text: // Copyright 2008 The Closure Library Authors. All Rights Reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS-IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  /**
   * @fileoverview Utility function for linkifying text.
   * @author bolinfest@google.com (Michael Bolin)
   */
  
  goog.provide('goog.string.linkify');
  
  goog.require('goog.string');
  
  
  /**
   * Takes a string of plain text and linkifies URLs and email addresses. For a
   * URL (unless opt_attributes is specified), the target of the link will be
   * _blank and it will have a rel=nofollow attribute applied to it so that links
   * created by linkify will not be of interest to search engines.
   * @param {string} text Plain text.
   * @param {Object.<string, string>=} opt_attributes Attributes to add to all
   *      links created. Default are rel=nofollow and target=blank. To clear those
   *      default attributes set rel='' and target='_blank'.
   * @return {string} HTML Linkified HTML text.
   */
  goog.string.linkify.linkifyPlainText = function(text, opt_attributes) {
    var attributesMap = opt_attributes || {};
    // Set default options.
    if (!('rel' in attributesMap)) {
      attributesMap['rel'] = 'nofollow';
    }
    if (!('target' in attributesMap)) {
      attributesMap['target'] = '_blank';
    }
    // Creates attributes string from options.
    var attributesArray = [];
    for (var key in attributesMap) {
      if (attributesMap.hasOwnProperty(key) && attributesMap[key]) {
        attributesArray.push(
            goog.string.htmlEscape(key), '="',
            goog.string.htmlEscape(attributesMap[key]), '" ');
      }
    }
    var attributes = attributesArray.join('');
  
    return text.replace(
        goog.string.linkify.FIND_LINKS_RE_,
        function(part, before, original, email, protocol) {
          var output = [goog.string.htmlEscape(before)];
          if (!original) {
            return output[0];
          }
          output.push('<a ', attributes, 'href="');
          /** @type {string} */
          var linkText;
          /** @type {string} */
          var afterLink;
          if (email) {
            output.push('mailto:');
            linkText = email;
            afterLink = '';
          } else {
            // This is a full url link.
            if (!protocol) {
              output.push('http://');
            }
            var splitEndingPunctuation =
                original.match(goog.string.linkify.ENDS_WITH_PUNCTUATION_RE_);
            if (splitEndingPunctuation) {
              linkText = splitEndingPunctuation[1];
              afterLink = splitEndingPunctuation[2];
            } else {
              linkText = original;
              afterLink = '';
            }
          }
          linkText = goog.string.htmlEscape(linkText);
          afterLink = goog.string.htmlEscape(afterLink);
          output.push(linkText, '">', linkText, '</a>', afterLink);
          return output.join('');
        });
  };
  
  
  /**
   * @type {string}
   * @const
   * @private
   */
  goog.string.linkify.ENDING_PUNCTUATION_CHARS_ = ':;,\\.?\\[\\]';
  
  
  /**
   * @type {!RegExp}
   * @const
   * @private
   */
  goog.string.linkify.ENDS_WITH_PUNCTUATION_RE_ =
      new RegExp(
          '^(.*)([' + goog.string.linkify.ENDING_PUNCTUATION_CHARS_ + '])$');
  
  
  /**
   * @type {string}
   * @const
   * @private
   */
  goog.string.linkify.ACCEPTABLE_URL_CHARS_ =
      goog.string.linkify.ENDING_PUNCTUATION_CHARS_ + '\\w/~%&=+#-@';
  
  
  /**
   * List of all protocols patterns recognized in urls (mailto is handled in email
   * matching).
   * @type {!Array.<string>}
   * @const
   * @private
   */
  goog.string.linkify.RECOGNIZED_PROTOCOLS_ = ['https?', 'ftp'];
  
  
  /**
   * Regular expression pattern that matches the beginning of an url.
   * Contains a catching group to capture the scheme.
   * @type {string}
   * @const
   * @private
   */
  goog.string.linkify.PROTOCOL_START_ =
      '(' + goog.string.linkify.RECOGNIZED_PROTOCOLS_.join('|') + ')://+';
  
  
  /**
   * Regular expression pattern that matches the beginning of a typical
   * http url without the http:// scheme.
   * @type {string}
   * @const
   * @private
   */
  goog.string.linkify.WWW_START_ = 'www\\.';
  
  
  /**
   * Regular expression pattern that matches an url.
   * @type {string}
   * @const
   * @private
   */
  goog.string.linkify.URL_ =
      '(?:' + goog.string.linkify.PROTOCOL_START_ + '|' +
      goog.string.linkify.WWW_START_ + ')\\w[' +
      goog.string.linkify.ACCEPTABLE_URL_CHARS_ + ']*';
  
  
  /**
   * Regular expression pattern that matches a top level domain.
   * @type {string}
   * @const
   * @private
   */
  goog.string.linkify.TOP_LEVEL_DOMAIN_ =
      '(?:com|org|net|edu|gov' +
      // from http://www.iana.org/gtld/gtld.htm
      '|aero|biz|cat|coop|info|int|jobs|mobi|museum|name|pro|travel' +
      '|arpa|asia|xxx' +
      // a two letter country code
      '|[a-z][a-z])\\b';
  
  
  /**
   * Regular expression pattern that matches an email.
   * Contains a catching group to capture the email without the optional "mailto:"
   * prefix.
   * @type {string}
   * @const
   * @private
   */
  goog.string.linkify.EMAIL_ =
      '(?:mailto:)?([\\w.+-]+@[A-Za-z0-9.-]+\\.' +
      goog.string.linkify.TOP_LEVEL_DOMAIN_ + ')';
  
  
  /**
   * Regular expression to match all the links (url or email) in a string.
   * First match is text before first link, might be empty string.
   * Second match is the original text that should be replaced by a link.
   * Third match is the email address in the case of an email.
   * Fourth match is the scheme of the url if specified.
   * @type {!RegExp}
   * @const
   * @private
   */
  goog.string.linkify.FIND_LINKS_RE_ = new RegExp(
      // Match everything including newlines.
      '([\\S\\s]*?)(' +
      // Match email after a word break.
      '\\b' + goog.string.linkify.EMAIL_ + '|' +
      // Match url after a workd break.
      '\\b' + goog.string.linkify.URL_ + '|$)',
      'g');
  
  