showdownjs/src/converter.js

/**
 * Created by Estevao on 31-05-2015.
 */

/**
 * Showdown Converter class
 * @class
 * @param {object} [converterOptions]
 * @returns {Converter}
 */
showdown.Converter = function (converterOptions) {
  'use strict';

  var
      /**
       * Options used by this converter
       * @private
       * @type {{}}
       */
      options = {},

      /**
       * Language extensions used by this converter
       * @private
       * @type {Array}
       */
      langExtensions = [],

      /**
       * Output modifiers extensions used by this converter
       * @private
       * @type {Array}
       */
      outputModifiers = [],

      /**
       * Event listeners
       * @private
       * @type {{}}
       */
      listeners = {},

      /**
       * The flavor set in this converter
       */
      setConvFlavor = setFlavor,

    /**
     * Metadata of the document
     * @type {{parsed: {}, raw: string, format: string}}
     */
      metadata = {
        parsed: {},
        raw: '',
        format: ''
      };

  _constructor();

  /**
   * Converter constructor
   * @private
   */
  function _constructor () {
    converterOptions = converterOptions || {};

    for (var gOpt in globalOptions) {
      if (globalOptions.hasOwnProperty(gOpt)) {
        options[gOpt] = globalOptions[gOpt];
      }
    }

    // Merge options
    if (typeof converterOptions === 'object') {
      for (var opt in converterOptions) {
        if (converterOptions.hasOwnProperty(opt)) {
          options[opt] = converterOptions[opt];
        }
      }
    } else {
      throw Error('Converter expects the passed parameter to be an object, but ' + typeof converterOptions +
      ' was passed instead.');
    }

    if (options.extensions) {
      showdown.helper.forEach(options.extensions, _parseExtension);
    }
  }

  /**
   * Parse extension
   * @param {*} ext
   * @param {string} [name='']
   * @private
   */
  function _parseExtension (ext, name) {

    name = name || null;
    // If it's a string, the extension was previously loaded
    if (showdown.helper.isString(ext)) {
      ext = showdown.helper.stdExtName(ext);
      name = ext;

      // LEGACY_SUPPORT CODE
      if (showdown.extensions[ext]) {
        console.warn('DEPRECATION WARNING: ' + ext + ' is an old extension that uses a deprecated loading method.' +
          'Please inform the developer that the extension should be updated!');
        legacyExtensionLoading(showdown.extensions[ext], ext);
        return;
      // END LEGACY SUPPORT CODE

      } else if (!showdown.helper.isUndefined(extensions[ext])) {
        ext = extensions[ext];

      } else {
        throw Error('Extension "' + ext + '" could not be loaded. It was either not found or is not a valid extension.');
      }
    }

    if (typeof ext === 'function') {
      ext = ext();
    }

    if (!showdown.helper.isArray(ext)) {
      ext = [ext];
    }

    var validExt = validate(ext, name);
    if (!validExt.valid) {
      throw Error(validExt.error);
    }

    for (var i = 0; i < ext.length; ++i) {
      switch (ext[i].type) {

        case 'lang':
          langExtensions.push(ext[i]);
          break;

        case 'output':
          outputModifiers.push(ext[i]);
          break;
      }
      if (ext[i].hasOwnProperty('listeners')) {
        for (var ln in ext[i].listeners) {
          if (ext[i].listeners.hasOwnProperty(ln)) {
            listen(ln, ext[i].listeners[ln]);
          }
        }
      }
    }

  }

  /**
   * LEGACY_SUPPORT
   * @param {*} ext
   * @param {string} name
   */
  function legacyExtensionLoading (ext, name) {
    if (typeof ext === 'function') {
      ext = ext(new showdown.Converter());
    }
    if (!showdown.helper.isArray(ext)) {
      ext = [ext];
    }
    var valid = validate(ext, name);

    if (!valid.valid) {
      throw Error(valid.error);
    }

    for (var i = 0; i < ext.length; ++i) {
      switch (ext[i].type) {
        case 'lang':
          langExtensions.push(ext[i]);
          break;
        case 'output':
          outputModifiers.push(ext[i]);
          break;
        default:// should never reach here
          throw Error('Extension loader error: Type unrecognized!!!');
      }
    }
  }

  /**
   * Listen to an event
   * @param {string} name
   * @param {function} callback
   */
  function listen (name, callback) {
    if (!showdown.helper.isString(name)) {
      throw Error('Invalid argument in converter.listen() method: name must be a string, but ' + typeof name + ' given');
    }

    if (typeof callback !== 'function') {
      throw Error('Invalid argument in converter.listen() method: callback must be a function, but ' + typeof callback + ' given');
    }

    if (!listeners.hasOwnProperty(name)) {
      listeners[name] = [];
    }
    listeners[name].push(callback);
  }

  function rTrimInputText (text) {
    var rsp = text.match(/^\s*/)[0].length,
        rgx = new RegExp('^\\s{0,' + rsp + '}', 'gm');
    return text.replace(rgx, '');
  }

  /**
   * Dispatch an event
   * @private
   * @param {string} evtName Event name
   * @param {string} text Text
   * @param {{}} options Converter Options
   * @param {{}} globals
   * @returns {string}
   */
  this._dispatch = function dispatch (evtName, text, options, globals) {
    if (listeners.hasOwnProperty(evtName)) {
      for (var ei = 0; ei < listeners[evtName].length; ++ei) {
        var nText = listeners[evtName][ei](evtName, text, this, options, globals);
        if (nText && typeof nText !== 'undefined') {
          text = nText;
        }
      }
    }
    return text;
  };

  /**
   * Listen to an event
   * @param {string} name
   * @param {function} callback
   * @returns {showdown.Converter}
   */
  this.listen = function (name, callback) {
    listen(name, callback);
    return this;
  };

  /**
   * Converts a markdown string into HTML string
   * @param {string} text
   * @returns {*}
   */
  this.makeHtml = function (text) {
    //check if text is not falsy
    if (!text) {
      return text;
    }

    var globals = {
      gHtmlBlocks:     [],
      gHtmlMdBlocks:   [],
      gHtmlSpans:      [],
      gUrls:           {},
      gTitles:         {},
      gDimensions:     {},
      gListLevel:      0,
      hashLinkCounts:  {},
      langExtensions:  langExtensions,
      outputModifiers: outputModifiers,
      converter:       this,
      ghCodeBlocks:    [],
      metadata: {
        parsed: {},
        raw: '',
        format: ''
      }
    };

    // This lets us use ¨ trema as an escape char to avoid md5 hashes
    // The choice of character is arbitrary; anything that isn't
    // magic in Markdown will work.
    text = text.replace(/¨/g, '¨T');

    // Replace $ with ¨D
    // RegExp interprets $ as a special character
    // when it's in a replacement string
    text = text.replace(/\$/g, '¨D');

    // Standardize line endings
    text = text.replace(/\r\n/g, '\n'); // DOS to Unix
    text = text.replace(/\r/g, '\n'); // Mac to Unix

    // Stardardize line spaces (nbsp causes trouble in older browsers and some regex flavors)
    text = text.replace(/\u00A0/g, ' ');

    if (options.smartIndentationFix) {
      text = rTrimInputText(text);
    }

    // Make sure text begins and ends with a couple of newlines:
    text = '\n\n' + text + '\n\n';

    // detab
    text = showdown.subParser('makehtml.detab')(text, options, globals);

    /**
     * Strip any lines consisting only of spaces and tabs.
     * This makes subsequent regexs easier to write, because we can
     * match consecutive blank lines with /\n+/ instead of something
     * contorted like /[ \t]*\n+/
     */
    text = text.replace(/^[ \t]+$/mg, '');

    //run languageExtensions
    showdown.helper.forEach(langExtensions, function (ext) {
      text = showdown.subParser('makehtml.runExtension')(ext, text, options, globals);
    });

    // run the sub parsers
    text = showdown.subParser('makehtml.metadata')(text, options, globals);
    text = showdown.subParser('makehtml.hashPreCodeTags')(text, options, globals);
    text = showdown.subParser('makehtml.githubCodeBlocks')(text, options, globals);
    text = showdown.subParser('makehtml.hashHTMLBlocks')(text, options, globals);
    text = showdown.subParser('makehtml.hashCodeTags')(text, options, globals);
    text = showdown.subParser('makehtml.stripLinkDefinitions')(text, options, globals);
    text = showdown.subParser('makehtml.blockGamut')(text, options, globals);
    text = showdown.subParser('makehtml.unhashHTMLSpans')(text, options, globals);
    text = showdown.subParser('makehtml.unescapeSpecialChars')(text, options, globals);

    // attacklab: Restore dollar signs
    text = text.replace(/¨D/g, '$$');

    // attacklab: Restore tremas
    text = text.replace(/¨T/g, '¨');

    // render a complete html document instead of a partial if the option is enabled
    text = showdown.subParser('makehtml.completeHTMLDocument')(text, options, globals);

    // Run output modifiers
    showdown.helper.forEach(outputModifiers, function (ext) {
      text = showdown.subParser('makehtml.runExtension')(ext, text, options, globals);
    });

    // update metadata
    metadata = globals.metadata;
    return text;
  };

  /**
   * Converts an HTML string into a markdown string
   * @param src
   * @returns {string}
   */
  this.makeMarkdown = function (src) {

    // replace \r\n with \n
    src = src.replace(/\r\n/g, '\n');
    src = src.replace(/\r/g, '\n'); // old macs

    // due to an edge case, we need to find this: > <
    // to prevent removing of non silent white spaces
    // ex: <em>this is</em> <strong>sparta</strong>
    src = src.replace(/>[ \t]+</, '>¨NBSP;<');

    var doc = showdown.helper.document.createElement('div');
    doc.innerHTML = src;

    var preList = substitutePreCodeTags(doc);

    // remove all newlines and collapse spaces
    clean(doc);

    // some stuff, like accidental reference links must now be escaped
    // TODO
    // doc.innerHTML = doc.innerHTML.replace(/\[[\S\t ]]/);

    var nodes = doc.childNodes,
        mdDoc = '';

    for (var i = 0; i < nodes.length; i++) {
      mdDoc += parseNode(nodes[i]);
    }


    function parseNode (node, spansOnly) {

      spansOnly = spansOnly || false;

      var txt = '';

      // edge case of text without wrapper paragraph
      if (node.nodeType === 3) {
        return parseTxt(node);
      }

      // HTML comment
      if (node.nodeType === 8) {
        return '<!--' + node.data + '-->\n\n';
      }

      // process only node elements
      if (node.nodeType !== 1) {
        return '';
      }

      var tagName = node.tagName.toLowerCase();

      switch (tagName) {

        //
        // BLOCKS
        //
        case 'h1':
          if (!spansOnly) { txt = parseHeader(node, 1) + '\n\n'; }
          break;
        case 'h2':
          if (!spansOnly) { txt = parseHeader(node, 2) + '\n\n'; }
          break;
        case 'h3':
          if (!spansOnly) { txt = parseHeader(node, 3) + '\n\n'; }
          break;
        case 'h4':
          if (!spansOnly) { txt = parseHeader(node, 4) + '\n\n'; }
          break;
        case 'h5':
          if (!spansOnly) { txt = parseHeader(node, 5) + '\n\n'; }
          break;
        case 'h6':
          if (!spansOnly) { txt = parseHeader(node, 6) + '\n\n'; }
          break;

        case 'p':
          if (!spansOnly) { txt = parseParagraph(node) + '\n\n'; }
          break;

        case 'blockquote':
          if (!spansOnly) { txt = parseBlockquote(node) + '\n\n'; }
          break;

        case 'hr':
          if (!spansOnly) { txt = parseHr(node) + '\n\n'; }
          break;

        case 'ol':
          if (!spansOnly) { txt = parseList(node, 'ol') + '\n\n'; }
          break;

        case 'ul':
          if (!spansOnly) { txt = parseList(node, 'ul') + '\n\n'; }
          break;

        case 'precode':
          if (!spansOnly) { txt = parsePreCode(node) + '\n\n'; }
          break;

        case 'pre':
          if (!spansOnly) { txt = parsePre(node) + '\n\n'; }
          break;

        case 'table':
          if (!spansOnly) { txt = parseTable(node) + '\n\n'; }
          break;

        //
        // SPANS
        //
        case 'code':
          txt = parseCodeSpan(node);
          break;

        case 'em':
        case 'i':
          txt = parseEmphasis(node);
          break;

        case 'strong':
        case 'b':
          txt = parseStrong(node);
          break;

        case 'del':
          txt = parseDel(node);
          break;

        case 'a':
          txt = parseLinks(node);
          break;

        case 'img':
          txt = parseImage(node);
          break;

        default:
          txt = node.outerHTML + '\n\n';
      }

      // common normalization


      return txt;
    }

    function parseTxt (node) {
      var txt = node.nodeValue;

      // multiple spaces are collapsed
      txt = txt.replace(/ +/g, ' ');

      // replace the custom ¨NBSP; with a space
      txt = txt.replace(/¨NBSP;/g, ' ');

      // ", <, > and & should replace escaped html entities
      txt = showdown.helper.unescapeHTMLEntities(txt);

      // escape markdown magic characters
      // emphasis, strong and strikethrough - can appear everywhere
      // we also escape pipe (|) because of tables
      // and escape ` because of code blocks and spans
      txt = txt.replace(/([*_~|`])/g, '\\$1');

      // escape > because of blockquotes
      txt = txt.replace(/^(\s*)>/g, '\\$1>');

      // hash character, only troublesome at the beginning of a line because of headers
      txt = txt.replace(/^#/gm, '\\#');

      // horizontal rules
      txt = txt.replace(/^(\s*)([-=]{3,})(\s*)$/, '$1\\$2$3');

      // dot, because of ordered lists, only troublesome at the beginning of a line when preceded by an integer
      txt = txt.replace(/^( {0,3}\d+)\./gm, '$1\\.');

      // +, * and -, at the beginning of a line becomes a list, so we need to escape them also (asterisk was already escaped)
      txt = txt.replace(/^( {0,3})([+-])/gm, '$1\\$2');

      // images and links, ] followed by ( is problematic, so we escape it
      txt = txt.replace(/]([\s]*)\(/g, '\\]$1\\(');

      // reference URIs must also be escaped
      txt = txt.replace(/^ {0,3}\[([\S \t]*?)]:/gm, '\\[$1]:');

      return txt;
    }

    function parseList (node, type) {
      var txt = '';
      if (!node.hasChildNodes()) {
        return '';
      }
      var listItems       = node.childNodes,
          listItemsLenght = listItems.length,
          listNum = node.getAttribute('start') || 1;

      for (var i = 0; i < listItemsLenght; ++i) {
        if (typeof listItems[i].tagName === 'undefined' || listItems[i].tagName.toLowerCase() !== 'li') {
          continue;
        }

        // define the bullet to use in list
        var bullet = '';
        if (type === 'ol') {
          bullet = listNum.toString() + '. ';
        } else {
          bullet = '- ';
        }

        // parse list item
        txt += bullet + parseListItem(listItems[i]);
        ++listNum;
      }

      return txt.trim();
    }

    function parseListItem (node) {
      var listItemTxt = '';

      var children = node.childNodes,
          childrenLenght = children.length;

      for (var i = 0; i < childrenLenght; ++i) {
        listItemTxt += parseNode(children[i]);
      }
      // if it's only one liner, we need to add a newline at the end
      if (!/\n$/.test(listItemTxt)) {
        listItemTxt += '\n';
      } else {
        // it's multiparagraph, so we need to indent
        listItemTxt = listItemTxt
          .split('\n')
          .join('\n    ')
          .replace(/^ {4}$/gm, '')
          .replace(/\n\n+/g, '\n\n');
      }

      return listItemTxt;
    }

    function parseHr () {
      return '---';
    }

    function parseBlockquote (node) {
      var txt = '';
      if (node.hasChildNodes()) {
        var children = node.childNodes,
            childrenLength = children.length;

        for (var i = 0; i < childrenLength; ++i) {
          var innerTxt = parseNode(children[i]);

          if (innerTxt === '') {
            continue;
          }
          txt += innerTxt;
        }
      }
      // cleanup
      txt = txt.trim();
      txt = '> ' + txt.split('\n').join('\n> ');
      return txt;
    }

    function parseCodeSpan (node) {
      return '`' + node.innerHTML + '`';
    }

    function parseStrong (node) {
      var txt = '';
      if (node.hasChildNodes()) {
        txt += '**';
        var children = node.childNodes,
            childrenLength = children.length;
        for (var i = 0; i < childrenLength; ++i) {
          txt += parseNode(children[i]);
        }
        txt += '**';
      }
      return txt;
    }

    function parseEmphasis (node) {
      var txt = '';
      if (node.hasChildNodes()) {
        txt += '*';
        var children = node.childNodes,
            childrenLength = children.length;
        for (var i = 0; i < childrenLength; ++i) {
          txt += parseNode(children[i]);
        }
        txt += '*';
      }
      return txt;
    }

    function parseDel (node) {
      var txt = '';
      if (node.hasChildNodes()) {
        txt += '~~';
        var children = node.childNodes,
            childrenLength = children.length;
        for (var i = 0; i < childrenLength; ++i) {
          txt += parseNode(children[i]);
        }
        txt += '~~';
      }
      return txt;
    }

    function parseLinks (node) {
      var txt = '';
      if (node.hasChildNodes() && node.hasAttribute('href')) {
        var children = node.childNodes,
            childrenLength = children.length;
        txt = '[';
        for (var i = 0; i < childrenLength; ++i) {
          txt += parseNode(children[i]);
        }
        txt += '](';
        txt += '<' + node.getAttribute('href') + '>';
        if (node.hasAttribute('title')) {
          txt += ' "' + node.getAttribute('title') + '"';
        }
        txt += ')';
      }
      return txt;
    }

    function parseImage (node) {
      var txt = '';
      if (node.hasAttribute('src')) {
        txt += '![' + node.getAttribute('alt') + '](';
        txt += '<' + node.getAttribute('src') + '>';
        if (node.hasAttribute('width') && node.hasAttribute('height')) {
          txt += ' =' + node.getAttribute('width') + 'x' + node.getAttribute('height');
        }

        if (node.hasAttribute('title')) {
          txt += ' "' + node.getAttribute('title') + '"';
        }
        txt += ')';
      }
      return txt;
    }

    function parseHeader (node, headerLevel) {
      var headerMark = new Array(headerLevel + 1).join('#'),
          txt = '';

      if (node.hasChildNodes()) {
        txt = headerMark + ' ';
        var children = node.childNodes,
            childrenLength = children.length;

        for (var i = 0; i < childrenLength; ++i) {
          txt += parseNode(children[i]);
        }
      }
      return txt;
    }

    function parseParagraph (node) {
      var txt = '';
      if (node.hasChildNodes()) {
        var children = node.childNodes,
            childrenLength = children.length;
        for (var i = 0; i < childrenLength; ++i) {
          txt += parseNode(children[i]);
        }
      }

      // some text normalization
      txt = txt.trim();

      return txt;
    }

    function parsePreCode (node) {
      var lang = node.getAttribute('language'),
          num  = node.getAttribute('precodenum');
      return '```' + lang + '\n' + preList[num] + '\n```';
    }

    function parsePre (node) {
      var num  = node.getAttribute('prenum');
      return '<pre>' + preList[num] + '</pre>';
    }

    function parseTable (node) {

      var txt = '',
          tableArray = [[], []],
          headings   = node.querySelectorAll('thead>tr>th'),
          rows       = node.querySelectorAll('tbody>tr'),
          i, ii;
      for (i = 0; i < headings.length; ++i) {
        var headContent = parseTableCell(headings[i]),
            allign = '---';

        if (headings[i].hasAttribute('style')) {
          var style = headings[i].getAttribute('style').toLowerCase().replace(/\s/g, '');
          switch (style) {
            case 'text-align:left;':
              allign = ':---';
              break;
            case 'text-align:right;':
              allign = '---:';
              break;
            case 'text-align:center;':
              allign = ':---:';
              break;
          }
        }
        tableArray[0][i] = headContent.trim();
        tableArray[1][i] = allign;
      }

      for (i = 0; i < rows.length; ++i) {
        var r = tableArray.push([]) - 1,
            cols = rows[i].getElementsByTagName('td');

        for (ii = 0; ii < headings.length; ++ii) {
          var cellContent = ' ';
          if (typeof cols[ii] !== 'undefined') {
            cellContent = parseTableCell(cols[ii]);
          }
          tableArray[r].push(cellContent);
        }
      }

      var cellSpacesCount = 3;
      for (i = 0; i < tableArray.length; ++i) {
        for (ii = 0; ii < tableArray[i].length; ++ii) {
          var strLen = tableArray[i][ii].length;
          if (strLen > cellSpacesCount) {
            cellSpacesCount = strLen;
          }
        }
      }

      for (i = 0; i < tableArray.length; ++i) {
        for (ii = 0; ii < tableArray[i].length; ++ii) {
          if (i === 1) {
            if (tableArray[i][ii].slice(-1) === ':') {
              tableArray[i][ii] = showdown.helper.padEnd(tableArray[i][ii].slice(-1), cellSpacesCount - 1, '-') + ':';
            } else {
              tableArray[i][ii] = showdown.helper.padEnd(tableArray[i][ii], cellSpacesCount, '-');
            }
          } else {
            tableArray[i][ii] = showdown.helper.padEnd(tableArray[i][ii], cellSpacesCount);
          }
        }
        txt += '| ' + tableArray[i].join(' | ') + ' |\n';
      }

      return txt.trim();
    }

    function parseTableCell (node) {
      var txt = '';
      if (!node.hasChildNodes()) {
        return '';
      }
      var children = node.childNodes,
          childrenLength = children.length;

      for (var i = 0; i < childrenLength; ++i) {
        txt += parseNode(children[i], true);
      }
      return txt.trim();
    }

    function clean (node) {
      for (var n = 0; n < node.childNodes.length; ++n) {
        var child = node.childNodes[n];
        if (child.nodeType === 3) {
          if (!/\S/.test(child.nodeValue)) {
            node.removeChild(child);
            --n;
          } else {
            child.nodeValue = child.nodeValue.split('\n').join(' ');
            child.nodeValue = child.nodeValue.replace(/(\s)+/g, '$1');
          }
        } else if (child.nodeType === 1) {
          clean(child);
        }
      }
    }

    // find all pre tags and replace contents with placeholder
    // we need this so that we can remove all indentation from html
    // to ease up parsing
    function substitutePreCodeTags (doc) {

      var pres = doc.querySelectorAll('pre'),
          presPH = [];

      for (var i = 0; i < pres.length; ++i) {

        if (pres[i].childElementCount === 1 && pres[i].firstChild.tagName.toLowerCase() === 'code') {
          var content = pres[i].firstChild.innerHTML.trim(),
              language = pres[i].firstChild.getAttribute('data-language') || '';

          // if data-language attribute is not defined, then we look for class language-*
          if (language === '') {
            var classes = pres[i].firstChild.className.split(' ');
            for (var c = 0; c < classes.length; ++c) {
              var matches = classes[c].match(/^language-(.+)$/);
              if (matches !== null) {
                language = matches[1];
                break;
              }
            }
          }

          // unescape html entities in content
          content = showdown.helper.unescapeHTMLEntities(content);

          presPH.push(content);
          pres[i].outerHTML = '<precode language="' + language + '" precodenum="' + i.toString() + '"></precode>';
        } else {
          presPH.push(pres[i].innerHTML);
          pres[i].innerHTML = '';
          pres[i].setAttribute('prenum', i.toString());
        }
      }
      return presPH;
    }

    return mdDoc;
  };

  /**
   * Set an option of this Converter instance
   * @param {string} key
   * @param {*} value
   */
  this.setOption = function (key, value) {
    options[key] = value;
  };

  /**
   * Get the option of this Converter instance
   * @param {string} key
   * @returns {*}
   */
  this.getOption = function (key) {
    return options[key];
  };

  /**
   * Get the options of this Converter instance
   * @returns {{}}
   */
  this.getOptions = function () {
    return options;
  };

  /**
   * Add extension to THIS converter
   * @param {{}} extension
   * @param {string} [name=null]
   */
  this.addExtension = function (extension, name) {
    name = name || null;
    _parseExtension(extension, name);
  };

  /**
   * Use a global registered extension with THIS converter
   * @param {string} extensionName Name of the previously registered extension
   */
  this.useExtension = function (extensionName) {
    _parseExtension(extensionName);
  };

  /**
   * Set the flavor THIS converter should use
   * @param {string} name
   */
  this.setFlavor = function (name) {
    if (!flavor.hasOwnProperty(name)) {
      throw Error(name + ' flavor was not found');
    }
    var preset = flavor[name];
    setConvFlavor = name;
    for (var option in preset) {
      if (preset.hasOwnProperty(option)) {
        options[option] = preset[option];
      }
    }
  };

  /**
   * Get the currently set flavor of this converter
   * @returns {string}
   */
  this.getFlavor = function () {
    return setConvFlavor;
  };

  /**
   * Remove an extension from THIS converter.
   * Note: This is a costly operation. It's better to initialize a new converter
   * and specify the extensions you wish to use
   * @param {Array} extension
   */
  this.removeExtension = function (extension) {
    if (!showdown.helper.isArray(extension)) {
      extension = [extension];
    }
    for (var a = 0; a < extension.length; ++a) {
      var ext = extension[a];
      for (var i = 0; i < langExtensions.length; ++i) {
        if (langExtensions[i] === ext) {
          langExtensions[i].splice(i, 1);
        }
      }
      for (var ii = 0; ii < outputModifiers.length; ++i) {
        if (outputModifiers[ii] === ext) {
          outputModifiers[ii].splice(i, 1);
        }
      }
    }
  };

  /**
   * Get all extension of THIS converter
   * @returns {{language: Array, output: Array}}
   */
  this.getAllExtensions = function () {
    return {
      language: langExtensions,
      output: outputModifiers
    };
  };

  /**
   * Get the metadata of the previously parsed document
   * @param raw
   * @returns {string|{}}
   */
  this.getMetadata = function (raw) {
    if (raw) {
      return metadata.raw;
    } else {
      return metadata.parsed;
    }
  };

  /**
   * Get the metadata format of the previously parsed document
   * @returns {string}
   */
  this.getMetadataFormat = function () {
    return metadata.format;
  };

  /**
   * Private: set a single key, value metadata pair
   * @param {string} key
   * @param {string} value
   */
  this._setMetadataPair = function (key, value) {
    metadata.parsed[key] = value;
  };

  /**
   * Private: set metadata format
   * @param {string} format
   */
  this._setMetadataFormat = function (format) {
    metadata.format = format;
  };

  /**
   * Private: set metadata raw text
   * @param {string} raw
   */
  this._setMetadataRaw = function (raw) {
    metadata.raw = raw;
  };
};