                self.vim.visual_line_anchor = start.0;
                self.vim.mode = Mode::VisualLine;
                self.vim.current_mode = VimMode::VisualLine;
                self.jump_cursor(end.0, 0);
            }
            _ => {
                self.vim.mode = Mode::Visual;
                self.vim.current_mode = VimMode::Visual;
                self.vim.visual_anchor = (start.0, start.1);
                let (er, ec) = vim::retreat_one(self, end);
                self.jump_cursor(er, ec);
            }
        }
    }
}

/// Visual column of the character at `char_col` in `line`, treating `\t`
/// as expansion to the next `tab_width` stop and every other char as
/// 1 cell wide. Wide-char support (CJK, emoji) is a separate concern —
/// the cursor math elsewhere also assumes single-cell chars.
fn visual_col_for_char(line: &str, char_col: usize, tab_width: usize) -> usize {
    let mut visual = 0usize;
    for (i, ch) in line.chars().enumerate() {
        if i >= char_col {
            break;
        }
        if ch == '\t' {
            visual += tab_width - (visual % tab_width);
        } else {
            visual += 1;
        }
    }
    visual
}

#[cfg(feature = "crossterm")]
impl From<KeyEvent> for Input {
    fn from(key: KeyEvent) -> Self {
        let k = match key.code {
            KeyCode::Char(c) => Key::Char(c),
            KeyCode::Backspace => Key::Backspace,
            KeyCode::Delete => Key::Delete,
            KeyCode::Enter => Key::Enter,
            KeyCode::Left => Key::Left,
            KeyCode::Right => Key::Right,
            KeyCode::Up => Key::Up,
            KeyCode::Down => Key::Down,
            KeyCode::Home => Key::Home,
            KeyCode::End => Key::End,
            KeyCode::Tab => Key::Tab,
            KeyCode::Esc => Key::Esc,
            _ => Key::Null,
        };
        Input {
            key: k,
            ctrl: key.modifiers.contains(KeyModifiers::CONTROL),
            alt: key.modifiers.contains(KeyModifiers::ALT),
            shift: key.modifiers.contains(KeyModifiers::SHIFT),
        }
    }
}

/// Crossterm `KeyEvent` → engine `Input`. Thin wrapper that delegates
/// to the [`From`] impl above; kept as a free fn for the in-tree
/// callers in the legacy ratatui-coupled paths.
#[cfg(feature = "crossterm")]
pub fn crossterm_to_input(key: KeyEvent) -> Input {
    Input::from(key)
}

#[cfg(all(test, feature = "crossterm", feature = "ratatui"))]
mod tests {
    use super::*;
    use crate::types::Host;
    use crossterm::event::KeyEvent;

    #[allow(dead_code)]
    fn key(code: KeyCode) -> KeyEvent {
        KeyEvent::new(code, KeyModifiers::NONE)
    }
    #[allow(dead_code)]
    fn shift_key(code: KeyCode) -> KeyEvent {
        KeyEvent::new(code, KeyModifiers::SHIFT)
    }
    #[allow(dead_code)]
    fn ctrl_key(code: KeyCode) -> KeyEvent {
        KeyEvent::new(code, KeyModifiers::CONTROL)
    }

    #[test]
    fn intern_style_dedups_engine_native_styles() {
        use crate::types::{Attrs, Color, Style};
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        let s = Style {
            fg: Some(Color(255, 0, 0)),
            bg: None,
            attrs: Attrs::BOLD,
        };
        let id_a = e.intern_style(s);
        // Re-interning the same engine style returns the same id.
        let id_b = e.intern_style(s);
        assert_eq!(id_a, id_b);
        // Engine accessor returns the same style back.
        let back = e.engine_style_at(id_a).expect("interned");
        assert_eq!(back, s);
    }

    #[test]
    fn engine_style_at_out_of_range_returns_none() {
        let e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        assert!(e.engine_style_at(99).is_none());
    }

    #[test]
    fn options_bridge_roundtrip() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        let opts = e.current_options();
        // 0.2.0: defaults flipped to modern editor norms — 4-space soft tabs.
        assert_eq!(opts.shiftwidth, 4);
        assert_eq!(opts.tabstop, 4);

        let new_opts = crate::types::Options {
            shiftwidth: 4,
            tabstop: 2,
            ignorecase: true,
            ..crate::types::Options::default()
        };
        e.apply_options(&new_opts);

        let after = e.current_options();
        assert_eq!(after.shiftwidth, 4);
        assert_eq!(after.tabstop, 2);
        assert!(after.ignorecase);
    }

    #[test]
    fn selection_highlight_none_in_normal() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello");
        assert!(e.selection_highlight().is_none());
    }

    #[test]
    fn highlights_emit_search_matches() {
        use crate::types::HighlightKind;
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("foo bar foo\nbaz qux\n");
        // 0.0.35: arm via the engine search state. The buffer
        // accessor still works (deprecated) but new code goes
        // through Editor.
        e.set_search_pattern(Some(regex::Regex::new("foo").unwrap()));
        let hs = e.highlights_for_line(0);
        assert_eq!(hs.len(), 2);
        for h in &hs {
            assert_eq!(h.kind, HighlightKind::SearchMatch);
            assert_eq!(h.range.start.line, 0);
            assert_eq!(h.range.end.line, 0);
        }
    }

    #[test]
    fn highlights_empty_without_pattern() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("foo bar");
        assert!(e.highlights_for_line(0).is_empty());
    }

    #[test]
    fn highlights_empty_for_out_of_range_line() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("foo");
        e.set_search_pattern(Some(regex::Regex::new("foo").unwrap()));
        assert!(e.highlights_for_line(99).is_empty());
    }

    #[test]
    fn snapshot_roundtrips_through_restore() {
        use crate::types::SnapshotMode;
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("alpha\nbeta\ngamma");
        e.jump_cursor(2, 3);
        let snap = e.take_snapshot();
        assert_eq!(snap.mode, SnapshotMode::Normal);
        assert_eq!(snap.cursor, (2, 3));
        assert_eq!(snap.lines.len(), 3);

        let mut other = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        other.restore_snapshot(snap).expect("restore");
        assert_eq!(other.cursor(), (2, 3));
        assert_eq!(other.buffer().lines().len(), 3);
    }

    #[test]
    fn restore_snapshot_rejects_version_mismatch() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        let mut snap = e.take_snapshot();
        snap.version = 9999;
        match e.restore_snapshot(snap) {
            Err(crate::EngineError::SnapshotVersion(got, want)) => {
                assert_eq!(got, 9999);
                assert_eq!(want, crate::types::EditorSnapshot::VERSION);
            }
            other => panic!("expected SnapshotVersion err, got {other:?}"),
        }
    }

    #[test]
    fn take_content_change_returns_some_on_first_dirty() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello");
        let first = e.take_content_change();
        assert!(first.is_some());
        let second = e.take_content_change();
        assert!(second.is_none());
    }

    fn many_lines(n: usize) -> String {
        (0..n)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n")
    }

    #[allow(dead_code)]
    fn prime_viewport<H: Host>(e: &mut Editor<hjkl_buffer::Buffer, H>, height: u16) {
        e.set_viewport_height(height);
    }

    /// Contract that the TUI drain relies on: `set_content` flags the
    /// editor dirty (so the next `take_dirty` call reports the change),
    /// and a second `take_dirty` returns `false` after consumption. The
    /// TUI drains this flag after every programmatic content load so
    /// opening a tab doesn't get mistaken for a user edit and mark the
    /// tab dirty (which would then trigger the quit-prompt on `:q`).
    #[test]
    fn set_content_dirties_then_take_dirty_clears() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello");
        assert!(
            e.take_dirty(),
            "set_content should leave content_dirty=true"
        );
        assert!(!e.take_dirty(), "take_dirty should clear the flag");
    }

    #[test]
    fn content_arc_cache_invalidated_by_set_content() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("one");
        let a = e.content_arc();
        e.set_content("two");
        let b = e.content_arc();
        assert!(!std::sync::Arc::ptr_eq(&a, &b));
        assert!(b.starts_with("two"));
    }

    // ── doc-coord mouse primitives (Phase 1 — issue #114) ──────────────────

    #[test]
    fn mouse_click_doc_moves_cursor_to_doc_coords() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello\nworld");
        e.mouse_click_doc(1, 2);
        assert_eq!(e.cursor(), (1, 2));
    }

    #[test]
    fn mouse_click_doc_normal_mode_clamps_past_eol_to_last_char() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello");
        // Normal mode (default after construction): "hello" has 5 chars,
        // past-EOL click clamps to col=4 (last char 'o' — never on the
        // implicit \n, vim/neovim convention).
        e.mouse_click_doc(0, 99);
        assert_eq!(e.cursor(), (0, 4));
    }

    #[test]
    fn mouse_click_doc_normal_mode_clamps_past_eol_multibyte() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        // 5 chars, 6 bytes — clamping must be char-counted, not byte-counted.
        e.set_content("héllo");
        e.mouse_click_doc(0, 99);
        assert_eq!(e.cursor(), (0, 4));
    }

    #[test]
    fn mouse_click_doc_insert_mode_allows_one_past_eol() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello");
        e.enter_insert_i(1);
        // Insert mode allows the one-past-EOL position (col=5 for 5-char
        // line) — that's the canonical insert-here sentinel.
        e.mouse_click_doc(0, 99);
        assert_eq!(e.cursor(), (0, 5));
    }

    #[test]
    fn mouse_click_doc_resets_sticky_col() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("aaaaa\nbb\naaaaa");
        // Pretend a previous keyboard motion put intended col at 4 (e.g.
        // user navigated $ on row 0).
        e.sticky_col = Some(4);
        // Click on row 1, col 1 (the second 'b' on a short line).
        e.mouse_click_doc(1, 1);
        assert_eq!(e.cursor(), (1, 1));
        assert_eq!(
            e.sticky_col,
            Some(1),
            "click must reset sticky_col so a subsequent j/k uses the clicked column \
             as the intended visual column (not the previous keyboard-tracked col)"
        );
    }

    #[test]
    fn mouse_click_doc_exits_visual_mode() {
        use crate::VimMode;
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello");
        e.enter_visual_char();
        assert_eq!(e.vim_mode(), VimMode::Visual);
        e.mouse_click_doc(0, 2);
        assert_eq!(e.vim_mode(), VimMode::Normal);
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn set_cursor_doc_clamps_past_last_row() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("one\ntwo");
        // doc has 2 rows (0 and 1); row 99 clamps to 1.
        e.set_cursor_doc(99, 0);
        assert_eq!(e.cursor(), (1, 0));
    }

    #[test]
    fn mouse_begin_drag_enters_visual_char() {
        use crate::VimMode;
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello");
        e.mouse_begin_drag();
        assert_eq!(e.vim_mode(), VimMode::Visual);
    }

    #[test]
    fn mouse_extend_drag_doc_moves_cursor_leaving_visual_anchor() {
        use crate::VimMode;
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_content("hello world");
        e.mouse_begin_drag(); // anchor at (0,0)
        e.mouse_extend_drag_doc(0, 5);
        assert_eq!(e.vim_mode(), VimMode::Visual);
        assert_eq!(e.cursor(), (0, 5));
    }

    // ── Patch B (0.0.29): Host trait wired into Editor ──

    #[test]
    fn host_clipboard_round_trip_via_default_host() {
        // DefaultHost stores write_clipboard in-memory; read_clipboard
        // returns the most recent payload.
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.host_mut().write_clipboard("payload".to_string());
        assert_eq!(e.host_mut().read_clipboard().as_deref(), Some("payload"));
    }

    // ── ContentEdit emission ─────────────────────────────────────────

    fn fresh_editor(initial: &str) -> Editor {
        let buffer = hjkl_buffer::Buffer::from_str(initial);
        Editor::new(
            buffer,
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        )
    }

    #[test]
    fn content_edit_insert_char_at_origin() {
        let mut e = fresh_editor("");
        let _ = e.mutate_edit(hjkl_buffer::Edit::InsertChar {
            at: hjkl_buffer::Position::new(0, 0),
            ch: 'a',
        });
        let edits = e.take_content_edits();
        assert_eq!(edits.len(), 1);
        let ce = &edits[0];
        assert_eq!(ce.start_byte, 0);
        assert_eq!(ce.old_end_byte, 0);
        assert_eq!(ce.new_end_byte, 1);
        assert_eq!(ce.start_position, (0, 0));
        assert_eq!(ce.old_end_position, (0, 0));
        assert_eq!(ce.new_end_position, (0, 1));
    }

    #[test]
    fn content_edit_insert_str_multiline() {
        // Buffer "x\ny" — insert "ab\ncd" at end of row 0.
        let mut e = fresh_editor("x\ny");
        let _ = e.mutate_edit(hjkl_buffer::Edit::InsertStr {
            at: hjkl_buffer::Position::new(0, 1),
            text: "ab\ncd".into(),
        });
        let edits = e.take_content_edits();
        assert_eq!(edits.len(), 1);
        let ce = &edits[0];
        assert_eq!(ce.start_byte, 1);
        assert_eq!(ce.old_end_byte, 1);
        assert_eq!(ce.new_end_byte, 1 + 5);
        assert_eq!(ce.start_position, (0, 1));
        // Insertion contains one '\n', so row+1, col = bytes after last '\n' = 2.
        assert_eq!(ce.new_end_position, (1, 2));
    }

    #[test]
    fn content_edit_delete_range_charwise() {
        // "abcdef" — delete chars 1..4 ("bcd").
        let mut e = fresh_editor("abcdef");
        let _ = e.mutate_edit(hjkl_buffer::Edit::DeleteRange {
            start: hjkl_buffer::Position::new(0, 1),
            end: hjkl_buffer::Position::new(0, 4),
            kind: hjkl_buffer::MotionKind::Char,
        });
        let edits = e.take_content_edits();
        assert_eq!(edits.len(), 1);
        let ce = &edits[0];
        assert_eq!(ce.start_byte, 1);
        assert_eq!(ce.old_end_byte, 4);
        assert_eq!(ce.new_end_byte, 1);
        assert!(ce.old_end_byte > ce.new_end_byte);
    }

    #[test]
    fn content_edit_set_content_resets() {
        let mut e = fresh_editor("foo");
        let _ = e.mutate_edit(hjkl_buffer::Edit::InsertChar {
            at: hjkl_buffer::Position::new(0, 0),
            ch: 'X',
        });
        // set_content should clear queued edits and raise the reset
        // flag on the next take_content_reset.
        e.set_content("brand new");
        assert!(e.take_content_reset());
        // Subsequent call clears the flag.
        assert!(!e.take_content_reset());
        // Edits cleared on reset.
        assert!(e.take_content_edits().is_empty());
    }

    #[test]
    fn content_edit_multiple_replaces_in_order() {
        // Three Replace edits applied left-to-right (mimics the
        // substitute path's per-match Replace fan-out). Verify each
        // mutation queues exactly one ContentEdit and they're drained
        // in source-order with structurally valid byte spans.
        let mut e = fresh_editor("xax xbx xcx");
        let _ = e.take_content_edits();
        let _ = e.take_content_reset();
        // Replace each "x" with "yy", left to right. After each replace,
        // the next match's char-col shifts by +1 (since "yy" is 1 char
        // longer than "x" but they're both ASCII so byte = char here).
        let positions = [(0usize, 0usize), (0, 4), (0, 8)];
        for (row, col) in positions {
            let _ = e.mutate_edit(hjkl_buffer::Edit::Replace {
                start: hjkl_buffer::Position::new(row, col),
                end: hjkl_buffer::Position::new(row, col + 1),
                with: "yy".into(),
            });
        }
        let edits = e.take_content_edits();
        assert_eq!(edits.len(), 3);
        for ce in &edits {
            assert!(ce.start_byte <= ce.old_end_byte);
            assert!(ce.start_byte <= ce.new_end_byte);
        }
        // Document order.
        for w in edits.windows(2) {
            assert!(w[0].start_byte <= w[1].start_byte);
        }
    }

    #[test]
    fn replace_char_at_replaces_single_char_under_cursor() {
        // Matches vim's `rx` semantics: replace char under cursor.
        let mut e = fresh_editor("abc");
        e.jump_cursor(0, 1); // cursor on 'b'
        e.replace_char_at('X', 1);
        let got = e.content();
        let got = got.trim_end_matches('\n');
        assert_eq!(
            got, "aXc",
            "replace_char_at(X, 1) must replace 'b' with 'X'"
        );
        // Cursor stays on the replaced char.
        assert_eq!(e.cursor(), (0, 1));
    }

    #[test]
    fn replace_char_at_count_replaces_multiple_chars() {
        // `3rx` in vim replaces 3 chars starting at cursor.
        let mut e = fresh_editor("abcde");
        e.jump_cursor(0, 0);
        e.replace_char_at('Z', 3);
        let got = e.content();
        let got = got.trim_end_matches('\n');
        assert_eq!(
            got, "ZZZde",
            "replace_char_at(Z, 3) must replace first 3 chars"
        );
    }

    #[test]
    fn find_char_method_moves_to_target() {
        // buffer "abcabc", cursor (0,0), f<c> → cursor (0,2).
        let mut e = fresh_editor("abcabc");
        e.jump_cursor(0, 0);
        e.find_char('c', true, false, 1);
        assert_eq!(
            e.cursor(),
            (0, 2),
            "find_char('c', forward=true, till=false, count=1) must land on 'c' at col 2"
        );
    }

    // ── after_g unit tests (Phase 2b-ii) ────────────────────────────────────

    #[test]
    fn after_g_gg_jumps_to_top() {
        let content: String = (0..20).map(|i| format!("line {i}\n")).collect();
        let mut e = fresh_editor(&content);
        e.jump_cursor(15, 0);
        e.after_g('g', 1);
        assert_eq!(e.cursor().0, 0, "gg must move cursor to row 0");
    }

    #[test]
    fn after_g_gg_with_count_jumps_line() {
        // 5gg → row 4 (0-indexed).
        let content: String = (0..20).map(|i| format!("line {i}\n")).collect();
        let mut e = fresh_editor(&content);
        e.jump_cursor(0, 0);
        e.after_g('g', 5);
        assert_eq!(e.cursor().0, 4, "5gg must land on row 4");
    }

    #[test]
    fn after_g_gj_moves_down() {
        let mut e = fresh_editor("line0\nline1\nline2\n");
        e.jump_cursor(0, 0);
        e.after_g('j', 1);
        assert_eq!(e.cursor().0, 1, "gj must move down one display row");
    }

    #[test]
    fn after_g_gu_sets_operator_pending() {
        // gU enters operator-pending with Uppercase op; next key applies it.
        let mut e = fresh_editor("hello\n");
        e.after_g('U', 1);
        // The engine should now be chord-pending (Pending::Op set).
        assert!(
            e.is_chord_pending(),
            "gU must set engine chord-pending (Pending::Op)"
        );
    }

    #[test]
    fn after_g_g_star_searches_forward_non_whole_word() {
        // g* on word "foo" in "foobar" should find the match.
        let mut e = fresh_editor("foo foobar\n");
        e.jump_cursor(0, 0); // cursor on 'f' of "foo"
        e.after_g('*', 1);
        // After g* the cursor should have moved (ScreenDown motion is
        // not applicable here; WordAtCursor forward moves to next match).
        // At minimum: no panic and mode stays Normal.
        assert_eq!(e.vim_mode(), VimMode::Normal, "g* must stay in Normal mode");
    }

    // ── apply_motion controller tests (Phase 3a) ────────────────────────────

    #[test]
    fn apply_motion_char_left_moves_cursor() {
        let mut e = fresh_editor("hello\n");
        e.jump_cursor(0, 3);
        e.apply_motion(crate::MotionKind::CharLeft, 1);
        assert_eq!(e.cursor(), (0, 2), "CharLeft moves one col left");
    }

    #[test]
    fn apply_motion_char_left_clamps_at_col_zero() {
        let mut e = fresh_editor("hello\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::CharLeft, 1);
        assert_eq!(e.cursor(), (0, 0), "CharLeft at col 0 must not wrap");
    }

    #[test]
    fn apply_motion_char_left_with_count() {
        let mut e = fresh_editor("hello\n");
        e.jump_cursor(0, 4);
        e.apply_motion(crate::MotionKind::CharLeft, 3);
        assert_eq!(e.cursor(), (0, 1), "CharLeft count=3 moves three cols left");
    }

    #[test]
    fn apply_motion_char_right_moves_cursor() {
        let mut e = fresh_editor("hello\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::CharRight, 1);
        assert_eq!(e.cursor(), (0, 1), "CharRight moves one col right");
    }

    #[test]
    fn apply_motion_char_right_clamps_at_last_char() {
        let mut e = fresh_editor("hello\n");
        // "hello" has chars at 0..=4; normal mode clamps at 4.
        e.jump_cursor(0, 4);
        e.apply_motion(crate::MotionKind::CharRight, 1);
        assert_eq!(
            e.cursor(),
            (0, 4),
            "CharRight at end must not go past last char"
        );
    }

    #[test]
    fn apply_motion_line_down_moves_cursor() {
        let mut e = fresh_editor("line0\nline1\nline2\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::LineDown, 1);
        assert_eq!(e.cursor().0, 1, "LineDown moves one row down");
    }

    #[test]
    fn apply_motion_line_down_with_count() {
        let mut e = fresh_editor("line0\nline1\nline2\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::LineDown, 2);
        assert_eq!(e.cursor().0, 2, "LineDown count=2 moves two rows down");
    }

    #[test]
    fn apply_motion_line_up_moves_cursor() {
        let mut e = fresh_editor("line0\nline1\nline2\n");
        e.jump_cursor(2, 0);
        e.apply_motion(crate::MotionKind::LineUp, 1);
        assert_eq!(e.cursor().0, 1, "LineUp moves one row up");
    }

    #[test]
    fn apply_motion_line_up_clamps_at_top() {
        let mut e = fresh_editor("line0\nline1\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::LineUp, 1);
        assert_eq!(e.cursor().0, 0, "LineUp at top must not go negative");
    }

    #[test]
    fn apply_motion_first_non_blank_down_moves_and_lands_on_non_blank() {
        // Line 0: "  hello" (indent 2), line 1: "  world" (indent 2).
        let mut e = fresh_editor("  hello\n  world\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::FirstNonBlankDown, 1);
        assert_eq!(e.cursor().0, 1, "FirstNonBlankDown must move to next row");
        assert_eq!(
            e.cursor().1,
            2,
            "FirstNonBlankDown must land on first non-blank col"
        );
    }

    #[test]
    fn apply_motion_first_non_blank_up_moves_and_lands_on_non_blank() {
        let mut e = fresh_editor("  hello\n  world\n");
        e.jump_cursor(1, 4);
        e.apply_motion(crate::MotionKind::FirstNonBlankUp, 1);
        assert_eq!(e.cursor().0, 0, "FirstNonBlankUp must move to prev row");
        assert_eq!(
            e.cursor().1,
            2,
            "FirstNonBlankUp must land on first non-blank col"
        );
    }

    #[test]
    fn apply_motion_count_zero_treated_as_one() {
        // count=0 must be normalised to 1 (count.max(1) in apply_motion_kind).
        let mut e = fresh_editor("hello\n");
        e.jump_cursor(0, 3);
        e.apply_motion(crate::MotionKind::CharLeft, 0);
        assert_eq!(e.cursor(), (0, 2), "count=0 treated as 1 for CharLeft");
    }

    // ── apply_motion controller tests (Phase 3b) — word motions ─────────────

    #[test]
    fn apply_motion_word_forward_moves_to_next_word() {
        // "hello world\n": 'w' from col 0 lands on 'w' of "world" at col 6.
        let mut e = fresh_editor("hello world\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::WordForward, 1);
        assert_eq!(
            e.cursor(),
            (0, 6),
            "WordForward moves to start of next word"
        );
    }

    #[test]
    fn apply_motion_word_forward_with_count() {
        // "one two three\n": 2w from col 0 → start of "three" at col 8.
        let mut e = fresh_editor("one two three\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::WordForward, 2);
        assert_eq!(e.cursor(), (0, 8), "WordForward count=2 skips two words");
    }

    #[test]
    fn apply_motion_big_word_forward_moves_to_next_big_word() {
        // "foo.bar baz\n": W from col 0 skips entire "foo.bar" (one WORD) to 'b' at col 8.
        let mut e = fresh_editor("foo.bar baz\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::BigWordForward, 1);
        assert_eq!(e.cursor(), (0, 8), "BigWordForward skips the whole WORD");
    }

    #[test]
    fn apply_motion_big_word_forward_with_count() {
        // "aa bb cc\n": 2W from col 0 → start of "cc" at col 6.
        let mut e = fresh_editor("aa bb cc\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::BigWordForward, 2);
        assert_eq!(e.cursor(), (0, 6), "BigWordForward count=2 skips two WORDs");
    }

    #[test]
    fn apply_motion_word_backward_moves_to_prev_word() {
        // "hello world\n": 'b' from col 6 ('w') lands back at col 0 ('h').
        let mut e = fresh_editor("hello world\n");
        e.jump_cursor(0, 6);
        e.apply_motion(crate::MotionKind::WordBackward, 1);
        assert_eq!(
            e.cursor(),
            (0, 0),
            "WordBackward moves to start of prev word"
        );
    }

    #[test]
    fn apply_motion_word_backward_with_count() {
        // "one two three\n": 2b from col 8 ('t' of "three") → col 0 ('o' of "one").
        let mut e = fresh_editor("one two three\n");
        e.jump_cursor(0, 8);
        e.apply_motion(crate::MotionKind::WordBackward, 2);
        assert_eq!(
            e.cursor(),
            (0, 0),
            "WordBackward count=2 skips two words back"
        );
    }

    #[test]
    fn apply_motion_big_word_backward_moves_to_prev_big_word() {
        // "foo.bar baz\n": B from col 8 ('b' of "baz") → col 0 (start of "foo.bar" WORD).
        let mut e = fresh_editor("foo.bar baz\n");
        e.jump_cursor(0, 8);
        e.apply_motion(crate::MotionKind::BigWordBackward, 1);
        assert_eq!(
            e.cursor(),
            (0, 0),
            "BigWordBackward jumps to start of prev WORD"
        );
    }

    #[test]
    fn apply_motion_big_word_backward_with_count() {
        // "aa bb cc\n": 2B from col 6 ('c') → col 0 ('a').
        let mut e = fresh_editor("aa bb cc\n");
        e.jump_cursor(0, 6);
        e.apply_motion(crate::MotionKind::BigWordBackward, 2);
        assert_eq!(
            e.cursor(),
            (0, 0),
            "BigWordBackward count=2 skips two WORDs back"
        );
    }

    #[test]
    fn apply_motion_word_end_moves_to_end_of_word() {
        // "hello world\n": 'e' from col 0 lands on 'o' of "hello" at col 4.
        let mut e = fresh_editor("hello world\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::WordEnd, 1);
        assert_eq!(e.cursor(), (0, 4), "WordEnd moves to end of current word");
    }

    #[test]
    fn apply_motion_word_end_with_count() {
        // "one two three\n": 2e from col 0 → end of "two" at col 6.
        let mut e = fresh_editor("one two three\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::WordEnd, 2);
        assert_eq!(
            e.cursor(),
            (0, 6),
            "WordEnd count=2 lands on end of second word"
        );
    }

    #[test]
    fn apply_motion_big_word_end_moves_to_end_of_big_word() {
        // "foo.bar baz\n": E from col 0 → end of "foo.bar" WORD at col 6.
        let mut e = fresh_editor("foo.bar baz\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::BigWordEnd, 1);
        assert_eq!(e.cursor(), (0, 6), "BigWordEnd lands on end of WORD");
    }

    #[test]
    fn apply_motion_big_word_end_with_count() {
        // "aa bb cc\n": 2E from col 0 → end of "bb" at col 4.
        let mut e = fresh_editor("aa bb cc\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::BigWordEnd, 2);
        assert_eq!(
            e.cursor(),
            (0, 4),
            "BigWordEnd count=2 lands on end of second WORD"
        );
    }

    // ── apply_motion controller tests (Phase 3c) — line-anchor motions ────────

    #[test]
    fn apply_motion_line_start_lands_at_col_zero() {
        // "  foo bar  \n": `0` from col 5 → col 0 unconditionally.
        let mut e = fresh_editor("  foo bar  \n");
        e.jump_cursor(0, 5);
        e.apply_motion(crate::MotionKind::LineStart, 1);
        assert_eq!(e.cursor(), (0, 0), "LineStart lands at col 0");
    }

    #[test]
    fn apply_motion_line_start_from_beginning_stays_at_col_zero() {
        // Already at col 0 — motion is a no-op but must not panic.
        let mut e = fresh_editor("  foo bar  \n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::LineStart, 1);
        assert_eq!(e.cursor(), (0, 0), "LineStart from col 0 stays at col 0");
    }

    #[test]
    fn apply_motion_first_non_blank_lands_on_first_non_blank() {
        // "  foo bar  \n": `^` from col 0 → col 2 ('f').
        let mut e = fresh_editor("  foo bar  \n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::FirstNonBlank, 1);
        assert_eq!(
            e.cursor(),
            (0, 2),
            "FirstNonBlank lands on first non-blank char"
        );
    }

    #[test]
    fn apply_motion_first_non_blank_on_blank_line_lands_at_zero() {
        // "   \n": all whitespace — `^` must land at col 0.
        let mut e = fresh_editor("   \n");
        e.jump_cursor(0, 2);
        e.apply_motion(crate::MotionKind::FirstNonBlank, 1);
        assert_eq!(
            e.cursor(),
            (0, 0),
            "FirstNonBlank on blank line stays at col 0"
        );
    }

    #[test]
    fn apply_motion_line_end_lands_on_last_char() {
        // "  foo bar  \n": last char is the second space at col 10.
        let mut e = fresh_editor("  foo bar  \n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::LineEnd, 1);
        assert_eq!(e.cursor(), (0, 10), "LineEnd lands on last char of line");
    }

    #[test]
    fn apply_motion_line_end_on_empty_line_stays_at_zero() {
        // "\n": empty line — `$` must stay at col 0.
        let mut e = fresh_editor("\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::LineEnd, 1);
        assert_eq!(e.cursor(), (0, 0), "LineEnd on empty line stays at col 0");
    }

    // ── apply_motion controller tests (Phase 3d) — doc-level motion ───────────

    #[test]
    fn goto_line_count_1_lands_on_last_line() {
        // "foo\nbar\nbaz\n": bare `G` (count=1) → last content line (row 2).
        // Count convention: apply_motion_kind normalises 1 → execute_motion
        // with count=1 → FileBottom arm sees count <= 1 → move_bottom(0) =
        // last content row.
        let mut e = fresh_editor("foo\nbar\nbaz\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::GotoLine, 1);
        assert_eq!(e.cursor(), (2, 0), "bare G lands on last content row");
    }

    #[test]
    fn goto_line_count_5_lands_on_line_5() {
        // 6-line buffer (rows 0-5); `5G` → row 4 (1-based line 5).
        let mut e = fresh_editor("a\nb\nc\nd\ne\nf\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::GotoLine, 5);
        assert_eq!(e.cursor(), (4, 0), "5G lands on row 4 (1-based line 5)");
    }

    #[test]
    fn goto_line_count_past_buffer_clamps_to_last_line() {
        // "foo\nbar\nbaz\n": `100G` → last content line (row 2), clamped.
        let mut e = fresh_editor("foo\nbar\nbaz\n");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::GotoLine, 100);
        assert_eq!(e.cursor(), (2, 0), "100G clamps to last content row");
    }

    // ── FindRepeat / FindRepeatReverse controller tests (Phase 3e) ────────────

    #[test]
    fn find_repeat_after_f_finds_next_occurrence() {
        // "abcabc", cursor at (0,0). `fc` lands on (0,2). `;` repeats → (0,5).
        let mut e = fresh_editor("abcabc");
        e.jump_cursor(0, 0);
        e.find_char('c', true, false, 1);
        assert_eq!(e.cursor(), (0, 2), "fc must land on first 'c'");
        e.apply_motion(crate::MotionKind::FindRepeat, 1);
        assert_eq!(
            e.cursor(),
            (0, 5),
            "find_repeat (;) must advance to second 'c'"
        );
    }

    #[test]
    fn find_repeat_reverse_after_f_finds_prev_occurrence() {
        // "abcabc", cursor at (0,0). `fc` lands on (0,2). `;` → (0,5). `,` back → (0,2).
        let mut e = fresh_editor("abcabc");
        e.jump_cursor(0, 0);
        e.find_char('c', true, false, 1);
        assert_eq!(e.cursor(), (0, 2), "fc must land on first 'c'");
        e.apply_motion(crate::MotionKind::FindRepeat, 1);
        assert_eq!(e.cursor(), (0, 5), "; must advance to second 'c'");
        e.apply_motion(crate::MotionKind::FindRepeatReverse, 1);
        assert_eq!(
            e.cursor(),
            (0, 2),
            "find_repeat_reverse (,) must go back to first 'c'"
        );
    }

    #[test]
    fn find_repeat_with_no_prior_find_is_noop() {
        // Fresh editor, no prior find — `;` must not move cursor.
        let mut e = fresh_editor("abcabc");
        e.jump_cursor(0, 3);
        e.apply_motion(crate::MotionKind::FindRepeat, 1);
        assert_eq!(
            e.cursor(),
            (0, 3),
            "find_repeat with no prior find must be a no-op"
        );
    }

    #[test]
    fn find_repeat_with_count_advances_count_times() {
        // "aXaXaX", cursor (0,0). `fX` → (0,1). `3;` → repeats 3× → (0,5).
        let mut e = fresh_editor("aXaXaX");
        e.jump_cursor(0, 0);
        e.find_char('X', true, false, 1);
        assert_eq!(e.cursor(), (0, 1), "fX must land on first 'X' at col 1");
        e.apply_motion(crate::MotionKind::FindRepeat, 3);
        assert_eq!(
            e.cursor(),
            (0, 5),
            "3; must advance 3 times from col 1 to col 5"
        );
    }

    // ── BracketMatch controller tests (Phase 3f) ───────────────────────────────

    #[test]
    fn bracket_match_jumps_to_matching_close_paren() {
        // "(abc)", cursor at (0,0) on `(` — `%` must jump to `)` at (0,4).
        let mut e = fresh_editor("(abc)");
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::BracketMatch, 1);
        assert_eq!(
            e.cursor(),
            (0, 4),
            "% on '(' must land on matching ')' at col 4"
        );
    }

    #[test]
    fn bracket_match_jumps_to_matching_open_paren() {
        // "(abc)", cursor at (0,4) on `)` — `%` must jump back to `(` at (0,0).
        let mut e = fresh_editor("(abc)");
        e.jump_cursor(0, 4);
        e.apply_motion(crate::MotionKind::BracketMatch, 1);
        assert_eq!(
            e.cursor(),
            (0, 0),
            "% on ')' must land on matching '(' at col 0"
        );
    }

    #[test]
    fn bracket_match_with_no_match_on_line_is_noop_or_engine_behaviour() {
        // "abcd", cursor at (0,2) — no bracket under cursor; engine returns
        // false from matching_bracket, cursor must not move.
        let mut e = fresh_editor("abcd");
        e.jump_cursor(0, 2);
        e.apply_motion(crate::MotionKind::BracketMatch, 1);
        assert_eq!(
            e.cursor(),
            (0, 2),
            "% with no bracket under cursor must be a no-op"
        );
    }

    // ── Scroll / viewport motion controller tests (Phase 3g) ──────────────────

    /// Helper: build a 20-line buffer, set viewport to rows [5..14] (height=10).
    fn fresh_viewport_editor() -> Editor {
        let content = many_lines(20);
        let mut e = Editor::new(
            hjkl_buffer::Buffer::from_str(&content),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        // height=10, top_row=5 → visible rows 5..14.
        // set_viewport_height stores to the atomic; sync_buffer_from_textarea
        // propagates it to host.viewport_mut().height so motion helpers see it.
        e.set_viewport_height(10);
        e.sync_buffer_from_textarea();
        e.host_mut().viewport_mut().top_row = 5;
        e
    }

    #[test]
    fn viewport_top_lands_on_first_visible_row() {
        // Viewport top=5, height=10. H (count=1) should land on row 5
        // (the first visible row, offset = count-1 = 0).
        let mut e = fresh_viewport_editor();
        e.jump_cursor(10, 0);
        e.apply_motion(crate::MotionKind::ViewportTop, 1);
        assert_eq!(
            e.cursor().0,
            5,
            "H (count=1) must land on viewport top row (5)"
        );
    }

    #[test]
    fn viewport_top_with_count_offsets_down() {
        // H with count=3 → viewport top + (3-1) = 5 + 2 = row 7.
        let mut e = fresh_viewport_editor();
        e.jump_cursor(12, 0);
        e.apply_motion(crate::MotionKind::ViewportTop, 3);
        assert_eq!(e.cursor().0, 7, "3H must land at viewport top + 2 = row 7");
    }

    #[test]
    fn viewport_middle_lands_on_middle_visible_row() {
        // Viewport top=5, height=10 → last visible = 14, mid = 5 + (14-5)/2 = 9.
        let mut e = fresh_viewport_editor();
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::ViewportMiddle, 1);
        assert_eq!(e.cursor().0, 9, "M must land on middle visible row (9)");
    }

    #[test]
    fn viewport_bottom_lands_on_last_visible_row() {
        // L (count=1) → viewport bottom, offset = count-1 = 0 → row 14.
        let mut e = fresh_viewport_editor();
        e.jump_cursor(5, 0);
        e.apply_motion(crate::MotionKind::ViewportBottom, 1);
        assert_eq!(
            e.cursor().0,
            14,
            "L (count=1) must land on viewport bottom row (14)"
        );
    }

    #[test]
    fn half_page_down_moves_cursor_by_half_window() {
        // viewport height=10, so half=5. Cursor at row 0 → row 5 after C-d.
        let mut e = Editor::new(
            hjkl_buffer::Buffer::from_str(&many_lines(30)),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_viewport_height(10);
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::HalfPageDown, 1);
        assert_eq!(
            e.cursor().0,
            5,
            "<C-d> from row 0 with viewport height=10 must land on row 5"
        );
    }

    #[test]
    fn half_page_up_moves_cursor_by_half_window_reverse() {
        // viewport height=10, half=5. Cursor at row 10 → row 5 after C-u.
        let mut e = Editor::new(
            hjkl_buffer::Buffer::from_str(&many_lines(30)),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_viewport_height(10);
        e.jump_cursor(10, 0);
        e.apply_motion(crate::MotionKind::HalfPageUp, 1);
        assert_eq!(
            e.cursor().0,
            5,
            "<C-u> from row 10 with viewport height=10 must land on row 5"
        );
    }

    #[test]
    fn full_page_down_moves_cursor_by_full_window() {
        // viewport height=10, full = 10 - 2 = 8. Cursor at row 0 → row 8.
        let mut e = Editor::new(
            hjkl_buffer::Buffer::from_str(&many_lines(30)),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_viewport_height(10);
        e.jump_cursor(0, 0);
        e.apply_motion(crate::MotionKind::FullPageDown, 1);
        assert_eq!(
            e.cursor().0,
            8,
            "<C-f> from row 0 with viewport height=10 must land on row 8"
        );
    }

    #[test]
    fn full_page_up_moves_cursor_by_full_window_reverse() {
        // viewport height=10, full=8. Cursor at row 10 → row 2.
        let mut e = Editor::new(
            hjkl_buffer::Buffer::from_str(&many_lines(30)),
            crate::types::DefaultHost::new(),
            crate::types::Options::default(),
        );
        e.set_viewport_height(10);
        e.jump_cursor(10, 0);
        e.apply_motion(crate::MotionKind::FullPageUp, 1);
        assert_eq!(
            e.cursor().0,
            2,
            "<C-b> from row 10 with viewport height=10 must land on row 2"
        );
    }

    // ── set_mark_at_cursor unit tests ─────────────────────────────────────────

    #[test]
    fn set_mark_at_cursor_alphabetic_records() {
        // `ma` at (0, 2) — mark 'a' must store (0, 2).
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 2);
        e.set_mark_at_cursor('a');
        assert_eq!(
            e.mark('a'),
            Some((0, 2)),
            "mark 'a' must record current pos"
        );
    }

    #[test]
    fn set_mark_at_cursor_invalid_char_no_op() {
        // Invalid chars (digits, special) must not store a mark.
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 1);
        e.set_mark_at_cursor('1'); // digit — not alphanumeric in vim mark sense
        assert_eq!(e.mark('1'), None, "digit mark must be a no-op");
        e.set_mark_at_cursor('['); // special — only goto uses '[', not set_mark
        assert_eq!(
            e.mark('['),
            None,
            "bracket char must be a no-op for set_mark"
        );
    }

    #[test]
    fn set_mark_at_cursor_special_left_bracket() {
        // Confirm '[' is NOT stored by set_mark_at_cursor (vim's `m[` is invalid).
        // The `[` mark is only set automatically by operator paths, not `m[`.
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 3);
        e.set_mark_at_cursor('[');
        assert_eq!(
            e.mark('['),
            None,
            "set_mark_at_cursor must reject '[' (vim: m[ is invalid)"
        );
    }

    // ── goto_mark_line unit tests ─────────────────────────────────────────────

    #[test]
    fn goto_mark_line_jumps_to_first_non_blank() {
        // Set mark 'a' at (1, 3), then jump back to (0, 0).
        // `'a` (linewise) must land on row 1, first non-blank column.
        let mut e = fresh_editor("hello\n  world\n");
        e.jump_cursor(1, 3);
        e.set_mark_at_cursor('a');
        e.jump_cursor(0, 0);
        e.goto_mark_line('a');
        assert_eq!(e.cursor().0, 1, "goto_mark_line must jump to mark row");
        // "  world" — first non-blank is col 2.
        assert_eq!(
            e.cursor().1,
            2,
            "goto_mark_line must land on first non-blank column"
        );
    }

    #[test]
    fn goto_mark_line_unset_mark_no_op() {
        // Jumping to an unset mark must not move the cursor.
        let mut e = fresh_editor("hello\nworld\n");
        e.jump_cursor(1, 2);
        e.goto_mark_line('z'); // 'z' not set
        assert_eq!(e.cursor(), (1, 2), "unset mark jump must be a no-op");
    }

    #[test]
    fn goto_mark_line_invalid_char_no_op() {
        // '!' is not a valid mark char — must not move cursor.
        let mut e = fresh_editor("hello\nworld\n");
        e.jump_cursor(0, 0);
        e.goto_mark_line('!');
        assert_eq!(e.cursor(), (0, 0), "invalid mark char must be a no-op");
    }

    // ── goto_mark_char unit tests ─────────────────────────────────────────────

    #[test]
    fn goto_mark_char_jumps_to_exact_pos() {
        // Set mark 'b' at (1, 4), then jump back to (0, 0).
        // `` `b `` (charwise) must land on (1, 4) exactly.
        let mut e = fresh_editor("hello\nworld\n");
        e.jump_cursor(1, 4);
        e.set_mark_at_cursor('b');
        e.jump_cursor(0, 0);
        e.goto_mark_char('b');
        assert_eq!(
            e.cursor(),
            (1, 4),
            "goto_mark_char must jump to exact mark position"
        );
    }

    #[test]
    fn goto_mark_char_unset_mark_no_op() {
        // Jumping to an unset mark must not move the cursor.
        let mut e = fresh_editor("hello\nworld\n");
        e.jump_cursor(1, 1);
        e.goto_mark_char('x'); // 'x' not set
        assert_eq!(
            e.cursor(),
            (1, 1),
            "unset charwise mark jump must be a no-op"
        );
    }

    #[test]
    fn goto_mark_char_invalid_char_no_op() {
        // '#' is not a valid mark char — must not move cursor.
        let mut e = fresh_editor("hello\nworld\n");
        e.jump_cursor(0, 2);
        e.goto_mark_char('#');
        assert_eq!(
            e.cursor(),
            (0, 2),
            "invalid charwise mark char must be a no-op"
        );
    }

    // ── Macro controller API tests (Phase 5b) ─────────────────────────────────

    #[test]
    fn start_macro_record_records_register() {
        let mut e = fresh_editor("hello");
        assert!(!e.is_recording_macro());
        e.start_macro_record('a');
        assert!(e.is_recording_macro());
        assert_eq!(e.recording_register(), Some('a'));
    }

    #[test]
    fn start_macro_record_capital_seeds_existing() {
        // `qa` records "h", stop. Then `qA` should seed from existing 'a' reg.
        let mut e = fresh_editor("hello");
        e.start_macro_record('a');
        e.record_input(crate::input::Input {
            key: crate::input::Key::Char('h'),
            ..Default::default()
        });
        e.stop_macro_record();
        // Start capital 'A' — should seed from existing 'a' register.
        e.start_macro_record('A');
        // recording_keys should now contain 1 input (the seeded 'h').
        assert_eq!(
            e.vim.recording_keys.len(),
            1,
            "capital record must seed from existing lowercase reg"
        );
    }

    #[test]
    fn stop_macro_record_writes_register() {
        let mut e = fresh_editor("hello");
        e.start_macro_record('a');
        e.record_input(crate::input::Input {
            key: crate::input::Key::Char('h'),
            ..Default::default()
        });
        e.record_input(crate::input::Input {
            key: crate::input::Key::Char('l'),
            ..Default::default()
        });
        e.stop_macro_record();
        assert!(!e.is_recording_macro());
        // Register 'a' should contain "hl".
        let text = e
            .registers()
            .read('a')
            .map(|s| s.text.clone())
            .unwrap_or_default();
        assert_eq!(
            text, "hl",
            "stop_macro_record must write encoded keys to register"
        );
    }

    #[test]
    fn is_recording_macro_reflects_state() {
        let mut e = fresh_editor("hello");
        assert!(!e.is_recording_macro());
        e.start_macro_record('b');
        assert!(e.is_recording_macro());
        e.stop_macro_record();
        assert!(!e.is_recording_macro());
    }

    #[test]
    fn play_macro_returns_decoded_inputs() {
        let mut e = fresh_editor("hello");
        // Write "jj" into register 'a'.
        e.set_named_register_text('a', "jj".to_string());
        let inputs = e.play_macro('a', 1);
        assert_eq!(inputs.len(), 2);
        assert_eq!(inputs[0].key, crate::input::Key::Char('j'));
        assert_eq!(inputs[1].key, crate::input::Key::Char('j'));
        assert!(e.is_replaying_macro(), "play_macro must set replaying flag");
        e.end_macro_replay();
        assert!(!e.is_replaying_macro());
    }

    #[test]
    fn play_macro_at_uses_last_macro() {
        let mut e = fresh_editor("hello");
        e.set_named_register_text('a', "k".to_string());
        // Play 'a' first to set last_macro.
        let _ = e.play_macro('a', 1);
        e.end_macro_replay();
        // Now `@@` should replay 'a' again.
        let inputs = e.play_macro('@', 1);
        assert_eq!(inputs.len(), 1);
        assert_eq!(inputs[0].key, crate::input::Key::Char('k'));
        e.end_macro_replay();
    }

    #[test]
    fn play_macro_with_count_repeats() {
        let mut e = fresh_editor("hello");
        e.set_named_register_text('a', "j".to_string());
        let inputs = e.play_macro('a', 3);
        assert_eq!(inputs.len(), 3, "3@a must produce 3 inputs");
        e.end_macro_replay();
    }

    #[test]
    fn record_input_appends_when_recording() {
        let mut e = fresh_editor("hello");
        // Not recording: record_input is a no-op.
        e.record_input(crate::input::Input {
            key: crate::input::Key::Char('j'),
            ..Default::default()
        });
        assert_eq!(e.vim.recording_keys.len(), 0);
        // Start recording: record_input appends.
        e.start_macro_record('a');
        e.record_input(crate::input::Input {
            key: crate::input::Key::Char('j'),
            ..Default::default()
        });
        e.record_input(crate::input::Input {
            key: crate::input::Key::Char('k'),
            ..Default::default()
        });
        assert_eq!(e.vim.recording_keys.len(), 2);
        // During replay: record_input must NOT append.
        e.vim.replaying_macro = true;
        e.record_input(crate::input::Input {
            key: crate::input::Key::Char('l'),
            ..Default::default()
        });
        assert_eq!(
            e.vim.recording_keys.len(),
            2,
            "record_input must skip during replay"
        );
        e.vim.replaying_macro = false;
        e.stop_macro_record();
    }

    // ── Phase 6.1 insert-mode primitive tests (kryptic-sh/hjkl#87) ────────────

    /// Helper: enter insert mode via the public bridge, then call the method under test.
    fn enter_insert(e: &mut Editor) {
        e.enter_insert_i(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
    }

    #[test]
    fn insert_char_basic() {
        let mut e = fresh_editor("hello");
        enter_insert(&mut e);
        e.insert_char('X');
        assert_eq!(e.buffer().lines()[0], "Xhello");
        assert!(e.take_dirty());
    }

    #[test]
    fn insert_newline_splits_line() {
        let mut e = fresh_editor("hello");
        // Move to col 3 so we split "hel" | "lo".
        e.jump_cursor(0, 3);
        enter_insert(&mut e);
        e.insert_newline();
        let lines = e.buffer().lines().to_vec();
        assert_eq!(lines[0], "hel");
        assert_eq!(lines[1], "lo");
    }

    #[test]
    fn insert_tab_expandtab_inserts_spaces() {
        let mut e = fresh_editor("");
        // Default options: expandtab=true, softtabstop=4, tabstop=4.
        enter_insert(&mut e);
        e.insert_tab();
        // At col 0 with sts=4: 4 spaces inserted.
        assert_eq!(e.buffer().lines()[0], "    ");
    }

    #[test]
    fn insert_tab_real_tab_when_noexpandtab() {
        let opts = crate::types::Options {
            expandtab: false,
            ..crate::types::Options::default()
        };
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            opts,
        );
        e.set_content("");
        enter_insert(&mut e);
        e.insert_tab();
        assert_eq!(e.buffer().lines()[0], "\t");
    }

    #[test]
    fn insert_backspace_single_char() {
        // Cursor at col 3 in "hello", backspace deletes 'l'.
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 3);
        enter_insert(&mut e);
        e.insert_backspace();
        assert_eq!(e.buffer().lines()[0], "helo");
    }

    #[test]
    fn insert_backspace_softtabstop() {
        // With sts=4, expandtab: 4 spaces at col 4 → one backspace deletes all 4.
        let mut e = fresh_editor("    hello");
        e.jump_cursor(0, 4);
        enter_insert(&mut e);
        e.insert_backspace();
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn insert_backspace_join_up() {
        // At col 0 on row 1, backspace joins with the previous line.
        let mut e = fresh_editor("foo\nbar");
        e.jump_cursor(1, 0);
        enter_insert(&mut e);
        e.insert_backspace();
        // Two rows merged into one.
        assert_eq!(e.buffer().lines().len(), 1);
        assert_eq!(e.buffer().lines()[0], "foobar");
    }

    #[test]
    fn leave_insert_steps_back_col() {
        // Esc in insert mode should move the cursor one cell left (vim convention).
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 3);
        enter_insert(&mut e);
        // Type one char so cursor is at col 4, then call leave_insert_to_normal.
        e.insert_char('X');
        // cursor is now at col 4 (after the inserted 'X').
        let pre_col = e.cursor().1;
        e.leave_insert_to_normal();
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
        // Cursor stepped back one.
        assert_eq!(e.cursor().1, pre_col - 1);
    }

    #[test]
    fn insert_ctrl_w_word_back() {
        // Ctrl-W deletes from cursor back to word start.
        // "hello world" — cursor at end of "world" (col 11).
        let mut e = fresh_editor("hello world");
        // Normal mode clamps cursor to col 10 (last char); jump_cursor doesn't clamp.
        e.jump_cursor(0, 11);
        enter_insert(&mut e);
        e.insert_ctrl_w();
        // "world" (5 chars) deleted, leaving "hello ".
        assert_eq!(e.buffer().lines()[0], "hello ");
    }

    #[test]
    fn insert_ctrl_u_deletes_to_line_start() {
        let mut e = fresh_editor("hello world");
        e.jump_cursor(0, 5);
        enter_insert(&mut e);
        e.insert_ctrl_u();
        assert_eq!(e.buffer().lines()[0], " world");
    }

    #[test]
    fn insert_ctrl_h_single_backspace() {
        // Ctrl-H is an alias for Backspace in insert mode.
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 3);
        enter_insert(&mut e);
        e.insert_ctrl_h();
        assert_eq!(e.buffer().lines()[0], "helo");
    }

    #[test]
    fn insert_ctrl_h_join_up() {
        let mut e = fresh_editor("foo\nbar");
        e.jump_cursor(1, 0);
        enter_insert(&mut e);
        e.insert_ctrl_h();
        assert_eq!(e.buffer().lines().len(), 1);
        assert_eq!(e.buffer().lines()[0], "foobar");
    }

    #[test]
    fn insert_ctrl_t_indents_current_line() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options {
                shiftwidth: 4,
                ..crate::types::Options::default()
            },
        );
        e.set_content("hello");
        enter_insert(&mut e);
        e.insert_ctrl_t();
        assert_eq!(e.buffer().lines()[0], "    hello");
    }

    #[test]
    fn insert_ctrl_d_outdents_current_line() {
        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options {
                shiftwidth: 4,
                ..crate::types::Options::default()
            },
        );
        e.set_content("    hello");
        enter_insert(&mut e);
        e.insert_ctrl_d();
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn insert_ctrl_o_arm_sets_one_shot_normal() {
        let mut e = fresh_editor("hello");
        enter_insert(&mut e);
        e.insert_ctrl_o_arm();
        // Mode should flip to Normal (one-shot).
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
    }

    #[test]
    fn insert_ctrl_r_arm_sets_pending_register() {
        let mut e = fresh_editor("hello");
        enter_insert(&mut e);
        e.insert_ctrl_r_arm();
        // pending register flag set; mode stays Insert.
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert!(e.vim.insert_pending_register);
    }

    #[test]
    fn insert_delete_removes_char_under_cursor() {
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 2);
        enter_insert(&mut e);
        e.insert_delete();
        assert_eq!(e.buffer().lines()[0], "helo");
    }

    #[test]
    fn insert_delete_joins_lines_at_eol() {
        let mut e = fresh_editor("foo\nbar");
        // Position at end of row 0 (col 3 = past last char).
        e.jump_cursor(0, 3);
        enter_insert(&mut e);
        e.insert_delete();
        assert_eq!(e.buffer().lines().len(), 1);
        assert_eq!(e.buffer().lines()[0], "foobar");
    }

    #[test]
    fn insert_arrow_left_moves_cursor() {
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 3);
        enter_insert(&mut e);
        e.insert_arrow(crate::vim::InsertDir::Left);
        assert_eq!(e.cursor().1, 2);
    }

    #[test]
    fn insert_arrow_right_moves_cursor() {
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 2);
        enter_insert(&mut e);
        e.insert_arrow(crate::vim::InsertDir::Right);
        assert_eq!(e.cursor().1, 3);
    }

    #[test]
    fn insert_arrow_up_moves_cursor() {
        let mut e = fresh_editor("foo\nbar");
        e.jump_cursor(1, 0);
        enter_insert(&mut e);
        e.insert_arrow(crate::vim::InsertDir::Up);
        assert_eq!(e.cursor().0, 0);
    }

    #[test]
    fn insert_arrow_down_moves_cursor() {
        let mut e = fresh_editor("foo\nbar");
        e.jump_cursor(0, 0);
        enter_insert(&mut e);
        e.insert_arrow(crate::vim::InsertDir::Down);
        assert_eq!(e.cursor().0, 1);
    }

    #[test]
    fn insert_home_moves_to_line_start() {
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 4);
        enter_insert(&mut e);
        e.insert_home();
        assert_eq!(e.cursor().1, 0);
    }

    #[test]
    fn insert_end_moves_to_line_end() {
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 0);
        enter_insert(&mut e);
        e.insert_end();
        // move_line_end lands on the last char (col 4) for "hello".
        assert_eq!(e.cursor().1, 4);
    }

    #[test]
    fn insert_pageup_does_not_panic() {
        let mut e = fresh_editor("line1\nline2\nline3");
        e.jump_cursor(2, 0);
        enter_insert(&mut e);
        // Viewport height 0 → no crash (viewport_h saturates to 1 row effectively).
        e.insert_pageup(24);
    }

    #[test]
    fn insert_pagedown_does_not_panic() {
        let mut e = fresh_editor("line1\nline2\nline3");
        e.jump_cursor(0, 0);
        enter_insert(&mut e);
        e.insert_pagedown(24);
    }

    #[test]
    fn leave_insert_to_normal_exits_mode() {
        let mut e = fresh_editor("hello");
        enter_insert(&mut e);
        e.leave_insert_to_normal();
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
    }

    #[test]
    fn insert_backspace_at_buffer_start_is_noop() {
        let mut e = fresh_editor("hello");
        e.jump_cursor(0, 0);
        enter_insert(&mut e);
        // No previous char and no previous row — should not panic.
        e.insert_backspace();
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn insert_delete_at_buffer_end_is_noop() {
        let mut e = fresh_editor("hello");
        // Cursor at col 5 (past last char index of 4), no next row.
        e.jump_cursor(0, 5);
        enter_insert(&mut e);
        // col 5 >= line_chars (5), no next row → no-op.
        e.insert_delete();
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    // ── Phase 6.2: normal-mode primitive tests (kryptic-sh/hjkl#88) ─────────

    // Helper: set content and ensure we are in Normal mode.
    fn normal_editor(initial: &str) -> Editor {
        let e = fresh_editor(initial);
        // fresh_editor starts in Normal; this is just a readability alias.
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
        e
    }

    // ── Insert-mode entry ────────────────────────────────────────────────────

    #[test]
    fn enter_insert_i_lands_in_insert_at_cursor() {
        let mut e = normal_editor("hello");
        e.jump_cursor(0, 2);
        e.enter_insert_i(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.cursor(), (0, 2));
    }

    #[test]
    fn enter_insert_shift_i_moves_to_first_non_blank_then_insert() {
        let mut e = normal_editor("  hello");
        e.jump_cursor(0, 5);
        e.enter_insert_shift_i(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        // First non-blank of "  hello" is col 2.
        assert_eq!(e.cursor().1, 2);
    }

    #[test]
    fn enter_insert_a_advances_one_then_insert() {
        let mut e = normal_editor("hello");
        e.jump_cursor(0, 0);
        e.enter_insert_a(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.cursor().1, 1);
    }

    #[test]
    fn enter_insert_shift_a_lands_at_eol() {
        let mut e = normal_editor("hello");
        e.enter_insert_shift_a(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.cursor().1, 5);
    }

    #[test]
    fn open_line_below_creates_new_line_and_insert() {
        let mut e = normal_editor("hello\nworld");
        e.open_line_below(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.buffer().lines().len(), 3);
    }

    #[test]
    fn open_line_above_creates_line_before_cursor() {
        let mut e = normal_editor("hello\nworld");
        e.jump_cursor(1, 0);
        e.open_line_above(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.buffer().lines().len(), 3);
        assert_eq!(e.cursor().0, 1);
    }

    #[test]
    fn open_line_above_at_row_0_creates_blank_first_line() {
        let mut e = normal_editor("hello");
        e.open_line_above(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        // New blank line is row 0; old "hello" is row 1.
        assert_eq!(e.cursor().0, 0);
        assert_eq!(e.buffer().lines()[1], "hello");
    }

    #[test]
    fn enter_replace_mode_sets_insert_mode() {
        let mut e = normal_editor("hello");
        e.enter_replace_mode(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
    }

    // ── Char / line ops ──────────────────────────────────────────────────────

    #[test]
    fn delete_char_forward_removes_one_char() {
        let mut e = normal_editor("hello");
        e.jump_cursor(0, 1);
        e.delete_char_forward(1);
        assert_eq!(e.buffer().lines()[0], "hllo");
    }

    #[test]
    fn delete_char_forward_count_5_removes_five() {
        let mut e = normal_editor("hello world");
        e.delete_char_forward(5);
        assert_eq!(e.buffer().lines()[0], " world");
    }

    #[test]
    fn delete_char_forward_noop_on_empty_line() {
        let mut e = normal_editor("");
        let before = e.content().to_string();
        e.delete_char_forward(1);
        // Empty buffer: no chars to delete, content unchanged.
        assert_eq!(e.content(), before.as_str());
    }

    #[test]
    fn delete_char_backward_removes_char_before_cursor() {
        let mut e = normal_editor("hello");
        e.jump_cursor(0, 3);
        e.delete_char_backward(1);
        assert_eq!(e.buffer().lines()[0], "helo");
    }

    #[test]
    fn delete_char_backward_noop_at_col_0() {
        let mut e = normal_editor("hello");
        e.jump_cursor(0, 0);
        e.delete_char_backward(1);
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn substitute_char_deletes_and_enters_insert() {
        let mut e = normal_editor("hello");
        e.jump_cursor(0, 0);
        e.substitute_char(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.buffer().lines()[0], "ello");
    }

    #[test]
    fn substitute_char_count_3_deletes_three() {
        let mut e = normal_editor("hello");
        e.substitute_char(3);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.buffer().lines()[0], "lo");
    }

    #[test]
    fn substitute_line_clears_content_and_enters_insert() {
        let mut e = normal_editor("hello world");
        e.substitute_line(1);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        assert_eq!(e.buffer().lines()[0], "");
    }

    #[test]
    fn delete_to_eol_removes_from_cursor_to_end() {
        let mut e = normal_editor("hello world");
        e.jump_cursor(0, 5);
        e.delete_to_eol();
        // col 5 is ' ' — deletes " world", leaving "hello".
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn delete_to_eol_noop_when_cursor_past_end() {
        let mut e = normal_editor("hi");
        e.jump_cursor(0, 2);
        e.delete_to_eol();
        assert_eq!(e.buffer().lines()[0], "hi");
    }

    #[test]
    fn change_to_eol_enters_insert() {
        let mut e = normal_editor("hello world");
        e.jump_cursor(0, 5);
        e.change_to_eol();
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        // col 5 is ' ' — deletes " world", leaving "hello".
        assert_eq!(e.buffer().lines()[0], "hello");
    }

    #[test]
    fn yank_to_eol_fills_register() {
        let mut e = normal_editor("hello world");
        e.jump_cursor(0, 6);
        e.yank_to_eol(1);
        // Yank does not change mode.
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
        // Unnamed register holds the yanked text (col 6 is 'w' in "world").
        assert!(
            e.registers().unnamed.text.starts_with("world")
                || e.registers().unnamed.text.contains("world")
        );
    }

    #[test]
    fn join_line_merges_next_line_with_space() {
        let mut e = normal_editor("foo\nbar");
        e.join_line(1);
        assert_eq!(e.buffer().lines()[0], "foo bar");
    }

    #[test]
    fn join_line_count_2_merges_three_lines() {
        let mut e = normal_editor("a\nb\nc");
        e.join_line(2);
        // Our bridge calls join_line() `count` times, each joining the
        // current line with the next → 2 iterations: "a b c".
        assert_eq!(e.buffer().lines()[0], "a b c");
    }

    #[test]
    fn join_line_noop_on_last_line() {
        let mut e = normal_editor("only");
        e.join_line(1);
        assert_eq!(e.buffer().lines()[0], "only");
    }

    #[test]
    fn toggle_case_at_cursor_flips_letter() {
        let mut e = normal_editor("hello");
        e.toggle_case_at_cursor(1);
        assert_eq!(e.buffer().lines()[0], "Hello");
    }

    #[test]
    fn toggle_case_at_cursor_count_3_flips_three() {
        let mut e = normal_editor("hello");
        e.toggle_case_at_cursor(3);
        assert_eq!(e.buffer().lines()[0], "HELlo");
    }

    // ── Undo / redo round-trip ───────────────────────────────────────────────

    #[test]
    fn undo_redo_roundtrip_via_public_methods() {
        let mut e = normal_editor("hello");
        e.delete_char_forward(1);
        assert_eq!(e.buffer().lines()[0], "ello");
        e.undo();
        assert_eq!(e.buffer().lines()[0], "hello");
        e.redo();
        assert_eq!(e.buffer().lines()[0], "ello");
    }

    // ── Jump / scroll ────────────────────────────────────────────────────────

    #[test]
    fn jump_back_and_forward_roundtrip() {
        let mut e = fresh_editor("a\nb\nc\nd");
        e.set_viewport_height(10);
        e.jump_cursor(3, 0);
        // Push current pos onto jumplist (big motion done externally; use
        // `run_keys` shortcut: `gg` pushes jump then `G` jumps).
        // Simpler: just call jump_back with empty stack → no-op (shouldn't panic).
        e.jump_back(1);
        e.jump_forward(1);
    }

    #[test]
    fn scroll_full_page_down_moves_cursor() {
        use crate::vim::ScrollDir;
        let lines = (0..30)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n");
        let mut e = fresh_editor(&lines);
        e.set_viewport_height(10);
        let before = e.cursor().0;
        e.scroll_full_page(ScrollDir::Down, 1);
        assert!(e.cursor().0 > before);
    }

    #[test]
    fn scroll_full_page_up_moves_cursor() {
        use crate::vim::ScrollDir;
        let lines = (0..30)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n");
        let mut e = fresh_editor(&lines);
        e.set_viewport_height(10);
        e.jump_cursor(25, 0);
        let before = e.cursor().0;
        e.scroll_full_page(ScrollDir::Up, 1);
        assert!(e.cursor().0 < before);
    }

    #[test]
    fn scroll_half_page_down_moves_cursor() {
        use crate::vim::ScrollDir;
        let lines = (0..30)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n");
        let mut e = fresh_editor(&lines);
        e.set_viewport_height(10);
        let before = e.cursor().0;
        e.scroll_half_page(ScrollDir::Down, 1);
        assert!(e.cursor().0 > before);
    }

    #[test]
    fn scroll_half_page_up_at_top_is_noop() {
        use crate::vim::ScrollDir;
        let lines = (0..30)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n");
        let mut e = fresh_editor(&lines);
        e.set_viewport_height(10);
        // Already at top, scrolling up should not panic and cursor stays at 0.
        e.scroll_half_page(ScrollDir::Up, 1);
        assert_eq!(e.cursor().0, 0);
    }

    #[test]
    fn scroll_line_down_shifts_viewport_without_moving_cursor() {
        use crate::vim::ScrollDir;
        let lines = (0..30)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n");
        let mut e = fresh_editor(&lines);
        e.set_viewport_height(10);
        // Park cursor in the middle of a large buffer.
        e.jump_cursor(15, 0);
        e.set_viewport_top(10);
        let cursor_before = e.cursor().0;
        e.scroll_line(ScrollDir::Down, 1);
        // Viewport top advances; cursor stays.
        assert_eq!(e.cursor().0, cursor_before);
        assert_eq!(e.host().viewport().top_row, 11);
    }

    #[test]
    fn scroll_line_up_shifts_viewport() {
        use crate::vim::ScrollDir;
        let lines = (0..30)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n");
        let mut e = fresh_editor(&lines);
        e.set_viewport_height(10);
        e.jump_cursor(15, 0);
        e.set_viewport_top(10);
        let cursor_before = e.cursor().0;
        e.scroll_line(ScrollDir::Up, 1);
        assert_eq!(e.cursor().0, cursor_before);
        assert_eq!(e.host().viewport().top_row, 9);
    }

    #[test]
    fn scroll_line_clamps_cursor_when_off_screen() {
        use crate::vim::ScrollDir;
        let lines = (0..30)
            .map(|i| format!("line{i}"))
            .collect::<Vec<_>>()
            .join("\n");
        let mut e = fresh_editor(&lines);
        e.set_viewport_height(10);
        // Cursor at viewport top; scrolling down pushes it off — must clamp.
        e.jump_cursor(5, 0);
        e.set_viewport_top(5);
        e.scroll_line(ScrollDir::Down, 3);
        // New top = 8; cursor was at 5, which is now off-screen (< 8).
        // Cursor clamped to new top.
        assert!(e.cursor().0 >= 8);
    }

    #[test]
    fn scroll_doesnt_crash_at_buffer_edges() {
        use crate::vim::ScrollDir;
        let mut e = normal_editor("single line");
        e.set_viewport_height(10);
        // Should not panic on any of these at-the-edge scrolls.
        e.scroll_full_page(ScrollDir::Down, 99);
        e.scroll_full_page(ScrollDir::Up, 99);
        e.scroll_half_page(ScrollDir::Down, 99);
        e.scroll_half_page(ScrollDir::Up, 99);
        e.scroll_line(ScrollDir::Down, 99);
        e.scroll_line(ScrollDir::Up, 99);
    }

    // ── Horizontal scroll ────────────────────────────────────────────────────

    #[test]
    fn scroll_right_advances_top_col() {
        let mut e = fresh_editor("hello world");
        e.set_viewport_height(10);
        e.scroll_right(5);
        assert_eq!(e.host().viewport().top_col, 5);
    }

    #[test]
    fn scroll_left_does_not_underflow() {
        let mut e = fresh_editor("hello world");
        e.set_viewport_height(10);
        e.scroll_right(2);
        e.scroll_left(10);
        assert_eq!(e.host().viewport().top_col, 0);
    }

    #[test]
    fn scroll_left_then_right_roundtrip() {
        let mut e = fresh_editor("hello world");
        e.set_viewport_height(10);
        e.scroll_right(10);
        e.scroll_left(3);
        assert_eq!(e.host().viewport().top_col, 7);
    }

    // ── Search ───────────────────────────────────────────────────────────────

    #[test]
    fn search_repeat_advances_to_next_match() {
        let mut e = fresh_editor("foo bar foo baz");
        // Use word_search to seed the search state (no search prompt needed).
        // `*` on "foo" at col 0 finds the second "foo" and sets last_search.
        e.word_search(true, true, 1);
        // Repeating forward wraps and finds the first "foo" again at col 0.
        e.search_repeat(true, 1);
        // Just ensure no panic and search state is valid.
        assert!(e.cursor().0 < e.buffer().lines().len());
    }

    #[test]
    fn search_repeat_no_pattern_is_noop() {
        let mut e = normal_editor("hello world");
        let before = e.cursor();
        // No search pattern loaded — should not panic.
        e.search_repeat(true, 1);
        assert_eq!(e.cursor(), before);
    }

    #[test]
    fn word_search_finds_word_under_cursor() {
        let mut e = fresh_editor("foo bar foo");
        // cursor starts at col 0 on "foo"
        e.word_search(true, true, 1);
        // Should jump to the second "foo" at col 8.
        assert_eq!(e.cursor().1, 8);
    }

    #[test]
    fn word_search_whole_word_false_extracts_word_under_cursor() {
        // `g*` on "foo" (no `\b`) — use two lines so wrap can find the next match.
        let mut e = fresh_editor("foobar\nfoo baz");
        // Cursor on second line "foo" at col 0.
        e.jump_cursor(1, 0);
        // g* with whole_word=false: pattern = "foo", advance forward (skip current).
        // Starting at (1, 0), skip "foo" at (1,0), wrap to (0, 0) which matches "foo"
        // inside "foobar".
        e.word_search(true, false, 1);
        // Cursor should land on "foo" at row 0, col 0.
        assert_eq!(e.cursor(), (0, 0));
    }

    #[test]
    fn word_search_backward_finds_previous_match() {
        let mut e = fresh_editor("foo bar foo");
        e.jump_cursor(0, 8); // on second "foo"
        e.word_search(false, true, 1);
        // Cursor should land on col 0 (first "foo").
        assert_eq!(e.cursor().1, 0);
    }

    // ── Edge cases ───────────────────────────────────────────────────────────

    #[test]
    fn delete_char_forward_on_single_char_line() {
        let mut e = normal_editor("x");
        e.delete_char_forward(1);
        assert_eq!(e.buffer().lines()[0], "");
    }

    #[test]
    fn substitute_char_on_empty_line_is_noop_for_delete() {
        let mut e = normal_editor("");
        e.substitute_char(1);
        // Nothing to delete — but should enter Insert mode.
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
    }

    #[test]
    fn join_line_10_iterations_clamps_gracefully() {
        let mut e = normal_editor("a\nb");
        // Joining 10 times on a 2-line buffer should not panic.
        e.join_line(10);
        // After the first join succeeds, the rest are no-ops.
        assert_eq!(e.buffer().lines()[0], "a b");
    }

    #[test]
    fn toggle_case_past_line_end_is_noop() {
        let mut e = normal_editor("ab");
        e.jump_cursor(0, 5); // way past end
        e.toggle_case_at_cursor(1);
        // Should not panic.
        assert_eq!(e.buffer().lines()[0], "ab");
    }

    // ── Phase 6.3: visual-mode primitive tests (kryptic-sh/hjkl#89) ──────────

    // ── Visual entry ─────────────────────────────────────────────────────────

    #[test]
    fn enter_visual_char_lands_in_visual_at_cursor() {
        let mut e = normal_editor("hello world");
        e.jump_cursor(0, 3);
        e.enter_visual_char();
        assert_eq!(e.vim_mode(), crate::VimMode::Visual);
        // Anchor should be at the cursor position we entered from.
        assert_eq!(e.vim.visual_anchor, (0, 3));
    }

    #[test]
    fn enter_visual_line_lands_in_visual_line() {
        let mut e = normal_editor("hello\nworld");
        e.jump_cursor(1, 2);
        e.enter_visual_line();
        assert_eq!(e.vim_mode(), crate::VimMode::VisualLine);
        // Line anchor should be the current row.
        assert_eq!(e.vim.visual_line_anchor, 1);
    }

    #[test]
    fn enter_visual_block_lands_in_visual_block() {
        let mut e = normal_editor("hello\nworld");
        e.jump_cursor(0, 2);
        e.enter_visual_block();
        assert_eq!(e.vim_mode(), crate::VimMode::VisualBlock);
        // Block anchor and vcol should match the cursor column.
        assert_eq!(e.vim.block_anchor, (0, 2));
        assert_eq!(e.vim.block_vcol, 2);
    }

    // ── Visual exit ──────────────────────────────────────────────────────────

    #[test]
    fn exit_visual_to_normal_sets_marks_and_returns_to_normal() {
        let mut e = normal_editor("hello world");
        // Enter charwise visual at col 2, extend to col 5.
        e.jump_cursor(0, 2);
        e.enter_visual_char();
        e.jump_cursor(0, 5);
        e.exit_visual_to_normal();
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
        // `<` = (0, 2), `>` = (0, 5).
        assert_eq!(e.mark('<'), Some((0, 2)));
        assert_eq!(e.mark('>'), Some((0, 5)));
    }

    #[test]
    fn exit_visual_to_normal_stores_last_visual() {
        let mut e = normal_editor("hello world");
        e.jump_cursor(0, 1);
        e.enter_visual_char();
        e.jump_cursor(0, 4);
        e.exit_visual_to_normal();
        // last_visual should be set so gv can restore it.
        assert!(e.vim.last_visual.is_some());
        let lv = e.vim.last_visual.unwrap();
        assert_eq!(lv.anchor, (0, 1));
        assert_eq!(lv.cursor, (0, 4));
    }

    #[test]
    fn exit_visual_line_sets_marks_at_line_boundaries() {
        let mut e = normal_editor("alpha\nbeta\ngamma");
        e.enter_visual_line(); // row 0
        e.jump_cursor(1, 3);
        e.exit_visual_to_normal();
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
        // `<` snaps to (min_row, 0), `>` snaps to (max_row, last_col).
        assert_eq!(e.mark('<'), Some((0, 0)));
        let last_col_of_beta = "beta".chars().count() - 1;
        assert_eq!(e.mark('>'), Some((1, last_col_of_beta)));
    }

    // ── visual_o_toggle ───────────────────────────────────────────────────────

    #[test]
    fn visual_o_toggle_swaps_anchor_and_cursor_charwise() {
        let mut e = normal_editor("hello world");
        // Enter visual at col 0, extend to col 4.
        e.enter_visual_char(); // anchor = (0,0)
        e.jump_cursor(0, 4); // cursor at col 4
        // Selection bounds before toggle: anchor=0, cursor=4.
        let pre_anchor = e.vim.visual_anchor;
        let pre_cursor = e.cursor();
        e.visual_o_toggle();
        // After toggle: cursor jumps to old anchor, anchor = old cursor.
        assert_eq!(e.cursor(), pre_anchor, "cursor should move to old anchor");
        assert_eq!(
            e.vim.visual_anchor, pre_cursor,
            "anchor should take old cursor position"
        );
        // Mode is unchanged.
        assert_eq!(e.vim_mode(), crate::VimMode::Visual);
    }

    #[test]
    fn visual_o_toggle_double_returns_to_start() {
        let mut e = normal_editor("hello world");
        e.enter_visual_char();
        e.jump_cursor(0, 4);
        let anchor0 = e.vim.visual_anchor;
        let cursor0 = e.cursor();
        e.visual_o_toggle();
        e.visual_o_toggle();
        // Two toggles restore original positions.
        assert_eq!(e.vim.visual_anchor, anchor0);
        assert_eq!(e.cursor(), cursor0);
    }

    #[test]
    fn visual_o_toggle_linewise_swaps_anchor_row() {
        let mut e = normal_editor("alpha\nbeta\ngamma");
        e.enter_visual_line(); // anchor row = 0
        e.jump_cursor(2, 0); // cursor on row 2
        e.visual_o_toggle();
        // Cursor should jump to old anchor row.
        assert_eq!(e.cursor().0, 0, "cursor row should be old anchor row");
        // Anchor row should now be the old cursor row.
        assert_eq!(e.vim.visual_line_anchor, 2);
    }

    // ── reenter_last_visual ───────────────────────────────────────────────────

    #[test]
    fn reenter_last_visual_after_vdollar_esc_restores() {
        let mut e = normal_editor("hello world");
        // v$ then Esc via FSM to store a real last_visual.
        e.enter_visual_char(); // anchor = (0,0)
        e.jump_cursor(0, 5); // move cursor to col 5 to create a range
        e.exit_visual_to_normal();
        // Should be back to Normal.
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
        // gv — should restore Visual mode.
        e.reenter_last_visual();
        assert_eq!(e.vim_mode(), crate::VimMode::Visual);
        // Cursor should be at the stored last position (col 5).
        assert_eq!(e.cursor().1, 5);
    }

    #[test]
    fn reenter_last_visual_noop_when_no_history() {
        let mut e = normal_editor("hello");
        // No prior visual — should be a no-op, not a panic.
        e.reenter_last_visual();
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
    }

    // ── set_mode ─────────────────────────────────────────────────────────────

    #[test]
    fn set_mode_insert_flips_vim_mode_to_insert() {
        let mut e = normal_editor("hello");
        e.set_mode(crate::VimMode::Insert);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
    }

    #[test]
    fn set_mode_roundtrip_normal_insert_normal() {
        let mut e = normal_editor("hello");
        e.set_mode(crate::VimMode::Insert);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        e.set_mode(crate::VimMode::Normal);
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
    }

    #[test]
    fn set_mode_visual_variants() {
        let mut e = normal_editor("hello");
        e.set_mode(crate::VimMode::Visual);
        assert_eq!(e.vim_mode(), crate::VimMode::Visual);
        e.set_mode(crate::VimMode::VisualLine);
        assert_eq!(e.vim_mode(), crate::VimMode::VisualLine);
        e.set_mode(crate::VimMode::VisualBlock);
        assert_eq!(e.vim_mode(), crate::VimMode::VisualBlock);
        e.set_mode(crate::VimMode::Normal);
        assert_eq!(e.vim_mode(), crate::VimMode::Normal);
    }

    // ── current_mode / vim_mode consistency ───────────────────────────────────

    // ── Phase 6.6b: FSM state accessor smoke tests ────────────────────────────

    #[test]
    fn pending_round_trips() {
        let mut e = normal_editor("hello");
        assert!(matches!(e.pending(), crate::vim::Pending::None));
        e.set_pending(crate::vim::Pending::G);
        assert!(matches!(e.pending(), crate::vim::Pending::G));
        let taken = e.take_pending();
        assert!(matches!(taken, crate::vim::Pending::G));
        assert!(matches!(e.pending(), crate::vim::Pending::None));
    }

    #[test]
    fn count_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.count(), 0);
        e.set_count(5);
        assert_eq!(e.count(), 5);
        e.accumulate_count_digit(3);
        assert_eq!(e.count(), 53);
        e.reset_count();
        assert_eq!(e.count(), 0);
    }

    #[test]
    fn take_count_returns_one_when_zero() {
        let mut e = normal_editor("hello");
        assert_eq!(e.take_count(), 1);
    }

    #[test]
    fn take_count_returns_value_and_resets() {
        let mut e = normal_editor("hello");
        e.set_count(7);
        assert_eq!(e.take_count(), 7);
        assert_eq!(e.count(), 0);
    }

    #[test]
    fn fsm_mode_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.fsm_mode(), crate::vim::Mode::Normal);
        e.set_fsm_mode(crate::vim::Mode::Insert);
        assert_eq!(e.fsm_mode(), crate::vim::Mode::Insert);
        assert_eq!(e.vim_mode(), crate::VimMode::Insert);
        e.set_fsm_mode(crate::vim::Mode::Normal);
        assert_eq!(e.fsm_mode(), crate::vim::Mode::Normal);
    }

    #[test]
    fn replaying_flag_round_trips() {
        let mut e = normal_editor("hello");
        assert!(!e.is_replaying());
        e.set_replaying(true);
        assert!(e.is_replaying());
        e.set_replaying(false);
        assert!(!e.is_replaying());
    }

    #[test]
    fn one_shot_normal_flag_round_trips() {
        let mut e = normal_editor("hello");
        assert!(!e.is_one_shot_normal());
        e.set_one_shot_normal(true);
        assert!(e.is_one_shot_normal());
        e.set_one_shot_normal(false);
        assert!(!e.is_one_shot_normal());
    }

    #[test]
    fn last_find_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.last_find(), None);
        e.set_last_find(Some(('x', true, false)));
        assert_eq!(e.last_find(), Some(('x', true, false)));
        e.set_last_find(None);
        assert_eq!(e.last_find(), None);
    }

    #[test]
    fn last_change_round_trips() {
        let mut e = normal_editor("hello");
        assert!(e.last_change().is_none());
        e.set_last_change(Some(crate::vim::LastChange::ToggleCase { count: 2 }));
        let lc = e.last_change();
        assert!(matches!(
            lc,
            Some(crate::vim::LastChange::ToggleCase { count: 2 })
        ));
        e.set_last_change(None);
        assert!(e.last_change().is_none());
    }

    #[test]
    fn last_change_mut_allows_in_place_edit() {
        let mut e = normal_editor("hello");
        e.set_last_change(Some(crate::vim::LastChange::ToggleCase { count: 1 }));
        if let Some(crate::vim::LastChange::ToggleCase { count }) = e.last_change_mut() {
            *count = 42;
        }
        assert!(matches!(
            e.last_change(),
            Some(crate::vim::LastChange::ToggleCase { count: 42 })
        ));
    }

    #[test]
    fn insert_session_round_trips() {
        let mut e = normal_editor("hello");
        assert!(e.insert_session().is_none());
        e.set_insert_session(Some(crate::vim::InsertSession {
            count: 3,
            row_min: 0,
            row_max: 0,
            before_lines: vec!["hello".to_string()],
            reason: crate::vim::InsertReason::Enter(crate::vim::InsertEntry::I),
        }));
        assert_eq!(e.insert_session().map(|s| s.count), Some(3));
        let taken = e.take_insert_session();
        assert!(taken.is_some());
        assert!(e.insert_session().is_none());
    }

    #[test]
    fn visual_anchor_round_trips() {
        let mut e = normal_editor("hello");
        e.set_visual_anchor((1, 3));
        assert_eq!(e.visual_anchor(), (1, 3));
    }

    #[test]
    fn visual_line_anchor_round_trips() {
        let mut e = normal_editor("hello\nworld");
        e.set_visual_line_anchor(1);
        assert_eq!(e.visual_line_anchor(), 1);
    }

    #[test]
    fn block_anchor_and_vcol_round_trip() {
        let mut e = normal_editor("hello");
        e.set_block_anchor((0, 2));
        e.set_block_vcol(4);
        assert_eq!(e.block_anchor(), (0, 2));
        assert_eq!(e.block_vcol(), 4);
    }

    #[test]
    fn yank_linewise_round_trips() {
        let mut e = normal_editor("hello");
        assert!(!e.yank_linewise());
        e.set_yank_linewise(true);
        assert!(e.yank_linewise());
    }

    #[test]
    fn pending_register_raw_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.pending_register(), None);
        e.set_pending_register_raw(Some('a'));
        assert_eq!(e.pending_register(), Some('a'));
        let taken = e.take_pending_register_raw();
        assert_eq!(taken, Some('a'));
        assert_eq!(e.pending_register(), None);
    }

    #[test]
    fn recording_macro_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.recording_macro(), None);
        e.set_recording_macro(Some('q'));
        assert_eq!(e.recording_macro(), Some('q'));
        e.set_recording_macro(None);
        assert_eq!(e.recording_macro(), None);
    }

    #[test]
    fn recording_keys_round_trips() {
        let mut e = normal_editor("hello");
        let input = crate::Input {
            key: crate::Key::Char('j'),
            ctrl: false,
            alt: false,
            shift: false,
        };
        e.push_recording_key(input);
        assert_eq!(e.take_recording_keys(), vec![input]);
        assert!(e.take_recording_keys().is_empty());
    }

    #[test]
    fn replaying_macro_raw_round_trips() {
        let mut e = normal_editor("hello");
        assert!(!e.is_replaying_macro_raw());
        e.set_replaying_macro_raw(true);
        assert!(e.is_replaying_macro_raw());
        e.set_replaying_macro_raw(false);
        assert!(!e.is_replaying_macro_raw());
    }

    #[test]
    fn last_macro_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.last_macro(), None);
        e.set_last_macro(Some('m'));
        assert_eq!(e.last_macro(), Some('m'));
    }

    #[test]
    fn last_insert_pos_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.last_insert_pos(), None);
        e.set_last_insert_pos(Some((1, 2)));
        assert_eq!(e.last_insert_pos(), Some((1, 2)));
    }

    #[test]
    fn last_visual_round_trips() {
        let mut e = normal_editor("hello");
        assert!(e.last_visual().is_none());
        let snap = crate::vim::LastVisual {
            mode: crate::vim::Mode::Visual,
            anchor: (0, 0),
            cursor: (0, 3),
            block_vcol: 0,
        };
        e.set_last_visual(Some(snap));
        assert!(e.last_visual().is_some());
        e.set_last_visual(None);
        assert!(e.last_visual().is_none());
    }

    #[test]
    fn viewport_pinned_round_trips() {
        let mut e = normal_editor("hello");
        assert!(!e.viewport_pinned());
        e.set_viewport_pinned(true);
        assert!(e.viewport_pinned());
        e.set_viewport_pinned(false);
        assert!(!e.viewport_pinned());
    }

    #[test]
    fn insert_pending_register_round_trips() {
        let mut e = normal_editor("hello");
        assert!(!e.insert_pending_register());
        e.set_insert_pending_register(true);
        assert!(e.insert_pending_register());
    }

    #[test]
    fn change_mark_start_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.change_mark_start(), None);
        e.set_change_mark_start(Some((2, 5)));
        assert_eq!(e.change_mark_start(), Some((2, 5)));
        let taken = e.take_change_mark_start();
        assert_eq!(taken, Some((2, 5)));
        assert_eq!(e.change_mark_start(), None);
    }

    #[test]
    fn search_prompt_state_round_trips() {
        let mut e = normal_editor("hello");
        assert!(e.search_prompt_state().is_none());
        e.set_search_prompt_state(Some(crate::vim::SearchPrompt {
            text: "foo".to_string(),
            cursor: 3,
            forward: true,
        }));
        assert_eq!(
            e.search_prompt_state().map(|p| p.text.as_str()),
            Some("foo")
        );
        let taken = e.take_search_prompt_state();
        assert!(taken.is_some());
        assert!(e.search_prompt_state().is_none());
    }

    #[test]
    fn last_search_pattern_and_direction_round_trips() {
        let mut e = normal_editor("hello");
        assert_eq!(e.last_search_pattern(), None);
        e.set_last_search_pattern_only(Some("world".to_string()));
        assert_eq!(e.last_search_pattern(), Some("world"));
        e.set_last_search_forward_only(false);
        assert!(!e.last_search_forward());
    }

    #[test]
    fn search_history_round_trips() {
        let mut e = normal_editor("hello");
        assert!(e.search_history().is_empty());
        e.search_history_mut().push("pattern1".to_string());
        assert_eq!(e.search_history(), &["pattern1"]);
        e.set_search_history_cursor(Some(0));
        assert_eq!(e.search_history_cursor(), Some(0));
        e.set_search_history_cursor(None);
        assert_eq!(e.search_history_cursor(), None);
    }

    #[test]
    fn jump_lists_round_trips() {
        let mut e = normal_editor("hello");
        assert!(e.jump_back_list().is_empty());
        assert!(e.jump_fwd_list().is_empty());
        e.jump_back_list_mut().push((1, 2));
        e.jump_fwd_list_mut().push((3, 4));
        assert_eq!(e.jump_back_list(), &[(1, 2)]);
        assert_eq!(e.jump_fwd_list(), &[(3, 4)]);
    }

    #[test]
    fn last_input_timing_round_trips() {
        let mut e = normal_editor("hello");
        assert!(e.last_input_at().is_none());
        assert!(e.last_input_host_at().is_none());
        let now = std::time::Instant::now();
        e.set_last_input_at(Some(now));
        assert!(e.last_input_at().is_some());
        let dur = core::time::Duration::from_millis(100);
        e.set_last_input_host_at(Some(dur));
        assert_eq!(e.last_input_host_at(), Some(dur));
    }

    // ── auto_indent_range tests ──────────────────────────────────────────────

    /// Helper: build an editor with `expandtab=true` and the given shiftwidth.
    fn indent_editor(initial: &str, shiftwidth: usize, expandtab: bool) -> Editor {
        let mut e = fresh_editor(initial);
        e.settings_mut().shiftwidth = shiftwidth;
        e.settings_mut().expandtab = expandtab;
        e
    }

    #[test]
    fn auto_indent_single_line_under_open_brace() {
        // `{\nfoo\n}` — "foo" is at depth 1 under the `{`.
        // With shiftwidth=4 expandtab=true it should become "    foo".
        let mut e = indent_editor("{\nfoo\n}", 4, true);
        // auto-indent only row 1 ("foo").
        e.auto_indent_range((1, 0), (1, 0));
        let lines = e.buffer().lines();
        assert_eq!(lines[1], "    foo", "foo should be indented by 4 spaces");
    }

    #[test]
    fn auto_indent_close_brace_outdents() {
        // `{\n    inner\n}` — the `}` is at depth 1 but starts with a close
        // bracket so effective_depth = 0.
        let mut e = indent_editor("{\n    inner\n}", 4, true);
        e.auto_indent_range((2, 0), (2, 0));
        let lines = e.buffer().lines();
        assert_eq!(lines[2], "}", "`}}` should have zero indent");
    }

    #[test]
    fn auto_indent_whole_buffer_normalizes_mixed_indent() {
        // Mixed-indent input: first line un-indented `{`, second line 1-tab
        // indented body, third line un-indented `}`.
        let src = "{\n\tbody\n}";
        let mut e = indent_editor(src, 4, true);
        let total = e.buffer().lines().len();
        e.auto_indent_range((0, 0), (total - 1, 0));
        let lines = e.buffer().lines();
        // `{` — depth 0 at start.
        assert_eq!(lines[0], "{");
        // `body` — depth 1 after `{`.
        assert_eq!(lines[1], "    body");
        // `}` — depth 1 but starts with close → effective_depth 0.
        assert_eq!(lines[2], "}");
    }

    #[test]
    fn auto_indent_respects_expandtab_false_uses_tabs() {
        // Same buffer, but expandtab=false → indent unit is `\t`.
        let src = "{\nbody\n}";
        let mut e = indent_editor(src, 4, false);
        let total = e.buffer().lines().len();
        e.auto_indent_range((0, 0), (total - 1, 0));
        let lines = e.buffer().lines();
        assert_eq!(lines[0], "{");
        assert_eq!(lines[1], "\tbody");
        assert_eq!(lines[2], "}");
    }

    #[test]
    fn auto_indent_empty_line_stays_empty() {
        // `{\n\nfoo\n}` — blank line in the middle should stay blank.
        let src = "{\n\nfoo\n}";
        let mut e = indent_editor(src, 4, true);
        let total = e.buffer().lines().len();
        e.auto_indent_range((0, 0), (total - 1, 0));
        let lines = e.buffer().lines();
        assert_eq!(lines[1], "", "blank line should stay blank");
        assert_eq!(lines[2], "    foo");
    }

    #[test]
    fn auto_indent_cursor_lands_on_first_nonws_of_start_row() {
        // After `==` / `auto_indent_range` the cursor should be at the first
        // non-whitespace character of start_row (vim parity).
        let src = "{\nfoo\n}";
        let mut e = indent_editor(src, 4, true);
        // Reindent only row 1.
        e.auto_indent_range((1, 0), (1, 0));
        // Row 1 after reindent is "    foo"; first non-ws is col 4.
        let (row, col) = e.cursor();
        assert_eq!(row, 1, "cursor should stay on start_row");
        assert_eq!(col, 4, "cursor should land on first non-ws char (col 4)");
    }

    #[test]
    fn auto_indent_sets_last_indent_range() {
        // After `auto_indent_range` the engine must store the touched row span.
        let src = "{\nfoo\nbar\n}";
        let mut e = indent_editor(src, 4, true);
        let total = e.buffer().lines().len();
        e.auto_indent_range((0, 0), (total - 1, 0));
        assert_eq!(
            e.take_last_indent_range(),
            Some((0, total - 1)),
            "take_last_indent_range must return Some with the touched rows"
        );
    }

    #[test]
    fn take_last_indent_range_clears() {
        // A second call after draining must return None.
        let src = "{\nfoo\n}";
        let mut e = indent_editor(src, 4, true);
        e.auto_indent_range((0, 0), (2, 0));
        let _ = e.take_last_indent_range(); // drain
        assert_eq!(
            e.take_last_indent_range(),
            None,
            "second take_last_indent_range must return None"
        );
    }

    // ── Diagnostic: auto_indent vs cargo fmt on a real source file ────────
    //
    // Loads `motions.rs` (~1400 LOC, mixed real-world Rust patterns: method
    // chains, multi-line fn args, match arms, where clauses, closures, nested
    // types) at compile time, runs `auto_indent_range` over every row, and
    // diffs per-line leading-whitespace counts against the cargo-fmt'd source
    // (the file is in the repo, fmt'd by CI on every commit).
    //
    // The test PRINTS divergences and only fails if more than `THRESHOLD`
    // lines disagree — the dumb shiftwidth+bracket algorithm is documented
    // to mishandle some patterns (chains, where clauses, etc.). A full
    // language-aware indenter is a v2 follow-up. The point of this test is
    // to surface the divergence list so we can decide which patterns the
    // dumb algo CAN be taught to handle without going full tree-sitter.
    //
    // To diagnose: run with `--nocapture` to see the full diff.
    #[test]
    #[ignore = "diagnostic — run with --ignored --nocapture to see auto-indent vs cargo fmt diffs"]
    fn auto_indent_vs_cargo_fmt_motions_diagnostic() {
        let original = include_str!("motions.rs");

        let mut e = Editor::new(
            hjkl_buffer::Buffer::new(),
            crate::types::DefaultHost::new(),
            crate::types::Options {
                shiftwidth: 4,
                expandtab: true,
                tabstop: 4,
                ..crate::types::Options::default()
            },
        );
        e.set_content(original);

        let row_count = buf_row_count(&e.buffer);
        e.auto_indent_range((0, 0), (row_count.saturating_sub(1), 0));

        let after_lines: Vec<String> = (0..row_count)
            .filter_map(|r| buf_line(&e.buffer, r).map(str::to_owned))
            .collect();
        let original_lines: Vec<&str> = original.lines().collect();

        let leading_ws = |s: &str| s.chars().take_while(|c| c.is_whitespace()).count();

        let mut diffs: Vec<(usize, String, usize, usize)> = Vec::new();
        for (i, (orig, after)) in original_lines.iter().zip(after_lines.iter()).enumerate() {
            let want = leading_ws(orig);
            let got = leading_ws(after);
            if want != got {
                diffs.push((i + 1, orig.trim().chars().take(80).collect(), want, got));
            }
        }

        // Print the first 50 divergences for diagnosis.
        eprintln!(
            "auto_indent_vs_cargo_fmt: {} lines differ out of {} ({}%)",
            diffs.len(),
            original_lines.len(),
            (diffs.len() * 100) / original_lines.len().max(1),
        );
        for (line_no, content, want, got) in diffs.iter().take(50) {
            eprintln!("  L{line_no:5} want={want:2} got={got:2}  {content}");
        }
        if diffs.len() > 50 {
            eprintln!("  ... and {} more", diffs.len() - 50);
        }

        // Soft assertion — track divergence count over time. If the algo
        // gets smarter, this number should drop. If a regression makes it
        // jump, we'll notice. Set the cap generously above current baseline.
        let pct = (diffs.len() * 100) / original_lines.len().max(1);
        // 2026-05-16 baseline after fixing bracket scan + chain continuation:
        // 5 divergences / 1416 lines (<1%). Remaining lines are a single
        // \`let X = if {} else {};\` trailing-\`=\` continuation pattern —
        // documented v2 follow-up. Cap at 2% so any regression in the
        // bracket scan or chain detection trips the test.
        assert!(
            pct < 2,
            "auto_indent diverges from cargo fmt on {pct}% of lines — regression from <1% baseline"
        );
    }
}