discourse/vendor/assets/javascripts/better_markdown.js

/*
  This is a fork of markdown-js with a few changes to support discourse:

  * We have replaced the strong/em handlers because we prefer them only to work on word
    boundaries.

  * [MOD]: non-url is fixed

  // Fix code within attrs
  if (prev && (typeof prev[0] === "string") && prev[0].match(/<[^>]+$/)) { return; }

  // __RAW

  // if ( next_block.match(is_list_re) || (next_block.match(/^ /) && (!next_block.match(/^ *\>/))) ) {

*/

// Released under MIT license
// Copyright (c) 2009-2010 Dominic Baggott
// Copyright (c) 2009-2010 Ash Berlin
// Copyright (c) 2011 Christoph Dorn <christoph@christophdorn.com> (http://www.christophdorn.com)

/*jshint browser:true, devel:true */

(function(expose) {

  var MarkdownHelpers = {};

  // For Spidermonkey based engines
  function mk_block_toSource() {
    return "Markdown.mk_block( " +
            uneval(this.toString()) +
            ", " +
            uneval(this.trailing) +
            ", " +
            uneval(this.lineNumber) +
            " )";
  }

  // node
  function mk_block_inspect() {
    var util = require("util");
    return "Markdown.mk_block( " +
            util.inspect(this.toString()) +
            ", " +
            util.inspect(this.trailing) +
            ", " +
            util.inspect(this.lineNumber) +
            " )";

  }

  MarkdownHelpers.mk_block = function(block, trail, line) {
    // Be helpful for default case in tests.
    if ( arguments.length === 1 )
      trail = "\n\n";

    // We actually need a String object, not a string primitive
    /* jshint -W053 */
    var s = new String(block);
    s.trailing = trail;
    // To make it clear its not just a string
    s.inspect = mk_block_inspect;
    s.toSource = mk_block_toSource;

    if ( line !== undefined )
      s.lineNumber = line;

    return s;
  };

  var isArray = MarkdownHelpers.isArray = Array.isArray || function(obj) {
    return Object.prototype.toString.call(obj) === "[object Array]";
  };

  // Don't mess with Array.prototype. Its not friendly
  if ( Array.prototype.forEach ) {
    MarkdownHelpers.forEach = function forEach( arr, cb, thisp ) {
      return arr.forEach( cb, thisp );
    };
  }
  else {
    MarkdownHelpers.forEach = function forEach(arr, cb, thisp) {
      for (var i = 0; i < arr.length; i++)
        cb.call(thisp || arr, arr[i], i, arr);
    };
  }

  MarkdownHelpers.isEmpty = function isEmpty( obj ) {
    for ( var key in obj ) {
      if ( hasOwnProperty.call( obj, key ) )
        return false;
    }
    return true;
  };

  MarkdownHelpers.extract_attr = function extract_attr( jsonml ) {
    return isArray(jsonml)
        && jsonml.length > 1
        && typeof jsonml[ 1 ] === "object"
        && !( isArray(jsonml[ 1 ]) )
        ? jsonml[ 1 ]
        : undefined;
  };

 /**
   *  class Markdown
   *
   *  Markdown processing in Javascript done right. We have very particular views
   *  on what constitutes 'right' which include:
   *
   *  - produces well-formed HTML (this means that em and strong nesting is
   *    important)
   *
   *  - has an intermediate representation to allow processing of parsed data (We
   *    in fact have two, both as [JsonML]: a markdown tree and an HTML tree).
   *
   *  - is easily extensible to add new dialects without having to rewrite the
   *    entire parsing mechanics
   *
   *  - has a good test suite
   *
   *  This implementation fulfills all of these (except that the test suite could
   *  do with expanding to automatically run all the fixtures from other Markdown
   *  implementations.)
   *
   *  ##### Intermediate Representation
   *
   *  *TODO* Talk about this :) Its JsonML, but document the node names we use.
   *
   *  [JsonML]: http://jsonml.org/ "JSON Markup Language"
   **/
  var Markdown = function(dialect) {
    switch (typeof dialect) {
    case "undefined":
      this.dialect = Markdown.dialects.Gruber;
      break;
    case "object":
      this.dialect = dialect;
      break;
    default:
      if ( dialect in Markdown.dialects )
        this.dialect = Markdown.dialects[dialect];
      else
        throw new Error("Unknown Markdown dialect '" + String(dialect) + "'");
      break;
    }
    this.em_state = [];
    this.strong_state = [];
    this.debug_indent = "";
  };

  /**
   * Markdown.dialects
   *
   * Namespace of built-in dialects.
   **/
  Markdown.dialects = {};

  // Imported functions
  var mk_block = Markdown.mk_block = MarkdownHelpers.mk_block,
      isArray = MarkdownHelpers.isArray;

  /**
   *  parse( markdown, [dialect] ) -> JsonML
   *  - markdown (String): markdown string to parse
   *  - dialect (String | Dialect): the dialect to use, defaults to gruber
   *
   *  Parse `markdown` and return a markdown document as a Markdown.JsonML tree.
   **/
  Markdown.parse = function( source, dialect ) {
    // dialect will default if undefined
    var md = new Markdown( dialect );
    return md.toTree( source );
  };

  /**
   *  count_lines( str ) -> count
   *  - str (String): String whose lines we want to count
   *
   *  Counts the number of linebreaks in `str`
   **/
  function count_lines( str ) {
    return str.split("\n").length - 1;
  }

  // Internal - split source into rough blocks
  Markdown.prototype.split_blocks = function splitBlocks( input ) {
    input = input.replace(/(\r\n|\n|\r)/g, "\n");
    // [\s\S] matches _anything_ (newline or space)
    // [^] is equivalent but doesn't work in IEs.
    var re = /([\s\S]+?)($|\n#|\n(?:\s*\n|$)+)/g,
        blocks = [],
        m;

    var line_no = 1;

    if ( ( m = /^(\s*\n)/.exec(input) ) !== null ) {
      // skip (but count) leading blank lines
      line_no += count_lines( m[0] );
      re.lastIndex = m[0].length;
    }

    while ( ( m = re.exec(input) ) !== null ) {
      if (m[2] === "\n#") {
        m[2] = "\n";
        re.lastIndex--;
      }
      blocks.push( mk_block( m[1], m[2], line_no ) );
      line_no += count_lines( m[0] );
    }

    return blocks;
  };

  /**
   *  Markdown#processBlock( block, next ) -> undefined | [ JsonML, ... ]
   *  - block (String): the block to process
   *  - next (Array): the following blocks
   *
   * Process `block` and return an array of JsonML nodes representing `block`.
   *
   * It does this by asking each block level function in the dialect to process
   * the block until one can. Succesful handling is indicated by returning an
   * array (with zero or more JsonML nodes), failure by a false value.
   *
   * Blocks handlers are responsible for calling [[Markdown#processInline]]
   * themselves as appropriate.
   *
   * If the blocks were split incorrectly or adjacent blocks need collapsing you
   * can adjust `next` in place using shift/splice etc.
   *
   * If any of this default behaviour is not right for the dialect, you can
   * define a `__call__` method on the dialect that will get invoked to handle
   * the block processing.
   */
  Markdown.prototype.processBlock = function processBlock( block, next ) {
    var cbs = this.dialect.block,
        ord = cbs.__order__;

    if ( "__call__" in cbs )
      return cbs.__call__.call(this, block, next);

    for ( var i = 0; i < ord.length; i++ ) {
      //D:this.debug( "Testing", ord[i] );
      var res = cbs[ ord[i] ].call( this, block, next );
      if ( res ) {
        //D:this.debug("  matched");
        if ( !isArray(res) || ( res.length > 0 && !( isArray(res[0]) ) && ( typeof res[0] !== "string")) )
          this.debug(ord[i], "didn't return a proper array");
        //D:this.debug( "" );
        return res;
      }
    }

    // Uhoh! no match! Should we throw an error?
    return [];
  };

  Markdown.prototype.processInline = function processInline( block ) {
    return this.dialect.inline.__call__.call( this, String( block ) );
  };

  /**
   *  Markdown#toTree( source ) -> JsonML
   *  - source (String): markdown source to parse
   *
   *  Parse `source` into a JsonML tree representing the markdown document.
   **/
  // custom_tree means set this.tree to `custom_tree` and restore old value on return
  Markdown.prototype.toTree = function toTree( source, custom_root ) {
    var blocks = source instanceof Array ? source : this.split_blocks( source );

    // Make tree a member variable so its easier to mess with in extensions
    var old_tree = this.tree;
    try {
      this.tree = custom_root || this.tree || [ "markdown" ];

      blocks_loop:
      while ( blocks.length ) {
        var b = this.processBlock( blocks.shift(), blocks );

        // Reference blocks and the like won't return any content
        if ( !b.length )
          continue blocks_loop;

        this.tree.push.apply( this.tree, b );
      }
      return this.tree;
    }
    finally {
      if ( custom_root )
        this.tree = old_tree;
    }
  };

  // Noop by default
  Markdown.prototype.debug = function () {
    var args = Array.prototype.slice.call( arguments);
    args.unshift(this.debug_indent);
    if ( typeof print !== "undefined" )
      print.apply( print, args );
    if ( typeof console !== "undefined" && typeof console.log !== "undefined" )
      console.log.apply( null, args );
  };

  Markdown.prototype.loop_re_over_block = function( re, block, cb ) {
    // Dont use /g regexps with this
    var m,
        b = block.valueOf();

    while ( b.length && (m = re.exec(b) ) !== null ) {
      b = b.substr( m[0].length );
      cb.call(this, m);
    }
    return b;
  };

  // Build default order from insertion order.
  Markdown.buildBlockOrder = function(d) {
    var ord = [[]];
    for ( var i in d ) {
      if ( i === "__order__" || i === "__call__" )
        continue;

      var priority = d[i].priority || 0;
      ord[priority] = ord[priority] || [];
      ord[priority].push( i );
    }

    var flattend = [];
    for (i=ord.length-1; i>=0; i--){
      if (ord[i]) {
        for (var j=0; j<ord[i].length; j++){
          flattend.push(ord[i][j]);
        }
      }
    }

    d.__order__ = flattend;
  };

  // Build patterns for inline matcher
  Markdown.buildInlinePatterns = function(d) {
    var patterns = [];

    for ( var i in d ) {
      // __foo__ is reserved and not a pattern
      if ( i.match( /^__.*__$/) )
        continue;
      var l = i.replace( /([\\.*+?^$|()\[\]{}])/g, "\\$1" )
               .replace( /\n/, "\\n" );
      patterns.push( i.length === 1 ? l : "(?:" + l + ")" );
    }

    patterns = patterns.join("|");
    d.__patterns__ = patterns;
    //print("patterns:", uneval( patterns ) );

    var fn = d.__call__;
    d.__call__ = function(text, pattern) {
      if ( pattern !== undefined )
        return fn.call(this, text, pattern);
      else
        return fn.call(this, text, patterns);
    };
  };

  var extract_attr = MarkdownHelpers.extract_attr;

  /**
   *  renderJsonML( jsonml[, options] ) -> String
   *  - jsonml (Array): JsonML array to render to XML
   *  - options (Object): options
   *
   *  Converts the given JsonML into well-formed XML.
   *
   *  The options currently understood are:
   *
   *  - root (Boolean): wether or not the root node should be included in the
   *    output, or just its children. The default `false` is to not include the
   *    root itself.
   */
  Markdown.renderJsonML = function( jsonml, options ) {
    options = options || {};
    // include the root element in the rendered output?
    options.root = options.root || false;

    var content = [];

    if ( options.root ) {
      content.push( render_tree( jsonml ) );
    }
    else {
      jsonml.shift(); // get rid of the tag
      if ( jsonml.length && typeof jsonml[ 0 ] === "object" && !( jsonml[ 0 ] instanceof Array ) )
        jsonml.shift(); // get rid of the attributes

      while ( jsonml.length )
        content.push( render_tree( jsonml.shift() ) );
    }

    return content.join( "\n\n" );
  };

  /**
   *  toHTMLTree( markdown, [dialect] ) -> JsonML
   *  toHTMLTree( md_tree ) -> JsonML
   *  - markdown (String): markdown string to parse
   *  - dialect (String | Dialect): the dialect to use, defaults to gruber
   *  - md_tree (Markdown.JsonML): parsed markdown tree
   *
   *  Turn markdown into HTML, represented as a JsonML tree. If a string is given
   *  to this function, it is first parsed into a markdown tree by calling
   *  [[parse]].
   **/
  Markdown.toHTMLTree = function toHTMLTree( input, dialect , options ) {

    // convert string input to an MD tree
    if ( typeof input === "string" )
      input = this.parse( input, dialect );

    // Now convert the MD tree to an HTML tree

    // remove references from the tree
    var attrs = extract_attr( input ),
        refs = {};

    if ( attrs && attrs.references )
      refs = attrs.references;

    var html = convert_tree_to_html( input, refs , options );
    merge_text_nodes( html );
    return html;
  };

  /**
   *  toHTML( markdown, [dialect]  ) -> String
   *  toHTML( md_tree ) -> String
   *  - markdown (String): markdown string to parse
   *  - md_tree (Markdown.JsonML): parsed markdown tree
   *
   *  Take markdown (either as a string or as a JsonML tree) and run it through
   *  [[toHTMLTree]] then turn it into a well-formated HTML fragment.
   **/
  Markdown.toHTML = function toHTML( source , dialect , options ) {
    var input = this.toHTMLTree( source , dialect , options );

    return this.renderJsonML( input );
  };

  function escapeHTML( text ) {
    if (text && text.length > 0) {
      return text.replace( /&/g, "&amp;" )
                 .replace( /</g, "&lt;" )
                 .replace( />/g, "&gt;" )
                 .replace( /"/g, "&quot;" )
                 .replace( /'/g, "&#39;" );
    } else {
      return "";
    }
  }

  function render_tree( jsonml ) {
    // basic case
    if ( typeof jsonml === "string" )
      return jsonml;

    if ( jsonml[0] === "__RAW" ) {
      return jsonml[1];
    }

    var tag = jsonml.shift(),
        attributes = {},
        content = [];

    if ( jsonml.length && typeof jsonml[ 0 ] === "object" && !( jsonml[ 0 ] instanceof Array ) )
      attributes = jsonml.shift();

    while ( jsonml.length )
      content.push( render_tree( jsonml.shift() ) );

    var tag_attrs = "";
    if (typeof attributes.src !== 'undefined') {
      tag_attrs += ' src="' + escapeHTML( attributes.src ) + '"';
      delete attributes.src;
    }

    for ( var a in attributes ) {
      var escaped = escapeHTML( attributes[ a ]);
      if (escaped && escaped.length) {
        tag_attrs += " " + a + '="' + escaped + '"';
      }
    }

    // be careful about adding whitespace here for inline elements
    if ( tag === "img" || tag === "br" || tag === "hr" )
      return "<"+ tag + tag_attrs + "/>";
    else
      return "<"+ tag + tag_attrs + ">" + content.join( "" ) + "</" + tag + ">";
  }

  function convert_tree_to_html( tree, references, options ) {
    var i;
    options = options || {};

    // shallow clone
    var jsonml = tree.slice( 0 );

    if ( typeof options.preprocessTreeNode === "function" )
      jsonml = options.preprocessTreeNode(jsonml, references);

    // Clone attributes if they exist
    var attrs = extract_attr( jsonml );
    if ( attrs ) {
      jsonml[ 1 ] = {};
      for ( i in attrs ) {
        jsonml[ 1 ][ i ] = attrs[ i ];
      }
      attrs = jsonml[ 1 ];
    }

    // basic case
    if ( typeof jsonml === "string" )
      return jsonml;

    // convert this node
    switch ( jsonml[ 0 ] ) {
    case "header":
      jsonml[ 0 ] = "h" + jsonml[ 1 ].level;
      delete jsonml[ 1 ].level;
      break;
    case "bulletlist":
      jsonml[ 0 ] = "ul";
      break;
    case "numberlist":
      jsonml[ 0 ] = "ol";
      break;
    case "listitem":
      jsonml[ 0 ] = "li";
      break;
    case "para":
      jsonml[ 0 ] = "p";
      break;
    case "markdown":
      jsonml[ 0 ] = "html";
      if ( attrs )
        delete attrs.references;
      break;
    case "code_block":
      jsonml[ 0 ] = "pre";
      i = attrs ? 2 : 1;
      var code = [ "code" ];
      code.push.apply( code, jsonml.splice( i, jsonml.length - i ) );
      jsonml[ i ] = code;
      break;
    case "inlinecode":
      jsonml[ 0 ] = "code";
      break;
    case "img":
      jsonml[ 1 ].src = jsonml[ 1 ].href;
      delete jsonml[ 1 ].href;
      break;
    case "linebreak":
      jsonml[ 0 ] = "br";
      break;
    case "link":
      jsonml[ 0 ] = "a";
      break;
    case "link_ref":
      jsonml[ 0 ] = "a";

      // grab this ref and clean up the attribute node
      var ref = references[ attrs.ref ];

      // if the reference exists, make the link
      if ( ref ) {
        delete attrs.ref;

        // add in the href and title, if present
        attrs.href = ref.href;
        if ( ref.title )
          attrs.title = ref.title;

        // get rid of the unneeded original text
        delete attrs.original;
      }
      // the reference doesn't exist, so revert to plain text
      else {
        return attrs.original;
      }
      break;
    case "img_ref":
      jsonml[ 0 ] = "img";

      // grab this ref and clean up the attribute node
      var ref = references[ attrs.ref ];

      // if the reference exists, make the link
      if ( ref ) {
        delete attrs.ref;

        // add in the href and title, if present
        attrs.src = ref.href;
        if ( ref.title )
          attrs.title = ref.title;

        // get rid of the unneeded original text
        delete attrs.original;
      }
      // the reference doesn't exist, so revert to plain text
      else {
        return attrs.original;
      }
      break;
    }

    // convert all the children
    i = 1;

    // deal with the attribute node, if it exists
    if ( attrs ) {
      // if there are keys, skip over it
      for ( var key in jsonml[ 1 ] ) {
        i = 2;
        break;
      }
      // if there aren't, remove it
      if ( i === 1 )
        jsonml.splice( i, 1 );
    }

    for ( ; i < jsonml.length; ++i ) {
      jsonml[ i ] = convert_tree_to_html( jsonml[ i ], references, options );
    }

    return jsonml;
  }

  // merges adjacent text nodes into a single node
  function merge_text_nodes( jsonml ) {
    // skip the tag name and attribute hash
    var i = extract_attr( jsonml ) ? 2 : 1;

    while ( i < jsonml.length ) {
      // if it's a string check the next item too
      if ( typeof jsonml[ i ] === "string" ) {
        if ( i + 1 < jsonml.length && typeof jsonml[ i + 1 ] === "string" ) {
          // merge the second string into the first and remove it
          jsonml[ i ] += jsonml.splice( i + 1, 1 )[ 0 ];
        }
        else {
          ++i;
        }
      }
      // if it's not a string recurse
      else {
        merge_text_nodes( jsonml[ i ] );
        ++i;
      }
    }
  }

  var DialectHelpers = {};
  DialectHelpers.inline_until_char = function( text, want ) {
    var consumed = 0,
        nodes = [],
        patterns = this.dialect.inline.__patterns__.replace('|_|', '|');

    while ( true ) {
      if ( text.charAt( consumed ) === want ) {
        // Found the character we were looking for
        consumed++;
        return [ consumed, nodes ];
      }

      if ( consumed >= text.length ) {
        // No closing char found. Abort.
        return [consumed, null, nodes];
      }

      var res = this.dialect.inline.__oneElement__.call(this, text.substr( consumed ), patterns, [text.substr(0, consumed)]);
      consumed += res[ 0 ];
      // Add any returned nodes.
      nodes.push.apply( nodes, res.slice( 1 ) );
    }
  };

  // Helper function to make sub-classing a dialect easier
  DialectHelpers.subclassDialect = function( d ) {
    function Block() {}
    Block.prototype = d.block;
    function Inline() {}
    Inline.prototype = d.inline;

    return { block: new Block(), inline: new Inline() };
  };

  var forEach = MarkdownHelpers.forEach,
      extract_attr = MarkdownHelpers.extract_attr,
      mk_block = MarkdownHelpers.mk_block,
      isEmpty = MarkdownHelpers.isEmpty,
      inline_until_char = DialectHelpers.inline_until_char;

  // A robust regexp for matching URLs. Thakns: https://gist.github.com/dperini/729294
  var urlRegexp = /(?:(?:https?|ftp):\/\/)(?:\S+(?::\S*)?@)?(?:(?!(?:10|127)(?:\.\d{1,3}){3})(?!(?:169\.254|192\.168)(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]-*)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]+-?)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})))(?::\d{2,5})?(?:\/[^\s]*)?/i.source;

  /**
   * Gruber dialect
   *
   * The default dialect that follows the rules set out by John Gruber's
   * markdown.pl as closely as possible. Well actually we follow the behaviour of
   * that script which in some places is not exactly what the syntax web page
   * says.
   **/
  var Gruber = {
    block: {
      atxHeader: function atxHeader( block, next ) {
        var m = block.match( /^(#{1,6})\s*(.*?)\s*#*\s*(?:\n|$)/ );

        if ( !m )
          return undefined;

        var header = [ "header", { level: m[ 1 ].length } ];
        Array.prototype.push.apply(header, this.processInline(m[ 2 ]));

        if ( m[0].length < block.length )
          next.unshift( mk_block( block.substr( m[0].length ), block.trailing, block.lineNumber + 2 ) );

        return [ header ];
      },

      setextHeader: function setextHeader( block, next ) {
        var m = block.match( /^(.*)\n([-=])\2\2+(?:\n|$)/ );

        if ( !m )
          return undefined;

        var level = ( m[ 2 ] === "=" ) ? 1 : 2,
            header = [ "header", { level : level } ].concat( this.processInline(m[ 1 ]) );

        if ( m[0].length < block.length )
          next.unshift( mk_block( block.substr( m[0].length ), block.trailing, block.lineNumber + 2 ) );

        return [ header ];
      },

      code: function code( block, next ) {
        // |    Foo
        // |bar
        // should be a code block followed by a paragraph. Fun
        //
        // There might also be adjacent code block to merge.

        var ret = [],
            re = /^(?: {0,3}\t| {4})(.*)\n?/;

        // 4 spaces + content
        if ( !block.match( re ) )
          return undefined;

        block_search:
        do {
          // Now pull out the rest of the lines
          var b = this.loop_re_over_block(
                    re, block.valueOf(), function( m ) { ret.push( m[1] ); } );

          if ( b.length ) {
            // Case alluded to in first comment. push it back on as a new block
            next.unshift( mk_block(b, block.trailing) );
            break block_search;
          }
          else if ( next.length ) {
            // Check the next block - it might be code too
            if ( !next[0].match( re ) )
              break block_search;

            // Pull how how many blanks lines follow - minus two to account for .join
            ret.push ( block.trailing.replace(/[^\n]/g, "").substring(2) );

            block = next.shift();
          }
          else {
            break block_search;
          }
        } while ( true );

        return [ [ "code_block", ret.join("\n") ] ];
      },

      horizRule: function horizRule( block, next ) {
        // this needs to find any hr in the block to handle abutting blocks
        var m = block.match( /^(?:([\s\S]*?)\n)?[ \t]*([-_*])(?:[ \t]*\2){2,}[ \t]*(?:\n([\s\S]*))?$/ );

        if ( !m )
          return undefined;

        var jsonml = [ [ "hr" ] ];

        // if there's a leading abutting block, process it
        if ( m[ 1 ] ) {
          var contained = mk_block( m[ 1 ], "", block.lineNumber );
          jsonml.unshift.apply( jsonml, this.toTree( contained, [] ) );
        }

        // if there's a trailing abutting block, stick it into next
        if ( m[ 3 ] )
          next.unshift( mk_block( m[ 3 ], block.trailing, block.lineNumber + 1 ) );

        return jsonml;
      },

      // There are two types of lists. Tight and loose. Tight lists have no whitespace
      // between the items (and result in text just in the <li>) and loose lists,
      // which have an empty line between list items, resulting in (one or more)
      // paragraphs inside the <li>.
      //
      // There are all sorts weird edge cases about the original markdown.pl's
      // handling of lists:
      //
      // * Nested lists are supposed to be indented by four chars per level. But
      //   if they aren't, you can get a nested list by indenting by less than
      //   four so long as the indent doesn't match an indent of an existing list
      //   item in the 'nest stack'.
      //
      // * The type of the list (bullet or number) is controlled just by the
      //    first item at the indent. Subsequent changes are ignored unless they
      //    are for nested lists
      //
      lists: (function( ) {
        // Use a closure to hide a few variables.
        var any_list = "[*+-]|\\d+\\.",
            bullet_list = /[*+-]/,
            // Capture leading indent as it matters for determining nested lists.
            is_list_re = new RegExp( "^( {0,3})(" + any_list + ")[ \t]+" ),
            indent_re = "(?: {0,3}\\t| {4})";

        // TODO: Cache this regexp for certain depths.
        // Create a regexp suitable for matching an li for a given stack depth
        function regex_for_depth( depth ) {
          return new RegExp(
            // m[1] = indent, m[2] = list_type
            "(?:^(" + indent_re + "{0," + depth + "} {0,3})(" + any_list + ")\\s+)|" +
            // m[3] = cont
            "(^" + indent_re + "{0," + (depth-1) + "}[ ]{0,4})"
          );
        }
        function expand_tab( input ) {
          return input.replace( / {0,3}\t/g, "    " );
        }

        // Add inline content `inline` to `li`. inline comes from processInline
        // so is an array of content
        function add(li, loose, inline, nl) {
          if ( loose ) {
            li.push( [ "para" ].concat(inline) );
            return;
          }
          // Hmmm, should this be any block level element or just paras?
          var add_to = li[li.length -1] instanceof Array && li[li.length - 1][0] === "para"
                     ? li[li.length -1]
                     : li;

          // If there is already some content in this list, add the new line in
          if ( nl && li.length > 1 )
            inline.unshift(nl);

          for ( var i = 0; i < inline.length; i++ ) {
            var what = inline[i],
                is_str = typeof what === "string";
            if ( is_str && add_to.length > 1 && typeof add_to[add_to.length-1] === "string" )
              add_to[ add_to.length-1 ] += what;
            else
              add_to.push( what );
          }
        }

        // contained means have an indent greater than the current one. On
        // *every* line in the block
        function get_contained_blocks( depth, blocks ) {

          var re = new RegExp( "^(" + indent_re + "{" + depth + "}.*?\\n?)*$" ),
              replace = new RegExp("^" + indent_re + "{" + depth + "}", "gm"),
              ret = [];


          while ( blocks.length > 0 ) {
            // HACK: Fixes a v8 issue
            test = blocks[0].replace(/^ {8,}/, '        ');
            if ( re.exec( test ) ) {
              var b = blocks.shift(),
                  // Now remove that indent
                  x = b.replace( replace, "");

              ret.push( mk_block( x, b.trailing, b.lineNumber ) );
            }
            else
              break;
          }
          return ret;
        }

        // passed to stack.forEach to turn list items up the stack into paras
        function paragraphify(s, i, stack) {
          var list = s.list;
          var last_li = list[list.length-1];

          if ( last_li[1] instanceof Array && last_li[1][0] === "para" )
            return;

          if ( i + 1 === stack.length ) {
            // Last stack frame
            // Keep the same array, but replace the contents
            last_li.push( ["para"].concat( last_li.splice(1, last_li.length - 1) ) );
          }
          else {
            var sublist = last_li.pop();
            last_li.push( ["para"].concat( last_li.splice(1, last_li.length - 1) ), sublist );
          }
        }

        // The matcher function
        return function( block, next ) {
          var m = block.match( is_list_re );
          if ( !m )
            return undefined;

          function make_list( m ) {
            var list = bullet_list.exec( m[2] )
                     ? ["bulletlist"]
                     : ["numberlist"];

            stack.push( { list: list, indent: m[1] } );
            return list;
          }

          var stack = [], // Stack of lists for nesting.
              list = make_list( m ),
              last_li,
              loose = false,
              ret = [ stack[0].list ],
              i;

          // Loop to search over block looking for inner block elements and loose lists
          loose_search:
          while ( true ) {
            // Split into lines preserving new lines at end of line
            var lines = block.split( /(?=\n)/ );

            // We have to grab all lines for a li and call processInline on them
            // once as there are some inline things that can span lines.
            var li_accumulate = "", nl = "";

            // Loop over the lines in this block looking for tight lists.
            tight_search:
            for ( var line_no = 0; line_no < lines.length; line_no++ ) {
              nl = "";
              var l = lines[line_no].replace(/^\n/, function(n) { nl = n; return ""; });

              // TODO: really should cache this
              var line_re = regex_for_depth( stack.length );

              m = l.match( line_re );
              //print( "line:", uneval(l), "\nline match:", uneval(m) );

              // We have a list item
              if ( m[1] !== undefined ) {
                // Process the previous list item, if any
                if ( li_accumulate.length ) {
                  add( last_li, loose, this.processInline( li_accumulate ), nl );
                  // Loose mode will have been dealt with. Reset it
                  loose = false;
                  li_accumulate = "";
                }

                m[1] = expand_tab( m[1] );
                var wanted_depth = Math.floor(m[1].length/4)+1;
                //print( "want:", wanted_depth, "stack:", stack.length);
                if ( wanted_depth > stack.length ) {
                  // Deep enough for a nested list outright
                  //print ( "new nested list" );
                  list = make_list( m );
                  last_li.push( list );
                  last_li = list[1] = [ "listitem" ];
                }
                else {
                  // We aren't deep enough to be strictly a new level. This is
                  // where Md.pl goes nuts. If the indent matches a level in the
                  // stack, put it there, else put it one deeper then the
                  // wanted_depth deserves.
                  var found = false;
                  for ( i = 0; i < stack.length; i++ ) {
                    if ( stack[ i ].indent !== m[1] )
                      continue;

                    list = stack[ i ].list;
                    stack.splice( i+1, stack.length - (i+1) );
                    found = true;
                    break;
                  }

                  if (!found) {
                    //print("not found. l:", uneval(l));
                    wanted_depth++;
                    if ( wanted_depth <= stack.length ) {
                      stack.splice(wanted_depth, stack.length - wanted_depth);
                      //print("Desired depth now", wanted_depth, "stack:", stack.length);
                      list = stack[wanted_depth-1].list;
                      //print("list:", uneval(list) );
                    }
                    else {
                      //print ("made new stack for messy indent");
                      list = make_list(m);
                      last_li.push(list);
                    }
                  }

                  //print( uneval(list), "last", list === stack[stack.length-1].list );
                  last_li = [ "listitem" ];
                  list.push(last_li);
                } // end depth of shenegains
                nl = "";
              }

              // Add content
              if ( l.length > m[0].length )
                li_accumulate += nl + l.substr( m[0].length );
            } // tight_search

            if ( li_accumulate.length ) {

              var contents = this.processBlock(li_accumulate, []),
                  firstBlock = contents[0];

              if (firstBlock) {
                firstBlock.shift();
                contents.splice.apply(contents, [0, 1].concat(firstBlock));
                add( last_li, loose, contents, nl );

                // Let's not creating a trailing \n after content in the li
                if(last_li[last_li.length-1] === "\n") {
                  last_li.pop();
                }

                // Loose mode will have been dealt with. Reset it
                loose = false;
                li_accumulate = "";
              }
            }

            // Look at the next block - we might have a loose list. Or an extra
            // paragraph for the current li
            var contained = get_contained_blocks( stack.length, next );

            // Deal with code blocks or properly nested lists
            if ( contained.length > 0 ) {
              // Make sure all listitems up the stack are paragraphs
              forEach( stack, paragraphify, this);

              last_li.push.apply( last_li, this.toTree( contained, [] ) );
            }

            var next_block = next[0] && next[0].valueOf() || "";

            if ( next_block.match(is_list_re) )  {
              block = next.shift();

              // Check for an HR following a list: features/lists/hr_abutting
              var hr = this.dialect.block.horizRule.call( this, block, next );

              if ( hr ) {
                ret.push.apply(ret, hr);
                break;
              }

              // Add paragraphs if the indentation level stays the same
              if (stack[stack.length-1].indent === block.match(/^\s*/)[0]) {
                forEach( stack, paragraphify, this);
              }

              loose = true;
              continue loose_search;
            }
            break;
          } // loose_search

          return ret;
        };
      })(),

      blockquote: function blockquote( block, next ) {

        // Handle quotes that have spaces before them
        var m = /(^|\n) +(\>[\s\S]*)/.exec(block);
        if (m && m[2] && m[2].length) {
          var blockContents = block.replace(/(^|\n) +\>/, "$1>");
          next.unshift(blockContents);
          return [];
        }

        if ( !block.match( /^>/m ) )
          return undefined;

        var jsonml = [];

        // separate out the leading abutting block, if any. I.e. in this case:
        //
        //  a
        //  > b
        //
        if ( block[ 0 ] !== ">" ) {
          var lines = block.split( /\n/ ),
              prev = [],
              line_no = block.lineNumber;

          // keep shifting lines until you find a crotchet
          while ( lines.length && lines[ 0 ][ 0 ] !== ">" ) {
            prev.push( lines.shift() );
            line_no++;
          }

          var abutting = mk_block( prev.join( "\n" ), "\n", block.lineNumber );
          jsonml.push.apply( jsonml, this.processBlock( abutting, [] ) );
          // reassemble new block of just block quotes!
          block = mk_block( lines.join( "\n" ), block.trailing, line_no );
        }

        // if the next block is also a blockquote merge it in
        while ( next.length && next[ 0 ][ 0 ] === ">" ) {
          var b = next.shift();
          block = mk_block( block + block.trailing + b, b.trailing, block.lineNumber );
        }

        // Strip off the leading "> " and re-process as a block.
        var input = block.replace( /^> ?/gm, "" ),
            old_tree = this.tree,
            processedBlock = this.toTree( input, [ "blockquote" ] ),
            attr = extract_attr( processedBlock );

        // If any link references were found get rid of them
        if ( attr && attr.references ) {
          delete attr.references;
          // And then remove the attribute object if it's empty
          if ( isEmpty( attr ) )
            processedBlock.splice( 1, 1 );
        }

        jsonml.push( processedBlock );
        return jsonml;
      },

      referenceDefn: function referenceDefn( block, next) {
        var re = /^\s*\[([^\[\]]+)\]:\s*(\S+)(?:\s+(?:(['"])(.*)\3|\((.*?)\)))?\n?/;
        // interesting matches are [ , ref_id, url, , title, title ]

        if ( !block.match(re) )
          return undefined;

        var attrs = create_attrs.call( this );

        var b = this.loop_re_over_block(re, block, function( m ) {
          create_reference(attrs, m);
        } );

        if ( b.length )
          next.unshift( mk_block( b, block.trailing ) );

        return [];
      },

      para: function para( block ) {
        // everything's a para!
        return [ ["para"].concat( this.processInline( block ) ) ];
      }
    },

    inline: {

      __oneElement__: function oneElement( text, patterns_or_re, previous_nodes ) {

        // PERF NOTE: rewritten to avoid greedy match regex \([\s\S]*?)(...)\
        // greedy match performs horribly with large inline blocks, it can be so
        // slow it will crash chrome
        patterns_or_re = patterns_or_re || this.dialect.inline.__patterns__;

        var search_re = new RegExp(patterns_or_re.source || patterns_or_re);
        var pos = text.search(search_re);

        if (pos === -1) {
          return [ text.length, text ];
        } else if (pos !== 0) {
          // Some un-interesting text matched. Return that first
          return [pos, text.substring(0,pos)];
        }

        var match_re = new RegExp( "^(" + (patterns_or_re.source || patterns_or_re) + ")" );
        var m = match_re.exec( text );
        var res;
        if ( m[1] in this.dialect.inline ) {
          res = this.dialect.inline[ m[1] ].call(
                    this,
                    text.substr( m.index ), m, previous_nodes || [] );

          // If no inline code executed, fallback
          if (!res) {
            var fn = this.dialect.inline[m[1][0]];
            if (fn) {
              res = fn.call(
                    this,
                    text.substr( m.index ), m, previous_nodes || [] );
            }
          }
        }
        // Default for now to make dev easier. just slurp special and output it.
        res = res || [ m[1].length, m[1] ];
        return res;
      },

      __call__: function inline( text, patterns ) {

        var out = [],
            res;

        function add(x) {
          //D:self.debug("  adding output", uneval(x));
          if ( typeof x === "string" && typeof out[out.length-1] === "string" )
            out[ out.length-1 ] += x;
          else
            out.push(x);
        }

        while ( text.length > 0 ) {
          res = this.dialect.inline.__oneElement__.call(this, text, patterns, out );
          text = text.substr( res.shift() );
          forEach(res, add );
        }

        return out;
      },

      // These characters are interesting elsewhere, so have rules for them so that
      // chunks of plain text blocks don't include them
      "]": function () {},
      "}": function () {},

      __escape__ : /^\\[\\`\*_{}<>\[\]()#\+.!\-]/,

      "\\": function escaped( text ) {
        // [ length of input processed, node/children to add... ]
        // Only esacape: \ ` * _ { } [ ] ( ) # * + - . !
        if ( this.dialect.inline.__escape__.exec( text ) )
          return [ 2, text.charAt( 1 ) ];
        else
          // Not an esacpe
          return [ 1, "\\" ];
      },

      "![": function image( text ) {

        // Without this guard V8 crashes hard on the RegExp
        if (text.indexOf('(') >= 0 && text.indexOf(')') === -1) { return; }

        // Unlike images, alt text is plain text only. no other elements are
        // allowed in there

        // ![Alt text](/path/to/img.jpg "Optional title")
        //      1          2            3       4         <--- captures
        //
        // First attempt to use a strong URL regexp to catch things like parentheses. If it misses, use the
        // old one.
        var origMatcher = /^!\[(.*?)\][ \t]*\([ \t]*([^")]*?)(?:[ \t]+(["'])(.*?)\3)?[ \t]*\)/;
            m = text.match(new RegExp("^!\\[(.*?)][ \\t]*\\((" + urlRegexp + ")\\)([ \\t])*([\"'].*[\"'])?")) ||
                text.match(origMatcher);

        if (m && m[2].indexOf(")]") !== -1) { m = text.match(origMatcher); }

        if ( m ) {
          if ( m[2] && m[2][0] === "<" && m[2][m[2].length-1] === ">" )
            m[2] = m[2].substring( 1, m[2].length - 1 );

          m[2] = this.dialect.inline.__call__.call( this, m[2], /\\/ )[0];

          var attrs = { alt: m[1], href: m[2] || "" };
          if ( m[4] !== undefined)
            attrs.title = m[4];

          return [ m[0].length, [ "img", attrs ] ];
        }

        // ![Alt text][id]
        m = text.match( /^!\[(.*?)\][ \t]*\[(.*?)\]/ );

        if ( m ) {
          // We can't check if the reference is known here as it likely wont be
          // found till after. Check it in md tree->hmtl tree conversion
          return [ m[0].length, [ "img_ref", { alt: m[1], ref: m[2].toLowerCase(), original: m[0] } ] ];
        }

        // Just consume the '!['
        return [ 2, "![" ];
      },

      "[": function link( text ) {

        var open = 1;
        for (var i=0; i<text.length; i++) {
          var c = text.charAt(i);
          if (c === '[') { open++; }
          if (c === ']') { open--; }

          if (open > 3) { return [1, "["]; }
        }

        var orig = String(text);
        // Inline content is possible inside `link text`
        var res = inline_until_char.call( this, text.substr(1), "]" );

        // No closing ']' found. Just consume the [
        if ( !res[1] ) {
          return [ res[0] + 1, text.charAt(0) ].concat(res[2]);
        }

        if ( res[0] == 1 ) { return [ 2, "[]" ]; } // empty link found.

        var consumed = 1 + res[ 0 ],
            children = res[ 1 ],
            link,
            attrs;

        // At this point the first [...] has been parsed. See what follows to find
        // out which kind of link we are (reference or direct url)
        text = text.substr( consumed );

        // [link text](/path/to/img.jpg "Optional title")
        //                 1            2       3         <--- captures
        // This will capture up to the last paren in the block. We then pull
        // back based on if there a matching ones in the url
        //    ([here](/url/(test))
        // The parens have to be balanced
        var m = text.match( /^\s*\([ \t]*([^"'\s]*)(?:[ \t]+(["'])(.*?)\2)?[ \t]*\)/ );
        if ( m ) {
          var url = m[1].replace(/\s+$/, '');
          consumed += m[0].length;

          if ( url && url[0] === "<" && url[url.length-1] === ">" )
            url = url.substring( 1, url.length - 1 );

          // If there is a title we don't have to worry about parens in the url
          if ( !m[3] ) {
            var open_parens = 1; // One open that isn't in the capture
            for ( var len = 0; len < url.length; len++ ) {
              switch ( url[len] ) {
              case "(":
                open_parens++;
                break;
              case ")":
                if ( --open_parens === 0) {
                  consumed -= url.length - len;
                  url = url.substring(0, len);
                }
                break;
              }
            }
          }

          // Process escapes only
          url = this.dialect.inline.__call__.call( this, url, /\\/ )[0];

          attrs = { href: url || "" };
          if ( m[3] !== undefined)
            attrs.title = m[3];

          link = [ "link", attrs ].concat( children );
          return [ consumed, link ];
        }

        if (text.indexOf('(') === 0 && text.indexOf(')') !== -1) {
          m = text.match(new RegExp("^\\((" + urlRegexp + ")\\)"));
          if (m && m[1]) {
            consumed += m[0].length;
            link = ["link", {href: m[1]}].concat(children);
            return [consumed, link];
          }
        }

        // [Alt text][id]
        // [Alt text] [id]
        m = text.match( /^\s*\[(.*?)\]/ );
        if ( m ) {

          consumed += m[ 0 ].length;

          // [links][] uses links as its reference
          attrs = { ref: ( m[ 1 ] || String(children) ).toLowerCase(),  original: orig.substr( 0, consumed ) };

          if (children && children.length > 0) {
            link = [ "link_ref", attrs ].concat( children );

            // We can't check if the reference is known here as it likely wont be
            // found till after. Check it in md tree->hmtl tree conversion.
            // Store the original so that conversion can revert if the ref isn't found.
            return [ consumed, link ];
          }
        }

        // Another check for references
        m = orig.match(/^\s*\[(.*?)\]:\s*(\S+)(?:\s+(?:(['"])(.*?)\3|\((.*?)\)))?\n?/);
        if (m &&
            (/^(?:(?:https?|ftp):\/\/)(?:\S+(?::\S*)?@)?(?:(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\u00a1-\uffff0-9]+-?)*[a-z\u00a1-\uffff0-9]+)(?:\.(?:[a-z\u00a1-\uffff0-9]+-?)*[a-z\u00a1-\uffff0-9]+)*(?:\.(?:[a-z\u00a1-\uffff]{2,})))(?::\d{2,5})?(?:\/[^\s]*)?$/i.test(m[2]) ||
             /(\/[\w~,;\-\./?%&+#=]*)/.test(m[2]))) {
          attrs = create_attrs.call(this);
          create_reference(attrs, m);

          return [ m[0].length ];
        }

        // [id]
        // Only if id is plain (no formatting.)
        if ( children.length === 1 && typeof children[0] === "string" ) {

          var normalized = children[0].toLowerCase().replace(/\s+/, ' ');
          attrs = { ref: normalized,  original: orig.substr( 0, consumed ) };
          link = [ "link_ref", attrs, children[0] ];
          return [ consumed, link ];
        }

        // Just consume the "["
        return [ 1, "[" ];
      },

      "<": function autoLink( text ) {
        var m;

        if ( ( m = text.match( /^<(?:((https?|ftp|mailto):[^>]+)|(.*?@.*?\.[a-zA-Z]+))>/ ) ) !== null ) {
          if ( m[3] )
            return [ m[0].length, [ "link", { href: "mailto:" + m[3] }, m[3] ] ];
          else if ( m[2] === "mailto" )
            return [ m[0].length, [ "link", { href: m[1] }, m[1].substr("mailto:".length ) ] ];
          else
            return [ m[0].length, [ "link", { href: m[1] }, m[1] ] ];
        }

        return [ 1, "<" ];
      },

      "`": function inlineCode( text, match, prev ) {

        // If we're in a tag, don't do it.
        if (prev && (typeof prev[0] === "string") && prev[0].match(/<[^>]+$/)) { return; }

        // Inline code block. as many backticks as you like to start it
        // Always skip over the opening ticks.
        var m = text.match( /(`+)(([\s\S]*?)\1)/ );

        if ( m && m[2] )
          return [ m[1].length + m[2].length, [ "inlinecode", m[3] ] ];
        else {
          // TODO: No matching end code found - warn!
          return [ 1, "`" ];
        }
      },

      "  \n": function lineBreak() {
        return [ 3, [ "linebreak" ] ];
      }

    }
  };

  // A helper function to create attributes
  function create_attrs() {
    if ( !extract_attr( this.tree ) ) {
      this.tree.splice( 1, 0, {} );
    }

    var attrs = extract_attr( this.tree );

    // make a references hash if it doesn't exist
    if ( attrs.references === undefined ) {
      attrs.references = {};
    }

    return attrs;
  }

  // Create references for attributes
  function create_reference(attrs, m) {
    if ( m[2] && m[2][0] === "<" && m[2][m[2].length-1] === ">" )
      m[2] = m[2].substring( 1, m[2].length - 1 );

    var ref = attrs.references[ m[1].toLowerCase() ] = {
      href: m[2]
    };

    if ( m[4] !== undefined )
      ref.title = m[4];
    else if ( m[5] !== undefined )
      ref.title = m[5];
  }

  Markdown.dialects.Gruber = Gruber;
  Markdown.buildBlockOrder ( Markdown.dialects.Gruber.block );
  Markdown.buildInlinePatterns( Markdown.dialects.Gruber.inline );

// Include all our dependencies and return the resulting library.

  expose.Markdown = Markdown;
  expose.parse = Markdown.parse;
  expose.toHTML = Markdown.toHTML;
  expose.toHTMLTree = Markdown.toHTMLTree;
  expose.renderJsonML = Markdown.renderJsonML;
  expose.DialectHelpers = DialectHelpers;

})(function() {
  window.BetterMarkdown = {};
  return window.BetterMarkdown;
}());