<?php

#
#
# Parsedown
# http://parsedown.org
#
# (c) Emanuil Rusev
# http://erusev.com
#
# For the full license information, please view the LICENSE file that was
# distributed with this source code.
#
#

class Parsedown
{
	#
	# Multiton (http://en.wikipedia.org/wiki/Multiton_pattern)
	#

	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
	#

	private $break_marker = "  \n";

	function set_breaks_enabled($breaks_enabled)
	{
		$this->break_marker = $breaks_enabled ? "\n" : "  \n";

		return $this;
	}

	#
	# Fields
	#

	private $reference_map = array();

	#
	# Public Methods
	#

	function parse($text)
	{
		# removes \r characters
		$text = str_replace("\r\n", "\n", $text);
		$text = str_replace("\r", "\n", $text);

		# replaces tabs with spaces
		$text = str_replace("\t", '    ', $text);

		# ~

		$text = trim($text, "\n");

		$lines = explode("\n", $text);

		$text = $this->parse_block_elements($lines);

		$text = rtrim($text, "\n");

		return $text;
	}

	#
	# Private Methods
	#

	private function parse_block_elements(array $lines, $context = '')
	{
		$elements = array();

		$element = array(
			'type' => '',
		);

		foreach ($lines as $line)
		{
			# fenced elements

			switch ($element['type'])
			{
				case 'fenced block':

					if ( ! isset($element['closed']))
					{
						if (preg_match('/^[ ]*'.$element['fence'][0].'{3,}[ ]*$/', $line))
						{
							$element['closed'] = true;
						}
						else
						{
							$element['text'] !== '' and $element['text'] .= "\n";

							$element['text'] .= $line;
						}

						continue 2;
					}

					break;

				case 'block-level markup':

					if ( ! isset($element['closed']))
					{
						if (strpos($line, $element['start']) !== false) # opening tag
						{
							$element['depth']++;
						}

						if (strpos($line, $element['end']) !== false) # closing tag
						{
							$element['depth'] > 0
								? $element['depth']--
								: $element['closed'] = true;
						}

						$element['text'] .= "\n".$line;

						continue 2;
					}

					break;
			}

			# *

			$deindented_line = ltrim($line);

			if ($deindented_line === '')
			{
				$element['interrupted'] = true;

				continue;
			}

			# composite elements

			switch ($element['type'])
			{
				case 'blockquote':

					if ( ! isset($element['interrupted']))
					{
						$line = preg_replace('/^[ ]*>[ ]?/', '', $line);

						$element['lines'] []= $line;

						continue 2;
					}

					break;

				case 'li':

					if (preg_match('/^([ ]{0,3})(\d+[.]|[*+-])[ ](.*)/', $line, $matches))
					{
						if ($element['indentation'] !== $matches[1])
						{
							$element['lines'] []= $line;
						}
						else
						{
							unset($element['last']);

							$elements []= $element;

							$element = array(
								'type' => 'li',
								'indentation' => $matches[1],
								'last' => true,
								'lines' => array(
									preg_replace('/^[ ]{0,4}/', '', $matches[3]),
								),
							);
						}

						continue 2;
					}

					if (isset($element['interrupted']))
					{
						if ($line[0] === ' ')
						{
							$element['lines'] []= '';

							$line = preg_replace('/^[ ]{0,4}/', '', $line);

							$element['lines'] []= $line;

							unset($element['interrupted']);

							continue 2;
						}
					}
					else
					{
						$line = preg_replace('/^[ ]{0,4}/', '', $line);

						$element['lines'] []= $line;

						continue 2;
					}

					break;
			}

			# indentation sensitive types

			switch ($line[0])
			{
				case ' ':

					# code block

					if (isset($line[3]) and $line[3] === ' ' and $line[2] === ' ' and $line[1] === ' ')
					{
						$code_line = substr($line, 4);

						if ($element['type'] === 'code block')
						{
							if (isset($element['interrupted']))
							{
								$element['text'] .= "\n";

								unset ($element['interrupted']);
							}

							$element['text'] .= "\n".$code_line;
						}
						else
						{
							$elements []= $element;

							$element = array(
								'type' => 'code block',
								'text' => $code_line,
							);
						}

						continue 2;
					}

					break;

				case '#':

					# atx heading (#)

					if (isset($line[1]))
					{
						$elements []= $element;

						$level = 1;

						while (isset($line[$level]) and $line[$level] === '#')
						{
							$level++;
						}

						$element = array(
							'type' => 'heading',
							'text' => trim($line, '# '),
							'level' => $level,
						);

						continue 2;
					}

					break;

				case '-':
				case '=':

					# setext heading

					if ($element['type'] === 'paragraph' and isset($element['interrupted']) === false)
					{
						$chopped_line = rtrim($line);

						$i = 1;

						while (isset($chopped_line[$i]))
						{
							if ($chopped_line[$i] !== $line[0])
							{
								break 2;
							}

							$i++;
						}

						$element['type'] = 'heading';
						$element['level'] = $line[0] === '-' ? 2 : 1;

						continue 2;
					}

					break;
			}

			# indentation insensitive types

			switch ($deindented_line[0])
			{
				case '<':

					$position = strpos($deindented_line, '>');

					if ($position > 1) # tag
					{
						$name = substr($deindented_line, 1, $position - 1);
						$name = rtrim($name);

						if (substr($name, -1) === '/')
						{
							$self_closing = true;

							$name = substr($name, 0, -1);
						}

						$position = strpos($name, ' ');

						if ($position)
						{
							$name = substr($name, 0, $position);
						}

						if ( ! ctype_alpha($name))
						{
							break;
						}

						if (in_array($name, $this->inline_tags))
						{
							break;
						}

						$elements []= $element;

						if (isset($self_closing))
						{
							$element = array(
								'type' => 'self-closing tag',
								'text' => $deindented_line,
							);

							unset($self_closing);

							continue 2;
						}

						$element = array(
							'type' => 'block-level markup',
							'text' => $deindented_line,
							'start' => '<'.$name.'>',
							'end' => '</'.$name.'>',
							'depth' => 0,
						);

						if (strpos($deindented_line, $element['end']))
						{
							$element['closed'] = true;
						}

						continue 2;
					}

					break;

				case '>':

					# quote

					if (preg_match('/^>[ ]?(.*)/', $deindented_line, $matches))
					{
						$elements []= $element;

						$element = array(
							'type' => 'blockquote',
							'lines' => array(
								$matches[1],
							),
						);

						continue 2;
					}

					break;

				case '[':

					# reference

					if (preg_match('/^\[(.+?)\]:[ ]*(.+?)(?:[ ]+[\'"](.+?)[\'"])?[ ]*$/', $deindented_line, $matches))
					{
						$label = strtolower($matches[1]);

						$this->reference_map[$label] = array(
							'»' => trim($matches[2], '<>'),
						);

						if (isset($matches[3]))
						{
							$this->reference_map[$label]['#'] = $matches[3];
						}

						continue 2;
					}

					break;

				case '`':
				case '~':

					# fenced code block

					if (preg_match('/^([`]{3,}|[~]{3,})[ ]*(\S+)?[ ]*$/', $deindented_line, $matches))
					{
						$elements []= $element;

						$element = array(
							'type' => 'fenced block',
							'text' => '',
							'fence' => $matches[1],
						);

						isset($matches[2]) and $element['language'] = $matches[2];

						continue 2;
					}

					break;

				case '*':
				case '+':
				case '-':
				case '_':

					# hr

					if (preg_match('/^([-*_])([ ]{0,2}\1){2,}[ ]*$/', $deindented_line))
					{
						$elements []= $element;

						$element = array(
							'type' => 'hr',
						);

						continue 2;
					}

					# li

					if (preg_match('/^([ ]*)[*+-][ ](.*)/', $line, $matches))
					{
						$elements []= $element;

						$element = array(
							'type' => 'li',
							'ordered' => false,
							'indentation' => $matches[1],
							'last' => true,
							'lines' => array(
								preg_replace('/^[ ]{0,4}/', '', $matches[2]),
							),
						);

						continue 2;
					}
			}

			# li

			if ($deindented_line[0] <= '9' and $deindented_line[0] >= '0' and preg_match('/^([ ]*)\d+[.][ ](.*)/', $line, $matches))
			{
				$elements []= $element;

				$element = array(
					'type' => 'li',
					'ordered' => true,
					'indentation' => $matches[1],
					'last' => true,
					'lines' => array(
						preg_replace('/^[ ]{0,4}/', '', $matches[2]),
					),
				);

				continue;
			}

			# paragraph

			if ($element['type'] === 'paragraph')
			{
				if (isset($element['interrupted']))
				{
					$elements []= $element;

					$element['text'] = $line;

					unset($element['interrupted']);
				}
				else
				{
					$element['text'] .= "\n".$line;
				}
			}
			else
			{
				$elements []= $element;

				$element = array(
					'type' => 'paragraph',
					'text' => $line,
				);
			}
		}

		$elements []= $element;

		unset($elements[0]);

		#
		# ~
		#

		$markup = '';

		foreach ($elements as $element)
		{
			switch ($element['type'])
			{
				case 'paragraph':

					$text = $this->parse_span_elements($element['text']);

					if ($context === 'li' and $markup === '')
					{
						if (isset($element['interrupted']))
						{
							$markup .= "\n".'<p>'.$text.'</p>'."\n";
						}
						else
						{
							$markup .= $text;
						}
					}
					else
					{
						$markup .= '<p>'.$text.'</p>'."\n";
					}

					break;

				case 'blockquote':

					$text = $this->parse_block_elements($element['lines']);

					$markup .= '<blockquote>'."\n".$text.'</blockquote>'."\n";

					break;

				case 'code block':

					$text = htmlspecialchars($element['text'], ENT_NOQUOTES, 'UTF-8');

					$markup .= '<pre><code>'.$text.'</code></pre>'."\n";

					break;

				case 'fenced block':

					$text = htmlspecialchars($element['text'], ENT_NOQUOTES, 'UTF-8');

					$markup .= '<pre><code';

					isset($element['language']) and $markup .= ' class="language-'.$element['language'].'"';

					$markup .= '>'.$text.'</code></pre>'."\n";

					break;

				case 'heading':

					$text = $this->parse_span_elements($element['text']);

					$markup .= '<h'.$element['level'].'>'.$text.'</h'.$element['level'].'>'."\n";

					break;

				case 'hr':

					$markup .= '<hr />'."\n";

					break;

				case 'li':

					if (isset($element['ordered'])) # first
					{
						$list_type = $element['ordered'] ? 'ol' : 'ul';

						$markup .= '<'.$list_type.'>'."\n";
					}

					if (isset($element['interrupted']) and ! isset($element['last']))
					{
						$element['lines'] []= '';
					}

					$text = $this->parse_block_elements($element['lines'], 'li');

					$markup .= '<li>'.$text.'</li>'."\n";

					isset($element['last']) and $markup .= '</'.$list_type.'>'."\n";

					break;

				case 'block-level markup':

					$markup .= $element['text']."\n";

					break;

				default:

					$markup .= $element['text']."\n";
			}
		}

		return $markup;
	}

	private function parse_span_elements($text, $markers = array('![', '&', '*', '<', '[', '\\', '_', '`', 'http', '~~'))
	{
		if (isset($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 '![':
				case '[':

					if (strpos($text, ']') and preg_match('/\[((?:[^][]|(?R))*)\]/', $text, $matches))
					{
						$element = array(
							'!' => $text[0] === '!',
							'a' => $matches[1],
						);

						$offset = strlen($matches[0]);

						$element['!'] and $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['»'].'" />';
						}
						else
						{
							$element['a'] = $this->parse_span_elements($element['a'], $markers);

							$markup .= isset($element['#'])
								? '<a href="'.$element['»'].'" title="'.$element['#'].'">'.$element['a'].'</a>'
								: '<a href="'.$element['»'].'">'.$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] === $closest_marker and preg_match($this->strong_regex[$closest_marker], $text, $matches))
					{
						$matches[1] = $this->parse_span_elements($matches[1], $markers);

						$markup .= '<strong>'.$matches[1].'</strong>';
					}
					elseif (preg_match($this->em_regex[$closest_marker], $text, $matches))
					{
						$matches[1] = $this->parse_span_elements($matches[1], $markers);

						$markup .= '<em>'.$matches[1].'</em>';
					}
					elseif ($text[1] === $closest_marker and preg_match($this->strong_em_regex[$closest_marker], $text, $matches))
					{
						$matches[2] = $this->parse_span_elements($matches[2], $markers);

						$matches[1] and $matches[1] = $this->parse_span_elements($matches[1], $markers);
						$matches[3] and $matches[3] = $this->parse_span_elements($matches[3], $markers);

						$markup .= '<strong>'.$matches[1].'<em>'.$matches[2].'</em>'.$matches[3].'</strong>';
					}
					elseif (preg_match($this->em_strong_regex[$closest_marker], $text, $matches))
					{
						$matches[2] = $this->parse_span_elements($matches[2], $markers);

						$matches[1] and $matches[1] = $this->parse_span_elements($matches[1], $markers);
						$matches[3] and $matches[3] = $this->parse_span_elements($matches[3], $markers);

						$markup .= '<em>'.$matches[1].'<strong>'.$matches[2].'</strong>'.$matches[3].'</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 (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], $this->special_characters))
					{
						$markup .= $text[1];

						$offset = 2;
					}
					else
					{
						$markup .= '\\';

						$offset = 1;
					}

					break;

				case '`':

					if (preg_match('/^`(.+?)`/', $text, $matches))
					{
						$element_text = $matches[1];
						$element_text = htmlspecialchars($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/i', $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;
		}

		$markup = str_replace($this->break_marker, '<br />'."\n", $markup);

		return $markup;
	}

	#
	# Read-only
	#

	private $inline_tags = array(
		'a', 'abbr', 'acronym', 'b', 'bdo', 'big', 'br', 'button',
		'cite', 'code', 'dfn', 'em', 'i', 'img', 'input', 'kbd',
		'label', 'map', 'object', 'q', 'samp', 'script', 'select', 'small',
		'span', 'strong', 'sub', 'sup', 'textarea', 'tt', 'var',
	);

	private $special_characters = array('\\', '`', '*', '_', '{', '}', '[', ']', '(', ')', '>', '#', '+', '-', '.', '!');

	# ~

	private $strong_regex = array(
		'*' => '/^[*]{2}([^*]+?)[*]{2}(?![*])/s',
		'_' => '/^__([^_]+?)__(?!_)/s',
	);

	private $em_regex = array(
		'*' => '/^[*]([^*]+?)[*](?![*])/s',
		'_' => '/^_([^_]+?)[_](?![_])\b/s',
	);

	private $strong_em_regex = array(
		'*' => '/^[*]{2}(.*?)[*](.+?)[*](.*?)[*]{2}/s',
		'_' => '/^__(.*?)_(.+?)_(.*?)__/s',
	);

	private $em_strong_regex = array(
		'*' => '/^[*](.*?)[*]{2}(.+?)[*]{2}(.*?)[*]/s',
		'_' => '/^_(.*?)__(.+?)__(.*?)_/s',
	);
}