<?php
/**
 * CodeIgniter Markdown
 *
 * Parses Mardown formatted text to HTML. A modified version of Michel Fortin's
 * PHP Markdown.
 *
 * @package     CodeIgniter
 * @subpackage  Libraries
 * @category    Libraries
 * @copyright   PHP Markdown Copyright (c) 2004-2015 Michel Fortin
 *              (https://michelf.ca/projects/php-markdown/)
 * @copyright   Markdown Copyright (c) 2004-2006 John Gruber
 *              (https://daringfireball.net/projects/markdown/)
 * @license     MIT License (http://opensource.org/licenses/MIT)
 * @author      Jon LaBelle
 * @link        https://github.com/jonlabelle/ci-markdown
 * @version     1.3.4
 */
defined('BASEPATH') or exit('No direct script access allowed');

class Markdown
{

    /**
     * Regex to match balanced brackets `[]`.
     *
     * Needed to insert a maximum bracket depth while converting to PHP.
     *
     * @var integer
     */
    protected $nested_brackets_depth = 6;

    /**
     * Nested brackets
     *
     * @var regex
     */
    protected $nested_brackets_re;

    /**
     * Nested url parenthesis depth
     *
     * @var integer
     */
    protected $nested_url_parenthesis_depth = 4;

    /**
     * Nested url parenthesis
     *
     * @var string
     */
    protected $nested_url_parenthesis_re;

    /**
     * Table of hash values for escaped characters
     *
     * @var string
     */
    protected $escape_chars = '\`*_{}[]()>#+-.!:|';

    /**
     * Escape chars.
     *
     * @var string
     */
    protected $escape_chars_re;

    /**
     * Change to ">" for HTML output.
     *
     * @var string
     */
    protected $empty_element_suffix = ">";

    /**
     * Tab width.
     *
     * @var integer
     */
    protected $tab_width = 2;

    /**
     * Change to `true` to disallow markup.
     *
     * @var boolean
     */
    protected $no_markup = false;

    /**
     * Change to `true` to disallow entities.
     *
     * @var boolean
     */
    protected $no_entities = false;

    /**
     * Predefined url's.
     *
     * @var array
     */
    protected $predef_urls = array();

    /**
     * Predefined titles.
     *
     * @var array
     */
    protected $predef_titles = array();

    /**
     * Optional filter function for URL's.
     *
     * @var function
     */
    public $url_filter_func = null;

    /**
     * Internal hashes used during transformation.
     *
     * @var array
     */
    protected $urls = array();

    /**
     * Internal hashes used during transformation.
     *
     * @var array
     */
    protected $titles = array();

    /**
     * Internal hashes used during transformation.
     *
     * @var array
     */
    protected $html_hashes = array();

    /**
     * Status flag to avoid invalid nesting.
     *
     * @var boolean
     */
    protected $in_anchor = false;

    /**
     * These are all the transformations that form block-level. Tags like
     * paragraphs, headers, and list items.
     *
     * @var array
     */
    protected $block_gamut = array(
        "doHeaders"          => 10,
        "doHorizontalRules"  => 20,
        "doLists"            => 40,
        "doCodeBlocks"       => 50,
        "doBlockQuotes"      => 60,
        "doFencedCodeBlocks" => 5,
        "doTables"           => 15,
        "doDefLists"         => 45,
    );

    /**
     * Strip link definitions, store in hashes.
     *
     * @var array
     */
    protected $document_gamut = array(
        "stripLinkDefinitions" => 20,
        "runBasicBlockGamut"   => 30,
        "doFencedCodeBlocks"   => 5,
        "stripFootnotes"       => 15,
        "stripAbbreviations"   => 25,
        "appendFootnotes"      => 50,
    );

    /**
     * These are all the transformations that occur *within* block-level tags
     * like paragraphs, headers, and list items.
     *
     * @var array
     */
    protected $span_gamut = array(
        "parseSpan"           => -30,
        "doImages"            =>  10,
        "doAnchors"           =>  20,
        "doAutoLinks"         =>  30,
        "encodeAmpsAndAngles" =>  40,
        "doItalicsAndBold"    =>  50,
        "doHardBreaks"        =>  60,
        "doFootnotes"         => 5,
        "doAbbreviations"     => 70,
    );

    /**
     * List level depth.
     *
     * @var integer
     */
    protected $list_level = 0;

    /**
     * Emphasis regex list.
     *
     * @var array
     */
    protected $em_relist = array(
        ''  => '(?:(?<!\*)\*(?!\*)|(?<![a-zA-Z0-9_])_(?!_))(?![\.,:;]?\s)',
        '*' => '(?<![\s*])\*(?!\*)',
        '_' => '(?<![\s_])_(?![a-zA-Z0-9_])',
    );

    /**
     * Strong regex list.
     *
     * @var array
     */
    protected $strong_relist = array(
        ''   => '(?:(?<!\*)\*\*(?!\*)|(?<![a-zA-Z0-9_])__(?!_))(?![\.,:;]?\s)',
        '**' => '(?<![\s*])\*\*(?!\*)',
        '__' => '(?<![\s_])__(?![a-zA-Z0-9_])',
    );

    /**
     * Strong and emphasized regex list.
     *
     * @var array
     */
    protected $em_strong_relist = array(
        ''    => '(?:(?<!\*)\*\*\*(?!\*)|(?<![a-zA-Z0-9_])___(?!_))(?![\.,:;]?\s)',
        '***' => '(?<![\s*])\*\*\*(?!\*)',
        '___' => '(?<![\s_])___(?![a-zA-Z0-9_])',
    );

    /**
     * Strong and emphasized prepared regex list.
     *
     * @var array
     */
    protected $em_strong_prepared_relist;

    /**
     * String length function for detab. `_initDetab` will create a function to
     * handle UTF-8 if the default function does not exist.
     *
     * @var string
     */
    protected $utf8_strlen = 'mb_strlen';

    /**
     * Prefix for footnote ids.
     *
     * @var string
     */
    public $fn_id_prefix = "";

    /**
     * Optional title attribute for footnote links and backlinks.
     *
     * @var string
     */
    public $fn_link_title = "";

    /**
     * Optional title attribute for footnote links and backlinks.
     *
     * @var string
     */
    public $fn_backlink_title = "";

    /**
     * Optional class attribute for footnote links and backlinks.
     *
     * @var string
     */
    public $fn_link_class = "footnote-ref";

    /**
     * Optional class attribute for footnote links and backlinks.
     *
     * @var string
     */
    public $fn_backlink_class = "footnote-backref";

    /**
     * Class name for table cell alignment (%% replaced left/center/right) For
     * instance: 'go-%%' becomes 'go-left' or 'go-right' or 'go-center' If
     * empty, the align attribute is used instead of a class name.
     *
     * @var string
     */
    public $table_align_class_tmpl = '';

    /**
     * Optional class prefix for fenced code block.
     *
     * @var string
     */
    public $code_class_prefix = "";

    /**
     * Class attribute for code blocks goes on the `code` tag; setting this to
     * true will put attributes on the `pre` tag instead.
     *
     * @var boolean
     */
    public $code_attr_on_pre = false;

    /**
     * Predefined abbreviations.
     *
     * @var array
     */
    public $predef_abbr = array();

    /**
     * Extra variables used during extra transformations.
     *
     * @var array
     */
    protected $footnotes = array();

    /**
     * Extra variables used during extra transformations.
     *
     * @var array
     */
    protected $footnotes_ordered = array();

    /**
     * Extra variables used during extra transformations.
     *
     * @var array
     */
    protected $footnotes_ref_count = array();

    /**
     * Extra variables used during extra transformations.
     *
     * @var array
     */
    protected $footnotes_numbers = array();

    /**
     * Extra variables used during extra transformations.
     *
     * @var array
     */
    protected $abbr_desciptions = array();

    /**
     * Extra variables used during extra transformations.
     *
     * @var array
     */
    protected $abbr_word_re = '';

    /**
     * Give the current footnote number.
     *
     * @var integer
     */
    protected $footnote_counter = 1;

    /**
     * Expression to use to catch attributes (includes the braces).
     *
     * @var string
     */
    protected $id_class_attr_catch_re = '\{((?:[ ]*[#.a-z][-_:a-zA-Z0-9=]+){1,})[ ]*\}';

    /**
     * Expression to use when parsing in a context when no capture is desired.
     *
     * @var string
     */
    protected $id_class_attr_nocatch_re = '\{(?:[ ]*[#.a-z][-_:a-zA-Z0-9=]+){1,}[ ]*\}';

    /**
     * Tags that are always treated as block tags.
     *
     * @var string
     */
    protected $block_tags_re = 'p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|address|form|fieldset|iframe|hr|legend|article|section|nav|aside|hgroup|header|footer|figcaption|figure';

    /**
     * Tags treated as block tags only if the opening tag is alone on its line.
     *
     * @var string
     */
    protected $context_block_tags_re = 'script|noscript|style|ins|del|iframe|object|source|track|param|math|svg|canvas|audio|video';

    /**
     * Tags where markdown="1" default to span mode.
     *
     * @var string
     */
    protected $contain_span_tags_re = 'p|h[1-6]|li|dd|dt|td|th|legend|address';

    /**
     * Tags which must not have their contents modified, no matter where they
     * appear.
     *
     * @var string
     */
    protected $clean_tags_re = 'script|style|math|svg';

    /**
     * Tags that do not need to be closed.
     *
     * @var string
     */
    protected $auto_close_tags_re = 'hr|img|param|source|track';

    /**
     * Optional header id="" generation callback function.
     *
     * @var function
     */
    public $header_id_func = null;

    /**
     * Optional function for converting code block content to HTML.
     *
     * @var function
     */
    public $code_block_content_func = null;

    /**
     * Enhanced ordered List
     *
     * Class attribute to toggle "enhanced ordered list" behaviour setting this
     * to true will allow ordered lists to start from the index number that is
     * defined first.
     *
     * For example:
     *
     *     2. List item two
     *     3. List item three
     *
     * becomes...
     *
     *     <ol start="2">
     *         <li>List item two</li>
     *         <li>List item three</li>
     *     </ol>
     *
     * @var boolean
     */
    public $enhanced_ordered_list = false;

    /**
     * ctor
     */
    public function __construct()
    {
        $this->_initDetab();

        $this->prepareItalicsAndBold();

        $this->nested_brackets_re =
            str_repeat('(?>[^\[\]]+|\[', $this->nested_brackets_depth).
            str_repeat('\])*', $this->nested_brackets_depth);

        $this->nested_url_parenthesis_re =
            str_repeat('(?>[^()\s]+|\(', $this->nested_url_parenthesis_depth).
            str_repeat('(?>\)))*', $this->nested_url_parenthesis_depth);

        $this->escape_chars_re = '['.preg_quote($this->escape_chars).']';

        // Sort document, block, and span gamut in ascendent priority order.
        asort($this->document_gamut);
        asort($this->block_gamut);
        asort($this->span_gamut);

        $this->enhanced_ordered_list = true;

        log_message('info', 'Markdown Class Initialized');
    }

    /**
     * Parses the markdown text to HTML.
     *
     * @param  string $text The markdown formatted text.
     * @return string The HTML formatted markdown.
     */
    public function parse($text)
    {
        return $this->transform($text);
    }

    /**
     * Parses a markdown formatted file to HTML.
     *
     * @param  string $file Path of markdown file to parse.
     * @return mixed  The HTML text, or `false` if file does not exist.
     */
    public function parse_file($file)
    {
        if (file_exists($file) && is_readable($file)) {
            return $this->transform(@file_get_contents($file));
        }

        return false;
    }

    /**
     * Called before the transformation process starts to setup parser states.
     *
     * @return void
     */
    protected function setup()
    {
        // clear global hashes
        $this->urls                = $this->predef_urls;
        $this->titles              = $this->predef_titles;
        $this->html_hashes         = array();
        $this->in_anchor           = false;

        // extra
        $this->footnotes           = array();
        $this->footnotes_ordered   = array();
        $this->footnotes_ref_count = array();
        $this->footnotes_numbers   = array();
        $this->abbr_desciptions    = array();
        $this->abbr_word_re        = '';
        $this->footnote_counter    = 1;

        foreach ($this->predef_abbr as $abbr_word => $abbr_desc) {
            if ($this->abbr_word_re) {
                $this->abbr_word_re .= '|';
            }

            $this->abbr_word_re .= preg_quote($abbr_word);
            $this->abbr_desciptions[$abbr_word] = trim($abbr_desc);
        }
    }

    /**
     * Called after the transformation process to clear any variable which may
     * be taking up memory unnecessarily.
     *
     * @return void
     */
    protected function teardown()
    {
        // Clearing Extra-specific variables.
        $this->footnotes           = array();
        $this->footnotes_ordered   = array();
        $this->footnotes_ref_count = array();
        $this->footnotes_numbers   = array();
        $this->abbr_desciptions    = array();
        $this->abbr_word_re        = '';

        $this->urls                = array();
        $this->titles              = array();
        $this->html_hashes         = array();
    }

    /**
     * Main function.
     *
     * Performs some preprocessing on the input text and pass it through the
     * document gamut.
     *
     * @param  string $text
     * @return string
     */
    protected function transform($text)
    {
        $this->setup();

        // Remove UTF-8 BOM and marker character in input, if present.
        $text = preg_replace('{^\xEF\xBB\xBF|\x1A}', '', $text);

        // Standardize line endings: dos to unix and mac to unix.
        $text = preg_replace('{\r\n?}', "\n", $text);

        // Make sure $text ends with a couple of newlines:
        $text .= "\n\n";

        // Convert all tabs to spaces.
        $text = $this->detab($text);

        // Turn block-level HTML blocks into hash entries
        $text = $this->hashHTMLBlocks($text);

        // Strip any lines consisting only of spaces and tabs. This makes
        // subsequent regex easier to write, because we can match consecutive
        // blank lines with /\n+/ instead of something contorted like /[ ]*\n+/
        $text = preg_replace('/^[ ]+$/m', '', $text);

        // run document gamut methods
        foreach ($this->document_gamut as $method => $priority) {
            $text = $this->$method($text);
        }

        $this->teardown();

        return $text."\n";
    }

    /**
     * Strips link definitions from text, stores the URLs and titles in hash
     * references.
     *
     * @param  string $text
     * @return string
     */
    protected function stripLinkDefinitions($text)
    {
        // Strips link definitions from text, stores the URLs and titles in hash
        // references.
        $less_than_tab = $this->tab_width - 1;

        // Link defs are in the form: ^[id]: url "optional title"
        $text = preg_replace_callback('{
                            ^[ ]{0,'.$less_than_tab.'}\[(.+)\][ ]?: # id = $1
                              [ ]*
                              \n?               # maybe *one* newline
                              [ ]*
                            (?:
                              <(.+?)>           # url = $2
                            |
                              (\S+?)            # url = $3
                            )
                              [ ]*
                              \n?               # maybe one newline
                              [ ]*
                            (?:
                                (?<=\s)         # lookbehind for whitespace
                                ["(]
                                (.*?)           # title = $4
                                [")]
                                [ ]*
                            )?  # title is optional
                    (?:[ ]* '.$this->id_class_attr_catch_re.' )?  # $5 = extra id & class attr
                            (?:\n+|\Z)
            }xm',
            array($this, '_stripLinkDefinitions_callback'),
            $text);

        return $text;
    }

    /**
     * Strips link definitions callback.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _stripLinkDefinitions_callback($matches)
    {
        $link_id = strtolower($matches[1]);
        $url = $matches[2] == '' ? $matches[3] : $matches[2];
        $this->urls[$link_id] = $url;
        $this->titles[$link_id] = & $matches[4];
        $this->ref_attr[$link_id] = $this->doExtraAttributes("", $dummy = & $matches[5]);

        return ''; // String that will replace the block
    }

    /**
     * Hashify HTML Blocks and "clean tags".
     *
     * 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.
     *
     * This works by calling _HashHTMLBlocks_InMarkdown, which then calls
     * _HashHTMLBlocks_InHTML when it encounter block tags. When the
     * markdown="1" attribute is found within a tag, _HashHTMLBlocks_InHTML
     * calls back _HashHTMLBlocks_InMarkdown to handle the Markdown syntax
     * within the tag. These two functions are calling each other. It's
     * recursive!
     *
     * @param  string $text
     * @return string
     */
    protected function hashHTMLBlocks($text)
    {
        if ($this->no_markup) {
            return $text;
        }

        // Call the HTML-in-Markdown hasher.
        list($text, ) = $this->_hashHTMLBlocks_inMarkdown($text);

        return $text;
    }

    /**
     * Parse markdown text, calling _HashHTMLBlocks_InHTML for block tags.
     *
     * $indent is the number of space to be ignored when checking for code
     * blocks. This is important because if we don't take the indent into
     * account, something like this (which looks right) won't work as expected:
     *
     * <div>
     *   <div markdown="1">
     *     Hello World. <-- Is this a Markdown code block or text?
     *   </div>         <-- Is this a Markdown code block or a real tag?
     * <div>
     *
     * If you don't like this, just don't indent the tag on which you apply the
     * markdown="1" attribute.
     *
     * If $enclosing_tag_re is not empty, stops at the first unmatched closing
     * tag with that name. Nested tags supported.
     *
     * If $span is true, text inside must treated as span. So any double newline
     * will be replaced by a single newline so that it does not create
     * paragraphs.
     *
     * Returns an array of that form: (processed text, remaining text)
     *
     * @param  string  $text
     * @param  integer $indent
     * @param  string  $enclosing_tag_re
     * @param  boolean $span
     * @return array
     */
    protected function _hashHTMLBlocks_inMarkdown($text, $indent = 0, $enclosing_tag_re = '', $span = false)
    {
        if ($text === '') {
            return array('', '');
        }

        // Regex to check for the presense of newlines around a block tag.
        $newline_before_re = '/(?:^\n?|\n\n)*$/';
        $newline_after_re =
            '{
                ^                       # Start of text following the tag.
                (?>[ ]*<!--.*?-->)?     # Optional comment.
                [ ]*\n                  # Must be followed by newline.
            }xs';

        // Regex to match any tag.
        $block_tag_re =
            '{
                (                   # $2: Capture whole tag.
                    </?                 # Any opening or closing tag.
                        (?>             # Tag name.
                            '.$this->block_tags_re.'            |
                            '.$this->context_block_tags_re.'    |
                            '.$this->clean_tags_re.'            |
                            (?!\s)'.$enclosing_tag_re.'
                        )
                        (?:
                            (?=[\s"\'/a-zA-Z0-9])   # Allowed characters after tag name.
                            (?>
                                ".*?"       |   # Double quotes (can contain `>`)
                                \'.*?\'     |   # Single quotes (can contain `>`)
                                .+?             # Anything but quotes and `>`.
                            )*?
                        )?
                    >                   # End of tag.
                |
                    <!--    .*?     --> # HTML Comment
                |
                    <\?.*?\?> | <%.*?%> # Processing instruction
                |
                    <!\[CDATA\[.*?\]\]> # CData Block
                '.(!$span ? ' # If not in span.
                |
                    # Indented code block
                    (?: ^[ ]*\n | ^ | \n[ ]*\n )
                    [ ]{'.($indent + 4).'}[^\n]* \n
                    (?>
                        (?: [ ]{'.($indent + 4).'}[^\n]* | [ ]* ) \n
                    )*
                |
                    # Fenced code block marker
                    (?<= ^ | \n )
                    [ ]{0,'.($indent + 3).'}(?:~{3,}|`{3,})
                    [ ]*
                    (?: \.?[-_:a-zA-Z0-9]+ )? # standalone class name
                    [ ]*
                    (?: '.$this->id_class_attr_nocatch_re.' )? # extra attributes
                    [ ]*
                    (?= \n )
                ' : '').' # End (if not is span).
                |
                    # Code span marker
                    # Note, this regex needs to go after backtick fenced
                    # code blocks but it should also be kept outside of the
                    # "if not in span" condition adding backticks to the parser
                    `+
                )
            }xs';

        $depth = 0;        // Current depth inside the tag tree.
        $parsed = "";    // Parsed text that will be returned.

        //
        // Loop through every tag until we find the closing tag of the parent
        // or loop until reaching the end of text if no parent tag specified.
        //
        do {
            //
            // Split the text using the first $tag_match pattern found.
            // Text before  pattern will be first in the array, text after
            // pattern will be at the end, and between will be any catches made
            // by the pattern.
            //
            $parts = preg_split($block_tag_re, $text, 2,
                PREG_SPLIT_DELIM_CAPTURE);

            // If in Markdown span mode, add a empty-string span-level hash
            // after each newline to prevent triggering any block element.
            if ($span) {
                $void = $this->hashPart("", ':');
                $newline = "$void\n";
                $parts[0] = $void.str_replace("\n", $newline, $parts[0]).$void;
            }

            $parsed .= $parts[0]; // Text before current tag.

            // If end of $text has been reached. Stop loop.
            if (count($parts) < 3) {
                $text = "";
                break;
            }

            $tag  = $parts[1]; // Tag to handle.
            $text = $parts[2]; // Remaining text after current tag.
            $tag_re = preg_quote($tag); // For use in a regular expression.

            //
            // Check for: Fenced code block marker.
            // Note: need to recheck the whole tag to disambiguate backtick
            // fences from code spans
            //
            if (preg_match('{^\n?([ ]{0,'.($indent + 3).'})(~{3,}|`{3,})[ ]*(?:\.?[-_:a-zA-Z0-9]+)?[ ]*(?:'.$this->id_class_attr_nocatch_re.')?[ ]*\n?$}', $tag, $capture)) {
                // Fenced code block marker: find matching end marker.
                $fence_indent = strlen($capture[1]); // use captured indent in re
                $fence_re = $capture[2]; // use captured fence in re
                if (preg_match('{^(?>.*\n)*?[ ]{'.($fence_indent).'}'.$fence_re.'[ ]*(?:\n|$)}', $text,
                        $matches)) {
                    // End marker found: pass text unchanged until marker.
                    $parsed .= $tag.$matches[0];
                    $text = substr($text, strlen($matches[0]));
                } else {
                    // No end marker: just skip it.
                    $parsed .= $tag;
                }
            }
            //
            // Check for: Indented code block.
            //
            elseif ($tag{0} == "\n" || $tag{0} == " ") {
                // Indented code block: pass it unchanged, will be handled
                // later.
                $parsed .= $tag;
            }
            //
            // Check for: Code span marker
            // Note: need to check this after backtick fenced code blocks
            //
            elseif ($tag{0} == "`") {
                // Find corresponding end marker.
                $tag_re = preg_quote($tag);
                if (preg_match('{^(?>.+?|\n(?!\n))*?(?<!`)'.$tag_re.'(?!`)}',
                        $text, $matches)) {
                    // End marker found: pass text unchanged until marker.
                    $parsed .= $tag.$matches[0];
                    $text = substr($text, strlen($matches[0]));
                } else {
                    // Unmatched marker: just skip it.
                    $parsed .= $tag;
                }
            }
            //
            // Check for: Opening Block level tag or
            //            Opening Context Block tag (like ins and del)
            //               used as a block tag (tag is alone on it's line).
            //
            elseif (preg_match('{^<(?:'.$this->block_tags_re.')\b}', $tag) ||
                (preg_match('{^<(?:'.$this->context_block_tags_re.')\b}', $tag) &&
                    preg_match($newline_before_re, $parsed) &&
                    preg_match($newline_after_re, $text))
            ) {
                // Need to parse tag and following text using the HTML parser.
                list($block_text, $text) =
                    $this->_hashHTMLBlocks_inHTML($tag.$text, "hashBlock", true);

                // Make sure it stays outside of any paragraph by adding newlines.
                $parsed .= "\n\n$block_text\n\n";
            }
            //
            // Check for: Clean tag (like script, math)
            //            HTML Comments, processing instructions.
            //
            elseif (preg_match('{^<(?:'.$this->clean_tags_re.')\b}', $tag) ||
                $tag{1} == '!' || $tag{1} == '?') {
                // Need to parse tag and following text using the HTML parser.
                // (don't check for markdown attribute)
                list($block_text, $text) =
                    $this->_hashHTMLBlocks_inHTML($tag.$text, "hashClean", false);

                $parsed .= $block_text;
            }
            //
            // Check for: Tag with same name as enclosing tag.
            //
            elseif ($enclosing_tag_re !== '' &&
                // Same name as enclosing tag.
                preg_match('{^</?(?:'.$enclosing_tag_re.')\b}', $tag)) {
                //
                // Increase/decrease nested tag count.
                //
                if ($tag{1} == '/') {
                    $depth--;
                } elseif ($tag{strlen($tag)-2} != '/') {
                    $depth++;
                }
                if ($depth < 0) {
                    //
                    // Going out of parent element. Clean up and break so we
                    // return to the calling function.
                    //
                    $text = $tag.$text;
                    break;
                }

                $parsed .= $tag;
            } else {
                $parsed .= $tag;
            }
        } while ($depth >= 0);

        return array($parsed, $text);
    }

    /**
     * Parse HTML, calling _HashHTMLBlocks_InMarkdown for block tags.
     *
     * - Calls $hash_method to convert any blocks.
     * - Stops when the first opening tag closes.
     * - $md_attr indicate if the use of the `markdown="1"` attribute is
     *   allowed. (it is not inside clean tags)
     *
     * @param  string $text
     * @param  string $hash_method
     * @param  string $md_attr
     * @return array  An array of that form: (processed text , remaining text)
     */
    protected function _hashHTMLBlocks_inHTML($text, $hash_method, $md_attr)
    {
        if ($text === '') {
            return array('', '');
        }

        // Regex to match `markdown` attribute inside of a tag.
        $markdown_attr_re = '
            {
                \s*         # Eat whitespace before the `markdown` attribute
                markdown
                \s*=\s*
                (?>
                    (["\'])     # $1: quote delimiter
                    (.*?)       # $2: attribute value
                    \1          # matching delimiter
                |
                    ([^\s>]*)   # $3: unquoted attribute value
                )
                ()              # $4: make $3 always defined (avoid warnings)
            }xs';

        // Regex to match any tag.
        $tag_re = '{
                (                   # $2: Capture whole tag.
                    </?                 # Any opening or closing tag.
                        [\w:$]+         # Tag name.
                        (?:
                            (?=[\s"\'/a-zA-Z0-9])   # Allowed characters after tag name.
                            (?>
                                ".*?"       |   # Double quotes (can contain `>`)
                                \'.*?\'     |   # Single quotes (can contain `>`)
                                .+?             # Anything but quotes and `>`.
                            )*?
                        )?
                    >                   # End of tag.
                |
                    <!--    .*?     --> # HTML Comment
                |
                    <\?.*?\?> | <%.*?%> # Processing instruction
                |
                    <!\[CDATA\[.*?\]\]> # CData Block
                )
            }xs';

        $original_text = $text;        // Save original text in case of faliure.

        $depth        = 0;    // Current depth inside the tag tree.
        $block_text    = "";    // Temporary text holder for current text.
        $parsed        = "";    // Parsed text that will be returned.

        //
        // Get the name of the starting tag.
        // (This pattern makes $base_tag_name_re safe without quoting.)
        //
        if (preg_match('/^<([\w:$]*)\b/', $text, $matches)) {
            $base_tag_name_re = $matches[1];
        }

        //
        // Loop through every tag until we find the corresponding closing tag.
        //
        do {
            //
            // Split the text using the first $tag_match pattern found.
            // Text before  pattern will be first in the array, text after
            // pattern will be at the end, and between will be any catches made
            // by the pattern.
            //
            $parts = preg_split($tag_re, $text, 2, PREG_SPLIT_DELIM_CAPTURE);

            if (count($parts) < 3) {
                //
                // End of $text reached with unbalenced tag(s).
                // In that case, we return original text unchanged and pass the
                // first character as filtered to prevent an infinite loop in the
                // parent function.
                //
                return array($original_text{0}, substr($original_text, 1));
            }

            $block_text .= $parts[0]; // Text before current tag.
            $tag         = $parts[1]; // Tag to handle.
            $text        = $parts[2]; // Remaining text after current tag.

            //
            // Check for: Auto-close tag (like <hr/>)
            //    Comments and Processing Instructions.
            //
            if (preg_match('{^</?(?:'.$this->auto_close_tags_re.')\b}', $tag) ||
                $tag{1} == '!' || $tag{1} == '?') {
                // Just add the tag to the block as if it was text.
                $block_text .= $tag;
            } else {
                //
                // Increase/decrease nested tag count. Only do so if
                // the tag's name match base tag's.
                //
                if (preg_match('{^</?'.$base_tag_name_re.'\b}', $tag)) {
                    if ($tag{1} == '/') {
                        $depth--;
                    } elseif ($tag{strlen($tag)-2} != '/') {
                        $depth++;
                    }
                }

                //
                // Check for `markdown="1"` attribute and handle it.
                //
                if ($md_attr &&
                    preg_match($markdown_attr_re, $tag, $attr_m) &&
                    preg_match('/^1|block|span$/', $attr_m[2].$attr_m[3])) {
                    // Remove `markdown` attribute from opening tag.
                    $tag = preg_replace($markdown_attr_re, '', $tag);

                    // Check if text inside this tag must be parsed in span mode.
                    $this->mode = $attr_m[2].$attr_m[3];
                    $span_mode = $this->mode == 'span' || $this->mode != 'block' &&
                        preg_match('{^<(?:'.$this->contain_span_tags_re.')\b}', $tag);

                    // Calculate indent before tag.
                    if (preg_match('/(?:^|\n)( *?)(?! ).*?$/', $block_text, $matches)) {
                        $strlen = $this->utf8_strlen;
                        $indent = $strlen($matches[1], 'UTF-8');
                    } else {
                        $indent = 0;
                    }

                    // End preceding block with this tag.
                    $block_text .= $tag;
                    $parsed .= $this->$hash_method($block_text);

                    // Get enclosing tag name for the ParseMarkdown function.
                    // (This pattern makes $tag_name_re safe without quoting.)
                    preg_match('/^<([\w:$]*)\b/', $tag, $matches);
                    $tag_name_re = $matches[1];

                    // Parse the content using the HTML-in-Markdown parser.
                    list($block_text, $text)
                        = $this->_hashHTMLBlocks_inMarkdown($text, $indent,
                        $tag_name_re, $span_mode);

                    // Outdent markdown text.
                    if ($indent > 0) {
                        $block_text = preg_replace("/^[ ]{1,$indent}/m", "",
                            $block_text);
                    }

                    // Append tag content to parsed text.
                    if (!$span_mode) {
                        $parsed .= "\n\n$block_text\n\n";
                    } else {
                        $parsed .= "$block_text";
                    }

                    // Start over with a new block.
                    $block_text = "";
                } else {
                    $block_text .= $tag;
                }
            }
        } while ($depth > 0);

        //
        // Hash last block text that wasn't processed inside the loop.
        //
        $parsed .= $this->$hash_method($block_text);

        return array($parsed, $text);
    }

    /**
     * Called whenever a tag must be hashed when a function insert an atomic
     * element in the text stream. Passing $text to through this function gives
     * a unique text-token which will be reverted back when calling unhash.
     *
     * The $boundary argument specify what character should be used to surround
     * the token. By convention, "B" is used for block elements that needs not
     * to be wrapped into paragraph tags at the end, ":" is used for elements
     * that are word separators and "X" is used in the general case.
     *
     * Swap back any tag hash found in $text so we do not have to `unhash`
     * multiple times at the end.
     *
     * @param  string $text
     * @param  string $boundary
     * @return string
     */
    protected function hashPart($text, $boundary = 'X')
    {
        // Swap back any tag hash found in $text so we do not have to `unhash`
        // multiple times at the end.
        $text = $this->unhash($text);

        // Then hash the block.
        static $i = 0;
        $key = "$boundary\x1A".++$i.$boundary;
        $this->html_hashes[$key] = $text;

        // String that will replace the tag.
        return $key;
    }

    /**
     * Shortcut function for hashPart with block-level boundaries.
     *
     * @param  string $text
     * @return string
     */
    protected function hashBlock($text)
    {
        return $this->hashPart($text, 'B');
    }

    /**
     * Called whenever a tag must be hashed when a function inserts a "clean"
     * tag in $text, it passes through this function and is automaticaly
     * escaped, blocking invalid nested overlap.
     *
     * @param  string $text
     * @return string
     */
    protected function hashClean($text)
    {
        return $this->hashPart($text, 'C');
    }

    /**
     * Block Gamut
     *
     * @param  string $text
     * @return string
     */
    protected function runBlockGamut($text)
    {
        $text = $this->hashHTMLBlocks($text);

        return $this->runBasicBlockGamut($text);
    }

    /**
     * Run block gamut transformations, without hashing HTML blocks.
     *
     * This is useful when HTML blocks are known to be already hashed, like in
     * the first whole-document pass.
     *
     * @param  string $text
     * @return string
     */
    protected function runBasicBlockGamut($text)
    {
        foreach ($this->block_gamut as $method => $priority) {
            $text = $this->$method($text);
        }

        // Finally form paragraph and restore hashed blocks.
        $text = $this->formParagraphs($text);

        return $text;
    }

    /**
     * Parse horizontal lines.
     *
     * @param  string $text
     * @return string
     */
    protected function doHorizontalRules($text)
    {
        return preg_replace(
            '{
                    ^[ ]{0,3} # Leading space
                    ([-*_])   # $1: First marker
                    (?>       # Repeated marker group
                    [ ]{0,2}  # Zero, one, or two spaces.
                    \1        # Marker character
                    ){2,}     # Group repeated at least twice
                    [ ]*      # Tailing spaces
                    $         # End of line.
                }mx',
            "\n".$this->hashBlock("<hr$this->empty_element_suffix")."\n",
            $text);
    }

    /**
     * Run span gamut
     *
     * @param  string $text
     * @return string
     */
    protected function runSpanGamut($text)
    {
        foreach ($this->span_gamut as $method => $priority) {
            $text = $this->$method($text);
        }

        return $text;
    }

    /**
     * Parse hard line breaks.
     *
     * @param  string $text
     * @return string
     */
    protected function doHardBreaks($text)
    {
        return preg_replace_callback('/ {2,}\n/',
            array($this, '_doHardBreaks_callback'), $text);
    }

    /**
     * Parse hard line breaks callback.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doHardBreaks_callback($matches)
    {
        return $this->hashPart("<br$this->empty_element_suffix\n");
    }

    /**
     * Turn Markdown link shortcuts into XHTML <a> tags.
     *
     * @param  string $text
     * @return string
     */
    protected function doAnchors($text)
    {
        //
        // Turn Markdown link shortcuts into XHTML <a> tags.
        //
        if ($this->in_anchor) {
            return $text;
        }
        $this->in_anchor = true;

        //
        // First, handle reference-style links: [link text] [id]
        //
        $text = preg_replace_callback('{
            (                   # wrap whole match in $1
              \[
                ('.$this->nested_brackets_re.') # link text = $2
              \]

              [ ]?              # one optional space
              (?:\n[ ]*)?       # one optional newline followed by spaces

              \[
                (.*?)       # id = $3
              \]
            )
            }xs',
            array($this, '_doAnchors_reference_callback'), $text);

        //
        // Next, inline-style links: [link text](url "optional title")
        //
        $text = preg_replace_callback('{
            (               # wrap whole match in $1
              \[
                ('.$this->nested_brackets_re.') # link text = $2
              \]
              \(            # literal paren
                [ \n]*
                (?:
                    <(.+?)> # href = $3
                |
                    ('.$this->nested_url_parenthesis_re.')  # href = $4
                )
                [ \n]*
                (           # $5
                  ([\'"])   # quote char = $6
                  (.*?)     # Title = $7
                  \6        # matching quote
                  [ \n]*    # ignore any spaces/tabs between closing quote and )
                )?          # title is optional
              \)
              (?:[ ]? '.$this->id_class_attr_catch_re.' )?   # $8 = id/class attributes
            )
            }xs',
            array($this, '_doAnchors_inline_callback'), $text);

        //
        // Last, handle reference-style shortcuts: [link text]
        // These must come last in case you've also got [link text][1]
        // or [link text](/foo)
        //
        $text = preg_replace_callback('{
            (                   # wrap whole match in $1
              \[
                ([^\[\]]+)      # link text = $2; can\'t contain [ or ]
              \]
            )
            }xs',
            array($this, '_doAnchors_reference_callback'), $text);

        $this->in_anchor = false;

        return $text;
    }

    /**
     * Markdown anchors callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doAnchors_reference_callback($matches)
    {
        $whole_match =  $matches[1];
        $link_text   =  $matches[2];
        $link_id     = & $matches[3];

        if ($link_id == "") {
            // for shortcut links like [this][] or [this].
            $link_id = $link_text;
        }

        // lower-case and turn embedded newlines into spaces
        $link_id = strtolower($link_id);
        $link_id = preg_replace('{[ ]?\n}', ' ', $link_id);

        if (isset($this->urls[$link_id])) {
            $url = $this->urls[$link_id];
            $url = $this->encodeURLAttribute($url);

            $result = "<a href=\"$url\"";
            if (isset($this->titles[$link_id])) {
                $title = $this->titles[$link_id];
                $title = $this->encodeAttribute($title);
                $result .=  " title=\"$title\"";
            }
            if (isset($this->ref_attr[$link_id])) {
                $result .= $this->ref_attr[$link_id];
            }

            $link_text = $this->runSpanGamut($link_text);
            $result .= ">$link_text</a>";
            $result = $this->hashPart($result);
        } else {
            $result = $whole_match;
        }

        return $result;
    }

    /**
     * Inline anchors callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doAnchors_inline_callback($matches)
    {
        $whole_match =  $matches[1];
        $link_text =  $this->runSpanGamut($matches[2]);
        $url =  $matches[3] == '' ? $matches[4] : $matches[3];
        $title = &$matches[7];
        $attr = $this->doExtraAttributes("a", $dummy = & $matches[8]);

        // if the URL was of the form <s p a c e s> it got caught by the HTML
        // tag parser and hashed. Need to reverse the process before using the
        // URL.
        $unhashed = $this->unhash($url);
        if ($unhashed != $url) {
            $url = preg_replace('/^<(.*)>$/', '\1', $unhashed);
        }

        $url = $this->encodeURLAttribute($url);

        $result = "<a href=\"$url\"";
        if (isset($title)) {
            $title = $this->encodeAttribute($title);
            $result .=  " title=\"$title\"";
        }
        $result .= $attr;

        $link_text = $this->runSpanGamut($link_text);
        $result .= ">$link_text</a>";

        return $this->hashPart($result);
    }

    /**
     * Turn Markdown image shortcuts into <img> tags.
     *
     * @param  string $text
     * @return string
     */
    protected function doImages($text)
    {
        $text = preg_replace_callback('{
            (               # wrap whole match in $1
              !\[
                ('.$this->nested_brackets_re.')     # alt text = $2
              \]

              [ ]?              # one optional space
              (?:\n[ ]*)?       # one optional newline followed by spaces

              \[
                (.*?)       # id = $3
              \]

            )
            }xs',
            array($this, '_doImages_reference_callback'), $text);

        //
        // Next, handle inline images:  ![alt text](url "optional title")
        // Don't forget: encode * and _
        //
        $text = preg_replace_callback('{
            (               # wrap whole match in $1
              !\[
                ('.$this->nested_brackets_re.')     # alt text = $2
              \]
              \s?           # One optional whitespace character
              \(            # literal paren
                [ \n]*
                (?:
                    <(\S*)> # src url = $3
                |
                    ('.$this->nested_url_parenthesis_re.')  # src url = $4
                )
                [ \n]*
                (           # $5
                  ([\'"])   # quote char = $6
                  (.*?)     # title = $7
                  \6        # matching quote
                  [ \n]*
                )?          # title is optional
              \)
              (?:[ ]? '.$this->id_class_attr_catch_re.' )?   # $8 = id/class attributes
            )
            }xs',
            array($this, '_doImages_inline_callback'), $text);

        return $text;
    }

    /**
     * Images callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doImages_reference_callback($matches)
    {
        $whole_match = $matches[1];
        $alt_text = $matches[2];
        $link_id = strtolower($matches[3]);

        if ($link_id == "") {
            $link_id = strtolower($alt_text); // for shortcut links like ![this][].
        }

        $alt_text = $this->encodeAttribute($alt_text);
        if (isset($this->urls[$link_id])) {
            $url = $this->encodeURLAttribute($this->urls[$link_id]);
            $result = "<img src=\"$url\" alt=\"$alt_text\"";
            if (isset($this->titles[$link_id])) {
                $title = $this->titles[$link_id];
                $title = $this->encodeAttribute($title);
                $result .=  " title=\"$title\"";
            }
            if (isset($this->ref_attr[$link_id])) {
                $result .= $this->ref_attr[$link_id];
            }
            $result .= $this->empty_element_suffix;
            $result = $this->hashPart($result);
        } else {
            // If there's no such link ID, leave intact:
            $result = $whole_match;
        }

        return $result;
    }

    /**
     * Inline images callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doImages_inline_callback($matches)
    {
        $whole_match = $matches[1];
        $alt_text = $matches[2];
        $url = $matches[3] == '' ? $matches[4] : $matches[3];
        $title = &$matches[7];
        $attr = $this->doExtraAttributes("img", $dummy = & $matches[8]);

        $alt_text = $this->encodeAttribute($alt_text);
        $url = $this->encodeURLAttribute($url);
        $result = "<img src=\"$url\" alt=\"$alt_text\"";

        if (isset($title)) {
            $title = $this->encodeAttribute($title);
            $result .=  " title=\"$title\""; // $title already quoted
        }

        $result .= $attr;
        $result .= $this->empty_element_suffix;

        return $this->hashPart($result);
    }

    /**
     * Process headers.
     *
     * @param  string $text
     * @return string
     */
    protected function doHeaders($text)
    {
        //
        // Redefined to add id and class attribute support.
        //
        // Setext-style headers:
        //   Header 1  {#header1}
        //   ========
        //
        //   Header 2  {#header2 .class1 .class2}
        //   --------
        //
        $text = preg_replace_callback(
            '{
                (^.+?)                              # $1: Header text
                (?:[ ]+ '.$this->id_class_attr_catch_re.' )?     # $3 = id/class attributes
                [ ]*\n(=+|-+)[ ]*\n+                # $3: Header footer
            }mx',
            array($this, '_doHeaders_callback_setext'), $text);

        // atx-style headers:
        // # Header 1        {#header1}
        // ## Header 2       {#header2}
        // ## Header 2 with closing hashes ##  {#header3.class1.class2}
        // ...
        // ###### Header 6   {.class2}
        //
        $text = preg_replace_callback('{
                ^(\#{1,6})  # $1 = string of #\'s
                [ ]*
                (.+?)       # $2 = Header text
                [ ]*
                \#*         # optional closing #\'s (not counted)
                (?:[ ]+ '.$this->id_class_attr_catch_re.' )?     # $3 = id/class attributes
                [ ]*
                \n+
            }xm',
            array($this, '_doHeaders_callback_atx'), $text);

        return $text;
    }

    /**
     * Process headers callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doHeaders_callback_setext($matches)
    {
        if ($matches[3] == '-' && preg_match('{^- }', $matches[1])) {
            return $matches[0];
        }

        $level = $matches[3]{0}
        == '=' ? 1 : 2;

        $defaultId = is_callable($this->header_id_func) ? call_user_func($this->header_id_func, $matches[1]) : null;

        $attr  = $this->doExtraAttributes("h$level", $dummy = & $matches[2], $defaultId);
        $block = "<h$level$attr>".$this->runSpanGamut($matches[1])."</h$level>";

        return "\n".$this->hashBlock($block)."\n\n";
    }

    /**
     * Headers atx callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doHeaders_callback_atx($matches)
    {
        $level = strlen($matches[1]);

        $defaultId = is_callable($this->header_id_func) ? call_user_func($this->header_id_func, $matches[2]) : null;
        $attr  = $this->doExtraAttributes("h$level", $dummy = & $matches[3], $defaultId);
        $block = "<h$level$attr>".$this->runSpanGamut($matches[2])."</h$level>";

        return "\n".$this->hashBlock($block)."\n\n";
    }

    /**
     * Generate ID from Header Value
     *
     * If a header_id_func property is set, we can use it to automatically
     * generate an id attribute.
     *
     * @param string $headerValue
     *
     * @return string
     */
    protected function _generateIdFromHeaderValue($headerValue)
    {
        // This method returns a string in the form id="foo", or an empty string
        // otherwise.
        if (!is_callable($this->header_id_func)) {
            return "";
        }

        $idValue = call_user_func($this->header_id_func, $headerValue);
        if (!$idValue) {
            return "";
        }

        return ' id="' . $this->encodeAttribute($idValue) . '"';
    }



    /**
     * Process HTML tables.
     *
     * @param  string $text
     * @return string
     */
    protected function doTables($text)
    {
        $less_than_tab = $this->tab_width - 1;

        // Find tables with leading pipe.
        //
        // | Header 1 | Header 2
        // | -------- | --------
        // | Cell 1   | Cell 2
        // | Cell 3   | Cell 4
        //
        $text = preg_replace_callback('
            {
                ^                           # Start of a line
                [ ]{0,'.$less_than_tab.'}   # Allowed whitespace.
                [|]                         # Optional leading pipe (present)
                (.+) \n                     # $1: Header row (at least one pipe)

                [ ]{0,'.$less_than_tab.'}   # Allowed whitespace.
                [|] ([ ]*[-:]+[-| :]*) \n   # $2: Header underline

                (                           # $3: Cells
                    (?>
                        [ ]*                # Allowed whitespace.
                        [|] .* \n           # Row content.
                    )*
                )
                (?=\n|\Z)                   # Stop at final double newline.
            }xm',
            array($this, '_doTable_leadingPipe_callback'), $text);

        // Find tables without leading pipe.
        //
        // Header 1 | Header 2
        // -------- | --------
        // Cell 1   | Cell 2
        // Cell 3   | Cell 4
        //
        $text = preg_replace_callback('
            {
                ^                           # Start of a line
                [ ]{0,'.$less_than_tab.'}   # Allowed whitespace.
                (\S.*[|].*) \n              # $1: Header row (at least one pipe)

                [ ]{0,'.$less_than_tab.'}   # Allowed whitespace.
                ([-:]+[ ]*[|][-| :]*) \n    # $2: Header underline

                (                           # $3: Cells
                    (?>
                        .* [|] .* \n        # Row content
                    )*
                )
                (?=\n|\Z)                   # Stop at final double newline.
            }xm',
            array($this, '_DoTable_callback'), $text);

        return $text;
    }

    /**
     * Table leading pipe callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doTable_leadingPipe_callback($matches)
    {
        $head      = $matches[1];
        $underline = $matches[2];
        $content   = $matches[3];

        // Remove leading pipe for each row.
        $content    = preg_replace('/^ *[|]/m', '', $content);

        return $this->_doTable_callback(array($matches[0], $head, $underline, $content));
    }

    /**
     * Handle table align attr.
     *
     * @param  string $alignname
     * @return string
     */
    protected function _doTable_makeAlignAttr($alignname)
    {
        if (empty($this->table_align_class_tmpl)) {
            return " align=\"$alignname\"";
        }

        $classname = str_replace('%%', $alignname, $this->table_align_class_tmpl);

        return " class=\"$classname\"";
    }

    /**
     * Table callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doTable_callback($matches)
    {
        $head      = $matches[1];
        $underline = $matches[2];
        $content   = $matches[3];

        // Remove any tailing pipes for each line.
        $head      = preg_replace('/[|] *$/m', '', $head);
        $underline = preg_replace('/[|] *$/m', '', $underline);
        $content   = preg_replace('/[|] *$/m', '', $content);

        // Reading alignement from header underline.
        $separators    = preg_split('/ *[|] */', $underline);
        foreach ($separators as $n => $s) {
            if (preg_match('/^ *-+: *$/', $s)) {
                $attr[$n] = $this->_doTable_makeAlignAttr('right');
            } elseif (preg_match('/^ *:-+: *$/', $s)) {
                $attr[$n] = $this->_doTable_makeAlignAttr('center');
            } elseif (preg_match('/^ *:-+ *$/', $s)) {
                $attr[$n] = $this->_doTable_makeAlignAttr('left');
            } else {
                $attr[$n] = '';
            }
        }

        // Parsing span elements, including code spans, character escapes,
        // and inline HTML tags, so that pipes inside those gets ignored.
        $head        = $this->parseSpan($head);
        $headers    = preg_split('/ *[|] */', $head);
        $col_count    = count($headers);
        $attr       = array_pad($attr, $col_count, '');

        // Write column headers.
        $text = "<table>\n";
        $text .= "<thead>\n";
        $text .= "<tr>\n";
        foreach ($headers as $n => $header) {
            $text .= "  <th$attr[$n]>".$this->runSpanGamut(trim($header))."</th>\n";
        }
        $text .= "</tr>\n";
        $text .= "</thead>\n";

        // Split content by row.
        $rows = explode("\n", trim($content, "\n"));

        $text .= "<tbody>\n";
        foreach ($rows as $row) {
            // Parsing span elements, including code spans, character escapes,
            // and inline HTML tags, so that pipes inside those gets ignored.
            $row = $this->parseSpan($row);

            // Split row by cell.
            $row_cells = preg_split('/ *[|] */', $row, $col_count);
            $row_cells = array_pad($row_cells, $col_count, '');

            $text .= "<tr>\n";
            foreach ($row_cells as $n => $cell) {
                $text .= "  <td$attr[$n]>".$this->runSpanGamut(trim($cell))."</td>\n";
            }
            $text .= "</tr>\n";
        }
        $text .= "</tbody>\n";
        $text .= "</table>";

        return $this->hashBlock($text)."\n";
    }

    /**
     * Process definition lists.
     *
     * @param  string $text
     * @return string
     */
    protected function doDefLists($text)
    {
        // Form HTML definition lists.
        $less_than_tab = $this->tab_width - 1;

        // Re-usable pattern to match any entire dl list:
        $whole_list_re = '(?>
            (                               # $1 = whole list
              (                             # $2
                [ ]{0,'.$less_than_tab.'}
                ((?>.*\S.*\n)+)             # $3 = defined term
                \n?
                [ ]{0,'.$less_than_tab.'}:[ ]+ # colon starting definition
              )
              (?s:.+?)
              (                             # $4
                  \z
                |
                  \n{2,}
                  (?=\S)
                  (?!                       # Negative lookahead for another term
                    [ ]{0,'.$less_than_tab.'}
                    (?: \S.*\n )+?          # defined term
                    \n?
                    [ ]{0,'.$less_than_tab.'}:[ ]+ # colon starting definition
                  )
                  (?!                       # Negative lookahead for another definition
                    [ ]{0,'.$less_than_tab.'}:[ ]+ # colon starting definition
                  )
              )
            )
        )'; // mx

        $text = preg_replace_callback('{
                (?>\A\n?|(?<=\n\n))
                '.$whole_list_re.'
            }mx',
            array($this, '_doDefLists_callback'), $text);

        return $text;
    }

    /**
     * Definition lists callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doDefLists_callback($matches)
    {
        // Re-usable patterns to match list item bullets and number markers:
        $list = $matches[1];

        // Turn double returns into triple returns, so that we can make a
        // paragraph for the last item in a list, if necessary:
        $result = trim($this->processDefListItems($list));
        $result = "<dl>\n".$result."\n</dl>";

        return $this->hashBlock($result)."\n\n";
    }

    /**
     * Process definition list items.
     *
     * @param  string $list_str
     * @return string
     */
    protected function processDefListItems($list_str)
    {
        //
        // Process the contents of a single definition list, splitting it
        // into individual term and definition list items.
        //
        $less_than_tab = $this->tab_width - 1;

        // trim trailing blank lines:
        $list_str = preg_replace("/\n{2,}\\z/", "\n", $list_str);

        // Process definition terms.
        $list_str = preg_replace_callback('{
            (?>\A\n?|\n\n+)                 # leading line
            (                               # definition terms = $1
                [ ]{0,'.$less_than_tab.'}   # leading whitespace
                (?!\:[ ]|[ ])               # negative lookahead for a definition
                                            #   mark (colon) or more whitespace.
                (?> \S.* \n)+?              # actual term (not whitespace).
            )
            (?=\n?[ ]{0,3}:[ ])             # lookahead for following line feed
                                            #   with a definition mark.
            }xm',
            array($this, '_processDefListItems_callback_dt'), $list_str);

        // Process actual definitions.
        $list_str = preg_replace_callback('{
            \n(\n+)?                        # leading line = $1
            (                               # marker space = $2
                [ ]{0,'.$less_than_tab.'}   # whitespace before colon
                \:[ ]+                      # definition mark (colon)
            )
            ((?s:.+?))                      # definition text = $3
            (?= \n+                         # stop at next definition mark,
                (?:                         # next term or end of text
                    [ ]{0,'.$less_than_tab.'} \:[ ] |
                    <dt> | \z
                )
            )
            }xm',
            array($this, '_processDefListItems_callback_dd'), $list_str);

        return $list_str;
    }

    /**
     * Process definition list dt items callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _processDefListItems_callback_dt($matches)
    {
        $terms = explode("\n", trim($matches[1]));
        $text = '';

        foreach ($terms as $term) {
            $term = $this->runSpanGamut(trim($term));
            $text .= "\n<dt>".$term."</dt>";
        }

        return $text."\n";
    }

    /**
     * Process definition list dd items callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _processDefListItems_callback_dd($matches)
    {
        $leading_line    = $matches[1];
        $marker_space    = $matches[2];
        $def            = $matches[3];

        if ($leading_line || preg_match('/\n{2,}/', $def)) {
            // Replace marker with the appropriate whitespace indentation
            $def = str_repeat(' ', strlen($marker_space)).$def;
            $def = $this->runBlockGamut($this->outdent($def."\n\n"));
            $def = "\n".$def."\n";
        } else {
            $def = rtrim($def);
            $def = $this->runSpanGamut($this->outdent($def));
        }

        return "\n<dd>".$def."</dd>\n";
    }

    /**
     * Adding the fenced code block syntax to regular Markdown.
     *
     *  ```
     *  var fn = function () {};
     *  ```
     *
     * @param  string $text
     * @return string
     */
    protected function doFencedCodeBlocks($text)
    {
        $less_than_tab = $this->tab_width;

        $text = preg_replace_callback('{
                (?:\n|\A)
                # 1: Opening marker
                (
                    (?:~{3,}|`{3,}) # 3 or more tildes/backticks.
                )
                [ ]*
                (?:
                    \.?([-_:a-zA-Z0-9]+) # 2: standalone class name
                )?
                [ ]*
                (?:
                    '.$this->id_class_attr_catch_re.' # 3: Extra attributes
                )?
                [ ]* \n # Whitespace and newline following marker.

                # 4: Content
                (
                    (?>
                        (?!\1 [ ]* \n)  # Not a closing marker.
                        .*\n+
                    )+
                )

                # Closing marker.
                \1 [ ]* (?= \n )
            }xm',
            array($this, '_doFencedCodeBlocks_callback'), $text);

        return $text;
    }

    /**
     * Fenced code block callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doFencedCodeBlocks_callback($matches)
    {
        $classname = &$matches[2];
        $attrs     = &$matches[3];
        $codeblock = $matches[4];

        if ($this->code_block_content_func) {
            $codeblock = call_user_func($this->code_block_content_func, $codeblock, $classname);
        } else {
            $codeblock = htmlspecialchars($codeblock, ENT_NOQUOTES);
        }

        $codeblock = preg_replace_callback('/^\n+/',
            array($this, '_doFencedCodeBlocks_newlines'), $codeblock);

        $classes = array();
        if ($classname != '') {
            if ($classname{0} == '.') {
                $classname = substr($classname, 1);
            }
            $classes[] = $this->code_class_prefix.$classname;
        }
        $attr_str = $this->doExtraAttributes($this->code_attr_on_pre ? 'pre' : 'code', $attrs, null, $classes);
        $pre_attr_str = $this->code_attr_on_pre ? $attr_str : '';
        $code_attr_str = $this->code_attr_on_pre ? '' : $attr_str;
        $codeblock = "<pre$pre_attr_str><code$code_attr_str>$codeblock</code></pre>";

        return "\n\n".$this->hashBlock($codeblock)."\n\n";
    }

    /**
     * Fenced code block newlines callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doFencedCodeBlocks_newlines($matches)
    {
        return str_repeat("<br$this->empty_element_suffix", strlen($matches[0]));
    }

    protected function doLists($text)
    {
        $less_than_tab = $this->tab_width - 1;

        // Re-usable patterns to match list item bullets and number markers:
        $marker_ul_re  = '[*+-]';
        $marker_ol_re  = '\d+[\.]';

        $markers_relist = array(
            $marker_ul_re => $marker_ol_re,
            $marker_ol_re => $marker_ul_re,
        );

        foreach ($markers_relist as $marker_re => $other_marker_re) {
            // Re-usable pattern to match any entirel ul or ol list:
            $whole_list_re = '
                (                               # $1 = whole list
                  (                             # $2
                    ([ ]{0,'.$less_than_tab.'}) # $3 = number of spaces
                    ('.$marker_re.')            # $4 = first list item marker
                    [ ]+
                  )
                  (?s:.+?)
                  (                             # $5
                      \z
                    |
                      \n{2,}
                      (?=\S)
                      (?!                       # Negative lookahead for another list item marker
                        [ ]*
                        '.$marker_re.'[ ]+
                      )
                    |
                      (?=                       # Lookahead for another kind of list
                        \n
                        \3                      # Must have the same indentation
                        '.$other_marker_re.'[ ]+
                      )
                  )
                )
            '; // mx

            // We use a different prefix before nested lists than top-level
            // lists. See extended comment in _ProcessListItems().
            if ($this->list_level) {
                $text = preg_replace_callback('{
                        ^
                        '.$whole_list_re.'
                    }mx',
                    array($this, '_doLists_callback'), $text);
            } else {
                $text = preg_replace_callback('{
                        (?:(?<=\n)\n|\A\n?) # Must eat the newline
                        '.$whole_list_re.'
                    }mx',
                    array($this, '_doLists_callback'), $text);
            }
        }

        return $text;
    }

    protected function _doLists_callback($matches)
    {
        // Re-usable patterns to match list item bullets and number markers:
        $marker_ul_re  = '[*+-]';
        $marker_ol_re  = '\d+[\.]';
        $marker_any_re = "(?:$marker_ul_re|$marker_ol_re)";
        $marker_ol_start_re = '[0-9]+';

        $list = $matches[1];
        $list_type = preg_match("/$marker_ul_re/", $matches[4]) ? "ul" : "ol";

        $marker_any_re = ($list_type == "ul" ? $marker_ul_re : $marker_ol_re);

        $list .= "\n";
        $result = $this->processListItems($list, $marker_any_re);

        $ol_start = 1;
        if ($this->enhanced_ordered_list) {
            // Get the start number for ordered list.
            if ($list_type == 'ol') {
                $ol_start_array = array();
                $ol_start_check = preg_match("/$marker_ol_start_re/", $matches[4], $ol_start_array);
                if ($ol_start_check) {
                    $ol_start = $ol_start_array[0];
                }
            }
        }

        if ($ol_start > 1 && $list_type == 'ol') {
            $result = $this->hashBlock("<$list_type start=\"$ol_start\">\n".$result."</$list_type>");
        } else {
            $result = $this->hashBlock("<$list_type>\n".$result."</$list_type>");
        }

        return "\n".$result."\n\n";
    }

    /**
     * Process the contents of a single ordered or unordered list, splitting it
     * into individual list items.
     *
     * The $this->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.".
     *
     * @param  string $list_str
     * @param  string $marker_any_re
     * @return string
     */
    protected function processListItems($list_str, $marker_any_re)
    {
        $this->list_level++;

        // trim trailing blank lines:
        $list_str = preg_replace("/\n{2,}\\z/", "\n", $list_str);

        $list_str = preg_replace_callback('{
            (\n)?                           # leading line = $1
            (^[ ]*)                         # leading whitespace = $2
            ('.$marker_any_re.'             # list marker and space = $3
                (?:[ ]+|(?=\n)) # space only required if item is not empty
            )
            ((?s:.*?))                      # list item text   = $4
            (?:(\n+(?=\n))|\n)              # tailing blank line = $5
            (?= \n* (\z | \2 ('.$marker_any_re.') (?:[ ]+|(?=\n))))
            }xm',
            array($this, '_processListItems_callback'), $list_str);

        $this->list_level--;

        return $list_str;
    }

    /**
     * Process list items callback.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _processListItems_callback($matches)
    {
        $item = $matches[4];
        $leading_line = & $matches[1];
        $leading_space = & $matches[2];
        $marker_space = $matches[3];
        $tailing_blank_line = & $matches[5];

        if ($leading_line || $tailing_blank_line ||
            preg_match('/\n{2,}/', $item)) {
            // Replace marker with the appropriate whitespace indentation
            $item = $leading_space.str_repeat(' ', strlen($marker_space)).$item;
            $item = $this->runBlockGamut($this->outdent($item)."\n");
        } else {
            // Recursion for sub-lists:
            $item = $this->doLists($this->outdent($item));
            $item = preg_replace('/\n+$/', '', $item);
            $item = $this->runSpanGamut($item);
        }

        return "<li>".$item."</li>\n";
    }

    /**
     * Process Markdown `<pre><code>` blocks.
     *
     * @param  string $text
     * @return string
     */
    protected function doCodeBlocks($text)
    {
        $text = preg_replace_callback('{
                (?:\n\n|\A\n?)
                (               # $1 = the code block -- one or more lines, starting with a space/tab
                  (?>
                    [ ]{'.$this->tab_width.'}  # Lines must start with a tab or a tab-width of spaces
                    .*\n+
                  )+
                )
                ((?=^[ ]{0,'.$this->tab_width.'}\S)|\Z) # Lookahead for non-space at line-start, or end of doc
            }xm',
            array($this, '_doCodeBlocks_callback'), $text);

        return $text;
    }

    /**
     * Process code blocks callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doCodeBlocks_callback($matches)
    {
        $codeblock = $matches[1];

        $codeblock = $this->outdent($codeblock);
        $codeblock = htmlspecialchars($codeblock, ENT_NOQUOTES);

        // trim leading newlines and trailing newlines
        $codeblock = preg_replace('/\A\n+|\n+\z/', '', $codeblock);

        $codeblock = "<pre><code>$codeblock\n</code></pre>";

        return "\n\n".$this->hashBlock($codeblock)."\n\n";
    }

    /**
     * Create a code span markup for $code.
     *
     * Called from handleSpanToken.
     *
     * @param  string $code
     * @return string
     */
    protected function makeCodeSpan($code)
    {
        $code = htmlspecialchars(trim($code), ENT_NOQUOTES);

        return $this->hashPart("<code>$code</code>");
    }

    /**
     * Prepare regular expressions for searching emphasis tokens in any context.
     *
     * @return void
     */
    protected function prepareItalicsAndBold()
    {
        foreach ($this->em_relist as $em => $em_re) {
            foreach ($this->strong_relist as $strong => $strong_re) {
                // Construct list of allowed token expressions.
                $token_relist = array();

                if (isset($this->em_strong_relist["$em$strong"])) {
                    $token_relist[] = $this->em_strong_relist["$em$strong"];
                }

                $token_relist[] = $em_re;
                $token_relist[] = $strong_re;

                // Construct master expression from list.
                $token_re = '{('.implode('|', $token_relist).')}';
                $this->em_strong_prepared_relist["$em$strong"] = $token_re;
            }
        }
    }

    /**
     * [doItalicsAndBold description]
     *
     * @param  [type] $text
     * @return [type]
     */
    protected function doItalicsAndBold($text)
    {
        $token_stack = array('');
        $text_stack = array('');
        $em = '';
        $strong = '';
        $tree_char_em = false;

        while (1) {
            //
            // Get prepared regular expression for seraching emphasis tokens
            // in current context.
            //
            $token_re = $this->em_strong_prepared_relist["$em$strong"];

            //
            // Each loop iteration search for the next emphasis token.
            // Each token is then passed to handleSpanToken.
            //
            $parts = preg_split($token_re, $text, 2, PREG_SPLIT_DELIM_CAPTURE);
            $text_stack[0] .= $parts[0];
            $token = & $parts[1];
            $text = & $parts[2];

            if (empty($token)) {
                // Reached end of text span: empty stack without emitting.
                // any more emphasis.
                while ($token_stack[0]) {
                    $text_stack[1] .= array_shift($token_stack);
                    $text_stack[0] .= array_shift($text_stack);
                }
                break;
            }

            $token_len = strlen($token);
            if ($tree_char_em) {
                // Reached closing marker while inside a three-char emphasis.
                if ($token_len == 3) {
                    // Three-char closing marker, close em and strong.
                    array_shift($token_stack);
                    $span = array_shift($text_stack);
                    $span = $this->runSpanGamut($span);
                    $span = "<strong><em>$span</em></strong>";
                    $text_stack[0] .= $this->hashPart($span);
                    $em = '';
                    $strong = '';
                } else {
                    // Other closing marker: close one em or strong and
                    // change current token state to match the other
                    $token_stack[0] = str_repeat($token{0}, 3-$token_len);
                    $tag = $token_len == 2 ? "strong" : "em";
                    $span = $text_stack[0];
                    $span = $this->runSpanGamut($span);
                    $span = "<$tag>$span</$tag>";
                    $text_stack[0] = $this->hashPart($span);
                    $$tag = ''; // $$tag stands for $em or $strong
                }
                $tree_char_em = false;
            } elseif ($token_len == 3) {
                if ($em) {
                    // Reached closing marker for both em and strong.
                    // Closing strong marker:
                    for ($i = 0; $i < 2; ++$i) {
                        $shifted_token = array_shift($token_stack);
                        $tag = strlen($shifted_token) == 2 ? "strong" : "em";
                        $span = array_shift($text_stack);
                        $span = $this->runSpanGamut($span);
                        $span = "<$tag>$span</$tag>";
                        $text_stack[0] .= $this->hashPart($span);
                        $$tag = ''; // $$tag stands for $em or $strong
                    }
                } else {
                    // Reached opening three-char emphasis marker. Push on token
                    // stack; will be handled by the special condition above.
                    $em = $token{0};
                    $strong = "$em$em";
                    array_unshift($token_stack, $token);
                    array_unshift($text_stack, '');
                    $tree_char_em = true;
                }
            } elseif ($token_len == 2) {
                if ($strong) {
                    // Unwind any dangling emphasis marker:
                    if (strlen($token_stack[0]) == 1) {
                        $text_stack[1] .= array_shift($token_stack);
                        $text_stack[0] .= array_shift($text_stack);
                    }
                    // Closing strong marker:
                    array_shift($token_stack);
                    $span = array_shift($text_stack);
                    $span = $this->runSpanGamut($span);
                    $span = "<strong>$span</strong>";
                    $text_stack[0] .= $this->hashPart($span);
                    $strong = '';
                } else {
                    array_unshift($token_stack, $token);
                    array_unshift($text_stack, '');
                    $strong = $token;
                }
            } else {
                // Here $token_len == 1
                if ($em) {
                    if (strlen($token_stack[0]) == 1) {
                        // Closing emphasis marker:
                        array_shift($token_stack);
                        $span = array_shift($text_stack);
                        $span = $this->runSpanGamut($span);
                        $span = "<em>$span</em>";
                        $text_stack[0] .= $this->hashPart($span);
                        $em = '';
                    } else {
                        $text_stack[0] .= $token;
                    }
                } else {
                    array_unshift($token_stack, $token);
                    array_unshift($text_stack, '');
                    $em = $token;
                }
            }
        }

        return $text_stack[0];
    }

    protected function doBlockQuotes($text)
    {
        $text = preg_replace_callback('/
              (                             # Wrap whole match in $1
                (?>
                  ^[ ]*>[ ]?                # ">" at the start of a line
                    .+\n                    # rest of the first line
                  (.+\n)*                   # subsequent consecutive lines
                  \n*                       # blanks
                )+
              )
            /xm',
            array($this, '_doBlockQuotes_callback'), $text);

        return $text;
    }

    protected function _doBlockQuotes_callback($matches)
    {
        $bq = $matches[1];
        // trim one level of quoting - trim whitespace-only lines
        $bq = preg_replace('/^[ ]*>[ ]?|^[ ]+$/m', '', $bq);
        $bq = $this->runBlockGamut($bq);        // recurse

        $bq = preg_replace('/^/m', "  ", $bq);
        // These leading spaces cause problem with <pre> content,
        // so we need to fix that:
        $bq = preg_replace_callback('{(\s*<pre>.+?</pre>)}sx',
            array($this, '_doBlockQuotes_callback2'), $bq);

        return "\n".$this->hashBlock("<blockquote>\n$bq\n</blockquote>")."\n\n";
    }

    protected function _doBlockQuotes_callback2($matches)
    {
        $pre = $matches[1];
        $pre = preg_replace('/^  /m', '', $pre);

        return $pre;
    }

    /**
     * Form paragraphs
     *
     * @param  string $text The string to process with html <p> tags
     * @return string
     */
    protected function formParagraphs($text)
    {
        // Strip leading and trailing lines:
        $text = preg_replace('/\A\n+|\n+\z/', '', $text);

        $grafs = preg_split('/\n{2,}/', $text, -1, PREG_SPLIT_NO_EMPTY);

        // Wrap <p> tags and unhashify HTML blocks
        foreach ($grafs as $key => $value) {
            $value = trim($this->runSpanGamut($value));

            // Check if this should be enclosed in a paragraph.
            // Clean tag hashes & block tag hashes are left alone.
            $is_p = !preg_match('/^B\x1A[0-9]+B|^C\x1A[0-9]+C$/', $value);

            if ($is_p) {
                $value = "<p>$value</p>";
            }
            $grafs[$key] = $value;
        }

        // Join grafs in one text, then unhash HTML tags.
        $text = implode("\n\n", $grafs);

        // Finish by removing any tag hashes still present in $text.
        $text = $this->unhash($text);

        return $text;
    }

    protected function stripFootnotes($text)
    {
        //
        // Strips link definitions from text, stores the URLs and titles in
        // hash references.
        //
        $less_than_tab = $this->tab_width - 1;

        // Link defs are in the form: [^id]: url "optional title"
        $text = preg_replace_callback('{
            ^[ ]{0,'.$less_than_tab.'}\[\^(.+?)\][ ]?:  # note_id = $1
              [ ]*
              \n?                   # maybe *one* newline
            (                       # text = $2 (no blank lines allowed)
                (?:
                    .+              # actual text
                |
                    \n              # newlines but
                    (?!\[.+?\][ ]?:\s)# negative lookahead for footnote or link definition marker.
                    (?!\n+[ ]{0,3}\S)# ensure line is not blank and followed
                                    # by non-indented content
                )*
            )
            }xm',
            array($this, '_stripFootnotes_callback'),
            $text);

        return $text;
    }

    protected function _stripFootnotes_callback($matches)
    {
        $note_id = $this->fn_id_prefix.$matches[1];
        $this->footnotes[$note_id] = $this->outdent($matches[2]);

        return ''; // String that will replace the block
    }

    /**
     * Replace footnote references in $text [^id] with a special text-token
     * which will be replaced by the actual footnote marker in appendFootnotes.
     *
     * @param  string $text
     * @return string
     */
    protected function doFootnotes($text)
    {
        if (!$this->in_anchor) {
            $text = preg_replace('{\[\^(.+?)\]}', "F\x1Afn:\\1\x1A:", $text);
        }

        return $text;
    }

    /**
     * Append footnote list to text.
     *
     * @param  string $text
     * @return string
     */
    protected function appendFootnotes($text)
    {
        $text = preg_replace_callback('{F\x1Afn:(.*?)\x1A:}',
            array($this, '_appendFootnotes_callback'), $text);

        if (!empty($this->footnotes_ordered)) {
            $text .= "\n\n";
            $text .= "<div class=\"footnotes\">\n";
            $text .= "<hr".$this->empty_element_suffix."\n";
            $text .= "<ol>\n\n";

            $attr = "";
            if ($this->fn_backlink_class != "") {
                $class = $this->fn_backlink_class;
                $class = $this->encodeAttribute($class);
                $attr .= " class=\"$class\"";
            }
            if ($this->fn_backlink_title != "") {
                $title = $this->fn_backlink_title;
                $title = $this->encodeAttribute($title);
                $attr .= " title=\"$title\"";
            }
            $num = 0;

            while (!empty($this->footnotes_ordered)) {
                $footnote = reset($this->footnotes_ordered);
                $note_id = key($this->footnotes_ordered);
                unset($this->footnotes_ordered[$note_id]);
                $ref_count = $this->footnotes_ref_count[$note_id];
                unset($this->footnotes_ref_count[$note_id]);
                unset($this->footnotes[$note_id]);

                $footnote .= "\n"; // Need to append newline before parsing.
                $footnote = $this->runBlockGamut("$footnote\n");
                $footnote = preg_replace_callback('{F\x1Afn:(.*?)\x1A:}',
                    array($this, '_appendFootnotes_callback'), $footnote);

                $attr = str_replace("%%", ++$num, $attr);
                $note_id = $this->encodeAttribute($note_id);

                // Prepare backlink, multiple backlinks if multiple references
                $backlink = "<a href=\"#fnref:$note_id\"$attr>&#8617;</a>";
                for ($ref_num = 2; $ref_num <= $ref_count; ++$ref_num) {
                    $backlink .= " <a href=\"#fnref$ref_num:$note_id\"$attr>&#8617;</a>";
                }
                // Add backlink to last paragraph; create new paragraph if needed.
                if (preg_match('{</p>$}', $footnote)) {
                    $footnote = substr($footnote, 0, -4)."&#160;$backlink</p>";
                } else {
                    $footnote .= "\n\n<p>$backlink</p>";
                }

                $text .= "<li id=\"fn:$note_id\">\n";
                $text .= $footnote."\n";
                $text .= "</li>\n\n";
            }

            $text .= "</ol>\n";
            $text .= "</div>";
        }

        return $text;
    }

    /**
     * Create footnote marker only if it has a corresponding footnote *and* the
     * footnote hasn't been used by another marker.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _appendFootnotes_callback($matches)
    {
        $node_id = $this->fn_id_prefix.$matches[1];
        if (isset($this->footnotes[$node_id])) {
            $num = &$this->footnotes_numbers[$node_id];
            if (!isset($num)) {
                // Transfer footnote content to the ordered list and give it its
                // number
                $this->footnotes_ordered[$node_id] = $this->footnotes[$node_id];
                $this->footnotes_ref_count[$node_id] = 1;
                $num = $this->footnote_counter++;
                $ref_count_mark = '';
            } else {
                $ref_count_mark = $this->footnotes_ref_count[$node_id] += 1;
            }

            $attr = "";
            if ($this->fn_link_class != "") {
                $class = $this->fn_link_class;
                $class = $this->encodeAttribute($class);
                $attr .= " class=\"$class\"";
            }
            if ($this->fn_link_title != "") {
                $title = $this->fn_link_title;
                $title = $this->encodeAttribute($title);
                $attr .= " title=\"$title\"";
            }

            $attr = str_replace("%%", $num, $attr);
            $node_id = $this->encodeAttribute($node_id);

            return
            "<sup id=\"fnref$ref_count_mark:$node_id\">".
                "<a href=\"#fn:$node_id\"$attr>$num</a>".
                "</sup>";
        }

        return "[^".$matches[1]."]";
    }

    /**
     * Strips abbreviations from text, stores titles in hash references.
     *
     * @param  string $text
     * @return string
     */
    protected function stripAbbreviations($text)
    {
        $less_than_tab = $this->tab_width - 1;

        // Link defs are in the form: [id]*: url "optional title"
        $text = preg_replace_callback('{
            ^[ ]{0,'.$less_than_tab.'}\*\[(.+?)\][ ]?:  # abbr_id = $1
            (.*)                    # text = $2 (no blank lines allowed)
            }xm',
            array($this, '_stripAbbreviations_callback'),
            $text);

        return $text;
    }

    protected function _stripAbbreviations_callback($matches)
    {
        $abbr_word = $matches[1];
        $abbr_desc = $matches[2];

        if ($this->abbr_word_re) {
            $this->abbr_word_re .= '|';
        }

        $this->abbr_word_re .= preg_quote($abbr_word);
        $this->abbr_desciptions[$abbr_word] = trim($abbr_desc);

        return ''; // String that will replace the block
    }

    /**
     * Find defined abbreviations in text and wrap them in <abbr> elements.
     *
     * @param  string $text
     * @return string
     */
    protected function doAbbreviations($text)
    {
        if ($this->abbr_word_re) {
            // cannot use the /x modifier because abbr_word_re may
            // contain significant spaces:
            $text = preg_replace_callback('{'.
                '(?<![\w\x1A])'.
                '(?:'.$this->abbr_word_re.')'.
                '(?![\w\x1A])'.
                '}',
                array($this, '_doAbbreviations_callback'), $text);
        }

        return $text;
    }

    protected function _doAbbreviations_callback($matches)
    {
        $abbr = $matches[0];
        if (isset($this->abbr_desciptions[$abbr])) {
            $desc = $this->abbr_desciptions[$abbr];
            if (empty($desc)) {
                return $this->hashPart("<abbr>$abbr</abbr>");
            } else {
                $desc = $this->encodeAttribute($desc);

                return $this->hashPart("<abbr title=\"$desc\">$abbr</abbr>");
            }
        } else {
            return $matches[0];
        }
    }

    /**
     * Encode text for a double-quoted HTML attribute. This function is *not*
     * suitable for attributes enclosed in single quotes.
     *
     * @param  string $text
     * @return string
     */
    protected function encodeAttribute($text)
    {
        $text = $this->encodeAmpsAndAngles($text);
        $text = str_replace('"', '&quot;', $text);

        return $text;
    }

    /**
     * Encode text for a double-quoted HTML attribute containing a URL, applying
     * the URL filter if set.
     *
     * Also generates the textual representation for the URL (removing mailto:
     * or tel:) storing it in $text.
     *
     * This function is *not* suitable for attributes enclosed in single quotes.
     *
     * @param  string $url
     * @param  string &$text
     * @return string
     */
    protected function encodeURLAttribute($url, &$text = null)
    {
        if ($this->url_filter_func) {
            $url = call_user_func($this->url_filter_func, $url);
        }

        if (preg_match('{^mailto:}i', $url)) {
            $url = $this->encodeEntityObfuscatedAttribute($url, $text, 7);
        } elseif (preg_match('{^tel:}i', $url)) {
            $url = $this->encodeAttribute($url);
            $text = substr($url, 4);
        } else {
            $url = $this->encodeAttribute($url);
            $text = $url;
        }

        return $url;
    }

    /**
     * Smart processing for ampersands and angle brackets that need to be
     * encoded. Valid character entities are left alone unless the no-entities
     * mode is set.
     *
     * @param  string $text
     * @return string
     */
    protected function encodeAmpsAndAngles($text)
    {
        if ($this->no_entities) {
            $text = str_replace('&', '&amp;', $text);
        } else {
            // Ampersand-encoding based entirely on Nat Irons's Amputator
            // MT plugin: <http://bumppo.net/projects/amputator/>
            $text = preg_replace('/&(?!#?[xX]?(?:[0-9a-fA-F]+|\w+);)/',
                '&amp;', $text);
        }

        // Encode remaining <'s
        $text = str_replace('<', '&lt;', $text);

        return $text;
    }

    /**
     * Process auto links.
     *
     * @param  string $text
     * @return string
     */
    protected function doAutoLinks($text)
    {
        $text = preg_replace_callback('{<((https?|ftp|dict|tel):[^\'">\s]+)>}i',
            array($this, '_doAutoLinks_url_callback'), $text);

        // Email addresses: <address@domain.foo>
        $text = preg_replace_callback('{
            <
            (?:mailto:)?
            (
                (?:
                    [-!#$%&\'*+/=?^_`.{|}~\w\x80-\xFF]+
                |
                    ".*?"
                )
                \@
                (?:
                    [-a-z0-9\x80-\xFF]+(\.[-a-z0-9\x80-\xFF]+)*\.[a-z]+
                |
                    \[[\d.a-fA-F:]+\]   # IPv4 & IPv6
                )
            )
            >
            }xi',
            array($this, '_doAutoLinks_email_callback'), $text);

        return $text;
    }

    /**
     * Process auto links url callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doAutoLinks_url_callback($matches)
    {
        $url = $this->encodeURLAttribute($matches[1], $text);
        $link = "<a href=\"$url\">$text</a>";

        return $this->hashPart($link);
    }

    /**
     * Process auto links email callback function.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _doAutoLinks_email_callback($matches)
    {
        $addr = $matches[1];
        $url = $this->encodeURLAttribute("mailto:$addr", $text);
        $link = "<a href=\"$url\">$text</a>";

        return $this->hashPart($link);
    }

    /**
     * Input: some text to obfuscate, e.g. "mailto:foo@example.com"
     *
     * Output: the same text but with most characters encoded as either a
     * decimal or hex entity, in the hopes of foiling most address harvesting
     * spam bots. E.g.:
     *
     *   &#109;&#x61;&#105;&#x6c;&#116;&#x6f;&#58;&#x66;o&#111;
     *   &#x40;&#101;&#x78;&#97;&#x6d;&#112;&#x6c;&#101;&#46;&#x63;&#111;
     *   &#x6d;
     *
     * Note: the additional output $tail is assigned the same value as the
     * ouput, minus the number of characters specified by $head_length.
     *
     * Based by a filter by Matthew Wickline, posted to BBEdit-Talk. With some
     * optimizations by Milian Wolff. Forced encoding of HTML attribute special
     * characters by Allan Odgaard.
     *
     * @param  string  $text
     * @param  string  &$tail
     * @param  integer $head_length
     * @return string
     */
    protected function encodeEntityObfuscatedAttribute($text, &$tail = null, $head_length = 0)
    {
        if ($text == "") {
            return $tail = "";
        }

        $chars = preg_split('/(?<!^)(?!$)/', $text);
        $seed = (int) abs(crc32($text) / strlen($text)); // Deterministic seed.

        foreach ($chars as $key => $char) {
            $ord = ord($char);

            // Ignore non-ascii chars.
            if ($ord < 128) {
                $r = ($seed * (1 + $key)) % 100; // Pseudo-random function.
                // roughly 10% raw, 45% hex, 45% dec
                // '@' *must* be encoded. I insist.
                // '"' and '>' have to be encoded inside the attribute
                if ($r > 90 && strpos('@"&>', $char) === false) {
                    /* do nothing */;
                } elseif ($r < 45) {
                    $chars[$key] = '&#x'.dechex($ord).';';
                } else {
                    $chars[$key] = '&#'.$ord.';';
                }
            }
        }

        $text = implode('', $chars);
        $tail = $head_length ? implode('', array_slice($chars, $head_length)) : $text;

        return $text;
    }

    /**
     * Take the string $str and parse it into tokens, hashing embedded HTML,
     * escaped characters and handling code spans.
     *
     * @param  string $str
     * @return string
     */
    protected function parseSpan($str)
    {
        $output = '';
        $span_re = '{
                        (
                        \\\\'.$this->escape_chars_re.'
                        |
                        (?<![`\\\\])
                        `+            # code span marker
                        '.($this->no_markup ? '' : '
                        |
                        <!--    .*?     -->   # comment
                        |
                        <\?.*?\?> | <%.*?%>   # processing instruction
                        |
                        <[/!$]?[-a-zA-Z0-9:_]+  # regular tags
                        (?>
                        \s
                        (?>[^"\'>]+|"[^"]*"|\'[^\']*\')*
                        )?
                        >
                        ').'
                        )
                    }xs';

        while (1) {
            //
            // Each loop iteration search for either the next tag, the next
            // opening code span marker, or the next escaped character. Each
            // token is then passed to handleSpanToken.
            //
            $parts = preg_split($span_re, $str, 2, PREG_SPLIT_DELIM_CAPTURE);

            // Create token from text preceding tag.
            if ($parts[0] != "") {
                $output .= $parts[0];
            }

            // Check if we reach the end.
            if (isset($parts[1])) {
                $output .= $this->handleSpanToken($parts[1], $parts[2]);
                $str = $parts[2];
            } else {
                break;
            }
        }

        return $output;
    }

    /**
     * Handle $token provided by parseSpan by determining its nature and
     * returning the corresponding value that should replace it.
     *
     * @param  [type] $token
     * @param  string &$str
     * @return string
     */
    protected function handleSpanToken($token, &$str)
    {
        switch ($token{0}) {
        case "\\":
            return $this->hashPart("&#".ord($token{1}).";");
        case "`":
            // Search for end marker in remaining text.
            if (preg_match('/^(.*?[^`])'.preg_quote($token).'(?!`)(.*)$/sm',
                    $str, $matches)) {
                $str = $matches[2];
                $codespan = $this->makeCodeSpan($matches[1]);

                return $this->hashPart($codespan);
            }

            return $token; // return as text since no ending marker found.
        default:
            return $this->hashPart($token);
        }
    }

    /**
     * Remove one level of line-leading tabs or spaces.
     *
     * @param  string $text
     * @return string
     */
    protected function outdent($text)
    {
        return preg_replace('/^(\t|[ ]{1,'.$this->tab_width.'})/m', '', $text);
    }

    /**
     * Replace tabs with the appropriate amount of space.
     *
     * For each line we separate the line in blocks delimited by tab characters.
     * Then we reconstruct every line by adding the appropriate number of space
     * between each blocks.
     *
     * @param  string $text
     * @return string
     */
    protected function detab($text)
    {
        $text = preg_replace_callback('/^.*\t.*$/m',
            array($this, '_detab_callback'), $text);

        return $text;
    }

    /**
     * Callback function for `detab()`.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _detab_callback($matches)
    {
        $line = $matches[0];
        $strlen = $this->utf8_strlen; // strlen function for UTF-8.

        // Split in blocks.
        $blocks = explode("\t", $line);
        // Add each blocks to the line.
        $line = $blocks[0];
        unset($blocks[0]); // Do not add first block twice.

        foreach ($blocks as $block) {
            // Calculate amount of space, insert spaces, insert block.
            $amount = $this->tab_width - $strlen($line, 'UTF-8') % $this->tab_width;
            $line .= str_repeat(" ", $amount).$block;
        }

        return $line;
    }

    /**
     * Check for the availability of the function in the `utf8_strlen` property
     * (initially `mb_strlen`).
     *
     * If the function is not available, create a function that will loosely
     * count the number of UTF-8 characters with a regular expression.
     *
     * @return void
     */
    protected function _initDetab()
    {
        if (function_exists($this->utf8_strlen)) {
            return;
        }

        $this->utf8_strlen = create_function('$text', 'return preg_match_all(
            "/[\\\\x00-\\\\xBF]|[\\\\xC0-\\\\xFF][\\\\x80-\\\\xBF]*/",
            $text, $m);');
    }

    /**
     * Swap back in all the tags hashed by _HashHTMLBlocks.
     *
     * @param  string $text
     * @return string
     */
    protected function unhash($text)
    {
        return preg_replace_callback('/(.)\x1A[0-9]+\1/',
            array($this, '_unhash_callback'), $text);
    }

    /**
     * Callback function for `unhash()`.
     *
     * @param  array  $matches
     * @return string
     */
    protected function _unhash_callback($matches)
    {
        return $this->html_hashes[$matches[0]];
    }

    /**
     * Parse attributes caught by the $this->id_class_attr_catch_re expression
     * and return the HTML-formatted list of attributes.
     *
     * Currently supported attributes are .class and #id.
     *
     * In addition, this method also supports supplying a default Id value,
     * which will be used to populate the id attribute in case it was not
     * overridden.
     *
     * @param string $tag_name
     * @param string $attr
     * @param string $defaultIdValue
     * @param array $classes
     *
     * @return string
     */
    protected function doExtraAttributes($tag_name, $attr, $defaultIdValue = null, $classes = array())
    {
        if (empty($attr) && !$defaultIdValue && empty($classes)) {
            return '';
        }

        // Split on components
        preg_match_all('/[#.a-z][-_:a-zA-Z0-9=]+/', $attr, $matches);
        $elements = $matches[0];

        // handle classes and ids (only first id taken into account)
        $attributes = array();
        $id = false;
        foreach ($elements as $element) {
            if ($element{0} == '.') {
                $classes[] = substr($element, 1);
            } elseif ($element{0} == '#') {
                if ($id === false) {
                    $id = substr($element, 1);
                }
            } elseif (strpos($element, '=') > 0) {
                $parts = explode('=', $element, 2);
                $attributes[] = $parts[0].'="'.$parts[1].'"';
            }
        }
        if (!$id) {
            $id = $defaultIdValue;
        }

        // compose attributes as string
        $attr_str = '';
        if (!empty($id)) {
            $attr_str .= ' id="'.$this->encodeAttribute($id).'"';
        }
        if (!empty($classes)) {
            $attr_str .= ' class="'.implode(' ', $classes).'"';
        }
        if (!$this->no_markup && !empty($attributes)) {
            $attr_str .= ' '.implode(' ', $attributes);
        }

        return $attr_str;
    }
}
