QMAI/extension/Turndown.js

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
  typeof define === 'function' && define.amd ? define(factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, global.TurndownService = factory());
})(this, (function () { 'use strict';

  function extend(destination) {
    for (var i = 1; i < arguments.length; i++) {
      var source = arguments[i];
      for (var key in source) {
        if (Object.prototype.hasOwnProperty.call(source, key)) destination[key] = source[key];
      }
    }
    return destination;
  }
  function repeat(character, count) {
    return Array(count + 1).join(character);
  }
  function trimLeadingNewlines(string) {
    return string.replace(/^\n*/, '');
  }
  function trimTrailingNewlines(string) {
    // avoid match-at-end regexp bottleneck, see #370
    var indexEnd = string.length;
    while (indexEnd > 0 && string[indexEnd - 1] === '\n') indexEnd--;
    return string.substring(0, indexEnd);
  }
  function trimNewlines(string) {
    return trimTrailingNewlines(trimLeadingNewlines(string));
  }
  var blockElements = ['ADDRESS', 'ARTICLE', 'ASIDE', 'AUDIO', 'BLOCKQUOTE', 'BODY', 'CANVAS', 'CENTER', 'DD', 'DIR', 'DIV', 'DL', 'DT', 'FIELDSET', 'FIGCAPTION', 'FIGURE', 'FOOTER', 'FORM', 'FRAMESET', 'H1', 'H2', 'H3', 'H4', 'H5', 'H6', 'HEADER', 'HGROUP', 'HR', 'HTML', 'ISINDEX', 'LI', 'MAIN', 'MENU', 'NAV', 'NOFRAMES', 'NOSCRIPT', 'OL', 'OUTPUT', 'P', 'PRE', 'SECTION', 'TABLE', 'TBODY', 'TD', 'TFOOT', 'TH', 'THEAD', 'TR', 'UL'];
  function isBlock(node) {
    return is(node, blockElements);
  }
  var voidElements = ['AREA', 'BASE', 'BR', 'COL', 'COMMAND', 'EMBED', 'HR', 'IMG', 'INPUT', 'KEYGEN', 'LINK', 'META', 'PARAM', 'SOURCE', 'TRACK', 'WBR'];
  function isVoid(node) {
    return is(node, voidElements);
  }
  function hasVoid(node) {
    return has(node, voidElements);
  }
  var meaningfulWhenBlankElements = ['A', 'TABLE', 'THEAD', 'TBODY', 'TFOOT', 'TH', 'TD', 'IFRAME', 'SCRIPT', 'AUDIO', 'VIDEO'];
  function isMeaningfulWhenBlank(node) {
    return is(node, meaningfulWhenBlankElements);
  }
  function hasMeaningfulWhenBlank(node) {
    return has(node, meaningfulWhenBlankElements);
  }
  function is(node, tagNames) {
    return tagNames.indexOf(node.nodeName) >= 0;
  }
  function has(node, tagNames) {
    return node.getElementsByTagName && tagNames.some(function (tagName) {
      return node.getElementsByTagName(tagName).length;
    });
  }
  var markdownEscapes = [[/\\/g, '\\\\'], [/\*/g, '\\*'], [/^-/g, '\\-'], [/^\+ /g, '\\+ '], [/^(=+)/g, '\\$1'], [/^(#{1,6}) /g, '\\$1 '], [/`/g, '\\`'], [/^~~~/g, '\\~~~'], [/\[/g, '\\['], [/\]/g, '\\]'], [/^>/g, '\\>'], [/_/g, '\\_'], [/^(\d+)\. /g, '$1\\. ']];
  function escapeMarkdown(string) {
    return markdownEscapes.reduce(function (accumulator, escape) {
      return accumulator.replace(escape[0], escape[1]);
    }, string);
  }

  var rules = {};
  rules.paragraph = {
    filter: 'p',
    replacement: function (content) {
      return '\n\n' + content + '\n\n';
    }
  };
  rules.lineBreak = {
    filter: 'br',
    replacement: function (content, node, options) {
      return options.br + '\n';
    }
  };
  rules.heading = {
    filter: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'],
    replacement: function (content, node, options) {
      var hLevel = Number(node.nodeName.charAt(1));
      if (options.headingStyle === 'setext' && hLevel < 3) {
        var underline = repeat(hLevel === 1 ? '=' : '-', content.length);
        return '\n\n' + content + '\n' + underline + '\n\n';
      } else {
        return '\n\n' + repeat('#', hLevel) + ' ' + content + '\n\n';
      }
    }
  };
  rules.blockquote = {
    filter: 'blockquote',
    replacement: function (content) {
      content = trimNewlines(content).replace(/^/gm, '> ');
      return '\n\n' + content + '\n\n';
    }
  };
  rules.list = {
    filter: ['ul', 'ol'],
    replacement: function (content, node) {
      var parent = node.parentNode;
      if (parent.nodeName === 'LI' && parent.lastElementChild === node) {
        return '\n' + content;
      } else {
        return '\n\n' + content + '\n\n';
      }
    }
  };
  rules.listItem = {
    filter: 'li',
    replacement: function (content, node, options) {
      var prefix = options.bulletListMarker + '   ';
      var parent = node.parentNode;
      if (parent.nodeName === 'OL') {
        var start = parent.getAttribute('start');
        var index = Array.prototype.indexOf.call(parent.children, node);
        prefix = (start ? Number(start) + index : index + 1) + '.  ';
      }
      var isParagraph = /\n$/.test(content);
      content = trimNewlines(content) + (isParagraph ? '\n' : '');
      content = content.replace(/\n/gm, '\n' + ' '.repeat(prefix.length)); // indent
      return prefix + content + (node.nextSibling ? '\n' : '');
    }
  };
  rules.indentedCodeBlock = {
    filter: function (node, options) {
      return options.codeBlockStyle === 'indented' && node.nodeName === 'PRE' && node.firstChild && node.firstChild.nodeName === 'CODE';
    },
    replacement: function (content, node, options) {
      return '\n\n    ' + node.firstChild.textContent.replace(/\n/g, '\n    ') + '\n\n';
    }
  };
  rules.fencedCodeBlock = {
    filter: function (node, options) {
      return options.codeBlockStyle === 'fenced' && node.nodeName === 'PRE' && node.firstChild && node.firstChild.nodeName === 'CODE';
    },
    replacement: function (content, node, options) {
      var className = node.firstChild.getAttribute('class') || '';
      var language = (className.match(/language-(\S+)/) || [null, ''])[1];
      var code = node.firstChild.textContent;
      var fenceChar = options.fence.charAt(0);
      var fenceSize = 3;
      var fenceInCodeRegex = new RegExp('^' + fenceChar + '{3,}', 'gm');
      var match;
      while (match = fenceInCodeRegex.exec(code)) {
        if (match[0].length >= fenceSize) {
          fenceSize = match[0].length + 1;
        }
      }
      var fence = repeat(fenceChar, fenceSize);
      return '\n\n' + fence + language + '\n' + code.replace(/\n$/, '') + '\n' + fence + '\n\n';
    }
  };
  rules.horizontalRule = {
    filter: 'hr',
    replacement: function (content, node, options) {
      return '\n\n' + options.hr + '\n\n';
    }
  };
  rules.inlineLink = {
    filter: function (node, options) {
      return options.linkStyle === 'inlined' && node.nodeName === 'A' && node.getAttribute('href');
    },
    replacement: function (content, node) {
      var href = escapeLinkDestination(node.getAttribute('href'));
      var title = escapeLinkTitle(cleanAttribute(node.getAttribute('title')));
      var titlePart = title ? ' "' + title + '"' : '';
      return '[' + content + '](' + href + titlePart + ')';
    }
  };
  rules.referenceLink = {
    filter: function (node, options) {
      return options.linkStyle === 'referenced' && node.nodeName === 'A' && node.getAttribute('href');
    },
    replacement: function (content, node, options) {
      var href = escapeLinkDestination(node.getAttribute('href'));
      var title = cleanAttribute(node.getAttribute('title'));
      if (title) title = ' "' + escapeLinkTitle(title) + '"';
      var replacement;
      var reference;
      switch (options.linkReferenceStyle) {
        case 'collapsed':
          replacement = '[' + content + '][]';
          reference = '[' + content + ']: ' + href + title;
          break;
        case 'shortcut':
          replacement = '[' + content + ']';
          reference = '[' + content + ']: ' + href + title;
          break;
        default:
          var id = this.references.length + 1;
          replacement = '[' + content + '][' + id + ']';
          reference = '[' + id + ']: ' + href + title;
      }
      this.references.push(reference);
      return replacement;
    },
    references: [],
    append: function (options) {
      var references = '';
      if (this.references.length) {
        references = '\n\n' + this.references.join('\n') + '\n\n';
        this.references = []; // Reset references
      }
      return references;
    }
  };
  rules.emphasis = {
    filter: ['em', 'i'],
    replacement: function (content, node, options) {
      if (!content.trim()) return '';
      return options.emDelimiter + content + options.emDelimiter;
    }
  };
  rules.strong = {
    filter: ['strong', 'b'],
    replacement: function (content, node, options) {
      if (!content.trim()) return '';
      return options.strongDelimiter + content + options.strongDelimiter;
    }
  };
  rules.code = {
    filter: function (node) {
      var hasSiblings = node.previousSibling || node.nextSibling;
      var isCodeBlock = node.parentNode.nodeName === 'PRE' && !hasSiblings;
      return node.nodeName === 'CODE' && !isCodeBlock;
    },
    replacement: function (content) {
      if (!content) return '';
      content = content.replace(/\r?\n|\r/g, ' ');
      var extraSpace = /^`|^ .*?[^ ].* $|`$/.test(content) ? ' ' : '';
      var delimiter = '`';
      var matches = content.match(/`+/gm) || [];
      while (matches.indexOf(delimiter) !== -1) delimiter = delimiter + '`';
      return delimiter + extraSpace + content + extraSpace + delimiter;
    }
  };
  rules.image = {
    filter: 'img',
    replacement: function (content, node) {
      var alt = escapeMarkdown(cleanAttribute(node.getAttribute('alt')));
      var src = escapeLinkDestination(node.getAttribute('src') || '');
      var title = cleanAttribute(node.getAttribute('title'));
      var titlePart = title ? ' "' + escapeLinkTitle(title) + '"' : '';
      return src ? '![' + alt + ']' + '(' + src + titlePart + ')' : '';
    }
  };
  function cleanAttribute(attribute) {
    return attribute ? attribute.replace(/(\n+\s*)+/g, '\n') : '';
  }
  function escapeLinkDestination(destination) {
    var escaped = destination.replace(/([<>()])/g, '\\$1');
    return escaped.indexOf(' ') >= 0 ? '<' + escaped + '>' : escaped;
  }
  function escapeLinkTitle(title) {
    return title.replace(/"/g, '\\"');
  }

  /**
   * Manages a collection of rules used to convert HTML to Markdown
   */

  function Rules(options) {
    this.options = options;
    this._keep = [];
    this._remove = [];
    this.blankRule = {
      replacement: options.blankReplacement
    };
    this.keepReplacement = options.keepReplacement;
    this.defaultRule = {
      replacement: options.defaultReplacement
    };
    this.array = [];
    for (var key in options.rules) this.array.push(options.rules[key]);
  }
  Rules.prototype = {
    add: function (key, rule) {
      this.array.unshift(rule);
    },
    keep: function (filter) {
      this._keep.unshift({
        filter: filter,
        replacement: this.keepReplacement
      });
    },
    remove: function (filter) {
      this._remove.unshift({
        filter: filter,
        replacement: function () {
          return '';
        }
      });
    },
    forNode: function (node) {
      if (node.isBlank) return this.blankRule;
      var rule;
      if (rule = findRule(this.array, node, this.options)) return rule;
      if (rule = findRule(this._keep, node, this.options)) return rule;
      if (rule = findRule(this._remove, node, this.options)) return rule;
      return this.defaultRule;
    },
    forEach: function (fn) {
      for (var i = 0; i < this.array.length; i++) fn(this.array[i], i);
    }
  };
  function findRule(rules, node, options) {
    for (var i = 0; i < rules.length; i++) {
      var rule = rules[i];
      if (filterValue(rule, node, options)) return rule;
    }
    return undefined;
  }
  function filterValue(rule, node, options) {
    var filter = rule.filter;
    if (typeof filter === 'string') {
      if (filter === node.nodeName.toLowerCase()) return true;
    } else if (Array.isArray(filter)) {
      if (filter.indexOf(node.nodeName.toLowerCase()) > -1) return true;
    } else if (typeof filter === 'function') {
      if (filter.call(rule, node, options)) return true;
    } else {
      throw new TypeError('`filter` needs to be a string, array, or function');
    }
  }

  /**
   * The collapseWhitespace function is adapted from collapse-whitespace
   * by Luc Thevenard.
   *
   * The MIT License (MIT)
   *
   * Copyright (c) 2014 Luc Thevenard <lucthevenard@gmail.com>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */

  /**
   * collapseWhitespace(options) removes extraneous whitespace from an the given element.
   *
   * @param {Object} options
   */
  function collapseWhitespace(options) {
    var element = options.element;
    var isBlock = options.isBlock;
    var isVoid = options.isVoid;
    var isPre = options.isPre || function (node) {
      return node.nodeName === 'PRE';
    };
    if (!element.firstChild || isPre(element)) return;
    var prevText = null;
    var keepLeadingWs = false;
    var prev = null;
    var node = next(prev, element, isPre);
    while (node !== element) {
      if (node.nodeType === 3 || node.nodeType === 4) {
        // Node.TEXT_NODE or Node.CDATA_SECTION_NODE
        var text = node.data.replace(/[ \r\n\t]+/g, ' ');
        if ((!prevText || / $/.test(prevText.data)) && !keepLeadingWs && text[0] === ' ') {
          text = text.substr(1);
        }

        // `text` might be empty at this point.
        if (!text) {
          node = remove(node);
          continue;
        }
        node.data = text;
        prevText = node;
      } else if (node.nodeType === 1) {
        // Node.ELEMENT_NODE
        if (isBlock(node) || node.nodeName === 'BR') {
          if (prevText) {
            prevText.data = prevText.data.replace(/ $/, '');
          }
          prevText = null;
          keepLeadingWs = false;
        } else if (isVoid(node) || isPre(node)) {
          // Avoid trimming space around non-block, non-BR void elements and inline PRE.
          prevText = null;
          keepLeadingWs = true;
        } else if (prevText) {
          // Drop protection if set previously.
          keepLeadingWs = false;
        }
      } else {
        node = remove(node);
        continue;
      }
      var nextNode = next(prev, node, isPre);
      prev = node;
      node = nextNode;
    }
    if (prevText) {
      prevText.data = prevText.data.replace(/ $/, '');
      if (!prevText.data) {
        remove(prevText);
      }
    }
  }

  /**
   * remove(node) removes the given node from the DOM and returns the
   * next node in the sequence.
   *
   * @param {Node} node
   * @return {Node} node
   */
  function remove(node) {
    var next = node.nextSibling || node.parentNode;
    node.parentNode.removeChild(node);
    return next;
  }

  /**
   * next(prev, current, isPre) returns the next node in the sequence, given the
   * current and previous nodes.
   *
   * @param {Node} prev
   * @param {Node} current
   * @param {Function} isPre
   * @return {Node}
   */
  function next(prev, current, isPre) {
    if (prev && prev.parentNode === current || isPre(current)) {
      return current.nextSibling || current.parentNode;
    }
    return current.firstChild || current.nextSibling || current.parentNode;
  }

  /*
   * Set up window for Node.js
   */

  var root = typeof window !== 'undefined' ? window : {};

  /*
   * Parsing HTML strings
   */

  function canParseHTMLNatively() {
    var Parser = root.DOMParser;
    var canParse = false;

    // Adapted from https://gist.github.com/1129031
    // Firefox/Opera/IE throw errors on unsupported types
    try {
      // WebKit returns null on unsupported types
      if (new Parser().parseFromString('', 'text/html')) {
        canParse = true;
      }
    } catch (e) {}
    return canParse;
  }
  function createHTMLParser() {
    var Parser = function () {};
    {
      if (shouldUseActiveX()) {
        Parser.prototype.parseFromString = function (string) {
          var doc = new window.ActiveXObject('htmlfile');
          doc.designMode = 'on'; // disable on-page scripts
          doc.open();
          doc.write(string);
          doc.close();
          return doc;
        };
      } else {
        Parser.prototype.parseFromString = function (string) {
          var doc = document.implementation.createHTMLDocument('');
          doc.open();
          doc.write(string);
          doc.close();
          return doc;
        };
      }
    }
    return Parser;
  }
  function shouldUseActiveX() {
    var useActiveX = false;
    try {
      document.implementation.createHTMLDocument('').open();
    } catch (e) {
      if (root.ActiveXObject) useActiveX = true;
    }
    return useActiveX;
  }
  var HTMLParser = canParseHTMLNatively() ? root.DOMParser : createHTMLParser();

  function RootNode(input, options) {
    var root;
    if (typeof input === 'string') {
      var doc = htmlParser().parseFromString(
      // DOM parsers arrange elements in the <head> and <body>.
      // Wrapping in a custom element ensures elements are reliably arranged in
      // a single element.
      '<x-turndown id="turndown-root">' + input + '</x-turndown>', 'text/html');
      root = doc.getElementById('turndown-root');
    } else {
      root = input.cloneNode(true);
    }
    collapseWhitespace({
      element: root,
      isBlock: isBlock,
      isVoid: isVoid,
      isPre: options.preformattedCode ? isPreOrCode : null
    });
    return root;
  }
  var _htmlParser;
  function htmlParser() {
    _htmlParser = _htmlParser || new HTMLParser();
    return _htmlParser;
  }
  function isPreOrCode(node) {
    return node.nodeName === 'PRE' || node.nodeName === 'CODE';
  }

  function Node(node, options) {
    node.isBlock = isBlock(node);
    node.isCode = node.nodeName === 'CODE' || node.parentNode.isCode;
    node.isBlank = isBlank(node);
    node.flankingWhitespace = flankingWhitespace(node, options);
    return node;
  }
  function isBlank(node) {
    return !isVoid(node) && !isMeaningfulWhenBlank(node) && /^\s*$/i.test(node.textContent) && !hasVoid(node) && !hasMeaningfulWhenBlank(node);
  }
  function flankingWhitespace(node, options) {
    if (node.isBlock || options.preformattedCode && node.isCode) {
      return {
        leading: '',
        trailing: ''
      };
    }
    var edges = edgeWhitespace(node.textContent);

    // abandon leading ASCII WS if left-flanked by ASCII WS
    if (edges.leadingAscii && isFlankedByWhitespace('left', node, options)) {
      edges.leading = edges.leadingNonAscii;
    }

    // abandon trailing ASCII WS if right-flanked by ASCII WS
    if (edges.trailingAscii && isFlankedByWhitespace('right', node, options)) {
      edges.trailing = edges.trailingNonAscii;
    }
    return {
      leading: edges.leading,
      trailing: edges.trailing
    };
  }
  function edgeWhitespace(string) {
    var m = string.match(/^(([ \t\r\n]*)(\s*))(?:(?=\S)[\s\S]*\S)?((\s*?)([ \t\r\n]*))$/);
    return {
      leading: m[1],
      // whole string for whitespace-only strings
      leadingAscii: m[2],
      leadingNonAscii: m[3],
      trailing: m[4],
      // empty for whitespace-only strings
      trailingNonAscii: m[5],
      trailingAscii: m[6]
    };
  }
  function isFlankedByWhitespace(side, node, options) {
    var sibling;
    var regExp;
    var isFlanked;
    if (side === 'left') {
      sibling = node.previousSibling;
      regExp = / $/;
    } else {
      sibling = node.nextSibling;
      regExp = /^ /;
    }
    if (sibling) {
      if (sibling.nodeType === 3) {
        isFlanked = regExp.test(sibling.nodeValue);
      } else if (options.preformattedCode && sibling.nodeName === 'CODE') {
        isFlanked = false;
      } else if (sibling.nodeType === 1 && !isBlock(sibling)) {
        isFlanked = regExp.test(sibling.textContent);
      }
    }
    return isFlanked;
  }

  var reduce = Array.prototype.reduce;
  function TurndownService(options) {
    if (!(this instanceof TurndownService)) return new TurndownService(options);
    var defaults = {
      rules: rules,
      headingStyle: 'setext',
      hr: '* * *',
      bulletListMarker: '*',
      codeBlockStyle: 'indented',
      fence: '```',
      emDelimiter: '_',
      strongDelimiter: '**',
      linkStyle: 'inlined',
      linkReferenceStyle: 'full',
      br: '  ',
      preformattedCode: false,
      blankReplacement: function (content, node) {
        return node.isBlock ? '\n\n' : '';
      },
      keepReplacement: function (content, node) {
        return node.isBlock ? '\n\n' + node.outerHTML + '\n\n' : node.outerHTML;
      },
      defaultReplacement: function (content, node) {
        return node.isBlock ? '\n\n' + content + '\n\n' : content;
      }
    };
    this.options = extend({}, defaults, options);
    this.rules = new Rules(this.options);
  }
  TurndownService.prototype = {
    /**
     * The entry point for converting a string or DOM node to Markdown
     * @public
     * @param {String|HTMLElement} input The string or DOM node to convert
     * @returns A Markdown representation of the input
     * @type String
     */

    turndown: function (input) {
      if (!canConvert(input)) {
        throw new TypeError(input + ' is not a string, or an element/document/fragment node.');
      }
      if (input === '') return '';
      var output = process.call(this, new RootNode(input, this.options));
      return postProcess.call(this, output);
    },
    /**
     * Add one or more plugins
     * @public
     * @param {Function|Array} plugin The plugin or array of plugins to add
     * @returns The Turndown instance for chaining
     * @type Object
     */

    use: function (plugin) {
      if (Array.isArray(plugin)) {
        for (var i = 0; i < plugin.length; i++) this.use(plugin[i]);
      } else if (typeof plugin === 'function') {
        plugin(this);
      } else {
        throw new TypeError('plugin must be a Function or an Array of Functions');
      }
      return this;
    },
    /**
     * Adds a rule
     * @public
     * @param {String} key The unique key of the rule
     * @param {Object} rule The rule
     * @returns The Turndown instance for chaining
     * @type Object
     */

    addRule: function (key, rule) {
      this.rules.add(key, rule);
      return this;
    },
    /**
     * Keep a node (as HTML) that matches the filter
     * @public
     * @param {String|Array|Function} filter The unique key of the rule
     * @returns The Turndown instance for chaining
     * @type Object
     */

    keep: function (filter) {
      this.rules.keep(filter);
      return this;
    },
    /**
     * Remove a node that matches the filter
     * @public
     * @param {String|Array|Function} filter The unique key of the rule
     * @returns The Turndown instance for chaining
     * @type Object
     */

    remove: function (filter) {
      this.rules.remove(filter);
      return this;
    },
    /**
     * Escapes Markdown syntax
     * @public
     * @param {String} string The string to escape
     * @returns A string with Markdown syntax escaped
     * @type String
     */

    escape: function (string) {
      return escapeMarkdown(string);
    }
  };

  /**
   * Reduces a DOM node down to its Markdown string equivalent
   * @private
   * @param {HTMLElement} parentNode The node to convert
   * @returns A Markdown representation of the node
   * @type String
   */

  function process(parentNode) {
    var self = this;
    return reduce.call(parentNode.childNodes, function (output, node) {
      node = new Node(node, self.options);
      var replacement = '';
      if (node.nodeType === 3) {
        replacement = node.isCode ? node.nodeValue : self.escape(node.nodeValue);
      } else if (node.nodeType === 1) {
        replacement = replacementForNode.call(self, node);
      }
      return join(output, replacement);
    }, '');
  }

  /**
   * Appends strings as each rule requires and trims the output
   * @private
   * @param {String} output The conversion output
   * @returns A trimmed version of the ouput
   * @type String
   */

  function postProcess(output) {
    var self = this;
    this.rules.forEach(function (rule) {
      if (typeof rule.append === 'function') {
        output = join(output, rule.append(self.options));
      }
    });
    return output.replace(/^[\t\r\n]+/, '').replace(/[\t\r\n\s]+$/, '');
  }

  /**
   * Converts an element node to its Markdown equivalent
   * @private
   * @param {HTMLElement} node The node to convert
   * @returns A Markdown representation of the node
   * @type String
   */

  function replacementForNode(node) {
    var rule = this.rules.forNode(node);
    var content = process.call(this, node);
    var whitespace = node.flankingWhitespace;
    if (whitespace.leading || whitespace.trailing) content = content.trim();
    return whitespace.leading + rule.replacement(content, node, this.options) + whitespace.trailing;
  }

  /**
   * Joins replacement to the current output with appropriate number of new lines
   * @private
   * @param {String} output The current conversion output
   * @param {String} replacement The string to append to the output
   * @returns Joined output
   * @type String
   */

  function join(output, replacement) {
    var s1 = trimTrailingNewlines(output);
    var s2 = trimLeadingNewlines(replacement);
    var nls = Math.max(output.length - s1.length, replacement.length - s2.length);
    var separator = '\n\n'.substring(0, nls);
    return s1 + separator + s2;
  }

  /**
   * Determines whether an input can be converted
   * @private
   * @param {String|HTMLElement} input Describe this parameter
   * @returns Describe what it returns
   * @type String|Object|Array|Boolean|Number
   */

  function canConvert(input) {
    return input != null && (typeof input === 'string' || input.nodeType && (input.nodeType === 1 || input.nodeType === 9 || input.nodeType === 11));
  }

  return TurndownService;

}));