/**
 * https://github.com/mixmark-io/turndown
 * v7.2.0 modified by SnappyMail to be ES2020
 */

const TurndownService = (() => {

  const repeat = (character, count) => Array(count + 1).join(character),

  trimLeadingNewlines = string => string.replace(/^\n*/, ''),

  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)
  },

  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'
  ],

  isBlock = node => is(node, blockElements),

  voidElements = [
    'AREA', 'BASE', 'BR', 'COL', 'COMMAND', 'EMBED', 'HR', 'IMG', 'INPUT',
    'KEYGEN', 'LINK', 'META', 'PARAM', 'SOURCE', 'TRACK', 'WBR'
  ],

  isVoid = node => is(node, voidElements),

  hasVoid = node => has(node, voidElements),

  meaningfulWhenBlankElements = [
    'A', 'TABLE', 'THEAD', 'TBODY', 'TFOOT', 'TH', 'TD', 'IFRAME', 'SCRIPT',
    'AUDIO', 'VIDEO'
  ],

  isMeaningfulWhenBlank = node => is(node, meaningfulWhenBlankElements),

  hasMeaningfulWhenBlank = node => has(node, meaningfulWhenBlankElements),

  is = (node, tagNames) => tagNames.indexOf(node.nodeName) >= 0,

  has = (node, tagNames) =>
    (
      node.getElementsByTagName &&
      tagNames.some(tagName => node.getElementsByTagName(tagName).length)
    ),

  rules = {

    paragraph: {
      filter: 'p',

      replacement: content => '\n\n' + content + '\n\n'
    },

    lineBreak: {
      filter: 'br',

      replacement: (content, node, options) => options.br + '\n'
    },

    heading: {
      filter: ['h1', 'h2', 'h3', 'h4', 'h5', 'h6'],

      replacement: (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'
        }
        return '\n\n' + repeat('#', hLevel) + ' ' + content + '\n\n'
      }
    },

    blockquote: {
      filter: 'blockquote',

      replacement: (content) => {
        content = content.replace(/^\n+|\n+$/g, '');
        content = content.replace(/^/gm, '> ');
        return '\n\n' + content + '\n\n'
      }
    },

    list: {
      filter: ['ul', 'ol'],

      replacement: (content, node) => {
        var parent = node.parentNode;
        if (parent.nodeName === 'LI' && parent.lastElementChild === node) {
          return '\n' + content
        }
        return '\n\n' + content + '\n\n'
      }
    },

    listItem: {
      filter: 'li',

      replacement: (content, node, options) => {
        content = content
          .replace(/^\n+/, '') // remove leading newlines
          .replace(/\n+$/, '\n') // replace trailing newlines with just a single one
          .replace(/\n/gm, '\n    '); // indent
        var prefix = options.bulletListMarker + '   ';
        var parent = node.parentNode;
        if (parent.nodeName === 'OL') {
          var start = parent.getAttribute('start');
          var index = Array.prototype.indexOf.call(parent.children, node);
          prefix = (start ? Number(start) + index : index + 1) + '.  ';
        }
        return (
          prefix + content + (node.nextSibling && !/\n$/.test(content) ? '\n' : '')
        )
      }
    },

    indentedCodeBlock: {
      filter: (node, options) =>
        (
          options.codeBlockStyle === 'indented' &&
          node.nodeName === 'PRE' &&
          node.firstChild &&
          node.firstChild.nodeName === 'CODE'
        )
      ,

      replacement: (content, node) =>
        (
          '\n\n    ' +
          node.firstChild.textContent.replace(/\n/g, '\n    ') +
          '\n\n'
        )
    },

    fencedCodeBlock: {
      filter: (node, options) =>
        (
          options.codeBlockStyle === 'fenced' &&
          node.nodeName === 'PRE' &&
          node.firstChild &&
          node.firstChild.nodeName === 'CODE'
        )
      ,

      replacement: (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'
        )
      }
    },

    horizontalRule: {
      filter: 'hr',

      replacement: (content, node, options) => '\n\n' + options.hr + '\n\n'
    },

    inlineLink: {
      filter: (node, options) =>
        (
          options.linkStyle === 'inlined' &&
          node.nodeName === 'A' &&
          node.getAttribute('href')
        )
      ,

      replacement: (content, node) => {
        var href = node.getAttribute('href');
        if (href) href = href.replace(/([()])/g, '\\$1');
        var title = cleanAttribute(node.getAttribute('title'));
        if (title) title = ' "' + title.replace(/"/g, '\\"') + '"';
        return '[' + content + '](' + href + title + ')'
      }
    },

    referenceLink: {
      filter: (node, options) =>
        (
          options.linkStyle === 'referenced' &&
          node.nodeName === 'A' &&
          node.getAttribute('href')
        )
      ,

      replacement(content, node, options) {
        var href = node.getAttribute('href');
        var title = cleanAttribute(node.getAttribute('title'));
        if (title) title = ' "' + 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() {
        var references = '';
        if (this.references.length) {
          references = '\n\n' + this.references.join('\n') + '\n\n';
          this.references = []; // Reset references
        }
        return references
      }
    },

    emphasis: {
      filter: ['em', 'i'],

      replacement: (content, node, options) => {
        if (!content.trim()) return ''
        return options.emDelimiter + content + options.emDelimiter
      }
    },

    strong: {
      filter: ['strong', 'b'],

      replacement: (content, node, options) => {
        if (!content.trim()) return ''
        return options.strongDelimiter + content + options.strongDelimiter
      }
    },

    code: {
      filter: (node) => {
        var hasSiblings = node.previousSibling || node.nextSibling;
        var isCodeBlock = node.parentNode.nodeName === 'PRE' && !hasSiblings;

        return node.nodeName === 'CODE' && !isCodeBlock
      },

      replacement: (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
      }
    },

    image: {
      filter: 'img',

      replacement: (content, node) => {
        var alt = cleanAttribute(node.getAttribute('alt'));
        var src = node.getAttribute('src') || '';
        var title = cleanAttribute(node.getAttribute('title'));
        var titlePart = title ? ' "' + title + '"' : '';
        return src ? '![' + alt + ']' + '(' + src + titlePart + ')' : ''
      }
    },

    style: {
      filter: 'style',
      replacement: () => ''
    }
  },

  cleanAttribute = (attribute) => attribute ? attribute.replace(/(\n+\s*)+/g, '\n') : '';

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

  class Rules
  {
    constructor(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]);
    }

    add(key, rule) {
      this.array.unshift(rule);
    }

    keep(filter) {
      this._keep.unshift({
        filter: filter,
        replacement: this.keepReplacement
      });
    }

    remove(filter) {
      this._remove.unshift({
        filter: filter,
        replacement: () => ''
      });
    }

    forNode(node) {
      if (node.isBlank) return this.blankRule
      return findRule(this.array, node, this.options)
        || findRule(this._keep, node, this.options)
        || findRule(this._remove, node, this.options)
        || this.defaultRule
    }

    forEach(fn) {
      for (var i = 0; i < this.array.length; i++) fn(this.array[i], i);
    }
  }

  const findRule = (rules, node, options) => {
    for (var i = 0; i < rules.length; i++) {
      var rule = rules[i];
      if (filterValue(rule, node, options)) return rule
    }
    return void 0
  },

  filterValue = (rule, node, options) => {
    var filter = rule.filter;
    if (typeof filter === 'string') {
      return (filter === node.nodeName.toLowerCase())
    } else if (Array.isArray(filter)) {
      return (filter.indexOf(node.nodeName.toLowerCase()) > -1)
    } else if (typeof filter === 'function') {
      return !!filter.call(rule, node, options)
    }
    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
   */
  collapseWhitespace = (options) => {
    var element = options.element;
    var isBlock = options.isBlock;
    var isVoid = options.isVoid;
    var isPre = options.isPre || ((node) => 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
   */
  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}
   */
  next = (prev, current, isPre) => {
    if ((prev && prev.parentNode === current) || isPre(current)) {
      return current.nextSibling || current.parentNode
    }

    return current.firstChild || current.nextSibling || current.parentNode
  },

  /*
   * Parsing HTML strings
   */

  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;
  const htmlParser = () => {
    _htmlParser = _htmlParser || new DOMParser();
    return _htmlParser
  },

  isPreOrCode = (node) => node.nodeName === 'PRE' || node.nodeName === 'CODE',

  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
  },

  isBlank = (node) =>
    (
      !isVoid(node) &&
      !isMeaningfulWhenBlank(node) &&
      /^\s*$/i.test(node.textContent) &&
      !hasVoid(node) &&
      !hasMeaningfulWhenBlank(node)
    )
  ,

  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 }
  },

  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]
    }
  },

  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
  },

  reduce = Array.prototype.reduce,
  escapes = [
    [/\\/g, '\\\\'],
    [/\*/g, '\\*'],
    [/^-/g, '\\-'],
    [/^\+ /g, '\\+ '],
    [/^(=+)/g, '\\$1'],
    [/^(#{1,6}) /g, '\\$1 '],
    [/`/g, '\\`'],
    [/^~~~/g, '\\~~~'],
    [/\[/g, '\\['],
    [/\]/g, '\\]'],
    [/^>/g, '\\>'],
    [/_/g, '\\_'],
    [/^(\d+)\. /g, '$1\\. ']
  ];

  class TurndownService
  {
    constructor(options) {
      this.options = Object.assign({
        rules: rules,
        headingStyle: 'setext',
        hr: '* * *',
        bulletListMarker: '*',
        codeBlockStyle: 'indented',
        fence: '```',
        emDelimiter: '_',
        strongDelimiter: '**',
        linkStyle: 'inlined',
        linkReferenceStyle: 'full',
        br: '  ',
        preformattedCode: false,
        blankReplacement: (content, node) => node.isBlock ? '\n\n' : '',
        keepReplacement: (content, node) => node.isBlock ? '\n\n' + node.outerHTML + '\n\n' : node.outerHTML,
        defaultReplacement: (content, node) => node.isBlock ? '\n\n' + content + '\n\n' : content
      }, options);
      this.rules = new Rules(this.options);
    }

    /**
     * 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(input) {
      if (!canConvert(input)) {
        throw new TypeError(
          input + ' is not a string, or an element/document/fragment node.'
        )
      }

      if (input === '') return ''

      var output = this.process(RootNode(input, this.options));
      return this.postProcess(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(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(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(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(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(string) {
      return escapes.reduce((accumulator, escape) => accumulator.replace(escape[0], escape[1]), 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
     */

    process(parentNode) {
      var self = this;
      return reduce.call(parentNode.childNodes, (output, node) => {
        node = 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 = self.replacementForNode(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
     */

    postProcess(output) {
      var self = this;
      this.rules.forEach((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
     */

    replacementForNode(node) {
      var rule = this.rules.forNode(node);
      var content = this.process(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
   */

  const 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
   */

  canConvert = (input) =>
    (
      input != null && (
        typeof input === 'string' ||
        (input.nodeType && (
          input.nodeType === 1 || input.nodeType === 9 || input.nodeType === 11
        ))
      )
    )
  ;

  return TurndownService;

})();