MacOS Style emacs mode for Codemirror 5

emacs_mini.js

// CodeMirror, copyright (c) by Marijn Haverbeke and others
// Distributed under an MIT license: https://codemirror.net/5/LICENSE
// Modified by Matthew Rathbone
import CodeMirror from 'codemirror'

let setupDone = false

export function setupEmacsMini() {
  "use strict";

  if (setupDone) return;

  var cmds = CodeMirror.commands;
  var Pos = CodeMirror.Pos;
  function posEq(a, b) { return a.line == b.line && a.ch == b.ch; }

  // Kill 'ring'

  var killRing = [];
  function addToRing(str) {
    killRing.push(str);
    if (killRing.length > 50) killRing.shift();
  }
  function growRingTop(str) {
    if (!killRing.length) return addToRing(str);
    killRing[killRing.length - 1] += str;
  }
  function getFromRing(n) { return killRing[killRing.length - (n ? Math.min(n, 1) : 1)] || ""; }
  function popFromRing() { if (killRing.length > 1) killRing.pop(); return getFromRing(); }

  var lastKill = null;

  // Internal generic kill function, used by several mapped kill "family" functions.
  function _kill(cm, from, to, ring, text) {
    if (text == null) text = cm.getRange(from, to);

    if (ring == "grow" && lastKill && lastKill.cm == cm && posEq(from, lastKill.pos) && cm.isClean(lastKill.gen))
      growRingTop(text);
    else if (ring !== false)
      addToRing(text);
    cm.replaceRange("", from, to, "+delete");

    if (ring == "grow") lastKill = {cm: cm, pos: from, gen: cm.changeGeneration()};
    else lastKill = null;
  }

  // Boundaries of various units

  function byChar(cm, pos, dir) {
    return cm.findPosH(pos, dir, "char", true);
  }

  function byWord(cm, pos, dir) {
    return cm.findPosH(pos, dir, "word", true);
  }

  function byLine(cm, pos, dir) {
    return cm.findPosV(pos, dir, "line", cm.doc.sel.goalColumn);
  }

  function byPage(cm, pos, dir) {
    return cm.findPosV(pos, dir, "page", cm.doc.sel.goalColumn);
  }

  function byParagraph(cm, pos, dir) {
    var no = pos.line, line = cm.getLine(no);
    var sawText = /\S/.test(dir < 0 ? line.slice(0, pos.ch) : line.slice(pos.ch));
    var fst = cm.firstLine(), lst = cm.lastLine();
    for (;;) {
      no += dir;
      if (no < fst || no > lst)
        return cm.clipPos(Pos(no - dir, dir < 0 ? 0 : null));
      line = cm.getLine(no);
      var hasText = /\S/.test(line);
      if (hasText) sawText = true;
      else if (sawText) return Pos(no, 0);
    }
  }

  function bySentence(cm, pos, dir) {
    var line = pos.line, ch = pos.ch;
    var text = cm.getLine(pos.line), sawWord = false;
    for (;;) {
      var next = text.charAt(ch + (dir < 0 ? -1 : 0));
      if (!next) { // End/beginning of line reached
        if (line == (dir < 0 ? cm.firstLine() : cm.lastLine())) return Pos(line, ch);
        text = cm.getLine(line + dir);
        if (!/\S/.test(text)) return Pos(line, ch);
        line += dir;
        ch = dir < 0 ? text.length : 0;
        continue;
      }
      if (sawWord && /[!?.]/.test(next)) return Pos(line, ch + (dir > 0 ? 1 : 0));
      if (!sawWord) sawWord = /\w/.test(next);
      ch += dir;
    }
  }

  function byExpr(cm, pos, dir) {
    var wrap;
    if (cm.findMatchingBracket && (wrap = cm.findMatchingBracket(pos, {strict: true}))
        && wrap.match && (wrap.forward ? 1 : -1) == dir)
      return dir > 0 ? Pos(wrap.to.line, wrap.to.ch + 1) : wrap.to;

    for (var first = true;; first = false) {
      var token = cm.getTokenAt(pos);
      var after = Pos(pos.line, dir < 0 ? token.start : token.end);
      if (first && dir > 0 && token.end == pos.ch || !/\w/.test(token.string)) {
        var newPos = cm.findPosH(after, dir, "char");
        if (posEq(after, newPos)) return pos;
        else pos = newPos;
      } else {
        return after;
      }
    }
  }

  // Prefixes (only crudely supported)

  function getPrefix(cm, precise) {
    var digits = cm.state.emacsPrefix;
    if (!digits) return precise ? null : 1;
    clearPrefix(cm);
    return digits == "-" ? -1 : Number(digits);
  }

  function repeated(cmd) {
    var f = typeof cmd == "string" ? function(cm) { cm.execCommand(cmd); } : cmd;
    return function(cm) {
      var prefix = getPrefix(cm);
      f(cm);
      for (var i = 1; i < prefix; ++i) f(cm);
    };
  }

  function findEnd(cm, pos, by, dir) {
    var prefix = getPrefix(cm);
    if (prefix < 0) { dir = -dir; prefix = -prefix; }
    for (var i = 0; i < prefix; ++i) {
      var newPos = by(cm, pos, dir);
      if (posEq(newPos, pos)) break;
      pos = newPos;
    }
    return pos;
  }

  function move(by, dir) {
    var f = function(cm) {
      cm.extendSelection(findEnd(cm, cm.getCursor(), by, dir));
    };
    f.motion = true;
    return f;
  }

  function killTo(cm, by, dir, ring) {
    var selections = cm.listSelections(), cursor;
    var i = selections.length;
    while (i--) {
      cursor = selections[i].head;
      _kill(cm, cursor, findEnd(cm, cursor, by, dir), ring);
    }
  }

  function _killRegion(cm, ring) {
    if (cm.somethingSelected()) {
      var selections = cm.listSelections(), selection;
      var i = selections.length;
      while (i--) {
        selection = selections[i];
        _kill(cm, selection.anchor, selection.head, ring);
      }
      return true;
    }
  }

  function addPrefix(cm, digit) {
    if (cm.state.emacsPrefix) {
      if (digit != "-") cm.state.emacsPrefix += digit;
      return;
    }
    // Not active yet
    cm.state.emacsPrefix = digit;
    cm.on("keyHandled", maybeClearPrefix);
    cm.on("inputRead", maybeDuplicateInput);
  }

  var prefixPreservingKeys = {"Alt-G": true, "Ctrl-X": true, "Ctrl-Q": true, "Ctrl-U": true};

  function maybeClearPrefix(cm, arg) {
    if (!cm.state.emacsPrefixMap && !prefixPreservingKeys.hasOwnProperty(arg))
      clearPrefix(cm);
  }

  function clearPrefix(cm) {
    cm.state.emacsPrefix = null;
    cm.off("keyHandled", maybeClearPrefix);
    cm.off("inputRead", maybeDuplicateInput);
  }

  function maybeDuplicateInput(cm, event) {
    var dup = getPrefix(cm);
    if (dup > 1 && event.origin == "+input") {
      var one = event.text.join("\n"), txt = "";
      for (var i = 1; i < dup; ++i) txt += one;
      cm.replaceSelection(txt);
    }
  }

  function maybeRemovePrefixMap(cm, arg) {
    if (typeof arg == "string" && (/^\d$/.test(arg) || arg == "Ctrl-U")) return;
    cm.removeKeyMap(prefixMap);
    cm.state.emacsPrefixMap = false;
    cm.off("keyHandled", maybeRemovePrefixMap);
    cm.off("inputRead", maybeRemovePrefixMap);
  }

  // Utilities

  cmds.setMark = function (cm) {
    cm.setCursor(cm.getCursor());
    cm.setExtending(!cm.getExtending());
    cm.on("change", function() { cm.setExtending(false); });
  }

  function clearMark(cm) {
    cm.setExtending(false);
    cm.setCursor(cm.getCursor());
  }

  function makePrompt(msg) {
    var fragment = document.createDocumentFragment();
    var input = document.createElement("input");
    input.setAttribute("type", "text");
    input.style.width = "10em";
    fragment.appendChild(document.createTextNode(msg + ": "));
    fragment.appendChild(input);
    return fragment;
  }

  function getInput(cm, msg, f) {
    if (cm.openDialog)
      cm.openDialog(makePrompt(msg), f, {bottom: true});
    else
      f(prompt(msg, ""));
  }

  function operateOnWord(cm, op) {
    var start = cm.getCursor(), end = cm.findPosH(start, 1, "word");
    cm.replaceRange(op(cm.getRange(start, end)), start, end);
    cm.setCursor(end);
  }

  function toEnclosingExpr(cm) {
    var pos = cm.getCursor(), line = pos.line, ch = pos.ch;
    var stack = [];
    while (line >= cm.firstLine()) {
      var text = cm.getLine(line);
      for (var i = ch == null ? text.length : ch; i > 0;) {
        var ch = text.charAt(--i);
        if (ch == ")")
          stack.push("(");
        else if (ch == "]")
          stack.push("[");
        else if (ch == "}")
          stack.push("{");
        else if (/[\(\{\[]/.test(ch) && (!stack.length || stack.pop() != ch))
          return cm.extendSelection(Pos(line, i));
      }
      --line; ch = null;
    }
  }

  // Commands. Names should match emacs function names (albeit in camelCase)
  // except where emacs function names collide with code mirror core commands.

  cmds.killRegion = function(cm) {
    _kill(cm, cm.getCursor("start"), cm.getCursor("end"), true);
  };

  // Maps to emacs kill-line
  cmds.killLineEmacs = repeated(function(cm) {
    var start = cm.getCursor(), end = cm.clipPos(Pos(start.line));
    var text = cm.getRange(start, end);
    if (!/\S/.test(text)) {
      text += "\n";
      end = Pos(start.line + 1, 0);
    }
    _kill(cm, start, end, "grow", text);
  });

  cmds.killRingSave = function(cm) {
    addToRing(cm.getSelection());
    clearMark(cm);
  };

  cmds.yank = function(cm) {
    var start = cm.getCursor();
    cm.replaceRange(getFromRing(getPrefix(cm)), start, start, "paste");
    cm.setSelection(start, cm.getCursor());
  };

  cmds.yankPop = function(cm) {
    cm.replaceSelection(popFromRing(), "around", "paste");
  };

  cmds.forwardChar = move(byChar, 1);

  cmds.backwardChar = move(byChar, -1)

  cmds.deleteChar = function(cm) { killTo(cm, byChar, 1, false); };

  cmds.deleteForwardChar = function(cm) {
    _killRegion(cm, false) || killTo(cm, byChar, 1, false);
  };

  cmds.deleteBackwardChar = function(cm) {
    _killRegion(cm, false) || killTo(cm, byChar, -1, false);
  };

  cmds.forwardWord = move(byWord, 1);

  cmds.backwardWord = move(byWord, -1);

  cmds.killWord = function(cm) { killTo(cm, byWord, 1, "grow"); };

  cmds.backwardKillWord = function(cm) { killTo(cm, byWord, -1, "grow"); };

  cmds.nextLine = move(byLine, 1);

  cmds.previousLine = move(byLine, -1);

  cmds.scrollDownCommand = move(byPage, -1);

  cmds.scrollUpCommand = move(byPage, 1);

  cmds.backwardParagraph = move(byParagraph, -1);

  cmds.forwardParagraph = move(byParagraph, 1);

  cmds.backwardSentence = move(bySentence, -1);

  cmds.forwardSentence = move(bySentence, 1);

  cmds.killSentence = function(cm) { killTo(cm, bySentence, 1, "grow"); };

  cmds.backwardKillSentence = function(cm) {
    _kill(cm, cm.getCursor(), bySentence(cm, cm.getCursor(), 1), "grow");
  };

  cmds.killSexp = function(cm) { killTo(cm, byExpr, 1, "grow"); };

  cmds.backwardKillSexp = function(cm) { killTo(cm, byExpr, -1, "grow"); };

  cmds.forwardSexp = move(byExpr, 1);

  cmds.backwardSexp = move(byExpr, -1);

  cmds.markSexp = function(cm) {
    var cursor = cm.getCursor();
    cm.setSelection(findEnd(cm, cursor, byExpr, 1), cursor);
  };

  cmds.transposeSexps = function(cm) {
    var leftStart = byExpr(cm, cm.getCursor(), -1);
    var leftEnd = byExpr(cm, leftStart, 1);
    var rightEnd = byExpr(cm, leftEnd, 1);
    var rightStart = byExpr(cm, rightEnd, -1);
    cm.replaceRange(cm.getRange(rightStart, rightEnd) +
                    cm.getRange(leftEnd, rightStart) +
                    cm.getRange(leftStart, leftEnd), leftStart, rightEnd);
  };

  cmds.backwardUpList = repeated(toEnclosingExpr);

  cmds.justOneSpace = function(cm) {
    var pos = cm.getCursor(), from = pos.ch;
    var to = pos.ch, text = cm.getLine(pos.line);
    while (from && /\s/.test(text.charAt(from - 1))) --from;
    while (to < text.length && /\s/.test(text.charAt(to))) ++to;
    cm.replaceRange(" ", Pos(pos.line, from), Pos(pos.line, to));
  };

  cmds.openLine = repeated(function(cm) {
    cm.replaceSelection("\n", "start");
  });

  // maps to emacs 'transpose-chars'
  cmds.transposeCharsRepeatable = repeated(function(cm) {
    cm.execCommand("transposeChars");
  });

  cmds.capitalizeWord = repeated(function(cm) {
    operateOnWord(cm, function(w) {
      var letter = w.search(/\w/);
      if (letter == -1) return w;
      return w.slice(0, letter) + w.charAt(letter).toUpperCase() +
          w.slice(letter + 1).toLowerCase();
    });
  });

  cmds.upcaseWord = repeated(function(cm) {
    operateOnWord(cm, function(w) { return w.toUpperCase(); });
  });

  cmds.downcaseWord = repeated(function(cm) {
    operateOnWord(cm, function(w) { return w.toLowerCase(); });
  });

  // maps to emacs 'undo'
  cmds.undoRepeatable = repeated("undo");

  cmds.keyboardQuit = function(cm) {
    cm.execCommand("clearSearch");
    clearMark(cm);
  }

  cmds.newline = repeated(function(cm) { cm.replaceSelection("\n", "end"); });

  cmds.gotoLine = function(cm) {
    var prefix = getPrefix(cm, true);
    if (prefix != null && prefix > 0) return cm.setCursor(prefix - 1);

    getInput(cm, "Goto line", function(str) {
      var num;
      if (str && !isNaN(num = Number(str)) && num == (num|0) && num > 0)
      cm.setCursor(num - 1);
    });
  };

  cmds.indentRigidly = function(cm) {
    cm.indentSelection(getPrefix(cm, true) || cm.getOption("indentUnit"));
  };

  cmds.exchangePointAndMark = function(cm) {
    cm.setSelection(cm.getCursor("head"), cm.getCursor("anchor"));
  };

  cmds.quotedInsertTab = repeated("insertTab");

  cmds.universalArgument = function addPrefixMap(cm) {
    cm.state.emacsPrefixMap = true;
    cm.addKeyMap(prefixMap);
    cm.on("keyHandled", maybeRemovePrefixMap);
    cm.on("inputRead", maybeRemovePrefixMap);
  };

  CodeMirror.emacsMini = {kill: _kill, killRegion: _killRegion, repeated: repeated};

  // Actual keymap
  var keyMap = CodeMirror.keyMap.emacsMini = CodeMirror.normalizeKeyMap({
    // "Ctrl-W": "killRegion",
    "Ctrl-K": "killLineEmacs",
    // "Alt-W": "killRingSave",
    "Ctrl-Y": "yank",
    "Alt-Y": "yankPop",
    // "Ctrl-Space": "setMark",
    // "Ctrl-Shift-2": "setMark",
    "Ctrl-F": "forwardChar",
    "Ctrl-B": "backwardChar",
    // "Right": "forwardChar",
    // "Left": "backwardChar",
    "Ctrl-D": "deleteForwardChar",
    "Delete": "deleteForwardChar",
    // "Ctrl-H": "deleteBackwardChar",
    // "Backspace": "deleteBackwardChar",
    "Alt-F": "forwardWord",
    "Alt-B": "backwardWord",
    "Alt-Right": "forwardWord",
    "Alt-Left": "backwardWord",
    "Alt-D": "killWord",
    // "Alt-Backspace": "backwardKillWord",
    "Ctrl-N": "nextLine",
    "Ctrl-P": "previousLine",
    // "Down": "nextLine",
    // "Up": "previousLine",
    "Ctrl-A": "goLineStart",
    "Ctrl-E": "goLineEnd",
    // "End": "goLineEnd",
    // "Home": "goLineStart",
    // "Alt-V": "scrollDownCommand",
    // "Ctrl-V": "scrollUpCommand",
    // "PageUp": "scrollDownCommand",
    // "PageDown": "scrollUpCommand",
    // "Ctrl-Up": "backwardParagraph",
    // "Ctrl-Down": "forwardParagraph",
    // "Alt-{": "backwardParagraph",
    // "Alt-}": "forwardParagraph",
    // "Alt-A": "backwardSentence",
    // "Alt-E": "forwardSentence",
    // "Alt-K": "killSentence",
    // "Ctrl-X Delete": "backwardKillSentence",
    // "Ctrl-Alt-K": "killSexp",
    // "Ctrl-Alt-Backspace": "backwardKillSexp",
    // "Ctrl-Alt-F": "forwardSexp",
    // "Ctrl-Alt-B": "backwardSexp",
    // "Shift-Ctrl-Alt-2": "markSexp",
    // "Ctrl-Alt-T": "transposeSexps",
    // "Ctrl-Alt-U": "backwardUpList",
    // "Alt-Space": "justOneSpace",
    // "Ctrl-O": "openLine",
    // "Ctrl-T": "transposeCharsRepeatable",
    // "Alt-C": "capitalizeWord",
    // "Alt-U": "upcaseWord",
    // "Alt-L": "downcaseWord",
    // "Alt-;": "toggleComment",
    // "Ctrl-/": "undoRepeatable",
    // "Shift-Ctrl--": "undoRepeatable",
    // "Ctrl-Z": "undoRepeatable",
    // "Cmd-Z": "undoRepeatable",
    // "Ctrl-X U": "undoRepeatable",
    // "Shift-Ctrl-Z": "redo",
    // "Shift-Alt-,": "goDocStart",
    // "Shift-Alt-.": "goDocEnd",
    "Ctrl-S": "findPersistentNext",
    "Ctrl-R": "findPersistentPrev",
    // "Ctrl-G": "keyboardQuit",
    // "Shift-Alt-5": "replace",
    // "Alt-/": "autocomplete",
    // "Enter": "newlineAndIndent",
    // "Ctrl-J": "newline",
    // "Tab": "indentAuto",
    "Alt-G G": "gotoLine",
    // "Ctrl-X Tab": "indentRigidly",
    // "Ctrl-X Ctrl-X": "exchangePointAndMark",
    // "Ctrl-X Ctrl-S": "save",
    // "Ctrl-X Ctrl-W": "save",
    // "Ctrl-X S": "saveAll",
    // "Ctrl-X F": "open",
    // "Ctrl-X K": "close",
    // "Ctrl-X H": "selectAll",
    // "Ctrl-Q Tab": "quotedInsertTab",
    // "Ctrl-U": "universalArgument",
    "fallthrough": "default"
  });

  var prefixMap = {"Ctrl-G": clearPrefix};
  function regPrefix(d) {
    prefixMap[d] = function(cm) { addPrefix(cm, d); };
    keyMap["Ctrl-" + d] = function(cm) { addPrefix(cm, d); };
    prefixPreservingKeys["Ctrl-" + d] = true;
  }
  for (var i = 0; i < 10; ++i) regPrefix(String(i));
  regPrefix("-");

  setupDone = true
};