/**
 * Turn Markdown image shortcuts into <img> tags.
 */
showdown.subParser('images', function (text, options, globals) {
  'use strict';

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

  var inlineRegExp    = /!\[(.*?)]\s?\([ \t]*()<?(\S+?)>?(?: =([*\d]+[A-Za-z%]{0,4})x([*\d]+[A-Za-z%]{0,4}))?[ \t]*(?:(['"])(.*?)\6[ \t]*)?\)/g,
      referenceRegExp = /!\[(.*?)][ ]?(?:\n[ ]*)?\[(.*?)]()()()()()/g;

  function writeImageTag (wholeMatch, altText, linkId, url, width, height, m5, title) {

    var gUrls   = globals.gUrls,
        gTitles = globals.gTitles,
        gDims   = globals.gDimensions;

    linkId = linkId.toLowerCase();

    if (!title) {
      title = '';
    }

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

      if (!showdown.helper.isUndefined(gUrls[linkId])) {
        url = gUrls[linkId];
        if (!showdown.helper.isUndefined(gTitles[linkId])) {
          title = gTitles[linkId];
        }
        if (!showdown.helper.isUndefined(gDims[linkId])) {
          width = gDims[linkId].width;
          height = gDims[linkId].height;
        }
      } else {
        return wholeMatch;
      }
    }

    altText = altText.replace(/"/g, '&quot;');
    altText = showdown.helper.escapeCharacters(altText, '*_', false);
    url = showdown.helper.escapeCharacters(url, '*_', false);
    var result = '<img src="' + url + '" alt="' + altText + '"';

    if (title) {
      title = title.replace(/"/g, '&quot;');
      title = showdown.helper.escapeCharacters(title, '*_', false);
      result += ' title="' + title + '"';
    }

    if (width && height) {
      width  = (width === '*') ? 'auto' : width;
      height = (height === '*') ? 'auto' : height;

      result += ' width="' + width + '"';
      result += ' height="' + height + '"';
    }

    result += ' />';

    return result;
  }

  // First, handle reference-style labeled images: ![alt text][id]
  text = text.replace(referenceRegExp, writeImageTag);

  // Next, handle inline images:  ![alt text](url =<width>x<height> "optional title")
  text = text.replace(inlineRegExp, writeImageTag);

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