ux/Showdown.js

[roojs1] / ux / Showdown.js

//
// showdown.js -- A javascript port of Markdown.
//
// Copyright (c) 2007 John Fraser.
//
// Original Markdown Copyright (c) 2004-2005 John Gruber
//   <http://daringfireball.net/projects/markdown/>
//
// Redistributable under a BSD-style open source license.
// See license.txt for more information.
//
// The full source distribution is at:
//
//                              A A L
//                              T C A
//                              T K B
//
//   <http://www.attacklab.net/>
//

//
// Wherever possible, Showdown is a straight, line-by-line port
// of the Perl version of Markdown.
//
// This is not a normal parser design; it's basically just a
// series of string substitutions.  It's hard to read and
// maintain this way,  but keeping Showdown close to the original
// design makes it easier to port new features.
//
// More importantly, Showdown behaves like markdown.pl in most
// edge cases.  So web applications can do client-side preview
// in Javascript, and then build identical HTML on the server.
//
// This port needs the new RegExp functionality of ECMA 262,
// 3rd Edition (i.e. Javascript 1.5).  Most modern web browsers
// should do fine.  Even with the new regular expression features,
// We do a lot of work to emulate Perl's regex functionality.
// The tricky changes in this file mostly have the "attacklab:"
// label.  Major or self-explanatory changes don't.
//
// Smart diff tools like Araxis Merge will be able to match up
// this file with markdown.pl in a useful way.  A little tweaking
// helps: in a copy of markdown.pl, replace "#" with "//" and
// replace "$text" with "text".  Be sure to ignore whitespace
// and line endings.
//


//
// Showdown usage:
// 
//   alert( Roo.ux.Showdown.toHtml("Markdown *rocks*.") );
// 
// Note: move the sample code to the bottom of this
// file before uncommenting it.
//


//
// Showdown namespace
//
Roo.namespace('Roo.ux'); 
Roo.ux.Showdown = {};
Roo.ux.Showdown.toHtml = function(text) {
    var c = new Roo.ux.Showdown.converter();
    return c.makeHtml(text);
};
//
// converter
//
// Wraps all "globals" so that the only thing
// exposed is makeHtml().
//
Roo.ux.Showdown.converter = function() {
    
    //
    // Globals:
    //
    
    // Global hashes, used by various utility routines
    var g_urls;
    var g_titles;
    var g_html_blocks;
    
    // Used to track when we're inside an ordered or unordered list
    // (see _ProcessListItems() for details):
    var g_list_level = 0;
    
    
    this.makeHtml = function(_text) {
    //
    // Main function. The order in which other subs are called here is
    // essential. Link and image substitutions need to happen before
    // _EscapeSpecialCharsWithinTagAttributes(), so that any *'s or _'s in the <a>
    // and <img> tags get encoded.
    //v
            var text = '' + _text;
            // Clear the global hashes. If we don't clear these, you get conflicts
            // from other articles when generating a page which contains more than
            // one article (e.g. an index page that shows the N most recent
            // articles):
            g_urls = new Array();
            g_titles = new Array();
            g_html_blocks = new Array();
    
            // attacklab: Replace ~ with ~T
            // This lets us use tilde as an escape char to avoid md5 hashes
            // The choice of character is arbitray; anything that isn't
        // magic in Markdown will work.
            text = text.replace(/~/g,"~T");
    
            // attacklab: Replace $ with ~D
            // RegExp interprets $ as a special character
            // when it's in a replacement string
            text = text.replace(/\$/g,"~D");
    
            // Standardize line endings
            text = text.replace(/\r\n/g,"\n"); // DOS to Unix
            text = text.replace(/\r/g,"\n"); // Mac to Unix
    
            // Make sure text begins and ends with a couple of newlines:
            text = "\n\n" + text + "\n\n";
    
            // Convert all tabs to spaces.
            text = _Detab(text);
    
            // Strip any lines consisting only of spaces and tabs.
            // This makes subsequent regexen easier to write, because we can
            // match consecutive blank lines with /\n+/ instead of something
            // contorted like /[ \t]*\n+/ .
            text = text.replace(/^[ \t]+$/mg,"");
    
            text = _DoCodeBlocks(text);
    
            // Turn block-level HTML blocks into hash entries
            text = _HashHTMLBlocks(text);
    
            // Strip link definitions, store in hashes.
            text = _StripLinkDefinitions(text);
    
            text = _RunBlockGamut(text);
    
            text = _UnescapeSpecialChars(text);
    
            // attacklab: Restore dollar signs
            text = text.replace(/~D/g,"$$");
    
            // attacklab: Restore tildes
            text = text.replace(/~T/g,"~");
    
            return text;
    }
    
    
    var _StripLinkDefinitions = function(text) {
    //
    // Strips link definitions from text, stores the URLs and titles in
    // hash references.
    //
    
            // Link defs are in the form: ^[id]: url "optional title"
    
            /*
                    var text = text.replace(/
                                    ^[ ]{0,3}\[(.+)\]:  // id = $1  attacklab: g_tab_width - 1
                                      [ \t]*
                                      \n?                               // maybe *one* newline
                                      [ \t]*
                                    <?(\S+?)>?                  // url = $2
                                      [ \t]*
                                      \n?                               // maybe one newline
                                      [ \t]*
                                    (?:
                                      (\n*)                             // any lines skipped = $3 attacklab: lookbehind removed
                                      ["(]
                                      (.+?)                             // title = $4
                                      [")]
                                      [ \t]*
                                    )?                                  // title is optional
                                    (?:\n+|$)
                              /gm,
                              function(){...});
            */
            text = text.replace(/^[ ]{0,3}\[(.+)\]:[ \t]*\n?[ \t]*<?(\S+?)>?[ \t]*\n?[ \t]*(?:(\n*)["(](.+?)[")][ \t]*)?(?:\n+|\Z)/gm,
                    function (wholeMatch,m1,m2,m3,m4) {
                            m1 = m1.toLowerCase();
                            g_urls[m1] = _EncodeAmpsAndAngles(m2);  // Link IDs are case-insensitive
                            if (m3) {
                                    // Oops, found blank lines, so it's not a title.
                                    // Put back the parenthetical statement we stole.
                                    return m3+m4;
                            } else if (m4) {
                                    g_titles[m1] = m4.replace(/"/g,"&quot;");
                            }
                            
                            // Completely remove the definition from the text
                            return "";
                    }
            );
    
            return text;
    }
    
    
    var _HashHTMLBlocks = function(text) {
            // attacklab: Double up blank lines to reduce lookaround
            text = text.replace(/\n/g,"\n\n");
    
            // Hashify HTML blocks:
            // We only want to do this for block-level HTML tags, such as headers,
            // lists, and tables. That's because we still want to wrap <p>s around
            // "paragraphs" that are wrapped in non-block-level tags, such as anchors,
            // phrase emphasis, and spans. The list of tags we're looking for is
            // hard-coded:
            var block_tags_a = "p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|script|noscript|form|fieldset|iframe|math|ins|del"
            var block_tags_b = "p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|script|noscript|form|fieldset|iframe|math"
    
            // First, look for nested blocks, e.g.:
            //   <div>
            //     <div>
            //     tags for inner block must be indented.
            //     </div>
            //   </div>
            //
            // The outermost tags must start at the left margin for this to match, and
            // the inner nested divs must be indented.
            // We need to do this before the next, more liberal match, because the next
            // match will start at the first `<div>` and stop at the first `</div>`.
    
            // attacklab: This regex can be expensive when it fails.
            /*
                    var text = text.replace(/
                    (                                           // save in $1
                            ^                                   // start of line  (with /m)
                            <($block_tags_a)    // start tag = $2
                            \b                                  // word break
                                                                    // attacklab: hack around khtml/pcre bug...
                            [^\r]*?\n                   // any number of lines, minimally matching
                            </\2>                               // the matching end tag
                            [ \t]*                              // trailing spaces/tabs
                            (?=\n+)                             // followed by a newline
                    )                                           // attacklab: there are sentinel newlines at end of document
                    /gm,function(){...}};
            */
            text = text.replace(/^(<(p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|script|noscript|form|fieldset|iframe|math|ins|del)\b[^\r]*?\n<\/\2>[ \t]*(?=\n+))/gm,hashElement);
    
            //
            // Now match more liberally, simply from `\n<tag>` to `</tag>\n`
            //
    
            /*
                    var text = text.replace(/
                    (                                           // save in $1
                            ^                                   // start of line  (with /m)
                            <($block_tags_b)    // start tag = $2
                            \b                                  // word break
                                                                    // attacklab: hack around khtml/pcre bug...
                            [^\r]*?                             // any number of lines, minimally matching
                            .*</\2>                             // the matching end tag
                            [ \t]*                              // trailing spaces/tabs
                            (?=\n+)                             // followed by a newline
                    )                                           // attacklab: there are sentinel newlines at end of document
                    /gm,function(){...}};
            */
            text = text.replace(/^(<(p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|script|noscript|form|fieldset|iframe|math)\b[^\r]*?.*<\/\2>[ \t]*(?=\n+)\n)/gm,hashElement);
    
            // Special case just for <hr />. It was easier to make a special case than
            // to make the other regex more complicated.  
    
            /*
                    text = text.replace(/
                    (                                           // save in $1
                            \n\n                                // Starting after a blank line
                            [ ]{0,3}
                            (<(hr)                              // start tag = $2
                            \b                                  // word break
                            ([^<>])*?                   // 
                            \/?>)                               // the matching end tag
                            [ \t]*
                            (?=\n{2,})                  // followed by a blank line
                    )
                    /g,hashElement);
            */
            text = text.replace(/(\n[ ]{0,3}(<(hr)\b([^<>])*?\/?>)[ \t]*(?=\n{2,}))/g,hashElement);
    
            // Special case for standalone HTML comments:
    
            /*
                    text = text.replace(/
                    (                                           // save in $1
                            \n\n                                // Starting after a blank line
                            [ ]{0,3}                    // attacklab: g_tab_width - 1
                            <!
                            (--[^\r]*?--\s*)+
                            >
                            [ \t]*
                            (?=\n{2,})                  // followed by a blank line
                    )
                    /g,hashElement);
            */
            text = text.replace(/(\n\n[ ]{0,3}<!(--[^\r]*?--\s*)+>[ \t]*(?=\n{2,}))/g,hashElement);
    
            // PHP and ASP-style processor instructions (<?...?> and <%...%>)
    
            /*
                    text = text.replace(/
                    (?:
                            \n\n                                // Starting after a blank line
                    )
                    (                                           // save in $1
                            [ ]{0,3}                    // attacklab: g_tab_width - 1
                            (?:
                                    <([?%])                     // $2
                                    [^\r]*?
                                    \2>
                            )
                            [ \t]*
                            (?=\n{2,})                  // followed by a blank line
                    )
                    /g,hashElement);
            */
            text = text.replace(/(?:\n\n)([ ]{0,3}(?:<([?%])[^\r]*?\2>)[ \t]*(?=\n{2,}))/g,hashElement);
    
            // attacklab: Undo double lines (see comment at top of this function)
            text = text.replace(/\n\n/g,"\n");
            return text;
    }
    
    var hashElement = function(wholeMatch,m1) {
            var blockText = m1;
    
            // Undo double lines
            blockText = blockText.replace(/\n\n/g,"\n");
            blockText = blockText.replace(/^\n/,"");
            
            // strip trailing blank lines
            blockText = blockText.replace(/\n+$/g,"");
            
            // Replace the element text with a marker ("~KxK" where x is its key)
            blockText = "\n\n~K" + (g_html_blocks.push(blockText)-1) + "K\n\n";
            
            return blockText;
    };
    
    var _RunBlockGamut = function(text) {
    //
    // These are all the transformations that form block-level
    // tags like paragraphs, headers, and list items.
    //
            // code blocks first... so content does not get translated..
            text = _DoCodeBlocks(text);
            
            text = _DoHeaders(text);
    
            // Do Horizontal Rules:
            var key = hashBlock("<hr />");
            text = text.replace(/^[ ]{0,2}([ ]?\*[ ]?){3,}[ \t]*$/gm,key);
            text = text.replace(/^[ ]{0,2}([ ]?\-[ ]?){3,}[ \t]*$/gm,key);
            text = text.replace(/^[ ]{0,2}([ ]?\_[ ]?){3,}[ \t]*$/gm,key);
    
            text = _DoLists(text);
    
            text = _DoBlockQuotes(text);
    
            // We already ran _HashHTMLBlocks() before, in Markdown(), but that
            // was to escape raw HTML in the original Markdown source. This time,
            // we're escaping the markup we've just created, so that we don't wrap
            // <p> tags around block-level tags.
           
            text = _FormParagraphs(text);
            text = _HashHTMLBlocks(text);
            return text;
    }
    
    
    var _RunSpanGamut = function(text) {
    //
    // These are all the transformations that occur *within* block-level
    // tags like paragraphs, headers, and list items.
    //
    
            text = _DoCodeSpans(text);
            text = _EscapeSpecialCharsWithinTagAttributes(text);
            text = _EncodeBackslashEscapes(text);
    
            // Process anchor and image tags. Images must come first,
            // because ![foo][f] looks like an anchor.
            text = _DoImages(text);
            text = _DoAnchors(text);
    
            // Make links out of things like `<http://example.com/>`
            // Must come after _DoAnchors(), because you can use < and >
            // delimiters in inline links like [this](<url>).
            text = _DoAutoLinks(text);
            text = _EncodeAmpsAndAngles(text);
            text = _DoItalicsAndBold(text);
    
            // Do hard breaks:
            text = text.replace(/  +\n/g," <br />\n");
    
            return text;
    }
    
    var _EscapeSpecialCharsWithinTagAttributes = function(text) {
    //
    // Within tags -- meaning between < and > -- encode [\ ` * _] so they
    // don't conflict with their use in Markdown for code, italics and strong.
    //
    
            // Build a regex to find HTML tags and comments.  See Friedl's 
            // "Mastering Regular Expressions", 2nd Ed., pp. 200-201.
            var regex = /(<[a-z\/!$]("[^"]*"|'[^']*'|[^'">])*>|<!(--.*?--\s*)+>)/gi;
    
            text = text.replace(regex, function(wholeMatch) {
                    var tag = wholeMatch.replace(/(.)<\/?code>(?=.)/g,"$1`");
                    tag = escapeCharacters(tag,"\\`*_");
                    return tag;
            });
    
            return text;
    }
    
    var _DoAnchors = function(text) {
    //
    // Turn Markdown link shortcuts into XHTML <a> tags.
    //
            //
            // First, handle reference-style links: [link text] [id]
            //
    
            /*
                    text = text.replace(/
                    (                                                   // wrap whole match in $1
                            \[
                            (
                                    (?:
                                            \[[^\]]*\]          // allow brackets nested one level
                                            |
                                            [^\[]                       // or anything else
                                    )*
                            )
                            \]
    
                            [ ]?                                        // one optional space
                            (?:\n[ ]*)?                         // one optional newline followed by spaces
    
                            \[
                            (.*?)                                       // id = $3
                            \]
                    )()()()()                                   // pad remaining backreferences
                    /g,_DoAnchors_callback);
            */
            text = text.replace(/(\[((?:\[[^\]]*\]|[^\[\]])*)\][ ]?(?:\n[ ]*)?\[(.*?)\])()()()()/g,writeAnchorTag);
    
            //
            // Next, inline-style links: [link text](url "optional title")
            //
    
            /*
                    text = text.replace(/
                            (                                           // wrap whole match in $1
                                    \[
                                    (
                                            (?:
                                                    \[[^\]]*\]  // allow brackets nested one level
                                            |
                                            [^\[\]]                     // or anything else
                                    )
                            )
                            \]
                            \(                                          // literal paren
                            [ \t]*
                            ()                                          // no id, so leave $3 empty
                            <?(.*?)>?                           // href = $4
                            [ \t]*
                            (                                           // $5
                                    (['"])                              // quote char = $6
                                    (.*?)                               // Title = $7
                                    \6                                  // matching quote
                                    [ \t]*                              // ignore any spaces/tabs between closing quote and )
                            )?                                          // title is optional
                            \)
                    )
                    /g,writeAnchorTag);
            */
            text = text.replace(/(\[((?:\[[^\]]*\]|[^\[\]])*)\]\([ \t]*()<?(.*?)>?[ \t]*((['"])(.*?)\6[ \t]*)?\))/g,writeAnchorTag);
    
            //
            // Last, handle reference-style shortcuts: [link text]
            // These must come last in case you've also got [link test][1]
            // or [link test](/foo)
            //
    
            /*
                    text = text.replace(/
                    (                                                   // wrap whole match in $1
                            \[
                            ([^\[\]]+)                          // link text = $2; can't contain '[' or ']'
                            \]
                    )()()()()()                                 // pad rest of backreferences
                    /g, writeAnchorTag);
            */
            text = text.replace(/(\[([^\[\]]+)\])()()()()()/g, writeAnchorTag);
    
            return text;
    }
    
    var writeAnchorTag = function(wholeMatch,m1,m2,m3,m4,m5,m6,m7) {
            if (m7 == undefined) m7 = "";
            var whole_match = m1;
            var link_text   = m2;
            var link_id  = m3.toLowerCase();
            var url             = m4;
            var title   = m7;
            
            if (url == "") {
                    if (link_id == "") {
                            // lower-case and turn embedded newlines into spaces
                            link_id = link_text.toLowerCase().replace(/ ?\n/g," ");
                    }
                    url = "#"+link_id;
                    
                    if (g_urls[link_id] != undefined) {
                            url = g_urls[link_id];
                            if (g_titles[link_id] != undefined) {
                                    title = g_titles[link_id];
                            }
                    }
                    else {
                            if (whole_match.search(/\(\s*\)$/m)>-1) {
                                    // Special case for explicit empty url
                                    url = "";
                            } else {
                                    return whole_match;
                            }
                    }
            }   
            
            url = escapeCharacters(url,"*_");
            var result = "<a href=\"" + url + "\"";
            
            if (title != "") {
                    title = title.replace(/"/g,"&quot;");
                    title = escapeCharacters(title,"*_");
                    result +=  " title=\"" + title + "\"";
            }
            
            result += ">" + link_text + "</a>";
            
            return result;
    }
    
    
    var _DoImages = function(text) {
    //
    // Turn Markdown image shortcuts into <img> tags.
    //
    
            //
            // First, handle reference-style labeled images: ![alt text][id]
            //
    
            /*
                    text = text.replace(/
                    (                                           // wrap whole match in $1
                            !\[
                            (.*?)                               // alt text = $2
                            \]
    
                            [ ]?                                // one optional space
                            (?:\n[ ]*)?                 // one optional newline followed by spaces
    
                            \[
                            (.*?)                               // id = $3
                            \]
                    )()()()()                           // pad rest of backreferences
                    /g,writeImageTag);
            */
            text = text.replace(/(!\[(.*?)\][ ]?(?:\n[ ]*)?\[(.*?)\])()()()()/g,writeImageTag);
    
            //
            // Next, handle inline images:  ![alt text](url "optional title")
            // Don't forget: encode * and _
    
            /*
                    text = text.replace(/
                    (                                           // wrap whole match in $1
                            !\[
                            (.*?)                               // alt text = $2
                            \]
                            \s?                                 // One optional whitespace character
                            \(                                  // literal paren
                            [ \t]*
                            ()                                  // no id, so leave $3 empty
                            <?(\S+?)>?                  // src url = $4
                            [ \t]*
                            (                                   // $5
                                    (['"])                      // quote char = $6
                                    (.*?)                       // title = $7
                                    \6                          // matching quote
                                    [ \t]*
                            )?                                  // title is optional
                    \)
                    )
                    /g,writeImageTag);
            */
            text = text.replace(/(!\[(.*?)\]\s?\([ \t]*()<?(\S+?)>?[ \t]*((['"])(.*?)\6[ \t]*)?\))/g,writeImageTag);
    
            return text;
    }
    
    var writeImageTag = function(wholeMatch,m1,m2,m3,m4,m5,m6,m7) {
            var whole_match = m1;
            var alt_text   = m2;
            var link_id  = m3.toLowerCase();
            var url             = m4;
            var title   = m7;
    
            if (!title) title = "";
            
            if (url == "") {
                    if (link_id == "") {
                            // lower-case and turn embedded newlines into spaces
                            link_id = alt_text.toLowerCase().replace(/ ?\n/g," ");
                    }
                    url = "#"+link_id;
                    
                    if (g_urls[link_id] != undefined) {
                            url = g_urls[link_id];
                            if (g_titles[link_id] != undefined) {
                                    title = g_titles[link_id];
                            }
                    }
                    else {
                            return whole_match;
                    }
            }   
            
            alt_text = alt_text.replace(/"/g,"&quot;");
            url = escapeCharacters(url,"*_");
            var result = "<img src=\"" + url + "\" alt=\"" + alt_text + "\"";
    
            // attacklab: Markdown.pl adds empty title attributes to images.
            // Replicate this bug.
    
            //if (title != "") {
                    title = title.replace(/"/g,"&quot;");
                    title = escapeCharacters(title,"*_");
                    result +=  " title=\"" + title + "\"";
            //}
            
            result += " />";
            
            return result;
    }
    
    
    var _DoHeaders = function(text) {
    
            // Setext-style headers:
            //  Header 1
            //  ========
            //  
            //  Header 2
            //  --------
            //
            text = text.replace(/^(.+)[ \t]*\n=+[ \t]*\n+/gm,
                    function(wholeMatch,m1){return hashBlock('<h1 id="' + headerId(m1) + '">' + _RunSpanGamut(m1) + "</h1>");});
    
            text = text.replace(/^(.+)[ \t]*\n-+[ \t]*\n+/gm,
                    function(matchFound,m1){return hashBlock('<h2 id="' + headerId(m1) + '">' + _RunSpanGamut(m1) + "</h2>");});
    
            // atx-style headers:
            //  # Header 1
            //  ## Header 2
            //  ## Header 2 with closing hashes ##
            //  ...
            //  ###### Header 6
            //
    
            /*
                    text = text.replace(/
                            ^(\#{1,6})                          // $1 = string of #'s
                            [ \t]*
                            (.+?)                                       // $2 = Header text
                            [ \t]*
                            \#*                                         // optional closing #'s (not counted)
                            \n+
                    /gm, function() {...});
            */
    
            text = text.replace(/^(\#{1,6})[ \t]*(.+?)[ \t]*\#*\n+/gm,
                    function(wholeMatch,m1,m2) {
                            var h_level = m1.length;
                            return hashBlock("<h" + h_level + ' id="' + headerId(m2) + '">' + _RunSpanGamut(m2) + "</h" + h_level + ">");
                    });
    
            function headerId(m) {
                    return m.replace(/[^\w]/g, '').toLowerCase();
            }
            return text;
    }
    
    // This declaration keeps Dojo compressor from outputting garbage:
    var _ProcessListItems;
    
    var _DoLists = function(text) {
    //
    // Form HTML ordered (numbered) and unordered (bulleted) lists.
    //
    
            // attacklab: add sentinel to hack around khtml/safari bug:
            // http://bugs.webkit.org/show_bug.cgi?id=11231
            text += "~0";
    
            // Re-usable pattern to match any entirel ul or ol list:
    
            /*
                    var whole_list = /
                    (                                                                   // $1 = whole list
                            (                                                           // $2
                                    [ ]{0,3}                                    // attacklab: g_tab_width - 1
                                    ([*+-]|\d+[.])                              // $3 = first list item marker
                                    [ \t]+
                            )
                            [^\r]+?
                            (                                                           // $4
                                    ~0                                                  // sentinel for workaround; should be $
                            |
                                    \n{2,}
                                    (?=\S)
                                    (?!                                                 // Negative lookahead for another list item marker
                                            [ \t]*
                                            (?:[*+-]|\d+[.])[ \t]+
                                    )
                            )
                    )/g
            */
            var whole_list = /^(([ ]{0,3}([*+-]|\d+[.])[ \t]+)[^\r]+?(~0|\n{2,}(?=\S)(?![ \t]*(?:[*+-]|\d+[.])[ \t]+)))/gm;
    
            if (g_list_level) {
                    text = text.replace(whole_list,function(wholeMatch,m1,m2) {
                            var list = m1;
                            var list_type = (m2.search(/[*+-]/g)>-1) ? "ul" : "ol";
    
                            // Turn double returns into triple returns, so that we can make a
                            // paragraph for the last item in a list, if necessary:
                            list = list.replace(/\n{2,}/g,"\n\n\n");;
                            var result = _ProcessListItems(list);
            
                            // Trim any trailing whitespace, to put the closing `</$list_type>`
                            // up on the preceding line, to get it past the current stupid
                            // HTML block parser. This is a hack to work around the terrible
                            // hack that is the HTML block parser.
                            result = result.replace(/\s+$/,"");
                            result = "<"+list_type+">" + result + "</"+list_type+">\n";
                            return result;
                    });
            } else {
                    whole_list = /(\n\n|^\n?)(([ ]{0,3}([*+-]|\d+[.])[ \t]+)[^\r]+?(~0|\n{2,}(?=\S)(?![ \t]*(?:[*+-]|\d+[.])[ \t]+)))/g;
                    text = text.replace(whole_list,function(wholeMatch,m1,m2,m3) {
                            var runup = m1;
                            var list = m2;
    
                            var list_type = (m3.search(/[*+-]/g)>-1) ? "ul" : "ol";
                            // Turn double returns into triple returns, so that we can make a
                            // paragraph for the last item in a list, if necessary:
                            var list = list.replace(/\n{2,}/g,"\n\n\n");;
                            var result = _ProcessListItems(list);
                            result = runup + "<"+list_type+">\n" + result + "</"+list_type+">\n";       
                            return result;
                    });
            }
    
            // attacklab: strip sentinel
            text = text.replace(/~0/,"");
    
            return text;
    }
    
    _ProcessListItems = function(list_str) {
    //
    //  Process the contents of a single ordered or unordered list, splitting it
    //  into individual list items.
    //
            // The $g_list_level global keeps track of when we're inside a list.
            // Each time we enter a list, we increment it; when we leave a list,
            // we decrement. If it's zero, we're not in a list anymore.
            //
            // We do this because when we're not inside a list, we want to treat
            // something like this:
            //
            //    I recommend upgrading to version
            //    8. Oops, now this line is treated
            //    as a sub-list.
            //
            // As a single paragraph, despite the fact that the second line starts
            // with a digit-period-space sequence.
            //
            // Whereas when we're inside a list (or sub-list), that line will be
            // treated as the start of a sub-list. What a kludge, huh? This is
            // an aspect of Markdown's syntax that's hard to parse perfectly
            // without resorting to mind-reading. Perhaps the solution is to
            // change the syntax rules such that sub-lists must start with a
            // starting cardinal number; e.g. "1." or "a.".
    
            g_list_level++;
    
            // trim trailing blank lines:
            list_str = list_str.replace(/\n{2,}$/,"\n");
    
            // attacklab: add sentinel to emulate \z
            list_str += "~0";
    
            /*
                    list_str = list_str.replace(/
                            (\n)?                                                       // leading line = $1
                            (^[ \t]*)                                           // leading whitespace = $2
                            ([*+-]|\d+[.]) [ \t]+                       // list marker = $3
                            ([^\r]+?                                            // list item text   = $4
                            (\n{1,2}))
                            (?= \n* (~0 | \2 ([*+-]|\d+[.]) [ \t]+))
                    /gm, function(){...});
            */
            list_str = list_str.replace(/(\n)?(^[ \t]*)([*+-]|\d+[.])[ \t]+([^\r]+?(\n{1,2}))(?=\n*(~0|\2([*+-]|\d+[.])[ \t]+))/gm,
                    function(wholeMatch,m1,m2,m3,m4){
                            var item = m4;
                            var leading_line = m1;
                            var leading_space = m2;
    
                            if (leading_line || (item.search(/\n{2,}/)>-1)) {
                                    item = _RunBlockGamut(_Outdent(item));
                            }
                            else {
                                    // Recursion for sub-lists:
                                    item = _DoLists(_Outdent(item));
                                    item = item.replace(/\n$/,""); // chomp(item)
                                    item = _RunSpanGamut(item);
                            }
    
                            return  "<li>" + item + "</li>\n";
                    }
            );
    
            // attacklab: strip sentinel
            list_str = list_str.replace(/~0/g,"");
    
            g_list_level--;
            return list_str;
    }
    
    
    var _DoCodeBlocks = function(text) {
    //
    //  Process Markdown `<pre><code>` blocks.
    //  
    
            /*
                    text = text.replace(text,
                            /(?:\n\n|^)
                            (                                                           // $1 = the code block -- one or more lines, starting with a space/tab
                                    (?:
                                            (?:[ ]{4}|\t)                       // Lines must start with a tab or a tab-width of spaces - attacklab: g_tab_width
                                            .*\n+
                                    )+
                            )
                            (\n*[ ]{0,3}[^ \t\n]|(?=~0))        // attacklab: g_tab_width
                    /g,function(){...});
            */
    
            // attacklab: sentinel workarounds for lack of \A and \Z, safari\khtml bug
            text = text.replace(/~0/,"");
            text += "~0";
            
            text = text.replace(/(?:\n\n|^)((?:(?:[ ]{4}|\t).*\n+)+)(\n*[ ]{0,3}[^ \t\n]|(?=~0))/g,
                    function(wholeMatch,m1,m2) {
                            var codeblock = m1;
                            var nextChar = m2;
                    
                            codeblock = _EncodeCode( _Outdent(codeblock));
                            codeblock = _Detab(codeblock);
                            codeblock = codeblock.replace(/^\n+/g,""); // trim leading newlines
                            codeblock = codeblock.replace(/\n+$/g,""); // trim trailing whitespace
    
                            codeblock = "<pre><code>" + codeblock + "\n</code></pre>";
    
                            return hashBlock(codeblock) + nextChar;
                    }
            );
    
            // attacklab: strip sentinel
            text = text.replace(/~0/,"");
    
    
      
            text += '~0';
          
            text = text.replace(/(?:^|\n)```(.*)\n([\s\S]*?)\n```/g, function (wholeMatch, language, codeblock) {
                    var end =  '\n';
                
                    // First parse the github code block
                    codeblock =  _EncodeCode( codeblock); 
                    codeblock =  _Detab(codeblock);
                    codeblock = codeblock.replace(/^\n+/g, ''); // trim leading newlines
                    codeblock = codeblock.replace(/\n+$/g, ''); // trim trailing whitespace
                
                    codeblock = '<pre><code' + (language ? ' class="' + language + ' language-' + language + '"' : '') + '>' + codeblock + end + '</code></pre>';
                
                    return hashBlock(codeblock) ;
            });
          
            // attacklab: strip sentinel
            text = text.replace(/~0/, '');

          
            return text;
    }
    
    var hashBlock = function(text) {
            text = text.replace(/(^\n+|\n+$)/g,"");
            return "\n\n~K" + (g_html_blocks.push(text)-1) + "K\n\n";
    }
    
    
    var _DoCodeSpans = function(text) {
    //
    //   *  Backtick quotes are used for <code></code> spans.
    // 
    //   *  You can use multiple backticks as the delimiters if you want to
    //   include literal backticks in the code span. So, this input:
    //   
    //           Just type ``foo `bar` baz`` at the prompt.
    //   
    //     Will translate to:
    //   
    //           <p>Just type <code>foo `bar` baz</code> at the prompt.</p>
    //   
    //  There's no arbitrary limit to the number of backticks you
    //  can use as delimters. If you need three consecutive backticks
    //  in your code, use four for delimiters, etc.
    //
    //  *  You can use spaces to get literal backticks at the edges:
    //   
    //           ... type `` `bar` `` ...
    //   
    //     Turns to:
    //   
    //           ... type <code>`bar`</code> ...
    //
    
            /*
                    text = text.replace(/
                            (^|[^\\])                                   // Character before opening ` can't be a backslash
                            (`+)                                                // $2 = Opening run of `
                            (                                                   // $3 = The code block
                                    [^\r]*?
                                    [^`]                                        // attacklab: work around lack of lookbehind
                            )
                            \2                                                  // Matching closer
                            (?!`)
                    /gm, function(){...});
            */
    
            text = text.replace(/(^|[^\\])(`+)([^\r]*?[^`])\2(?!`)/gm,
                    function(wholeMatch,m1,m2,m3,m4) {
                            var c = m3;
                            c = c.replace(/^([ \t]*)/g,"");     // leading whitespace
                            c = c.replace(/[ \t]*$/g,"");       // trailing whitespace
                            c = _EncodeCode(c);
                            return m1+"<code>"+c+"</code>";
                    });
    
            return text;
    }
    
    
    var _EncodeCode = function(text) {
    //
    // Encode/escape certain characters inside Markdown code runs.
    // The point is that in code, these characters are literals,
    // and lose their special Markdown meanings.
    
    // REMOVED - Data going into markdown should be encoded before it enters..
    
    //
            // Encode all ampersands; HTML entities are not
            // entities within a Markdown code span.
            
            
            //text = text.replace(/&/g,"&amp;");
    
            // Do the angle bracket song and dance:
            //text = text.replace(/</g,"&lt;");
            //text = text.replace(/>/g,"&gt;");
    
            // Now, escape characters that are magic in Markdown:
            text = escapeCharacters(text,"\*_{}[]\\",false);
    
    // jj the line above breaks this:
    //---
    
    //* Item
    
    //   1. Subitem
    
    //            special char: *
    //---
    
            return text;
    }
    
    
    var _DoItalicsAndBold = function(text) {
    
            // <strong> must go first:
            text = text.replace(/(\*\*|__)(?=\S)([^\r]*?\S[*_]*)\1/g,
                    "<strong>$2</strong>");
    
            text = text.replace(/(\*|_)(?=\S)([^\r]*?\S)\1/g,
                    "<em>$2</em>");
    
            return text;
    }
    
    
    var _DoBlockQuotes = function(text) {
    
            /*
                    text = text.replace(/
                    (                                                           // Wrap whole match in $1
                            (
                                    ^[ \t]*>[ \t]?                      // '>' at the start of a line
                                    .+\n                                        // rest of the first line
                                    (.+\n)*                                     // subsequent consecutive lines
                                    \n*                                         // blanks
                            )+
                    )
                    /gm, function(){...});
            */
    
            text = text.replace(/((^[ \t]*>[ \t]?.+\n(.+\n)*\n*)+)/gm,
                    function(wholeMatch,m1) {
                            var bq = m1;
    
                            // attacklab: hack around Konqueror 3.5.4 bug:
                            // "----------bug".replace(/^-/g,"") == "bug"
    
                            bq = bq.replace(/^[ \t]*>[ \t]?/gm,"~0");   // trim one level of quoting
    
                            // attacklab: clean up hack
                            bq = bq.replace(/~0/g,"");
    
                            bq = bq.replace(/^[ \t]+$/gm,"");           // trim whitespace-only lines
                            bq = _RunBlockGamut(bq);                            // recurse
                            
                            bq = bq.replace(/(^|\n)/g,"$1  ");
                            // These leading spaces screw with <pre> content, so we need to fix that:
                            bq = bq.replace(
                                            /(\s*<pre>[^\r]+?<\/pre>)/gm,
                                    function(wholeMatch,m1) {
                                            var pre = m1;
                                            // attacklab: hack around Konqueror 3.5.4 bug:
                                            pre = pre.replace(/^  /mg,"~0");
                                            pre = pre.replace(/~0/g,"");
                                            return pre;
                                    });
                            
                            return hashBlock("<blockquote>\n" + bq + "\n</blockquote>");
                    });
            return text;
    }
    
    
    var _FormParagraphs = function(text) {
    //
    //  Params:
    //    $text - string to process with html <p> tags
    //
    
            // Strip leading and trailing lines:
            text = text.replace(/^\n+/g,"");
            text = text.replace(/\n+$/g,"");
    
            var grafs = text.split(/\n{2,}/g);
            var grafsOut = new Array();
    
            //
            // Wrap <p> tags.
            //
            var end = grafs.length;
            for (var i=0; i<end; i++) {
                    var str = grafs[i];
    
                    // if this is an HTML marker, copy it
                    if (str.search(/~K(\d+)K/g) >= 0) {
                            grafsOut.push(str);
                    }
                    else if (str.search(/\S/) >= 0) {
                            str = _RunSpanGamut(str);
                            str = str.replace(/^([ \t]*)/g,"<p>");
                            str += "</p>"
                            grafsOut.push(str);
                    }
    
            }
    
            //
            // Unhashify HTML blocks
            //
            end = grafsOut.length;
            for (var i=0; i<end; i++) {
                    // if this is a marker for an html block...
                    while (grafsOut[i].search(/~K(\d+)K/) >= 0) {
                            var blockText = g_html_blocks[RegExp.$1];
                            blockText = blockText.replace(/\$/g,"$$$$"); // Escape any dollar signs
                            grafsOut[i] = grafsOut[i].replace(/~K\d+K/,blockText);
                    }
            }
    
            return grafsOut.join("\n\n");
    }
    
    
    var _EncodeAmpsAndAngles = function(text) {
    // Smart processing for ampersands and angle brackets that need to be encoded.
            
            // Ampersand-encoding based entirely on Nat Irons's Amputator MT plugin:
            //   http://bumppo.net/projects/amputator/
            text = text.replace(/&(?!#?[xX]?(?:[0-9a-fA-F]+|\w+);)/g,"&amp;");
            
            // Encode naked <'s
            text = text.replace(/<(?![a-z\/?\$!])/gi,"&lt;");
            
            return text;
    }
    
    
    var _EncodeBackslashEscapes = function(text) {
    //
    //   Parameter:  String.
    //   Returns:       The string, with after processing the following backslash
    //                     escape sequences.
    //
    
            // attacklab: The polite way to do this is with the new
            // escapeCharacters() function:
            //
            //  text = escapeCharacters(text,"\\",true);
            //  text = escapeCharacters(text,"`*_{}[]()>#+-.!",true);
            //
            // ...but we're sidestepping its use of the (slow) RegExp constructor
            // as an optimization for Firefox.  This function gets called a LOT.
    
            text = text.replace(/\\(\\)/g,escapeCharacters_callback);
            text = text.replace(/\\([`*_{}\[\]()>#+-.!])/g,escapeCharacters_callback);
            return text;
    }
    
    
    var _DoAutoLinks = function(text) {
    
            text = text.replace(/<((https?|ftp|dict):[^'">\s]+)>/gi,"<a href=\"$1\">$1</a>");
    
            // Email addresses: <address@domain.foo>
    
            /*
                    text = text.replace(/
                            <
                            (?:mailto:)?
                            (
                                    [-.\w]+
                                    \@
                                    [-a-z0-9]+(\.[-a-z0-9]+)*\.[a-z]+
                            )
                            >
                    /gi, _DoAutoLinks_callback());
            */
            text = text.replace(/<(?:mailto:)?([-.\w]+\@[-a-z0-9]+(\.[-a-z0-9]+)*\.[a-z]+)>/gi,
                    function(wholeMatch,m1) {
                            return _EncodeEmailAddress( _UnescapeSpecialChars(m1) );
                    }
            );
    
            return text;
    }
    
    
    var _EncodeEmailAddress = function(addr) {
    //
    //  Input: an email address, e.g. "foo@example.com"
    //
    //  Output: the email address as a mailto link, with each character
    //  of the address encoded as either a decimal or hex entity, in
    //  the hopes of foiling most address harvesting spam bots. E.g.:
    //
    //  <a href="&#x6D;&#97;&#105;&#108;&#x74;&#111;:&#102;&#111;&#111;&#64;&#101;
    //     x&#x61;&#109;&#x70;&#108;&#x65;&#x2E;&#99;&#111;&#109;">&#102;&#111;&#111;
    //     &#64;&#101;x&#x61;&#109;&#x70;&#108;&#x65;&#x2E;&#99;&#111;&#109;</a>
    //
    //  Based on a filter by Matthew Wickline, posted to the BBEdit-Talk
    //  mailing list: <http://tinyurl.com/yu7ue>
    //
    
            // attacklab: why can't javascript speak hex?
            function char2hex(ch) {
                    var hexDigits = '0123456789ABCDEF';
                    var dec = ch.charCodeAt(0);
                    return(hexDigits.charAt(dec>>4) + hexDigits.charAt(dec&15));
            }
    
            var encode = [
                    function(ch){return "&#"+ch.charCodeAt(0)+";";},
                    function(ch){return "&#x"+char2hex(ch)+";";},
                    function(ch){return ch;}
            ];
    
            addr = "mailto:" + addr;
    
            addr = addr.replace(/./g, function(ch) {
                    if (ch == "@") {
                            // this *must* be encoded. I insist.
                            ch = encode[Math.floor(Math.random()*2)](ch);
                    } else if (ch !=":") {
                            // leave ':' alone (to spot mailto: later)
                            var r = Math.random();
                            // roughly 10% raw, 45% hex, 45% dec
                            ch =  (
                                            r > .9  ?   encode[2](ch)   :
                                            r > .45 ?   encode[1](ch)   :
                                                                    encode[0](ch)
                                    );
                    }
                    return ch;
            });
    
            addr = "<a href=\"" + addr + "\">" + addr + "</a>";
            addr = addr.replace(/">.+:/g,"\">"); // strip the mailto: from the visible part
    
            return addr;
    }
    
    
    var _UnescapeSpecialChars = function(text) {
    //
    // Swap back in all the special characters we've hidden.
    //
            text = text.replace(/~E(\d+)E/g,
                    function(wholeMatch,m1) {
                            var charCodeToReplace = parseInt(m1);
                            return String.fromCharCode(charCodeToReplace);
                    }
            );
            return text;
    }
    
    
    var _Outdent = function(text) {
    //
    // Remove one level of line-leading tabs or spaces
    //
    
            // attacklab: hack around Konqueror 3.5.4 bug:
            // "----------bug".replace(/^-/g,"") == "bug"
    
            text = text.replace(/^(\t|[ ]{1,4})/gm,"~0"); // attacklab: g_tab_width
    
            // attacklab: clean up hack
            text = text.replace(/~0/g,"");
    
            return text;
    }
    
    var _Detab = function(text) {
    // attacklab: Detab's completely rewritten for speed.
    // In perl we could fix it by anchoring the regexp with \G.
    // In javascript we're less fortunate.
    
            // expand first n-1 tabs
            text = text.replace(/\t(?=\t)/g,"    "); // attacklab: g_tab_width
    
            // replace the nth with two sentinels
            text = text.replace(/\t/g,"~A~B");
    
            // use the sentinel to anchor our regex so it doesn't explode
            text = text.replace(/~B(.+?)~A/g,
                    function(wholeMatch,m1,m2) {
                            var leadingText = m1;
                            var numSpaces = 4 - leadingText.length % 4;  // attacklab: g_tab_width
    
                            // there *must* be a better way to do this:
                            for (var i=0; i<numSpaces; i++) leadingText+=" ";
    
                            return leadingText;
                    }
            );
    
            // clean up sentinels
            text = text.replace(/~A/g,"    ");  // attacklab: g_tab_width
            text = text.replace(/~B/g,"");
    
            return text;
    }
    
    
    //
    //  attacklab: Utility functions
    //
    
    
    var escapeCharacters = function(text, charsToEscape, afterBackslash) {
            // First we have to escape the escape characters so that
            // we can build a character class out of them
            var regexString = "([" + charsToEscape.replace(/([\[\]\\])/g,"\\$1") + "])";
    
            if (afterBackslash) {
                    regexString = "\\\\" + regexString;
            }
    
            var regex = new RegExp(regexString,"g");
            text = text.replace(regex,escapeCharacters_callback);
    
            return text;
    }
    
    
    var escapeCharacters_callback = function(wholeMatch,m1) {
            var charCodeToEscape = m1.charCodeAt(0);
            return "~E"+charCodeToEscape+"E";
    }

} // end of Showdown.converter

// export
//if (typeof exports != 'undefined') exports.Showdown = Showdown;