/**
 * Copyright (c) 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule DraftRemovableWord
 * @format
 * @flow
 */

'use strict';

var TokenizeUtil = require('fbjs/lib/TokenizeUtil');

var punctuation = TokenizeUtil.getPunctuation();

// The apostrophe and curly single quotes behave in a curious way: when
// surrounded on both sides by word characters, they behave as word chars; when
// either neighbor is punctuation or an end of the string, they behave as
// punctuation.
var CHAMELEON_CHARS = "['\u2018\u2019]";

// Remove the underscore, which should count as part of the removable word. The
// "chameleon chars" also count as punctuation in this regex.
var WHITESPACE_AND_PUNCTUATION = '\\s|(?![_])' + punctuation;

var DELETE_STRING = '^' + '(?:' + WHITESPACE_AND_PUNCTUATION + ')*' + '(?:' + CHAMELEON_CHARS + '|(?!' + WHITESPACE_AND_PUNCTUATION + ').)*' + '(?:(?!' + WHITESPACE_AND_PUNCTUATION + ').)';
var DELETE_REGEX = new RegExp(DELETE_STRING);

var BACKSPACE_STRING = '(?:(?!' + WHITESPACE_AND_PUNCTUATION + ').)' + '(?:' + CHAMELEON_CHARS + '|(?!' + WHITESPACE_AND_PUNCTUATION + ').)*' + '(?:' + WHITESPACE_AND_PUNCTUATION + ')*' + '$';
var BACKSPACE_REGEX = new RegExp(BACKSPACE_STRING);

function getRemovableWord(text: string, isBackward: boolean): string {
  var matches = isBackward ? BACKSPACE_REGEX.exec(text) : DELETE_REGEX.exec(text);
  return matches ? matches[0] : text;
}

var DraftRemovableWord = {
  getBackward: function (text: string): string {
    return getRemovableWord(text, true);
  },

  getForward: function (text: string): string {
    return getRemovableWord(text, false);
  }
};

module.exports = DraftRemovableWord;