exports.handler.handleKeyboard = function()

in lib/ace/keyboard/emacs.js [236:341]
66 lines of code
33 McCabe index (conditional complexity)

exports.handler.handleKeyboard = function(data, hashId, key, keyCode) {
    // if keyCode == -1 a non-printable key was pressed, such as just
    // control. Handling those is currently not supported in this handler
    if (keyCode === -1) return undefined;

    var editor = data.editor;
    editor._signal("changeStatus");
    // insertstring data.count times
    if (hashId == -1) {
        editor.pushEmacsMark();
        if (data.count) {
            var str = new Array(data.count + 1).join(key);
            data.count = null;
            return {command: "insertstring", args: str};
        }
    }

    var modifier = eMods[hashId];

    // CTRL + number / universalArgument for setting data.count
    if (modifier == "c-" || data.count) {
        var count = parseInt(key[key.length - 1]);
        if (typeof count === 'number' && !isNaN(count)) {
            data.count = Math.max(data.count, 0) || 0;
            data.count = 10 * data.count + count;
            return {command: "null"};
        }
    }

    // this.commandKeyBinding maps key specs like "c-p" (for CTRL + P) to
    // command objects, for lookup key needs to include the modifier
    if (modifier) key = modifier + key;

    // Key combos like CTRL+X H build up the data.keyChain
    if (data.keyChain) key = data.keyChain += " " + key;

    // Key combo prefixes get stored as "null" (String!) in this
    // this.commandKeyBinding. When encountered no command is invoked but we
    // buld up data.keyChain
    var command = this.commandKeyBinding[key];
    data.keyChain = command == "null" ? key : "";

    // there really is no command
    if (!command) return undefined;

    // we pass b/c of key combo or universalArgument
    if (command === "null") return {command: "null"};

    if (command === "universalArgument") {
        // if no number pressed emacs repeats action 4 times.
        // minus sign is needed to allow next keypress to replace it
        data.count = -4;
        return {command: "null"};
    }

    // lookup command
    // TODO extract special handling of markmode
    // TODO special case command.command is really unnecessary, remove
    var args;
    if (typeof command !== "string") {
        args = command.args;
        if (command.command) command = command.command;
        if (command === "goorselect") {
            command = editor.emacsMark() ? args[1] : args[0];
            args = null;
        }
    }

    if (typeof command === "string") {
        if (command === "insertstring" ||
            command === "splitline" ||
            command === "togglecomment") {
            editor.pushEmacsMark();
        }
        command = this.commands[command] || editor.commands.commands[command];
        if (!command) return undefined;
    }

    if (!command.readOnly && !command.isYank)
        data.lastCommand = null;

    if (!command.readOnly && editor.emacsMark())
        editor.setEmacsMark(null);
        
    if (data.count) {
        var count = data.count;
        data.count = 0;
        if (!command || !command.handlesCount) {
            return {
                args: args,
                command: {
                    exec: function(editor, args) {
                        for (var i = 0; i < count; i++)
                            command.exec(editor, args);
                    },
                    multiSelectAction: command.multiSelectAction
                }
            };
        } else {
            if (!args) args = {};
            if (typeof args === 'object') args.count = count;
        }
    }

    return {command: command, args: args};
};