use crate::clipboard::{ClipboardMode, SystemClipboard};
use crate::files::{DockSide, FilePicker, FilePresentation, FileView};
use crate::plugin::{Diagnostic, TextPosition};
use serde::Serialize;
use std::borrow::Cow;
use std::collections::{BTreeMap, HashMap, HashSet};
use std::fmt;
use std::fs::{self, OpenOptions};
use std::io::{self, Write};
#[cfg(unix)]
use std::os::unix::fs::OpenOptionsExt;
use std::path::{Component, Path, PathBuf};
use std::sync::atomic::{AtomicU64, Ordering};
use unicode_segmentation::{GraphemeCursor, UnicodeSegmentation};
use unicode_width::UnicodeWidthStr;

const MAX_EDIT_BYTES: usize = 4 * 1024 * 1024;
static TEMP_ID: AtomicU64 = AtomicU64::new(0);

#[derive(Clone, Debug, Eq, Hash, PartialEq)]
pub enum Input {
    Char(char),
    Ctrl(char),
    Paste(String),
    Escape,
    Enter,
    Backspace,
    Delete,
    Left,
    Right,
    Up,
    Down,
    Home,
    End,
}

#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum Mode {
    Normal,
    Insert,
    Command,
    Search,
    Visual,
}

impl fmt::Display for Mode {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            Self::Normal => "NORMAL",
            Self::Insert => "INSERT",
            Self::Command => "COMMAND",
            Self::Search => "SEARCH",
            Self::Visual => "VISUAL",
        })
    }
}

pub struct Palette {
    pub query: String,
    /// Current filtered results, sorted by label then name.
    pub entries: Vec<PaletteEntry>,
    pub selected: usize,
}

pub struct PaletteEntry {
    pub name: String,
    pub label: String,
    pub owner: String,
    /// Effective bindings in the underlying editor mode.
    pub bindings: Vec<String>,
    pub enabled: bool,
    pub modes: Vec<Mode>,
}

#[derive(Clone, Copy, Debug, Default, Eq, Ord, PartialEq, PartialOrd)]
pub struct Cursor {
    pub row: usize,
    /// Zero-based extended grapheme index, not a byte or display-cell offset.
    pub column: usize,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct SearchMatch {
    pub start: Cursor,
    /// Exclusive end, in grapheme columns on the same row as `start`.
    pub end_column: usize,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct Selection {
    /// Inclusive start of the ordered range, in grapheme coordinates.
    pub start: Cursor,
    /// Exclusive end in grapheme coordinates; may be the next row's column 0.
    pub end: Cursor,
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Feature {
    pub name: String,
    pub required_capabilities: Vec<String>,
    pub commands: Vec<String>,
    pub core: bool,
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum Effect {
    Insert(String),
    Replace(String),
    Message(String),
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Invocation {
    pub plugin: String,
    pub command: String,
    pub args: String,
}

#[derive(Debug, Serialize)]
pub struct Context {
    pub buffer_id: usize,
    pub revision: u64,
    pub root: String,
    pub text: String,
    /// One-based row, including the empty row after a trailing newline.
    pub row: usize,
    /// One-based extended grapheme column.
    pub column: usize,
    pub mode: String,
    pub path: Option<String>,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct Target {
    anchor: Cursor,
    active: Cursor,
    // Display columns survive a clone onto a shorter line.
    preferred_columns: Option<(usize, usize)>,
}

impl Target {
    fn caret(cursor: Cursor) -> Self {
        Self {
            anchor: cursor,
            active: cursor,
            preferred_columns: None,
        }
    }
}

#[cfg_attr(test, derive(Debug))]
struct Snapshot {
    lines: Vec<String>,
    targets: Vec<Target>,
    primary: usize,
}

struct Edit<'a> {
    target: usize,
    start: usize,
    end: usize,
    text: Cow<'a, str>,
    caret: usize,
    round_up: bool,
}

// Recipes contain resolved native intent, never input keys or source-buffer offsets.
#[cfg_attr(test, derive(Debug))]
struct EditRecipe {
    start: EditStart,
    steps: Vec<InsertStep>,
}

#[cfg_attr(test, derive(Debug))]
enum EditStart {
    Insert(Action),
    Selection {
        change: bool,
        selector: SelectionIntent,
    },
    Delete,
    Join,
    Paste {
        after: bool,
        fragments: Vec<String>,
    },
}

#[cfg_attr(test, derive(Debug))]
enum SelectionIntent {
    Motions(Vec<(Action, usize)>),
    // Whole graphemes, with a newline counting as one boundary.
    Spans(Vec<usize>),
}

#[cfg_attr(test, derive(Debug))]
enum InsertStep {
    Typed(String),
    Bulk(String),
    Move(Action, usize),
    Delete(Vec<bool>),
    Backspace(Vec<bool>),
}

#[cfg_attr(test, derive(Debug))]
#[derive(Clone, Copy, Eq, PartialEq)]
enum Action {
    Insert,
    InsertFirstNonblank,
    Append,
    AppendLineEnd,
    OpenBelow,
    OpenAbove,
    Left,
    Right,
    Down,
    Up,
    JoinLines,
    LineStart,
    LineEnd,
    Delete,
    Undo,
    Redo,
    RepeatLastEdit,
    Command,
    Normal,
    Newline,
    Backspace,
    Submit,
    Search,
    SearchNext,
    SearchPrevious,
    WordNext,
    WordPrevious,
    WordEnd,
    BigWordNext,
    BigWordPrevious,
    BigWordEnd,
    Select,
    Copy,
    Cut,
    CopySystem,
    Change,
    PasteBefore,
    PasteAfter,
    PasteSystemBefore,
    PasteSystemAfter,
    SelectLines,
    CloneAbove,
    CloneBelow,
    SelectNext,
    SkipOccurrence,
    SelectAll,
    Palette,
    FilePicker,
    FileExplorer,
}

// Names and mode eligibility are shared by configured bindings and the palette.
const CORE_ACTIONS: &[(&str, Action, &[Mode])] = &[
    ("core.insert", Action::Insert, &[Mode::Normal]),
    (
        "core.insert_first_nonblank",
        Action::InsertFirstNonblank,
        &[Mode::Normal, Mode::Visual],
    ),
    ("core.append", Action::Append, &[Mode::Normal]),
    (
        "core.append_line_end",
        Action::AppendLineEnd,
        &[Mode::Normal, Mode::Visual],
    ),
    ("core.open_below", Action::OpenBelow, &[Mode::Normal]),
    ("core.open_above", Action::OpenAbove, &[Mode::Normal]),
    ("core.join_lines", Action::JoinLines, &[Mode::Normal]),
    ("core.undo", Action::Undo, &[Mode::Normal]),
    ("core.redo", Action::Redo, &[Mode::Normal]),
    (
        "core.repeat_last_edit",
        Action::RepeatLastEdit,
        &[Mode::Normal, Mode::Visual],
    ),
    ("core.command", Action::Command, &[Mode::Normal]),
    ("core.search", Action::Search, &[Mode::Normal]),
    (
        "core.search_next",
        Action::SearchNext,
        &[Mode::Normal, Mode::Visual],
    ),
    (
        "core.search_previous",
        Action::SearchPrevious,
        &[Mode::Normal, Mode::Visual],
    ),
    ("core.select", Action::Select, &[Mode::Normal, Mode::Visual]),
    ("core.select_lines", Action::SelectLines, &[Mode::Visual]),
    (
        "core.clone_above",
        Action::CloneAbove,
        &[Mode::Normal, Mode::Visual],
    ),
    (
        "core.clone_below",
        Action::CloneBelow,
        &[Mode::Normal, Mode::Visual],
    ),
    ("core.select_next", Action::SelectNext, &[Mode::Visual]),
    (
        "core.skip_occurrence",
        Action::SkipOccurrence,
        &[Mode::Visual],
    ),
    ("core.select_all", Action::SelectAll, &[Mode::Visual]),
    ("core.copy", Action::Copy, &[Mode::Visual]),
    ("core.copy_system", Action::CopySystem, &[Mode::Visual]),
    ("core.cut", Action::Cut, &[Mode::Visual]),
    ("core.change", Action::Change, &[Mode::Visual]),
    ("core.paste_before", Action::PasteBefore, &[Mode::Normal]),
    ("core.paste_after", Action::PasteAfter, &[Mode::Normal]),
    (
        "core.paste_system_before",
        Action::PasteSystemBefore,
        &[Mode::Normal],
    ),
    (
        "core.paste_system_after",
        Action::PasteSystemAfter,
        &[Mode::Normal],
    ),
    (
        "core.left",
        Action::Left,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.right",
        Action::Right,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.down",
        Action::Down,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.up",
        Action::Up,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.line_start",
        Action::LineStart,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.line_end",
        Action::LineEnd,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.word_next",
        Action::WordNext,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.word_previous",
        Action::WordPrevious,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.word_end",
        Action::WordEnd,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.big_word_next",
        Action::BigWordNext,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.big_word_previous",
        Action::BigWordPrevious,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    (
        "core.big_word_end",
        Action::BigWordEnd,
        &[Mode::Normal, Mode::Insert, Mode::Visual],
    ),
    ("core.delete", Action::Delete, &[Mode::Normal, Mode::Insert]),
    (
        "core.normal",
        Action::Normal,
        &[
            Mode::Normal,
            Mode::Insert,
            Mode::Command,
            Mode::Search,
            Mode::Visual,
        ],
    ),
    ("core.newline", Action::Newline, &[Mode::Insert]),
    (
        "core.backspace",
        Action::Backspace,
        &[Mode::Insert, Mode::Command, Mode::Search],
    ),
    (
        "core.submit",
        Action::Submit,
        &[Mode::Command, Mode::Search],
    ),
    (
        "core.palette",
        Action::Palette,
        &[
            Mode::Normal,
            Mode::Insert,
            Mode::Command,
            Mode::Search,
            Mode::Visual,
        ],
    ),
    (
        "core.file_picker",
        Action::FilePicker,
        &[Mode::Normal, Mode::Visual],
    ),
    (
        "core.file_explorer",
        Action::FileExplorer,
        &[Mode::Normal, Mode::Visual],
    ),
];

impl Action {
    fn named(mode: Mode, name: &str) -> Option<Self> {
        CORE_ACTIONS
            .iter()
            .find(|(candidate, _, modes)| *candidate == name && modes.contains(&mode))
            .map(|(_, action, _)| *action)
    }
}

enum Binding {
    Action(Action),
    Command(String),
    Disabled,
}

fn parse_key(key: &str) -> Result<Input, String> {
    let character = |name: &str| {
        let mut chars = name.chars();
        chars
            .next()
            .filter(|ch| !ch.is_control() && chars.next().is_none())
    };
    // Keep literal punctuation, especially "+", usable without escaping.
    if let Some(ch) = character(key) {
        return Ok(Input::Char(ch));
    }
    let invalid = || format!("Invalid binding key: {key:?}");
    let (modifier, name) = key
        .split_once('+')
        .map_or((None, key), |(modifier, name)| (Some(modifier), name));
    let input = if let Some(ch) = character(name) {
        Input::Char(ch)
    } else {
        [
            ("esc", Input::Escape),
            ("enter", Input::Enter),
            ("backspace", Input::Backspace),
            ("delete", Input::Delete),
            ("left", Input::Left),
            ("right", Input::Right),
            ("up", Input::Up),
            ("down", Input::Down),
            ("home", Input::Home),
            ("end", Input::End),
            ("tab", Input::Char('\t')),
            ("space", Input::Char(' ')),
            ("minus", Input::Char('-')),
            ("comma", Input::Char(',')),
            ("ampersand", Input::Char('&')),
            ("plus", Input::Char('+')),
            ("backtick", Input::Char('`')),
        ]
        .into_iter()
        .find(|(key, _)| name.eq_ignore_ascii_case(key))
        .map(|(_, input)| input)
        .ok_or_else(invalid)?
    };
    match (modifier, input) {
        (None, input) => Ok(input),
        (Some(modifier), Input::Char(ch)) if ch.is_ascii_alphabetic() => {
            if modifier.eq_ignore_ascii_case("ctrl") {
                Ok(control_key(ch))
            } else if modifier.eq_ignore_ascii_case("shift") {
                Ok(Input::Char(ch.to_ascii_uppercase()))
            } else {
                Err(invalid())
            }
        }
        _ => Err(invalid()),
    }
}

fn control_key(ch: char) -> Input {
    // Terminals encode these controls as named keys.
    match ch.to_ascii_lowercase() {
        'i' => Input::Char('\t'),
        'm' => Input::Enter,
        ch => Input::Ctrl(ch),
    }
}

fn display_key(input: &Input) -> String {
    let mut display = String::new();
    append_key(&mut display, input);
    display
}

fn append_key(display: &mut String, input: &Input) {
    use std::fmt::Write as _;
    match input {
        Input::Char('\t') => display.push_str("Tab"),
        Input::Char(' ') => display.push_str("Space"),
        Input::Char(ch) => display.push(*ch),
        Input::Ctrl(ch) => write!(display, "Ctrl+{ch}").expect("writing to a String"),
        Input::Escape => display.push_str("Esc"),
        Input::Enter => display.push_str("Enter"),
        Input::Backspace => display.push_str("Backspace"),
        Input::Delete => display.push_str("Delete"),
        Input::Left => display.push_str("Left"),
        Input::Right => display.push_str("Right"),
        Input::Up => display.push_str("Up"),
        Input::Down => display.push_str("Down"),
        Input::Home => display.push_str("Home"),
        Input::End => display.push_str("End"),
        Input::Paste(_) => unreachable!("paste cannot be bound"),
    }
}

fn default_bindings() -> HashMap<Mode, HashMap<Input, Binding>> {
    use Action::*;
    let mut bindings: HashMap<Mode, HashMap<Input, Binding>> = HashMap::new();
    for (key, action) in [
        ('i', Insert),
        ('I', InsertFirstNonblank),
        ('a', Append),
        ('A', AppendLineEnd),
        ('o', OpenBelow),
        ('O', OpenAbove),
        ('J', JoinLines),
        ('x', Delete),
        ('u', Undo),
        ('U', Redo),
        (':', Command),
        ('/', Search),
        ('p', PasteAfter),
        ('P', PasteBefore),
    ] {
        bindings
            .entry(Mode::Normal)
            .or_default()
            .insert(Input::Char(key), Binding::Action(action));
    }
    for mode in [Mode::Normal, Mode::Visual] {
        for (key, action) in [
            ('h', Left),
            ('j', Down),
            ('k', Up),
            ('l', Right),
            ('0', LineStart),
            ('$', LineEnd),
            ('w', WordNext),
            ('b', WordPrevious),
            ('e', WordEnd),
            ('W', BigWordNext),
            ('B', BigWordPrevious),
            ('E', BigWordEnd),
            ('n', SearchNext),
            ('N', SearchPrevious),
            ('v', Select),
            ('.', RepeatLastEdit),
        ] {
            bindings
                .entry(mode)
                .or_default()
                .insert(Input::Char(key), Binding::Action(action));
        }
        for (key, action) in [
            (Input::Ctrl('k'), CloneAbove),
            (Input::Ctrl('e'), CloneBelow),
            (Input::Escape, Normal),
        ] {
            bindings
                .entry(mode)
                .or_default()
                .insert(key, Binding::Action(action));
        }
    }
    for mode in [Mode::Normal, Mode::Insert, Mode::Visual] {
        for (key, action) in [
            (Input::Left, Left),
            (Input::Right, Right),
            (Input::Down, Down),
            (Input::Up, Up),
            (Input::Home, LineStart),
            (Input::End, LineEnd),
        ] {
            bindings
                .entry(mode)
                .or_default()
                .insert(key, Binding::Action(action));
        }
    }
    for mode in [Mode::Normal, Mode::Insert] {
        bindings
            .entry(mode)
            .or_default()
            .insert(Input::Delete, Binding::Action(Delete));
    }
    bindings
        .entry(Mode::Visual)
        .or_default()
        .insert(Input::Escape, Binding::Action(Normal));
    for (key, action) in [
        (Input::Char('y'), Copy),
        (Input::Char('d'), Cut),
        (Input::Char('c'), Change),
        (Input::Char('x'), Cut),
        (Input::Delete, Cut),
        (Input::Char('I'), InsertFirstNonblank),
        (Input::Char('A'), AppendLineEnd),
        (Input::Ctrl('l'), SelectLines),
        (Input::Ctrl('n'), SelectNext),
        (Input::Ctrl('s'), SkipOccurrence),
        (Input::Ctrl('a'), SelectAll),
    ] {
        bindings
            .entry(Mode::Visual)
            .or_default()
            .insert(key, Binding::Action(action));
    }
    for mode in [Mode::Insert, Mode::Command, Mode::Search] {
        for (key, action) in [
            (Input::Escape, Normal),
            (Input::Backspace, Backspace),
            (
                Input::Enter,
                if mode == Mode::Insert {
                    Newline
                } else {
                    Submit
                },
            ),
            (
                Input::Ctrl('j'),
                if mode == Mode::Insert {
                    Newline
                } else {
                    Submit
                },
            ),
        ] {
            bindings
                .entry(mode)
                .or_default()
                .insert(key, Binding::Action(action));
        }
    }
    for mode in [
        Mode::Normal,
        Mode::Insert,
        Mode::Command,
        Mode::Search,
        Mode::Visual,
    ] {
        bindings
            .entry(mode)
            .or_default()
            .insert(Input::Ctrl('p'), Binding::Action(Palette));
    }
    bindings
}

/// Borrowed buffer-list metadata; paths retain their supplied display/save spelling.
pub struct BufferInfo<'a> {
    pub id: usize,
    pub path: Option<&'a Path>,
    pub dirty: bool,
    pub active: bool,
}

/// Borrowed document state, including hidden and unnamed buffers.
pub struct DocumentInfo<'a> {
    pub id: usize,
    pub revision: u64,
    pub path: Option<&'a Path>,
    pub lines: &'a [String],
    pub save_revision: u64,
}

struct AnnotationSet {
    revision: u64,
    items: Vec<Diagnostic>,
}

struct Buffer {
    id: usize,
    lines: Vec<String>,
    saved_lines: Vec<String>,
    text_revision: u64,
    save_revision: u64,
    diagnostics: BTreeMap<String, AnnotationSet>,
    targets: Vec<Target>,
    primary: usize,
    mode: Mode,
    search_query: String,
    search_match: Option<SearchMatch>,
    path: Option<PathBuf>,
    identity: Option<PathBuf>,
    // ponytail: full-buffer history costs O(buffer size) per action; use edit deltas for large files.
    undo: Vec<Snapshot>,
    redo: Vec<Snapshot>,
    insert_start: Option<Snapshot>,
    pending_edit: Option<EditRecipe>,
    visual_motions: Option<Vec<(Action, usize)>>,
}

impl Buffer {
    fn open(
        id: usize,
        path: Option<PathBuf>,
        identity: Option<PathBuf>,
        allow_missing: bool,
    ) -> io::Result<Self> {
        let text = match &path {
            Some(path) => match fs::read_to_string(path) {
                Ok(text) => text,
                Err(error) if allow_missing && error.kind() == io::ErrorKind::NotFound => {
                    String::new()
                }
                Err(error) => return Err(error),
            },
            None => String::new(),
        };
        validate_text(&text).map_err(|error| io::Error::new(io::ErrorKind::InvalidData, error))?;
        let lines = split_lines(&text);
        Ok(Self {
            id,
            saved_lines: lines.clone(),
            lines,
            text_revision: 0,
            save_revision: 0,
            diagnostics: BTreeMap::new(),
            targets: vec![Target::caret(Cursor::default())],
            primary: 0,
            mode: Mode::Normal,
            search_query: String::new(),
            search_match: None,
            path,
            identity,
            undo: Vec::new(),
            redo: Vec::new(),
            insert_start: None,
            pending_edit: None,
            visual_motions: None,
        })
    }

    fn dirty(&self) -> bool {
        self.lines != self.saved_lines
    }

    fn info(&self, active: bool) -> BufferInfo<'_> {
        BufferInfo {
            id: self.id,
            path: self.path.as_deref(),
            dirty: self.dirty(),
            active,
        }
    }

    fn document(&self) -> DocumentInfo<'_> {
        DocumentInfo {
            id: self.id,
            revision: self.text_revision,
            path: self.path.as_deref(),
            lines: &self.lines,
            save_revision: self.save_revision,
        }
    }

    fn text_changed(&mut self) {
        self.text_revision = self.text_revision.wrapping_add(1);
        self.diagnostics.clear();
    }
}

pub struct Editor {
    active: Buffer,
    parked: BTreeMap<usize, Buffer>,
    next_buffer_id: usize,
    command_line: String,
    clipboard: Vec<String>,
    clipboard_mode: ClipboardMode,
    system_clipboard: SystemClipboard,
    // Exact exported bytes bridge our fragments; external newlines never imply boundaries.
    owned_system_clipboard: Option<(String, Vec<String>)>,
    last_edit: Option<EditRecipe>,
    message: String,
    quit: bool,
    capabilities: Vec<String>,
    features: HashMap<String, Feature>,
    bindings: HashMap<Mode, HashMap<Input, Binding>>,
    selection_bindings: HashMap<Input, Binding>,
    selection_navigation_hint: String,
    tree_bindings: HashMap<Input, Binding>,
    tree_navigation_hint: String,
    tree_filter_navigation_hint: String,
    leader: Input,
    leader_bindings: HashMap<Mode, HashMap<Vec<Input>, Binding>>,
    leader_suffix: Vec<Input>,
    leader_display: String,
    palette: Option<Palette>,
    project_root: PathBuf,
    file_picker: Option<FilePicker>,
    file_explorer_side: DockSide,
    file_picker_view: FileView,
    file_explorer_view: FileView,
    count: Option<usize>,
}

impl Editor {
    pub fn open(path: Option<PathBuf>, capabilities: Vec<String>) -> io::Result<Self> {
        let identity = path.as_deref().map(path_identity).transpose()?;
        let mut editor = Self {
            active: Buffer::open(1, path, identity, true)?,
            parked: BTreeMap::new(),
            next_buffer_id: 2,
            command_line: String::new(),
            clipboard: Vec::new(),
            clipboard_mode: ClipboardMode::System,
            system_clipboard: SystemClipboard::new(),
            owned_system_clipboard: None,
            last_edit: None,
            message: String::new(),
            quit: false,
            capabilities,
            features: HashMap::new(),
            bindings: default_bindings(),
            selection_bindings: [
                (Input::Up, Action::Up),
                (Input::Ctrl('k'), Action::Up),
                (Input::Down, Action::Down),
                (Input::Ctrl('j'), Action::Down),
                (Input::Ctrl('n'), Action::Down),
            ]
            .into_iter()
            .map(|(key, action)| (key, Binding::Action(action)))
            .collect(),
            selection_navigation_hint: String::new(),
            tree_bindings: [
                (Input::Left, Action::Left),
                (Input::Ctrl('h'), Action::Left),
                (Input::Right, Action::Right),
                (Input::Ctrl('l'), Action::Right),
                (Input::Char('h'), Action::Left),
                (Input::Char('j'), Action::Down),
                (Input::Char('k'), Action::Up),
                (Input::Char('l'), Action::Right),
            ]
            .into_iter()
            .map(|(key, action)| (key, Binding::Action(action)))
            .collect(),
            tree_navigation_hint: String::new(),
            tree_filter_navigation_hint: String::new(),
            leader: Input::Char(' '),
            leader_bindings: HashMap::new(),
            leader_suffix: Vec::new(),
            leader_display: String::new(),
            palette: None,
            project_root: std::env::current_dir()?,
            file_picker: None,
            file_explorer_side: DockSide::Right,
            file_picker_view: FileView::Tree,
            file_explorer_view: FileView::Tree,
            count: None,
        };
        editor.refresh_selection_navigation_hint();
        editor
            .install(
                Feature {
                    name: "core".into(),
                    required_capabilities: Vec::new(),
                    commands: [
                        "w", "q", "q!", "wq", "plugins", "edit", "buffers", "buffer", "bnext",
                        "bprev", "bdelete", "bdelete!",
                    ]
                    .into_iter()
                    .map(str::to_owned)
                    .collect(),
                    core: true,
                },
                true,
            )
            .map_err(io::Error::other)?;
        for (mode, key, target) in [
            ("normal", "leader space", "core.palette"),
            ("visual", "leader space", "core.palette"),
            ("normal", "leader o", "core.file_picker"),
            ("visual", "leader o", "core.file_picker"),
            ("normal", "leader e", "core.file_explorer"),
            ("visual", "leader e", "core.file_explorer"),
            ("normal", "leader w", "w"),
            ("normal", "leader b n", "bnext"),
            ("normal", "leader b p", "bprev"),
            ("normal", "leader b l", "buffers"),
            ("normal", "leader b d", "bdelete"),
        ] {
            editor
                .bind(mode, key, Some(target.into()))
                .map_err(io::Error::other)?;
        }
        Ok(editor)
    }

    pub fn clipboard_mode(&self) -> ClipboardMode {
        self.clipboard_mode
    }

    pub fn set_clipboard_mode(&mut self, mode: &str) -> Result<(), String> {
        self.clipboard_mode = if mode.eq_ignore_ascii_case("system") {
            ClipboardMode::System
        } else if mode.eq_ignore_ascii_case("separate") {
            ClipboardMode::Separate
        } else {
            return Err("Clipboard mode must be system or separate".into());
        };
        Ok(())
    }

    #[cfg(test)]
    pub(crate) fn set_system_clipboard(&mut self, clipboard: SystemClipboard) {
        self.system_clipboard = clipboard;
        self.owned_system_clipboard = None;
    }

    /// Stable one-based ID, never reused after a buffer is deleted.
    pub fn buffer_id(&self) -> usize {
        self.active.id
    }

    pub fn buffer_count(&self) -> usize {
        self.parked.len() + 1
    }

    pub fn has_buffer(&self, id: usize) -> bool {
        id == self.active.id || self.parked.contains_key(&id)
    }

    /// All loaded buffers in ascending ID order, without copying their paths.
    pub fn buffers(&self) -> impl Iterator<Item = BufferInfo<'_>> + '_ {
        self.parked
            .range(..self.active.id)
            .map(|(_, buffer)| buffer.info(false))
            .chain(std::iter::once(self.active.info(true)))
            .chain(
                self.parked
                    .range(self.active.id..)
                    .map(|(_, buffer)| buffer.info(false)),
            )
    }

    pub fn documents(&self) -> impl Iterator<Item = DocumentInfo<'_>> + '_ {
        self.parked
            .range(..self.active.id)
            .map(|(_, buffer)| buffer.document())
            .chain(std::iter::once(self.active.document()))
            .chain(
                self.parked
                    .range(self.active.id..)
                    .map(|(_, buffer)| buffer.document()),
            )
    }

    pub fn project_root(&self) -> &Path {
        &self.project_root
    }

    fn buffer(&self, id: usize) -> Option<&Buffer> {
        if id == self.active.id {
            Some(&self.active)
        } else {
            self.parked.get(&id)
        }
    }

    pub fn diagnostics(&self) -> impl Iterator<Item = &Diagnostic> {
        self.active
            .diagnostics
            .values()
            .filter(|annotations| annotations.revision == self.active.text_revision)
            .flat_map(|annotations| &annotations.items)
    }

    pub fn diagnostic_at_cursor(&self) -> Option<&Diagnostic> {
        let cursor = self.cursor();
        let position = TextPosition {
            row: cursor.row,
            column: cursor.column,
        };
        self.diagnostics().find(|diagnostic| {
            diagnostic.start <= position
                && (position < diagnostic.end
                    || (diagnostic.start == diagnostic.end && position == diagnostic.start))
        })
    }

    pub(crate) fn validate_diagnostics(
        &self,
        buffer_id: usize,
        revision: u64,
        items: &[Diagnostic],
    ) -> Result<bool, String> {
        let Some(buffer) = self.buffer(buffer_id) else {
            return Ok(false);
        };
        if buffer.text_revision != revision {
            return Ok(false);
        }
        let mut bytes = 0usize;
        for diagnostic in items {
            for position in [diagnostic.start, diagnostic.end] {
                if buffer
                    .lines
                    .get(position.row)
                    .is_none_or(|line| position.column > grapheme_count(line))
                {
                    return Err("Diagnostic position is outside the document".into());
                }
            }
            if diagnostic.end < diagnostic.start {
                return Err("Diagnostic range is reversed".into());
            }
            if diagnostic.message.chars().any(char::is_control) {
                return Err("Diagnostic messages cannot contain controls".into());
            }
            bytes = bytes
                .checked_add(diagnostic.message.len())
                .ok_or("Diagnostics exceed 4 MiB")?;
            if bytes > MAX_EDIT_BYTES {
                return Err("Diagnostics exceed 4 MiB".into());
            }
        }
        Ok(true)
    }

    pub fn replace_diagnostics(
        &mut self,
        owner: &str,
        buffer_id: usize,
        revision: u64,
        items: Vec<Diagnostic>,
    ) -> Result<bool, String> {
        if !self.validate_diagnostics(buffer_id, revision, &items)? {
            return Ok(false);
        }
        Ok(self.replace_validated_diagnostics(owner, buffer_id, revision, items))
    }

    /// Only session's fully prevalidated batch may use this storage path.
    pub(crate) fn replace_validated_diagnostics(
        &mut self,
        owner: &str,
        buffer_id: usize,
        revision: u64,
        items: Vec<Diagnostic>,
    ) -> bool {
        let buffer = if buffer_id == self.active.id {
            &mut self.active
        } else if let Some(buffer) = self.parked.get_mut(&buffer_id) {
            buffer
        } else {
            return false;
        };
        if buffer.text_revision != revision {
            return false;
        }
        if items.is_empty() {
            return buffer.diagnostics.remove(owner).is_some();
        }
        if buffer.diagnostics.get(owner).is_some_and(|annotations| {
            annotations.revision == revision && annotations.items == items
        }) {
            return false;
        }
        buffer
            .diagnostics
            .insert(owner.to_owned(), AnnotationSet { revision, items });
        true
    }

    pub fn clear_plugin_diagnostics(&mut self, owner: &str) {
        self.active.diagnostics.remove(owner);
        for buffer in self.parked.values_mut() {
            buffer.diagnostics.remove(owner);
        }
    }

    /// Reuses loaded (including dirty) buffers and leaves the source unchanged on failure.
    pub fn navigate_to(&mut self, path: PathBuf, position: TextPosition) -> Result<(), String> {
        if path.as_os_str().is_empty() || path.to_string_lossy().chars().any(char::is_control) {
            return Err("Navigation path must be nonempty and contain no controls".into());
        }
        self.edit_buffer(path, false)
            .map_err(|error| error.to_string())?;
        self.park_source();
        self.active.mode = Mode::Normal;
        let row = position.row.min(self.active.lines.len() - 1);
        let column = position
            .column
            .min(grapheme_count(&self.active.lines[row]).saturating_sub(1));
        self.active.targets = vec![Target::caret(Cursor { row, column })];
        self.active.primary = 0;
        self.active.search_match = None;
        self.active.visual_motions = None;
        self.normalize_targets();
        Ok(())
    }

    pub fn lines(&self) -> &[String] {
        &self.active.lines
    }
    /// Changes only when this buffer's text changes, independent of cursor/view state.
    pub fn text_revision(&self) -> u64 {
        self.active.text_revision
    }
    pub fn cursor(&self) -> Cursor {
        self.active.targets[self.active.primary].active
    }
    pub fn mode(&self) -> Mode {
        self.active.mode
    }
    /// Read-only display state for the overlay; opening it does not change mode.
    pub fn palette(&self) -> Option<&Palette> {
        self.palette.as_ref()
    }

    pub fn file_picker(&self) -> Option<&FilePicker> {
        self.file_picker.as_ref()
    }

    pub fn file_explorer_side(&self) -> DockSide {
        self.file_explorer_side
    }

    pub fn set_file_explorer_side(&mut self, side: &str) -> Result<(), String> {
        self.file_explorer_side = match side.to_ascii_lowercase().as_str() {
            "left" => DockSide::Left,
            "right" => DockSide::Right,
            "top" => DockSide::Top,
            "bottom" => DockSide::Bottom,
            _ => return Err(format!("Invalid file explorer side: {side:?}")),
        };
        Ok(())
    }

    pub fn file_picker_view(&self) -> FileView {
        self.file_picker_view
    }

    pub fn file_explorer_view(&self) -> FileView {
        self.file_explorer_view
    }

    pub fn set_file_picker_view(&mut self, view: &str) -> Result<(), String> {
        self.set_file_view(view, FilePresentation::Floating)
    }

    pub fn set_file_explorer_view(&mut self, view: &str) -> Result<(), String> {
        self.set_file_view(view, FilePresentation::Docked)
    }

    fn set_file_view(&mut self, view: &str, presentation: FilePresentation) -> Result<(), String> {
        let view = match view.to_ascii_lowercase().as_str() {
            "list" => FileView::List,
            "tree" => FileView::Tree,
            _ => return Err(format!("Invalid file view: {view:?}")),
        };
        match presentation {
            FilePresentation::Floating => self.file_picker_view = view,
            FilePresentation::Docked => self.file_explorer_view = view,
        }
        if let Some(picker) = self
            .file_picker
            .as_mut()
            .filter(|picker| picker.presentation == presentation)
        {
            picker.set_view(view);
        }
        Ok(())
    }

    #[cfg(test)]
    pub(crate) fn set_project_root(&mut self, root: PathBuf) {
        self.project_root = root;
    }
    /// Pending decimal prefix for the next Normal/Visual motion.
    pub fn count(&self) -> Option<usize> {
        self.count
    }
    /// Actual pending leader prefix, cached until the next input.
    pub fn leader_pending(&self) -> Option<&str> {
        (!self.leader_display.is_empty()).then_some(self.leader_display.as_str())
    }

    fn clear_leader(&mut self) {
        self.leader_suffix.clear();
        self.leader_display.clear();
    }

    fn cancel_leader(&mut self) {
        if self.leader_pending().is_some() {
            self.count = None;
            self.clear_leader();
        }
    }

    /// Changes the symbolic leader without moving its bindings.
    pub fn set_leader(&mut self, key: &str) -> Result<(), String> {
        let leader = parse_key(key)?;
        if leader == Input::Escape || matches!(leader, Input::Char(ch) if ch.is_ascii_digit()) {
            return Err("Leader cannot be Escape or an ASCII digit".into());
        }
        if leader != self.leader
            && [Mode::Normal, Mode::Visual].into_iter().any(|mode| {
                self.bindings
                    .get(&mode)
                    .is_some_and(|keys| keys.contains_key(&leader))
            })
        {
            return Err(format!(
                "Leader key already bound: {}",
                display_key(&leader)
            ));
        }
        self.cancel_leader();
        self.leader = leader;
        self.refresh_palette();
        Ok(())
    }
    /// Editable Ex/search prompt, without its `:` or `/` prefix.
    pub fn command_line(&self) -> &str {
        &self.command_line
    }
    pub fn search_match(&self) -> Option<SearchMatch> {
        self.active.search_match
    }
    /// Ordered, end-exclusive Visual ranges in document order; empty in other modes.
    pub fn selections(&self) -> Vec<Selection> {
        if self.active.mode == Mode::Visual {
            self.active
                .targets
                .iter()
                .map(|target| self.target_range(*target))
                .collect()
        } else {
            Vec::new()
        }
    }
    /// All active cursors in document order, including the primary cursor.
    pub fn carets(&self) -> Vec<Cursor> {
        self.active
            .targets
            .iter()
            .map(|target| target.active)
            .collect()
    }
    pub fn selection_count(&self) -> usize {
        self.active.targets.len()
    }
    pub fn message(&self) -> &str {
        &self.message
    }
    pub fn path(&self) -> Option<&Path> {
        self.active.path.as_deref()
    }
    pub fn dirty(&self) -> bool {
        self.active.dirty()
    }
    pub fn should_quit(&self) -> bool {
        self.quit
    }

    pub fn context(&self) -> Context {
        Context {
            buffer_id: self.active.id,
            revision: self.active.text_revision,
            root: self.project_root.to_string_lossy().into_owned(),
            text: self.active.lines.join("\n"),
            row: self.cursor().row + 1,
            column: self.cursor().column + 1,
            mode: self.active.mode.to_string(),
            path: self
                .active
                .path
                .as_ref()
                .map(|path| path.to_string_lossy().into_owned()),
        }
    }

    pub fn set_message(&mut self, message: impl Into<String>) {
        let message = message.into();
        self.message = if message.chars().any(char::is_control) {
            message
                .chars()
                .map(|ch| if ch.is_control() { ' ' } else { ch })
                .collect()
        } else {
            message
        };
    }

    pub fn register(&mut self, feature: Feature) -> Result<(), String> {
        self.install(feature, false)
    }

    fn install(&mut self, feature: Feature, privileged: bool) -> Result<(), String> {
        if feature.core && !privileged {
            return Err("Plugins cannot register core features".into());
        }
        if feature.name.trim().is_empty() || feature.name.chars().any(char::is_control) {
            return Err("Feature names must be nonempty and contain no controls".into());
        }
        if self.features.contains_key(&feature.name) {
            return Err(format!("Feature already registered: {}", feature.name));
        }
        for capability in &feature.required_capabilities {
            if !self.capabilities.contains(capability) {
                return Err(format!(
                    "Feature {} requires unavailable capability: {capability}",
                    feature.name
                ));
            }
        }
        let mut names = HashSet::new();
        for command in &feature.commands {
            if !valid_command(command) {
                return Err(format!("Invalid command name: {command}"));
            }
            if !names.insert(command.as_str()) || self.owner(command).is_some() {
                return Err(format!("Command already registered: {command}"));
            }
        }
        self.features.insert(feature.name.clone(), feature);
        self.refresh_palette();
        Ok(())
    }

    fn owner(&self, command: &str) -> Option<&Feature> {
        self.features
            .values()
            .find(|feature| feature.commands.iter().any(|name| name == command))
    }

    pub fn disable_plugin(&mut self, name: &str, reason: &str) {
        self.cancel_leader();
        if self.features.get(name).is_some_and(|feature| feature.core) {
            self.set_message("Core features cannot be disabled");
            return;
        }
        self.clear_plugin_diagnostics(name);
        if let Some(feature) = self.features.remove(name) {
            for bindings in self.bindings.values_mut() {
                bindings.retain(|_, binding| {
                    !matches!(binding, Binding::Command(command) if feature.commands.contains(command))
                });
            }
            for bindings in self.leader_bindings.values_mut() {
                bindings.retain(|_, binding| {
                    !matches!(binding, Binding::Command(command) if feature.commands.contains(command))
                });
            }
        }
        self.refresh_palette();
        self.set_message(format!("Plugin {name} disabled: {reason}"));
    }

    /// Overrides an editing route or single selection/tree navigation key.
    /// `None` disables it; invalid overrides are atomic.
    pub fn bind(&mut self, mode: &str, key: &str, target: Option<String>) -> Result<(), String> {
        if matches!(mode, "selection" | "tree") {
            let input = parse_key(key)?;
            let binding = match target.as_deref() {
                None => Binding::Disabled,
                Some("core.up") => Binding::Action(Action::Up),
                Some("core.down") => Binding::Action(Action::Down),
                Some("core.left") if mode == "tree" => Binding::Action(Action::Left),
                Some("core.right") if mode == "tree" => Binding::Action(Action::Right),
                Some(target) => return Err(format!("Unknown {mode} action: {target}")),
            };
            if mode == "tree" {
                self.tree_bindings.insert(input, binding);
            } else {
                self.selection_bindings.insert(input, binding);
            }
            self.refresh_selection_navigation_hint();
            return Ok(());
        }
        let mode = match mode {
            "normal" => Mode::Normal,
            "insert" => Mode::Insert,
            "command" => Mode::Command,
            "search" => Mode::Search,
            "visual" => Mode::Visual,
            _ => return Err(format!("Unknown binding mode: {mode}")),
        };
        let mut tokens = key.split_whitespace();
        let suffix = if tokens
            .next()
            .is_some_and(|token| token.eq_ignore_ascii_case("leader"))
        {
            if !matches!(mode, Mode::Normal | Mode::Visual) {
                return Err("Leader sequences can only be bound in Normal or Visual mode".into());
            }
            let suffix: Vec<_> = tokens.map(parse_key).collect::<Result<_, _>>()?;
            if suffix.is_empty() {
                return Err("Leader binding requires at least one suffix key".into());
            }
            if self.leader_bindings.get(&mode).is_some_and(|bindings| {
                bindings.keys().any(|existing| {
                    *existing != suffix
                        && (existing.starts_with(&suffix) || suffix.starts_with(existing))
                })
            }) {
                return Err(format!("Ambiguous leader binding: {key:?}"));
            }
            Some(suffix)
        } else {
            None
        };
        let input = if suffix.is_none() {
            Some(parse_key(key)?)
        } else {
            None
        };
        let binding = match target {
            None => Binding::Disabled,
            Some(target) if target.starts_with("core.") => Binding::Action(
                Action::named(mode, &target)
                    .ok_or_else(|| format!("Unknown action for {mode}: {target}"))?,
            ),
            Some(command) => {
                if mode != Mode::Normal {
                    return Err("Ex/plugin commands can only be bound in Normal mode".into());
                }
                if self.owner(&command).is_none() {
                    return Err(format!("Unknown command: {command}"));
                }
                Binding::Command(command)
            }
        };
        self.cancel_leader();
        if let Some(suffix) = suffix {
            self.leader_bindings
                .entry(mode)
                .or_default()
                .insert(suffix, binding);
        } else {
            self.bindings
                .entry(mode)
                .or_default()
                .insert(input.expect("single-key binding"), binding);
        }
        self.refresh_palette();
        Ok(())
    }

    pub fn selection_navigation_hint(&self) -> &str {
        &self.selection_navigation_hint
    }

    pub fn file_navigation_hint(&self) -> &str {
        if let Some(picker) = &self.file_picker
            && picker.view == FileView::Tree
        {
            if picker.searching {
                &self.tree_filter_navigation_hint
            } else {
                &self.tree_navigation_hint
            }
        } else {
            &self.selection_navigation_hint
        }
    }

    fn refresh_selection_navigation_hint(&mut self) {
        let keys = |action, tree: bool, filtering: bool| {
            let applies = |input: &Input| tree && (!filtering || !matches!(input, Input::Char(_)));
            let mut keys: Vec<_> = self
                .selection_bindings
                .iter()
                .filter(|(key, _)| !applies(key) || !self.tree_bindings.contains_key(*key))
                .chain(self.tree_bindings.iter().filter(|(key, _)| applies(key)))
                .filter(
                    |(_, binding)| matches!(binding, Binding::Action(bound) if *bound == action),
                )
                .map(|(input, _)| {
                    let priority =
                        usize::from(!(tree && !filtering && matches!(input, Input::Char(_))));
                    (priority, display_key(input))
                })
                .collect();
            keys.sort();
            if keys.is_empty() {
                "unbound".into()
            } else {
                let capacity =
                    keys.iter().map(|(_, key)| key.len()).sum::<usize>() + keys.len() - 1;
                let mut hint = String::with_capacity(capacity);
                for (_, key) in keys {
                    if !hint.is_empty() {
                        hint.push('/');
                    }
                    hint.push_str(&key);
                }
                hint
            }
        };
        self.selection_navigation_hint = format!(
            "{} next · {} previous",
            keys(Action::Down, false, false),
            keys(Action::Up, false, false)
        );
        self.tree_navigation_hint = format!(
            "{} next · {} previous · {} parent/close · {} open/child",
            keys(Action::Down, true, false),
            keys(Action::Up, true, false),
            keys(Action::Left, true, false),
            keys(Action::Right, true, false)
        );
        self.tree_filter_navigation_hint = format!(
            "{} next · {} previous · {} parent · {} child",
            keys(Action::Down, true, true),
            keys(Action::Up, true, true),
            keys(Action::Left, true, true),
            keys(Action::Right, true, true)
        );
    }

    fn handle_tree_binding(&mut self, input: &Input) -> bool {
        let Some(picker) = self
            .file_picker
            .as_mut()
            .filter(|picker| picker.focused && picker.view == FileView::Tree)
        else {
            return false;
        };
        if picker.searching && matches!(input, Input::Char(_)) {
            return false;
        }
        match self.tree_bindings.get(input) {
            Some(Binding::Action(Action::Down)) => picker.navigate(true),
            Some(Binding::Action(Action::Up)) => picker.navigate(false),
            Some(Binding::Action(Action::Left)) => picker.left(),
            Some(Binding::Action(Action::Right)) => picker.right(),
            Some(Binding::Disabled) => {}
            None => return false,
            _ => unreachable!("tree bindings only accept navigation or disabled"),
        }
        true
    }

    fn handle_selection_binding(&mut self, input: &Input) -> bool {
        let next = match self.selection_bindings.get(input) {
            Some(Binding::Action(Action::Down)) => true,
            Some(Binding::Action(Action::Up)) => false,
            Some(Binding::Disabled) => return true,
            None => return false,
            _ => unreachable!("selection bindings only accept navigation or disabled"),
        };
        if let Some(picker) = self.file_picker.as_mut().filter(|picker| picker.focused) {
            picker.navigate(next);
        } else if let Some(palette) = self.palette.as_mut()
            && !palette.entries.is_empty()
        {
            palette.selected = if next {
                (palette.selected + 1) % palette.entries.len()
            } else if palette.selected == 0 {
                palette.entries.len() - 1
            } else {
                palette.selected - 1
            };
        }
        true
    }

    fn palette_bindings(&self, action: Option<Action>, command: &str) -> Vec<String> {
        // ponytail: scan mode bindings per result; index by target if catalogs grow.
        let mut bindings: Vec<_> = self
            .bindings
            .get(&self.active.mode)
            .into_iter()
            .flat_map(|keys| keys.iter())
            .filter(|(_, binding)| match (action, binding) {
                (Some(action), Binding::Action(bound)) => action == *bound,
                (None, Binding::Command(bound)) => command == bound,
                _ => false,
            })
            .map(|(input, _)| display_key(input))
            .collect();
        if !self
            .bindings
            .get(&self.active.mode)
            .is_some_and(|keys| keys.contains_key(&self.leader))
        {
            for (suffix, binding) in self
                .leader_bindings
                .get(&self.active.mode)
                .into_iter()
                .flat_map(|keys| keys.iter())
            {
                if match (action, binding) {
                    (Some(action), Binding::Action(bound)) => action == *bound,
                    (None, Binding::Command(bound)) => command == bound,
                    _ => false,
                } {
                    let mut display = display_key(&self.leader);
                    for input in suffix {
                        display.push(' ');
                        append_key(&mut display, input);
                    }
                    bindings.push(display);
                }
            }
        }
        bindings.sort();
        bindings
    }

    fn refresh_palette(&mut self) {
        let Some(mut palette) = self.palette.take() else {
            return;
        };
        let query = palette.query.to_lowercase();
        // Derived labels contain the same searchable words as their names.
        let matches = |name: &str, owner: &str| {
            query
                .split_whitespace()
                .all(|token| name.contains(token) || owner.contains(token))
        };
        palette.entries.clear();
        for &(name, action, modes) in CORE_ACTIONS {
            if action == Action::Palette {
                continue;
            }
            if !matches(name, "core") {
                continue;
            }
            let mut label = name.trim_start_matches("core.").replace('_', " ");
            label[..1].make_ascii_uppercase();
            palette.entries.push(PaletteEntry {
                name: name.into(),
                label,
                owner: "core".into(),
                bindings: self.palette_bindings(Some(action), ""),
                enabled: modes.contains(&self.active.mode),
                modes: modes.to_vec(),
            });
        }
        for feature in self.features.values() {
            let owner = feature.name.to_lowercase();
            for command in &feature.commands {
                let name = command.to_lowercase();
                if !matches(&name, &owner) {
                    continue;
                }
                palette.entries.push(PaletteEntry {
                    name: command.clone(),
                    label: command.clone(),
                    owner: feature.name.clone(),
                    bindings: self.palette_bindings(None, command),
                    enabled: self.active.mode == Mode::Normal,
                    modes: vec![Mode::Normal],
                });
            }
        }
        palette.entries.sort_by(|left, right| {
            left.label
                .cmp(&right.label)
                .then_with(|| left.name.cmp(&right.name))
        });
        palette.selected = 0;
        self.palette = Some(palette);
    }

    fn handle_palette(&mut self, input: Input) -> Option<Invocation> {
        let palette = self.palette.as_mut().expect("open palette receives input");
        match input {
            Input::Escape | Input::Ctrl('p') => self.palette = None,
            Input::Enter => {
                let entry = palette
                    .entries
                    .get(palette.selected)
                    .filter(|entry| entry.enabled)?;
                if let Some(action) = Action::named(self.active.mode, &entry.name) {
                    self.palette = None;
                    return self.act(action);
                }
                self.command_line = format!("{} ", entry.name);
                self.palette = None;
                if self.active.mode == Mode::Insert {
                    self.finish_insert();
                }
                self.active.mode = Mode::Command;
            }
            Input::Backspace => {
                if let Some((byte, _)) = palette.query.grapheme_indices(true).next_back() {
                    palette.query.truncate(byte);
                    self.refresh_palette();
                }
            }
            Input::Char(ch) if !ch.is_control() => {
                palette.query.push(ch);
                self.refresh_palette();
            }
            _ => {}
        }
        None
    }

    fn open_file_picker(&mut self, presentation: FilePresentation) {
        let view = match presentation {
            FilePresentation::Floating => self.file_picker_view,
            FilePresentation::Docked => self.file_explorer_view,
        };
        if let Some(picker) = &mut self.file_picker {
            picker.presentation = presentation;
            picker.set_view(view);
            picker.focused = true;
            picker.clear_error();
        } else {
            match FilePicker::scan(self.project_root.clone(), presentation, view) {
                Ok(picker) => {
                    self.file_picker = Some(picker);
                }
                Err(error) => {
                    self.set_message(format!("File scan failed: {error}"));
                    return;
                }
            }
        }
        if presentation == FilePresentation::Floating
            && view == FileView::Tree
            && let Some(picker) = &mut self.file_picker
            && !picker.searching
        {
            picker.start_search();
        }
        self.palette = None;
        self.count = None;
        self.clear_leader();
    }

    fn blur_file_picker(&mut self) {
        match self.file_picker.as_mut() {
            Some(picker) if picker.presentation == FilePresentation::Docked => {
                picker.focused = false;
            }
            _ => self.file_picker = None,
        }
    }

    fn handle_file_picker(&mut self, input: Input) {
        let picker = self
            .file_picker
            .as_mut()
            .expect("focused picker receives input");
        match input {
            Input::Ctrl('w') => self.file_picker = None,
            Input::Escape if picker.view == FileView::Tree && picker.searching => {
                picker.finish_search()
            }
            Input::Escape => self.blur_file_picker(),
            Input::Ctrl('p') => {
                self.act(Action::Palette);
            }
            Input::Char('\t') if picker.presentation == FilePresentation::Docked => {
                picker.focused = false;
            }
            Input::Ctrl('r') => picker.refresh(),
            Input::Ctrl('t') => picker.toggle_view(),
            Input::Ctrl('u') => picker.clear_filter(),
            Input::Backspace if picker.view == FileView::List || picker.searching => {
                picker.backspace()
            }
            Input::Char('i') if picker.view == FileView::Tree && !picker.searching => {
                picker.start_search()
            }
            Input::Char(ch)
                if !ch.is_control() && (picker.view == FileView::List || picker.searching) =>
            {
                picker.query.push(ch);
                picker.refilter();
            }
            Input::Enter => {
                let Some(path) = picker.accept() else { return };
                match self.edit_buffer(path, false) {
                    Ok(()) => self.blur_file_picker(),
                    Err(error) => {
                        self.file_picker
                            .as_mut()
                            .expect("failed open retains picker")
                            .error = Some(format!("Open failed: {error}"));
                    }
                }
            }
            _ => {}
        }
    }

    pub fn handle(&mut self, input: Input) -> Option<Invocation> {
        // Normalize genuine terminal aliases before list and editing dispatch.
        let input = match input {
            Input::Ctrl(ch) => control_key(ch),
            input => input,
        };
        let picker_focused = self
            .file_picker
            .as_ref()
            .is_some_and(|picker| picker.focused);
        if picker_focused && self.handle_tree_binding(&input) {
            return None;
        }
        if (picker_focused || self.palette.is_some()) && self.handle_selection_binding(&input) {
            return None;
        }
        if picker_focused {
            self.handle_file_picker(input);
            return None;
        }
        if self.palette.is_some() {
            return self.handle_palette(input);
        }
        // Paste is literal input, never a configurable key or command.
        if let Input::Paste(text) = input {
            self.count = None;
            self.clear_leader();
            if self.active.mode == Mode::Insert {
                self.paste(&text);
            }
            return None;
        }
        if self.leader_pending().is_some() {
            if input == Input::Escape {
                self.cancel_leader();
                return None;
            }
            return self.handle_leader(input);
        }
        if input == Input::Escape && self.count.take().is_some() {
            return None;
        }
        if matches!(self.active.mode, Mode::Normal | Mode::Visual)
            && let Input::Char(ch @ '0'..='9') = input
        {
            let binding = self
                .bindings
                .get(&self.active.mode)
                .and_then(|keys| keys.get(&input));
            let extends_count = ch == '0'
                && self.count.is_some()
                && matches!(binding, Some(Binding::Action(Action::LineStart)));
            if (binding.is_none() || extends_count) && (ch != '0' || self.count.is_some()) {
                let digit = usize::from(ch as u8 - b'0');
                self.count = Some(
                    self.count
                        .unwrap_or(0)
                        .saturating_mul(10)
                        .saturating_add(digit),
                );
                return None;
            }
        }
        match self
            .bindings
            .get(&self.active.mode)
            .and_then(|keys| keys.get(&input))
        {
            Some(Binding::Action(action)) => return self.act(*action),
            Some(Binding::Command(command)) => {
                let command = command.clone();
                return self.execute(&command);
            }
            Some(Binding::Disabled) => {
                self.count = None;
                return None;
            }
            None => {}
        }
        if matches!(self.active.mode, Mode::Normal | Mode::Visual) && input == self.leader {
            append_key(&mut self.leader_display, &input);
            return None;
        }
        self.count = None;
        match (self.active.mode, input) {
            (Mode::Insert, Input::Char(ch)) if !ch.is_control() || ch == '\t' => {
                let mut bytes = [0; 4];
                self.type_native(ch.encode_utf8(&mut bytes));
            }
            (Mode::Command | Mode::Search, Input::Char(ch))
                if !ch.is_control() || (self.active.mode == Mode::Search && ch == '\t') =>
            {
                self.command_line.push(ch);
            }
            _ => {}
        }
        None
    }

    fn handle_leader(&mut self, input: Input) -> Option<Invocation> {
        self.leader_display.push(' ');
        append_key(&mut self.leader_display, &input);
        self.leader_suffix.push(input);
        let bindings = self.leader_bindings.get(&self.active.mode);
        match bindings.and_then(|keys| keys.get(self.leader_suffix.as_slice())) {
            Some(Binding::Action(action)) => return self.act(*action),
            Some(Binding::Command(command)) => {
                let command = command.clone();
                return self.execute(&command);
            }
            Some(Binding::Disabled) => {
                self.cancel_leader();
                return None;
            }
            None => {}
        }
        // ponytail: scan finite leader routes; use a trie if catalogs grow large.
        if bindings.is_some_and(|keys| {
            keys.keys()
                .any(|suffix| suffix.starts_with(&self.leader_suffix))
        }) {
            return None;
        }
        self.set_message(format!("Unknown leader sequence: {}", self.leader_display));
        self.cancel_leader();
        None
    }

    fn act(&mut self, action: Action) -> Option<Invocation> {
        let count = self.count.take().unwrap_or(1);
        self.clear_leader();
        match action {
            Action::Palette => {
                self.blur_file_picker();
                self.palette = Some(Palette {
                    query: String::new(),
                    entries: Vec::new(),
                    selected: 0,
                });
                self.refresh_palette();
            }
            Action::FilePicker => self.open_file_picker(FilePresentation::Floating),
            Action::FileExplorer => self.open_file_picker(FilePresentation::Docked),
            Action::Insert
            | Action::InsertFirstNonblank
            | Action::AppendLineEnd
            | Action::Append
            | Action::OpenBelow
            | Action::OpenAbove => {
                let before = self.snapshot();
                if self.active.mode == Mode::Visual {
                    self.split_rows(matches!(action, Action::AppendLineEnd), true);
                }
                self.start_insert(before, EditStart::Insert(action));
                self.place_insert(action);
            }
            Action::Left
            | Action::Right
            | Action::Down
            | Action::Up
            | Action::LineStart
            | Action::LineEnd
            | Action::WordNext
            | Action::WordPrevious
            | Action::WordEnd
            | Action::BigWordNext
            | Action::BigWordPrevious
            | Action::BigWordEnd => {
                if self.active.mode == Mode::Visual {
                    if let Some(motions) = &mut self.active.visual_motions {
                        motions.push((action, count));
                    }
                } else if self.active.mode == Mode::Insert {
                    self.push_insert_step(InsertStep::Move(action, count));
                }
                self.move_targets(action, count);
            }
            Action::JoinLines => {
                let before = self.snapshot();
                self.join_lines();
                self.record_native(
                    before,
                    EditRecipe {
                        start: EditStart::Join,
                        steps: Vec::new(),
                    },
                );
            }
            Action::Delete => {
                let before = (self.active.mode != Mode::Insert).then(|| self.snapshot());
                let mask = self.deletion_mask(false);
                self.delete_forward(&mask);
                if let Some(before) = before {
                    self.record_native(
                        before,
                        EditRecipe {
                            start: EditStart::Delete,
                            steps: Vec::new(),
                        },
                    );
                } else if mask.iter().any(|active| *active) {
                    self.push_insert_step(InsertStep::Delete(mask));
                }
            }
            Action::Undo => self.undo(),
            Action::Redo => self.redo(),
            Action::RepeatLastEdit => self.repeat_last_edit(),
            Action::Command | Action::Search => {
                self.active.mode = if matches!(action, Action::Search) {
                    Mode::Search
                } else {
                    Mode::Command
                };
                self.command_line.clear();
            }
            Action::SearchNext => self.seek_search(true, count),
            Action::SearchPrevious => self.seek_search(false, count),
            Action::Select => {
                if self.active.mode == Mode::Visual {
                    self.clear_selection();
                } else {
                    for target in &mut self.active.targets {
                        target.anchor = target.active;
                    }
                    self.active.mode = Mode::Visual;
                    self.active.visual_motions = Some(Vec::new());
                    self.normalize_targets();
                    self.message.clear();
                }
            }
            Action::SelectLines => self.split_rows(false, false),
            Action::CloneAbove => self.clone_vertical(false),
            Action::CloneBelow => self.clone_vertical(true),
            Action::SelectNext | Action::SkipOccurrence | Action::SelectAll => {
                self.select_occurrences(action);
            }
            Action::Copy | Action::CopySystem | Action::Cut | Action::Change => {
                self.edit_selection(action)
            }
            Action::PasteBefore | Action::PasteAfter => self.paste_clipboard(
                matches!(action, Action::PasteAfter),
                self.clipboard_mode == ClipboardMode::System,
            ),
            Action::PasteSystemBefore | Action::PasteSystemAfter => {
                self.paste_clipboard(matches!(action, Action::PasteSystemAfter), true)
            }
            Action::Normal => {
                if self.active.mode == Mode::Normal {
                    self.collapse_primary();
                } else if self.active.mode == Mode::Insert {
                    self.finish_insert();
                    self.leave_insert();
                } else {
                    self.command_line.clear();
                    self.active.visual_motions = None;
                    self.active.mode = Mode::Normal;
                    self.normalize_targets();
                }
            }
            Action::Newline => self.type_native("\n"),
            Action::Backspace => {
                if self.active.mode == Mode::Insert {
                    let mask = self.deletion_mask(true);
                    self.backspace(&mask);
                    if mask.iter().any(|active| *active) {
                        self.push_insert_step(InsertStep::Backspace(mask));
                    }
                } else if let Some((byte, _)) = self.command_line.grapheme_indices(true).next_back()
                {
                    self.command_line.truncate(byte);
                }
            }
            Action::Submit => {
                let command = std::mem::take(&mut self.command_line);
                let searching = self.active.mode == Mode::Search;
                self.active.mode = Mode::Normal;
                if searching {
                    if !command.is_empty() {
                        self.active.search_query = command;
                    }
                    self.seek_search(true, 1);
                } else {
                    return self.execute(&command);
                }
            }
        }
        None
    }

    fn seek_search(&mut self, forward: bool, count: usize) {
        self.active.search_match = None;
        if self.active.search_query.is_empty() {
            self.set_message("No previous search");
            return;
        }
        let query = self.active.search_query.as_str();
        // ponytail: O(buffer graphemes × query bytes) scan; index matches if large buffers need it.
        let matches: Vec<_> = self
            .active
            .lines
            .iter()
            .enumerate()
            .flat_map(|(row, line)| {
                line.grapheme_indices(true).filter_map(move |(byte, _)| {
                    (line[byte..].starts_with(query)
                        && GraphemeCursor::new(byte + query.len(), line.len(), true)
                            .is_boundary(line, 0)
                            .expect("complete line supplies grapheme context"))
                    .then_some((row, byte))
                })
            })
            .collect();
        if matches.is_empty() {
            self.set_message(format!("Not found: {}", self.active.search_query));
            return;
        }
        for (index, target) in self.active.targets.iter_mut().enumerate() {
            let origin = (
                target.active.row,
                grapheme_byte(&self.active.lines[target.active.row], target.active.column),
            );
            let first = if forward {
                matches.partition_point(|position| *position <= origin) % matches.len()
            } else {
                matches
                    .partition_point(|position| *position < origin)
                    .checked_sub(1)
                    .unwrap_or(matches.len() - 1)
            };
            let distance = (count - 1) % matches.len();
            let destination = if forward {
                (first + distance) % matches.len()
            } else {
                (first + matches.len() - distance) % matches.len()
            };
            let found = matches[destination];
            target.active = Cursor {
                row: found.0,
                column: column_after_byte(&self.active.lines[found.0], found.1),
            };
            target.preferred_columns = None;
            if index == self.active.primary {
                self.active.search_match = Some(SearchMatch {
                    start: target.active,
                    end_column: target.active.column + grapheme_count(query),
                });
            }
        }
        self.active.visual_motions = None;
        self.normalize_targets();
        self.message.clear();
    }

    fn park_source(&mut self) {
        if self.active.mode == Mode::Insert {
            self.finish_insert();
        }
        if matches!(
            self.active.mode,
            Mode::Insert | Mode::Command | Mode::Search
        ) {
            self.active.mode = Mode::Normal;
            self.normalize_targets();
        }
        self.command_line.clear();
        self.count = None;
        self.clear_leader();
        self.palette = None;
    }

    fn activate(&mut self, buffer: Buffer) {
        self.park_source();
        let previous = std::mem::replace(&mut self.active, buffer);
        self.parked.insert(previous.id, previous);
        self.show_buffer();
    }

    fn show_buffer(&mut self) {
        let path = self
            .path()
            .map_or_else(|| Cow::Borrowed("[No Name]"), Path::to_string_lossy);
        self.set_message(format!("Buffer {}: {path}", self.active.id));
    }

    fn switch_buffer(&mut self, id: usize) {
        if id == self.active.id {
            self.park_source();
            self.show_buffer();
        } else if let Some(buffer) = self.parked.remove(&id) {
            self.activate(buffer);
        } else {
            self.set_message(format!("No buffer: {id}"));
        }
    }

    fn adjacent_buffer(&self, forward: bool) -> usize {
        use std::ops::Bound::{Excluded, Unbounded};
        let id = self.active.id;
        if forward {
            self.parked
                .range((Excluded(id), Unbounded))
                .next()
                .or_else(|| self.parked.first_key_value())
        } else {
            self.parked
                .range(..id)
                .next_back()
                .or_else(|| self.parked.last_key_value())
        }
        .map_or(id, |(id, _)| *id)
    }

    fn edit_buffer(&mut self, path: PathBuf, allow_missing: bool) -> io::Result<()> {
        let identity = path_identity(&path)?;
        let loaded = std::iter::once(&self.active)
            .chain(self.parked.values())
            .find(|buffer| buffer.identity.as_ref() == Some(&identity))
            .map(|buffer| buffer.id);
        if let Some(id) = loaded {
            self.switch_buffer(id);
            return Ok(());
        }
        let buffer = Buffer::open(
            self.next_buffer_id,
            Some(path),
            Some(identity),
            allow_missing,
        )?;
        self.next_buffer_id += 1;
        self.activate(buffer);
        Ok(())
    }

    fn delete_buffer(&mut self, id: usize, force: bool) {
        let buffer = if id == self.active.id {
            Some(&self.active)
        } else {
            self.parked.get(&id)
        };
        let Some(buffer) = buffer else {
            self.set_message(format!("No buffer: {id}"));
            return;
        };
        if buffer.dirty() && !force {
            self.set_message(format!(
                "Buffer {id} has unsaved changes; use :w or :bdelete!"
            ));
            return;
        }
        if id == self.active.id {
            let next = self.adjacent_buffer(true);
            let replacement = if next == id {
                let buffer = Buffer::open(self.next_buffer_id, None, None, true)
                    .expect("an unnamed empty buffer is valid");
                self.next_buffer_id += 1;
                buffer
            } else {
                self.parked.remove(&next).expect("adjacent buffer exists")
            };
            self.park_source();
            self.active = replacement;
        } else {
            self.parked.remove(&id);
            self.park_source();
        }
        self.set_message(format!(
            "Deleted buffer {id}; active buffer {}",
            self.active.id
        ));
    }

    fn buffer_command(&mut self, name: &str, args: &str) -> bool {
        match name {
            "edit" if args.is_empty() => self.set_message("Usage: :edit path"),
            "edit" => {
                if let Err(error) = self.edit_buffer(PathBuf::from(args), true) {
                    self.set_message(format!("Open failed: {error}"));
                }
            }
            "buffers" | "bnext" | "bprev" if !args.is_empty() => {
                self.set_message(format!("The {name} command takes no arguments"));
            }
            "buffers" => {
                let mut message = String::new();
                for buffer in self.buffers() {
                    if !message.is_empty() {
                        message.push_str(" | ");
                    }
                    use std::fmt::Write as _;
                    write!(
                        message,
                        "{}{}{} {}",
                        buffer.id,
                        if buffer.active { "%" } else { "" },
                        if buffer.dirty { "+" } else { "" },
                        buffer
                            .path
                            .map_or_else(|| Cow::Borrowed("[No Name]"), Path::to_string_lossy,),
                    )
                    .expect("writing into a String cannot fail");
                }
                self.set_message(message);
            }
            "bnext" | "bprev" => self.switch_buffer(self.adjacent_buffer(name == "bnext")),
            "buffer" | "bdelete" | "bdelete!" => {
                let id = if args.is_empty() && name != "buffer" {
                    Some(self.active.id)
                } else if !args.is_empty() && args.bytes().all(|byte| byte.is_ascii_digit()) {
                    args.parse::<usize>().ok().filter(|id| *id > 0)
                } else {
                    None
                };
                match id {
                    Some(id) if name == "buffer" => self.switch_buffer(id),
                    Some(id) => self.delete_buffer(id, name == "bdelete!"),
                    None => self.set_message(format!(
                        "Usage: :{name} {}",
                        if name == "buffer" { "N" } else { "[N]" },
                    )),
                }
            }
            _ => return false,
        }
        true
    }

    fn any_dirty(&self) -> bool {
        self.active.dirty() || self.parked.values().any(Buffer::dirty)
    }

    pub fn execute(&mut self, command: &str) -> Option<Invocation> {
        self.count = None;
        self.clear_leader();
        self.palette = None;
        self.blur_file_picker();
        let command = command.trim().strip_prefix(':').unwrap_or(command.trim());
        let (name, args) = command
            .split_once(char::is_whitespace)
            .unwrap_or((command, ""));
        let args = args.trim();
        // Switching must park directed Visual selections before ordinary Ex cleanup.
        if self.buffer_command(name, args) {
            return None;
        }
        if self.active.mode == Mode::Insert {
            self.finish_insert();
        }
        self.clear_selection();
        self.active.mode = Mode::Normal;
        self.normalize_targets();
        let Some(feature) = self.owner(name) else {
            self.set_message(format!("Unknown command: {name}"));
            return None;
        };
        if !feature.core {
            return Some(Invocation {
                plugin: feature.name.clone(),
                command: name.into(),
                args: args.into(),
            });
        }
        match name {
            "w" | "wq" => {
                if self.save(if args.is_empty() {
                    None
                } else {
                    Some(PathBuf::from(args))
                }) && name == "wq"
                {
                    if self.any_dirty() {
                        self.set_message("Unsaved changes in other buffers; use :w or :q!");
                    } else {
                        self.quit = true;
                    }
                }
            }
            "q" | "q!" if !args.is_empty() => self.set_message("Quit commands take no arguments"),
            "q" if self.any_dirty() => self.set_message("Unsaved changes; use :w or :q!"),
            "q" | "q!" => self.quit = true,
            "plugins" if !args.is_empty() => {
                self.set_message("The plugins command takes no arguments")
            }
            "plugins" => {
                let mut features: Vec<_> = self.features.values().collect();
                features.sort_unstable_by(|left, right| left.name.cmp(&right.name));
                let mut message = format!("Capabilities: {}", self.capabilities.join(", "));
                for feature in features {
                    message.push_str(" | ");
                    message.push_str(&feature.name);
                    if feature.core {
                        message.push_str(" [core]");
                    }
                    message.push_str(": ");
                    for (index, command) in feature.commands.iter().enumerate() {
                        if index > 0 {
                            message.push_str(", ");
                        }
                        message.push_str(command);
                    }
                }
                self.set_message(message);
            }
            _ => unreachable!("privately installed core commands"),
        }
        None
    }

    /// Applies one validated plugin response. Successful text effects collapse
    /// to the primary caret: Insert runs once there, Replace replaces the buffer.
    /// Rejected responses and message-only effects retain the complete set.
    pub fn apply(&mut self, effects: Vec<Effect>) -> Result<(), String> {
        let mut total = 0usize;
        for effect in &effects {
            let text = match effect {
                Effect::Insert(text) | Effect::Replace(text) | Effect::Message(text) => text,
            };
            total = total
                .checked_add(text.len())
                .ok_or("Plugin effects exceed 4 MiB")?;
            if total > MAX_EDIT_BYTES {
                return Err("Plugin effects exceed 4 MiB".into());
            }
            validate_text(text)?;
        }
        // Validation precedes even history/message changes, so a rejected response is atomic.
        let previous_mode = self.active.mode;
        let inserting = self.active.mode == Mode::Insert;
        if inserting {
            self.finish_insert();
        }
        let before = effects
            .iter()
            .any(|effect| {
                matches!(effect, Effect::Insert(text) if !text.is_empty())
                    || matches!(effect, Effect::Replace(_))
            })
            .then(|| self.snapshot());
        if before.is_some() {
            self.count = None;
            self.clear_leader();
            self.clear_selection();
            self.collapse_primary();
            // Plugin inserts use one primary insertion point, not the selection set.
            self.active.mode = Mode::Insert;
        }
        for effect in effects {
            match effect {
                Effect::Insert(text) => self.insert_text(&normalize_newlines(&text)),
                Effect::Replace(text) => {
                    let lines = split_lines(&text);
                    if lines != self.active.lines {
                        self.active.text_changed();
                    }
                    self.active.lines = lines;
                    self.active.search_match = None;
                    self.normalize_targets();
                }
                Effect::Message(text) => self.set_message(text),
            }
        }
        if before.is_some() {
            self.active.mode = if inserting {
                Mode::Insert
            } else {
                Mode::Normal
            };
        }
        self.normalize_targets();
        if let Some(before) = before {
            self.record(before);
        }
        if inserting {
            self.begin_insert();
        }
        if self.active.mode != previous_mode {
            self.refresh_palette();
        }
        Ok(())
    }

    fn save(&mut self, path: Option<PathBuf>) -> bool {
        let Some(path) = path.or_else(|| self.active.path.clone()) else {
            self.set_message("No file name; use :w path");
            return false;
        };
        let identity = match path_identity(&path) {
            Ok(identity) => identity,
            Err(error) => {
                self.set_message(format!("Write failed: {error}"));
                return false;
            }
        };
        if let Some(buffer) = self
            .parked
            .values()
            .find(|buffer| buffer.identity.as_ref() == Some(&identity))
        {
            self.set_message(format!(
                "Write refused: path belongs to buffer {}",
                buffer.id
            ));
            return false;
        }
        match atomic_save(&path, &self.active.lines) {
            Ok(()) => {
                self.active.saved_lines.clone_from(&self.active.lines);
                self.active.save_revision = self.active.save_revision.wrapping_add(1);
                self.active.path = Some(path);
                self.active.identity = Some(identity);
                self.set_message("Written");
                true
            }
            Err(error) => {
                self.set_message(format!("Write failed: {error}"));
                false
            }
        }
    }

    fn snapshot(&self) -> Snapshot {
        Snapshot {
            lines: self.active.lines.clone(),
            targets: self.active.targets.clone(),
            primary: self.active.primary,
        }
    }

    fn record(&mut self, before: Snapshot) {
        if before.lines != self.active.lines {
            self.active.search_match = None;
            self.active.undo.push(before);
            self.active.redo.clear();
        }
    }

    fn record_native(&mut self, before: Snapshot, recipe: EditRecipe) {
        if before.lines != self.active.lines {
            self.last_edit = Some(recipe);
        }
        self.record(before);
    }

    fn target_range(&self, target: Target) -> Selection {
        let start = target.anchor.min(target.active);
        let end = self.next_boundary(target.anchor.max(target.active));
        Selection { start, end }
    }

    fn next_boundary(&self, mut cursor: Cursor) -> Cursor {
        if cursor.column < grapheme_count(&self.active.lines[cursor.row]) {
            cursor.column += 1;
        } else if cursor.row + 1 < self.active.lines.len() {
            cursor.row += 1;
            cursor.column = 0;
        }
        cursor
    }

    fn previous_boundary(&self, mut cursor: Cursor) -> Cursor {
        if cursor.column > 0 {
            cursor.column -= 1;
        } else if cursor.row > 0 {
            cursor.row -= 1;
            cursor.column = grapheme_count(&self.active.lines[cursor.row]);
        }
        cursor
    }

    fn range_target(&self, range: Selection, forward: bool) -> Target {
        let last = if range.start == range.end {
            range.start
        } else {
            self.previous_boundary(range.end)
        };
        Target {
            anchor: if forward { range.start } else { last },
            active: if forward { last } else { range.start },
            preferred_columns: None,
        }
    }

    fn max_column(&self, row: usize) -> usize {
        let count = grapheme_count(&self.active.lines[row]);
        if self.active.mode == Mode::Insert
            || (self.active.mode == Mode::Visual && row + 1 < self.active.lines.len())
        {
            count
        } else {
            count.saturating_sub(1)
        }
    }

    fn normalize_targets(&mut self) {
        for index in 0..self.active.targets.len() {
            let mut target = self.active.targets[index];
            target.active.row = target.active.row.min(self.active.lines.len() - 1);
            target.active.column = target.active.column.min(self.max_column(target.active.row));
            if self.active.mode == Mode::Visual {
                target.anchor.row = target.anchor.row.min(self.active.lines.len() - 1);
                target.anchor.column = target.anchor.column.min(self.max_column(target.anchor.row));
            } else {
                target.anchor = target.active;
            }
            self.active.targets[index] = target;
        }
        let ordered: Vec<_> = self
            .active
            .targets
            .iter()
            .copied()
            .enumerate()
            .map(|(index, target)| {
                let range = if self.active.mode == Mode::Visual {
                    self.target_range(target)
                } else {
                    Selection {
                        start: target.active,
                        end: target.active,
                    }
                };
                (target, index == self.active.primary, range)
            })
            .collect();
        self.merge_target_ranges(ordered, false);
    }

    fn merge_target_ranges(
        &mut self,
        mut ordered: Vec<(Target, bool, Selection)>,
        keep_ranges: bool,
    ) -> Vec<Selection> {
        let count = ordered.len();
        ordered.sort_by_key(|(_, _, range)| (range.start, range.end));
        let mut merged: Vec<(Target, bool, Selection)> = Vec::with_capacity(ordered.len());
        for (target, primary, range) in ordered {
            if let Some((previous, was_primary, previous_range)) = merged.last_mut()
                && ranges_intersect(*previous_range, range)
            {
                let representative = if primary { target } else { *previous };
                previous_range.start = previous_range.start.min(range.start);
                previous_range.end = previous_range.end.max(range.end);
                *previous = if self.active.mode == Mode::Visual
                    && self.target_range(representative) != *previous_range
                {
                    self.range_target(
                        *previous_range,
                        representative.active >= representative.anchor,
                    )
                } else {
                    representative
                };
                *was_primary |= primary;
                continue;
            }
            merged.push((target, primary, range));
        }
        if merged.len() != count {
            self.active.visual_motions = None;
        }
        let ranges = if keep_ranges {
            merged.iter().map(|(_, _, range)| *range).collect()
        } else {
            Vec::new()
        };
        self.active.primary = merged
            .iter()
            .position(|(_, primary, _)| *primary)
            .unwrap_or(0);
        self.active.targets.clear();
        self.active
            .targets
            .extend(merged.into_iter().map(|(target, _, _)| target));
        ranges
    }

    fn collapse_primary(&mut self) {
        let target = self.active.targets[self.active.primary];
        self.active.targets.clear();
        self.active.targets.push(target);
        self.active.primary = 0;
    }

    fn clear_selection(&mut self) {
        if self.active.mode == Mode::Visual {
            self.active.visual_motions = None;
            self.active.mode = Mode::Normal;
            self.normalize_targets();
        }
    }

    fn split_rows(&mut self, end: bool, insert: bool) {
        self.active.visual_motions = None;
        let ranges = self.selections();
        let primary_row = self.cursor().row;
        let mut carets = Vec::new();
        let mut primary = 0;
        for (index, range) in ranges.into_iter().enumerate() {
            let last = if range.end.column == 0 && range.end.row > range.start.row {
                range.end.row - 1
            } else {
                range.end.row
            };
            for row in range.start.row..=last {
                if index == self.active.primary && row == primary_row {
                    primary = carets.len();
                }
                let column = if end {
                    grapheme_count(&self.active.lines[row])
                } else {
                    first_nonblank(&self.active.lines[row])
                };
                carets.push(Target::caret(Cursor { row, column }));
            }
        }
        self.active.targets = carets;
        self.active.primary = primary;
        self.active.mode = if insert { Mode::Insert } else { Mode::Normal };
        self.normalize_targets();
    }

    fn clone_vertical(&mut self, down: bool) {
        self.active.visual_motions = None;
        let count = self.active.targets.len();
        let primary = self.active.primary;
        for index in 0..count {
            let target = self.active.targets[index];
            let shift = |row: usize| {
                if down {
                    row.checked_add(1)
                        .filter(|row| *row < self.active.lines.len())
                } else {
                    row.checked_sub(1)
                }
            };
            let Some(anchor_row) = shift(target.anchor.row) else {
                continue;
            };
            let Some(active_row) = shift(target.active.row) else {
                continue;
            };
            let columns = target.preferred_columns.unwrap_or_else(|| {
                (
                    display_column(&self.active.lines[target.anchor.row], target.anchor.column),
                    display_column(&self.active.lines[target.active.row], target.active.column),
                )
            });
            self.active.targets[index].preferred_columns = Some(columns);
            let cloned = Target {
                anchor: Cursor {
                    row: anchor_row,
                    column: column_at_display(
                        &self.active.lines[anchor_row],
                        columns.0,
                        self.max_column(anchor_row),
                    ),
                },
                active: Cursor {
                    row: active_row,
                    column: column_at_display(
                        &self.active.lines[active_row],
                        columns.1,
                        self.max_column(active_row),
                    ),
                },
                preferred_columns: Some(columns),
            };
            if index == primary {
                self.active.primary = self.active.targets.len();
            }
            self.active.targets.push(cloned);
        }
        self.normalize_targets();
    }

    fn select_occurrences(&mut self, action: Action) {
        let text = self.active.lines.join("\n");
        let offsets = line_offsets(&self.active.lines);
        let ranges = self.selections();
        let primary_range = ranges[self.active.primary];
        let start = cursor_offset(&self.active.lines, &offsets, primary_range.start);
        let end = cursor_offset(&self.active.lines, &offsets, primary_range.end);
        if start == end {
            self.set_message("Nothing selected");
            return;
        }
        let phrase = &text[start..end];
        let mut occupied: Vec<_> = ranges
            .iter()
            .map(|range| {
                (
                    cursor_offset(&self.active.lines, &offsets, range.start),
                    cursor_offset(&self.active.lines, &offsets, range.end),
                )
            })
            .collect();
        // ponytail: literal scan is O(buffer graphemes × phrase bytes); index only for large buffers.
        let candidates: Vec<_> = text
            .grapheme_indices(true)
            .filter_map(|(byte, _)| {
                let end = byte + phrase.len();
                (text[byte..].starts_with(phrase)
                    && GraphemeCursor::new(end, text.len(), true)
                        .is_boundary(&text, 0)
                        .expect("complete buffer supplies grapheme context"))
                .then_some((byte, end))
            })
            .collect();
        if matches!(action, Action::SelectAll) {
            for (start, end) in candidates {
                if occupied
                    .iter()
                    .any(|(left, right)| start < *right && *left < end)
                {
                    continue;
                }
                occupied.push((start, end));
                self.active.targets.push(self.range_target(
                    Selection {
                        start: offset_cursor(&self.active.lines, &offsets, start, true),
                        end: offset_cursor(&self.active.lines, &offsets, end, true),
                    },
                    true,
                ));
            }
        } else {
            let available = |(left, right): &(usize, usize)| {
                !occupied
                    .iter()
                    .any(|(start, end)| *left < *end && *start < *right)
            };
            let next = candidates
                .iter()
                .filter(|range| available(range))
                .find(|(left, _)| *left > start)
                .or_else(|| candidates.iter().find(|range| available(range)));
            let Some(&(start, end)) = next else {
                self.set_message("No more occurrences");
                return;
            };
            let target = self.range_target(
                Selection {
                    start: offset_cursor(&self.active.lines, &offsets, start, true),
                    end: offset_cursor(&self.active.lines, &offsets, end, true),
                },
                true,
            );
            if matches!(action, Action::SkipOccurrence) {
                self.active.targets[self.active.primary] = target;
            } else {
                self.active.primary = self.active.targets.len();
                self.active.targets.push(target);
            }
        }
        self.active.visual_motions = None;
        self.normalize_targets();
        self.message.clear();
    }

    fn edit_selection(&mut self, action: Action) {
        let ranges = self.selections();
        let fragments = self.selection_fragments(&ranges);
        let nonempty = fragments.iter().any(|fragment| !fragment.is_empty());
        if let Err(error) = self.store_clipboard(
            fragments,
            matches!(action, Action::CopySystem) || self.clipboard_mode == ClipboardMode::System,
        ) {
            self.set_message(error);
            return;
        }
        let cut = matches!(action, Action::Cut | Action::Change);
        let changing = matches!(action, Action::Change);
        let recipe = cut.then(|| EditRecipe {
            start: EditStart::Selection {
                change: changing,
                selector: self.selection_intent(&ranges),
            },
            steps: Vec::new(),
        });
        let before = cut.then(|| self.snapshot());
        if changing {
            self.start_insert(before.unwrap(), recipe.unwrap().start);
            self.edit_ranges(action, &ranges);
            self.message.clear();
            return;
        }
        self.edit_ranges(action, &ranges);
        self.active.mode = Mode::Normal;
        self.normalize_targets();
        if let Some(before) = before {
            self.record_native(before, recipe.unwrap());
        }
        self.set_message(if !nonempty {
            "Nothing selected"
        } else if cut {
            "Cut selections"
        } else {
            "Copied selections"
        });
    }

    fn selection_fragments(&self, ranges: &[Selection]) -> Vec<String> {
        let offsets = line_offsets(&self.active.lines);
        ranges
            .iter()
            .map(|range| {
                let start = cursor_offset(&self.active.lines, &offsets, range.start);
                let end = cursor_offset(&self.active.lines, &offsets, range.end);
                let mut fragment = String::with_capacity(end - start);
                for (row, &offset) in offsets
                    .iter()
                    .enumerate()
                    .take(range.end.row + 1)
                    .skip(range.start.row)
                {
                    if row != range.start.row {
                        fragment.push('\n');
                    }
                    let line = &self.active.lines[row];
                    let start = if row == range.start.row {
                        start - offset
                    } else {
                        0
                    };
                    let end = if row == range.end.row {
                        end - offset
                    } else {
                        line.len()
                    };
                    fragment.push_str(&line[start..end]);
                }
                fragment
            })
            .collect()
    }

    fn store_clipboard(&mut self, fragments: Vec<String>, system: bool) -> Result<(), String> {
        if fragments.iter().all(|fragment| fragment.is_empty()) {
            return Ok(());
        }
        if system {
            let exported = fragments.join("\n");
            self.system_clipboard.write(&exported)?;
            self.owned_system_clipboard = Some((exported, fragments));
        } else {
            self.clipboard = fragments;
        }
        Ok(())
    }

    // Range mutation has no register/history side effects: replay publishes only after validation.
    fn edit_ranges(&mut self, action: Action, ranges: &[Selection]) {
        let cut = matches!(action, Action::Cut | Action::Change);
        self.active.visual_motions = None;
        let offsets = line_offsets(&self.active.lines);
        self.active.mode = Mode::Insert;
        if cut {
            let edits = ranges
                .iter()
                .enumerate()
                .map(|(target, range)| Edit {
                    target,
                    start: cursor_offset(&self.active.lines, &offsets, range.start),
                    end: cursor_offset(&self.active.lines, &offsets, range.end),
                    text: Cow::Borrowed(""),
                    caret: 0,
                    round_up: true,
                })
                .collect();
            self.apply_edits(edits);
        } else {
            for (target, range) in self.active.targets.iter_mut().zip(ranges) {
                target.active = range.start;
            }
        }
    }

    fn read_system_clipboard(&mut self) -> Result<Vec<String>, String> {
        let text = self.system_clipboard.read()?;
        validate_paste_text(&text)?;
        if let Some((exported, fragments)) = &self.owned_system_clipboard
            && *exported == text
        {
            return Ok(fragments.clone());
        }
        self.owned_system_clipboard = None;
        Ok(if text.is_empty() {
            Vec::new()
        } else {
            vec![normalize_newlines(&text).into_owned()]
        })
    }

    fn paste_clipboard(&mut self, after: bool, system: bool) {
        let mut fragments = if system {
            match self.read_system_clipboard() {
                Ok(fragments) => fragments,
                Err(error) => {
                    self.set_message(error);
                    return;
                }
            }
        } else {
            std::mem::take(&mut self.clipboard)
        };
        if fragments.is_empty() {
            self.set_message("Clipboard is empty");
        } else if fragments.len() != 1 && fragments.len() != self.active.targets.len() {
            self.set_message("Clipboard fragment count does not match caret count");
        } else {
            let before = self.snapshot();
            self.paste_fragments(after, &fragments);
            if before.lines != self.active.lines {
                self.last_edit = Some(EditRecipe {
                    start: EditStart::Paste {
                        after,
                        fragments: if system {
                            std::mem::take(&mut fragments)
                        } else {
                            fragments.clone()
                        },
                    },
                    steps: Vec::new(),
                });
            }
            self.record(before);
            self.message.clear();
        }
        if !system {
            self.clipboard = fragments;
        }
    }

    fn paste_fragments(&mut self, after: bool, fragments: &[String]) {
        let offsets = line_offsets(&self.active.lines);
        let edits = self
            .active
            .targets
            .iter()
            .enumerate()
            .map(|(target, item)| {
                let mut cursor = item.active;
                if after {
                    cursor.column =
                        (cursor.column + 1).min(grapheme_count(&self.active.lines[cursor.row]));
                }
                let start = cursor_offset(&self.active.lines, &offsets, cursor);
                let text = &fragments[if fragments.len() == 1 { 0 } else { target }];
                Edit {
                    target,
                    start,
                    end: start,
                    text: Cow::Borrowed(text),
                    caret: text.len(),
                    round_up: true,
                }
            })
            .collect();
        self.active.mode = Mode::Insert;
        self.apply_edits(edits);
        self.leave_insert();
    }

    fn begin_insert(&mut self) {
        self.start_insert(self.snapshot(), EditStart::Insert(Action::Insert));
    }

    fn start_insert(&mut self, before: Snapshot, start: EditStart) {
        self.active.insert_start = Some(before);
        self.active.pending_edit = Some(EditRecipe {
            start,
            steps: Vec::new(),
        });
        self.active.visual_motions = None;
        self.active.mode = Mode::Insert;
    }

    fn finish_insert(&mut self) {
        let recipe = self.active.pending_edit.take();
        if let Some(before) = self.active.insert_start.take() {
            if let Some(mut recipe) = recipe {
                while matches!(recipe.steps.last(), Some(InsertStep::Move(_, _))) {
                    recipe.steps.pop();
                }
                self.record_native(before, recipe);
            } else {
                self.record(before);
            }
        }
    }

    fn leave_insert(&mut self) {
        for target in &mut self.active.targets {
            target.active.column = target.active.column.saturating_sub(1);
        }
        self.active.mode = Mode::Normal;
        self.normalize_targets();
    }

    fn place_insert(&mut self, action: Action) {
        self.active.mode = Mode::Insert;
        if matches!(action, Action::OpenBelow | Action::OpenAbove) {
            self.open_lines(matches!(action, Action::OpenBelow));
            return;
        }
        for target in &mut self.active.targets {
            let line = &self.active.lines[target.active.row];
            target.active.column = match action {
                Action::InsertFirstNonblank => first_nonblank(line),
                Action::AppendLineEnd => grapheme_count(line),
                Action::Append => (target.active.column + 1).min(grapheme_count(line)),
                _ => target.active.column,
            };
        }
        self.normalize_targets();
    }

    fn push_insert_step(&mut self, step: InsertStep) {
        if let Some(recipe) = &mut self.active.pending_edit {
            recipe.steps.push(step);
        }
    }

    fn type_native(&mut self, text: &str) {
        self.insert_text(text);
        if let Some(recipe) = &mut self.active.pending_edit {
            if let Some(InsertStep::Typed(typed)) = recipe.steps.last_mut() {
                typed.push_str(text);
            } else {
                recipe.steps.push(InsertStep::Typed(text.to_owned()));
            }
        }
    }

    fn deletion_mask(&self, backwards: bool) -> Vec<bool> {
        let mut mask: Vec<_> = self
            .active
            .targets
            .iter()
            .map(|target| {
                let cursor = target.active;
                if backwards {
                    cursor.row != 0 || cursor.column != 0
                } else {
                    cursor.column < grapheme_count(&self.active.lines[cursor.row])
                        || (self.active.mode == Mode::Insert
                            && cursor.row + 1 < self.active.lines.len())
                }
            })
            .collect();
        if mask.iter().all(|active| *active) {
            mask.truncate(1);
        }
        mask
    }

    fn selection_intent(&mut self, ranges: &[Selection]) -> SelectionIntent {
        if let Some(motions) = self.active.visual_motions.take() {
            return SelectionIntent::Motions(motions);
        }
        let mut spans: Vec<_> = ranges
            .iter()
            .map(|range| {
                let mut cursor = range.start;
                let mut span = 0;
                while cursor < range.end {
                    cursor = self.next_boundary(cursor);
                    span += 1;
                }
                span
            })
            .collect();
        if spans.iter().all(|span| *span == spans[0]) {
            spans.truncate(1);
        }
        SelectionIntent::Spans(spans)
    }

    fn repeat_last_edit(&mut self) {
        let Some(recipe) = self.last_edit.take() else {
            self.set_message("Nothing to repeat");
            return;
        };
        let cardinality = match &recipe.start {
            EditStart::Paste { fragments, .. } => Some(fragments.len()),
            EditStart::Selection {
                selector: SelectionIntent::Spans(spans),
                ..
            } if self.active.mode != Mode::Visual => Some(spans.len()),
            _ => None,
        };
        if cardinality.is_some_and(|count| count != 1 && count != self.active.targets.len()) {
            self.set_message("Repeat fragment/span count does not match target count");
            self.last_edit = Some(recipe);
            return;
        }
        let before = self.snapshot();
        let mode = self.active.mode;
        let selector = self.active.visual_motions.take();
        let search_match = self.active.search_match;
        let result = self
            .replay_edit(&recipe)
            .map_err(str::to_owned)
            .and_then(|fragments| {
                if let Some(fragments) = fragments {
                    self.store_clipboard(fragments, self.clipboard_mode == ClipboardMode::System)?;
                }
                Ok(())
            });
        match result {
            Ok(()) => {
                self.active.visual_motions = None;
                self.record(before);
                self.message.clear();
            }
            Err(error) => {
                self.active.lines = before.lines;
                self.active.targets = before.targets;
                self.active.primary = before.primary;
                self.active.mode = mode;
                self.active.visual_motions = selector;
                self.active.search_match = search_match;
                self.set_message(error);
            }
        }
        self.last_edit = Some(recipe);
    }

    fn replay_edit(&mut self, recipe: &EditRecipe) -> Result<Option<Vec<String>>, &'static str> {
        let mut clipboard = None;
        match &recipe.start {
            EditStart::Insert(action) => self.place_insert(*action),
            EditStart::Selection { change, selector } => {
                let ranges = self.replay_ranges(selector);
                clipboard = Some(self.selection_fragments(&ranges));
                self.edit_ranges(if *change { Action::Change } else { Action::Cut }, &ranges);
                if !*change {
                    self.active.mode = Mode::Normal;
                    self.normalize_targets();
                }
            }
            EditStart::Delete => {
                self.active.mode = Mode::Normal;
                self.delete_forward(&[true]);
            }
            EditStart::Join => {
                self.active.mode = Mode::Normal;
                self.join_lines();
            }
            EditStart::Paste { after, fragments } => self.paste_fragments(*after, fragments),
        }
        for step in &recipe.steps {
            match step {
                InsertStep::Typed(text) => {
                    // Scalar boundaries matter when an insertion merges with its right neighbor.
                    for ch in text.chars() {
                        let mut bytes = [0; 4];
                        self.insert_text(ch.encode_utf8(&mut bytes));
                    }
                }
                InsertStep::Bulk(text) => self.insert_text(text),
                InsertStep::Move(action, count) => self.move_targets(*action, *count),
                InsertStep::Delete(mask) | InsertStep::Backspace(mask) => {
                    // Earlier native steps may have merged carets. Refuse the entire transaction
                    // rather than pairing a recorded partial deletion with different targets.
                    if mask.len() != 1 && mask.len() != self.active.targets.len() {
                        return Err("Repeat deletion count does not match target count");
                    }
                    if matches!(step, InsertStep::Delete(_)) {
                        self.delete_forward(mask);
                    } else {
                        self.backspace(mask);
                    }
                }
            }
        }
        if self.active.mode == Mode::Insert {
            self.leave_insert();
        } else {
            self.active.mode = Mode::Normal;
            self.normalize_targets();
        }
        Ok(clipboard)
    }

    fn replay_ranges(&mut self, selector: &SelectionIntent) -> Vec<Selection> {
        if self.active.mode == Mode::Visual {
            return self.selections();
        }
        self.active.mode = Mode::Visual;
        match selector {
            SelectionIntent::Motions(motions) => {
                for target in &mut self.active.targets {
                    target.anchor = target.active;
                }
                for (action, count) in motions {
                    self.move_targets(*action, *count);
                }
                self.normalize_targets();
                self.selections()
            }
            SelectionIntent::Spans(spans) => {
                let ordered = self
                    .active
                    .targets
                    .iter()
                    .enumerate()
                    .map(|(index, target)| {
                        let start = target.active;
                        let mut end = start;
                        for _ in 0..spans[if spans.len() == 1 { 0 } else { index }] {
                            let next = self.next_boundary(end);
                            if next == end {
                                break;
                            }
                            end = next;
                        }
                        let range = Selection { start, end };
                        (
                            self.range_target(range, true),
                            index == self.active.primary,
                            range,
                        )
                    })
                    .collect();
                self.merge_target_ranges(ordered, true)
            }
        }
    }

    fn paste(&mut self, text: &str) {
        if let Err(error) = validate_paste_text(text) {
            self.set_message(error);
            return;
        }
        // Preserve the separate typing / paste / typing undo groups.
        self.finish_insert();
        let text = normalize_newlines(text);
        if !text.is_empty() {
            let before = self.snapshot();
            self.insert_text(&text);
            self.record_native(
                before,
                EditRecipe {
                    start: EditStart::Insert(Action::Insert),
                    steps: vec![InsertStep::Bulk(text.into_owned())],
                },
            );
        }
        self.begin_insert();
    }

    fn restore(&mut self, snapshot: Snapshot) {
        if self.active.lines != snapshot.lines {
            self.active.text_changed();
        }
        self.active.lines = snapshot.lines;
        self.active.targets = snapshot.targets;
        self.active.primary = snapshot.primary;
        self.active.mode = Mode::Normal;
        self.active.search_match = None;
        self.active.visual_motions = None;
        self.normalize_targets();
    }

    fn undo(&mut self) {
        if let Some(before) = self.active.undo.pop() {
            self.active.redo.push(self.snapshot());
            self.restore(before);
        } else {
            self.set_message("Nothing to undo");
        }
    }

    fn redo(&mut self) {
        if let Some(after) = self.active.redo.pop() {
            self.active.undo.push(self.snapshot());
            self.restore(after);
        } else {
            self.set_message("Nothing to redo");
        }
    }

    fn move_targets(&mut self, action: Action, count: usize) {
        for index in 0..self.active.targets.len() {
            let mut cursor = self.active.targets[index].active;
            match action {
                Action::Left => cursor.column = cursor.column.saturating_sub(count),
                Action::Right => {
                    cursor.column = cursor
                        .column
                        .saturating_add(count)
                        .min(self.max_column(cursor.row))
                }
                Action::Down | Action::Up => {
                    let row = if matches!(action, Action::Down) {
                        cursor
                            .row
                            .saturating_add(count)
                            .min(self.active.lines.len() - 1)
                    } else {
                        cursor.row.saturating_sub(count)
                    };
                    let first = cursor.row.min(row);
                    let last = cursor.row.max(row);
                    cursor.column = (first..=last)
                        .map(|row| self.max_column(row))
                        .min()
                        .unwrap_or(0)
                        .min(cursor.column);
                    cursor.row = row;
                }
                Action::LineStart => cursor.column = 0,
                Action::LineEnd => cursor.column = self.max_column(cursor.row),
                _ => cursor = self.word_destination(cursor, action, count),
            }
            self.active.targets[index].active = cursor;
            self.active.targets[index].preferred_columns = None;
        }
        self.normalize_targets();
    }
    fn word_destination(&self, cursor: Cursor, action: Action, count: usize) -> Cursor {
        let row = cursor.row;
        let byte = grapheme_byte(&self.active.lines[row], cursor.column);
        let big = matches!(
            action,
            Action::BigWordNext | Action::BigWordPrevious | Action::BigWordEnd
        );
        let destination = match action {
            Action::WordPrevious | Action::BigWordPrevious => {
                let mut tokens = word_tokens(&self.active.lines[..=row], big)
                    .rev()
                    .skip_while(|(r, b, _)| (*r, *b) >= (row, byte))
                    .peekable();
                let mut destination = (0, 0);
                for _ in 0..count {
                    let Some(mut first) = tokens.find(|(_, _, kind)| *kind != WordKind::Whitespace)
                    else {
                        destination = (0, 0);
                        break;
                    };
                    if first.2 != WordKind::EmptyLine {
                        while tokens.peek().is_some_and(|(_, _, kind)| *kind == first.2) {
                            first = tokens.next().expect("peeked token");
                        }
                    }
                    destination = (first.0, first.1);
                }
                destination
            }
            _ => {
                let mut tokens = word_tokens(&self.active.lines[row..], big)
                    .skip_while(|(r, b, _)| (*r, *b) < (0, byte))
                    .peekable();
                let mut current = tokens
                    .next()
                    .expect("cursor has a grapheme or line-end token")
                    .2;
                let last = self.active.lines.len() - 1;
                let mut destination = (last, self.active.lines[last].len());
                for _ in 0..count {
                    let next_start = matches!(action, Action::WordNext | Action::BigWordNext);
                    if next_start && current != WordKind::EmptyLine {
                        while tokens.peek().is_some_and(|(_, _, kind)| *kind == current) {
                            tokens.next();
                        }
                    }
                    let Some(mut first) = tokens.find(|(_, _, kind)| {
                        *kind != WordKind::Whitespace
                            && (next_start || *kind != WordKind::EmptyLine)
                    }) else {
                        destination = (last, self.active.lines[last].len());
                        break;
                    };
                    current = first.2;
                    if !next_start {
                        while tokens.peek().is_some_and(|(_, _, kind)| *kind == current) {
                            first = tokens.next().expect("peeked token");
                        }
                    }
                    destination = (row + first.0, first.1);
                }
                destination
            }
        };
        let line = &self.active.lines[destination.0];
        let column = column_after_byte(line, destination.1);
        Cursor {
            row: destination.0,
            column: if destination.1 == line.len() && self.active.mode != Mode::Insert {
                column.saturating_sub(1)
            } else {
                column
            },
        }
    }

    /// Every edit in a batch refers to this one pre-edit buffer. Duplicate row
    /// operations share an edit; caret destinations are remapped only afterwards.
    // ponytail: rebuilding text costs O(buffer + carets²); use per-line edits for large buffers.
    fn apply_edits(&mut self, mut edits: Vec<Edit<'_>>) {
        if edits.is_empty() {
            return;
        }
        edits.sort_by_key(|edit| (edit.start, edit.end));
        let mut unique: Vec<usize> = Vec::with_capacity(edits.len());
        for (index, edit) in edits.iter().enumerate() {
            if unique.last().is_some_and(|previous| {
                let previous = &edits[*previous];
                previous.start == edit.start
                    && previous.end == edit.end
                    && previous.text == edit.text
            }) {
                continue;
            }
            unique.push(index);
        }
        let old = self.active.lines.join("\n");
        let offsets = line_offsets(&self.active.lines);
        let removed: usize = unique
            .iter()
            .map(|index| edits[*index].end - edits[*index].start)
            .sum();
        let added: usize = unique.iter().map(|index| edits[*index].text.len()).sum();
        let mut text = String::with_capacity(old.len() - removed + added);
        let mut consumed = 0;
        for index in &unique {
            let edit = &edits[*index];
            assert!(edit.start >= consumed, "batch edits must not overlap");
            text.push_str(&old[consumed..edit.start]);
            text.push_str(&edit.text);
            consumed = edit.end;
        }
        text.push_str(&old[consumed..]);
        let remap = |position: usize, after: bool| {
            let mut removed = 0;
            let mut added = 0;
            for index in &unique {
                let edit = &edits[*index];
                if position < edit.start {
                    break;
                }
                if position == edit.start || position < edit.end {
                    return edit.start - removed + added + if after { edit.text.len() } else { 0 };
                }
                removed += edit.end - edit.start;
                added += edit.text.len();
            }
            position - removed + added
        };
        let mut destinations: Vec<_> = self
            .active
            .targets
            .iter()
            .map(|target| {
                (
                    remap(
                        cursor_offset(&self.active.lines, &offsets, target.active),
                        true,
                    ),
                    true,
                )
            })
            .collect();
        for edit in &edits {
            destinations[edit.target] = (remap(edit.start, false) + edit.caret, edit.round_up);
        }
        if text != old {
            self.active.text_changed();
            self.active.search_match = None;
        }
        self.active.lines = text.split('\n').map(str::to_owned).collect();
        let offsets = line_offsets(&self.active.lines);
        for (target, (byte, round_up)) in self.active.targets.iter_mut().zip(destinations) {
            target.active = offset_cursor(&self.active.lines, &offsets, byte, round_up);
            target.anchor = target.active;
            target.preferred_columns = None;
        }
        self.normalize_targets();
    }

    fn insert_text(&mut self, text: &str) {
        if text.is_empty() {
            return;
        }
        let offsets = line_offsets(&self.active.lines);
        let edits = self
            .active
            .targets
            .iter()
            .enumerate()
            .map(|(target, item)| {
                let start = cursor_offset(&self.active.lines, &offsets, item.active);
                Edit {
                    target,
                    start,
                    end: start,
                    text: Cow::Borrowed(text),
                    caret: text.len(),
                    round_up: true,
                }
            })
            .collect();
        self.apply_edits(edits);
    }

    fn open_lines(&mut self, below: bool) {
        let offsets = line_offsets(&self.active.lines);
        let edits = self
            .active
            .targets
            .iter()
            .enumerate()
            .map(|(target, item)| {
                let start = offsets[item.active.row]
                    + if below {
                        self.active.lines[item.active.row].len()
                    } else {
                        0
                    };
                Edit {
                    target,
                    start,
                    end: start,
                    text: Cow::Borrowed("\n"),
                    caret: usize::from(below),
                    round_up: true,
                }
            })
            .collect();
        self.apply_edits(edits);
    }

    fn delete_forward(&mut self, mask: &[bool]) {
        let offsets = line_offsets(&self.active.lines);
        let edits = self
            .active
            .targets
            .iter()
            .enumerate()
            .filter_map(|(target, item)| {
                if !mask[if mask.len() == 1 { 0 } else { target }] {
                    return None;
                }
                let cursor = item.active;
                let start = cursor_offset(&self.active.lines, &offsets, cursor);
                let end = if cursor.column < grapheme_count(&self.active.lines[cursor.row]) {
                    cursor_offset(&self.active.lines, &offsets, self.next_boundary(cursor))
                } else if self.active.mode == Mode::Insert
                    && cursor.row + 1 < self.active.lines.len()
                {
                    start + 1
                } else {
                    return None;
                };
                Some(Edit {
                    target,
                    start,
                    end,
                    text: Cow::Borrowed(""),
                    caret: 0,
                    round_up: true,
                })
            })
            .collect();
        self.apply_edits(edits);
    }

    fn join_lines(&mut self) {
        let offsets = line_offsets(&self.active.lines);
        let edits = self
            .active
            .targets
            .iter()
            .enumerate()
            .filter_map(|(target, item)| {
                let row = item.active.row;
                let line = &self.active.lines[row];
                let next = self.active.lines.get(row + 1)?;
                let trimmed = next.trim_start_matches([' ', '\t']);
                let separator = if !line.is_empty()
                    && !trimmed.is_empty()
                    && !line.ends_with([' ', '\t'])
                    && !trimmed.starts_with(')')
                {
                    if line.ends_with(['.', '?', '!']) {
                        "  "
                    } else {
                        " "
                    }
                } else {
                    ""
                };
                let start = offsets[row] + line.len();
                Some(Edit {
                    target,
                    start,
                    end: start + 1 + next.len() - trimmed.len(),
                    text: Cow::Borrowed(separator),
                    caret: 0,
                    round_up: false,
                })
            })
            .collect();
        self.apply_edits(edits);
    }

    fn backspace(&mut self, mask: &[bool]) {
        let offsets = line_offsets(&self.active.lines);
        let edits = self
            .active
            .targets
            .iter()
            .enumerate()
            .filter_map(|(target, item)| {
                if !mask[if mask.len() == 1 { 0 } else { target }] {
                    return None;
                }
                let cursor = item.active;
                if cursor.column == 0 && cursor.row == 0 {
                    return None;
                }
                let start =
                    cursor_offset(&self.active.lines, &offsets, self.previous_boundary(cursor));
                let end = cursor_offset(&self.active.lines, &offsets, cursor);
                Some(Edit {
                    target,
                    start,
                    end,
                    text: Cow::Borrowed(""),
                    caret: 0,
                    round_up: true,
                })
            })
            .collect();
        self.apply_edits(edits);
    }
}

fn ranges_intersect(left: Selection, right: Selection) -> bool {
    if left.start == left.end {
        left.start == right.start || (right.start < left.start && left.start < right.end)
    } else if right.start == right.end {
        left.start <= right.start && right.start < left.end
    } else {
        left.start < right.end && right.start < left.end
    }
}

fn first_nonblank(line: &str) -> usize {
    line.graphemes(true)
        .take_while(|grapheme| matches!(*grapheme, " " | "\t"))
        .count()
}

fn display_column(line: &str, column: usize) -> usize {
    line.graphemes(true)
        .take(column)
        .fold(0, |cells, grapheme| {
            cells
                + if grapheme == "\t" {
                    4 - cells % 4
                } else {
                    grapheme.width()
                }
        })
}

fn column_at_display(line: &str, wanted: usize, maximum: usize) -> usize {
    let mut cells = 0;
    let mut count = 0;
    for (column, grapheme) in line.graphemes(true).enumerate() {
        let width = if grapheme == "\t" {
            4 - cells % 4
        } else {
            grapheme.width()
        };
        if cells + width > wanted {
            return column.min(maximum);
        }
        cells += width;
        count = column + 1;
    }
    count.min(maximum)
}

fn line_offsets(lines: &[String]) -> Vec<usize> {
    let mut byte = 0;
    lines
        .iter()
        .map(|line| {
            let start = byte;
            byte += line.len() + 1;
            start
        })
        .collect()
}

fn cursor_offset(lines: &[String], offsets: &[usize], cursor: Cursor) -> usize {
    offsets[cursor.row] + grapheme_byte(&lines[cursor.row], cursor.column)
}

fn offset_cursor(lines: &[String], offsets: &[usize], byte: usize, round_up: bool) -> Cursor {
    let row = offsets
        .partition_point(|offset| *offset <= byte)
        .saturating_sub(1);
    let local = (byte - offsets[row]).min(lines[row].len());
    let column = if round_up {
        column_after_byte(&lines[row], local)
    } else {
        lines[row]
            .grapheme_indices(true)
            .take_while(|(byte, _)| *byte <= local)
            .count()
            .saturating_sub(1)
    };
    Cursor { row, column }
}

#[derive(Clone, Copy, Eq, PartialEq)]
enum WordKind {
    Whitespace,
    Keyword,
    Punctuation,
    EmptyLine,
}

fn word_tokens(
    lines: &[String],
    big: bool,
) -> impl DoubleEndedIterator<Item = (usize, usize, WordKind)> + '_ {
    lines.iter().enumerate().flat_map(move |(row, line)| {
        line.grapheme_indices(true)
            .map(move |(byte, grapheme)| {
                let ch = grapheme.chars().next().expect("graphemes are nonempty");
                let kind = if ch.is_whitespace() {
                    WordKind::Whitespace
                } else if big || ch == '_' || ch.is_alphanumeric() {
                    WordKind::Keyword
                } else {
                    WordKind::Punctuation
                };
                (row, byte, kind)
            })
            .chain(std::iter::once((
                row,
                line.len(),
                if line.is_empty() {
                    WordKind::EmptyLine
                } else {
                    WordKind::Whitespace
                },
            )))
    })
}

fn valid_command(command: &str) -> bool {
    let command = command.strip_suffix('!').unwrap_or(command);
    let mut chars = command.chars();
    chars.next().is_some_and(|ch| ch.is_ascii_alphabetic())
        && chars.all(|ch| ch.is_ascii_alphanumeric() || ch == '_' || ch == '-')
}

fn validate_paste_text(text: &str) -> Result<(), String> {
    if text.len() > MAX_EDIT_BYTES {
        Err("Paste exceeds 4 MiB".into())
    } else {
        validate_text(text)
    }
}

fn validate_text(text: &str) -> Result<(), String> {
    if let Some(ch) = text
        .chars()
        .find(|ch| ch.is_control() && !matches!(ch, '\t' | '\n' | '\r'))
    {
        Err(format!("Unsupported control character U+{:04X}", ch as u32))
    } else {
        Ok(())
    }
}

fn normalize_newlines(text: &str) -> Cow<'_, str> {
    if !text.contains('\r') {
        return Cow::Borrowed(text);
    }
    let mut normalized = String::with_capacity(text.len());
    let mut chars = text.chars().peekable();
    while let Some(ch) = chars.next() {
        if ch == '\r' {
            if chars.peek() == Some(&'\n') {
                chars.next();
            }
            normalized.push('\n');
        } else {
            normalized.push(ch);
        }
    }
    Cow::Owned(normalized)
}

fn split_lines(text: &str) -> Vec<String> {
    normalize_newlines(text)
        .split('\n')
        .map(str::to_owned)
        .collect()
}

fn grapheme_count(line: &str) -> usize {
    line.graphemes(true).count()
}
fn grapheme_byte(line: &str, column: usize) -> usize {
    line.grapheme_indices(true)
        .nth(column)
        .map_or(line.len(), |(byte, _)| byte)
}
fn column_after_byte(line: &str, byte: usize) -> usize {
    line.grapheme_indices(true)
        .take_while(|(index, _)| *index < byte)
        .count()
}

fn path_identity(path: &Path) -> io::Result<PathBuf> {
    let absolute = if path.is_absolute() {
        path.to_owned()
    } else {
        std::env::current_dir()?.join(path)
    };
    // Resolve the existing prefix too, so new files under aliased directories deduplicate.
    for ancestor in absolute.ancestors() {
        match fs::canonicalize(ancestor) {
            Ok(prefix) => {
                let mut identity = prefix;
                for component in absolute
                    .strip_prefix(ancestor)
                    .expect("path ancestor")
                    .components()
                {
                    match component {
                        Component::ParentDir => {
                            identity.pop();
                        }
                        Component::CurDir => {}
                        component => identity.push(component.as_os_str()),
                    }
                }
                return Ok(identity);
            }
            Err(error) if error.kind() == io::ErrorKind::NotFound => {}
            Err(error) => return Err(error),
        }
    }
    Err(io::Error::new(
        io::ErrorKind::NotFound,
        "No existing path ancestor",
    ))
}

fn target_metadata(path: &Path) -> io::Result<Option<fs::Metadata>> {
    match fs::symlink_metadata(path) {
        Ok(metadata) if metadata.file_type().is_symlink() => Err(io::Error::new(
            io::ErrorKind::InvalidInput,
            "Refusing to save through a symbolic link",
        )),
        Ok(metadata) if !metadata.is_file() => Err(io::Error::new(
            io::ErrorKind::InvalidInput,
            "Save target is not a regular file",
        )),
        Ok(metadata) => Ok(Some(metadata)),
        Err(error) if error.kind() == io::ErrorKind::NotFound => Ok(None),
        Err(error) => Err(error),
    }
}

fn atomic_save(path: &Path, lines: &[String]) -> io::Result<()> {
    let metadata = target_metadata(path)?;
    let parent = path
        .parent()
        .filter(|parent| !parent.as_os_str().is_empty())
        .unwrap_or(Path::new("."));
    let (temporary, mut file) = loop {
        let id = TEMP_ID.fetch_add(1, Ordering::Relaxed);
        let temporary = parent.join(format!(".vamp-{}-{id}.tmp", std::process::id()));
        let mut options = OpenOptions::new();
        options.write(true).create_new(true);
        #[cfg(unix)]
        options.mode(0o600);
        match options.open(&temporary) {
            Ok(file) => break (temporary, file),
            Err(error) if error.kind() == io::ErrorKind::AlreadyExists => continue,
            Err(error) => return Err(error),
        }
    };
    let result = (|| {
        for (index, line) in lines.iter().enumerate() {
            if index > 0 {
                file.write_all(b"\n")?;
            }
            file.write_all(line.as_bytes())?;
        }
        if let Some(metadata) = metadata {
            file.set_permissions(metadata.permissions())?;
        }
        file.sync_all()?;
        drop(file);
        // Recheck immediately before rename: never knowingly replace a symlink.
        target_metadata(path)?;
        fs::rename(&temporary, path)?;
        #[cfg(unix)]
        fs::File::open(parent)?.sync_all()?;
        Ok(())
    })();
    if result.is_err() {
        let _ = fs::remove_file(&temporary);
    }
    result
}

#[cfg(test)]
mod tests {
    use super::*;

    struct Directory(PathBuf);
    impl Directory {
        fn new() -> Self {
            let id = TEMP_ID.fetch_add(1, Ordering::Relaxed);
            let path =
                std::env::temp_dir().join(format!("vamp-editor-test-{}-{id}", std::process::id()));
            fs::create_dir(&path).unwrap();
            Self(path)
        }
        fn path(&self, name: &str) -> PathBuf {
            self.0.join(name)
        }
    }
    impl Drop for Directory {
        fn drop(&mut self) {
            let _ = fs::remove_dir_all(&self.0);
        }
    }
    fn editor() -> Editor {
        let mut editor = Editor::open(None, vec!["text".into()]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor
    }
    fn type_text(editor: &mut Editor, text: &str) {
        for ch in text.chars() {
            editor.handle(if ch == '\n' {
                Input::Enter
            } else {
                Input::Char(ch)
            });
        }
    }
    fn project_editor(directory: &Directory) -> Editor {
        let mut editor = editor();
        editor.project_root = directory.0.clone();
        editor
    }

    #[cfg(unix)]
    mod system_clipboard {
        use super::*;
        use std::os::unix::fs::PermissionsExt;

        struct Fixture(Directory);

        impl Fixture {
            fn new() -> Self {
                let fixture = Self(Directory::new());
                for name in ["state", "reads", "writes"] {
                    fs::write(fixture.0.path(name), b"").unwrap();
                }
                let quoted = |name: &str| {
                    format!(
                        "'{}'",
                        fixture
                            .0
                            .path(name)
                            .display()
                            .to_string()
                            .replace('\'', "'\\''")
                    )
                };
                let reader = format!(
                    "#!/bin/sh\nprintf . >> {}\n[ ! -f {} ] || exit 23\nexec /bin/cat {}\n",
                    quoted("reads"),
                    quoted("fail-read"),
                    quoted("state"),
                );
                let writer = format!(
                    "#!/bin/sh\nprintf . >> {}\n[ ! -f {} ] || exit 23\n/bin/cat > {} || exit 24\nexec /bin/mv {} {}\n",
                    quoted("writes"),
                    quoted("fail-write"),
                    quoted("next"),
                    quoted("next"),
                    quoted("state"),
                );
                for (name, script) in [("reader", reader), ("writer", writer)] {
                    let path = fixture.0.path(name);
                    fs::write(&path, script).unwrap();
                    fs::set_permissions(path, fs::Permissions::from_mode(0o700)).unwrap();
                }
                fixture
            }

            fn editor(&self) -> Editor {
                let mut editor = Editor::open(None, vec!["text".into()]).unwrap();
                editor.set_system_clipboard(SystemClipboard::with_commands(
                    self.0.path("reader"),
                    self.0.path("writer"),
                ));
                editor
            }

            fn bytes(&self, name: &str) -> Vec<u8> {
                fs::read(self.0.path(name)).unwrap()
            }

            fn external(&self, text: impl AsRef<[u8]>) {
                fs::write(self.0.path("state"), text).unwrap();
            }

            fn fail(&self, name: &str, enabled: bool) {
                let path = self.0.path(name);
                if enabled {
                    fs::write(path, b"").unwrap();
                } else {
                    fs::remove_file(path).unwrap();
                }
            }
        }

        // Includes every replay-owned state, not the intentionally changed error message.
        fn state(editor: &Editor) -> String {
            format!(
                "{:?}",
                (
                    (
                        &editor.active.lines,
                        &editor.active.targets,
                        editor.active.primary,
                        editor.active.mode,
                        &editor.active.search_query,
                        editor.active.search_match,
                        &editor.active.undo,
                        &editor.active.redo,
                    ),
                    (
                        &editor.active.insert_start,
                        &editor.active.pending_edit,
                        &editor.active.visual_motions,
                        &editor.clipboard,
                        &editor.owned_system_clipboard,
                        &editor.last_edit,
                        editor.clipboard_mode,
                    ),
                ),
            )
        }

        #[test]
        fn default_system_native_copy_cut_change_exports_exact_selected_text() {
            for key in ['y', 'd', 'x', 'c'] {
                let fixture = Fixture::new();
                let mut editor = fixture.editor();
                assert_eq!(editor.clipboard_mode(), ClipboardMode::System);
                editor.clipboard = vec!["internal".into()];
                editor
                    .apply(vec![Effect::Replace("a界e\u{301}z\n👩‍🚀tail\n".into())])
                    .unwrap();
                set_ranges(
                    &mut editor,
                    &[(Cursor { row: 0, column: 1 }, Cursor { row: 1, column: 1 })],
                    0,
                );
                let undo = editor.active.undo.len();
                editor.handle(Input::Char(key));
                assert_eq!(fixture.bytes("state"), "界e\u{301}z\n👩‍🚀".as_bytes());
                assert_eq!(fixture.bytes("writes").len(), 1);
                assert_eq!(fixture.bytes("reads").len(), 0);
                assert_eq!(editor.clipboard, ["internal"]);
                match key {
                    'y' => {
                        assert_eq!(editor.context().text, "a界e\u{301}z\n👩‍🚀tail\n");
                        assert_eq!(editor.active.undo.len(), undo);
                    }
                    'c' => {
                        assert_eq!(editor.mode(), Mode::Insert);
                        assert!(editor.active.pending_edit.is_some());
                        type_text(&mut editor, "Q");
                        editor.handle(Input::Escape);
                        assert_eq!(editor.context().text, "aQtail\n");
                        editor.handle(Input::Char('u'));
                        assert_eq!(editor.context().text, "a界e\u{301}z\n👩‍🚀tail\n");
                    }
                    _ => {
                        assert_eq!(editor.context().text, "atail\n");
                        assert_eq!(editor.active.undo.len(), undo + 1);
                        editor.handle(Input::Char('u'));
                        assert_eq!(editor.context().text, "a界e\u{301}z\n👩‍🚀tail\n");
                    }
                }
            }
        }

        #[test]
        fn system_paste_before_after_normalizes_valid_external_text_and_records_it() {
            for (key, action, expected) in [
                ('P', None, "界\t\n:q!\nab"),
                ('p', None, "a界\t\n:q!\nb"),
                ('z', Some("core.paste_system_before"), "界\t\n:q!\nab"),
                ('z', Some("core.paste_system_after"), "a界\t\n:q!\nb"),
            ] {
                let fixture = Fixture::new();
                let mut editor = fixture.editor();
                if let Some(action) = action {
                    editor.set_clipboard_mode("separate").unwrap();
                    editor.bind("normal", "z", Some(action.into())).unwrap();
                }
                editor.apply(vec![Effect::Replace("ab".into())]).unwrap();
                editor.clipboard = vec!["stale".into()];
                fixture.external("界\t\r\n:q!\r");
                editor.handle(Input::Char(key));
                assert_eq!(editor.context().text, expected);
                assert_eq!(editor.mode(), Mode::Normal);
                assert_eq!(editor.clipboard, ["stale"]);
                assert_eq!(fixture.bytes("state"), "界\t\r\n:q!\r".as_bytes());
                assert_eq!(fixture.bytes("writes").len(), 0);
                editor.handle(Input::Char('u'));
                assert_eq!(editor.context().text, "ab");
                assert!(!editor.should_quit());
            }
        }

        #[test]
        fn own_fragments_pair_external_multiline_broadcasts_and_empty_never_uses_internal() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor
                .apply(vec![Effect::Replace("ab\nxyz".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            type_text(&mut editor, "vey");
            assert_eq!(fixture.bytes("state"), b"ab\nxyz");
            assert_eq!(
                editor.owned_system_clipboard.as_ref().unwrap().1,
                ["ab", "xyz"]
            );
            editor
                .apply(vec![Effect::Replace("1\n2\n3".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 2);
            let before = state(&editor);
            editor.handle(Input::Char('P'));
            assert_eq!(state(&editor), before);
            assert!(editor.message().contains("fragment count"));
            editor.apply(vec![Effect::Replace("1\n2".into())]).unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            editor.handle(Input::Char('P'));
            assert_eq!(editor.context().text, "ab1\nxyz2");
            editor.apply(vec![Effect::Replace("1\n2".into())]).unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            fixture.external("left\nright\n");
            editor.handle(Input::Char('P'));
            assert_eq!(editor.context().text, "left\nright\n1\nleft\nright\n2");
            assert!(editor.owned_system_clipboard.is_none());
            editor.apply(vec![Effect::Replace("1\n2".into())]).unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            fixture.external("ab\nxyz");
            editor.handle(Input::Char('P'));
            assert_eq!(editor.context().text, "ab\nxyz1\nab\nxyz2");
            editor.clipboard = vec!["stale".into()];
            fixture.external("");
            let before = state(&editor);
            editor.handle(Input::Char('p'));
            assert_eq!(state(&editor), before);
            assert!(editor.message().contains("empty"));
        }

        #[test]
        fn separate_and_explicit_system_actions_are_independent_and_mode_checked() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor.set_clipboard_mode("SePaRaTe").unwrap();
            assert_eq!(editor.clipboard_mode(), ClipboardMode::Separate);
            for mode in ["", "invalid", " system "] {
                assert!(editor.set_clipboard_mode(mode).is_err());
                assert_eq!(editor.clipboard_mode(), ClipboardMode::Separate);
            }
            fixture.external("outside");
            fixture.fail("fail-read", true);
            fixture.fail("fail-write", true);
            editor
                .apply(vec![Effect::Replace("inside".into())])
                .unwrap();
            type_text(&mut editor, "veyP");
            assert_eq!(editor.context().text, "insideinside");
            assert_eq!(editor.clipboard, ["inside"]);
            assert_eq!(fixture.bytes("reads").len(), 0);
            assert_eq!(fixture.bytes("writes").len(), 0);
            fixture.fail("fail-read", false);
            fixture.fail("fail-write", false);
            for action in ["core.paste_system_before", "core.paste_system_after"] {
                assert!(editor.bind("visual", "z", Some(action.into())).is_err());
                assert!(editor.bind("insert", "z", Some(action.into())).is_err());
                editor.bind("normal", "z", Some(action.into())).unwrap();
            }
            assert!(
                editor
                    .bind("normal", "q", Some("core.copy_system".into()))
                    .is_err()
            );
            assert!(
                editor
                    .bind("insert", "q", Some("core.copy_system".into()))
                    .is_err()
            );
            editor
                .bind("visual", "q", Some("core.copy_system".into()))
                .unwrap();
            editor
                .apply(vec![Effect::Replace("system".into())])
                .unwrap();
            editor.handle(Input::Home);
            type_text(&mut editor, "veq");
            assert_eq!(fixture.bytes("state"), b"system");
            assert_eq!(editor.clipboard, ["inside"]);
            editor.apply(vec![Effect::Replace("!".into())]).unwrap();
            editor.handle(Input::Char('z'));
            assert_eq!(editor.context().text, "!system");
            assert_eq!(editor.clipboard, ["inside"]);
            editor.handle(Input::Char('P'));
            assert_eq!(editor.context().text, "!systeinsidem");
            assert_eq!(fixture.bytes("state"), b"system");
            editor.set_clipboard_mode("SYSTEM").unwrap();
            editor.handle(Input::Ctrl('p'));
            let entries = &editor.palette().unwrap().entries;
            for name in [
                "core.copy_system",
                "core.paste_system_before",
                "core.paste_system_after",
            ] {
                let entry = entries.iter().find(|entry| entry.name == name).unwrap();
                assert_eq!(entry.enabled, name != "core.copy_system");
            }
        }

        #[test]
        fn provider_and_invalid_text_errors_preserve_all_editing_state() {
            for key in ['y', 'd', 'x', 'c'] {
                let fixture = Fixture::new();
                let mut editor = fixture.editor();
                editor
                    .apply(vec![Effect::Replace("ab\ncd".into())])
                    .unwrap();
                type_text(&mut editor, "iX");
                editor.handle(Input::Escape);
                editor.handle(Input::Char('u'));
                editor.clipboard = vec!["internal".into()];
                editor.store_clipboard(vec!["owned".into()], true).unwrap();
                set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
                type_text(&mut editor, "ve");
                fixture.fail("fail-write", true);
                let before = state(&editor);
                editor.handle(Input::Char(key));
                assert_eq!(state(&editor), before);
                assert_eq!(fixture.bytes("state"), b"owned");
                assert!(!editor.message().is_empty());
            }
            for invalid in [
                b"valid\nbad\0".to_vec(),
                b"\x1b[31m".to_vec(),
                b"\xff".to_vec(),
                vec![b'x'; MAX_EDIT_BYTES + 1],
            ] {
                let fixture = Fixture::new();
                let mut editor = fixture.editor();
                editor
                    .apply(vec![Effect::Replace("original".into())])
                    .unwrap();
                editor.store_clipboard(vec!["owned".into()], true).unwrap();
                editor.clipboard = vec!["internal".into()];
                fixture.external(invalid);
                let before = state(&editor);
                editor.handle(Input::Char('p'));
                assert_eq!(state(&editor), before);
                assert!(!editor.message().is_empty());
            }
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            type_text(&mut editor, "iX");
            editor.handle(Input::Escape);
            fixture.fail("fail-read", true);
            let before = state(&editor);
            editor.handle(Input::Char('P'));
            assert_eq!(state(&editor), before);
            assert!(!editor.message().is_empty());
        }

        #[test]
        fn separate_cut_change_and_copy_never_invoke_system_transport() {
            for key in ['y', 'd', 'x', 'c'] {
                let fixture = Fixture::new();
                let mut editor = fixture.editor();
                editor.set_clipboard_mode("separate").unwrap();
                fixture.external("outside");
                fixture.fail("fail-read", true);
                fixture.fail("fail-write", true);
                editor
                    .apply(vec![Effect::Replace("inside".into())])
                    .unwrap();
                type_text(&mut editor, "ve");
                editor.handle(Input::Char(key));
                assert_eq!(editor.clipboard, ["inside"]);
                assert_eq!(
                    editor.context().text,
                    if key == 'y' { "inside" } else { "" }
                );
                assert_eq!(
                    editor.mode(),
                    if key == 'c' {
                        Mode::Insert
                    } else {
                        Mode::Normal
                    }
                );
                assert_eq!(fixture.bytes("state"), b"outside");
                assert_eq!(fixture.bytes("reads").len(), 0);
                assert_eq!(fixture.bytes("writes").len(), 0);
            }
        }

        #[test]
        fn empty_visual_copy_and_change_preserve_both_registers() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor.clipboard = vec!["internal".into()];
            editor.store_clipboard(vec!["owned".into()], true).unwrap();
            fixture.fail("fail-write", true);
            for key in ['y', 'd', 'c'] {
                editor.active.mode = Mode::Visual;
                editor.handle(Input::Char(key));
                assert_eq!(editor.clipboard, ["internal"]);
                assert_eq!(fixture.bytes("state"), b"owned");
                assert_eq!(fixture.bytes("writes").len(), 1);
                assert_eq!(editor.context().text, "");
                if key == 'c' {
                    assert_eq!(editor.mode(), Mode::Insert);
                    type_text(&mut editor, "X");
                    editor.handle(Input::Escape);
                    editor.handle(Input::Char('u'));
                    assert_eq!(editor.context().text, "");
                }
            }
        }

        #[test]
        fn registers_and_mode_are_session_wide_across_buffers() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor.set_clipboard_mode("separate").unwrap();
            editor
                .apply(vec![Effect::Replace("inside".into())])
                .unwrap();
            type_text(&mut editor, "vey");
            editor.set_clipboard_mode("system").unwrap();
            editor
                .apply(vec![Effect::Replace("ab\nxyz".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            type_text(&mut editor, "vey");
            let other = fixture.0.path("other");
            fs::write(&other, "1\n2").unwrap();
            editor.execute(&format!("edit {}", other.display()));
            assert_eq!(editor.clipboard_mode(), ClipboardMode::System);
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            editor.handle(Input::Char('P'));
            assert_eq!(editor.context().text, "ab1\nxyz2");
            editor.set_clipboard_mode("separate").unwrap();
            editor.execute("buffer 1");
            assert_eq!(editor.clipboard_mode(), ClipboardMode::Separate);
            set_carets(&mut editor, &[(0, 0)], 0);
            editor.handle(Input::Char('P'));
            assert_eq!(editor.context().text, "insideab\nxyz");
            assert_eq!(fixture.bytes("state"), b"ab\nxyz");
        }

        #[test]
        fn dot_paste_uses_captured_fragments_without_reading_or_publishing() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor
                .apply(vec![Effect::Replace("ab\nxyz".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            type_text(&mut editor, "vey");
            editor.apply(vec![Effect::Replace("1\n2".into())]).unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            editor.handle(Input::Char('P'));
            fixture.external("external");
            fixture.fail("fail-read", true);
            fixture.fail("fail-write", true);
            editor
                .apply(vec![Effect::Replace("3\n4\n5".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 2);
            let before = state(&editor);
            editor.handle(Input::Char('.'));
            assert_eq!(state(&editor), before);
            editor.set_clipboard_mode("separate").unwrap();
            editor.clipboard = vec!["other".into()];
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            editor.handle(Input::Char('.'));
            assert_eq!(editor.context().text, "ab3\nxyz4\n5");
            assert_eq!(editor.clipboard, ["other"]);
            assert_eq!(fixture.bytes("reads").len(), 1);
            assert_eq!(fixture.bytes("writes").len(), 1);
            assert_eq!(fixture.bytes("state"), b"external");
        }

        #[test]
        fn dot_selection_stages_publication_and_rolls_back_step_or_provider_failures() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor
                .apply(vec![Effect::Replace("ab\ncd".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            type_text(&mut editor, "vc");
            editor.handle(Input::Backspace);
            type_text(&mut editor, "X");
            editor.handle(Input::Escape);
            let original_clipboard = fixture.bytes("state");
            editor
                .apply(vec![Effect::Replace("aa\nbb\ncc".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 2);
            editor.handle(Input::Char('v'));
            let before = state(&editor);
            editor.handle(Input::Char('.'));
            assert_eq!(state(&editor), before);
            assert_eq!(fixture.bytes("writes").len(), 1);
            assert_eq!(fixture.bytes("state"), original_clipboard);
            assert!(editor.message().contains("count"));
            editor
                .apply(vec![Effect::Replace("aa\nbb".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            editor.handle(Input::Char('v'));
            editor.active.search_query = "aa".into();
            editor.active.search_match = Some(SearchMatch {
                start: Cursor::default(),
                end_column: 2,
            });
            fixture.fail("fail-write", true);
            let before = state(&editor);
            editor.handle(Input::Char('.'));
            assert_eq!(state(&editor), before);
            assert_eq!(fixture.bytes("state"), original_clipboard);
            assert_eq!(fixture.bytes("writes").len(), 2);
            fixture.fail("fail-write", false);
            let undo = editor.active.undo.len();
            editor.handle(Input::Char('.'));
            assert_eq!(editor.context().text, "XaXb");
            assert_eq!(fixture.bytes("state"), b"a\nb");
            assert_eq!(fixture.bytes("writes").len(), 3);
            assert_eq!(editor.active.undo.len(), undo + 1);
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, "aa\nbb");
            assert_eq!(fixture.bytes("state"), b"a\nb");
        }

        #[test]
        fn dot_unequal_spans_refuses_before_publication_and_preserves_recipe() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor
                .apply(vec![Effect::Replace("ab\nxyz".into())])
                .unwrap();
            set_ranges(
                &mut editor,
                &[
                    (Cursor::default(), Cursor { row: 0, column: 2 }),
                    (Cursor { row: 1, column: 0 }, Cursor { row: 1, column: 3 }),
                ],
                1,
            );
            editor.handle(Input::Char('d'));
            editor
                .apply(vec![Effect::Replace("12\n345".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0)], 0);
            let before = state(&editor);
            editor.handle(Input::Char('.'));
            assert_eq!(state(&editor), before);
            assert_eq!(fixture.bytes("writes").len(), 1);
            set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
            editor.handle(Input::Char('.'));
            assert_eq!(editor.context().text, "\n");
            assert_eq!(fixture.bytes("state"), b"12\n345");
            assert_eq!(fixture.bytes("writes").len(), 2);
        }

        #[test]
        fn dot_cut_follows_current_policy_without_copying_plain_deletes_or_plugin_edits() {
            let fixture = Fixture::new();
            let mut editor = fixture.editor();
            editor.set_clipboard_mode("separate").unwrap();
            editor.apply(vec![Effect::Replace("first".into())]).unwrap();
            type_text(&mut editor, "ved");
            assert_eq!(editor.clipboard, ["first"]);
            assert_eq!(fixture.bytes("writes").len(), 0);
            editor.set_clipboard_mode("system").unwrap();
            editor
                .apply(vec![Effect::Replace("second".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0)], 0);
            editor.handle(Input::Char('.'));
            assert_eq!(editor.context().text, "");
            assert_eq!(fixture.bytes("state"), b"second");
            assert_eq!(editor.clipboard, ["first"]);
            editor.set_clipboard_mode("separate").unwrap();
            editor.apply(vec![Effect::Replace("third".into())]).unwrap();
            set_carets(&mut editor, &[(0, 0)], 0);
            editor.handle(Input::Char('.'));
            assert_eq!(editor.clipboard, ["third"]);
            assert_eq!(fixture.bytes("state"), b"second");
            editor.set_clipboard_mode("system").unwrap();
            editor.apply(vec![Effect::Replace("plain".into())]).unwrap();
            set_carets(&mut editor, &[(0, 0)], 0);
            type_text(&mut editor, "x.");
            type_text(&mut editor, "iX");
            editor.handle(Input::Backspace);
            editor.handle(Input::Delete);
            editor.handle(Input::Escape);
            editor.handle(Input::Char('.'));
            assert_eq!(fixture.bytes("writes").len(), 1);
            assert_eq!(fixture.bytes("reads").len(), 0);
        }
    }

    #[test]
    fn floating_default_tree_starts_filtering_then_escape_navigates_before_close() {
        let directory = Directory::new();
        fs::create_dir(directory.path("dir")).unwrap();
        fs::write(directory.path("dir/first.txt"), "first").unwrap();
        fs::write(directory.path("dir/second.txt"), "second").unwrap();
        let mut editor = project_editor(&directory);
        type_text(&mut editor, " osecond.txt");
        let picker = editor.file_picker().unwrap();
        assert_eq!(picker.view, FileView::Tree);
        assert!(picker.focused && picker.searching);
        assert_eq!(picker.query, "second.txt");
        assert_eq!(
            picker.entries().nth(picker.selected).unwrap().path,
            Path::new("dir/second.txt")
        );
        editor.handle(Input::Escape);
        let picker = editor.file_picker().unwrap();
        assert!(picker.focused && !picker.searching);
        assert_eq!(picker.query, "second.txt");
        assert_eq!(
            picker.entries().nth(picker.selected).unwrap().path,
            Path::new("dir/second.txt")
        );
        editor.handle(Input::Char('i'));
        assert!(editor.file_picker().unwrap().searching);
        assert_eq!(editor.file_picker().unwrap().query, "second.txt");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('h'));
        editor.handle(Input::Char('h'));
        let picker = editor.file_picker().unwrap();
        assert_eq!(picker.entries().len(), 1);
        assert_eq!(picker.entries().next().unwrap().path, Path::new("dir"));
        assert!(!picker.entries().next().unwrap().expanded);
        assert_eq!(picker.query, "second.txt");
        editor.handle(Input::Char('l'));
        assert!(
            editor
                .file_picker()
                .unwrap()
                .entries()
                .next()
                .unwrap()
                .expanded
        );
        editor.handle(Input::Escape);
        assert!(editor.file_picker().is_none());
        assert_eq!(editor.lines(), &[String::new()]);
        editor.set_file_picker_view("list").unwrap();
        type_text(&mut editor, " osecond.txt");
        assert_eq!(editor.file_picker().unwrap().view, FileView::List);
        editor.handle(Input::Enter);
        assert_eq!(editor.lines(), &["second"]);
        assert!(editor.file_picker().is_none());
    }

    #[test]
    fn filter_escape_resume_and_clear_do_not_edit_underlying_buffers_or_history() {
        let directory = Directory::new();
        fs::create_dir_all(directory.path("src/deep")).unwrap();
        fs::write(directory.path("src/deep/needle.txt"), "needle").unwrap();
        fs::write(directory.path("src/other.txt"), "other").unwrap();
        let selected_path = |editor: &Editor| {
            let picker = editor.file_picker().unwrap();
            picker
                .entries()
                .nth(picker.selected)
                .unwrap()
                .path
                .to_owned()
        };
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            for mode in [
                Mode::Normal,
                Mode::Insert,
                Mode::Command,
                Mode::Search,
                Mode::Visual,
            ] {
                let mut editor = project_editor(&directory);
                editor
                    .apply(vec![Effect::Replace("alpha\nbeta".into())])
                    .unwrap();
                editor
                    .apply(vec![Effect::Replace("changed".into())])
                    .unwrap();
                editor.act(Action::Undo);
                set_carets(&mut editor, &[(0, 1), (1, 2)], 1);
                editor.begin_insert();
                editor.active.mode = mode;
                editor.command_line = "original prompt".into();
                editor.open_file_picker(presentation);
                if !editor.file_picker().unwrap().searching {
                    editor.handle(Input::Char('i'));
                }
                editor.count = Some(7);
                let snapshot =
                    |state: &Snapshot| (state.lines.clone(), state.targets.clone(), state.primary);
                let lines = editor.lines().to_owned();
                let targets = editor.active.targets.clone();
                let primary = editor.active.primary;
                let undo: Vec<_> = editor.active.undo.iter().map(&snapshot).collect();
                let redo: Vec<_> = editor.active.redo.iter().map(&snapshot).collect();
                let insert = editor.active.insert_start.as_ref().map(snapshot);
                let buffer = editor.buffer_id();
                let buffers = editor.buffer_count();
                type_text(&mut editor, "needle");
                let expected = PathBuf::from("src/deep/needle.txt");
                assert_eq!(selected_path(&editor), expected);
                editor.handle(Input::Escape);
                assert!(!editor.file_picker().unwrap().searching);
                assert_eq!(editor.file_picker().unwrap().query, "needle");
                assert_eq!(selected_path(&editor), expected);
                editor.handle(Input::Char('i'));
                assert!(editor.file_picker().unwrap().searching);
                assert_eq!(editor.file_picker().unwrap().query, "needle");
                assert_eq!(selected_path(&editor), expected);
                editor.handle(Input::Ctrl('U'));
                assert!(editor.file_picker().unwrap().searching);
                assert!(editor.file_picker().unwrap().query.is_empty());
                assert_eq!(selected_path(&editor), expected);
                type_text(&mut editor, "needle");
                editor.handle(Input::Escape);
                editor.handle(Input::Ctrl('u'));
                assert!(!editor.file_picker().unwrap().searching);
                assert!(editor.file_picker().unwrap().query.is_empty());
                assert_eq!(selected_path(&editor), expected);
                editor.handle(Input::Ctrl('u'));
                assert_eq!(selected_path(&editor), expected);
                editor.handle(Input::Char('i'));
                type_text(&mut editor, "missing");
                editor.handle(Input::Ctrl('j'));
                editor.handle(Input::Ctrl('k'));
                editor.handle(Input::Escape);
                assert_eq!(editor.file_picker().unwrap().entries().len(), 0);
                editor.handle(Input::Ctrl('u'));
                assert_eq!(selected_path(&editor), expected);
                assert!(editor.file_picker().unwrap().focused);
                assert!(!editor.file_picker().unwrap().searching);
                assert_eq!(editor.mode(), mode);
                assert_eq!(editor.lines(), lines);
                assert_eq!(editor.active.targets, targets);
                assert_eq!(editor.active.primary, primary);
                assert_eq!(editor.command_line, "original prompt");
                assert_eq!(editor.count(), Some(7));
                assert_eq!(editor.buffer_id(), buffer);
                assert_eq!(editor.buffer_count(), buffers);
                assert_eq!(
                    editor.active.undo.iter().map(&snapshot).collect::<Vec<_>>(),
                    undo
                );
                assert_eq!(
                    editor.active.redo.iter().map(&snapshot).collect::<Vec<_>>(),
                    redo
                );
                assert_eq!(editor.active.insert_start.as_ref().map(snapshot), insert);
                editor.handle(Input::Escape);
                match presentation {
                    FilePresentation::Floating => assert!(editor.file_picker().is_none()),
                    FilePresentation::Docked => {
                        assert!(!editor.file_picker().unwrap().focused);
                        editor.open_file_picker(presentation);
                        assert!(!editor.file_picker().unwrap().searching);
                        assert_eq!(selected_path(&editor), expected);
                    }
                }
            }
        }
    }

    #[test]
    fn filtered_folder_keys_and_directory_accept_work_in_both_presentations() {
        let directory = Directory::new();
        fs::create_dir_all(directory.path("src/deep")).unwrap();
        fs::write(directory.path("src/deep/needle.txt"), "needle").unwrap();
        fs::write(directory.path("src/other.txt"), "other").unwrap();
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            let mut editor = project_editor(&directory);
            editor.open_file_picker(presentation);
            if !editor.file_picker().unwrap().searching {
                editor.handle(Input::Char('i'));
            }
            type_text(&mut editor, "needle");
            editor.handle(Input::Ctrl('h'));
            let picker = editor.file_picker().unwrap();
            assert!(picker.searching);
            assert_eq!(picker.query, "needle");
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new("src/deep")
            );
            assert!(picker.entries().nth(picker.selected).unwrap().expanded);
            editor.handle(Input::Ctrl('l'));
            let picker = editor.file_picker().unwrap();
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new("src/deep/needle.txt")
            );
            editor.handle(Input::Escape);
            editor.handle(Input::Char('h'));
            editor.handle(Input::Char('h'));
            let picker = editor.file_picker().unwrap();
            assert!(!picker.searching);
            assert_eq!(picker.query, "needle");
            assert_eq!(picker.entries().len(), 2);
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new("src/deep")
            );
            assert!(!picker.entries().nth(picker.selected).unwrap().expanded);
            editor.handle(Input::Char('l'));
            assert!(
                editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .nth(1)
                    .unwrap()
                    .expanded
            );
            editor.handle(Input::Char('l'));
            editor.handle(Input::Char('h'));
            editor.handle(Input::Enter);
            assert!(
                !editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .nth(1)
                    .unwrap()
                    .expanded
            );
            editor.handle(Input::Enter);
            assert!(
                editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .nth(1)
                    .unwrap()
                    .expanded
            );
            editor.handle(Input::Char('i'));
            editor.handle(Input::Enter);
            let picker = editor.file_picker().unwrap();
            assert!(!picker.searching && picker.focused);
            assert_eq!(picker.query, "needle");
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new("src/deep")
            );
            assert!(!picker.entries().nth(picker.selected).unwrap().expanded);
            assert_eq!(editor.context().text, "");
            editor.handle(Input::Ctrl('r'));
            editor.handle(Input::Ctrl('t'));
            editor.handle(Input::Ctrl('t'));
            let picker = editor.file_picker().unwrap();
            assert!(!picker.searching && picker.focused);
            assert_eq!(picker.query, "needle");
            assert!(!picker.entries().nth(picker.selected).unwrap().expanded);
            if presentation == FilePresentation::Docked {
                editor.handle(Input::Escape);
                editor.open_file_picker(presentation);
                assert!(!editor.file_picker().unwrap().searching);
                assert_eq!(editor.file_picker().unwrap().query, "needle");
            }
            editor.open_file_picker(FilePresentation::Floating);
            assert!(editor.file_picker().unwrap().searching);
            assert_eq!(editor.file_picker().unwrap().query, "needle");
        }
    }

    #[test]
    fn filter_clear_respects_navigation_bindings_and_does_not_clear_palette_or_idle_dock() {
        let directory = Directory::new();
        for name in ["a.txt", "b.txt"] {
            fs::write(directory.path(name), "text").unwrap();
        }
        for view in [FileView::List, FileView::Tree] {
            let mut editor = project_editor(&directory);
            editor.open_file_picker(FilePresentation::Docked);
            editor.file_picker.as_mut().unwrap().set_view(view);
            if view == FileView::Tree {
                editor.handle(Input::Char('i'));
            }
            type_text(&mut editor, "txt");
            editor
                .bind("selection", "ctrl+u", Some("core.down".into()))
                .unwrap();
            editor.handle(Input::Ctrl('u'));
            assert_eq!(editor.file_picker().unwrap().query, "txt");
            assert_eq!(editor.file_picker().unwrap().selected, 1);
            editor.bind("selection", "ctrl+u", None).unwrap();
            editor.handle(Input::Ctrl('u'));
            assert_eq!(editor.file_picker().unwrap().query, "txt");
            editor.selection_bindings.remove(&Input::Ctrl('u'));
            if view == FileView::Tree {
                editor.bind("tree", "ctrl+u", None).unwrap();
                editor.handle(Input::Ctrl('u'));
                assert_eq!(editor.file_picker().unwrap().query, "txt");
                editor.tree_bindings.remove(&Input::Ctrl('u'));
            }
            editor.handle(Input::Ctrl('u'));
            assert!(editor.file_picker().unwrap().query.is_empty());
            assert_eq!(editor.file_picker().unwrap().selected, 1);
            assert_eq!(
                editor.file_picker().unwrap().searching,
                view == FileView::Tree
            );
            type_text(&mut editor, "txt");
            editor.handle(Input::Char('\t'));
            editor.handle(Input::Ctrl('u'));
            assert_eq!(editor.file_picker().unwrap().query, "txt");
            editor.handle(Input::Ctrl('p'));
            type_text(&mut editor, "core");
            editor.handle(Input::Ctrl('u'));
            assert_eq!(editor.palette().unwrap().query, "core");
            assert_eq!(editor.file_picker().unwrap().query, "txt");
        }
    }

    #[test]
    fn selection_navigation_wraps_without_touching_any_underlying_mode() {
        let directory = Directory::new();
        for name in ["a.txt", "b.txt", "c.txt"] {
            fs::write(directory.path(name), "file text").unwrap();
        }
        for surface in [
            None,
            Some(FilePresentation::Floating),
            Some(FilePresentation::Docked),
        ] {
            for mode in [
                Mode::Normal,
                Mode::Insert,
                Mode::Command,
                Mode::Search,
                Mode::Visual,
            ] {
                let mut editor = project_editor(&directory);
                editor
                    .apply(vec![Effect::Replace("alpha\nbeta".into())])
                    .unwrap();
                set_carets(&mut editor, &[(0, 1), (1, 2)], 1);
                editor.active.mode = mode;
                editor.command_line = "original prompt".into();
                if let Some(presentation) = surface {
                    editor.open_file_picker(presentation);
                    editor
                        .file_picker
                        .as_mut()
                        .unwrap()
                        .set_view(FileView::List);
                    type_text(&mut editor, "txt");
                } else {
                    editor.handle(Input::Ctrl('p'));
                    type_text(&mut editor, "core");
                }
                let list = |editor: &Editor| {
                    if let Some(picker) = editor.file_picker() {
                        (
                            picker.query.clone(),
                            picker.selected,
                            picker.entries().len(),
                        )
                    } else {
                        let palette = editor.palette().unwrap();
                        (
                            palette.query.clone(),
                            palette.selected,
                            palette.entries.len(),
                        )
                    }
                };
                let (query, _, len) = list(&editor);
                assert!(len > 1);
                let snapshot =
                    |state: &Snapshot| (state.lines.clone(), state.targets.clone(), state.primary);
                let text = editor.context().text;
                let targets = editor.active.targets.clone();
                let primary = editor.active.primary;
                let undo: Vec<_> = editor.active.undo.iter().map(&snapshot).collect();
                let redo: Vec<_> = editor.active.redo.iter().map(&snapshot).collect();
                let insert = editor.active.insert_start.as_ref().map(snapshot);
                editor.count = Some(7);
                for (input, selected) in [
                    (Input::Ctrl('K'), len - 1),
                    (Input::Ctrl('J'), 0),
                    (Input::Ctrl('j'), 1),
                    (Input::Ctrl('k'), 0),
                    (Input::Up, len - 1),
                    (Input::Down, 0),
                    (Input::Ctrl('n'), 1),
                ] {
                    assert_eq!(editor.handle(input), None);
                    assert_eq!(list(&editor), (query.clone(), selected, len));
                }
                assert_eq!(editor.mode(), mode);
                assert_eq!(editor.context().text, text);
                assert_eq!(editor.active.targets, targets);
                assert_eq!(editor.active.primary, primary);
                assert_eq!(editor.command_line, "original prompt");
                assert_eq!(editor.count(), Some(7));
                assert_eq!(
                    editor.active.undo.iter().map(&snapshot).collect::<Vec<_>>(),
                    undo
                );
                assert_eq!(
                    editor.active.redo.iter().map(&snapshot).collect::<Vec<_>>(),
                    redo
                );
                assert_eq!(editor.active.insert_start.as_ref().map(snapshot), insert);
                type_text(&mut editor, "missing");
                assert_eq!(list(&editor).2, 0);
                for input in [Input::Ctrl('j'), Input::Ctrl('k'), Input::Enter] {
                    assert_eq!(editor.handle(input), None);
                    assert_eq!(list(&editor).1, 0);
                    assert_eq!(editor.context().text, text);
                    assert_eq!(editor.mode(), mode);
                }
            }
        }
    }

    #[test]
    fn selection_remaps_and_disables_are_shared_and_invalid_edits_are_atomic() {
        let directory = Directory::new();
        for name in ["a.txt", "b.txt", "c.txt"] {
            fs::write(directory.path(name), "file text").unwrap();
        }
        for surface in [
            None,
            Some(FilePresentation::Floating),
            Some(FilePresentation::Docked),
        ] {
            let mut editor = project_editor(&directory);
            assert_eq!(
                editor.selection_navigation_hint(),
                "Ctrl+j/Ctrl+n/Down next · Ctrl+k/Up previous"
            );
            type_text(&mut editor, "3 b");
            let pending = editor.leader_pending().unwrap().to_owned();
            editor
                .bind("selection", "x", Some("core.down".into()))
                .unwrap();
            editor
                .bind("selection", "z", Some("core.up".into()))
                .unwrap();
            editor.bind("selection", "ctrl+j", None).unwrap();
            editor.bind("selection", "!", None).unwrap();
            assert_eq!(editor.count(), Some(3));
            assert_eq!(editor.leader_pending(), Some(pending.as_str()));
            assert_eq!(
                editor.selection_navigation_hint(),
                "Ctrl+n/Down/x next · Ctrl+k/Up/z previous"
            );
            let hint = editor.selection_navigation_hint().to_owned();
            for (mode, key, target) in [
                ("selection", "x", Some("core.delete")),
                ("selection", "x", Some("core.palette")),
                ("selection", "x", Some("w")),
                ("selection", "leader x", Some("core.down")),
                ("selection", "LEADER x", None),
                ("selection", "x z", Some("core.up")),
                ("selection", "alt+x", Some("core.up")),
                ("invalid", "x", Some("core.up")),
            ] {
                assert!(editor.bind(mode, key, target.map(str::to_owned)).is_err());
                assert_eq!(editor.selection_navigation_hint(), hint);
                assert_eq!(editor.count(), Some(3));
                assert_eq!(editor.leader_pending(), Some(pending.as_str()));
            }
            editor.cancel_leader();
            // Editing bindings cannot disable or remap list bindings.
            editor
                .bind("normal", "x", Some("core.insert".into()))
                .unwrap();
            editor.bind("normal", "ctrl+k", None).unwrap();
            if let Some(presentation) = surface {
                editor.open_file_picker(presentation);
                editor
                    .file_picker
                    .as_mut()
                    .unwrap()
                    .set_view(FileView::List);
            } else {
                editor.handle(Input::Ctrl('p'));
            }
            let selected = |editor: &Editor| {
                if let Some(picker) = editor.file_picker() {
                    picker.selected
                } else {
                    editor.palette().unwrap().selected
                }
            };
            for (input, expected) in [
                (Input::Char('x'), 1),
                (Input::Ctrl('j'), 1),
                (Input::Char('!'), 1),
                (Input::Char('z'), 0),
                (Input::Char('x'), 1),
                (Input::Ctrl('k'), 0),
            ] {
                editor.handle(input);
                assert_eq!(selected(&editor), expected);
                assert_eq!(editor.mode(), Mode::Normal);
            }
            // Updating the map does not rebuild/reset the selected list.
            editor.handle(Input::Char('x'));
            editor
                .bind("selection", "ctrl+p", Some("core.down".into()))
                .unwrap();
            assert_eq!(selected(&editor), 1);
            editor.handle(Input::Ctrl('p'));
            assert_eq!(selected(&editor), 2);
            editor.bind("selection", "backspace", None).unwrap();
            type_text(&mut editor, "a");
            editor.handle(Input::Backspace);
            let query = if let Some(picker) = editor.file_picker() {
                &picker.query
            } else {
                &editor.palette().unwrap().query
            };
            assert_eq!(query, "a");
            for key in ["down", "ctrl+n", "x", "ctrl+p"] {
                editor.bind("selection", key, None).unwrap();
            }
            assert_eq!(
                editor.selection_navigation_hint(),
                "unbound next · Ctrl+k/Up/z previous"
            );
            editor.handle(Input::Escape);
            editor.handle(Input::Char('x'));
            assert_eq!(editor.mode(), Mode::Insert);
        }
    }

    #[test]
    fn ctrl_j_is_distinct_from_enter_and_preserves_editor_defaults() {
        assert_eq!(parse_key("CTRL+J").unwrap(), Input::Ctrl('j'));
        for (key, input) in [
            ("ctrl+m", Input::Enter),
            ("ctrl+h", Input::Ctrl('h')),
            ("ctrl+i", Input::Char('\t')),
        ] {
            assert_eq!(parse_key(key).unwrap(), input);
        }
        let mut editor = editor();
        editor
            .bind("normal", "ctrl+j", Some("core.insert".into()))
            .unwrap();
        editor.handle(Input::Enter);
        assert_eq!(editor.mode(), Mode::Normal);
        editor.handle(Input::Ctrl('j'));
        assert_eq!(editor.mode(), Mode::Insert);
        editor.bind("insert", "enter", None).unwrap();
        type_text(&mut editor, "one");
        editor.handle(Input::Enter);
        editor.handle(Input::Ctrl('j'));
        type_text(&mut editor, "two");
        assert_eq!(editor.context().text, "one\ntwo");
        editor.handle(Input::Escape);
        editor.register(plugin("fixture", &["greet"])).unwrap();
        type_text(&mut editor, ":greet arguments");
        let invocation = editor.handle(Input::Ctrl('j')).unwrap();
        assert_eq!(invocation.command, "greet");
        assert_eq!(invocation.args, "arguments");
        assert_eq!(editor.mode(), Mode::Normal);
        type_text(&mut editor, "/two");
        editor.handle(Input::Ctrl('j'));
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.active.search_query, "two");
        assert_eq!(editor.cursor().row, 1);
        editor
            .bind("visual", "ctrl+j", Some("core.up".into()))
            .unwrap();
        editor.handle(Input::Char('v'));
        editor.handle(Input::Ctrl('j'));
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.cursor().row, 0);
    }

    #[test]
    fn ctrl_j_navigates_lists_while_enter_accepts() {
        let directory = Directory::new();
        fs::write(directory.path("a.txt"), "first").unwrap();
        fs::write(directory.path("b.txt"), "second").unwrap();
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            let mut editor = project_editor(&directory);
            editor.open_file_picker(presentation);
            editor.handle(Input::Ctrl('j'));
            assert_eq!(editor.file_picker().unwrap().selected, 1);
            assert_eq!(editor.context().text, "");
            editor.handle(Input::Enter);
            assert_eq!(editor.context().text, "second");
            assert_eq!(editor.path(), Some(directory.path("b.txt").as_path()));
        }
        let mut editor = editor();
        editor
            .register(plugin("fixture", &["greet_one", "greet_two"]))
            .unwrap();
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "greet");
        editor.handle(Input::Ctrl('j'));
        assert_eq!(editor.palette().unwrap().selected, 1);
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.command_line, "");
        editor.handle(Input::Enter);
        assert!(editor.palette().is_none());
        assert_eq!(editor.mode(), Mode::Command);
        assert_eq!(editor.command_line, "greet_two ");
    }

    #[test]
    fn file_actions_default_leaders_palette_and_side_configuration() {
        let directory = Directory::new();
        fs::write(directory.path("file.txt"), "abcdef").unwrap();
        for visual in [false, true] {
            let mut editor = project_editor(&directory);
            editor
                .apply(vec![Effect::Replace("abcdef".into())])
                .unwrap();
            if visual {
                type_text(&mut editor, "vl");
            }
            let mode = editor.mode();
            let selections = editor.selections();
            let carets = editor.carets();
            for (suffix, presentation) in [
                ("3 o", FilePresentation::Floating),
                ("2 e", FilePresentation::Docked),
            ] {
                type_text(&mut editor, suffix);
                let picker = editor.file_picker().unwrap();
                assert_eq!(picker.presentation, presentation);
                assert!(picker.focused);
                assert_eq!(editor.mode(), mode);
                assert_eq!(editor.selections(), selections);
                assert_eq!(editor.carets(), carets);
                assert_eq!(editor.count(), None);
                assert_eq!(editor.leader_pending(), None);
                editor.handle(Input::Ctrl('w'));
                assert!(editor.file_picker().is_none());
            }
            editor.handle(Input::Ctrl('p'));
            for (name, binding) in [
                ("core.file_picker", "Space o"),
                ("core.file_explorer", "Space e"),
            ] {
                let entry = palette_entry(&editor, name);
                assert!(entry.enabled);
                assert_eq!(entry.bindings, vec![binding]);
            }
            editor.handle(Input::Escape);
            assert_eq!(editor.file_explorer_side(), DockSide::Right);
            for (name, side) in [
                ("LEFT", DockSide::Left),
                ("rIgHt", DockSide::Right),
                ("top", DockSide::Top),
                ("BOTTOM", DockSide::Bottom),
            ] {
                editor.set_file_explorer_side(name).unwrap();
                assert_eq!(editor.file_explorer_side(), side);
            }
            assert!(editor.set_file_explorer_side("middle").is_err());
            assert_eq!(editor.file_explorer_side(), DockSide::Bottom);
            assert!(
                editor
                    .bind("insert", "ctrl+o", Some("core.file_picker".into()))
                    .is_err()
            );
            assert!(
                editor
                    .bind("command", "ctrl+e", Some("core.file_explorer".into()))
                    .is_err()
            );
        }
    }

    #[test]
    fn picker_focus_literal_input_navigation_and_empty_selection() {
        let directory = Directory::new();
        for name in ["a space 界[e\u{301}].txt", "b.txt", "c.txt"] {
            fs::write(directory.path(name), "text").unwrap();
        }
        let mut editor = project_editor(&directory);
        editor.set_file_picker_view("list").unwrap();
        type_text(&mut editor, " o");
        editor.handle(Input::Ctrl('K'));
        assert_eq!(editor.file_picker().unwrap().selected, 2);
        editor.handle(Input::Ctrl('N'));
        assert_eq!(editor.file_picker().unwrap().selected, 0);
        editor.handle(Input::Up);
        editor.handle(Input::Down);
        assert_eq!(editor.file_picker().unwrap().selected, 0);
        type_text(&mut editor, "界 SPACE [E\u{301}]");
        assert_eq!(editor.file_picker().unwrap().entries().len(), 1);
        assert_eq!(editor.context().text, "");
        assert_eq!(editor.count(), None);
        assert_eq!(editor.leader_pending(), None);
        let query = editor.file_picker().unwrap().query.clone();
        editor.handle(Input::Paste("ignored 5 b n".into()));
        assert_eq!(editor.file_picker().unwrap().query, query);
        editor.handle(Input::Enter);
        assert!(editor.file_picker().is_none());
        assert_eq!(
            editor.path(),
            Some(directory.path("a space 界[e\u{301}].txt").as_path())
        );
        assert_eq!(editor.context().text, "text");
        type_text(&mut editor, " o");
        type_text(&mut editor, "e\u{301}👩‍💻");
        editor.handle(Input::Backspace);
        assert_eq!(editor.file_picker().unwrap().query, "e\u{301}");
        editor.handle(Input::Backspace);
        assert_eq!(editor.file_picker().unwrap().query, "");
        editor.handle(Input::Backspace);
        type_text(&mut editor, "missing 123");
        let id = editor.buffer_id();
        editor.handle(Input::Up);
        editor.handle(Input::Down);
        editor.handle(Input::Enter);
        assert_eq!(editor.buffer_id(), id);
        assert_eq!(editor.file_picker().unwrap().selected, 0);
        assert!(editor.file_picker().unwrap().focused);
        editor.handle(Input::Escape);
        let empty = Directory::new();
        editor.project_root = empty.0.clone();
        type_text(&mut editor, " e");
        editor.handle(Input::Up);
        editor.handle(Input::Down);
        editor.handle(Input::Ctrl('j'));
        editor.handle(Input::Ctrl('k'));
        editor.handle(Input::Enter);
        assert_eq!(editor.buffer_id(), id);
        assert_eq!(editor.file_picker().unwrap().entries().len(), 0);
    }

    #[test]
    fn picker_conversion_reuses_query_and_scan_refreshes_only_on_request() {
        let directory = Directory::new();
        fs::write(directory.path("keep.txt"), "text").unwrap();
        let mut editor = project_editor(&directory);
        type_text(&mut editor, " eikeep");
        editor.handle(Input::Char('\t'));
        assert!(!editor.file_picker().unwrap().focused);
        fs::write(directory.path("keep new.txt"), "new").unwrap();
        type_text(&mut editor, " o");
        let picker = editor.file_picker().unwrap();
        assert_eq!(picker.presentation, FilePresentation::Floating);
        assert_eq!(picker.query, "keep");
        assert_eq!(picker.entries().len(), 1);
        editor.open_file_picker(FilePresentation::Docked);
        assert_eq!(editor.file_picker().unwrap().query, "keep");
        editor.handle(Input::Ctrl('R'));
        assert_eq!(editor.file_picker().unwrap().entries().len(), 2);
        assert_eq!(editor.file_picker().unwrap().query, "keep");
        editor.handle(Input::Char('\t'));
        assert!(!editor.file_picker().unwrap().focused);
        type_text(&mut editor, " e");
        assert!(editor.file_picker().unwrap().focused);
        assert_eq!(editor.file_picker().unwrap().query, "keep");
        fs::remove_file(directory.path("keep new.txt")).unwrap();
        editor.handle(Input::Ctrl('r'));
        assert_eq!(editor.file_picker().unwrap().entries().len(), 1);
        editor.handle(Input::Ctrl('w'));
        assert!(editor.file_picker().is_none());
        type_text(&mut editor, " o");
        assert_eq!(editor.file_picker().unwrap().query, "");
        editor.handle(Input::Escape);
        assert!(editor.file_picker().unwrap().focused);
        editor.handle(Input::Escape);
        assert!(editor.file_picker().is_none());
    }

    #[test]
    fn picker_open_reuses_loaded_dirty_buffer_and_dock_survives_lifecycle() {
        let directory = Directory::new();
        let a = directory.path("a space 界.txt");
        let b = directory.path("b.txt");
        fs::write(&a, "original").unwrap();
        fs::write(&b, "other").unwrap();
        let mut editor = project_editor(&directory);
        editor.execute(&format!("edit {}", a.display()));
        editor.apply(vec![Effect::Replace("dirty".into())]).unwrap();
        type_text(&mut editor, "vl");
        let selections = editor.selections();
        let id = editor.buffer_id();
        editor.execute(&format!("edit {}", b.display()));
        fs::write(&a, b"\xff").unwrap();
        type_text(&mut editor, " eia space 界");
        editor.handle(Input::Enter);
        assert_eq!(editor.buffer_id(), id);
        assert_eq!(editor.buffer_count(), 3);
        assert_eq!(editor.context().text, "dirty");
        assert!(editor.dirty());
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.selections(), selections);
        assert!(!editor.file_picker().unwrap().focused);
        assert_eq!(editor.file_picker().unwrap().query, "a space 界");
        editor.execute("bnext");
        assert!(editor.file_picker().is_some());
        editor.execute("bdelete");
        assert!(editor.file_picker().is_some());
        editor.execute("buffer 1");
        assert_eq!(
            editor.file_picker().unwrap().presentation,
            FilePresentation::Docked
        );
        assert_eq!(editor.file_picker().unwrap().query, "a space 界");
    }

    #[test]
    fn failed_picker_selection_preserves_visual_state_and_insert_group() {
        let directory = Directory::new();
        let bad = directory.path("bad.txt");
        fs::write(&bad, b"\xff").unwrap();
        let mut editor = project_editor(&directory);
        editor
            .apply(vec![Effect::Replace("abcdef".into())])
            .unwrap();
        type_text(&mut editor, "llvhh");
        let selections = editor.selections();
        let carets = editor.carets();
        let undo = editor.active.undo.len();
        type_text(&mut editor, " obad");
        editor.handle(Input::Enter);
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.selections(), selections);
        assert_eq!(editor.carets(), carets);
        assert_eq!(editor.context().text, "abcdef");
        assert_eq!(editor.active.undo.len(), undo);
        assert_eq!(editor.next_buffer_id, 2);
        assert_eq!(editor.buffer_count(), 1);
        assert!(editor.file_picker().unwrap().focused);
        assert!(
            editor
                .file_picker()
                .unwrap()
                .error
                .as_ref()
                .unwrap()
                .contains("Open failed")
        );
        editor.handle(Input::Down);
        assert!(editor.file_picker().unwrap().error.is_none());
        editor.handle(Input::Enter);
        editor.handle(Input::Backspace);
        assert!(editor.file_picker().unwrap().error.is_none());
        editor.handle(Input::Escape);
        editor.handle(Input::Escape);
        editor.handle(Input::Escape);
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "X");
        editor.open_file_picker(FilePresentation::Docked);
        editor.handle(Input::Enter);
        assert_eq!(editor.mode(), Mode::Insert);
        assert!(editor.active.insert_start.is_some());
        assert!(editor.file_picker().unwrap().error.is_some());
        fs::remove_file(&bad).unwrap();
        editor.handle(Input::Enter);
        assert_eq!(editor.buffer_id(), 1);
        assert_eq!(editor.mode(), Mode::Insert);
        assert!(editor.file_picker().unwrap().error.is_some());
        fs::create_dir(&bad).unwrap();
        editor.handle(Input::Enter);
        assert_eq!(editor.buffer_count(), 1);
        assert!(editor.file_picker().unwrap().focused);
        editor.handle(Input::Escape);
        assert!(!editor.file_picker().unwrap().focused);
        type_text(&mut editor, "Y");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "abcdef");
        assert!(editor.file_picker().is_some());
    }

    #[test]
    fn picker_palette_and_external_commands_are_mutually_exclusive() {
        let directory = Directory::new();
        fs::write(directory.path("file.txt"), "text").unwrap();
        let mut editor = project_editor(&directory);
        editor.handle(Input::Ctrl('p'));
        editor.open_file_picker(FilePresentation::Docked);
        assert!(editor.palette().is_none());
        editor.handle(Input::Ctrl('p'));
        assert!(editor.palette().is_some());
        assert!(!editor.file_picker().unwrap().focused);
        type_text(&mut editor, "file picker");
        editor.handle(Input::Enter);
        assert!(editor.palette().is_none());
        assert_eq!(
            editor.file_picker().unwrap().presentation,
            FilePresentation::Floating
        );
        assert!(editor.file_picker().unwrap().focused);
        editor.handle(Input::Ctrl('p'));
        assert!(editor.file_picker().is_none());
        assert!(editor.palette().is_some());
        editor.handle(Input::Escape);
        type_text(&mut editor, " o");
        editor.execute("buffers");
        assert!(editor.file_picker().is_none());
        type_text(&mut editor, " eifile");
        editor.execute("buffers");
        assert!(!editor.file_picker().unwrap().focused);
        assert_eq!(editor.file_picker().unwrap().query, "file");
        type_text(&mut editor, " e");
        editor.handle(Input::Ctrl('w'));
        assert!(editor.file_picker().is_none());
    }

    #[test]
    fn unfocused_dock_keeps_editor_counts_leaders_palette_and_literal_input() {
        let directory = Directory::new();
        fs::write(directory.path("file.txt"), "text").unwrap();
        let mut editor = project_editor(&directory);
        editor
            .apply(vec![Effect::Replace("a\nb\nc\nd".into())])
            .unwrap();
        type_text(&mut editor, " eifile");
        editor.handle(Input::Char('\t'));
        type_text(&mut editor, "2j");
        assert_eq!(editor.cursor().row, 2);
        assert_eq!(editor.file_picker().unwrap().query, "file");
        type_text(&mut editor, "3 b");
        assert_eq!(editor.leader_pending(), Some("Space b"));
        assert_eq!(editor.count(), Some(3));
        editor.handle(Input::Escape);
        type_text(&mut editor, "i o e123");
        editor.handle(Input::Paste(" literal".into()));
        assert!(editor.context().text.contains(" o e123 literal"));
        assert_eq!(editor.file_picker().unwrap().query, "file");
        editor.handle(Input::Escape);
        type_text(&mut editor, ": o e123");
        assert_eq!(editor.mode(), Mode::Command);
        assert_eq!(editor.command_line(), " o e123");
        editor.handle(Input::Escape);
        type_text(&mut editor, "/ o e123");
        assert_eq!(editor.mode(), Mode::Search);
        assert_eq!(editor.command_line(), " o e123");
        editor.handle(Input::Escape);
        type_text(&mut editor, "  ");
        assert!(editor.palette().is_some());
        assert!(!editor.file_picker().unwrap().focused);
    }

    #[test]
    fn canceling_picker_does_not_commit_insert_and_root_failure_is_not_empty_success() {
        let directory = Directory::new();
        let mut editor = project_editor(&directory);
        type_text(&mut editor, "iX");
        editor.open_file_picker(FilePresentation::Floating);
        editor.handle(Input::Paste("ignored".into()));
        editor.handle(Input::Escape);
        assert!(editor.file_picker().unwrap().focused);
        editor.handle(Input::Escape);
        assert_eq!(editor.mode(), Mode::Insert);
        assert!(editor.active.insert_start.is_some());
        assert_eq!(editor.context().text, "X");
        type_text(&mut editor, "Y");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        fs::remove_dir_all(&directory.0).unwrap();
        type_text(&mut editor, " o");
        assert!(editor.file_picker().is_none());
        assert!(editor.message().contains("File scan failed"));
        assert_eq!(editor.buffer_count(), 1);
    }

    #[cfg(unix)]
    #[test]
    fn picker_opens_raw_paths_even_when_sanitized_display_labels_collide() {
        let directory = Directory::new();
        let names = [PathBuf::from("same\n.txt"), PathBuf::from("same\t.txt")];
        fs::write(directory.0.join(&names[0]), "first").unwrap();
        fs::write(directory.0.join(&names[1]), "second").unwrap();
        let mut editor = project_editor(&directory);
        for (name, text) in names.iter().zip(["first", "second"]) {
            type_text(&mut editor, " osame");
            let picker = editor.file_picker.as_mut().unwrap();
            assert_eq!(picker.entries().len(), 2);
            assert_eq!(
                picker.entries().next().unwrap().label,
                picker.entries().last().unwrap().label,
            );
            assert!(
                picker
                    .entries()
                    .all(|entry| !entry.label.chars().any(char::is_control))
            );
            let selected = picker
                .entries()
                .position(|entry| entry.path == name.as_path())
                .unwrap();
            picker.selected = selected;
            editor.handle(Input::Enter);
            assert_eq!(editor.path(), Some(directory.0.join(name).as_path()));
            assert_eq!(editor.context().text, text);
        }
        assert_eq!(editor.buffer_count(), 3);
    }

    #[test]
    fn file_view_preferences_are_independent_atomic_and_applied_to_current_presentation() {
        let directory = Directory::new();
        fs::create_dir(directory.path("folder")).unwrap();
        fs::write(directory.path("file.txt"), "text").unwrap();
        let mut editor = project_editor(&directory);
        editor.open_file_picker(FilePresentation::Docked);
        assert_eq!(editor.file_picker().unwrap().view, FileView::Tree);
        editor.set_file_picker_view("TREE").unwrap();
        assert_eq!(editor.file_picker().unwrap().view, FileView::Tree);
        editor.set_file_explorer_view("LiSt").unwrap();
        assert_eq!(editor.file_picker().unwrap().view, FileView::List);
        for invalid in ["", "flat", " tree "] {
            assert!(editor.set_file_picker_view(invalid).is_err());
            assert!(editor.set_file_explorer_view(invalid).is_err());
            assert_eq!(editor.file_picker_view(), FileView::Tree);
            assert_eq!(editor.file_explorer_view(), FileView::List);
            assert_eq!(editor.file_picker().unwrap().view, FileView::List);
        }
        editor.handle(Input::Ctrl('t'));
        assert_eq!(editor.file_picker().unwrap().view, FileView::Tree);
        assert_eq!(editor.file_explorer_view(), FileView::List);
        editor.handle(Input::Char('\t'));
        editor.open_file_picker(FilePresentation::Docked);
        assert_eq!(editor.file_picker().unwrap().view, FileView::List);
        editor.open_file_picker(FilePresentation::Floating);
        assert_eq!(editor.file_picker().unwrap().view, FileView::Tree);
        assert_eq!(
            editor.file_picker().unwrap().presentation,
            FilePresentation::Floating
        );
        editor.set_file_explorer_view("tree").unwrap();
        editor.set_file_picker_view("list").unwrap();
        assert_eq!(editor.file_picker().unwrap().view, FileView::List);
        assert_eq!(editor.file_picker().unwrap().entries().len(), 1);
    }

    #[test]
    fn tree_hjkl_navigates_normal_and_control_hjkl_navigates_filter_without_changing_text() {
        let directory = Directory::new();
        fs::create_dir(directory.path("dir")).unwrap();
        fs::write(directory.path("dir/hjkl-a.txt"), "a").unwrap();
        fs::write(directory.path("dir/hjkl-b.txt"), "b").unwrap();
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            let mut editor = project_editor(&directory);
            editor.set_file_picker_view("tree").unwrap();
            editor.open_file_picker(presentation);
            if presentation == FilePresentation::Floating {
                editor.handle(Input::Escape);
            }
            let selected = |editor: &Editor| {
                let picker = editor.file_picker().unwrap();
                picker
                    .entries()
                    .nth(picker.selected)
                    .unwrap()
                    .path
                    .to_owned()
            };
            editor.handle(Input::Char('l'));
            assert!(
                editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .next()
                    .unwrap()
                    .expanded
            );
            editor.handle(Input::Char('l'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-a.txt"));
            editor.handle(Input::Char('j'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-b.txt"));
            editor.handle(Input::Char('k'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-a.txt"));
            editor.handle(Input::Char('h'));
            assert_eq!(selected(&editor), Path::new("dir"));
            assert!(
                editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .next()
                    .unwrap()
                    .expanded
            );
            editor.handle(Input::Char('h'));
            assert!(
                !editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .next()
                    .unwrap()
                    .expanded
            );
            editor.handle(Input::Char('i'));
            type_text(&mut editor, "hjkl");
            assert_eq!(editor.file_picker().unwrap().query, "hjkl");
            assert_eq!(selected(&editor), Path::new("dir/hjkl-a.txt"));
            editor.handle(Input::Ctrl('j'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-b.txt"));
            editor.handle(Input::Ctrl('k'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-a.txt"));
            editor.handle(Input::Ctrl('h'));
            assert_eq!(selected(&editor), Path::new("dir"));
            editor.handle(Input::Ctrl('l'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-a.txt"));
            assert_eq!(editor.file_picker().unwrap().query, "hjkl");
            editor.handle(Input::Escape);
            assert!(editor.file_picker().unwrap().focused);
            assert_eq!(selected(&editor), Path::new("dir/hjkl-a.txt"));
            assert_eq!(editor.file_picker().unwrap().query, "hjkl");
            editor.handle(Input::Ctrl('u'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-a.txt"));
            editor.handle(Input::Char('h'));
            editor.handle(Input::Char('h'));
            assert!(
                !editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .next()
                    .unwrap()
                    .expanded
            );
            editor.bind("tree", "j", Some("core.up".into())).unwrap();
            editor.bind("tree", "k", None).unwrap();
            editor.handle(Input::Char('l'));
            editor.handle(Input::Char('j'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-b.txt"));
            editor.handle(Input::Char('k'));
            assert_eq!(selected(&editor), Path::new("dir/hjkl-b.txt"));
            editor.handle(Input::Char('i'));
            type_text(&mut editor, "jk");
            assert_eq!(editor.file_picker().unwrap().query, "jk");
            assert_eq!(editor.lines(), &[String::new()]);
            assert_eq!(editor.mode(), Mode::Normal);
            assert_eq!(editor.cursor(), Cursor::default());
        }
    }

    #[test]
    fn tree_browse_and_search_have_separate_input_and_two_stage_escape() {
        let directory = Directory::new();
        fs::create_dir_all(directory.path("folder/deep")).unwrap();
        fs::write(directory.path("folder/deep/needle.txt"), "text").unwrap();
        fs::write(directory.path("folder/other.txt"), "other").unwrap();
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            for mode in [
                Mode::Normal,
                Mode::Visual,
                Mode::Insert,
                Mode::Command,
                Mode::Search,
            ] {
                let mut editor = project_editor(&directory);
                editor
                    .apply(vec![Effect::Replace("alpha\nbeta".into())])
                    .unwrap();
                set_carets(&mut editor, &[(0, 1), (1, 2)], 1);
                editor.active.mode = mode;
                editor.command_line = "underlying".into();
                let targets = editor.active.targets.clone();
                let text = editor.context().text;
                let undo = editor.active.undo.len();
                editor.set_file_picker_view("tree").unwrap();
                editor.open_file_picker(presentation);
                if presentation == FilePresentation::Floating {
                    editor.handle(Input::Escape);
                }
                type_text(&mut editor, "123 b xyz");
                editor.handle(Input::Paste("ignored".into()));
                editor.handle(Input::Backspace);
                assert_eq!(editor.file_picker().unwrap().query, "");
                assert_eq!(editor.count(), None);
                assert_eq!(editor.leader_pending(), None);
                editor.handle(Input::Enter);
                assert_eq!(editor.buffer_count(), 1);
                assert!(
                    editor
                        .file_picker()
                        .unwrap()
                        .entries()
                        .next()
                        .unwrap()
                        .expanded
                );
                editor.handle(Input::Ctrl('l'));
                assert_eq!(
                    editor.file_picker().unwrap().entries().nth(1).unwrap().path,
                    Path::new("folder/deep")
                );
                assert_eq!(editor.file_picker().unwrap().selected, 1);
                editor.handle(Input::Ctrl('h'));
                assert_eq!(editor.file_picker().unwrap().selected, 0);
                type_text(&mut editor, "ideep/");
                assert!(editor.file_picker().unwrap().searching);
                assert_eq!(editor.file_picker().unwrap().query, "deep/");
                editor.handle(Input::Ctrl('H'));
                assert_eq!(editor.file_picker().unwrap().query, "deep/");
                editor.handle(Input::Backspace);
                assert_eq!(editor.file_picker().unwrap().query, "deep");
                type_text(&mut editor, "👩‍💻");
                editor.handle(Input::Backspace);
                assert_eq!(editor.file_picker().unwrap().query, "deep");
                let before = editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .map(|row| row.path.to_owned())
                    .collect::<Vec<_>>();
                let selected_before = editor.file_picker().unwrap().selected;
                editor.handle(Input::Escape);
                let picker = editor.file_picker().unwrap();
                assert!(picker.focused);
                assert!(!picker.searching);
                assert_eq!(picker.query, "deep");
                assert_eq!(picker.selected, selected_before);
                assert_eq!(
                    picker
                        .entries()
                        .map(|row| row.path.to_owned())
                        .collect::<Vec<_>>(),
                    before
                );
                editor.handle(Input::Escape);
                match presentation {
                    FilePresentation::Floating => assert!(editor.file_picker().is_none()),
                    FilePresentation::Docked => assert!(!editor.file_picker().unwrap().focused),
                }
                assert_eq!(editor.mode(), mode);
                assert_eq!(editor.command_line, "underlying");
                assert_eq!(editor.active.targets, targets);
                assert_eq!(editor.context().text, text);
                assert_eq!(editor.active.undo.len(), undo);
            }
        }
    }

    #[test]
    fn tree_binding_precedence_is_modal_and_navigation_preferences_are_atomic() {
        let directory = Directory::new();
        fs::create_dir(directory.path("folder")).unwrap();
        fs::write(directory.path("folder/a.txt"), "a").unwrap();
        fs::write(directory.path("folder/b.txt"), "b").unwrap();
        fs::write(directory.path("z.txt"), "z").unwrap();
        let mut editor = project_editor(&directory);
        editor
            .bind("selection", "x", Some("core.down".into()))
            .unwrap();
        editor.bind("tree", "x", Some("core.right".into())).unwrap();
        editor
            .bind("tree", "ctrl+j", Some("core.left".into()))
            .unwrap();
        editor.bind("tree", "ctrl+k", None).unwrap();
        type_text(&mut editor, "3 b");
        let pending = editor.leader_pending().unwrap().to_owned();
        let hint = editor.tree_navigation_hint.clone();
        for (key, target) in [
            ("x", Some("core.delete")),
            ("x", Some("core.palette")),
            ("x", Some("w")),
            ("leader x", Some("core.right")),
            ("x y", Some("core.left")),
            ("alt+x", None),
        ] {
            assert!(editor.bind("tree", key, target.map(str::to_owned)).is_err());
            assert_eq!(editor.tree_navigation_hint, hint);
            assert_eq!(editor.count(), Some(3));
            assert_eq!(editor.leader_pending(), Some(pending.as_str()));
        }
        editor.open_file_picker(FilePresentation::Docked);
        editor.handle(Input::Char('x'));
        assert_eq!(editor.file_picker().unwrap().selected, 0);
        assert!(
            editor
                .file_picker()
                .unwrap()
                .entries()
                .next()
                .unwrap()
                .expanded
        );
        editor.handle(Input::Char('x'));
        assert_eq!(editor.file_picker().unwrap().selected, 1);
        editor.handle(Input::Ctrl('k'));
        assert_eq!(editor.file_picker().unwrap().selected, 1);
        editor.handle(Input::Ctrl('j'));
        assert_eq!(editor.file_picker().unwrap().selected, 0);
        editor.handle(Input::Char('i'));
        editor.handle(Input::Char('x'));
        assert_eq!(editor.file_picker().unwrap().selected, 1);
        assert_eq!(editor.file_picker().unwrap().query, "");
        editor.handle(Input::Ctrl('j'));
        assert_eq!(editor.file_picker().unwrap().selected, 0);
        editor.handle(Input::Ctrl('h'));
        assert_eq!(editor.file_picker().unwrap().selected, 0);
        editor.handle(Input::Ctrl('t'));
        assert_eq!(editor.file_picker().unwrap().view, FileView::List);
        assert_eq!(
            editor.file_navigation_hint(),
            editor.selection_navigation_hint()
        );
        editor.handle(Input::Char('x'));
        assert_eq!(editor.file_picker().unwrap().selected, 1);
        editor.handle(Input::Ctrl('w'));
        editor.handle(Input::Char('x'));
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Ctrl('p'));
        let selected = editor.palette().unwrap().selected;
        editor.handle(Input::Char('x'));
        assert_eq!(editor.palette().unwrap().selected, selected + 1);
        editor.handle(Input::Ctrl('h'));
        assert_eq!(editor.palette().unwrap().query, "");
    }

    #[test]
    fn ctrl_h_is_not_backspace_unless_explicitly_bound() {
        assert_eq!(parse_key("CTRL+H").unwrap(), Input::Ctrl('h'));
        assert_eq!(parse_key("backspace").unwrap(), Input::Backspace);
        for mode in [
            Mode::Normal,
            Mode::Visual,
            Mode::Insert,
            Mode::Command,
            Mode::Search,
        ] {
            let mut editor = editor();
            editor.apply(vec![Effect::Replace("abc".into())]).unwrap();
            set_carets(&mut editor, &[(0, 2)], 0);
            editor.active.mode = mode;
            editor.command_line = "query".into();
            let targets = editor.active.targets.clone();
            let undo = editor.active.undo.len();
            editor.handle(Input::Ctrl('h'));
            assert_eq!(editor.context().text, "abc");
            assert_eq!(editor.active.targets, targets);
            assert_eq!(editor.active.undo.len(), undo);
            assert_eq!(editor.command_line, "query");
            assert_eq!(editor.mode(), mode);
        }
        let mut editor = editor();
        type_text(&mut editor, "iabc");
        editor.handle(Input::Ctrl('h'));
        assert_eq!(editor.context().text, "abc");
        editor
            .bind("insert", "ctrl+h", Some("core.backspace".into()))
            .unwrap();
        editor.handle(Input::Ctrl('h'));
        assert_eq!(editor.context().text, "ab");
        editor.bind("insert", "ctrl+h", None).unwrap();
        editor.handle(Input::Ctrl('h'));
        assert_eq!(editor.context().text, "ab");
        editor.handle(Input::Backspace);
        assert_eq!(editor.context().text, "a");

        let directory = Directory::new();
        fs::write(directory.path("a.txt"), "text").unwrap();
        let mut editor = project_editor(&directory);
        editor.open_file_picker(FilePresentation::Floating);
        type_text(&mut editor, "a");
        editor.handle(Input::Ctrl('h'));
        assert_eq!(editor.file_picker().unwrap().query, "a");
        editor.handle(Input::Backspace);
        assert_eq!(editor.file_picker().unwrap().query, "");
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "core");
        editor.handle(Input::Ctrl('h'));
        assert_eq!(editor.palette().unwrap().query, "core");
        editor.handle(Input::Backspace);
        assert_eq!(editor.palette().unwrap().query, "cor");
    }

    #[test]
    fn tree_leaf_search_opens_direct_match_and_directory_search_enters_browse() {
        let directory = Directory::new();
        fs::create_dir_all(directory.path("src/module")).unwrap();
        fs::write(directory.path("src/module/needle.txt"), "needle").unwrap();
        fs::write(directory.path("src/sibling.txt"), "sibling").unwrap();
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            let mut editor = project_editor(&directory);
            editor.set_file_picker_view("tree").unwrap();
            editor.open_file_picker(presentation);
            if presentation == FilePresentation::Docked {
                editor.handle(Input::Char('i'));
            }
            type_text(&mut editor, "needle.txt");
            let picker = editor.file_picker().unwrap();
            assert_eq!(
                picker.entries().nth(picker.selected).unwrap().path,
                Path::new("src/module/needle.txt")
            );
            editor.handle(Input::Enter);
            assert_eq!(editor.context().text, "needle");
            assert_eq!(
                editor.path(),
                Some(directory.path("src/module/needle.txt").as_path())
            );
            editor.open_file_picker(presentation);
            editor.handle(Input::Ctrl('w'));
            editor.open_file_picker(presentation);
            if presentation == FilePresentation::Docked {
                editor.handle(Input::Char('i'));
            }
            type_text(&mut editor, "module");
            assert!(
                editor
                    .file_picker()
                    .unwrap()
                    .entries()
                    .nth(editor.file_picker().unwrap().selected)
                    .unwrap()
                    .is_dir
            );
            let id = editor.buffer_id();
            editor.handle(Input::Enter);
            let picker = editor.file_picker().unwrap();
            assert_eq!(editor.buffer_id(), id);
            assert!(!picker.searching);
            assert_eq!(picker.query, "module");
            let selected = picker.entries().nth(picker.selected).unwrap();
            assert_eq!(selected.path, Path::new("src/module"));
            assert!(!selected.expanded);
            assert!(
                !picker
                    .entries()
                    .any(|row| row.path == Path::new("src/module/needle.txt"))
            );
            editor.handle(Input::Enter);
            let picker = editor.file_picker().unwrap();
            assert_eq!(picker.query, "module");
            assert!(picker.entries().nth(picker.selected).unwrap().expanded);
            assert!(
                picker
                    .entries()
                    .any(|row| row.path == Path::new("src/module/needle.txt"))
            );
            assert_eq!(editor.buffer_count(), 2);
        }
    }

    #[cfg(unix)]
    #[test]
    fn tree_search_opens_raw_nested_paths_and_deduplicates_dirty_buffers() {
        let directory = Directory::new();
        fs::create_dir_all(directory.path("dir\n/deep")).unwrap();
        let a = directory.path("dir\n/deep/same\n.txt");
        let b = directory.path("dir\n/deep/same\t.txt");
        fs::write(&a, "first").unwrap();
        fs::write(&b, "second").unwrap();
        for presentation in [FilePresentation::Floating, FilePresentation::Docked] {
            fs::write(&a, "first").unwrap();
            let mut editor = project_editor(&directory);
            editor.set_file_picker_view("tree").unwrap();
            editor.edit_buffer(a.clone(), false).unwrap();
            editor
                .apply(vec![Effect::Replace("dirty first".into())])
                .unwrap();
            type_text(&mut editor, "vl");
            let selections = editor.selections();
            let id = editor.buffer_id();
            editor.edit_buffer(b.clone(), false).unwrap();
            fs::write(&a, b"\xff").unwrap();
            editor.open_file_picker(presentation);
            if presentation == FilePresentation::Docked {
                editor.handle(Input::Char('i'));
            }
            type_text(&mut editor, "same");
            let picker = editor.file_picker.as_mut().unwrap();
            let labels = picker
                .entries()
                .filter(|row| !row.is_dir)
                .map(|row| row.label)
                .collect::<Vec<_>>();
            assert_eq!(labels.len(), 2);
            assert_eq!(labels[0], labels[1]);
            assert!(
                picker
                    .entries()
                    .all(|row| !row.label.chars().any(char::is_control))
            );
            let selected = picker
                .entries()
                .position(|row| picker.root.join(row.path) == a)
                .unwrap();
            picker.selected = selected;
            editor.handle(Input::Enter);
            assert_eq!(editor.path(), Some(a.as_path()));
            assert_eq!(editor.buffer_id(), id);
            assert_eq!(editor.buffer_count(), 3);
            assert_eq!(editor.context().text, "dirty first");
            assert!(editor.dirty());
            assert_eq!(editor.mode(), Mode::Visual);
            assert_eq!(editor.selections(), selections);
            match presentation {
                FilePresentation::Floating => assert!(editor.file_picker().is_none()),
                FilePresentation::Docked => {
                    assert!(!editor.file_picker().unwrap().focused);
                    assert!(editor.file_picker().unwrap().searching);
                    assert_eq!(editor.file_picker().unwrap().query, "same");
                }
            }
        }
    }

    #[test]
    fn default_leader_routes_save_switch_list_delete_and_open_palette() {
        let directory = Directory::new();
        let path = directory.path("first");
        let mut editor = Editor::open(Some(path.clone()), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        type_text(&mut editor, "ihello");
        editor.handle(Input::Escape);
        type_text(&mut editor, " w");
        assert_eq!(fs::read_to_string(&path).unwrap(), "hello");
        assert!(!editor.dirty());
        editor.execute(&format!("edit {}", directory.path("second").display()));
        type_text(&mut editor, " b");
        assert_eq!(editor.leader_pending(), Some("Space b"));
        editor.handle(Input::Char('n'));
        assert_eq!(editor.buffer_id(), 1);
        assert_eq!(editor.leader_pending(), None);
        type_text(&mut editor, " bp");
        assert_eq!(editor.buffer_id(), 2);
        type_text(&mut editor, " bl");
        assert!(editor.message().contains("first"));
        assert!(editor.message().contains("second"));
        type_text(&mut editor, " bd");
        assert!(!editor.has_buffer(2));
        assert_eq!(editor.buffer_id(), 1);
        for mode in [Mode::Normal, Mode::Visual] {
            if mode == Mode::Visual {
                editor.handle(Input::Char('v'));
            }
            editor.handle(Input::Char(' '));
            assert_eq!(editor.leader_pending(), Some("Space"));
            editor.handle(Input::Char(' '));
            assert!(editor.palette().is_some());
            assert_eq!(editor.mode(), mode);
            assert_eq!(editor.leader_pending(), None);
            editor.handle(Input::Escape);
        }
    }

    #[test]
    fn nested_leader_dispatches_plugin_once_with_count_and_multiple_carets() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("aa\nbb".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.register(plugin("fixture", &["greet"])).unwrap();
        editor
            .bind("normal", "LeAdEr g ctrl+r 7 shift+i", Some("greet".into()))
            .unwrap();
        type_text(&mut editor, "8 g");
        editor.handle(Input::Ctrl('R'));
        assert_eq!(editor.leader_pending(), Some("Space g Ctrl+r"));
        editor.handle(Input::Char('7'));
        assert_eq!(editor.count(), Some(8));
        assert_eq!(editor.leader_pending(), Some("Space g Ctrl+r 7"));
        assert_eq!(
            editor.handle(Input::Char('I')),
            Some(Invocation {
                plugin: "fixture".into(),
                command: "greet".into(),
                args: String::new(),
            })
        );
        assert_eq!(editor.selection_count(), 2);
        assert_eq!(editor.context().text, "aa\nbb");
        assert_eq!(editor.count(), None);
        assert_eq!(editor.leader_pending(), None);
        editor.handle(Input::Ctrl('p'));
        assert_eq!(
            palette_entry(&editor, "greet").bindings,
            vec!["Space g Ctrl+r 7 I"]
        );
    }

    #[test]
    fn custom_leader_is_symbolic_and_ordinary_trigger_bindings_preempt_by_mode() {
        let mut editor = editor();
        type_text(&mut editor, "3 b");
        editor.set_leader("comma").unwrap();
        assert_eq!(editor.leader_pending(), None);
        assert_eq!(editor.count(), None);
        editor.handle(Input::Ctrl('p'));
        assert_eq!(palette_entry(&editor, "bnext").bindings, vec![", b n"]);
        editor
            .bind("normal", ",", Some("core.command".into()))
            .unwrap();
        assert!(palette_entry(&editor, "bnext").bindings.is_empty());
        editor.set_leader(",").unwrap();
        editor.handle(Input::Escape);
        editor.handle(Input::Char(','));
        assert_eq!(editor.mode(), Mode::Command);
        assert_eq!(editor.leader_pending(), None);
        editor.handle(Input::Escape);
        editor.handle(Input::Char('v'));
        type_text(&mut editor, ", ");
        assert!(editor.palette().is_some());
        assert_eq!(editor.mode(), Mode::Visual);
        editor.handle(Input::Escape);
        editor.handle(Input::Escape);
        editor.bind("normal", ",", None).unwrap();
        type_text(&mut editor, "4,");
        assert_eq!(editor.count(), None);
        assert_eq!(editor.leader_pending(), None);
        editor.set_leader("\\").unwrap();
        type_text(&mut editor, "\\b");
        assert_eq!(editor.leader_pending(), Some("\\ b"));
        editor.handle(Input::Char('n'));
        assert_eq!(editor.leader_pending(), None);
        editor.handle(Input::Ctrl('p'));
        assert_eq!(palette_entry(&editor, "bnext").bindings, vec!["\\ b n"]);
    }

    #[test]
    fn leader_prefix_conflicts_and_invalid_replacements_are_atomic() {
        let mut editor = editor();
        assert!(editor.bind("normal", "leader b", None).is_err());
        editor
            .bind("normal", "leader z", Some("core.down".into()))
            .unwrap();
        assert!(editor.bind("normal", "leader z n", None).is_err());
        assert!(
            editor
                .bind("normal", "leader z", Some("missing".into()))
                .is_err()
        );
        editor
            .apply(vec![Effect::Replace("a\nb\nc".into())])
            .unwrap();
        type_text(&mut editor, " z");
        assert_eq!(editor.cursor().row, 1);
        editor.bind("normal", "leader z", None).unwrap();
        assert!(
            editor
                .bind("normal", "leader z n", Some("core.down".into()))
                .is_err()
        );
        type_text(&mut editor, "2 z");
        assert_eq!(editor.cursor().row, 1);
        assert_eq!(editor.count(), None);
        editor.bind("normal", "leader g n", None).unwrap();
        assert!(editor.bind("normal", "leader g", None).is_err());
        for key in ["leader", "leader ctrl+", "leader b ctrl++r", "leader <Esc>"] {
            assert!(editor.bind("normal", key, None).is_err(), "{key}");
        }
        editor
            .bind("normal", "  LEADER\tz  ", Some("core.up".into()))
            .unwrap();
        type_text(&mut editor, " z");
        assert_eq!(editor.cursor().row, 0);
        assert!(
            editor
                .leader_bindings
                .get(&Mode::Normal)
                .unwrap()
                .contains_key(&vec![Input::Char('b'), Input::Char('n')])
        );
    }

    #[test]
    fn leader_validation_preserves_choice_and_reuses_action_mode_eligibility() {
        let mut editor = editor();
        editor.register(plugin("fixture", &["greet"])).unwrap();
        for mode in ["insert", "command", "search", "unknown"] {
            assert!(editor.bind(mode, "leader z", None).is_err(), "{mode}");
        }
        assert!(
            editor
                .bind("visual", "leader z", Some("core.insert".into()))
                .is_err()
        );
        assert!(
            editor
                .bind("visual", "leader z", Some("greet".into()))
                .is_err()
        );
        editor
            .bind("visual", "leader z", Some("core.right".into()))
            .unwrap();
        editor.bind("normal", "comma", None).unwrap();
        editor.bind("visual", "\\", None).unwrap();
        for key in [
            "", "esc", "ESC", "0", "9", "i", "ctrl+p", ",", "\\", "leader b", "alt+j",
        ] {
            assert!(editor.set_leader(key).is_err(), "{key}");
            assert_eq!(editor.leader, Input::Char(' '));
        }
        editor.bind("insert", "界", None).unwrap();
        editor.set_leader("界").unwrap();
        editor.handle(Input::Char('界'));
        assert_eq!(editor.leader_pending(), Some("界"));
        editor.handle(Input::Escape);
        editor.set_leader("space").unwrap();
        editor.bind("normal", "space", None).unwrap();
        editor.set_leader("SPACE").unwrap();
        assert_eq!(editor.leader, Input::Char(' '));
    }

    #[test]
    fn leader_escape_unknown_and_paste_cancel_count_without_changing_selections() {
        for visual in [false, true] {
            let mut editor = editor();
            editor
                .apply(vec![Effect::Replace("abcd\nabcd".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 1), (1, 1)], 1);
            if visual {
                editor
                    .bind("visual", "leader b n", Some("core.down".into()))
                    .unwrap();
                type_text(&mut editor, "vl");
            }
            let mode = editor.mode();
            let carets = editor.carets();
            let selections = editor.selections();
            for prefix in [" b", "3 b"] {
                type_text(&mut editor, prefix);
                assert_eq!(editor.leader_pending(), Some("Space b"));
                editor.handle(Input::Escape);
                assert_eq!(editor.mode(), mode);
                assert_eq!(editor.carets(), carets);
                assert_eq!(editor.selections(), selections);
                assert_eq!(editor.count(), None);
                assert_eq!(editor.leader_pending(), None);
            }
            type_text(&mut editor, "4 b");
            editor.handle(Input::Char('x'));
            assert!(
                editor
                    .message()
                    .contains("Unknown leader sequence: Space b x")
            );
            assert_eq!(editor.context().text, "abcd\nabcd");
            assert_eq!(editor.carets(), carets);
            assert_eq!(editor.selections(), selections);
            assert_eq!(editor.mode(), mode);
            assert_eq!(editor.count(), None);
            assert_eq!(editor.leader_pending(), None);
            type_text(&mut editor, "5 b");
            editor.handle(Input::Paste("n".into()));
            assert_eq!(editor.context().text, "abcd\nabcd");
            assert_eq!(editor.carets(), carets);
            assert_eq!(editor.count(), None);
            assert_eq!(editor.leader_pending(), None);
            editor.handle(Input::Escape);
            assert_eq!(editor.mode(), Mode::Normal);
            assert_eq!(editor.selection_count(), if visual { 2 } else { 1 });
        }
    }

    #[test]
    fn leader_digit_suffix_uses_pending_count_for_remapped_motion_not_new_count() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace(["abcd"; 12].join("\n"))])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor
            .bind("normal", "leader g 0 2", Some("core.down".into()))
            .unwrap();
        type_text(&mut editor, "3 g0");
        assert_eq!(editor.count(), Some(3));
        assert_eq!(editor.leader_pending(), Some("Space g 0"));
        editor.handle(Input::Char('2'));
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 3, column: 0 }, Cursor { row: 4, column: 0 }]
        );
        assert_eq!(editor.count(), None);
        assert_eq!(editor.leader_pending(), None);
        editor
            .bind("visual", "leader 7", Some("core.right".into()))
            .unwrap();
        editor.handle(Input::Char('v'));
        type_text(&mut editor, "2 7");
        assert_eq!(editor.cursor(), Cursor { row: 4, column: 2 });
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.selection_count(), 2);
        assert_eq!(editor.count(), None);
    }

    #[test]
    fn leader_keys_are_literal_in_insert_prompts_and_palette_queries() {
        for (key, ch) in [("space", ' '), ("comma", ',')] {
            for mode_key in ['i', ':', '/'] {
                let mut editor = editor();
                editor.set_leader(key).unwrap();
                editor.handle(Input::Char(mode_key));
                let text = format!("{ch}b n{ch}");
                type_text(&mut editor, &text);
                assert_eq!(editor.leader_pending(), None);
                assert_eq!(editor.count(), None);
                if mode_key == 'i' {
                    assert_eq!(editor.context().text, text);
                    assert_eq!(editor.mode(), Mode::Insert);
                } else {
                    assert_eq!(editor.command_line(), text);
                    assert_eq!(
                        editor.mode(),
                        if mode_key == ':' {
                            Mode::Command
                        } else {
                            Mode::Search
                        }
                    );
                }
                let mode = editor.mode();
                editor.handle(Input::Ctrl('p'));
                type_text(&mut editor, "core word next ");
                assert_eq!(editor.palette().unwrap().query, "core word next ");
                assert_eq!(editor.leader_pending(), None);
                editor.handle(Input::Escape);
                assert_eq!(editor.mode(), mode);
            }
        }
    }

    #[test]
    fn leader_routes_retire_with_plugins_and_binding_changes_cancel_pending() {
        let mut editor = editor();
        editor.register(plugin("fixture", &["greet"])).unwrap();
        editor.bind("normal", "g", Some("greet".into())).unwrap();
        editor
            .bind("normal", "leader g n", Some("greet".into()))
            .unwrap();
        type_text(&mut editor, "3 g");
        editor
            .bind("normal", "leader g n", Some("core.down".into()))
            .unwrap();
        assert_eq!(editor.leader_pending(), None);
        assert_eq!(editor.count(), None);
        type_text(&mut editor, "2 g");
        editor.bind("normal", "z", None).unwrap();
        assert_eq!(editor.leader_pending(), None);
        assert_eq!(editor.count(), None);
        editor
            .bind("normal", "leader g n", Some("greet".into()))
            .unwrap();
        type_text(&mut editor, "4 g");
        editor.disable_plugin("fixture", "retired");
        assert_eq!(editor.leader_pending(), None);
        assert_eq!(editor.count(), None);
        assert_eq!(editor.handle(Input::Char('g')), None);
        type_text(&mut editor, " g");
        assert_eq!(editor.leader_pending(), None);
        assert!(editor.message().contains("Unknown leader sequence"));
        assert!(
            editor
                .bind("normal", "leader g n", Some("greet".into()))
                .is_err()
        );
        editor.handle(Input::Ctrl('p'));
        assert!(
            !editor
                .palette()
                .unwrap()
                .entries
                .iter()
                .any(|entry| entry.name == "greet")
        );
    }

    #[test]
    fn pending_leader_never_survives_external_commands_or_buffer_transitions() {
        let directory = Directory::new();
        let mut editor = editor();
        editor.apply(vec![Effect::Replace("abcd".into())]).unwrap();
        editor.execute(&format!("edit {}", directory.path("other").display()));
        editor.set_leader(",").unwrap();
        for command in [
            "buffer 1",
            "buffer 1",
            "bnext",
            "bprev",
            "buffers",
            "buffer 999",
        ] {
            type_text(&mut editor, "3,b");
            assert_eq!(editor.leader_pending(), Some(", b"));
            editor.execute(command);
            assert_eq!(editor.leader_pending(), None);
            assert_eq!(editor.count(), None);
            editor.handle(Input::Char(','));
            assert_eq!(editor.leader_pending(), Some(","));
            editor.handle(Input::Escape);
        }
        editor.execute("buffer 1");
        type_text(&mut editor, "vl");
        let selections = editor.selections();
        type_text(&mut editor, "2,");
        editor.execute("buffer 2");
        editor.execute("buffer 1");
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.selections(), selections);
        assert_eq!(editor.leader_pending(), None);
        assert_eq!(editor.count(), None);
        editor.handle(Input::Char(','));
        editor
            .apply(vec![Effect::Replace("replacement".into())])
            .unwrap();
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.leader_pending(), None);
        editor
            .bind("normal", "leader i", Some("core.insert".into()))
            .unwrap();
        type_text(&mut editor, ",i");
        assert_eq!(editor.mode(), Mode::Insert);
        assert_eq!(editor.leader_pending(), None);
    }

    #[test]
    fn counted_cursor_motions_apply_to_all_carets_and_clamp_through_short_rows() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace(
                "e\u{301}界👩‍🚀z\n\nlong\nfour\naa\nbbbb\ncccc".into(),
            )])
            .unwrap();
        set_carets(&mut editor, &[(0, 3), (4, 1)], 1);
        let undo = editor.active.undo.len();
        type_text(&mut editor, "2j");
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 2, column: 0 }, Cursor { row: 6, column: 1 }]
        );
        assert_eq!(editor.cursor(), Cursor { row: 6, column: 1 });
        type_text(&mut editor, "100k");
        assert_eq!(editor.carets(), vec![Cursor::default()]);
        type_text(&mut editor, "2l");
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 2 });
        type_text(&mut editor, "9h");
        assert_eq!(editor.cursor(), Cursor::default());
        type_text(&mut editor, "999999999999999999999999999999999999");
        assert_eq!(editor.count(), Some(usize::MAX));
        editor.handle(Input::Down);
        assert_eq!(editor.cursor(), Cursor { row: 6, column: 0 });
        assert_eq!(editor.count(), None);
        assert_eq!(editor.active.undo.len(), undo);
        assert_eq!(
            editor.lines(),
            &["e\u{301}界👩‍🚀z", "", "long", "four", "aa", "bbbb", "cccc"]
        );
    }

    #[test]
    fn counted_words_match_repeated_unicode_motions_without_intermediate_selection_merging() {
        let text = "foo_bar...baz qux\n\n   \n界e\u{301}_2 👩‍🚀!! tail\n";
        for key in ['w', 'b', 'e', 'W', 'B', 'E'] {
            for positions in [&[(0, 0), (3, 0)][..], &[(0, 8), (3, 8)][..]] {
                let mut counted = editor();
                counted.apply(vec![Effect::Replace(text.into())]).unwrap();
                set_carets(&mut counted, positions, 1);
                let mut repeated = editor();
                repeated.apply(vec![Effect::Replace(text.into())]).unwrap();
                set_carets(&mut repeated, positions, 1);
                type_text(&mut counted, &format!("3{key}"));
                for _ in 0..3 {
                    repeated.handle(Input::Char(key));
                }
                assert_eq!(counted.carets(), repeated.carets(), "{key} {positions:?}");
                assert_eq!(counted.cursor(), repeated.cursor(), "{key} {positions:?}");
            }
        }
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace(
                "one two three\none longer third".into(),
            )])
            .unwrap();
        editor.handle(Input::Ctrl('e'));
        editor.handle(Input::Char('v'));
        type_text(&mut editor, "2e");
        assert_eq!(
            editor.selections(),
            vec![
                Selection {
                    start: Cursor { row: 0, column: 0 },
                    end: Cursor { row: 0, column: 7 }
                },
                Selection {
                    start: Cursor { row: 1, column: 0 },
                    end: Cursor { row: 1, column: 10 }
                },
            ]
        );
        editor.handle(Input::Char('c'));
        type_text(&mut editor, "item");
        editor.handle(Input::Escape);
        assert_eq!(editor.lines(), &["item three", "item third"]);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.lines(), &["one two three", "one longer third"]);
        assert_eq!(editor.selection_count(), 2);
        type_text(&mut editor, &format!("{}w", usize::MAX));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 15 });
    }

    #[test]
    fn count_digits_zero_and_escape_preserve_modal_editing_and_custom_bindings() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace(["abc"; 12].join("\n"))])
            .unwrap();
        type_text(&mut editor, "10j");
        assert_eq!(editor.cursor(), Cursor { row: 10, column: 0 });
        editor.handle(Input::End);
        type_text(&mut editor, "0");
        assert_eq!(editor.cursor().column, 0);
        editor.handle(Input::Ctrl('k'));
        editor.handle(Input::Char('v'));
        let selected = editor.selections();
        type_text(&mut editor, "4");
        editor.handle(Input::Escape);
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.selections(), selected);
        assert_eq!(editor.count(), None);
        editor.handle(Input::Escape);
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.selection_count(), 2);
        type_text(&mut editor, "3g");
        assert_eq!(editor.count(), None);
        editor.bind("normal", "2", None).unwrap();
        type_text(&mut editor, "42");
        assert_eq!(editor.count(), None);
        editor
            .bind("normal", "3", Some("core.down".into()))
            .unwrap();
        type_text(&mut editor, "3");
        assert_eq!(editor.cursor().row, 10);
        assert_eq!(editor.count(), None);
        type_text(&mut editor, "5i12");
        editor.handle(Input::Escape);
        assert_eq!(editor.lines()[10], "12abc");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.lines()[10], "abc");
        editor.handle(Input::Char('/'));
        type_text(&mut editor, "123");
        assert_eq!(editor.command_line(), "123");
        assert_eq!(editor.count(), None);
    }

    #[test]
    fn counted_search_wraps_per_target_and_unrelated_actions_execute_once() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("cat cat cat\ncat cat cat".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        submit_search(&mut editor, "cat");
        type_text(&mut editor, "2n");
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 0 }, Cursor { row: 1, column: 0 }]
        );
        type_text(&mut editor, "2N");
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 4 }, Cursor { row: 1, column: 4 }]
        );
        editor.register(plugin("once", &["once"])).unwrap();
        editor.bind("normal", "g", Some("once".into())).unwrap();
        type_text(&mut editor, "8");
        let invocation = editor.handle(Input::Char('g')).unwrap();
        assert_eq!(invocation.command, "once");
        assert_eq!(editor.count(), None);
        type_text(&mut editor, "7");
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "core.word_next");
        editor.handle(Input::Enter);
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 8 }, Cursor { row: 1, column: 8 }]
        );
        assert_eq!(editor.count(), None);
        type_text(&mut editor, "9");
        editor.handle(Input::Paste("ignored".into()));
        editor.handle(Input::Char('h'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 7 });
    }
    fn submit_search(editor: &mut Editor, query: &str) {
        editor.handle(Input::Char('/'));
        type_text(editor, query);
        editor.handle(Input::Enter);
    }
    fn plugin(name: &str, commands: &[&str]) -> Feature {
        Feature {
            name: name.into(),
            required_capabilities: vec!["text".into()],
            commands: commands.iter().map(|name| (*name).into()).collect(),
            core: false,
        }
    }

    fn set_carets(editor: &mut Editor, positions: &[(usize, usize)], primary: usize) {
        editor.active.mode = Mode::Normal;
        editor.active.visual_motions = None;
        editor.active.targets = positions
            .iter()
            .map(|&(row, column)| Target::caret(Cursor { row, column }))
            .collect();
        editor.active.primary = primary;
        editor.normalize_targets();
    }

    fn set_ranges(editor: &mut Editor, ranges: &[(Cursor, Cursor)], primary: usize) {
        editor.active.mode = Mode::Visual;
        editor.active.visual_motions = None;
        editor.active.targets = ranges
            .iter()
            .map(|&(start, end)| editor.range_target(Selection { start, end }, true))
            .collect();
        editor.active.primary = primary;
        editor.normalize_targets();
    }

    #[test]
    fn repeat_visual_word_change_resolves_fresh_words_for_every_caret_and_ignores_remaps() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("foo\nlonger".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        type_text(&mut editor, "vecitem");
        editor.handle(Input::Escape);
        editor
            .bind("visual", "e", Some("core.right".into()))
            .unwrap();
        editor
            .apply(vec![Effect::Replace("tiny\nextraordinary".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        let undo = editor.active.undo.len();
        type_text(&mut editor, "9.");
        assert_eq!(editor.context().text, "item\nitem");
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.selection_count(), 2);
        assert_eq!(editor.cursor().row, 1);
        assert_eq!(editor.count(), None);
        assert_eq!(editor.clipboard, vec!["tiny", "extraordinary"]);
        assert_eq!(editor.active.undo.len(), undo + 1);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "tiny\nextraordinary");
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 0 }, Cursor { row: 1, column: 0 }]
        );
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "item\nitem");
        editor.handle(Input::Char('u'));
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "item\nitem");
    }

    #[test]
    fn repeat_visual_current_ranges_supersede_unequal_recorded_spans_and_cardinality() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("abcd\nlonger".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[
                (Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 2 }),
                (Cursor { row: 1, column: 0 }, Cursor { row: 1, column: 5 }),
            ],
            1,
        );
        type_text(&mut editor, "cQ");
        editor.handle(Input::Escape);
        editor
            .apply(vec![Effect::Replace("alpha beta\nsecond\nthird".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[
                (Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 10 }),
                (Cursor { row: 1, column: 0 }, Cursor { row: 1, column: 6 }),
                (Cursor { row: 2, column: 0 }, Cursor { row: 2, column: 5 }),
            ],
            2,
        );
        let undo = editor.active.undo.len();
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Q\nQ\nQ");
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.selection_count(), 3);
        assert_eq!(editor.cursor().row, 2);
        assert_eq!(editor.active.undo.len(), undo + 1);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "alpha beta\nsecond\nthird");
    }

    #[test]
    fn repeat_cut_retargets_fresh_unequal_words_without_recreating_cloned_carets() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("cat\nlongword".into())])
            .unwrap();
        type_text(&mut editor, "ve");
        editor.handle(Input::Ctrl('e'));
        editor.handle(Input::Char('d'));
        editor
            .apply(vec![Effect::Replace("small\nhugeword\nlast".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 2);
        // Cloning invalidated the selector; both recorded spans have length three.
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "ll\neword\nt");
        assert_eq!(editor.selection_count(), 3);
        editor
            .apply(vec![Effect::Replace("cat\nlongword".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        type_text(&mut editor, "ved");
        editor
            .apply(vec![Effect::Replace("tiny\nenormous".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "\n");
        assert_eq!(editor.clipboard, vec!["tiny", "enormous"]);
    }

    #[test]
    fn repeat_relative_spans_count_graphemes_and_newlines_and_keep_zero_spans_empty() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("a界\n👩‍🚀x".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[(Cursor { row: 0, column: 1 }, Cursor { row: 1, column: 1 })],
            0,
        );
        editor.handle(Input::Char('d'));
        editor
            .apply(vec![Effect::Replace("e\u{301}Z\n\n👨‍💻tail".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "\n👨‍💻tail");
        assert_eq!(editor.clipboard, vec!["e\u{301}Z\n"]);
        editor.apply(vec![Effect::Replace("".into())]).unwrap();
        set_ranges(&mut editor, &[(Cursor::default(), Cursor::default())], 0);
        type_text(&mut editor, "cQ");
        editor.handle(Input::Escape);
        editor.apply(vec![Effect::Replace("abc".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Qabc");
    }

    #[test]
    fn repeat_unequal_span_distribution_refuses_atomically_and_recipe_survives() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("abcd\nlonger".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[
                (Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 2 }),
                (Cursor { row: 1, column: 0 }, Cursor { row: 1, column: 3 }),
            ],
            1,
        );
        editor.handle(Input::Char('d'));
        editor
            .apply(vec![Effect::Replace("1234\n56789".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 1)], 0);
        let undo = editor.active.undo.len();
        let redo = editor.active.redo.len();
        let clipboard = editor.clipboard.clone();
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "1234\n56789");
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 1 });
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.active.undo.len(), undo);
        assert_eq!(editor.active.redo.len(), redo);
        assert_eq!(editor.clipboard, clipboard);
        assert!(editor.message().contains("count"));
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "34\n89");
    }

    #[test]
    fn repeat_insert_placements_recalculate_for_current_multi_caret_lines() {
        for key in ['i', 'I', 'a', 'A', 'o', 'O'] {
            let mut recorded = editor();
            recorded
                .apply(vec![Effect::Replace("short".into())])
                .unwrap();
            recorded.handle(Input::Char(key));
            type_text(&mut recorded, "X\nY");
            recorded.handle(Input::Escape);
            let text = "  alpha\n\tbeta\nz";
            recorded.apply(vec![Effect::Replace(text.into())]).unwrap();
            set_carets(&mut recorded, &[(0, 2), (1, 1), (2, 0)], 1);
            let mut expected = editor();
            expected.apply(vec![Effect::Replace(text.into())]).unwrap();
            set_carets(&mut expected, &[(0, 2), (1, 1), (2, 0)], 1);
            expected.handle(Input::Char(key));
            type_text(&mut expected, "X\nY");
            expected.handle(Input::Escape);
            let undo = recorded.active.undo.len();
            recorded.handle(Input::Char('.'));
            assert_eq!(recorded.context().text, expected.context().text, "{key}");
            assert_eq!(recorded.carets(), expected.carets(), "{key}");
            assert_eq!(recorded.cursor(), expected.cursor(), "{key}");
            assert_eq!(recorded.mode(), Mode::Normal);
            assert_eq!(recorded.active.undo.len(), undo + 1);
            recorded.handle(Input::Char('u'));
            assert_eq!(recorded.context().text, text, "{key}");
            assert_eq!(recorded.selection_count(), 3);
        }
    }

    #[test]
    fn repeat_visual_line_insert_uses_current_carets_without_rebuilding_old_row_targets() {
        for (key, expected) in [('I', " !alpha\n !beta"), ('A', " alpha!\n beta!")] {
            let mut editor = editor();
            editor
                .apply(vec![Effect::Replace("a\nb\nc".into())])
                .unwrap();
            type_text(&mut editor, "v2j");
            editor.handle(Input::Char(key));
            type_text(&mut editor, "!");
            editor.handle(Input::Escape);
            assert_eq!(editor.selection_count(), 3);
            editor
                .apply(vec![Effect::Replace(" alpha\n beta".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 2), (1, 2)], 1);
            editor.handle(Input::Char('.'));
            assert_eq!(editor.context().text, expected);
            assert_eq!(editor.selection_count(), 2);
            assert_eq!(editor.cursor().row, 1);
        }
    }

    #[test]
    fn repeat_counted_visual_motion_uses_resolved_action_and_normalizes_overlaps() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("one two three".into())])
            .unwrap();
        type_text(&mut editor, "v2ecQ");
        editor.handle(Input::Escape);
        editor
            .bind("visual", "e", Some("core.left".into()))
            .unwrap();
        editor
            .apply(vec![Effect::Replace("a enormous tail".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (0, 2)], 1);
        let undo = editor.active.undo.len();
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Q");
        assert_eq!(editor.selection_count(), 1);
        assert_eq!(editor.active.undo.len(), undo + 1);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "a enormous tail");
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 2 }]
        );
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 2 });
    }

    #[test]
    fn repeat_insert_native_motion_delete_backspace_and_newline_are_one_edit() {
        fn edit(editor: &mut Editor) {
            editor.handle(Input::Char('i'));
            editor.handle(Input::Right);
            type_text(editor, "XY");
            editor.handle(Input::Left);
            editor.handle(Input::Backspace);
            editor.handle(Input::Delete);
            editor.handle(Input::Enter);
            type_text(editor, "Z");
            editor.handle(Input::Right); // Trailing navigation is not part of the edit.
            editor.handle(Input::Escape);
        }
        let mut recorded = editor();
        recorded
            .apply(vec![Effect::Replace("abcdef".into())])
            .unwrap();
        edit(&mut recorded);
        recorded
            .apply(vec![Effect::Replace("123456\nlongertext".into())])
            .unwrap();
        set_carets(&mut recorded, &[(0, 1), (1, 2)], 1);
        let mut expected = editor();
        expected
            .apply(vec![Effect::Replace("123456\nlongertext".into())])
            .unwrap();
        set_carets(&mut expected, &[(0, 1), (1, 2)], 1);
        edit(&mut expected);
        let undo = recorded.active.undo.len();
        recorded.handle(Input::Char('.'));
        assert_eq!(recorded.context().text, expected.context().text);
        assert_eq!(recorded.active.undo.len(), undo + 1);
        recorded.handle(Input::Char('u'));
        assert_eq!(recorded.context().text, "123456\nlongertext");
    }

    #[test]
    fn repeat_omits_noop_insert_deletions_and_preserves_partial_noop_carets() {
        let mut editor = editor();
        editor.handle(Input::Char('i'));
        editor.handle(Input::Backspace);
        editor.handle(Input::Delete);
        type_text(&mut editor, "X");
        editor.handle(Input::Escape);
        editor.apply(vec![Effect::Replace("abcd".into())]).unwrap();
        set_carets(&mut editor, &[(0, 2)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "abXcd");
        editor.apply(vec![Effect::Replace("a\nab".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 1)], 1);
        editor.handle(Input::Char('i'));
        editor.handle(Input::Backspace);
        type_text(&mut editor, "X");
        editor.handle(Input::Escape);
        editor
            .apply(vec![Effect::Replace("cde\nfgh".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 2), (1, 2)], 1);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "cdXe\nfXh");
    }

    #[test]
    fn repeat_partial_deletion_mismatch_rolls_back_visual_change_and_clipboard() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("ab\ncd".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        type_text(&mut editor, "vc");
        editor.handle(Input::Backspace);
        type_text(&mut editor, "X");
        editor.handle(Input::Escape);
        editor
            .apply(vec![Effect::Replace("aa\nbb\ncc".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 2);
        editor.handle(Input::Char('v'));
        let ranges = editor.selections();
        let targets = editor.active.targets.clone();
        let primary = editor.active.primary;
        let clipboard = editor.clipboard.clone();
        let undo = editor.active.undo.len();
        let redo = editor.active.redo.len();
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "aa\nbb\ncc");
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.selections(), ranges);
        assert_eq!(editor.active.targets, targets);
        assert_eq!(editor.active.primary, primary);
        assert_eq!(editor.clipboard, clipboard);
        assert_eq!(editor.active.undo.len(), undo);
        assert_eq!(editor.active.redo.len(), redo);
        assert!(editor.message().contains("count"));
        editor.handle(Input::Escape);
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "XaXb\ncc");
    }

    #[test]
    fn repeat_typed_scalars_keep_right_neighbor_combining_and_zwj_boundaries() {
        for (typed, neighbor, result) in
            [("ab", "\u{301}", "a\u{301}b"), ("👩x", "\u{200d}🚀", "👩‍🚀x")]
        {
            let mut editor = editor();
            editor.handle(Input::Char('i'));
            type_text(&mut editor, typed);
            editor.handle(Input::Escape);
            editor
                .apply(vec![Effect::Replace(neighbor.into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0)], 0);
            let undo = editor.active.undo.len();
            editor.handle(Input::Char('.'));
            assert_eq!(editor.context().text, result);
            assert_eq!(editor.active.undo.len(), undo + 1);
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, neighbor);
            editor.handle(Input::Char('U'));
            assert_eq!(editor.context().text, result);
        }
    }

    #[test]
    fn repeat_literal_paste_is_bulk_literal_and_keeps_original_typing_groups() {
        let mut editor = editor();
        type_text(&mut editor, "iX");
        editor.handle(Input::Paste("ab\r\n:q!".into()));
        type_text(&mut editor, "Y");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "Xab\n:q!Y");
        for expected in ["Xab\n:q!", "X", ""] {
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, expected);
        }
        editor.apply(vec![Effect::Replace("fresh".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Yfresh");
        type_text(&mut editor, "i");
        editor.handle(Input::Paste("ab".into()));
        editor.handle(Input::Escape);
        editor
            .apply(vec![Effect::Replace("\u{301}".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "ab\u{301}");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "\u{301}");
        editor.handle(Input::Char('i'));
        editor.handle(Input::Paste(":q!\r\n".into()));
        editor.handle(Input::Escape);
        editor
            .apply(vec![Effect::Replace("target".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, ":q!\ntarget");
        assert!(!editor.should_quit());
    }

    #[test]
    fn repeat_clipboard_captures_fragments_pairs_broadcasts_and_refuses_mismatch() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("ab\nxyz".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[
                (Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 2 }),
                (Cursor { row: 1, column: 0 }, Cursor { row: 1, column: 3 }),
            ],
            1,
        );
        editor.handle(Input::Char('y'));
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.handle(Input::Char('P'));
        editor.apply(vec![Effect::Replace("OTHER".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        type_text(&mut editor, "vey");
        assert_eq!(editor.clipboard, vec!["OTHER"]);
        editor
            .apply(vec![Effect::Replace("1\n2\n3".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 2);
        let undo = editor.active.undo.len();
        let targets = editor.active.targets.clone();
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "1\n2\n3");
        assert_eq!(editor.active.targets, targets);
        assert_eq!(editor.active.undo.len(), undo);
        assert_eq!(editor.clipboard, vec!["OTHER"]);
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "ab1\nxyz2\n3");
        assert_eq!(editor.clipboard, vec!["OTHER"]);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "1\n2\n3");
        editor.clipboard = vec!["!".into()];
        editor.handle(Input::Char('p'));
        editor
            .apply(vec![Effect::Replace("a\nb\nc".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 1);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "a!\nb!\nc!");
    }

    #[test]
    fn repeat_join_and_normal_delete_are_native_and_noops_keep_the_previous_recipe() {
        let mut editor = editor();
        editor.apply(vec![Effect::Replace("a\n b".into())]).unwrap();
        editor.handle(Input::Char('J'));
        editor
            .apply(vec![Effect::Replace("Done.\n  again\nlast".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        let undo = editor.active.undo.len();
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Done.  again\nlast");
        assert_eq!(editor.active.undo.len(), undo + 1);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "Done.\n  again\nlast");
        editor.apply(vec![Effect::Replace("".into())]).unwrap();
        editor.handle(Input::Char('J'));
        editor.handle(Input::Char('x'));
        editor
            .apply(vec![Effect::Replace("one\n two".into())])
            .unwrap();
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "one two");
        editor.handle(Input::Char('x'));
        editor
            .apply(vec![Effect::Replace("界e\u{301}\n👩‍🚀z".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "e\u{301}\nz");
        assert_eq!(editor.selection_count(), 2);
    }

    #[test]
    fn repeat_identical_change_empty_insert_rejected_paste_and_history_keep_recipe_and_redo() {
        let mut editor = editor();
        editor.apply(vec![Effect::Replace("abc".into())]).unwrap();
        type_text(&mut editor, "iX");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        type_text(&mut editor, "vecabc");
        editor.handle(Input::Escape);
        set_carets(&mut editor, &[(0, 0)], 0);
        type_text(&mut editor, "i");
        editor.handle(Input::Backspace);
        editor.handle(Input::Escape);
        let redo = editor.active.redo.len();
        editor.handle(Input::Char('i'));
        editor.handle(Input::Paste("bad\0".into()));
        editor.handle(Input::Escape);
        assert_eq!(editor.active.redo.len(), redo);
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "Xabc");
        editor.handle(Input::Char('u'));
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Xabc");
    }

    #[test]
    fn repeat_is_session_wide_and_plugin_effects_commit_but_never_record_native_intent() {
        let directory = Directory::new();
        let other = directory.path("other");
        fs::write(&other, "base").unwrap();
        let mut editor = editor();
        type_text(&mut editor, "iN");
        editor.execute(&format!("edit {}", other.display()));
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Nbase");
        editor.register(plugin("fixture", &["greet"])).unwrap();
        assert_eq!(editor.execute("greet").unwrap().command, "greet");
        editor
            .apply(vec![
                Effect::Replace("plugin".into()),
                Effect::Insert("!".into()),
            ])
            .unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        assert_eq!(editor.handle(Input::Char('.')), None);
        assert_eq!(editor.context().text, "N!plugin");
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "T");
        editor.apply(vec![Effect::Insert("P".into())]).unwrap();
        editor.handle(Input::Escape);
        editor.apply(vec![Effect::Replace("fresh".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "Tfresh");
        editor.execute("buffer 1");
        assert_eq!(editor.context().text, "N");
        editor.handle(Input::Char('.'));
        assert_eq!(editor.context().text, "TN");
    }

    #[test]
    fn repeat_action_no_recipe_remaps_and_literal_queries_do_not_record_or_execute_edits() {
        let directory = Directory::new();
        fs::write(directory.path("file.txt"), "file").unwrap();
        let mut editor = project_editor(&directory);
        editor.handle(Input::Char('.'));
        assert_eq!(editor.message(), "Nothing to repeat");
        assert_eq!(editor.context().text, "");
        assert!(editor.active.undo.is_empty());
        editor
            .bind("normal", "r", Some("core.repeat_last_edit".into()))
            .unwrap();
        editor
            .bind("visual", "r", Some("core.repeat_last_edit".into()))
            .unwrap();
        assert!(
            editor
                .bind("insert", "r", Some("core.repeat_last_edit".into()))
                .is_err()
        );
        type_text(&mut editor, "iX");
        editor.open_file_picker(FilePresentation::Docked);
        editor.handle(Input::Char('i'));
        type_text(&mut editor, ".");
        assert_eq!(editor.file_picker().unwrap().query, ".");
        assert_eq!(editor.context().text, "X");
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, ".");
        assert_eq!(editor.palette().unwrap().query, ".");
        editor.handle(Input::Escape);
        type_text(&mut editor, "Y");
        editor.handle(Input::Escape);
        editor.apply(vec![Effect::Replace("fresh".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('r'));
        assert_eq!(editor.context().text, "XYfresh");
        type_text(&mut editor, "i.");
        editor.handle(Input::Escape);
        editor
            .apply(vec![Effect::Replace("target".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('r'));
        assert_eq!(editor.context().text, ".target");
        type_text(&mut editor, "/.");
        assert_eq!(editor.command_line(), ".");
        editor.handle(Input::Escape);
        type_text(&mut editor, ":.");
        assert_eq!(editor.command_line(), ".");
        editor.handle(Input::Escape);
        editor.apply(vec![Effect::Replace("again".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0)], 0);
        editor.handle(Input::Char('r'));
        assert_eq!(editor.context().text, ".again");
    }

    #[test]
    fn buffers_keep_independent_history_saved_text_carets_primary_and_search() {
        let directory = Directory::new();
        let a = directory.path("a");
        let b = directory.path("b");
        fs::write(&a, "cat cat\ncat cat").unwrap();
        fs::write(&b, "dog dog\ndog dog").unwrap();
        let mut editor = Editor::open(Some(a.clone()), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "X");
        editor.handle(Input::Escape);
        submit_search(&mut editor, "cat");
        let a_carets = editor.carets();
        let a_primary = editor.cursor();
        let a_match = editor.search_match();
        editor.execute("w");
        assert!(!editor.dirty());

        editor.execute(&format!("edit {}", b.display()));
        assert_eq!(editor.buffer_id(), 2);
        set_carets(&mut editor, &[(0, 0), (1, 0)], 0);
        submit_search(&mut editor, "dog");
        let b_carets = editor.carets();
        let b_primary = editor.cursor();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "Y");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "dog dog\ndog dog");
        assert_eq!(editor.carets(), b_carets);
        assert_eq!(editor.cursor(), b_primary);
        assert!(!editor.dirty());

        editor.execute("buffer 1");
        assert_eq!(editor.context().text, "Xcat cat\nXcat cat");
        assert_eq!(editor.carets(), a_carets);
        assert_eq!(editor.cursor(), a_primary);
        assert_eq!(editor.search_match(), a_match);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 5 });
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "cat cat\ncat cat");
        assert!(editor.dirty());
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "Xcat cat\nXcat cat");
        assert!(!editor.dirty());
        editor.execute("buffer 2");
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "dog Ydog\ndog Ydog");
        assert!(editor.dirty());
        editor.execute("w");
        assert!(!editor.dirty());
        assert_eq!(fs::read_to_string(&a).unwrap(), "Xcat cat\nXcat cat");
        assert_eq!(fs::read_to_string(&b).unwrap(), "dog Ydog\ndog Ydog");
        editor.execute("buffer 1");
        assert!(!editor.dirty());
    }

    #[test]
    fn explicit_switch_preserves_directed_visual_ranges_and_bound_switch_restores_them() {
        let directory = Directory::new();
        let a = directory.path("a");
        let b = directory.path("b");
        fs::write(&a, "abcdef\nabcdef").unwrap();
        fs::write(&b, "other").unwrap();
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        set_carets(&mut editor, &[(0, 4), (1, 4)], 1);
        type_text(&mut editor, "vhh");
        let carets = editor.carets();
        let primary = editor.cursor();
        let ranges = editor.selections();
        editor.execute(&format!("edit {}", b.display()));
        assert_eq!(editor.mode(), Mode::Normal);
        editor.bind("normal", "g", Some("bprev".into())).unwrap();
        editor.handle(Input::Char('g'));
        assert_eq!(editor.buffer_id(), 1);
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.carets(), carets);
        assert_eq!(editor.cursor(), primary);
        assert_eq!(editor.selections(), ranges);
        editor.execute("bnext");
        editor.execute("buffer 1");
        assert_eq!(editor.mode(), Mode::Visual);
        editor.handle(Input::Char('h'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 1 });
        assert_eq!(editor.selections()[1].end.column, 5);
    }

    #[test]
    fn switching_commits_insert_groups_and_never_restores_transient_prompts() {
        let directory = Directory::new();
        let a = directory.path("a");
        let b = directory.path("b");
        fs::write(&a, "base").unwrap();
        fs::write(&b, "other").unwrap();
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "XY");
        editor.execute(&format!("edit {}", b.display()));
        editor.execute("buffer 1");
        assert_eq!(editor.mode(), Mode::Normal);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "base");
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "XYbase");
        for prompt in [':', '/'] {
            editor.handle(Input::Char(prompt));
            type_text(&mut editor, "unfinished");
            editor.execute("buffer 2");
            assert_eq!(editor.command_line(), "");
            editor.execute("buffer 1");
            assert_eq!(editor.mode(), Mode::Normal);
            assert_eq!(editor.command_line(), "");
        }
    }

    #[test]
    fn failed_opens_and_invalid_buffer_arguments_leave_editing_state_untouched() {
        let directory = Directory::new();
        let bad = directory.path("bad");
        fs::write(&bad, b"\xff").unwrap();
        let controls = directory.path("controls");
        fs::write(&controls, "bad\0").unwrap();
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("abcdef".into())])
            .unwrap();
        type_text(&mut editor, "llvhh");
        let ranges = editor.selections();
        let carets = editor.carets();
        let cursor = editor.cursor();
        let undo = editor.active.undo.len();
        let commands = [
            format!("edit {}", bad.display()),
            format!("edit {}", controls.display()),
            format!("edit {}", directory.0.display()),
            "edit".into(),
            "buffer".into(),
            "buffer 0".into(),
            "buffer -1".into(),
            "buffer 99".into(),
            "buffer 1 2".into(),
            "bnext 1".into(),
            "bprev 1".into(),
            "buffers 1".into(),
            "bdelete nope".into(),
            "bdelete! 99".into(),
            "bdelete 999999999999999999999999999999".into(),
        ];
        for command in commands {
            editor.execute(&command);
            assert_eq!(editor.buffer_count(), 1);
            assert_eq!(editor.buffer_id(), 1);
            assert_eq!(editor.context().text, "abcdef");
            assert_eq!(editor.mode(), Mode::Visual);
            assert_eq!(editor.selections(), ranges);
            assert_eq!(editor.carets(), carets);
            assert_eq!(editor.cursor(), cursor);
            assert_eq!(editor.active.undo.len(), undo);
        }
        editor.handle(Input::Escape);
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "X");
        editor.execute(&format!("edit {}", bad.display()));
        assert_eq!(editor.mode(), Mode::Insert);
        type_text(&mut editor, "Y");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "abcdef");
    }

    #[test]
    fn stable_buffer_ids_wrap_close_inactive_and_replace_the_last_buffer() {
        let directory = Directory::new();
        let mut editor = editor();
        let a = directory.path("new a");
        let b = directory.path("new b");
        editor.execute(&format!("edit {}", a.display()));
        editor.execute(&format!("edit {}", b.display()));
        assert_eq!(
            editor.buffers().map(|buffer| buffer.id).collect::<Vec<_>>(),
            vec![1, 2, 3],
        );
        let info = editor.buffers().find(|buffer| buffer.id == 3).unwrap();
        assert_eq!(info.path, Some(b.as_path()));
        assert!(info.active);
        assert!(!info.dirty);
        editor.execute("bdelete 2");
        assert_eq!(editor.buffer_id(), 3);
        assert!(!editor.has_buffer(2));
        assert_eq!(editor.buffer_count(), 2);
        editor.execute("bnext");
        assert_eq!(editor.buffer_id(), 1);
        editor.execute("bprev");
        assert_eq!(editor.buffer_id(), 3);
        editor.execute("bdelete");
        assert_eq!(editor.buffer_id(), 1);
        editor.execute("bdelete");
        assert_eq!(editor.buffer_id(), 4);
        assert_eq!(editor.buffer_count(), 1);
        assert_eq!(editor.path(), None);
        assert_eq!(editor.context().text, "");
        assert!(!editor.dirty());
        assert!(!editor.should_quit());
        editor.execute("bnext");
        editor.execute("bprev");
        assert_eq!(editor.buffer_id(), 4);
        editor.execute(&format!("edit {}", a.display()));
        assert_eq!(editor.buffer_id(), 5);
        assert_eq!(editor.buffer_count(), 2);
        editor.execute("buffer 2");
        assert_eq!(editor.buffer_id(), 5);
    }

    #[test]
    fn hidden_dirty_buffers_block_quit_write_quit_and_unforced_deletion() {
        let directory = Directory::new();
        let a = directory.path("a");
        let b = directory.path("b");
        fs::write(&a, "a").unwrap();
        fs::write(&b, "b").unwrap();
        let mut editor = Editor::open(Some(a), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor
            .apply(vec![Effect::Replace("dirty a".into())])
            .unwrap();
        editor.execute(&format!("edit {}", b.display()));
        assert!(!editor.dirty());
        editor.execute("q");
        assert!(!editor.should_quit());
        editor
            .apply(vec![Effect::Replace("saved b".into())])
            .unwrap();
        editor.execute("wq");
        assert!(!editor.should_quit());
        assert!(!editor.dirty());
        assert_eq!(fs::read_to_string(&b).unwrap(), "saved b");
        editor.execute("bdelete 1");
        assert!(editor.has_buffer(1));
        assert_eq!(editor.buffer_id(), 2);
        editor.execute("buffer 1");
        assert_eq!(editor.context().text, "dirty a");
        editor.execute("bdelete");
        assert_eq!(editor.buffer_id(), 1);
        editor.execute("bdelete!");
        assert_eq!(editor.buffer_id(), 2);
        editor.execute("q");
        assert!(editor.should_quit());

        let mut forced = Editor::open(Some(b), vec![]).unwrap();
        forced.set_clipboard_mode("separate").unwrap();
        forced.apply(vec![Effect::Replace("dirty".into())]).unwrap();
        forced.execute(&format!("edit {}", directory.path("new").display()));
        forced.execute("q! arguments");
        assert!(!forced.should_quit());
        forced.execute("bdelete! 1");
        assert_eq!(forced.buffer_id(), 2);
        assert!(!forced.has_buffer(1));
        forced
            .apply(vec![Effect::Replace("also dirty".into())])
            .unwrap();
        forced.execute("bdelete!");
        assert_eq!(forced.buffer_id(), 3);
        assert!(!forced.dirty());
        forced
            .apply(vec![Effect::Replace("quit dirty".into())])
            .unwrap();
        forced.execute(&format!("edit {}", directory.path("another").display()));
        forced.execute("q!");
        assert!(forced.should_quit());
    }

    #[test]
    fn loaded_paths_refuse_save_collisions_before_touching_files_or_saved_state() {
        let directory = Directory::new();
        let a = directory.path("a");
        let b = directory.path("b");
        fs::write(&a, "a").unwrap();
        fs::write(&b, "b").unwrap();
        let mut editor = Editor::open(Some(a.clone()), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor.execute(&format!("edit {}", b.display()));
        editor
            .apply(vec![Effect::Replace("dirty b".into())])
            .unwrap();
        editor.execute(&format!("w {}", directory.0.join("./a").display()));
        assert!(editor.message().contains("belongs to buffer 1"));
        assert_eq!(editor.path(), Some(b.as_path()));
        assert!(editor.dirty());
        assert_eq!(fs::read_to_string(&a).unwrap(), "a");
        assert_eq!(fs::read_to_string(&b).unwrap(), "b");
        assert_eq!(fs::read_dir(&directory.0).unwrap().count(), 2);
        editor.execute(&format!("wq {}", a.display()));
        assert!(!editor.should_quit());
        assert!(editor.dirty());
        editor.execute(&format!("w {}", directory.0.join("./b").display()));
        assert!(!editor.dirty());
        assert_eq!(fs::read_to_string(&b).unwrap(), "dirty b");
        let new = directory.path("missing");
        editor.execute(&format!("edit {}", new.display()));
        editor.execute("buffer 2");
        editor.execute(&format!("w {}", new.display()));
        assert!(editor.message().contains("belongs to buffer 3"));
        assert!(!new.exists());
        assert!(!editor.dirty());
    }

    #[test]
    fn clipboard_bindings_plugins_and_palette_catalog_are_session_wide() {
        let directory = Directory::new();
        let mut editor = editor();
        editor.register(plugin("fixture", &["greet"])).unwrap();
        editor.bind("normal", "g", Some("greet".into())).unwrap();
        editor.bind("normal", "z", Some("bnext".into())).unwrap();
        editor
            .apply(vec![Effect::Replace("copied".into())])
            .unwrap();
        type_text(&mut editor, "v$y");
        editor.execute(&format!("edit {}", directory.path("new").display()));
        editor.handle(Input::Char('p'));
        assert_eq!(editor.context().text, "copied");
        assert_eq!(editor.handle(Input::Char('g')).unwrap().plugin, "fixture");
        editor.handle(Input::Char('z'));
        assert_eq!(editor.buffer_id(), 1);
        assert_eq!(editor.handle(Input::Char('g')).unwrap().command, "greet");
        editor.handle(Input::Ctrl('p'));
        for command in [
            "edit", "buffers", "buffer", "bnext", "bprev", "bdelete", "bdelete!",
        ] {
            let entry = palette_entry(&editor, command);
            assert_eq!(entry.owner, "core");
            assert!(entry.enabled);
        }
        assert_eq!(
            palette_entry(&editor, "bnext").bindings,
            vec!["Space b n", "z"]
        );
        editor.disable_plugin("fixture", "failure");
        assert!(
            !editor
                .palette()
                .unwrap()
                .entries
                .iter()
                .any(|entry| entry.name == "greet")
        );
        editor.handle(Input::Escape);
        editor.execute("buffer 2");
        assert_eq!(editor.handle(Input::Char('g')), None);
        editor.execute("plugins");
        assert!(!editor.message().contains("fixture"));
        assert!(editor.message().contains("bdelete!"));
    }

    #[cfg(unix)]
    #[test]
    fn canonical_aliases_reuse_dirty_buffers_and_new_paths_are_normalized() {
        use std::os::unix::fs::symlink;
        let directory = Directory::new();
        let path = directory.path("file");
        let link = directory.path("file link");
        fs::write(&path, "disk").unwrap();
        symlink(&path, &link).unwrap();
        let mut editor = Editor::open(Some(link.clone()), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor
            .apply(vec![Effect::Replace("dirty memory".into())])
            .unwrap();
        editor.execute(&format!("edit {}", directory.path("other").display()));
        fs::write(&path, "changed externally").unwrap();
        editor.execute(&format!("edit {}", path.display()));
        assert_eq!(editor.buffer_id(), 1);
        assert_eq!(editor.buffer_count(), 2);
        assert_eq!(editor.path(), Some(link.as_path()));
        assert_eq!(editor.context().text, "dirty memory");
        assert!(editor.dirty());
        editor.execute("w");
        assert!(editor.message().contains("symbolic link"));
        assert!(editor.dirty());
        assert_eq!(fs::read_to_string(&path).unwrap(), "changed externally");
        editor.execute(&format!("w {}", path.display()));
        assert!(!editor.dirty());
        assert_eq!(editor.path(), Some(path.as_path()));

        let alias = directory.path("directory link");
        symlink(&directory.0, &alias).unwrap();
        let new = alias.join("new");
        editor.execute(&format!("edit {}", new.display()));
        assert_eq!(editor.buffer_id(), 3);
        editor
            .apply(vec![Effect::Replace("new memory".into())])
            .unwrap();
        editor.execute("buffer 1");
        editor.execute(&format!(
            "edit {}",
            directory.0.join("absent/../new").display()
        ));
        assert_eq!(editor.buffer_id(), 3);
        assert_eq!(editor.buffer_count(), 3);
        assert_eq!(editor.context().text, "new memory");
        assert_eq!(editor.path(), Some(new.as_path()));
        editor.execute(&format!("w {}", link.display()));
        assert!(editor.message().contains("belongs to buffer 1"));
        assert!(editor.dirty());
        assert_eq!(fs::read_to_string(&path).unwrap(), "dirty memory");
        assert!(!new.exists());
        editor.execute("buffers");
        assert!(editor.message().contains("1 "));
        assert!(editor.message().contains("3%+ "));
        let control_path = directory.path("line\nbreak");
        editor.execute(&format!("edit {}", control_path.display()));
        editor.execute("buffers");
        assert!(!editor.message().chars().any(char::is_control));
        assert!(editor.message().contains("line break"));
    }

    fn palette_entry<'a>(editor: &'a Editor, name: &str) -> &'a PaletteEntry {
        editor
            .palette()
            .unwrap()
            .entries
            .iter()
            .find(|entry| entry.name == name)
            .unwrap()
    }

    #[test]
    fn palette_cancellation_preserves_every_underlying_mode_and_insert_group() {
        for mode in [
            Mode::Normal,
            Mode::Insert,
            Mode::Command,
            Mode::Search,
            Mode::Visual,
        ] {
            for cancel in [Input::Escape, Input::Ctrl('p')] {
                let mut editor = editor();
                let original = "alpha beta\nalpha beta";
                editor
                    .apply(vec![Effect::Replace(original.into())])
                    .unwrap();
                editor.apply(vec![Effect::Insert("extra".into())]).unwrap();
                editor.undo();
                submit_search(&mut editor, "alpha");
                set_carets(&mut editor, &[(0, 0), (1, 0)], 1);
                match mode {
                    Mode::Normal => {}
                    Mode::Insert => {
                        editor.handle(Input::Char('i'));
                        type_text(&mut editor, "X");
                    }
                    Mode::Command => {
                        editor.handle(Input::Char(':'));
                        type_text(&mut editor, "w output");
                    }
                    Mode::Search => {
                        editor.handle(Input::Char('/'));
                        type_text(&mut editor, "alpha e\u{301}");
                    }
                    Mode::Visual => {
                        editor.handle(Input::Char('v'));
                        editor.handle(Input::Right);
                    }
                }
                let snapshot =
                    |state: &Snapshot| (state.lines.clone(), state.targets.clone(), state.primary);
                let lines = editor.active.lines.clone();
                let targets = editor.active.targets.clone();
                let primary = editor.active.primary;
                let selections = editor.selections();
                let prompt = editor.command_line.clone();
                let search = editor.active.search_query.clone();
                let found = editor.active.search_match;
                let message = editor.message.clone();
                let undo: Vec<_> = editor.active.undo.iter().map(&snapshot).collect();
                let redo: Vec<_> = editor.active.redo.iter().map(&snapshot).collect();
                let insert = editor.active.insert_start.as_ref().map(snapshot);

                editor.handle(Input::Ctrl('p'));
                assert!(editor.palette().is_some());
                editor.handle(Input::Ctrl('j'));
                editor.handle(Input::Ctrl('k'));
                type_text(&mut editor, "query Δe\u{301}👩‍🚀 ");
                editor.handle(Input::Backspace);
                editor.handle(Input::Backspace);
                assert_eq!(editor.palette().unwrap().query, "query Δe\u{301}");
                editor.handle(Input::Paste("ignored\n:q!".into()));
                editor.handle(Input::Down);
                editor.handle(Input::Ctrl('k'));
                editor.handle(cancel);

                assert!(editor.palette().is_none());
                assert_eq!(editor.mode(), mode);
                assert_eq!(editor.active.lines, lines);
                assert_eq!(editor.active.targets, targets);
                assert_eq!(editor.active.primary, primary);
                assert_eq!(editor.selections(), selections);
                assert_eq!(editor.command_line, prompt);
                assert_eq!(editor.active.search_query, search);
                assert_eq!(editor.active.search_match, found);
                assert_eq!(editor.message, message);
                assert_eq!(
                    editor.active.undo.iter().map(&snapshot).collect::<Vec<_>>(),
                    undo
                );
                assert_eq!(
                    editor.active.redo.iter().map(&snapshot).collect::<Vec<_>>(),
                    redo
                );
                assert_eq!(editor.active.insert_start.as_ref().map(snapshot), insert);
                if mode == Mode::Insert {
                    type_text(&mut editor, "Y");
                    editor.handle(Input::Escape);
                    editor.handle(Input::Char('u'));
                    assert_eq!(editor.context().text, original);
                }
            }
        }
    }

    #[test]
    fn palette_filters_all_tokens_and_wraps_without_executing_empty_results() {
        let mut editor = editor();
        editor
            .register(plugin("Älpha Tools", &["greet_one", "greet_two"]))
            .unwrap();
        editor.handle(Input::Ctrl('p'));
        let order: Vec<_> = editor
            .palette()
            .unwrap()
            .entries
            .iter()
            .map(|entry| (entry.label.clone(), entry.name.clone()))
            .collect();
        assert!(order.windows(2).all(|pair| pair[0] <= pair[1]));
        assert!(
            !editor
                .palette()
                .unwrap()
                .entries
                .iter()
                .any(|entry| entry.name == "core.palette")
        );
        type_text(&mut editor, "GREET ÄLPHA");
        assert_eq!(editor.palette().unwrap().entries.len(), 2);
        assert_eq!(editor.palette().unwrap().entries[0].name, "greet_one");
        editor.handle(Input::Up);
        assert_eq!(editor.palette().unwrap().selected, 1);
        editor.handle(Input::Ctrl('n'));
        assert_eq!(editor.palette().unwrap().selected, 0);
        editor.handle(Input::Down);
        assert_eq!(editor.palette().unwrap().selected, 1);
        editor.handle(Input::Ctrl('k'));
        assert_eq!(editor.palette().unwrap().selected, 0);
        editor.handle(Input::Down);
        editor.handle(Input::Char(' '));
        assert_eq!(editor.palette().unwrap().selected, 0);
        type_text(&mut editor, "missing");
        assert!(editor.palette().unwrap().entries.is_empty());
        for input in [
            Input::Enter,
            Input::Up,
            Input::Down,
            Input::Ctrl('j'),
            Input::Ctrl('k'),
            Input::Ctrl('n'),
        ] {
            assert_eq!(editor.handle(input), None);
            assert_eq!(editor.palette().unwrap().selected, 0);
        }
        while !editor.palette().unwrap().query.is_empty() {
            editor.handle(Input::Backspace);
        }
        type_text(&mut editor, "e\u{301}👩‍🚀");
        editor.handle(Input::Backspace);
        assert_eq!(editor.palette().unwrap().query, "e\u{301}");
        editor.handle(Input::Backspace);
        assert_eq!(editor.palette().unwrap().query, "");
        assert!(!editor.palette().unwrap().entries.is_empty());
        editor.handle(Input::Ctrl('i'));
        assert_eq!(editor.palette().unwrap().query, "");
    }

    #[test]
    fn palette_catalog_shares_binding_eligibility_and_keeps_disabled_rows() {
        let mut names = HashSet::new();
        for &(name, action, modes) in CORE_ACTIONS {
            assert!(names.insert(name));
            for mode in [
                Mode::Normal,
                Mode::Insert,
                Mode::Command,
                Mode::Search,
                Mode::Visual,
            ] {
                assert!(Action::named(mode, name) == modes.contains(&mode).then_some(action));
            }
        }
        for mode in [Mode::Insert, Mode::Command, Mode::Search, Mode::Visual] {
            let mut editor = editor();
            editor.active.mode = mode;
            editor.command_line = "untouched".into();
            editor.handle(Input::Ctrl('p'));
            type_text(&mut editor, "core.undo");
            let entry = palette_entry(&editor, "core.undo");
            assert!(!entry.enabled);
            assert_eq!(entry.modes, vec![Mode::Normal]);
            assert!(entry.bindings.is_empty());
            editor.handle(Input::Ctrl('j'));
            editor.handle(Input::Ctrl('k'));
            assert_eq!(editor.palette().unwrap().query, "core.undo");
            assert_eq!(editor.handle(Input::Enter), None);
            assert!(editor.palette().is_some());
            assert_eq!(editor.mode(), mode);
            assert_eq!(editor.command_line(), "untouched");
            while !editor.palette().unwrap().query.is_empty() {
                editor.handle(Input::Backspace);
            }
            type_text(&mut editor, "q!");
            assert_eq!(editor.palette().unwrap().entries.len(), 1);
            assert!(!palette_entry(&editor, "q!").enabled);
            editor.handle(Input::Enter);
            assert!(!editor.should_quit());
            assert!(editor.palette().is_some());
        }
    }

    #[test]
    fn palette_effective_bindings_refresh_with_canonical_terminal_names() {
        let mut editor = editor();
        editor.handle(Input::Ctrl('p'));
        assert_eq!(palette_entry(&editor, "core.insert").bindings, vec!["i"]);
        editor.bind("normal", "i", None).unwrap();
        assert!(palette_entry(&editor, "core.insert").bindings.is_empty());
        for key in [
            "shift+i", "ctrl+m", "ctrl+h", "ctrl+i", "space", "ctrl+r", "界",
        ] {
            editor
                .bind("normal", key, Some("core.insert".into()))
                .unwrap();
        }
        editor
            .bind("normal", "ctrl+j", Some("core.insert".into()))
            .unwrap();
        assert_eq!(
            palette_entry(&editor, "core.insert").bindings,
            vec![
                "Ctrl+h", "Ctrl+j", "Ctrl+r", "Enter", "I", "Space", "Tab", "界"
            ]
        );
        assert!(
            palette_entry(&editor, "core.insert_first_nonblank")
                .bindings
                .is_empty()
        );
        editor.bind("normal", "ENTER", None).unwrap();
        assert!(
            !palette_entry(&editor, "core.insert")
                .bindings
                .iter()
                .any(|key| key == "Enter")
        );
        editor
            .bind("normal", "界", Some("core.undo".into()))
            .unwrap();
        assert_eq!(
            palette_entry(&editor, "core.undo").bindings,
            vec!["u", "界"]
        );
        assert!(
            !palette_entry(&editor, "core.insert")
                .bindings
                .iter()
                .any(|key| key == "界")
        );
        assert!(
            editor
                .bind("insert", "g", Some("core.undo".into()))
                .is_err()
        );
        editor.handle(Input::Escape);
        editor.bind("normal", "ctrl+p", None).unwrap();
        editor
            .bind("normal", "ctrl+f", Some("core.palette".into()))
            .unwrap();
        editor.handle(Input::Ctrl('p'));
        assert!(editor.palette().is_none());
        editor.handle(Input::Ctrl('f'));
        assert!(editor.palette().is_some());
        editor.handle(Input::Ctrl('p'));
        assert!(editor.palette().is_none());
    }

    #[test]
    fn palette_registered_commands_refresh_and_retire_with_plugins() {
        let mut editor = editor();
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "fixture");
        assert!(editor.palette().unwrap().entries.is_empty());
        editor.register(plugin("fixture", &["greet"])).unwrap();
        assert_eq!(editor.palette().unwrap().entries.len(), 1);
        assert_eq!(palette_entry(&editor, "greet").owner, "fixture");
        assert!(palette_entry(&editor, "greet").enabled);
        editor.bind("normal", "g", Some("greet".into())).unwrap();
        assert_eq!(palette_entry(&editor, "greet").bindings, vec!["g"]);
        editor.disable_plugin("fixture", "retired");
        assert!(editor.palette().unwrap().entries.is_empty());
        editor.handle(Input::Enter);
        assert!(editor.palette().is_some());
        editor.handle(Input::Escape);
        assert_eq!(editor.handle(Input::Char('g')), None);
        assert!(editor.bind("normal", "g", Some("greet".into())).is_err());
    }

    #[test]
    fn palette_commands_require_prompt_submission_and_dispatch_arguments_once() {
        let mut editor = editor();
        editor.register(plugin("fixture", &["greet"])).unwrap();
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "greet");
        assert_eq!(editor.handle(Input::Enter), None);
        assert!(editor.palette().is_none());
        assert_eq!(editor.mode(), Mode::Command);
        assert_eq!(editor.command_line(), "greet ");
        type_text(&mut editor, "界!");
        assert_eq!(
            editor.handle(Input::Enter),
            Some(Invocation {
                plugin: "fixture".into(),
                command: "greet".into(),
                args: "界!".into(),
            })
        );
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.handle(Input::Enter), None);
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "q!");
        editor.handle(Input::Enter);
        assert_eq!(editor.command_line(), "q! ");
        assert!(!editor.should_quit());
        editor.handle(Input::Enter);
        assert!(editor.should_quit());
    }

    #[test]
    fn palette_actions_dispatch_visual_change_insert_newline_and_original_prompts() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("alpha beta".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[(Cursor::default(), Cursor { row: 0, column: 5 })],
            0,
        );
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "core.change");
        assert!(palette_entry(&editor, "core.change").enabled);
        editor.handle(Input::Enter);
        assert!(editor.palette().is_none());
        assert_eq!(editor.mode(), Mode::Insert);
        assert_eq!(editor.context().text, " beta");
        type_text(&mut editor, "Ω");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "Ω beta");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "alpha beta");

        let mut insertion = self::editor();
        insertion.handle(Input::Char('i'));
        type_text(&mut insertion, "A");
        insertion.handle(Input::Ctrl('p'));
        type_text(&mut insertion, "core.newline");
        insertion.handle(Input::Enter);
        assert_eq!(insertion.mode(), Mode::Insert);
        assert_eq!(insertion.lines(), &["A", ""]);
        type_text(&mut insertion, "B");
        insertion.handle(Input::Escape);
        insertion.handle(Input::Char('u'));
        assert_eq!(insertion.context().text, "");
        insertion.handle(Input::Char('U'));
        assert_eq!(insertion.context().text, "A\nB");

        editor.handle(Input::Char(':'));
        type_text(&mut editor, "plugins");
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "core.submit");
        editor.handle(Input::Enter);
        assert_eq!(editor.mode(), Mode::Normal);
        assert!(editor.message().starts_with("Capabilities: "));
        assert_eq!(editor.command_line(), "");
        editor.handle(Input::Char('/'));
        type_text(&mut editor, "beta");
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "core.submit");
        editor.handle(Input::Enter);
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.active.search_query, "beta");
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 6 });
    }

    #[test]
    fn palette_survives_rejected_effects_but_external_execution_closes_it() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("alpha beta".into())])
            .unwrap();
        editor.handle(Input::Char('v'));
        editor.handle(Input::Right);
        let targets = editor.active.targets.clone();
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "core.change");
        let undo = editor.active.undo.len();
        assert!(
            editor
                .apply(vec![
                    Effect::Message("changed".into()),
                    Effect::Insert("\0".into())
                ])
                .is_err()
        );
        assert_eq!(editor.palette().unwrap().query, "core.change");
        assert_eq!(editor.mode(), Mode::Visual);
        assert_eq!(editor.active.targets, targets);
        assert_eq!(editor.active.undo.len(), undo);
        editor.apply(vec![Effect::Message("ok".into())]).unwrap();
        assert_eq!(editor.palette().unwrap().query, "core.change");
        assert_eq!(editor.active.targets, targets);
        editor.execute("plugins");
        assert!(editor.palette().is_none());
        assert_eq!(editor.mode(), Mode::Normal);

        editor.handle(Input::Char('v'));
        editor.handle(Input::Ctrl('p'));
        type_text(&mut editor, "core.change");
        editor.apply(vec![Effect::Insert("!".into())]).unwrap();
        assert_eq!(editor.mode(), Mode::Normal);
        assert!(!palette_entry(&editor, "core.change").enabled);
    }

    #[test]
    fn visual_change_replaces_reversed_multiline_graphemes_in_one_undo_group() {
        let mut editor = editor();
        let original = "pre界e\u{301}\n\n👩‍🚀tail\npost";
        editor
            .apply(vec![Effect::Replace(original.into())])
            .unwrap();
        submit_search(&mut editor, "👩‍🚀");
        editor.handle(Input::Char('v'));
        editor.handle(Input::Up);
        editor.handle(Input::Up);
        for _ in 0..3 {
            editor.handle(Input::Right);
        }
        editor.handle(Input::Char('c'));
        assert_eq!(editor.mode(), Mode::Insert);
        assert!(editor.selections().is_empty());
        assert_eq!(editor.search_match(), None);
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 3 });
        assert_eq!(editor.context().text, "pretail\npost");
        editor.handle(Input::Paste("\0".into()));
        type_text(&mut editor, "α\nβ");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "preα\nβtail\npost");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, original);
        assert_eq!(editor.mode(), Mode::Normal);
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "preα\nβtail\npost");
    }

    #[test]
    fn visual_change_at_eof_and_empty_ranges_preserves_clipboard() {
        let mut editor = editor();
        editor.apply(vec![Effect::Replace("abX".into())]).unwrap();
        editor.handle(Input::End);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Char('c'));
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 2 });
        type_text(&mut editor, "YZ");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "abYZ");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "abX");
        editor.apply(vec![Effect::Replace("".into())]).unwrap();
        editor.handle(Input::Char('v'));
        assert_eq!(editor.selections()[0].start, editor.selections()[0].end);
        editor.handle(Input::Char('c'));
        type_text(&mut editor, "new");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('p'));
        assert_eq!(editor.context().text, "X");
    }

    #[test]
    fn visual_change_with_identical_replacement_preserves_redo() {
        let mut editor = editor();
        editor.apply(vec![Effect::Replace("abc".into())]).unwrap();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "X");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        editor.handle(Input::Char('v'));
        editor.handle(Input::Char('e'));
        editor.handle(Input::Char('c'));
        type_text(&mut editor, "abc");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "Xabc");
    }

    #[test]
    fn visual_ranges_copy_both_directions_and_cut_and_paste_multiline_graphemes() {
        let mut editor = editor();
        let text = "a界e\u{301}z\n\n👩‍🚀tail\n";
        editor.apply(vec![Effect::Replace(text.into())]).unwrap();
        editor.handle(Input::Right);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Right);
        assert_eq!(
            editor.selections(),
            vec![Selection {
                start: Cursor { row: 0, column: 1 },
                end: Cursor { row: 0, column: 3 },
            }]
        );
        editor.handle(Input::Left);
        editor.handle(Input::Left);
        assert_eq!(
            editor.selections()[0],
            Selection {
                start: Cursor { row: 0, column: 0 },
                end: Cursor { row: 0, column: 2 },
            }
        );
        editor.handle(Input::Down);
        assert_eq!(editor.selections()[0].end, Cursor { row: 2, column: 0 });
        let selected = editor.selections();
        editor.handle(Input::Paste(":q!\n".into()));
        assert_eq!(editor.selections(), selected);
        editor.handle(Input::Down);
        editor.handle(Input::Char('d'));
        assert!(editor.selections().is_empty());
        assert_eq!(editor.context().text, "atail\n");
        editor.handle(Input::Char('P'));
        assert_eq!(editor.context().text, text);
        editor.handle(Input::Char('u'));
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, text);
        assert_eq!(editor.mode(), Mode::Normal);
    }

    #[test]
    fn clipboard_copy_preserves_redo_and_survives_history_and_grapheme_merging() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("\u{301}".into())])
            .unwrap();
        editor.handle(Input::Char('v'));
        editor.handle(Input::Char('y'));
        editor.handle(Input::Char('u'));
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "\u{301}");
        editor.apply(vec![Effect::Replace("a".into())]).unwrap();
        editor.handle(Input::Char('p'));
        assert_eq!(editor.context().text, "a\u{301}");
        assert_eq!(editor.cursor(), Cursor::default());
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "a");
    }

    #[test]
    fn visual_empty_lines_include_real_newlines_and_row_split_excludes_exclusive_end() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("ab\n\ncd\n".into())])
            .unwrap();
        editor.handle(Input::Down);
        editor.handle(Input::Char('v'));
        assert_eq!(
            editor.selections(),
            vec![Selection {
                start: Cursor { row: 1, column: 0 },
                end: Cursor { row: 2, column: 0 },
            }]
        );
        editor.handle(Input::Ctrl('l'));
        assert_eq!(editor.carets(), vec![Cursor { row: 1, column: 0 }]);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Delete);
        assert_eq!(editor.context().text, "ab\ncd\n");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "ab\n\ncd\n");
    }

    #[test]
    fn batch_insert_newline_backspace_and_delete_use_prebuffer_offsets() {
        let mut editor = editor();
        editor.apply(vec![Effect::Replace("abcd".into())]).unwrap();
        set_carets(&mut editor, &[(0, 0), (0, 2)], 1);
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "X");
        assert_eq!(editor.context().text, "XabXcd");
        editor.handle(Input::Enter);
        assert_eq!(editor.context().text, "X\nabX\ncd");
        editor.handle(Input::Backspace);
        assert_eq!(editor.context().text, "XabXcd");
        editor.handle(Input::Delete);
        assert_eq!(editor.context().text, "XbXd");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "abcd");
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 2 }]
        );
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 2 });
    }

    #[test]
    fn visual_insert_and_append_split_ragged_rows_without_padding() {
        for (key, expected) in [('I', "  !aa\n!\n !zzz"), ('A', "  aa!\n!\n zzz!")] {
            let mut editor = editor();
            editor
                .apply(vec![Effect::Replace("  aa\n\n zzz".into())])
                .unwrap();
            editor.handle(Input::Char('v'));
            editor.handle(Input::Down);
            editor.handle(Input::Down);
            editor.handle(Input::Char(key));
            assert_eq!(editor.mode(), Mode::Insert);
            assert_eq!(editor.selection_count(), 3);
            type_text(&mut editor, "!");
            editor.handle(Input::Escape);
            assert_eq!(editor.context().text, expected);
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, "  aa\n\n zzz");
        }
    }

    #[test]
    fn unequal_word_changes_and_typing_share_undo_and_restore_primary_carets() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("foo\nlonger".into())])
            .unwrap();
        editor.handle(Input::Ctrl('e'));
        editor.handle(Input::Char('v'));
        editor.handle(Input::Char('e'));
        assert_eq!(
            editor
                .selections()
                .iter()
                .map(|range| range.end.column)
                .collect::<Vec<_>>(),
            vec![3, 6]
        );
        let before = editor.carets();
        let primary = editor.cursor();
        editor.handle(Input::Char('c'));
        type_text(&mut editor, "X");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "X\nX");
        assert_eq!(editor.clipboard, vec!["foo", "longer"]);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "foo\nlonger");
        assert_eq!(editor.carets(), before);
        assert_eq!(editor.cursor(), primary);
        assert_eq!(editor.mode(), Mode::Normal);
        assert!(editor.selections().is_empty());
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "X\nX");
    }

    #[test]
    fn unicode_overlap_merges_but_adjacency_preserves_distinct_fragments() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("a\u{301}👩‍🚀界z".into())])
            .unwrap();
        editor.active.mode = Mode::Visual;
        editor.active.targets = vec![
            editor.range_target(
                Selection {
                    start: Cursor { row: 0, column: 0 },
                    end: Cursor { row: 0, column: 2 },
                },
                true,
            ),
            editor.range_target(
                Selection {
                    start: Cursor { row: 0, column: 1 },
                    end: Cursor { row: 0, column: 3 },
                },
                false,
            ),
            editor.range_target(
                Selection {
                    start: Cursor { row: 0, column: 3 },
                    end: Cursor { row: 0, column: 4 },
                },
                true,
            ),
        ];
        editor.active.primary = 1;
        editor.normalize_targets();
        assert_eq!(editor.selection_count(), 2);
        assert_eq!(editor.selections()[0].end.column, 3);
        assert_eq!(editor.cursor().column, 0);
        editor.handle(Input::Char('d'));
        assert_eq!(editor.context().text, "");
        assert_eq!(editor.clipboard, vec!["a\u{301}👩‍🚀界", "z"]);
        assert_eq!(editor.selection_count(), 1);
        editor.handle(Input::Char('u'));
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 3 }]
        );
    }

    #[test]
    fn clipboard_pairs_in_document_order_broadcasts_one_and_refuses_mismatch_atomically() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("ab\nxyzq".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[
                (Cursor { row: 0, column: 0 }, Cursor { row: 0, column: 1 }),
                (Cursor { row: 1, column: 0 }, Cursor { row: 1, column: 3 }),
            ],
            1,
        );
        editor.handle(Input::Char('d'));
        assert_eq!(editor.context().text, "b\nq");
        editor.handle(Input::Char('P'));
        assert_eq!(editor.context().text, "ab\nxyzq");
        editor.handle(Input::Char('u'));
        editor.handle(Input::Escape);
        let before = editor.snapshot();
        let undo = editor.active.undo.len();
        let redo = editor.active.redo.len();
        editor.handle(Input::Char('p'));
        assert_eq!(editor.active.lines, before.lines);
        assert_eq!(editor.active.targets, before.targets);
        assert_eq!(editor.active.primary, before.primary);
        assert_eq!(
            (editor.active.undo.len(), editor.active.redo.len()),
            (undo, redo)
        );
        assert!(editor.message().contains("fragment count"));
        editor.clipboard = vec!["!".into()];
        set_carets(&mut editor, &[(0, 0), (1, 0)], 0);
        editor.handle(Input::Char('P'));
        assert_eq!(editor.context().text, "!b\n!q");
    }

    #[test]
    fn literal_multiline_occurrences_skip_wrap_select_all_and_escape_in_two_stages() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("α\nβ α\nβ α\nβ".into())])
            .unwrap();
        set_ranges(
            &mut editor,
            &[(Cursor { row: 0, column: 0 }, Cursor { row: 1, column: 1 })],
            0,
        );
        editor.handle(Input::Ctrl('n'));
        assert_eq!(editor.selection_count(), 2);
        assert_eq!(editor.cursor(), Cursor { row: 2, column: 0 });
        editor.handle(Input::Ctrl('s'));
        assert_eq!(editor.selection_count(), 2);
        assert_eq!(editor.cursor(), Cursor { row: 3, column: 0 });
        editor.handle(Input::Ctrl('n'));
        assert_eq!(editor.selection_count(), 3);
        assert_eq!(editor.cursor(), Cursor { row: 2, column: 0 });
        editor.handle(Input::Ctrl('a'));
        assert_eq!(editor.selection_count(), 3);
        editor.handle(Input::Escape);
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.selection_count(), 3);
        let primary = editor.cursor();
        editor.handle(Input::Escape);
        assert_eq!(editor.carets(), vec![primary]);
    }

    #[test]
    fn occurrences_reject_grapheme_intersections_and_gather_nonoverlapping_literals() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("aa aa aaa a\u{301}a".into())])
            .unwrap();
        editor.handle(Input::Char('v'));
        editor.handle(Input::Right);
        editor.handle(Input::Ctrl('a'));
        assert_eq!(
            editor
                .selections()
                .iter()
                .map(|range| range.start.column)
                .collect::<Vec<_>>(),
            vec![0, 3, 6]
        );
        assert_eq!(editor.cursor().column, 1);
        editor.handle(Input::Ctrl('n'));
        assert_eq!(editor.selection_count(), 3);
    }

    #[test]
    fn vertical_clones_keep_display_columns_through_tabs_wide_and_short_rows() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("a\t界z\nx\n123456z".into())])
            .unwrap();
        editor.handle(Input::End);
        editor.handle(Input::Ctrl('e'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        editor.handle(Input::Ctrl('e'));
        assert_eq!(editor.selection_count(), 3);
        assert_eq!(editor.cursor(), Cursor { row: 2, column: 6 });
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "!");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "a\t界!z\n!x\n123456!z");
        assert_eq!(editor.selection_count(), 3);
        editor.handle(Input::Escape);
        assert_eq!(editor.selection_count(), 1);
    }

    #[test]
    fn visual_clones_preserve_directed_ranges_and_motion_targets_every_range() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("abc\nabcd\nabcde".into())])
            .unwrap();
        editor.handle(Input::Right);
        editor.handle(Input::Char('v'));
        editor.handle(Input::Right);
        editor.handle(Input::Ctrl('e'));
        assert_eq!(editor.selection_count(), 2);
        editor.handle(Input::Ctrl('e'));
        assert_eq!(editor.selection_count(), 3);
        editor.handle(Input::Left);
        assert!(
            editor
                .selections()
                .iter()
                .all(|range| range.start.column == 1 && range.end.column == 2)
        );
        editor.handle(Input::Char('c'));
        type_text(&mut editor, "!");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "a!c\na!cd\na!cde");
    }

    #[test]
    fn batch_open_deduplicates_rows_and_join_uses_original_neighbor_rows() {
        for (key, expected) in [('o', "abc\n\nxyz\n"), ('O', "\nabc\n\nxyz")] {
            let mut editor = editor();
            editor
                .apply(vec![Effect::Replace("abc\nxyz".into())])
                .unwrap();
            set_carets(&mut editor, &[(0, 0), (0, 2), (1, 1)], 2);
            editor.handle(Input::Char(key));
            editor.handle(Input::Escape);
            assert_eq!(editor.context().text, expected);
            assert_eq!(editor.selection_count(), 2);
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, "abc\nxyz");
            assert_eq!(editor.selection_count(), 3);
        }
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("a\n b\n c".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 1)], 1);
        editor.handle(Input::Char('J'));
        assert_eq!(editor.context().text, "a b c");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "a\n b\n c");
        assert_eq!(editor.selection_count(), 2);
    }

    #[test]
    fn plugin_text_effects_and_invocation_are_single_primary_but_messages_are_not() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("aa\nbb\ncc".into())])
            .unwrap();
        editor.register(plugin("sample", &["sample"])).unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0), (2, 0)], 1);
        assert_eq!(editor.execute("sample").unwrap().command, "sample");
        assert_eq!(editor.selection_count(), 3);
        editor.handle(Input::Char('v'));
        let ranges = editor.selections();
        assert!(editor.apply(vec![Effect::Insert("\0".into())]).is_err());
        editor.apply(vec![Effect::Message("ok".into())]).unwrap();
        assert_eq!(editor.selections(), ranges);
        editor.apply(vec![Effect::Insert("!".into())]).unwrap();
        assert_eq!(editor.context().text, "aa\n!bb\ncc");
        assert_eq!(editor.selection_count(), 1);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "aa\nbb\ncc");
        assert_eq!(editor.selection_count(), 3);
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        assert_eq!(editor.mode(), Mode::Normal);
    }

    #[test]
    fn literal_paste_broadcasts_and_retains_separate_typing_history_for_all_carets() {
        let mut editor = editor();
        editor.apply(vec![Effect::Replace("a\nb".into())]).unwrap();
        editor.handle(Input::Ctrl('e'));
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "x");
        editor.handle(Input::Paste("界e\u{301}\r\n".into()));
        type_text(&mut editor, "z");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "x界e\u{301}\nza\nx界e\u{301}\nzb");
        for expected in ["x界e\u{301}\na\nx界e\u{301}\nb", "xa\nxb", "a\nb"] {
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, expected);
            assert_eq!(editor.selection_count(), 2);
        }
    }

    #[test]
    fn caret_motions_and_search_apply_to_all_targets_and_collapse_duplicates() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("cat cat\ncat cat".into())])
            .unwrap();
        set_carets(&mut editor, &[(0, 0), (1, 0), (1, 0)], 2);
        assert_eq!(editor.selection_count(), 2);
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        submit_search(&mut editor, "cat");
        assert_eq!(
            editor.carets(),
            vec![Cursor { row: 0, column: 4 }, Cursor { row: 1, column: 4 }]
        );
        editor.handle(Input::Char('b'));
        assert!(editor.carets().iter().all(|cursor| cursor.column == 0));
        editor.handle(Input::Up);
        assert_eq!(editor.carets(), vec![Cursor::default()]);
    }

    #[test]
    fn word_motions_distinguish_punctuation_cross_empty_lines_and_preserve_history() {
        let mut editor = editor();
        let text = "foo_bar...baz  qux\n\n   \n界e\u{301}_2 👩‍🚀!! tail";
        editor.apply(vec![Effect::Replace(text.into())]).unwrap();
        for (key, row, column) in [
            ('w', 0, 7),
            ('w', 0, 10),
            ('w', 0, 15),
            ('w', 1, 0),
            ('w', 3, 0),
            ('w', 3, 5),
            ('w', 3, 9),
            ('w', 3, 12),
            ('w', 3, 12),
            ('b', 3, 9),
            ('b', 3, 5),
            ('b', 3, 0),
            ('b', 1, 0),
            ('b', 0, 15),
            ('b', 0, 10),
            ('b', 0, 7),
            ('b', 0, 0),
            ('b', 0, 0),
            ('e', 0, 6),
            ('e', 0, 9),
            ('e', 0, 12),
            ('e', 0, 17),
            ('e', 3, 3),
            ('e', 3, 7),
            ('e', 3, 12),
            ('e', 3, 12),
        ] {
            editor.handle(Input::Char(key));
            assert_eq!(editor.cursor(), Cursor { row, column }, "{key}");
        }
        assert_eq!(editor.context().text, text);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, text);
    }

    #[test]
    fn big_word_motions_use_only_whitespace_and_handle_buffer_edges() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace(
                "foo_bar...baz  qux\n\n   \n界e\u{301}_2 👩‍🚀!! tail".into(),
            )])
            .unwrap();
        for (key, row, column) in [
            ('W', 0, 15),
            ('W', 1, 0),
            ('W', 3, 0),
            ('W', 3, 5),
            ('W', 3, 9),
            ('W', 3, 12),
            ('B', 3, 9),
            ('B', 3, 5),
            ('B', 3, 0),
            ('B', 1, 0),
            ('B', 0, 15),
            ('B', 0, 0),
            ('B', 0, 0),
            ('E', 0, 12),
            ('E', 0, 17),
            ('E', 3, 3),
            ('E', 3, 7),
            ('E', 3, 12),
            ('E', 3, 12),
        ] {
            editor.handle(Input::Char(key));
            assert_eq!(editor.cursor(), Cursor { row, column }, "{key}");
        }
        for (text, next, end) in [("", 0, 0), ("   ", 2, 2), ("word   ", 6, 3)] {
            editor.apply(vec![Effect::Replace(text.into())]).unwrap();
            editor.handle(Input::Home);
            editor.handle(Input::Char('e'));
            assert_eq!(
                editor.cursor(),
                Cursor {
                    row: 0,
                    column: end
                }
            );
            editor.handle(Input::Char('w'));
            assert_eq!(
                editor.cursor(),
                Cursor {
                    row: 0,
                    column: next
                }
            );
            editor.handle(Input::Char('b'));
            assert_eq!(editor.cursor(), Cursor { row: 0, column: 0 });
        }
        editor
            .apply(vec![Effect::Replace("one\u{2003}two\u{a0}three\n".into())])
            .unwrap();
        editor.handle(Input::Home);
        editor.handle(Input::Char('w'));
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 4 });
        editor.handle(Input::Char('w'));
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 8 });
        editor.handle(Input::Char('w'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        editor.handle(Input::Char('e'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        editor.handle(Input::Char('b'));
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 8 });
    }

    #[test]
    fn search_wraps_both_ways_and_cancel_failure_and_navigation_preserve_edits() {
        let mut editor = editor();
        let text = "zero cat\ncat cat\nCAT\n";
        editor.apply(vec![Effect::Replace(text.into())]).unwrap();
        submit_search(&mut editor, "cat");
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 5 });
        assert_eq!(editor.search_match().unwrap().end_column, 8);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 4 });
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 5 });
        editor.handle(Input::Char('N'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 4 });
        editor.handle(Input::Char('N'));
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });

        let cursor = editor.cursor();
        let active = editor.search_match();
        editor.handle(Input::Char('/'));
        type_text(&mut editor, "other界e\u{301}");
        editor.handle(Input::Backspace);
        assert_eq!(editor.command_line(), "other界");
        editor.handle(Input::Paste(":q!\n".into()));
        assert_eq!(editor.command_line(), "other界");
        editor.handle(Input::Escape);
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.cursor(), cursor);
        assert_eq!(editor.search_match(), active);
        assert!(editor.command_line().is_empty());
        submit_search(&mut editor, "");
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 4 });

        let cursor = editor.cursor();
        submit_search(&mut editor, "missing");
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.cursor(), cursor);
        assert_eq!(editor.search_match(), None);
        editor.handle(Input::Char('N'));
        assert_eq!(editor.cursor(), cursor);
        assert!(!editor.should_quit());
        assert_eq!(editor.context().text, text);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, text);
    }

    #[test]
    fn search_is_literal_overlapping_and_grapheme_safe_and_rechecks_after_edits() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("e\u{301} e 👩‍🚀 👩 aa... aaa".into())])
            .unwrap();
        submit_search(&mut editor, "e");
        assert_eq!(editor.cursor().column, 2);
        submit_search(&mut editor, "\u{301}");
        assert_eq!(editor.cursor().column, 2);
        assert_eq!(editor.search_match(), None);
        submit_search(&mut editor, "👩");
        assert_eq!(editor.cursor().column, 6);
        submit_search(&mut editor, "👩‍🚀");
        assert_eq!(editor.cursor().column, 4);
        assert_eq!(editor.search_match().unwrap().end_column, 5);
        submit_search(&mut editor, ".");
        assert_eq!(editor.cursor().column, 10);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor().column, 11);
        submit_search(&mut editor, "aa");
        assert_eq!(editor.cursor().column, 14);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor().column, 15);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor().column, 8);
        submit_search(&mut editor, "e\u{301}");
        assert_eq!(editor.cursor().column, 0);
        assert_eq!(editor.search_match().unwrap().end_column, 1);

        let active = editor.search_match();
        assert!(editor.apply(vec![Effect::Replace("\0".into())]).is_err());
        assert_eq!(editor.search_match(), active);
        editor.handle(Input::Char('x'));
        assert_eq!(editor.search_match(), None);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.search_match(), None);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.search_match(), None);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor().column, 0);
        assert_eq!(editor.search_match().unwrap().end_column, 1);
        editor
            .apply(vec![Effect::Replace("e\u{301}".into())])
            .unwrap();
        assert_eq!(editor.search_match(), None);
        editor.handle(Input::Char('n'));
        assert_eq!(editor.cursor().column, 0);
        assert_eq!(editor.search_match().unwrap().end_column, 1);
    }

    #[test]
    fn join_lines_matches_vim_spacing_and_grapheme_cursor_positions() {
        for (original, expected, column) in [
            ("alpha\n \tbeta\ntail", "alpha beta\ntail", 5),
            ("alpha  \n\tbeta", "alpha  beta", 7),
            ("alpha\t\n beta", "alpha\tbeta", 6),
            ("\n  beta", "beta", 0),
            ("alpha\n \t", "alpha", 4),
            ("\n", "", 0),
            ("alpha\n )tail", "alpha)tail", 5),
            ("Sentence.\n next", "Sentence.  next", 9),
            ("界e\u{301}\n next", "界e\u{301} next", 2),
            ("x \n\u{301}y", "x \u{301}y", 1),
        ] {
            let mut editor = editor();
            editor
                .apply(vec![Effect::Replace(original.into())])
                .unwrap();
            editor.handle(Input::Char('J'));
            assert_eq!(editor.context().text, expected);
            assert_eq!(editor.cursor(), Cursor { row: 0, column });
            assert_eq!(editor.mode(), Mode::Normal);
        }
    }

    #[test]
    fn join_is_one_undo_action_on_the_current_row_and_restores_cursor() {
        let mut editor = editor();
        let original = "above\nalpha\n  beta\nbelow";
        editor
            .apply(vec![Effect::Replace(original.into())])
            .unwrap();
        editor.handle(Input::Down);
        editor.handle(Input::Right);
        let before = editor.cursor();
        editor.handle(Input::Char('J'));
        assert_eq!(editor.context().text, "above\nalpha beta\nbelow");
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 5 });
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, original);
        assert_eq!(editor.cursor(), before);
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "above\nalpha beta\nbelow");
        editor.handle(Input::Char('x'));
        assert_eq!(editor.context().text, "above\nalphabeta\nbelow");
    }

    #[test]
    fn join_at_eof_preserves_history_and_insert_mode_j_is_literal() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("single".into())])
            .unwrap();
        editor.handle(Input::Char('u'));
        editor.handle(Input::Char('J'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "single");
        editor.handle(Input::Char('J'));
        assert_eq!(editor.context().text, "single");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('U'));
        editor.handle(Input::Char('i'));
        editor.handle(Input::Char('J'));
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "Jsingle");
    }

    #[test]
    fn uppercase_u_redoes_and_control_r_no_longer_does() {
        let mut editor = editor();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "changed");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Ctrl('r'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "changed");
    }

    #[test]
    fn uppercase_insert_keys_target_line_positions_and_preserve_undo_cursor() {
        for (original, key, expected) in [
            (" \t界e\u{301} tail", 'I', " \tX界e\u{301} tail"),
            (" \t ", 'I', " \t X"),
            ("", 'I', "X"),
            (" \t界e\u{301} tail", 'A', " \t界e\u{301} tailX"),
            ("", 'A', "X"),
        ] {
            let mut editor = editor();
            editor
                .apply(vec![Effect::Replace(original.into())])
                .unwrap();
            editor.handle(if key == 'I' { Input::End } else { Input::Right });
            let before = editor.cursor();
            editor.handle(Input::Char(key));
            assert_eq!(editor.mode(), Mode::Insert);
            type_text(&mut editor, "X");
            editor.handle(Input::Escape);
            assert_eq!(editor.context().text, expected);
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, original);
            assert_eq!(editor.cursor(), before);
            editor.handle(Input::Char('U'));
            assert_eq!(editor.context().text, expected);
        }
    }

    #[test]
    fn paste_is_ignored_in_normal_and_command_modes_without_dispatching() {
        let mut editor = editor();
        assert_eq!(editor.handle(Input::Paste(":q!\r\n".into())), None);
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.context().text, "");
        assert!(!editor.dirty());
        assert!(!editor.should_quit());

        editor.handle(Input::Char(':'));
        type_text(&mut editor, "q");
        assert_eq!(editor.handle(Input::Paste("\rq!\n\0".into())), None);
        assert_eq!(editor.mode(), Mode::Command);
        assert_eq!(editor.command_line(), "q");
        assert_eq!(editor.context().text, "");
        assert!(!editor.should_quit());
        editor.handle(Input::Enter);
        assert!(editor.should_quit());
    }

    #[test]
    fn pasted_unicode_and_newlines_are_literal_and_a_separate_undo_action() {
        let mut editor = editor();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "a");
        assert_eq!(
            editor.handle(Input::Paste("界e\u{301}\t\r\n:q!\r".into())),
            None
        );
        assert_eq!(editor.mode(), Mode::Insert);
        assert_eq!(editor.cursor(), Cursor { row: 2, column: 0 });
        type_text(&mut editor, "z");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "a界e\u{301}\t\n:q!\nz");
        assert!(!editor.should_quit());

        for expected in ["a界e\u{301}\t\n:q!\n", "a", ""] {
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, expected);
        }
        for expected in ["a", "a界e\u{301}\t\n:q!\n", "a界e\u{301}\t\n:q!\nz"] {
            editor.handle(Input::Char('U'));
            assert_eq!(editor.context().text, expected);
        }
    }

    #[test]
    fn rejected_paste_preserves_text_cursor_mode_and_pending_insert_history() {
        for text in [
            "valid prefix\ninvalid\0".to_owned(),
            "\u{1b}[31m".to_owned(),
            "x".repeat(MAX_EDIT_BYTES + 1),
        ] {
            let mut editor = editor();
            editor.handle(Input::Char('i'));
            type_text(&mut editor, "before");
            let cursor = editor.cursor();
            editor.handle(Input::Paste(text));
            assert_eq!(editor.context().text, "before");
            assert_eq!(editor.cursor(), cursor);
            assert_eq!(editor.mode(), Mode::Insert);
            assert!(
                editor.message().contains("Unsupported control character")
                    || editor.message().contains("Paste exceeds 4 MiB")
            );
            type_text(&mut editor, "after");
            editor.handle(Input::Escape);
            editor.handle(Input::Char('u'));
            assert_eq!(editor.context().text, "");
            editor.handle(Input::Char('U'));
            assert_eq!(editor.context().text, "beforeafter");
        }
    }

    #[test]
    fn insert_sessions_and_open_lines_are_single_undo_actions() {
        let mut editor = editor();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "hello\n世界");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "hello\n世界");
        assert!(editor.dirty());
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        assert!(!editor.dirty());
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "hello\n世界");
        editor.handle(Input::Char('O'));
        type_text(&mut editor, "above");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "hello\nabove\n世界");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "hello\n世界");
        editor.handle(Input::Char('o'));
        type_text(&mut editor, "below");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "hello\n世界\nbelow");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "hello\n世界");
    }

    #[test]
    fn grapheme_navigation_and_deletion_do_not_split_unicode() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("a\u{301}👩‍💻界".into())])
            .unwrap();
        editor.handle(Input::Char('l'));
        assert_eq!(editor.cursor().column, 1);
        editor.handle(Input::Char('x'));
        assert_eq!(editor.context().text, "a\u{301}界");
        editor.handle(Input::Char('0'));
        editor.handle(Input::Delete);
        assert_eq!(editor.context().text, "界");
        editor.handle(Input::Char('a'));
        type_text(&mut editor, "👨‍👩‍👧");
        editor.handle(Input::Backspace);
        assert_eq!(editor.context().text, "界");
        editor.handle(Input::Escape);
        assert_eq!(editor.cursor().column, 0);
        assert_eq!(editor.context().column, 1);
    }

    #[test]
    fn insertion_merges_combining_graphemes_and_joins_lines() {
        let mut editor = editor();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "a\u{301}\nb");
        editor.handle(Input::Home);
        editor.handle(Input::Backspace);
        assert_eq!(editor.context().text, "a\u{301}b");
        assert_eq!(editor.cursor(), Cursor { row: 0, column: 1 });
        editor.handle(Input::Enter);
        editor.handle(Input::Up);
        editor.handle(Input::End);
        editor.handle(Input::Delete);
        assert_eq!(editor.context().text, "a\u{301}b");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
    }

    #[test]
    fn cursor_is_clamped_on_short_and_empty_lines() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("long\nx\n".into())])
            .unwrap();
        editor.handle(Input::End);
        assert_eq!(editor.cursor().column, 3);
        editor.handle(Input::Down);
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        editor.handle(Input::Char('j'));
        editor.handle(Input::Char('l'));
        editor.handle(Input::Char('x'));
        assert_eq!(editor.cursor(), Cursor { row: 2, column: 0 });
        assert_eq!(editor.context().row, 3);
        editor.handle(Input::Char('i'));
        editor.handle(Input::Left);
        editor.handle(Input::Delete);
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "long\nx\n");
    }

    #[test]
    fn registry_rejects_incompatible_duplicate_and_forged_core_atomically() {
        let mut editor = editor();
        let mut feature = plugin("graphics", &["draw"]);
        feature.required_capabilities.push("graphics".into());
        assert!(editor.register(feature).is_err());
        assert!(editor.bind("normal", "g", Some("draw".into())).is_err());
        assert!(
            editor
                .register(plugin("duplicate", &["newcmd", "w"]))
                .is_err()
        );
        assert!(editor.bind("normal", "g", Some("newcmd".into())).is_err());
        assert!(
            editor
                .register(plugin("repeat", &["same", "same"]))
                .is_err()
        );
        assert!(editor.register(plugin("invalid", &["bad name"])).is_err());
        assert!(editor.register(plugin("", &["emptyname"])).is_err());
        let mut feature = plugin("forged", &["override"]);
        feature.core = true;
        assert!(editor.register(feature).is_err());
        editor.register(plugin("working", &["greet"])).unwrap();
        assert!(editor.register(plugin("working", &["different"])).is_err());
        assert!(editor.register(plugin("other", &["greet"])).is_err());
        assert!(editor.register(plugin("collision", &["plugins"])).is_err());
        editor.disable_plugin("core", "attempt");
        editor.execute("q");
        assert!(editor.should_quit());
    }

    #[test]
    fn readable_key_aliases_share_bindings_and_invalid_chords_leave_them_intact() {
        let mut editor = editor();
        editor.bind("normal", "shift+i", None).unwrap();
        editor.handle(Input::Char('I'));
        assert_eq!(editor.mode(), Mode::Normal);
        editor
            .bind("normal", "I", Some("core.insert".into()))
            .unwrap();
        editor.handle(Input::Char('I'));
        assert_eq!(editor.mode(), Mode::Insert);

        editor
            .bind("insert", "plus", Some("core.newline".into()))
            .unwrap();
        editor.bind("insert", "+", None).unwrap();
        editor.handle(Input::Char('+'));
        type_text(&mut editor, "界");
        assert_eq!(editor.lines(), &["界"]);
        editor
            .bind("insert", "plus", Some("core.newline".into()))
            .unwrap();
        editor.handle(Input::Char('+'));
        assert_eq!(editor.lines(), &["界", ""]);

        editor.bind("insert", "CTRL+I", None).unwrap();
        editor.handle(Input::Char('\t'));
        assert_eq!(editor.lines(), &["界", ""]);
        editor
            .bind("insert", "TAB", Some("core.newline".into()))
            .unwrap();
        editor.handle(Input::Ctrl('i'));
        assert_eq!(editor.lines(), &["界", "", ""]);

        editor
            .bind("insert", "shift+j", Some("core.normal".into()))
            .unwrap();
        for key in [
            "",
            "<C-r>",
            "<Esc>",
            "ctrl+",
            "+r",
            "ctrl++r",
            "ctrl+shift+j",
            "shift+tab",
            "shift+1",
            "alt+j",
            "cmd+j",
            "ctrl+界",
        ] {
            assert!(
                editor
                    .bind("insert", key, Some("core.newline".into()))
                    .is_err(),
                "{key}"
            );
        }
        editor.handle(Input::Char('J'));
        assert_eq!(editor.mode(), Mode::Normal);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.lines(), &[String::new()]);
    }

    #[test]
    fn plugin_bindings_dispatch_only_normal_mode_and_retire_with_owner() {
        let mut editor = editor();
        editor.register(plugin("greeting", &["greet"])).unwrap();
        assert!(editor.bind("insert", "g", Some("greet".into())).is_err());
        editor.bind("normal", "g", Some("greet".into())).unwrap();
        assert_eq!(
            editor.handle(Input::Char('g')),
            Some(Invocation {
                plugin: "greeting".into(),
                command: "greet".into(),
                args: String::new(),
            })
        );
        editor.handle(Input::Char('i'));
        assert_eq!(editor.handle(Input::Char('g')), None);
        assert_eq!(editor.context().text, "g");
        editor.handle(Input::Escape);
        editor.disable_plugin("greeting", "crashed\u{1b}[31m");
        assert_eq!(editor.handle(Input::Char('g')), None);
        assert!(editor.bind("normal", "g", Some("greet".into())).is_err());
        assert!(!editor.message().contains('\u{1b}'));
    }

    #[test]
    fn command_mode_dispatches_arguments_and_backspaces_whole_graphemes() {
        let mut editor = editor();
        editor.register(plugin("greeting", &["greet"])).unwrap();
        editor.handle(Input::Char(':'));
        type_text(&mut editor, "greet a\u{301}");
        editor.handle(Input::Backspace);
        assert_eq!(editor.command_line(), "greet ");
        type_text(&mut editor, "world");
        assert_eq!(
            editor.handle(Input::Enter),
            Some(Invocation {
                plugin: "greeting".into(),
                command: "greet".into(),
                args: "world".into(),
            })
        );
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(editor.command_line(), "");
        editor.handle(Input::Char(':'));
        type_text(&mut editor, "q!");
        editor.handle(Input::Escape);
        assert!(!editor.should_quit());
        assert_eq!(editor.command_line(), "");
    }

    #[test]
    fn plugin_effects_validate_before_any_mutation_and_group_undo() {
        let mut editor = editor();
        editor.set_message("unchanged");
        assert!(
            editor
                .apply(vec![
                    Effect::Insert("good".into()),
                    Effect::Message("bad\u{1b}".into())
                ])
                .is_err()
        );
        assert_eq!(editor.context().text, "");
        assert_eq!(editor.message(), "unchanged");
        assert!(!editor.dirty());
        assert!(
            editor
                .apply(vec![
                    Effect::Insert("a".repeat(MAX_EDIT_BYTES)),
                    Effect::Insert("x".into())
                ])
                .is_err()
        );
        assert_eq!(editor.context().text, "");
        editor
            .apply(vec![
                Effect::Insert("one".into()),
                Effect::Insert("\ntwo".into()),
                Effect::Message("ok".into()),
            ])
            .unwrap();
        assert_eq!(editor.context().text, "one\ntwo");
        assert_eq!(editor.message(), "ok");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "one\ntwo");
        editor
            .apply(vec![Effect::Replace("replacement".into())])
            .unwrap();
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "one\ntwo");
    }

    #[test]
    fn plugin_effect_transactions_preserve_insert_sessions() {
        let mut editor = editor();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "before");
        let cursor = editor.cursor();
        assert!(
            editor
                .apply(vec![Effect::Replace("invalid\0".into())])
                .is_err()
        );
        assert_eq!(editor.mode(), Mode::Insert);
        assert_eq!(editor.cursor(), cursor);
        type_text(&mut editor, "after");
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "a");
        editor
            .apply(vec![
                Effect::Insert("b".into()),
                Effect::Message("plugin".into()),
            ])
            .unwrap();
        type_text(&mut editor, "c");
        editor.handle(Input::Escape);
        assert_eq!(editor.context().text, "abc");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "ab");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "a");
        editor.handle(Input::Char('u'));
        assert_eq!(editor.context().text, "");
    }

    #[test]
    fn no_op_edits_preserve_redo_but_new_edits_clear_it() {
        let mut editor = editor();
        editor.apply(vec![Effect::Insert("a".into())]).unwrap();
        editor.handle(Input::Char('u'));
        editor.handle(Input::Char('i'));
        editor.handle(Input::Escape);
        editor
            .apply(vec![Effect::Message("notice".into())])
            .unwrap();
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "a");
        editor.handle(Input::Char('u'));
        editor.apply(vec![Effect::Insert("b".into())]).unwrap();
        editor.handle(Input::Char('U'));
        assert_eq!(editor.context().text, "b");
    }

    #[test]
    fn saves_preserve_empty_files_lf_trailing_newlines_and_dirty_history() {
        let directory = Directory::new();
        for (name, text) in [
            ("empty", ""),
            ("no-newline", "hello"),
            ("newline", "hello\n"),
            ("two-newlines", "hello\n\n"),
        ] {
            let path = directory.path(name);
            fs::write(&path, text).unwrap();
            let mut editor = Editor::open(Some(path.clone()), vec![]).unwrap();
            editor.set_clipboard_mode("separate").unwrap();
            editor.execute("w");
            assert_eq!(fs::read_to_string(&path).unwrap(), text);
            assert!(!editor.dirty());
        }
        let path = directory.path("new file");
        let mut editor = Editor::open(Some(path.clone()), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor.handle(Input::Char('i'));
        type_text(&mut editor, "saved\n");
        editor.handle(Input::Escape);
        editor.execute("q");
        assert!(!editor.should_quit());
        editor.execute("w");
        assert_eq!(fs::read_to_string(&path).unwrap(), "saved\n");
        assert!(!editor.dirty());
        editor.handle(Input::Char('u'));
        assert!(editor.dirty());
        editor.handle(Input::Char('U'));
        assert!(!editor.dirty());
        editor.execute("q");
        assert!(editor.should_quit());
    }

    #[test]
    fn save_as_and_failed_wq_keep_path_dirty_state_and_quit_correct() {
        let directory = Directory::new();
        let mut editor = editor();
        editor
            .apply(vec![Effect::Insert("unsaved".into())])
            .unwrap();
        editor.execute("w");
        assert!(editor.dirty());
        let bad = directory.path("absent/file");
        editor.execute(&format!("wq {}", bad.display()));
        assert!(editor.dirty());
        assert!(!editor.should_quit());
        assert_eq!(editor.path(), None);
        let path = directory.path("save as.txt");
        editor.execute(&format!("w {}", path.display()));
        assert_eq!(editor.path(), Some(path.as_path()));
        assert!(!editor.dirty());
        editor.apply(vec![Effect::Insert("new".into())]).unwrap();
        editor.execute("q!");
        assert!(editor.should_quit());
        assert_eq!(fs::read_to_string(path).unwrap(), "unsaved");
    }

    #[test]
    fn loaded_controls_are_rejected_and_cr_line_endings_are_normalized() {
        let directory = Directory::new();
        let path = directory.path("control");
        for text in ["nul\0", "escape\u{1b}[31m", "backspace\u{8}", "c1\u{85}"] {
            fs::write(&path, text).unwrap();
            assert!(
                matches!(Editor::open(Some(path.clone()), vec![]), Err(error) if error.kind() == io::ErrorKind::InvalidData)
            );
        }
        fs::write(&path, "a\t界\r\nb\rc\n").unwrap();
        let editor = Editor::open(Some(path), vec![]).unwrap();
        assert_eq!(editor.context().text, "a\t界\nb\nc\n");
        assert!(!editor.dirty());
        assert!(Editor::open(Some(directory.0.clone()), vec![]).is_err());
    }

    #[cfg(unix)]
    #[test]
    fn saves_preserve_permissions_and_reject_symlinks_without_replacing_them() {
        use std::os::unix::fs::{PermissionsExt, symlink};
        let directory = Directory::new();
        let path = directory.path("original");
        fs::write(&path, "original").unwrap();
        fs::set_permissions(&path, fs::Permissions::from_mode(0o640)).unwrap();
        let mut editor = Editor::open(Some(path.clone()), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor
            .apply(vec![Effect::Replace("changed".into())])
            .unwrap();
        editor.execute("w");
        assert_eq!(
            fs::metadata(&path).unwrap().permissions().mode() & 0o777,
            0o640
        );
        let link = directory.path("link");
        symlink(&path, &link).unwrap();
        let mut editor = Editor::open(Some(link.clone()), vec![]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor
            .apply(vec![Effect::Replace("not saved".into())])
            .unwrap();
        editor.execute("wq");
        assert!(editor.dirty());
        assert!(!editor.should_quit());
        assert!(
            fs::symlink_metadata(&link)
                .unwrap()
                .file_type()
                .is_symlink()
        );
        assert_eq!(fs::read_to_string(&path).unwrap(), "changed");
        assert_eq!(fs::read_dir(&directory.0).unwrap().count(), 2);
    }

    fn annotation(start: (usize, usize), end: (usize, usize), message: &str) -> Diagnostic {
        Diagnostic {
            start: TextPosition {
                row: start.0,
                column: start.1,
            },
            end: TextPosition {
                row: end.0,
                column: end.1,
            },
            severity: crate::plugin::DiagnosticSeverity::Warning,
            message: message.into(),
        }
    }

    #[test]
    fn annotations_are_owner_scoped_atomic_and_grapheme_bounded() {
        let mut editor = editor();
        editor
            .apply(vec![Effect::Replace("a😀e\u{301}\n".into())])
            .unwrap();
        let id = editor.buffer_id();
        let revision = editor.text_revision();
        let first = annotation((0, 1), (0, 3), "first");
        editor
            .replace_diagnostics("one", id, revision, vec![first.clone()])
            .unwrap();
        editor
            .replace_diagnostics("two", id, revision, vec![annotation((1, 0), (1, 0), "end")])
            .unwrap();
        for invalid in [
            annotation((0, 0), (0, 4), "scalar column"),
            annotation((0, 3), (0, 2), "reversed"),
            annotation((2, 0), (2, 0), "missing row"),
            annotation((0, 0), (0, 1), "control\u{1b}"),
        ] {
            assert!(
                editor
                    .replace_diagnostics("one", id, revision, vec![first.clone(), invalid])
                    .is_err()
            );
            assert_eq!(editor.diagnostics().count(), 2);
            assert_eq!(
                editor.active.diagnostics["one"].items.as_slice(),
                std::slice::from_ref(&first)
            );
        }
        assert!(
            !editor
                .replace_diagnostics(
                    "one",
                    id,
                    revision - 1,
                    vec![annotation((99, 0), (99, 0), "stale")]
                )
                .unwrap()
        );
        assert!(
            !editor
                .replace_diagnostics("one", 999, revision, vec![first.clone()])
                .unwrap()
        );
        editor.active.targets = vec![Target::caret(Cursor { row: 0, column: 1 })];
        assert_eq!(editor.diagnostic_at_cursor().unwrap().message, "first");
        editor.active.targets = vec![Target::caret(Cursor { row: 1, column: 0 })];
        assert_eq!(editor.diagnostic_at_cursor().unwrap().message, "end");
        editor.clear_plugin_diagnostics("one");
        assert_eq!(editor.diagnostics().count(), 1);
    }

    #[test]
    fn annotations_do_not_split_typing_undo_and_clear_on_text_change() {
        let mut editor = editor();
        editor.handle(Input::Char('i'));
        editor.handle(Input::Char('a'));
        let revision = editor.text_revision();
        editor
            .replace_diagnostics(
                "one",
                editor.buffer_id(),
                revision,
                vec![annotation((0, 0), (0, 1), "typed")],
            )
            .unwrap();
        assert!(editor.active.insert_start.is_some());
        assert!(editor.active.undo.is_empty());
        editor.handle(Input::Char('b'));
        assert_eq!(editor.diagnostics().count(), 0);
        editor.handle(Input::Escape);
        editor.handle(Input::Char('u'));
        assert_eq!(editor.lines(), [""]);
        assert!(editor.active.undo.is_empty());
    }

    #[test]
    fn navigation_reuses_dirty_hidden_text_and_failure_preserves_source() {
        let directory = Directory::new();
        let source = directory.path("source");
        let target = directory.path("target");
        fs::write(&source, "source").unwrap();
        fs::write(&target, "a😀e\u{301}\n").unwrap();
        let mut editor = Editor::open(Some(source.clone()), vec!["text".into()]).unwrap();
        editor.set_clipboard_mode("separate").unwrap();
        editor.execute(&format!("edit {}", target.display()));
        editor
            .apply(vec![Effect::Replace("dirty😀e\u{301}\n".into())])
            .unwrap();
        let target_id = editor.buffer_id();
        editor.execute("buffer 1");
        editor.handle(Input::Char('i'));
        editor.handle(Input::Char('!'));
        let before = editor.context().text;
        let cursor = editor.cursor();
        let undo = editor.active.undo.len();
        assert!(
            editor
                .navigate_to(
                    directory.path("missing"),
                    TextPosition { row: 0, column: 0 }
                )
                .is_err()
        );
        assert_eq!(editor.buffer_id(), 1);
        assert_eq!(editor.context().text, before);
        assert_eq!(editor.cursor(), cursor);
        assert_eq!(editor.mode(), Mode::Insert);
        assert_eq!(editor.active.undo.len(), undo);
        assert!(editor.active.insert_start.is_some());
        editor
            .navigate_to(
                target,
                TextPosition {
                    row: 99,
                    column: 99,
                },
            )
            .unwrap();
        assert_eq!(editor.buffer_id(), target_id);
        assert_eq!(editor.lines(), ["dirty😀e\u{301}", ""]);
        assert_eq!(editor.buffer_count(), 2);
        assert_eq!(editor.cursor(), Cursor { row: 1, column: 0 });
        assert_eq!(editor.mode(), Mode::Normal);
        assert_eq!(fs::read_to_string(source).unwrap(), "source");
    }
}