<?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();
	
	# 
	# Fields 
	# 
	
	private $reference_map = array();
	private $escape_sequence_map = array();
	
	# 
	# Public Methods 
	# 
	
	function parse($text)
	{	
		# Removes UTF-8 BOM and marker characters.
		$text = preg_replace('{^\xEF\xBB\xBF|\x1A}', '', $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);
		
		# Encodes escape sequences.
		
		if (strpos($text, '\\') !== FALSE)
		{
			$escape_sequences = array('\\\\', '\`', '\*', '\_', '\{', '\}', '\[', '\]', '\(', '\)', '\>', '\#', '\+', '\-', '\.', '\!');
			
			foreach ($escape_sequences as $index => $escape_sequence)
			{
				if (strpos($text, $escape_sequence) !== FALSE)
				{
					$code = "\x1A".'\\'.$index;
					
					$text = str_replace($escape_sequence, $code, $text);
					
					$this->escape_sequence_map[$code] = $escape_sequence;
				}
			}
		}
		
		# Extracts link references.
		
		if (preg_match_all('/^[ ]{0,3}\[(.+)\][ ]?:[ ]*\n?[ ]*(.+)$/m', $text, $matches, PREG_SET_ORDER))
		{
			foreach ($matches as $matches)
			{
				$this->reference_map[strtolower($matches[1])] = $matches[2];
				
				$text = str_replace($matches[0], '', $text);
			}
		}
		
		# ~ 
		
		$text = preg_replace('/\n\s*\n/', "\n\n", $text);
		$text = trim($text, "\n");
		
		$lines = explode("\n", $text);
		
		$text = $this->parse_block_elements($lines);
		
		# Decodes escape sequences (leaves out backslashes).
		
		foreach ($this->escape_sequence_map as $code => $escape_sequence)
		{
			$text = str_replace($code, $escape_sequence[1], $text);
		}
		
		$text = rtrim($text, "\n");
		
		return $text;
	}
	
	# 
	# Private Methods 
	# 
	
	private function parse_block_elements(array $lines, $context = '')
	{
		$elements = array();
		
		$element = array(
			'type' => '',
		);
		
		foreach ($lines as $line)
		{
			# Empty 
			
			if ($line === '')
			{
				$element['interrupted'] = true;
				
				$element['type'] === 'code' and $element['text'] .= "\n";
				
				continue;
			}
			
			# Lazy Blockquote 
			
			if ($element['type'] === 'blockquote' and ! isset($element['interrupted']))
			{
				$line = preg_replace('/^[ ]*>[ ]?/', '', $line);
				
				$element['lines'] []= $line;
				
				continue;
			}
			
			# Lazy List Item 
			
			if ($element['type'] === '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;
				}
				
				if (isset($element['interrupted']))
				{
					if ($line[0] === ' ')
					{
						$element['lines'] []= '';
						
						$line = preg_replace('/^[ ]{0,4}/', '', $line);;
						
						$element['lines'] []= $line;
						
						continue;
					}
				}
				else
				{
					$line = preg_replace('/^[ ]{0,4}/', '', $line);;
						
					$element['lines'] []= $line;
					
					continue;
				}
			}
			
			# Quick Paragraph 
			
			if ($line[0] >= 'A' and $line['0'] !== '_')
			{
				goto paragraph; # trust me 
			}
			
			# Setext Header (---) 
			
			if ($element['type'] === 'p' and preg_match('/^[-]+[ ]*$/', $line))
			{
				$element['type'] = 'h.';
				$element['level'] = 2;
				
				continue;
			}
			
			# Horizontal Rule  
			
			if (preg_match('/^[ ]{0,3}([-*_])([ ]{0,2}\1){2,}[ ]*$/', $line))
			{
				$elements []= $element;
				
				$element = array(
					'type' => 'hr',
				);
				
				continue;
			}
			
			# List Item 
			
			if (preg_match('/^([ ]{0,3})(\d+[.]|[*+-])[ ](.*)/', $line, $matches))
			{
				$elements []= $element;
				
				$element = array(
					'type' => 'li',
					'ordered' => isset($matches[2][1]),
					'indentation' => $matches[1],
					'last' => true,
					'lines' => array(
						preg_replace('/^[ ]{0,4}/', '', $matches[3]),
					),
				);
				
				continue;
			}
			
			# Code 
			
			if (preg_match('/^[ ]{4}(.*)/', $line, $matches))
			{
				if ($element['type'] === 'code')
				{
					$element['text'] .= "\n".$matches[1];
				}
				else
				{
					$elements []= $element;
					
					$element = array(
						'type' => 'code', 
						'text' => $matches[1],
					);
				}
				
				continue;
			}
			
			# Atx Header (#)
			
			if ($line[0] === '#' and preg_match('/^(#{1,6})[ ]*(.+?)[ ]*#*$/', $line, $matches))
			{
				$elements []= $element;
				
				$level = strlen($matches[1]);
				
				$element = array(
					'type' => 'h.', 
					'text' => $matches[2], 
					'level' => $level,
				);
				
				continue;
			}
			
			# Blockquote 
			
			if (preg_match('/^[ ]*>[ ]?(.*)/', $line, $matches))
			{
				if ($element['type'] === 'blockquote')
				{
					if (isset($element['interrupted']))
					{
						$element['lines'] []= '';
						
						unset($element['interrupted']);
					}
					
					$element['lines'] []= $matches[1];
				}
				else
				{
					$elements []= $element;
					
					$element = array(
						'type' => 'blockquote',
						'lines' => array(
							$matches[1],
						),
					);
				}
				
				continue;
			}
			
			# Setext Header (===) 
			
			if ($element['type'] === 'p' and preg_match('/^[=]+[ ]*$/', $line))
			{
				$element['type'] = 'h.';
				$element['level'] = 1;
				
				continue;
			}
			
			# ~ 
			
			paragraph:
			
			if ($element['type'] === 'p')
			{
				if (isset($element['interrupted']))
				{
					$elements []= $element;
					
					$element['text'] = $line;
					
					unset($element['interrupted']);
				}
				else
				{
					$element['text'] .= "\n".$line;
				}
			}
			else
			{
				$elements []= $element;
				
				$element = array(
					'type' => 'p', 
					'text' => $line,
				);
			}
		}
		
		$elements []= $element;
		
		array_shift($elements);
		
		# 
		# ~ 
		# 
		
		$markup = '';
		
		foreach ($elements as $index => $element)
		{
			switch ($element['type'])
			{
				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 'p':
					
					$text = $this->parse_inline_elements($element['text']);
					
					$text = preg_replace('/[ ]{2}\n/', '<br />'."\n", $text);
					
					if ($context === 'li' and $index === 0)
					{
						if (isset($element['interrupted']))
						{
							$markup .= "\n".'<p>'.$text.'</p>'."\n";
						}
						else 
						{
							$markup .= $text;
						}
					}
					else 
					{
						$markup .= '<p>'.$text.'</p>'."\n";
					}
					
					break;
				
				case 'code':
					
					$text = rtrim($element['text'], "\n");
					
					$text = htmlentities($text, ENT_NOQUOTES);
					
					strpos($text, "\x1A\\") !== FALSE and $text = strtr($text, $this->escape_sequence_map);
					
					$markup .= '<pre><code>'.$text.'</code></pre>'."\n";
					
					break;
				
				case 'blockquote':
					
					$text = $this->parse_block_elements($element['lines']);
					
					$markup .= '<blockquote>'."\n".$text.'</blockquote>'."\n";
					
					break;
				
				case 'h.':
					
					$text = $this->parse_inline_elements($element['text']);
					
					$markup .= '<h'.$element['level'].'>'.$text.'</h'.$element['level'].'>'."\n";
					
					break;
				
				case 'hr':
					
					$markup .= '<hr />'."\n";
					
					break;
			}
		}
		
		return $markup;
	}
	
	private function parse_inline_elements($text)
	{
		$map = array();
		
		$index = 0;
		
		# Code Span 
		
		if (strpos($text, '`') !== FALSE and preg_match_all('/`(.+?)`/', $text, $matches, PREG_SET_ORDER)) 
		{
			foreach ($matches as $matches)
			{
				$element_text = $matches[1];
				$element_text = htmlentities($element_text, ENT_NOQUOTES);
				
				# Decodes escape sequences.
				
				$this->escape_sequence_map 
					and strpos($element_text, "\x1A") !== FALSE 
					and $element_text = strtr($element_text, $this->escape_sequence_map);
				
				# Composes element.
				
				$element = '<code>'.$element_text.'</code>';
				
				# Encodes element.
				
				$code = "\x1A".'$'.$index;
				
				$text = str_replace($matches[0], $code, $text);
				
				$map[$code] = $element;
				
				$index ++;
			}
		}
		
		# Inline Link / Image 
		
		if (strpos($text, '](') !== FALSE and preg_match_all('/(!?)(\[((?:[^][]+|(?2))*)\])\((.*?)\)/', $text, $matches, PREG_SET_ORDER)) # inline 
		{
			foreach ($matches as $matches)
			{
				if ($matches[1]) # image 
				{
					$element = '<img alt="'.$matches[3].'" src="'.$matches[4].'">';
				}
				else 
				{
					$element_text = $this->parse_inline_elements($matches[3]);
					
					$element = '<a href="'.$matches[4].'">'.$element_text.'</a>';
				}
				
				$element_text = $this->parse_inline_elements($matches[1]);
				
				# ~ 

				$code = "\x1A".'$'.$index;

				$text = str_replace($matches[0], $code, $text);

				$map[$code] = $element;
				
				$index ++;
			}
		}
		
		# Reference(d) Link / Image 
		
		if ($this->reference_map and strpos($text, '[') !== FALSE and preg_match_all('/(!?)\[(.+?)\](?:\n?[ ]?\[(.*?)\])?/ms', $text, $matches, PREG_SET_ORDER))
		{
			foreach ($matches as $matches)
			{
				$link_difinition = isset($matches[3]) && $matches[3]
					? $matches[3]
					: $matches[2]; # implicit 
				
				$link_difinition = strtolower($link_difinition);
				
				if (isset($this->reference_map[$link_difinition]))
				{
					$url = $this->reference_map[$link_difinition];
					
					if ($matches[1]) # image 
					{
						$element = '<img alt="'.$matches[2].'" src="'.$url.'">';
					}
					else # anchor 
					{
						$element_text = $this->parse_inline_elements($matches[2]);

						$element = '<a href="'.$url.'">'.$element_text.'</a>';
					}

					# ~ 

					$code = "\x1A".'$'.$index;

					$text = str_replace($matches[0], $code, $text);

					$map[$code] = $element;

					$index ++;
				}
			}
		}
		
		if (strpos($text, '<') !== FALSE and preg_match_all('/<((https?|ftp|dict):[^\^\s]+?)>/i', $text, $matches, PREG_SET_ORDER))
		{
			foreach ($matches as $matches)
			{
				$element = '<a href=":href">:text</a>';
				$element = str_replace(':text', $matches[1], $element);
				$element = str_replace(':href', $matches[1], $element);
				
				# ~ 
				
				$code = "\x1A".'$'.$index;
				
				$text = str_replace($matches[0], $code, $text);
				
				$map[$code] = $element;
				
				$index ++;
			}
		}
		
		if (strpos($text, '_') !== FALSE)
		{
			$text = preg_replace('/__(?=\S)(.+?)(?<=\S)__/', '<strong>$1</strong>', $text);
			$text = preg_replace('/_(?=\S)(.+?)(?<=\S)_/', '<em>$1</em>', $text);
		}
		
		if (strpos($text, '*') !== FALSE)
		{
			$text = preg_replace('/\*\*(?=\S)(.+?)(?<=\S)\*\*/', '<strong>$1</strong>', $text);
			$text = preg_replace('/\*(?=\S)(.+?)(?<=\S)\*/', '<em>$1</em>', $text);
		}
		
		$text = strtr($text, $map);
		
		return $text;
	}
}