Dropped Markdown for Parsedown

2 files changed, 1155 insertions, 0 deletions

diff --git a/framework/3rdParty/Parsedown/LICENSE.txt b/framework/3rdParty/Parsedown/LICENSE.txt
new file mode 100644
index 00000000..baca86f5
--- /dev/null
+++ b/framework/3rdParty/Parsedown/LICENSE.txt
@@ -0,0 +1,20 @@
+The MIT License (MIT)
+
+Copyright (c) 2013 Emanuil Rusev, erusev.com
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
\ No newline at end of file
diff --git a/framework/3rdParty/Parsedown/Parsedown.php b/framework/3rdParty/Parsedown/Parsedown.php
new file mode 100755
index 00000000..ebc80974
--- /dev/null
+++ b/framework/3rdParty/Parsedown/Parsedown.php
@@ -0,0 +1,1135 @@
+<?php
+
+#
+#
+# Parsedown
+# http://parsedown.org
+#
+# (c) Emanuil Rusev
+# http://erusev.com
+#
+# For the full license information, view the LICENSE file that was distributed
+# with this source code.
+#
+#
+
+class Parsedown
+{
+    # Multiton
+
+    static function instance($name = 'default')
+    {
+        if (isset(self::$instances[$name]))
+        {
+            return self::$instances[$name];
+        }
+
+        $instance = new Parsedown();
+
+        self::$instances[$name] = $instance;
+
+        return $instance;
+    }
+
+    private static $instances = array();
+
+    #
+    # Setters
+    #
+
+    # Enables GFM line breaks.
+
+    function set_breaks_enabled($breaks_enabled)
+    {
+        $this->breaks_enabled = $breaks_enabled;
+
+        return $this;
+    }
+
+    private $breaks_enabled = false;
+
+    #
+    # Synopsis
+    #
+
+    # Markdown is intended to be easy-to-read by humans - those of us who read
+    # line by line, left to right, top to bottom. In order to take advantage of
+    # this, Parsedown tries to read in a similar way. It breaks texts into
+    # lines, it iterates through them and it looks at how they start and relate
+    # to each other.
+
+    #
+    # Methods
+    #
+
+    function parse($text)
+    {
+        # standardize line breaks
+        $text = str_replace("\r\n", "\n", $text);
+        $text = str_replace("\r", "\n", $text);
+
+        # replace tabs with spaces
+        $text = str_replace("\t", '    ', $text);
+
+        # remove surrounding line breaks
+        $text = trim($text, "\n");
+
+        # split text into lines
+        $lines = explode("\n", $text);
+
+        # convert lines into html
+        $text = $this->parse_block_elements($lines);
+
+        # remove trailing line breaks
+        $text = chop($text, "\n");
+
+        return $text;
+    }
+
+    #
+    # Private
+
+    private function parse_block_elements(array $lines, $context = '')
+    {
+        $blocks = array();
+
+        $block = array(
+            'type' => '',
+        );
+
+        foreach ($lines as $line)
+        {
+            # context
+
+            switch ($block['type'])
+            {
+                case 'fenced':
+
+                    if ( ! isset($block['closed']))
+                    {
+                        if (preg_match('/^[ ]*'.$block['fence'][0].'{3,}[ ]*$/', $line))
+                        {
+                            $block['closed'] = true;
+                        }
+                        else
+                        {
+                            if ($block['text'] !== '')
+                            {
+                                $block['text'] .= "\n";
+                            }
+
+                            $block['text'] .= $line;
+                        }
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case 'markup':
+
+                    if ( ! isset($block['closed']))
+                    {
+                        if (strpos($line, $block['start']) !== false) # opening tag
+                        {
+                            $block['depth']++;
+                        }
+
+                        if (strpos($line, $block['end']) !== false) # closing tag
+                        {
+                            if ($block['depth'] > 0)
+                            {
+                                $block['depth']--;
+                            }
+                            else
+                            {
+                                $block['closed'] = true;
+                            }
+                        }
+
+                        $block['text'] .= "\n".$line;
+
+                        continue 2;
+                    }
+
+                    break;
+            }
+
+            # ~
+
+            $indentation = 0;
+
+            while(isset($line[$indentation]) and $line[$indentation] === ' ')
+            {
+                $indentation++;
+            }
+
+            $outdented_line = $indentation > 0 ? ltrim($line) : $line;
+
+            # blank
+
+            if ($outdented_line === '')
+            {
+                $block['interrupted'] = true;
+
+                continue;
+            }
+
+            # context
+
+            switch ($block['type'])
+            {
+                case 'quote':
+
+                    if ( ! isset($block['interrupted']))
+                    {
+                        $line = preg_replace('/^[ ]*>[ ]?/', '', $line);
+
+                        $block['lines'] []= $line;
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case 'li':
+
+                    if ($block['indentation'] === $indentation and preg_match('/^'.$block['marker'].'[ ]+(.*)/', $outdented_line, $matches))
+                    {
+                        unset($block['last']);
+
+                        $blocks []= $block;
+
+                        $block['last'] = true;
+                        $block['lines'] = array($matches[1]);
+
+                        unset($block['first']);
+                        unset($block['interrupted']);
+
+                        continue 2;
+                    }
+
+                    if ( ! isset($block['interrupted']))
+                    {
+                        $line = preg_replace('/^[ ]{0,'.$block['baseline'].'}/', '', $line);
+
+                        $block['lines'] []= $line;
+
+                        continue 2;
+                    }
+                    elseif ($line[0] === ' ')
+                    {
+                        $block['lines'] []= '';
+
+                        $line = preg_replace('/^[ ]{0,'.$block['baseline'].'}/', '', $line);
+
+                        $block['lines'] []= $line;
+
+                        unset($block['interrupted']);
+
+                        continue 2;
+                    }
+
+                    break;
+            }
+
+            # indentation sensitive types
+
+            switch ($line[0])
+            {
+                case ' ':
+
+                    # code
+
+                    if ($indentation >= 4)
+                    {
+                        $code_line = substr($line, 4);
+
+                        if ($block['type'] === 'code')
+                        {
+                            if (isset($block['interrupted']))
+                            {
+                                $block['text'] .= "\n";
+
+                                unset($block['interrupted']);
+                            }
+
+                            $block['text'] .= "\n".$code_line;
+                        }
+                        else
+                        {
+                            $blocks []= $block;
+
+                            $block = array(
+                                'type' => 'code',
+                                'text' => $code_line,
+                            );
+                        }
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case '#':
+
+                    # atx heading (#)
+
+                    if (isset($line[1]))
+                    {
+                        $blocks []= $block;
+
+                        $level = 1;
+
+                        while (isset($line[$level]) and $line[$level] === '#')
+                        {
+                            $level++;
+                        }
+
+                        $block = array(
+                            'type' => 'heading',
+                            'text' => trim($line, '# '),
+                            'level' => $level,
+                        );
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case '-':
+                case '=':
+
+                    # setext heading (===)
+
+                    if ($block['type'] === 'paragraph' and isset($block['interrupted']) === false)
+                    {
+                        $chopped_line = chop($line);
+
+                        $i = 1;
+
+                        while (isset($chopped_line[$i]))
+                        {
+                            if ($chopped_line[$i] !== $line[0])
+                            {
+                                break 2;
+                            }
+
+                            $i++;
+                        }
+
+                        $block['type'] = 'heading';
+
+                        $block['level'] = $line[0] === '-' ? 2 : 1;
+
+                        continue 2;
+                    }
+
+                    break;
+            }
+
+            # indentation insensitive types
+
+            switch ($outdented_line[0])
+            {
+                case '<':
+
+                    $position = strpos($outdented_line, '>');
+
+                    if ($position > 1)
+                    {
+                        $substring = substr($outdented_line, 1, $position - 1);
+
+                        $substring = chop($substring);
+
+                        if (substr($substring, -1) === '/')
+                        {
+                            $is_self_closing = true;
+
+                            $substring = substr($substring, 0, -1);
+                        }
+
+                        $position = strpos($substring, ' ');
+
+                        if ($position)
+                        {
+                            $name = substr($substring, 0, $position);
+                        }
+                        else
+                        {
+                            $name = $substring;
+                        }
+
+                        if ( ! ctype_alpha($name))
+                        {
+                            break;
+                        }
+
+                        if (in_array($name, self::$text_level_elements))
+                        {
+                            break;
+                        }
+
+                        $blocks []= $block;
+
+                        if (isset($is_self_closing))
+                        {
+                            $block = array(
+                                'type' => 'self-closing tag',
+                                'text' => $outdented_line,
+                            );
+
+                            unset($is_self_closing);
+
+                            continue 2;
+                        }
+
+                        $block = array(
+                            'type' => 'markup',
+                            'text' => $outdented_line,
+                            'start' => '<'.$name.'>',
+                            'end' => '</'.$name.'>',
+                            'depth' => 0,
+                        );
+
+                        if (strpos($outdented_line, $block['end']))
+                        {
+                            $block['closed'] = true;
+                        }
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case '>':
+
+                    # quote
+
+                    if (preg_match('/^>[ ]?(.*)/', $outdented_line, $matches))
+                    {
+                        $blocks []= $block;
+
+                        $block = array(
+                            'type' => 'quote',
+                            'lines' => array(
+                                $matches[1],
+                            ),
+                        );
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case '[':
+
+                    # reference
+
+                    $position = strpos($outdented_line, ']:');
+
+                    if ($position)
+                    {
+                        $reference = array();
+
+                        $label = substr($outdented_line, 1, $position - 1);
+                        $label = strtolower($label);
+
+                        $substring = substr($outdented_line, $position + 2);
+                        $substring = trim($substring);
+
+                        if ($substring === '')
+                        {
+                            break;
+                        }
+
+                        if ($substring[0] === '<')
+                        {
+                            $position = strpos($substring, '>');
+
+                            if ($position === false)
+                            {
+                                break;
+                            }
+
+                            $reference['»'] = substr($substring, 1, $position - 1);
+
+                            $substring = substr($substring, $position + 1);
+                        }
+                        else
+                        {
+                            $position = strpos($substring, ' ');
+
+                            if ($position === false)
+                            {
+                                $reference['»'] = $substring;
+
+                                $substring = false;
+                            }
+                            else
+                            {
+                                $reference['»'] = substr($substring, 0, $position);
+
+                                $substring = substr($substring, $position + 1);
+                            }
+                        }
+
+                        if ($substring !== false)
+                        {
+                            if ($substring[0] !== '"' and $substring[0] !== "'" and $substring[0] !== '(')
+                            {
+                                break;
+                            }
+
+                            $last_char = substr($substring, -1);
+
+                            if ($last_char !== '"' and $last_char !== "'" and $last_char !== ')')
+                            {
+                                break;
+                            }
+
+                            $reference['#'] = substr($substring, 1, -1);
+                        }
+
+                        $this->reference_map[$label] = $reference;
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case '`':
+                case '~':
+
+                    # fenced code block
+
+                    if (preg_match('/^([`]{3,}|[~]{3,})[ ]*(\S+)?[ ]*$/', $outdented_line, $matches))
+                    {
+                        $blocks []= $block;
+
+                        $block = array(
+                            'type' => 'fenced',
+                            'text' => '',
+                            'fence' => $matches[1],
+                        );
+
+                        if (isset($matches[2]))
+                        {
+                            $block['language'] = $matches[2];
+                        }
+
+                        continue 2;
+                    }
+
+                    break;
+
+                case '*':
+                case '+':
+                case '-':
+                case '_':
+
+                    # hr
+
+                    if (preg_match('/^([-*_])([ ]{0,2}\1){2,}[ ]*$/', $outdented_line))
+                    {
+                        $blocks []= $block;
+
+                        $block = array(
+                            'type' => 'rule',
+                        );
+
+                        continue 2;
+                    }
+
+                    # li
+
+                    if (preg_match('/^([*+-][ ]+)(.*)/', $outdented_line, $matches))
+                    {
+                        $blocks []= $block;
+
+                        $baseline = $indentation + strlen($matches[1]);
+
+                        $block = array(
+                            'type' => 'li',
+                            'indentation' => $indentation,
+                            'baseline' => $baseline,
+                            'marker' => '[*+-]',
+                            'first' => true,
+                            'last' => true,
+                            'lines' => array(),
+                        );
+
+                        $block['lines'] []= preg_replace('/^[ ]{0,4}/', '', $matches[2]);
+
+                        continue 2;
+                    }
+            }
+
+            # li
+
+            if ($outdented_line[0] <= '9' and preg_match('/^(\d+[.][ ]+)(.*)/', $outdented_line, $matches))
+            {
+                $blocks []= $block;
+
+                $baseline = $indentation + strlen($matches[1]);
+
+                $block = array(
+                    'type' => 'li',
+                    'indentation' => $indentation,
+                    'baseline' => $baseline,
+                    'marker' => '\d+[.]',
+                    'first' => true,
+                    'last' => true,
+                    'ordered' => true,
+                    'lines' => array(),
+                );
+
+                $block['lines'] []= preg_replace('/^[ ]{0,4}/', '', $matches[2]);
+
+                continue;
+            }
+
+            # paragraph
+
+            if ($block['type'] === 'paragraph')
+            {
+                if (isset($block['interrupted']))
+                {
+                    $blocks []= $block;
+
+                    $block['text'] = $line;
+
+                    unset($block['interrupted']);
+                }
+                else
+                {
+                    if ($this->breaks_enabled)
+                    {
+                        $block['text'] .= '  ';
+                    }
+
+                    $block['text'] .= "\n".$line;
+                }
+            }
+            else
+            {
+                $blocks []= $block;
+
+                $block = array(
+                    'type' => 'paragraph',
+                    'text' => $line,
+                );
+            }
+        }
+
+        $blocks []= $block;
+
+        unset($blocks[0]);
+
+        # $blocks » HTML
+
+        $markup = '';
+
+        foreach ($blocks as $block)
+        {
+            switch ($block['type'])
+            {
+                case 'paragraph':
+
+                    $text = $this->parse_span_elements($block['text']);
+
+                    if ($context === 'li' and $markup === '')
+                    {
+                        if (isset($block['interrupted']))
+                        {
+                            $markup .= "\n".'<p>'.$text.'</p>'."\n";
+                        }
+                        else
+                        {
+                            $markup .= $text;
+
+                            if (isset($blocks[2]))
+                            {
+                                $markup .= "\n";
+                            }
+                        }
+                    }
+                    else
+                    {
+                        $markup .= '<p>'.$text.'</p>'."\n";
+                    }
+
+                    break;
+
+                case 'quote':
+
+                    $text = $this->parse_block_elements($block['lines']);
+
+                    $markup .= '<blockquote>'."\n".$text.'</blockquote>'."\n";
+
+                    break;
+
+                case 'code':
+
+                    $text = htmlspecialchars($block['text'], ENT_NOQUOTES, 'UTF-8');
+
+                    $markup .= '<pre><code>'.$text.'</code></pre>'."\n";
+
+                    break;
+
+                case 'fenced':
+
+                    $text = htmlspecialchars($block['text'], ENT_NOQUOTES, 'UTF-8');
+
+                    $markup .= '<pre><code';
+
+                    if (isset($block['language']))
+                    {
+                        $markup .= ' class="language-'.$block['language'].'"';
+                    }
+
+                    $markup .= '>'.$text.'</code></pre>'."\n";
+
+                    break;
+
+                case 'heading':
+
+                    $text = $this->parse_span_elements($block['text']);
+
+                    $markup .= '<h'.$block['level'].'>'.$text.'</h'.$block['level'].'>'."\n";
+
+                    break;
+
+                case 'rule':
+
+                    $markup .= '<hr />'."\n";
+
+                    break;
+
+                case 'li':
+
+                    if (isset($block['first']))
+                    {
+                        $type = isset($block['ordered']) ? 'ol' : 'ul';
+
+                        $markup .= '<'.$type.'>'."\n";
+                    }
+
+                    if (isset($block['interrupted']) and ! isset($block['last']))
+                    {
+                        $block['lines'] []= '';
+                    }
+
+                    $text = $this->parse_block_elements($block['lines'], 'li');
+
+                    $markup .= '<li>'.$text.'</li>'."\n";
+
+                    if (isset($block['last']))
+                    {
+                        $type = isset($block['ordered']) ? 'ol' : 'ul';
+
+                        $markup .= '</'.$type.'>'."\n";
+                    }
+
+                    break;
+
+                case 'markup':
+
+                    $markup .= $block['text']."\n";
+
+                    break;
+
+                default:
+
+                    $markup .= $block['text']."\n";
+            }
+        }
+
+        return $markup;
+    }
+
+    private function parse_span_elements($text, $markers = array("  \n", '![', '&', '*', '<', '[', '\\', '_', '`', 'http', '~~'))
+    {
+        if (isset($text[1]) === false or $markers === array())
+        {
+            return $text;
+        }
+
+        # ~
+
+        $markup = '';
+
+        while ($markers)
+        {
+            $closest_marker = null;
+            $closest_marker_index = 0;
+            $closest_marker_position = null;
+
+            foreach ($markers as $index => $marker)
+            {
+                $marker_position = strpos($text, $marker);
+
+                if ($marker_position === false)
+                {
+                    unset($markers[$index]);
+
+                    continue;
+                }
+
+                if ($closest_marker === null or $marker_position < $closest_marker_position)
+                {
+                    $closest_marker = $marker;
+                    $closest_marker_index = $index;
+                    $closest_marker_position = $marker_position;
+                }
+            }
+
+            # ~
+
+            if ($closest_marker === null or isset($text[$closest_marker_position + 1]) === false)
+            {
+                $markup .= $text;
+
+                break;
+            }
+            else
+            {
+                $markup .= substr($text, 0, $closest_marker_position);
+            }
+
+            $text = substr($text, $closest_marker_position);
+
+            # ~
+
+            unset($markers[$closest_marker_index]);
+
+            # ~
+
+            switch ($closest_marker)
+            {
+                case "  \n":
+
+                    $markup .= '<br />'."\n";
+
+                    $offset = 3;
+
+                    break;
+
+                case '![':
+                case '[':
+
+                    if (strpos($text, ']') and preg_match('/\[((?:[^][]|(?R))*)\]/', $text, $matches))
+                    {
+                        $element = array(
+                            '!' => $text[0] === '!',
+                            'a' => $matches[1],
+                        );
+
+                        $offset = strlen($matches[0]);
+
+                        if ($element['!'])
+                        {
+                            $offset++;
+                        }
+
+                        $remaining_text = substr($text, $offset);
+
+                        if ($remaining_text[0] === '(' and preg_match('/\([ ]*(.*?)(?:[ ]+[\'"](.+?)[\'"])?[ ]*\)/', $remaining_text, $matches))
+                        {
+                            $element['»'] = $matches[1];
+
+                            if (isset($matches[2]))
+                            {
+                                $element['#'] = $matches[2];
+                            }
+
+                            $offset += strlen($matches[0]);
+                        }
+                        elseif ($this->reference_map)
+                        {
+                            $reference = $element['a'];
+
+                            if (preg_match('/^\s*\[(.*?)\]/', $remaining_text, $matches))
+                            {
+                                $reference = $matches[1] ? $matches[1] : $element['a'];
+
+                                $offset += strlen($matches[0]);
+                            }
+
+                            $reference = strtolower($reference);
+
+                            if (isset($this->reference_map[$reference]))
+                            {
+                                $element['»'] = $this->reference_map[$reference]['»'];
+
+                                if (isset($this->reference_map[$reference]['#']))
+                                {
+                                    $element['#'] = $this->reference_map[$reference]['#'];
+                                }
+                            }
+                            else
+                            {
+                                unset($element);
+                            }
+                        }
+                        else
+                        {
+                            unset($element);
+                        }
+                    }
+
+                    if (isset($element))
+                    {
+                        $element['»'] = str_replace('&', '&amp;', $element['»']);
+                        $element['»'] = str_replace('<', '&lt;', $element['»']);
+
+                        if ($element['!'])
+                        {
+                            $markup .= '<img alt="'.$element['a'].'" src="'.$element['»'].'"';
+
+                            if (isset($element['#']))
+                            {
+                                $markup .= ' title="'.$element['#'].'"';
+                            }
+
+                            $markup .= ' />';
+                        }
+                        else
+                        {
+                            $element['a'] = $this->parse_span_elements($element['a'], $markers);
+
+                            $markup .= '<a href="'.$element['»'].'"';
+
+                            if (isset($element['#']))
+                            {
+                                $markup .= ' title="'.$element['#'].'"';
+                            }
+
+                            $markup .= '>'.$element['a'].'</a>';
+                        }
+
+                        unset($element);
+                    }
+                    else
+                    {
+                        $markup .= $closest_marker;
+
+                        $offset = $closest_marker === '![' ? 2 : 1;
+                    }
+
+                    break;
+
+                case '&':
+
+                    if (preg_match('/^&#?\w+;/', $text, $matches))
+                    {
+                        $markup .= $matches[0];
+
+                        $offset = strlen($matches[0]);
+                    }
+                    else
+                    {
+                        $markup .= '&amp;';
+
+                        $offset = 1;
+                    }
+
+                    break;
+
+                case '*':
+                case '_':
+
+                    if ($text[1] === $closest_marker and preg_match(self::$strong_regex[$closest_marker], $text, $matches))
+                    {
+                        $markers[] = $closest_marker;
+                        $matches[1] = $this->parse_span_elements($matches[1], $markers);
+
+                        $markup .= '<strong>'.$matches[1].'</strong>';
+                    }
+                    elseif (preg_match(self::$em_regex[$closest_marker], $text, $matches))
+                    {
+                        $markers[] = $closest_marker;
+                        $matches[1] = $this->parse_span_elements($matches[1], $markers);
+
+                        $markup .= '<em>'.$matches[1].'</em>';
+                    }
+
+                    if (isset($matches) and $matches)
+                    {
+                        $offset = strlen($matches[0]);
+                    }
+                    else
+                    {
+                        $markup .= $closest_marker;
+
+                        $offset = 1;
+                    }
+
+                    break;
+
+                case '<':
+
+                    if (strpos($text, '>') !== false)
+                    {
+                        if ($text[1] === 'h' and preg_match('/^<(https?:[\/]{2}[^\s]+?)>/i', $text, $matches))
+                        {
+                            $element_url = $matches[1];
+                            $element_url = str_replace('&', '&amp;', $element_url);
+                            $element_url = str_replace('<', '&lt;', $element_url);
+
+                            $markup .= '<a href="'.$element_url.'">'.$element_url.'</a>';
+
+                            $offset = strlen($matches[0]);
+                        }
+                        elseif (strpos($text, '@') > 1 and preg_match('/<(\S+?@\S+?)>/', $text, $matches))
+                        {
+                            $markup .= '<a href="mailto:'.$matches[1].'">'.$matches[1].'</a>';
+
+                            $offset = strlen($matches[0]);
+                        }
+                        elseif (preg_match('/^<\/?\w.*?>/', $text, $matches))
+                        {
+                            $markup .= $matches[0];
+
+                            $offset = strlen($matches[0]);
+                        }
+                        else
+                        {
+                            $markup .= '&lt;';
+
+                            $offset = 1;
+                        }
+                    }
+                    else
+                    {
+                        $markup .= '&lt;';
+
+                        $offset = 1;
+                    }
+
+                    break;
+
+                case '\\':
+
+                    if (in_array($text[1], self::$special_characters))
+                    {
+                        $markup .= $text[1];
+
+                        $offset = 2;
+                    }
+                    else
+                    {
+                        $markup .= '\\';
+
+                        $offset = 1;
+                    }
+
+                    break;
+
+                case '`':
+
+                    if (preg_match('/^(`+)[ ]*(.+?)[ ]*(?<!`)\1(?!`)/', $text, $matches))
+                    {
+                        $element_text = $matches[2];
+                        $element_text = htmlspecialchars($element_text, ENT_NOQUOTES, 'UTF-8');
+
+                        $markup .= '<code>'.$element_text.'</code>';
+
+                        $offset = strlen($matches[0]);
+                    }
+                    else
+                    {
+                        $markup .= '`';
+
+                        $offset = 1;
+                    }
+
+                    break;
+
+                case 'http':
+
+                    if (preg_match('/^https?:[\/]{2}[^\s]+\b\/*/ui', $text, $matches))
+                    {
+                        $element_url = $matches[0];
+                        $element_url = str_replace('&', '&amp;', $element_url);
+                        $element_url = str_replace('<', '&lt;', $element_url);
+
+                        $markup .= '<a href="'.$element_url.'">'.$element_url.'</a>';
+
+                        $offset = strlen($matches[0]);
+                    }
+                    else
+                    {
+                        $markup .= 'http';
+
+                        $offset = 4;
+                    }
+
+                    break;
+
+                case '~~':
+
+                    if (preg_match('/^~~(?=\S)(.+?)(?<=\S)~~/', $text, $matches))
+                    {
+                        $matches[1] = $this->parse_span_elements($matches[1], $markers);
+
+                        $markup .= '<del>'.$matches[1].'</del>';
+
+                        $offset = strlen($matches[0]);
+                    }
+                    else
+                    {
+                        $markup .= '~~';
+
+                        $offset = 2;
+                    }
+
+                    break;
+            }
+
+            if (isset($offset))
+            {
+                $text = substr($text, $offset);
+            }
+
+            $markers[$closest_marker_index] = $closest_marker;
+        }
+
+        return $markup;
+    }
+
+    #
+    # Fields
+    #
+
+    private $reference_map = array();
+
+    #
+    # Read-only
+
+    private static $strong_regex = array(
+        '*' => '/^[*]{2}((?:[^*]|[*][^*]*[*])+?)[*]{2}(?![*])/s',
+        '_' => '/^__((?:[^_]|_[^_]*_)+?)__(?!_)/us',
+    );
+
+    private static $em_regex = array(
+        '*' => '/^[*]((?:[^*]|[*][*][^*]+?[*][*])+?)[*](?![*])/s',
+        '_' => '/^_((?:[^_]|__[^_]*__)+?)_(?!_)\b/us',
+    );
+
+    private static $special_characters = array(
+        '\\', '`', '*', '_', '{', '}', '[', ']', '(', ')', '>', '#', '+', '-', '.', '!',
+    );
+
+    private static $text_level_elements = array(
+        'a', 'br', 'bdo', 'abbr', 'blink', 'nextid', 'acronym', 'basefont',
+        'b', 'em', 'big', 'cite', 'small', 'spacer', 'listing',
+        'i', 'rp', 'sub', 'code',          'strike', 'marquee',
+        'q', 'rt', 'sup', 'font',          'strong',
+        's', 'tt', 'var', 'mark',
+        'u', 'xm', 'wbr', 'nobr',
+                          'ruby',
+                          'span',
+                          'time',
+    );
+}