mathtex-editor-keymap 0.1.0

//! The default Hypatia keymap maps host input to primitive `Command`s.
#![allow(dead_code)]

use std::collections::HashMap;

use mathtex_editor_core::command::{Command, Dir};
use mathtex_editor_core::model::{FracStyle, MathClass, MatrixEnv, ScriptSlot, Symbol};

/// A normalized key event from the host matching browser `KeyboardEvent` fields.
#[derive(Debug, Clone)]
pub struct KeyInput {
    /// The `KeyboardEvent.key` value such as `"a"`, `"/"`, `"ArrowLeft"`, or `"Backspace"`.
    pub key: String,
    /// Whether the shift modifier is active.
    pub shift: bool,
    /// Whether the control modifier is active.
    pub ctrl: bool,
    /// Whether the alt modifier is active.
    pub alt: bool,
    /// Whether the meta modifier is active.
    pub meta: bool,
}

/// Input state for character autocorrect, word autoconvert, and host word shortcuts.
#[derive(Debug, Default)]
pub struct Keymap {
    last_char: Option<char>,
    word: String,
    word_overrides: HashMap<String, Vec<Command>>,
}

impl Keymap {
    /// Create an empty keymap with the built in shortcuts.
    pub fn new() -> Self {
        Self::default()
    }

    /// Register a user word shortcut so `word` plus space expands to `commands`.
    pub fn define_word(&mut self, word: impl Into<String>, commands: Vec<Command>) {
        self.word_overrides.insert(word.into(), commands);
    }

    /// Remove a previously registered word shortcut while leaving built ins unaffected.
    pub fn undefine_word(&mut self, word: &str) {
        self.word_overrides.remove(word);
    }

    /// Return words the keymap can expand for a `\` command popover.
    pub fn entries(&self) -> Vec<KeymapEntry<'_>> {
        let mut out: Vec<KeymapEntry<'_>> = Vec::new();
        for w in self.word_overrides.keys() {
            out.push(KeymapEntry { word: w.as_str(), label: w.as_str() });
        }
        for s in CATALOG {
            if !self.word_overrides.contains_key(s.word) {
                out.push(KeymapEntry { word: s.word, label: s.label });
            }
        }
        for &op in OPERATORS {
            if !self.word_overrides.contains_key(op) {
                out.push(KeymapEntry { word: op, label: op });
            }
        }
        out
    }

    /// Translate a key event into zero or more editor commands.
    pub fn map_key(&mut self, input: &KeyInput) -> Vec<Command> {
        let named = match input.key.as_str() {
            "ArrowLeft" => Some(dir_cmd(Dir::Left, input.shift)),
            "ArrowRight" => Some(dir_cmd(Dir::Right, input.shift)),
            "ArrowUp" => Some(dir_cmd(Dir::Up, input.shift)),
            "ArrowDown" => Some(dir_cmd(Dir::Down, input.shift)),
            "Home" => Some(Command::MoveLineStart),
            "End" => Some(Command::MoveLineEnd),
            "Tab" => Some(if input.shift {
                Command::ShiftTab
            } else {
                Command::Tab
            }),
            "Backspace" => Some(Command::DeleteBackward),
            "Delete" => Some(Command::DeleteForward),
            // Enter confirms a pending Backspace swap menu or behaves like Collapse.
            "Enter" => Some(Command::Confirm),
            "Escape" => Some(Command::Collapse), // host decides; reset state
            _ => None,
        };
        if let Some(cmd) = named {
            self.reset();
            return if matches!(cmd, Command::Collapse) {
                vec![cmd] // benign reset, host may also act
            } else {
                vec![cmd]
            };
        }

        if input.ctrl || input.meta {
            self.reset();
            return match input.key.as_str() {
                "a" | "A" => vec![Command::SelectAll],
                _ => vec![],
            };
        }

        match single_char(&input.key) {
            Some(ch) => self.map_char(ch),
            None => vec![],
        }
    }

    /// Translate committed text by replaying it through `map_char` one character at a time.
    pub fn map_text(&mut self, text: &str) -> Vec<Command> {
        self.reset();
        text.chars().flat_map(|ch| self.map_char(ch)).collect()
    }

    fn reset(&mut self) {
        self.last_char = None;
        self.word.clear();
    }

    fn map_char(&mut self, ch: char) -> Vec<Command> {
        // Space converts the preceding word or is swallowed.
        if ch == ' ' {
            return self.flush_word();
        }
        // Two character symbol autocorrect.
        if let Some(prev) = self.last_char {
            if let Some(repl) = two_char(prev, ch) {
                self.reset();
                return vec![Command::DeleteBackward, insert(repl)];
            }
        }
        self.last_char = Some(ch);
        if ch.is_ascii_alphabetic() {
            self.word.push(ch);
        } else {
            self.word.clear();
        }
        match ch {
            '/' => vec![Command::InsertFraction(FracStyle::Bar)],
            '^' => vec![Command::InsertScript(ScriptSlot::Sup)],
            '_' => vec![Command::InsertScript(ScriptSlot::Sub)],
            '(' => vec![delims('(', ')')],
            '[' => vec![delims('[', ']')],
            '{' => vec![delims('{', '}')],
            '|' => vec![delims('|', '|')],
            '\'' => vec![Command::InsertScript(ScriptSlot::Sup), insert("\\prime")],
            '*' => vec![insert("\\cdot")],
            c => vec![Command::InsertAtom(atom(c))],
        }
    }

    /// Convert the buffered word on space or swallow the space if the word is unknown.
    fn flush_word(&mut self) -> Vec<Command> {
        self.last_char = None;
        let word = std::mem::take(&mut self.word);
        if word.is_empty() {
            return vec![];
        }
        match self.lookup(&word) {
            Some(mut cmds) => {
                let mut out = vec![Command::DeleteBackward; word.chars().count()];
                out.append(&mut cmds);
                out
            }
            None => vec![],
        }
    }

    /// Resolve a word using host overrides, catalog entries, then upright operators.
    fn lookup(&self, word: &str) -> Option<Vec<Command>> {
        if let Some(cmds) = self.word_overrides.get(word) {
            return Some(cmds.clone());
        }
        if let Some(s) = CATALOG.iter().find(|s| s.word == word) {
            return Some(s.insert.commands());
        }
        if OPERATORS.contains(&word) {
            return Some(vec![named_atom(&format!("\\{word}"))]);
        }
        None
    }

    /// Resolve a word directly for a host rendered `\` command palette.
    pub fn commands_for_word(&self, word: &str) -> Option<Vec<Command>> {
        self.lookup(word)
    }
}

/// The insertion shape shared by catalog entries.
#[derive(Debug, Clone, Copy)]
enum Insertion {
    /// A named atom whose class comes from [`class_of_latex`].
    Symbol(&'static str),
    Fraction(FracStyle),
    Root,
    /// A big operator with stacked limit slots.
    BigOperator(&'static str),
    /// A matrix like environment with a fixed `rows` x `cols` grid.
    Matrix(MatrixEnv, usize, usize),
}

impl Insertion {
    fn commands(self) -> Vec<Command> {
        match self {
            Insertion::Symbol(latex) => vec![named_atom(latex)],
            Insertion::Fraction(style) => vec![Command::InsertFraction(style)],
            Insertion::Root => vec![Command::InsertSqrt],
            Insertion::BigOperator(latex) => vec![Command::InsertBigOp(Symbol {
                latex: latex.to_string(),
                class: MathClass::Op,
            })],
            Insertion::Matrix(env, rows, cols) => vec![Command::InsertMatrix { env, rows, cols }],
        }
    }
}

/// One catalog row with a trigger word, display label, and insertion.
#[derive(Debug, Clone, Copy)]
struct Shortcut {
    word: &'static str,
    label: &'static str,
    insert: Insertion,
}

/// A popover row with a trigger word and display label.
#[derive(Debug, Clone, Copy)]
pub struct KeymapEntry<'a> {
    /// The shortcut trigger word.
    pub word: &'a str,
    /// The label shown for the shortcut.
    pub label: &'a str,
}

/// Terse constructor for a plain named symbol entry whose label defaults to the word.
const fn sym(word: &'static str, latex: &'static str) -> Shortcut {
    Shortcut { word, label: word, insert: Insertion::Symbol(latex) }
}

/// Terse constructor for a big operator entry whose label defaults to the word.
const fn bigop(word: &'static str, latex: &'static str) -> Shortcut {
    Shortcut { word, label: word, insert: Insertion::BigOperator(latex) }
}

/// The built in word to insertion catalog for structures, big operators, and named symbols.
const CATALOG: &[Shortcut] = &[
    // structures
    Shortcut { word: "frac", label: "fraction", insert: Insertion::Fraction(FracStyle::Bar) },
    Shortcut { word: "dfrac", label: "display fraction", insert: Insertion::Fraction(FracStyle::Display) },
    Shortcut { word: "binom", label: "binomial", insert: Insertion::Fraction(FracStyle::Binom) },
    Shortcut { word: "sqrt", label: "square root", insert: Insertion::Root },
    Shortcut { word: "root", label: "root", insert: Insertion::Root },
    // big operators with stacked limits
    bigop("sum", "\\sum"),
    bigop("prod", "\\prod"),
    bigop("coprod", "\\coprod"),
    bigop("int", "\\int"),
    bigop("iint", "\\iint"),
    bigop("iiint", "\\iiint"),
    bigop("oint", "\\oint"),
    bigop("bigcup", "\\bigcup"),
    bigop("bigcap", "\\bigcap"),
    bigop("bigsqcup", "\\bigsqcup"),
    bigop("biguplus", "\\biguplus"),
    bigop("bigoplus", "\\bigoplus"),
    bigop("bigotimes", "\\bigotimes"),
    bigop("bigodot", "\\bigodot"),
    bigop("bigvee", "\\bigvee"),
    bigop("bigwedge", "\\bigwedge"),
    // matrices
    Shortcut { word: "pmatrix", label: "matrix (parentheses)", insert: Insertion::Matrix(MatrixEnv::Pmatrix, 2, 2) },
    Shortcut { word: "bmatrix", label: "matrix (brackets)", insert: Insertion::Matrix(MatrixEnv::Bmatrix, 2, 2) },
    Shortcut { word: "vmatrix", label: "matrix (bars / determinant)", insert: Insertion::Matrix(MatrixEnv::Vmatrix, 2, 2) },
    Shortcut { word: "matrix", label: "matrix (plain)", insert: Insertion::Matrix(MatrixEnv::Matrix, 2, 2) },
    Shortcut { word: "cases", label: "cases", insert: Insertion::Matrix(MatrixEnv::Cases, 2, 2) },
    Shortcut { word: "aligned", label: "aligned equations", insert: Insertion::Matrix(MatrixEnv::Aligned, 2, 2) },
    Shortcut { word: "align", label: "aligned equations", insert: Insertion::Matrix(MatrixEnv::Aligned, 2, 2) },
    Shortcut { word: "array", label: "array", insert: Insertion::Matrix(MatrixEnv::Array, 2, 2) },
    // lower greek
    sym("alpha", "\\alpha"),
    sym("beta", "\\beta"),
    sym("gamma", "\\gamma"),
    sym("delta", "\\delta"),
    sym("epsilon", "\\epsilon"),
    sym("varepsilon", "\\varepsilon"),
    sym("zeta", "\\zeta"),
    sym("eta", "\\eta"),
    sym("theta", "\\theta"),
    sym("vartheta", "\\vartheta"),
    sym("iota", "\\iota"),
    sym("kappa", "\\kappa"),
    sym("lambda", "\\lambda"),
    sym("mu", "\\mu"),
    sym("nu", "\\nu"),
    sym("xi", "\\xi"),
    sym("pi", "\\pi"),
    sym("rho", "\\rho"),
    sym("sigma", "\\sigma"),
    sym("tau", "\\tau"),
    sym("upsilon", "\\upsilon"),
    sym("phi", "\\phi"),
    sym("varphi", "\\varphi"),
    sym("chi", "\\chi"),
    sym("psi", "\\psi"),
    sym("omega", "\\omega"),
    // upper greek
    sym("Gamma", "\\Gamma"),
    sym("Delta", "\\Delta"),
    sym("Theta", "\\Theta"),
    sym("Lambda", "\\Lambda"),
    sym("Xi", "\\Xi"),
    sym("Pi", "\\Pi"),
    sym("Sigma", "\\Sigma"),
    sym("Phi", "\\Phi"),
    sym("Psi", "\\Psi"),
    sym("Omega", "\\Omega"),
    // calculus and misc symbols
    sym("infty", "\\infty"),
    sym("infinity", "\\infty"),
    sym("partial", "\\partial"),
    sym("nabla", "\\nabla"),
    // The differential is upright `\mathrm{d}` for integrals and derivatives.
    Shortcut { word: "dd", label: "differential", insert: Insertion::Symbol("\\mathrm{d}") },
    // binary operators and relations
    sym("pm", "\\pm"),
    sym("mp", "\\mp"),
    sym("times", "\\times"),
    sym("div", "\\div"),
    sym("cdot", "\\cdot"),
    sym("ast", "\\ast"),
    sym("star", "\\star"),
    sym("leq", "\\leq"),
    sym("le", "\\leq"),
    sym("geq", "\\geq"),
    sym("ge", "\\geq"),
    sym("neq", "\\neq"),
    sym("ne", "\\neq"),
    sym("approx", "\\approx"),
    sym("equiv", "\\equiv"),
    sym("cong", "\\cong"),
    sym("sim", "\\sim"),
    sym("propto", "\\propto"),
    sym("to", "\\to"),
    sym("gets", "\\gets"),
    sym("implies", "\\implies"),
    sym("iff", "\\iff"),
    // sets and logic
    sym("in", "\\in"),
    sym("notin", "\\notin"),
    sym("subset", "\\subset"),
    sym("subseteq", "\\subseteq"),
    sym("supset", "\\supset"),
    sym("cup", "\\cup"),
    sym("cap", "\\cap"),
    sym("emptyset", "\\emptyset"),
    sym("forall", "\\forall"),
    sym("exists", "\\exists"),
    sym("neg", "\\neg"),
    sym("land", "\\land"),
    sym("lor", "\\lor"),
    // dots, arrows, and misc symbols
    sym("cdots", "\\cdots"),
    sym("ldots", "\\ldots"),
    sym("dots", "\\dots"),
    sym("rightarrow", "\\rightarrow"),
    sym("leftarrow", "\\leftarrow"),
    sym("angle", "\\angle"),
    sym("perp", "\\perp"),
    sym("parallel", "\\parallel"),
];

fn dir_cmd(dir: Dir, shift: bool) -> Command {
    if shift {
        Command::Extend(dir)
    } else {
        Command::Move(dir)
    }
}

fn delims(open: char, close: char) -> Command {
    Command::InsertDelimiters { open, close }
}

fn single_char(key: &str) -> Option<char> {
    let mut it = key.chars();
    match (it.next(), it.next()) {
        (Some(c), None) => Some(c),
        _ => None,
    }
}

fn atom(c: char) -> Symbol {
    Symbol::from_char(c) // escapes TeX specials like %, $, ~, and \
}

fn insert(latex: &str) -> Command {
    Command::InsertAtom(Symbol {
        latex: latex.to_string(),
        class: class_of_latex(latex),
    })
}

fn named_atom(latex: &str) -> Command {
    insert(latex)
}

fn class_of_latex(latex: &str) -> MathClass {
    if let Some(name) = latex.strip_prefix('\\') {
        if OPERATORS.contains(&name) {
            return MathClass::Op;
        }
    }
    match latex {
        "\\leq" | "\\geq" | "\\neq" | "\\equiv" | "\\approx" | "\\cong" | "\\to" | "\\sim"
        | "\\implies" | "\\iff" | "\\gets" | "\\propto" | "\\in" | "\\notin" | "\\subset"
        | "\\subseteq" | "\\supset" | "\\rightarrow" | "\\leftarrow" | "\\Rightarrow"
        | "\\Leftarrow" | "\\perp" | "\\parallel" => MathClass::Rel,
        "\\pm" | "\\mp" | "\\times" | "\\div" | "\\cdot" | "\\ast" | "\\star" | "\\cup"
        | "\\cap" => MathClass::Bin,
        _ => MathClass::Ord,
    }
}

/// The Hypatia two character autoconvert table.
fn two_char(a: char, b: char) -> Option<&'static str> {
    Some(match (a, b) {
        ('<', '=') => "\\leq",
        ('>', '=') => "\\geq",
        ('!', '=') => "\\neq",
        ('=', '=') => "\\equiv",
        ('=', '~') => "\\cong",
        ('~', '~') => "\\approx",
        ('-', '>') => "\\to",
        ('<', '-') => "\\gets",
        ('=', '>') => "\\implies",
        ('+', '-') => "\\pm",
        ('-', '+') => "\\mp",
        (':', '-') => "\\div",
        ('<', '<') => "\\langle",
        ('>', '>') => "\\rangle",
        _ => return None,
    })
}

/// Named operators that render upright and feed word lookup.
const OPERATORS: &[&str] = &[
    "sin", "cos", "tan", "cot", "sec", "csc", "sinh", "cosh", "tanh", "arcsin", "arccos", "arctan",
    "log", "ln", "exp", "lim", "max", "min", "sup", "inf", "gcd", "det", "dim", "ker", "arg", "deg",
    "hom",
];

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

    fn k(key: &str) -> KeyInput {
        KeyInput {
            key: key.into(),
            shift: false,
            ctrl: false,
            alt: false,
            meta: false,
        }
    }

    fn sym(latex: &str, class: MathClass) -> Command {
        Command::InsertAtom(Symbol {
            latex: latex.into(),
            class,
        })
    }

    #[test]
    fn arrows_and_shift() {
        let mut km = Keymap::new();
        assert_eq!(km.map_key(&k("ArrowLeft")), vec![Command::Move(Dir::Left)]);
        let mut shifted = k("ArrowRight");
        shifted.shift = true;
        assert_eq!(km.map_key(&shifted), vec![Command::Extend(Dir::Right)]);
    }

    #[test]
    fn structure_keys() {
        let mut km = Keymap::new();
        assert_eq!(
            km.map_key(&k("/")),
            vec![Command::InsertFraction(FracStyle::Bar)]
        );
        assert_eq!(
            km.map_key(&k("(")),
            vec![Command::InsertDelimiters {
                open: '(',
                close: ')'
            }]
        );
    }

    #[test]
    fn autocorrect_two_char() {
        let mut km = Keymap::new();
        assert_eq!(km.map_key(&k("<")), vec![sym("<", MathClass::Rel)]);
        assert_eq!(
            km.map_key(&k("=")),
            vec![Command::DeleteBackward, sym("\\leq", MathClass::Rel)]
        );
    }

    #[test]
    fn implies_arrow() {
        let mut km = Keymap::new();
        km.map_key(&k("="));
        assert_eq!(
            km.map_key(&k(">")),
            vec![Command::DeleteBackward, sym("\\implies", MathClass::Rel)]
        );
    }

    #[test]
    fn word_on_space_converts() {
        let mut km = Keymap::new();
        km.map_key(&k("p"));
        km.map_key(&k("i"));
        assert_eq!(
            km.map_key(&k(" ")),
            vec![
                Command::DeleteBackward,
                Command::DeleteBackward,
                sym("\\pi", MathClass::Ord)
            ]
        );
    }

    /// `map_text` must replay every character through `map_char` so shortcuts still fire.
    #[test]
    fn map_text_replays_word_lookup_fraction_and_autocorrect() {
        // `map_text` queues inserts before the space replacement, matching typed input order.
        let mut km = Keymap::new();
        assert_eq!(
            km.map_text("pi "),
            vec![
                sym("p", MathClass::Ord),
                sym("i", MathClass::Ord),
                Command::DeleteBackward,
                Command::DeleteBackward,
                sym("\\pi", MathClass::Ord)
            ]
        );

        let mut km = Keymap::new();
        assert_eq!(
            km.map_text("a/b"),
            vec![
                sym("a", MathClass::Ord),
                Command::InsertFraction(FracStyle::Bar),
                sym("b", MathClass::Ord),
            ]
        );

        let mut km = Keymap::new();
        assert_eq!(
            km.map_text("a<=b"),
            vec![
                sym("a", MathClass::Ord),
                sym("<", MathClass::Rel),
                Command::DeleteBackward,
                sym("\\leq", MathClass::Rel),
                sym("b", MathClass::Ord),
            ]
        );
    }

    #[test]
    fn operator_word_converts() {
        let mut km = Keymap::new();
        for c in ["s", "i", "n"] {
            km.map_key(&k(c));
        }
        assert_eq!(
            km.map_key(&k(" ")),
            vec![
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                sym("\\sin", MathClass::Op)
            ]
        );
    }

    #[test]
    fn bare_space_inserts_nothing() {
        let mut km = Keymap::new();
        assert_eq!(km.map_key(&k(" ")), Vec::<Command>::new());
    }

    #[test]
    fn unknown_word_then_space_is_dropped() {
        let mut km = Keymap::new();
        km.map_key(&k("x"));
        km.map_key(&k("y"));
        assert_eq!(km.map_key(&k(" ")), Vec::<Command>::new());
    }

    #[test]
    fn plain_letter_inserts_atom() {
        let mut km = Keymap::new();
        assert_eq!(km.map_key(&k("a")), vec![sym("a", MathClass::Ord)]);
    }

    #[test]
    fn structure_word_builds_bigop() {
        let mut km = Keymap::new();
        for c in ["s", "u", "m"] {
            km.map_key(&k(c));
        }
        assert_eq!(
            km.map_key(&k(" ")),
            vec![
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::InsertBigOp(Symbol {
                    latex: "\\sum".into(),
                    class: MathClass::Op
                }),
            ]
        );
    }

    #[test]
    fn structure_word_builds_fraction() {
        let mut km = Keymap::new();
        for c in ["f", "r", "a", "c"] {
            km.map_key(&k(c));
        }
        assert_eq!(
            km.map_key(&k(" ")),
            vec![
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::InsertFraction(FracStyle::Bar),
            ]
        );
    }

    #[test]
    fn structure_word_builds_pmatrix() {
        let mut km = Keymap::new();
        for c in ["p", "m", "a", "t", "r", "i", "x"] {
            km.map_key(&k(c));
        }
        assert_eq!(
            km.map_key(&k(" ")),
            vec![
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::InsertMatrix {
                    env: MatrixEnv::Pmatrix,
                    rows: 2,
                    cols: 2
                },
            ]
        );
    }

    #[test]
    fn structure_word_builds_cases() {
        let mut km = Keymap::new();
        for c in ["c", "a", "s", "e", "s"] {
            km.map_key(&k(c));
        }
        assert_eq!(
            km.map_key(&k(" ")),
            vec![
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::DeleteBackward,
                Command::InsertMatrix {
                    env: MatrixEnv::Cases,
                    rows: 2,
                    cols: 2
                },
            ]
        );
    }

    #[test]
    fn host_defined_word_overrides_and_inserts() {
        let mut km = Keymap::new();
        km.define_word("RR", vec![sym("\\mathbb{R}", MathClass::Ord)]);
        for c in ["R", "R"] {
            km.map_key(&k(c));
        }
        assert_eq!(
            km.map_key(&k(" ")),
            vec![
                Command::DeleteBackward,
                Command::DeleteBackward,
                sym("\\mathbb{R}", MathClass::Ord)
            ]
        );
    }

    #[test]
    fn override_shadows_builtin() {
        let mut km = Keymap::new();
        km.define_word("pi", vec![sym("\\varpi", MathClass::Ord)]);
        for c in ["p", "i"] {
            km.map_key(&k(c));
        }
        assert_eq!(
            km.map_key(&k(" ")).last().cloned(),
            Some(sym("\\varpi", MathClass::Ord))
        );
    }

    #[test]
    fn entries_are_enumerable_for_popover() {
        let km = Keymap::new();
        let words: Vec<&str> = km.entries().iter().map(|e| e.word).collect();
        assert!(words.contains(&"frac")); // structure
        assert!(words.contains(&"sum")); // big operator
        assert!(words.contains(&"alpha")); // symbol
        assert!(words.contains(&"sin")); // operator
    }
}