* @copyright 2004-2019 Michel Fortin * @copyright (Original Markdown) 2004-2006 John Gruber */ namespace Michelf; /** * Markdown Parser Class */ class Markdown implements MarkdownInterface { /** * Define the package version * @var string */ const MARKDOWNLIB_VERSION = "1.9.0"; /** * Simple function interface - Initialize the parser and return the result * of its transform method. This will work fine for derived classes too. * * @api * * @param string $text * @return string */ public static function defaultTransform($text) { // Take parser class on which this function was called. $parser_class = \get_called_class(); // Try to take parser from the static parser list static $parser_list; $parser =& $parser_list[$parser_class]; // Create the parser it not already set if (!$parser) { $parser = new $parser_class; } // Transform text using parser. return $parser->transform($text); } /** * Configuration variables */ /** * Change to ">" for HTML output. * @var string */ public $empty_element_suffix = " />"; /** * The width of indentation of the output markup * @var int */ public $tab_width = 4; /** * Change to `true` to disallow markup or entities. * @var boolean */ public $no_markup = false; public $no_entities = false; /** * Change to `true` to enable line breaks on \n without two trailling spaces * @var boolean */ public $hard_wrap = false; /** * Predefined URLs and titles for reference links and images. * @var array */ public $predef_urls = array(); public $predef_titles = array(); /** * Optional filter function for URLs * @var callable|null */ public $url_filter_func = null; /** * Optional header id="" generation callback function. * @var callable|null */ public $header_id_func = null; /** * Optional function for converting code block content to HTML * @var callable|null */ public $code_block_content_func = null; /** * Optional function for converting code span content to HTML. * @var callable|null */ public $code_span_content_func = null; /** * 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: *
    *
  1. List item two
    2. *
  2. List item three
    3. *
* * @var bool */ public $enhanced_ordered_list = false; /** * Parser implementation */ /** * Regex to match balanced [brackets]. * Needed to insert a maximum bracked depth while converting to PHP. * @var int */ protected $nested_brackets_depth = 6; protected $nested_brackets_re; protected $nested_url_parenthesis_depth = 4; protected $nested_url_parenthesis_re; /** * Table of hash values for escaped characters: * @var string */ protected $escape_chars = '\`*_{}[]()>#+-.!'; protected $escape_chars_re; /** * Constructor function. Initialize appropriate member variables. * @return void */ 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); } /** * Internal hashes used during transformation. * @var array */ protected $urls = array(); protected $titles = array(); protected $html_hashes = array(); /** * Status flag to avoid invalid nesting. * @var boolean */ protected $in_anchor = false; /** * Status flag to avoid invalid nesting. * @var boolean */ protected $in_emphasis_processing = 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; $this->in_emphasis_processing = false; } /** * Called after the transformation process to clear any variable which may * be taking up memory unnecessarly. * @return void */ protected function teardown() { $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. * * @api * * @param string $text * @return string */ public function transform($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 regexen 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"; } /** * Define the document gamut * @var array */ protected $document_gamut = array( // Strip link definitions, store in hashes. "stripLinkDefinitions" => 20, "runBasicBlockGamut" => 30, ); /** * Strips link definitions from text, stores the URLs and titles in * hash references * @param string $text * @return string */ protected function stripLinkDefinitions($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.'}\[(.+)\][ ]?: # id = $1 [ ]* \n? # maybe *one* newline [ ]* (?: <(.+?)> # url = $2 | (\S+?) # url = $3 ) [ ]* \n? # maybe one newline [ ]* (?: (?<=\s) # lookbehind for whitespace ["(] (.*?) # title = $4 [")] [ ]* )? # title is optional (?:\n+|\Z) }xm', array($this, '_stripLinkDefinitions_callback'), $text ); return $text; } /** * The callback to strip link definitions * @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]; return ''; // String that will replace the block } /** * Hashify HTML blocks * @param string $text * @return string */ protected function hashHTMLBlocks($text) { if ($this->no_markup) { return $text; } $less_than_tab = $this->tab_width - 1; /** * Hashify HTML blocks: * * We only want to do this for block-level HTML tags, such as headers, * lists, and tables. That's because we still want to wrap

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: * * * List "a" is made of tags which can be both inline or block-level. * These will be treated block-level when the start tag is alone on * its line, otherwise they're not matched here and will be taken as * inline later. * * List "b" is made of tags which are always block-level; */ $block_tags_a_re = 'ins|del'; $block_tags_b_re = 'p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|address|'. 'script|noscript|style|form|fieldset|iframe|math|svg|'. 'article|section|nav|aside|hgroup|header|footer|'. 'figure'; // Regular expression for the content of a block tag. $nested_tags_level = 4; $attr = ' (?> # optional tag attributes \s # starts with whitespace (?> [^>"/]+ # text outside quotes | /+(?!>) # slash not followed by ">" | "[^"]*" # text inside double quotes (tolerate ">") | \'[^\']*\' # text inside single quotes (tolerate ">") )* )? '; $content = str_repeat(' (?> [^<]+ # content without tag | <\2 # nested opening tag '.$attr.' # attributes (?> /> | >', $nested_tags_level). // end of opening tag '.*?'. // last level nested tag content str_repeat(' # closing nested tag ) | <(?!/\2\s*> # other tags with a different name ) )*', $nested_tags_level); $content2 = str_replace('\2', '\3', $content); /** * First, look for nested blocks, e.g.: *

*
* tags for inner block must be indented. *
*
* * The outermost tags must start at the left margin for this to match, * and the inner nested divs must be indented. * We need to do this before the next, more liberal match, because the * next match will start at the first `
` and stop at the * first `
`. */ $text = preg_replace_callback('{(?> (?> (?<=\n) # Starting on its own line | # or \A\n? # the at beginning of the doc ) ( # save in $1 # Match from `\n` to `\n`, handling nested tags # in between. [ ]{0,'.$less_than_tab.'} <('.$block_tags_b_re.')# start tag = $2 '.$attr.'> # attributes followed by > and \n '.$content.' # content, support nesting # the matching end tag [ ]* # trailing spaces/tabs (?=\n+|\Z) # followed by a newline or end of document | # Special version for tags of group a. [ ]{0,'.$less_than_tab.'} <('.$block_tags_a_re.')# start tag = $3 '.$attr.'>[ ]*\n # attributes followed by > '.$content2.' # content, support nesting # the matching end tag [ ]* # trailing spaces/tabs (?=\n+|\Z) # followed by a newline or end of document | # Special case just for
. It was easier to make a special # case than to make the other regex more complicated. [ ]{0,'.$less_than_tab.'} <(hr) # start tag = $2 '.$attr.' # attributes /?> # the matching end tag [ ]* (?=\n{2,}|\Z) # followed by a blank line or end of document | # Special case for standalone HTML comments: [ ]{0,'.$less_than_tab.'} (?s: ) [ ]* (?=\n{2,}|\Z) # followed by a blank line or end of document | # PHP and ASP-style processor instructions ( ) [ ]* (?=\n{2,}|\Z) # followed by a blank line or end of document ) )}Sxmi', array($this, '_hashHTMLBlocks_callback'), $text ); return $text; } /** * The callback for hashing HTML blocks * @param string $matches * @return string */ protected function _hashHTMLBlocks_callback($matches) { $text = $matches[1]; $key = $this->hashBlock($text); return "\n\n$key\n\n"; } /** * 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 convension, "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. * * @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; return $key; // String that will replace the tag. } /** * Shortcut function for hashPart with block-level boundaries. * @param string $text * @return string */ protected function hashBlock($text) { return $this->hashPart($text, 'B'); } /** * Define the block gamut - 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, ); /** * Run block gamut tranformations. * * We need to escape raw HTML in Markdown source before doing anything * else. This need to be done for each block, and not only at the * begining in the Markdown function since hashed blocks can be part of * list items and could have been indented. Indented blocks would have * been seen as a code block in a previous pass of hashHTMLBlocks. * * @param string $text * @return string */ protected function runBlockGamut($text) { $text = $this->hashHTMLBlocks($text); return $this->runBasicBlockGamut($text); } /** * Run block gamut tranformations, 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; } /** * Convert horizontal rules * @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("empty_element_suffix")."\n", $text ); } /** * These are all the transformations that occur *within* block-level * tags like paragraphs, headers, and list items. * @var array */ protected $span_gamut = array( // Process character escapes, code spans, and inline HTML // in one shot. "parseSpan" => -30, // Process anchor and image tags. Images must come first, // because ![foo][f] looks like an anchor. "doImages" => 10, "doAnchors" => 20, // Make links out of things like `` // Must come after doAnchors, because you can use < and > // delimiters in inline links like [this](). "doAutoLinks" => 30, "encodeAmpsAndAngles" => 40, "doItalicsAndBold" => 50, "doHardBreaks" => 60, ); /** * Run span gamut transformations * @param string $text * @return string */ protected function runSpanGamut($text) { foreach ($this->span_gamut as $method => $priority) { $text = $this->$method($text); } return $text; } /** * Do hard breaks * @param string $text * @return string */ protected function doHardBreaks($text) { if ($this->hard_wrap) { return preg_replace_callback('/ *\n/', array($this, '_doHardBreaks_callback'), $text); } else { return preg_replace_callback('/ {2,}\n/', array($this, '_doHardBreaks_callback'), $text); } } /** * Trigger part hashing for the hard break (callback method) * @param array $matches * @return string */ protected function _doHardBreaks_callback($matches) { return $this->hashPart("empty_element_suffix\n"); } /** * Turn Markdown link shortcuts into XHTML tags. * @param string $text * @return string */ protected function doAnchors($text) { 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 \[ ('.$this->nested_brackets_re.') # link text = $2 \] \( # literal paren [ \n]* (?: <(.+?)> # href = $3 | ('.$this->nested_url_parenthesis_re.') # href = $4 ) [ \n]* ( # $5 ([\'"]) # quote char = $6 (.*?) # Title = $7 \6 # matching quote [ \n]* # ignore any spaces/tabs between closing quote and ) )? # title is optional \) ) }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; } /** * Callback method to parse referenced anchors * @param string $matches * @return string */ protected function _doAnchors_reference_callback($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); $result = "titles[$link_id] ) ) { $title = $this->titles[$link_id]; $title = $this->encodeAttribute($title); $result .= " title=\"$title\""; } $link_text = $this->runSpanGamut($link_text); $result .= ">$link_text"; $result = $this->hashPart($result); } else { $result = $whole_match; } return $result; } /** * Callback method to parse inline anchors * @param string $matches * @return string */ protected function _doAnchors_inline_callback($matches) { $link_text = $this->runSpanGamut($matches[2]); $url = $matches[3] === '' ? $matches[4] : $matches[3]; $title =& $matches[7]; // If the URL was of the form 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); $result = "encodeAttribute($title); $result .= " title=\"$title\""; } $link_text = $this->runSpanGamut($link_text); $result .= ">$link_text"; return $this->hashPart($result); } /** * Turn Markdown image shortcuts into tags. * @param string $text * @return string */ protected function doImages($text) { // First, handle reference-style labeled images: ![alt text][id] $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 \( # literal paren [ \n]* (?: <(\S*)> # src url = $3 | ('.$this->nested_url_parenthesis_re.') # src url = $4 ) [ \n]* ( # $5 ([\'"]) # quote char = $6 (.*?) # title = $7 \6 # matching quote [ \n]* )? # title is optional \) ) }xs', array($this, '_doImages_inline_callback'), $text); return $text; } /** * Callback to parse references image tags * @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]); $result = "\"$alt_text\"";titles[$link_id])) { $title = $this->titles[$link_id]; $title = $this->encodeAttribute($title); $result .= " title=\"$title\""; } $result .= $this->empty_element_suffix; $result = $this->hashPart($result); } else { // If there's no such link ID, leave intact: $result = $whole_match; } return $result; } /** * Callback to parse inline image tags * @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]; $alt_text = $this->encodeAttribute($alt_text); $url = $this->encodeURLAttribute($url); $result = "\"$alt_text\"";encodeAttribute($title); $result .= " title=\"$title\""; // $title already quoted } $result .= $this->empty_element_suffix; return $this->hashPart($result); } /** * Parse Markdown heading elements to HTML * @param string $text * @return string */ protected function doHeaders($text) { /** * Setext-style headers: * Header 1 * ======== * * Header 2 * -------- */ $text = preg_replace_callback('{ ^(.+?)[ ]*\n(=+|-+)[ ]*\n+ }mx', array($this, '_doHeaders_callback_setext'), $text); /** * atx-style headers: * # Header 1 * ## Header 2 * ## Header 2 with closing hashes ## * ... * ###### Header 6 */ $text = preg_replace_callback('{ ^(\#{1,6}) # $1 = string of #\'s [ ]* (.+?) # $2 = Header text [ ]* \#* # optional closing #\'s (not counted) \n+ }xm', array($this, '_doHeaders_callback_atx'), $text); return $text; } /** * Setext header parsing callback * @param array $matches * @return string */ protected function _doHeaders_callback_setext($matches) { // Terrible hack to check we haven't found an empty list item. if ($matches[2] == '-' && preg_match('{^-(?: |$)}', $matches[1])) { return $matches[0]; } $level = $matches[2][0] == '=' ? 1 : 2; // ID attribute generation $idAtt = $this->_generateIdFromHeaderValue($matches[1]); $block = "".$this->runSpanGamut($matches[1]).""; return "\n" . $this->hashBlock($block) . "\n\n"; } /** * ATX header parsing callback * @param array $matches * @return string */ protected function _doHeaders_callback_atx($matches) { // ID attribute generation $idAtt = $this->_generateIdFromHeaderValue($matches[2]); $level = strlen($matches[1]); $block = "".$this->runSpanGamut($matches[2]).""; return "\n" . $this->hashBlock($block) . "\n\n"; } /** * If a header_id_func property is set, we can use it to automatically * generate an id attribute. * * This method returns a string in the form id="foo", or an empty string * otherwise. * @param string $headerValue * @return string */ protected function _generateIdFromHeaderValue($headerValue) { 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) . '"'; } /** * Form HTML ordered (numbered) and unordered (bulleted) lists. * @param string $text * @return string */ protected function doLists($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; } /** * List parsing callback * @param array $matches * @return string */ protected function _doLists_callback($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 . ""); } else { $result = $this->hashBlock("<$list_type>\n" . $result . ""); } return "\n". $result ."\n\n"; } /** * Nesting tracker for list levels * @var integer */ protected $list_level = 0; /** * Process the contents of a single ordered or unordered list, splitting it * into individual list items. * @param string $list_str * @param string $marker_any_re * @return string */ protected function processListItems($list_str, $marker_any_re) { /** * 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.". */ $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; } /** * List item parsing 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 = $this->formParagraphs($item, false); } return "
  • " . $item . "
    • \n"; } /** * Process Markdown `
    ` 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;
	}

	/**
	 * Code block parsing callback
	 * @param  array $matches
	 * @return string
	 */
	protected function _doCodeBlocks_callback($matches) {
		$codeblock = $matches[1];

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

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

		$codeblock = "
    $codeblock\n
    ";
		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) {
		if (is_callable($this->code_span_content_func)) {
			$code = call_user_func($this->code_span_content_func, $code);
		} else {
			$code = htmlspecialchars(trim($code), ENT_NOQUOTES);
		}
		return $this->hashPart("$code");
	}

	/**
	 * Define the emphasis operators with their regex matches
	 * @var array
	 */
	protected $em_relist = array(
		''  => '(?:(? '(? '(? '(?:(? '(? '(? '(?:(? '(? '(?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;
			}
		}
	}

	/**
	 * Convert Markdown italics (emphasis) and bold (strong) to HTML
	 * @param  string $text
	 * @return string
	 */
	protected function doItalicsAndBold($text) {
		if ($this->in_emphasis_processing) {
			return $text; // avoid reentrency
		}
		$this->in_emphasis_processing = true;

		$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);
					$span = "$span";
					$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";
					$text_stack[0] = $this->hashPart($span);
					$$tag = ''; // $$tag stands for $em or $strong
				}
				$tree_char_em = false;
			} else if ($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";
						$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, '');
					$tree_char_em = true;
				}
			} else if ($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);
						$em = '';
					}
					// Closing strong marker:
					array_shift($token_stack);
					$span = array_shift($text_stack);
					$span = $this->runSpanGamut($span);
					$span = "$span";
					$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);
						$span = "$span";
						$text_stack[0] .= $this->hashPart($span);
						$em = '';
					} else {
						$text_stack[0] .= $token;
					}
				} else {
					array_unshift($token_stack, $token);
					array_unshift($text_stack, '');
					$em = $token;
				}
			}
		}
		$this->in_emphasis_processing = false;
		return $text_stack[0];
	}

	/**
	 * Parse Markdown blockquotes to HTML
	 * @param  string $text
	 * @return string
	 */
	protected function doBlockQuotes($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;
	}

	/**
	 * Blockquote parsing callback
	 * @param  array $matches
	 * @return string
	 */
	protected function _doBlockQuotes_callback($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 
     content,
		// so we need to fix that:
		$bq = preg_replace_callback('{(\s*
    .+?
    )}sx',
			array($this, '_doBlockQuotes_callback2'), $bq);

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

	/**
	 * Blockquote parsing callback
	 * @param  array $matches
	 * @return string
	 */
	protected function _doBlockQuotes_callback2($matches) {
		$pre = $matches[1];
		$pre = preg_replace('/^  /m', '', $pre);
		return $pre;
	}

	/**
	 * Parse paragraphs
	 *
	 * @param  string $text String to process in paragraphs
	 * @param  boolean $wrap_in_p Whether paragraphs should be wrapped in 
     tags
	 * @return string
	 */
	protected function formParagraphs($text, $wrap_in_p = true) {
		// 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 
     tags and unhashify HTML blocks
		foreach ($grafs as $key => $value) {
			if (!preg_match('/^B\x1A[0-9]+B$/', $value)) {
				// Is a paragraph.
				$value = $this->runSpanGamut($value);
				if ($wrap_in_p) {
					$value = preg_replace('/^([ ]*)/', "
    ", $value);
					$value .= "
    ";
				}
				$grafs[$key] = $this->unhash($value);
			} else {
				// Is a block.
				// Modify elements of @grafs in-place...
				$graf = $value;
				$block = $this->html_hashes[$graf];
				$graf = $block;
//				if (preg_match('{
//					\A
//					(							# $1 = 
     tag
//					  
    ]*
//					  \b
//					  markdown\s*=\s*  ([\'"])	#	$2 = attr quote char
//					  1
//					  \2
//					  [^>]*
//					  >
//					)
//					(							# $3 = contents
//					.*
//					)
//					(
    )					# $4 = closing tag
//					\z
//					}xs', $block, $matches))
//				{
//					list(, $div_open, , $div_content, $div_close) = $matches;
//
//					// We can't call Markdown(), because that resets the hash;
//					// that initialization code should be pulled into its own sub, though.
//					$div_content = $this->hashHTMLBlocks($div_content);
//
//					// Run document gamut methods on the content.
//					foreach ($this->document_gamut as $method => $priority) {
//						$div_content = $this->$method($div_content);
//					}
//
//					$div_open = preg_replace(
//						'{\smarkdown\s*=\s*([\'"]).+?\1}', '', $div_open);
//
//					$graf = $div_open . "\n" . $div_content . "\n" . $div_close;
//				}
				$grafs[$key] = $graf;
			}
		}

		return implode("\n\n", $grafs);
	}

	/**
	 * 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('"', '"', $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 $text Passed by reference
	 * @return string        URL
	 */
	protected function encodeURLAttribute($url, &$text = null) {
		if (is_callable($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);
		} else if (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('&', '&', $text);
		} else {
			// Ampersand-encoding based entirely on Nat Irons's Amputator
			// MT plugin: 
			$text = preg_replace('/&(?!#?[xX]?(?:[0-9a-fA-F]+|\w+);)/',
								'&', $text);
		}
		// Encode remaining <'s
		$text = str_replace('<', '<', $text);

		return $text;
	}

	/**
	 * Parse Markdown automatic links to anchor HTML tags
	 * @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: 
		$text = preg_replace_callback('{
			<
			(?:mailto:)?
			(
				(?:
					[-!#$%&\'*+/=?^_`.{|}~\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;
	}

	/**
	 * Parse URL callback
	 * @param  array $matches
	 * @return string
	 */
	protected function _doAutoLinks_url_callback($matches) {
		$url = $this->encodeURLAttribute($matches[1], $text);
		$link = "$text";
		return $this->hashPart($link);
	}

	/**
	 * Parse email address callback
	 * @param  array $matches
	 * @return string
	 */
	protected function _doAutoLinks_email_callback($matches) {
		$addr = $matches[1];
		$url = $this->encodeURLAttribute("mailto:$addr", $text);
		$link = "$text";
		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.:
	 *
	 *        mailto:foo
	 *        @example.co
	 *        m
	 *
	 * 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 Passed by reference
	 * @param  integer $head_length
	 * @return string
	 */
	protected function encodeEntityObfuscatedAttribute($text, &$tail = null, $head_length = 0) {
		if ($text == "") {
			return $tail = "";
		}

		$chars = preg_split('/(? $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('@"&>', $char) === false) {
					/* do nothing */
				} else if ($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 embeded HTML,
	 * escaped characters and handling code spans.
	 * @param  string $str
	 * @return string
	 */
	protected function parseSpan($str) {
		$output = '';

		$span_re = '{
				(
					\\\\'.$this->escape_chars_re.'
				|
					(?no_markup ? '' : '
				|
							# comment
				|
					<\?.*?\?> | <%.*?%>		# processing instruction
				|
					<[!$]?[-a-zA-Z0-9:_]+	# regular tags
					(?>
						\s
						(?>[^"\'>]+|"[^"]*"|\'[^\']*\')*
					)?
					>
				|
					<[-a-zA-Z0-9:_]+\s*/> # xml-style empty tag
				|
					 # closing tag
			').'
				)
				}xs';

		while (1) {
			// Each loop iteration seach for either the next tag, the next
			// openning 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  string $token
	 * @param  string $str Passed by reference
	 * @return string
	 */
	protected function handleSpanToken($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);
	}


	/**
	 * 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';

	/**
	 * Replace tabs with the appropriate amount of spaces.
	 *
	 * For each line we separate the line in blocks delemited 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;
	}

	/**
	 * Replace tabs callback
	 * @param  string $matches
	 * @return string
	 */
	protected function _detab_callback($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;
		}

		$this->utf8_strlen = function($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);
	}

	/**
	 * Unhashing callback
	 * @param  array $matches
	 * @return string
	 */
	protected function _unhash_callback($matches) {
		return $this->html_hashes[$matches[0]];
	}
}