text: // 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 ) {
  
      /**
       *  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 = expose.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 = "";
      };
  
      /**
       *  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.
       **/
      expose.parse = function( source, dialect ) {
          // dialect will default if undefined
          var md = new Markdown( dialect );
          return md.toTree( source );
      };
  
      /**
       *  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.
       **/
      expose.toHTML = function toHTML( source , dialect , options ) {
          var input = expose.toHTMLTree( source , dialect , options );
  
          return expose.renderJsonML( input );
      };
  
      /**
       *  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]].
       **/
      expose.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;
      };
  
  // 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) +
              " )";
  
      }
  
      var mk_block = Markdown.mk_block = function(block, trail, line) {
          // Be helpful for default case in tests.
          if ( arguments.length == 1 ) trail = "\n\n";
  
          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;
      };
  
      function count_lines( str ) {
          var n = 0, i = -1;
          while ( ( i = str.indexOf("\n", i + 1) ) !== -1 ) n++;
          return n;
      }
  
  // Internal - split source into rough blocks
      Markdown.prototype.split_blocks = function splitBlocks( input, startLine ) {
          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]) ) ) )
                      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:
                  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;
  
                      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;
      };
  
      /**
       * Markdown.dialects
       *
       * Namespace of built-in dialects.
       **/
      Markdown.dialects = {};
  
      /**
       * Markdown.dialects.Gruber
       *
       * 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.
       **/
      Markdown.dialects.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;
                  var header = [ "header", { level : level }, 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?/,
                      lines;
  
                  // 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 ] ) {
                      jsonml.unshift.apply( jsonml, this.processBlock( m[ 1 ], [] ) );
                  }
  
                  // if there's a trailing abutting block, stick it into next
                  if ( m[ 3 ] ) {
                      next.unshift( mk_block( m[ 3 ] ) );
                  }
  
                  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 = /[*+-]/,
                      number_list = /\d+\./,
                      // 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 ) {
                          if ( re.exec( blocks[0] ) ) {
                              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 = "";
  
                              // Loop over the lines in this block looking for tight lists.
                              tight_search:
                                  for ( var line_no = 0; line_no < lines.length; line_no++ ) {
                                      var nl = "",
                                          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 ) {
                                  add( last_li, loose, this.processInline( li_accumulate ), nl );
                                  // 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) || next_block.match( /^ / ) ) {
                                  block = next.shift();
  
                                  // Check for an HR following a list: features/lists/hr_abutting
                                  var hr = this.dialect.block.horizRule( block, next );
  
                                  if ( hr ) {
                                      ret.push.apply(ret, hr);
                                      break;
                                  }
  
                                  // Make sure all listitems up the stack are paragraphs
                                  forEach( stack, paragraphify, this);
  
                                  loose = true;
                                  continue loose_search;
                              }
                              break;
                          } // loose_search
  
                      return ret;
                  };
              })(),
  
              blockquote: function blockquote( block, next ) {
                  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;
  
                  // make an attribute node if it doesn't exist
                  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 = {};
                  }
  
                  var b = this.loop_re_over_block(re, block, function( 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];
  
                  } );
  
                  if ( b.length )
                      next.unshift( mk_block( b, block.trailing ) );
  
                  return [];
              },
  
              para: function para( block, next ) {
                  // everything's a para!
                  return [ ["para"].concat( this.processInline( block ) ) ];
              }
          }
      };
  
      Markdown.dialects.Gruber.inline = {
  
          __oneElement__: function oneElement( text, patterns_or_re, previous_nodes ) {
              var m,
                  res,
                  lastIndex = 0;
  
              patterns_or_re = patterns_or_re || this.dialect.inline.__patterns__;
              var re = new RegExp( "([\\s\\S]*?)(" + (patterns_or_re.source || patterns_or_re) + ")" );
  
              m = re.exec( text );
              if (!m) {
                  // Just boring text
                  return [ text.length, text ];
              }
              else if ( m[1] ) {
                  // Some un-interesting text matched. Return that first
                  return [ m[1].length, m[1] ];
              }
  
              var res;
              if ( m[2] in this.dialect.inline ) {
                  res = this.dialect.inline[ m[2] ].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[2].length, m[2] ];
              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 intersting 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 ) {
  
              // 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
              var m = text.match( /^!\[(.*?)\][ \t]*\([ \t]*([^")]*?)(?:[ \t]+(["'])(.*?)\3)?[ \t]*\)/ );
  
              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 orig = String(text);
              // Inline content is possible inside `link text`
              var res = Markdown.DialectHelpers.inline_until_char.call( this, text.substr(1), "]" );
  
              // No closing ']' found. Just consume the [
              if ( !res ) return [ 1, "[" ];
  
              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*\([ \t]*([^"']*)(?:[ \t]+(["'])(.*?)\2)?[ \t]*\)/ );
              if ( m ) {
                  var url = m[1];
                  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 ];
              }
  
              // [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 ) };
  
                  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 ];
              }
  
              // [id]
              // Only if id is plain (no formatting.)
              if ( children.length == 1 && typeof children[0] == "string" ) {
  
                  attrs = { ref: children[0].toLowerCase(),  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 ) {
              // 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( text ) {
              return [ 3, [ "linebreak" ] ];
          }
  
      };
  
  // Meta Helper/generator method for em and strong handling
      function strong_em( tag, md ) {
  
          var state_slot = tag + "_state",
              other_slot = tag == "strong" ? "em_state" : "strong_state";
  
          function CloseTag(len) {
              this.len_after = len;
              this.name = "close_" + md;
          }
  
          return function ( text, orig_match ) {
  
              if ( this[state_slot][0] == md ) {
                  // Most recent em is of this type
                  //D:this.debug("closing", md);
                  this[state_slot].shift();
  
                  // "Consume" everything to go back to the recrusion in the else-block below
                  return[ text.length, new CloseTag(text.length-md.length) ];
              }
              else {
                  // Store a clone of the em/strong states
                  var other = this[other_slot].slice(),
                      state = this[state_slot].slice();
  
                  this[state_slot].unshift(md);
  
                  //D:this.debug_indent += "  ";
  
                  // Recurse
                  var res = this.processInline( text.substr( md.length ) );
                  //D:this.debug_indent = this.debug_indent.substr(2);
  
                  var last = res[res.length - 1];
  
                  //D:this.debug("processInline from", tag + ": ", uneval( res ) );
  
                  var check = this[state_slot].shift();
                  if ( last instanceof CloseTag ) {
                      res.pop();
                      // We matched! Huzzah.
                      var consumed = text.length - last.len_after;
                      return [ consumed, [ tag ].concat(res) ];
                  }
                  else {
                      // Restore the state of the other kind. We might have mistakenly closed it.
                      this[other_slot] = other;
                      this[state_slot] = state;
  
                      // We can't reuse the processed result as it could have wrong parsing contexts in it.
                      return [ md.length, md ];
                  }
              }
          }; // End returned function
      }
  
      Markdown.dialects.Gruber.inline["**"] = strong_em("strong", "**");
      Markdown.dialects.Gruber.inline["__"] = strong_em("strong", "__");
      Markdown.dialects.Gruber.inline["*"]  = strong_em("em", "*");
      Markdown.dialects.Gruber.inline["_"]  = strong_em("em", "_");
  
  
  // Build default order from insertion order.
      Markdown.buildBlockOrder = function(d) {
          var ord = [];
          for ( var i in d ) {
              if ( i == "__order__" || i == "__call__" ) continue;
              ord.push( i );
          }
          d.__order__ = ord;
      };
  
  // 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);
              }
          };
      };
  
      Markdown.DialectHelpers = {};
      Markdown.DialectHelpers.inline_until_char = function( text, want ) {
          var consumed = 0,
              nodes = [];
  
          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 null;
              }
  
              var res = this.dialect.inline.__oneElement__.call(this, text.substr( consumed ) );
              consumed += res[ 0 ];
              // Add any returned nodes.
              nodes.push.apply( nodes, res.slice( 1 ) );
          }
      }
  
  // Helper function to make sub-classing a dialect easier
      Markdown.subclassDialect = function( d ) {
          function Block() {}
          Block.prototype = d.block;
          function Inline() {}
          Inline.prototype = d.inline;
  
          return { block: new Block(), inline: new Inline() };
      };
  
      Markdown.buildBlockOrder ( Markdown.dialects.Gruber.block );
      Markdown.buildInlinePatterns( Markdown.dialects.Gruber.inline );
  
      Markdown.dialects.Maruku = Markdown.subclassDialect( Markdown.dialects.Gruber );
  
      Markdown.dialects.Maruku.processMetaHash = function processMetaHash( meta_string ) {
          var meta = split_meta_hash( meta_string ),
              attr = {};
  
          for ( var i = 0; i < meta.length; ++i ) {
              // id: #foo
              if ( /^#/.test( meta[ i ] ) ) {
                  attr.id = meta[ i ].substring( 1 );
              }
              // class: .foo
              else if ( /^\./.test( meta[ i ] ) ) {
                  // if class already exists, append the new one
                  if ( attr["class"] ) {
                      attr["class"] = attr["class"] + meta[ i ].replace( /./, " " );
                  }
                  else {
                      attr["class"] = meta[ i ].substring( 1 );
                  }
              }
              // attribute: foo=bar
              else if ( /\=/.test( meta[ i ] ) ) {
                  var s = meta[ i ].split( /\=/ );
                  attr[ s[ 0 ] ] = s[ 1 ];
              }
          }
  
          return attr;
      }
  
      function split_meta_hash( meta_string ) {
          var meta = meta_string.split( "" ),
              parts = [ "" ],
              in_quotes = false;
  
          while ( meta.length ) {
              var letter = meta.shift();
              switch ( letter ) {
                  case " " :
                      // if we're in a quoted section, keep it
                      if ( in_quotes ) {
                          parts[ parts.length - 1 ] += letter;
                      }
                      // otherwise make a new part
                      else {
                          parts.push( "" );
                      }
                      break;
                  case "'" :
                  case '"' :
                      // reverse the quotes and move straight on
                      in_quotes = !in_quotes;
                      break;
                  case "\\" :
                      // shift off the next letter to be used straight away.
                      // it was escaped so we'll keep it whatever it is
                      letter = meta.shift();
                  default :
                      parts[ parts.length - 1 ] += letter;
                      break;
              }
          }
  
          return parts;
      }
  
      Markdown.dialects.Maruku.block.document_meta = function document_meta( block, next ) {
          // we're only interested in the first block
          if ( block.lineNumber > 1 ) return undefined;
  
          // document_meta blocks consist of one or more lines of `Key: Value\n`
          if ( ! block.match( /^(?:\w+:.*\n)*\w+:.*$/ ) ) return undefined;
  
          // make an attribute node if it doesn't exist
          if ( !extract_attr( this.tree ) ) {
              this.tree.splice( 1, 0, {} );
          }
  
          var pairs = block.split( /\n/ );
          for ( p in pairs ) {
              var m = pairs[ p ].match( /(\w+):\s*(.*)$/ ),
                  key = m[ 1 ].toLowerCase(),
                  value = m[ 2 ];
  
              this.tree[ 1 ][ key ] = value;
          }
  
          // document_meta produces no content!
          return [];
      };
  
      Markdown.dialects.Maruku.block.block_meta = function block_meta( block, next ) {
          // check if the last line of the block is an meta hash
          var m = block.match( /(^|\n) {0,3}\{:\s*((?:\\\}|[^\}])*)\s*\}$/ );
          if ( !m ) return undefined;
  
          // process the meta hash
          var attr = this.dialect.processMetaHash( m[ 2 ] );
  
          var hash;
  
          // if we matched ^ then we need to apply meta to the previous block
          if ( m[ 1 ] === "" ) {
              var node = this.tree[ this.tree.length - 1 ];
              hash = extract_attr( node );
  
              // if the node is a string (rather than JsonML), bail
              if ( typeof node === "string" ) return undefined;
  
              // create the attribute hash if it doesn't exist
              if ( !hash ) {
                  hash = {};
                  node.splice( 1, 0, hash );
              }
  
              // add the attributes in
              for ( a in attr ) {
                  hash[ a ] = attr[ a ];
              }
  
              // return nothing so the meta hash is removed
              return [];
          }
  
          // pull the meta hash off the block and process what's left
          var b = block.replace( /\n.*$/, "" ),
              result = this.processBlock( b, [] );
  
          // get or make the attributes hash
          hash = extract_attr( result[ 0 ] );
          if ( !hash ) {
              hash = {};
              result[ 0 ].splice( 1, 0, hash );
          }
  
          // attach the attributes to the block
          for ( a in attr ) {
              hash[ a ] = attr[ a ];
          }
  
          return result;
      };
  
      Markdown.dialects.Maruku.block.definition_list = function definition_list( block, next ) {
          // one or more terms followed by one or more definitions, in a single block
          var tight = /^((?:[^\s:].*\n)+):\s+([\s\S]+)$/,
              list = [ "dl" ],
              i, m;
  
          // see if we're dealing with a tight or loose block
          if ( ( m = block.match( tight ) ) ) {
              // pull subsequent tight DL blocks out of `next`
              var blocks = [ block ];
              while ( next.length && tight.exec( next[ 0 ] ) ) {
                  blocks.push( next.shift() );
              }
  
              for ( var b = 0; b < blocks.length; ++b ) {
                  var m = blocks[ b ].match( tight ),
                      terms = m[ 1 ].replace( /\n$/, "" ).split( /\n/ ),
                      defns = m[ 2 ].split( /\n:\s+/ );
  
                  // print( uneval( m ) );
  
                  for ( i = 0; i < terms.length; ++i ) {
                      list.push( [ "dt", terms[ i ] ] );
                  }
  
                  for ( i = 0; i < defns.length; ++i ) {
                      // run inline processing over the definition
                      list.push( [ "dd" ].concat( this.processInline( defns[ i ].replace( /(\n)\s+/, "$1" ) ) ) );
                  }
              }
          }
          else {
              return undefined;
          }
  
          return [ list ];
      };
  
  // splits on unescaped instances of @ch. If @ch is not a character the result
  // can be unpredictable
  
      Markdown.dialects.Maruku.block.table = function table (block, next) {
  
          var _split_on_unescaped = function(s, ch) {
              ch = ch || '\\s';
              if (ch.match(/^[\\|\[\]{}?*.+^$]$/)) { ch = '\\' + ch; }
              var res = [ ],
                  r = new RegExp('^((?:\\\\.|[^\\\\' + ch + '])*)' + ch + '(.*)'),
                  m;
              while(m = s.match(r)) {
                  res.push(m[1]);
                  s = m[2];
              }
              res.push(s);
              return res;
          }
  
          var leading_pipe = /^ {0,3}\|(.+)\n {0,3}\|\s*([\-:]+[\-| :]*)\n((?:\s*\|.*(?:\n|$))*)(?=\n|$)/,
              // find at least an unescaped pipe in each line
              no_leading_pipe = /^ {0,3}(\S(?:\\.|[^\\|])*\|.*)\n {0,3}([\-:]+\s*\|[\-| :]*)\n((?:(?:\\.|[^\\|])*\|.*(?:\n|$))*)(?=\n|$)/,
              i, m;
          if (m = block.match(leading_pipe)) {
              // remove leading pipes in contents
              // (header and horizontal rule already have the leading pipe left out)
              m[3] = m[3].replace(/^\s*\|/gm, '');
          } else if (! ( m = block.match(no_leading_pipe))) {
              return undefined;
          }
  
          var table = [ "table", [ "thead", [ "tr" ] ], [ "tbody" ] ];
  
          // remove trailing pipes, then split on pipes
          // (no escaped pipes are allowed in horizontal rule)
          m[2] = m[2].replace(/\|\s*$/, '').split('|');
  
          // process alignment
          var html_attrs = [ ];
          forEach (m[2], function (s) {
              if (s.match(/^\s*-+:\s*$/))       html_attrs.push({align: "right"});
              else if (s.match(/^\s*:-+\s*$/))  html_attrs.push({align: "left"});
              else if (s.match(/^\s*:-+:\s*$/)) html_attrs.push({align: "center"});
              else                              html_attrs.push({});
          });
  
          // now for the header, avoid escaped pipes
          m[1] = _split_on_unescaped(m[1].replace(/\|\s*$/, ''), '|');
          for (i = 0; i < m[1].length; i++) {
              table[1][1].push(['th', html_attrs[i] || {}].concat(
                  this.processInline(m[1][i].trim())));
          }
  
          // now for body contents
          forEach (m[3].replace(/\|\s*$/mg, '').split('\n'), function (row) {
              var html_row = ['tr'];
              row = _split_on_unescaped(row, '|');
              for (i = 0; i < row.length; i++) {
                  html_row.push(['td', html_attrs[i] || {}].concat(this.processInline(row[i].trim())));
              }
              table[2].push(html_row);
          }, this);
  
          return [table];
      }
  
      Markdown.dialects.Maruku.inline[ "{:" ] = function inline_meta( text, matches, out ) {
          if ( !out.length ) {
              return [ 2, "{:" ];
          }
  
          // get the preceeding element
          var before = out[ out.length - 1 ];
  
          if ( typeof before === "string" ) {
              return [ 2, "{:" ];
          }
  
          // match a meta hash
          var m = text.match( /^\{:\s*((?:\\\}|[^\}])*)\s*\}/ );
  
          // no match, false alarm
          if ( !m ) {
              return [ 2, "{:" ];
          }
  
          // attach the attributes to the preceeding element
          var meta = this.dialect.processMetaHash( m[ 1 ] ),
              attr = extract_attr( before );
  
          if ( !attr ) {
              attr = {};
              before.splice( 1, 0, attr );
          }
  
          for ( var k in meta ) {
              attr[ k ] = meta[ k ];
          }
  
          // cut out the string and replace it with nothing
          return [ m[ 0 ].length, "" ];
      };
  
      Markdown.dialects.Maruku.inline.__escape__ = /^\\[\\`\*_{}\[\]()#\+.!\-|:]/;
  
      Markdown.buildBlockOrder ( Markdown.dialects.Maruku.block );
      Markdown.buildInlinePatterns( Markdown.dialects.Maruku.inline );
  
      var isArray = Array.isArray || function(obj) {
              return Object.prototype.toString.call(obj) == "[object Array]";
          };
  
      var forEach;
  // Don't mess with Array.prototype. Its not friendly
      if ( Array.prototype.forEach ) {
          forEach = function( arr, cb, thisp ) {
              return arr.forEach( cb, thisp );
          };
      }
      else {
          forEach = function(arr, cb, thisp) {
              for (var i = 0; i < arr.length; i++) {
                  cb.call(thisp || arr, arr[i], i, arr);
              }
          }
      }
  
      var isEmpty = function( obj ) {
          for ( var key in obj ) {
              if ( hasOwnProperty.call( obj, key ) ) {
                  return false;
              }
          }
  
          return true;
      }
  
      function extract_attr( jsonml ) {
          return isArray(jsonml)
          && jsonml.length > 1
          && typeof jsonml[ 1 ] === "object"
          && !( isArray(jsonml[ 1 ]) )
              ? jsonml[ 1 ]
              : undefined;
      }
  
  
  
      /**
       *  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.
       */
      expose.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" );
      };
  
      function escapeHTML( text ) {
          return text.replace( /&/g, "&amp;" )
              .replace( /</g, "&lt;" )
              .replace( />/g, "&gt;" )
              .replace( /"/g, "&quot;" )
              .replace( /'/g, "&#39;" );
      }
  
      function render_tree( jsonml ) {
          // basic case
          if ( typeof jsonml === "string" ) {
              return escapeHTML( jsonml );
          }
  
          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 = "";
          for ( var a in attributes ) {
              tag_attrs += " " + a + '="' + escapeHTML( attributes[ a ] ) + '"';
          }
  
          // 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;
              }
          }
      }
  
  } )( (function() {
      if ( typeof exports === "undefined" ) {
          window.markdown = {};
          return window.markdown;
      }
      else {
          return exports;
      }
  } )() );
  