(function() {
  var DEFAULT_BRACKETS = "()[]{}''\"\"";
  var SPACE_CHAR_REGEX = /\s/;

  CodeMirror.defineOption("autoCloseBrackets", false, function(cm, val, old) {
    var wasOn = old && old != CodeMirror.Init;
    if (val && !wasOn)
      cm.addKeyMap(buildKeymap(typeof val == "string" ? val : DEFAULT_BRACKETS));
    else if (!val && wasOn)
      cm.removeKeyMap("autoCloseBrackets");
  });

  function buildKeymap(pairs) {
    var map = {
      name : "autoCloseBrackets",
      Backspace: function(cm) {
        if (cm.somethingSelected()) return CodeMirror.Pass;
        var cur = cm.getCursor(), line = cm.getLine(cur.line);
        if (cur.ch && cur.ch < line.length &&
            pairs.indexOf(line.slice(cur.ch - 1, cur.ch + 1)) % 2 == 0)
          cm.replaceRange("", CodeMirror.Pos(cur.line, cur.ch - 1), CodeMirror.Pos(cur.line, cur.ch + 1));
        else
          return CodeMirror.Pass;
      }
    };
    var closingBrackets = [];
    for (var i = 0; i < pairs.length; i += 2) (function(left, right) {
      if (left != right) closingBrackets.push(right);
      function surround(cm) {
          var selection = cm.getSelection();
          cm.replaceSelection(left + selection + right);
      }
      function maybeOverwrite(cm) {
        var cur = cm.getCursor(), ahead = cm.getRange(cur, CodeMirror.Pos(cur.line, cur.ch + 1));
        if (ahead != right || cm.somethingSelected()) return CodeMirror.Pass;
        else cm.execCommand("goCharRight");
      }
      map["'" + left + "'"] = function(cm) {
        if (cm.somethingSelected()) return surround(cm);
        if (left == right && maybeOverwrite(cm) != CodeMirror.Pass) return;
        var cur = cm.getCursor(), ahead = CodeMirror.Pos(cur.line, cur.ch + 1);
        var line = cm.getLine(cur.line), nextChar = line.charAt(cur.ch);
        if (line.length == cur.ch || closingBrackets.indexOf(nextChar) >= 0 || SPACE_CHAR_REGEX.test(nextChar))
          cm.replaceSelection(left + right, {head: ahead, anchor: ahead});
        else
          return CodeMirror.Pass;
      };
      if (left != right) map["'" + right + "'"] = maybeOverwrite;
    })(pairs.charAt(i), pairs.charAt(i + 1));
    return map;
  }
})();