/**
 * Turn Markdown link shortcuts into XHTML <a> tags.
 */
showdown.subParser('anchors', function (text, options, globals) {
  'use strict';

  text = globals.converter._dispatch('anchors.before', text, options, globals);

  var writeAnchorTag = function (wholeMatch, m1, m2, m3, m4, m5, m6, m7) {
    if (showdown.helper.isUndefined(m7)) {
      m7 = '';
    }
    wholeMatch = m1;
    var linkText = m2,
        linkId = m3.toLowerCase(),
        url = m4,
        title = m7;

    if (!url) {
      if (!linkId) {
        // lower-case and turn embedded newlines into spaces
        linkId = linkText.toLowerCase().replace(/ ?\n/g, ' ');
      }
      url = '#' + linkId;

      if (!showdown.helper.isUndefined(globals.gUrls[linkId])) {
        url = globals.gUrls[linkId];
        if (!showdown.helper.isUndefined(globals.gTitles[linkId])) {
          title = globals.gTitles[linkId];
        }
      } else {
        if (wholeMatch.search(/\(\s*\)$/m) > -1) {
          // Special case for explicit empty url
          url = '';
        } else {
          return wholeMatch;
        }
      }
    }

    //url = showdown.helper.escapeCharacters(url, '*_', false); // replaced line to improve performance
    url = url.replace(showdown.helper.regexes.asteriskAndDash, showdown.helper.escapeCharactersCallback);

    var result = '<a href="' + url + '"';

    if (title !== '' && title !== null) {
      title = title.replace(/"/g, '&quot;');
      //title = showdown.helper.escapeCharacters(title, '*_', false); // replaced line to improve performance
      title = title.replace(showdown.helper.regexes.asteriskAndDash, showdown.helper.escapeCharactersCallback);
      result += ' title="' + title + '"';
    }

    result += '>' + linkText + '</a>';

    return result;
  };

  // First, handle reference-style links: [link text] [id]
  text = text.replace(/(\[((?:\[[^\]]*]|[^\[\]])*)][ ]?(?:\n[ ]*)?\[(.*?)])()()()()/g, writeAnchorTag);

  // Next, inline-style links: [link text](url "optional title")
  text = text.replace(/(\[((?:\[[^\]]*]|[^\[\]])*)]\([ \t]*()<?(.*?(?:\(.*?\).*?)?)>?[ \t]*((['"])(.*?)\6[ \t]*)?\))/g,
                      writeAnchorTag);

  // handle reference-style shortcuts: [link text]
  // These must come last in case you've also got [link test][1]
  // or [link test](/foo)
  text = text.replace(/(\[([^\[\]]+)])()()()()()/g, writeAnchorTag);

  // Lastly handle GithubMentions if option is enabled
  if (options.ghMentions) {
    text = text.replace(/(^|\s)(\\)?(@([a-z\d\-]+))(?=[.!?;,[\]()]|\s|$)/gmi, function (wm, st, escape, mentions, username) {
      if (escape === '\\') {
        return st + mentions;
      }

      //check if options.ghMentionsLink is a string
      if (!showdown.helper.isString(options.ghMentionsLink)) {
        throw new Error('ghMentionsLink option must be a string');
      }
      var lnk = options.ghMentionsLink.replace(/\{u}/g, username);
      return st + '<a href="' + lnk + '">' + mentions + '</a>';
    });
  }

  text = globals.converter._dispatch('anchors.after', text, options, globals);
  return text;
});