<?php

// if want to implement error collecting here, we'll need to use some sort
// of global data (probably trigger_error) because it's impossible to pass
// $config or $context to the callback functions.

/**
 * Handles referencing and derefencing character entities
 */
class HTMLPurifier_EntityParser {
	
	/**
	 * Reference to entity lookup table.
	 * @type HTMLPurifier_EntityLookup
	 */
	protected $_entity_lookup;
	
	/**
	 * Callback regex string for parsing entities.
	 * @type string
	 */
	protected $_substituteEntitiesRegex = '/&(?:[#]x([a-fA-F0-9]+)|[#]0*(\d+)|([A-Za-z_:][A-Za-z0-9.\-_:]*));?/';
	// 1. hex 2. dec 3. string (XML style)
	
	/**
	 * Decimal to parsed string conversion table for special entities.
	 * @type array
	 */
	protected $_special_dec2str = array (
			34 => '"',
			38 => '&',
			39 => "'",
			60 => '<',
			62 => '>' 
	);
	
	/**
	 * Stripped entity names to decimal conversion table for special entities.
	 * @type array
	 */
	protected $_special_ent2dec = array (
			'quot' => 34,
			'amp' => 38,
			'lt' => 60,
			'gt' => 62 
	);
	
	/**
	 * Substitutes non-special entities with their parsed equivalents.
	 * Since
	 * running this whenever you have parsed character is t3h 5uck, we run
	 * it before everything else.
	 *
	 * @param string $string
	 *        	String to have non-special entities parsed.
	 * @return string Parsed string.
	 */
	public function substituteNonSpecialEntities($string) {
		// it will try to detect missing semicolons, but don't rely on it
		return preg_replace_callback ( $this->_substituteEntitiesRegex, array (
				$this,
				'nonSpecialEntityCallback' 
		), $string );
	}
	
	/**
	 * Callback function for substituteNonSpecialEntities() that does the work.
	 *
	 * @param array $matches
	 *        	PCRE matches array, with 0 the entire match, and
	 *        	either index 1, 2 or 3 set with a hex value, dec value,
	 *        	or string (respectively).
	 * @return string Replacement string.
	 */
	protected function nonSpecialEntityCallback($matches) {
		// replaces all but big five
		$entity = $matches [0];
		$is_num = (@$matches [0] [1] === '#');
		if ($is_num) {
			$is_hex = (@$entity [2] === 'x');
			$code = $is_hex ? hexdec ( $matches [1] ) : ( int ) $matches [2];
			// abort for special characters
			if (isset ( $this->_special_dec2str [$code] )) {
				return $entity;
			}
			return HTMLPurifier_Encoder::unichr ( $code );
		} else {
			if (isset ( $this->_special_ent2dec [$matches [3]] )) {
				return $entity;
			}
			if (! $this->_entity_lookup) {
				$this->_entity_lookup = HTMLPurifier_EntityLookup::instance ();
			}
			if (isset ( $this->_entity_lookup->table [$matches [3]] )) {
				return $this->_entity_lookup->table [$matches [3]];
			} else {
				return $entity;
			}
		}
	}
	
	/**
	 * Substitutes only special entities with their parsed equivalents.
	 *
	 * @notice We try to avoid calling this function because otherwise, it
	 * would have to be called a lot (for every parsed section).
	 *
	 * @param string $string
	 *        	String to have non-special entities parsed.
	 * @return string Parsed string.
	 */
	public function substituteSpecialEntities($string) {
		return preg_replace_callback ( $this->_substituteEntitiesRegex, array (
				$this,
				'specialEntityCallback' 
		), $string );
	}
	
	/**
	 * Callback function for substituteSpecialEntities() that does the work.
	 *
	 * This callback has same syntax as nonSpecialEntityCallback().
	 *
	 * @param array $matches
	 *        	PCRE-style matches array, with 0 the entire match, and
	 *        	either index 1, 2 or 3 set with a hex value, dec value,
	 *        	or string (respectively).
	 * @return string Replacement string.
	 */
	protected function specialEntityCallback($matches) {
		$entity = $matches [0];
		$is_num = (@$matches [0] [1] === '#');
		if ($is_num) {
			$is_hex = (@$entity [2] === 'x');
			$int = $is_hex ? hexdec ( $matches [1] ) : ( int ) $matches [2];
			return isset ( $this->_special_dec2str [$int] ) ? $this->_special_dec2str [$int] : $entity;
		} else {
			return isset ( $this->_special_ent2dec [$matches [3]] ) ? $this->_special_ent2dec [$matches [3]] : $entity;
		}
	}
}

// vim: et sw=4 sts=4