<?php
/**
 * Generic string parsing infrastructure
 *
 * These classes provide the means to parse any kind of string into a tree-like
 * memory structure. It would e.g. be possible to create an HTML parser based
 * upon this class.
 * 
 * Version: 0.3.0-alpha1
 *
 * @author Christian Seiler <spam@christian-seiler.de>
 * @copyright Christian Seiler 2005
 * @package stringparser
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of either:
 *
 *  a) the GNU General Public License as published by the Free
 *  Software Foundation; either version 1, or (at your option) any
 *  later version, or
 *
 *  b) the Artistic License as published by Larry Wall, either version 2.0,
 *     or (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See either
 *  the GNU General Public License or the Artistic License for more details.
 *
 *  You should have received a copy of the Artistic License with this Kit,
 *  in the file named "Artistic.clarified".  If not, I'll be glad to provide
 *  one.
 *
 *  You should also have received a copy of the GNU General Public License
 *  along with this program in the file named "COPYING"; if not, write to
 *  the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *  MA 02111-1307, USA.
 */

/**
 * String parser mode: Search for the next character
 * @see StringParser::_parserMode
 */
define ('STRINGPARSER_MODE_SEARCH', 1);
/**
 * String parser mode: Look at each character of the string
 * @see StringParser::_parserMode
 */
define ('STRINGPARSER_MODE_LOOP', 2);
/**
 * Filter type: Prefilter
 * @see StringParser::addFilter, StringParser::_prefilters
 */
define ('STRINGPARSER_FILTER_PRE', 1);
/**
 * Filter type: Postfilter
 * @see StringParser::addFilter, StringParser::_postfilters
 */
define ('STRINGPARSER_FILTER_POST', 2);

/**
 * Generic string parser class
 *
 * This is an abstract class for any type of string parser.
 *
 * @package stringparser
 */
class StringParser {
	/**
	 * String parser mode
	 *
	 * There are two possible modes: searchmode and loop mode. In loop mode
	 * every single character is looked at in a loop and it is then decided
	 * what action to take. This is the most straight-forward approach to
	 * string parsing but due to the nature of PHP as a scripting language,
	 * it can also cost performance. In search mode the class posseses a
	 * list of relevant characters for parsing and uses the
	 * {@link PHP_MANUAL#strpos strpos} function to search for the next
	 * relevant character. The search mode will be faster than the loop mode
	 * in most circumstances but it is also more difficult to implement.
	 * The subclass that does the string parsing itself will define which
	 * mode it will implement.
	 *
	 * @access private
	 * @var int
	 * @see STRINGPARSER_MODE_SEARCH, STRINGPARSER_MODE_LOOP
	 */
	var $_parserMode = STRINGPARSER_MODE_SEARCH;
	
	/**
	 * Raw text
	 * @access private
	 * @var string
	 */
	var $_text = '';
	
	/**
	 * Parse stack
	 * @access private
	 * @var array
	 */
	var $_stack = array ();
	
	/**
	 * Current position in raw text
	 * @access private
	 * @var integer
	 */
	var $_cpos = -1;
	
	/**
	 * Root node
	 * @access private
	 * @var mixed
	 */
	var $_root = null;
	
	/**
	 * Length of the text
	 * @access private
	 * @var integer
	 */
	var $_length = -1;
	
	/**
	 * Flag if this object is already parsing a text
	 *
	 * This flag is to prevent recursive calls to the parse() function that
	 * would cause very nasty things.
	 *
	 * @access private
	 * @var boolean
	 */
	var $_parsing = false;
	
	/**
	 * Strict mode
	 *
	 * Whether to stop parsing if a parse error occurs.
	 *
	 * @access public
	 * @var boolean
	 */
	var $strict = false;
	
	/**
	 * Characters or strings to look for
	 * @access private
	 * @var array
	 */
	var $_charactersSearch = array ();
	
	/**
	 * Characters currently allowed
	 *
	 * Note that this will only be evaluated in loop mode; in search mode
	 * this would ruin every performance increase. Note that only single
	 * characters are permitted here, no strings. Please also note that in
	 * loop mode, {@link StringParser::_charactersSearch _charactersSearch}
	 * is evaluated before this variable.
	 *
	 * If in strict mode, parsing is stopped if a character that is not
	 * allowed is encountered. If not in strict mode, the character is
	 * simply ignored.
	 *
	 * @access private
	 * @var array
	 */
	var $_charactersAllowed = array ();
	
	/**
	 * Current parser status
	 * @access private
	 * @var int
	 */
	var $_status = 0;
	
	/**
	 * Prefilters
	 * @access private
	 * @var array
	 */
	var $_prefilters = array ();
	
	/**
	 * Postfilters
	 * @access private
	 * @var array
	 */
	var $_postfilters = array ();
	
	/**
	 * Recently reparsed?
	 * @access private
	 * @var bool
	 */
	var $_recentlyReparsed = false;
	 
	/**
	 * Constructor
	 *
	 * @access public
	 */
	function StringParser () {
	}
	
	/**
	 * Add a filter
	 *
	 * @access public
	 * @param int $type The type of the filter
	 * @param mixed $callback The callback to call
	 * @return bool
	 * @see STRINGPARSER_FILTER_PRE, STRINGPARSER_FILTER_POST
	 */
	function addFilter ($type, $callback) {
		// make sure the function is callable
		if (!is_callable ($callback)) {
			return false;
		}
		
		switch ($type) {
			case STRINGPARSER_FILTER_PRE:
				$this->_prefilters[] = $callback;
				break;
			case STRINGPARSER_FILTER_POST:
				$this->_postfilters[] = $callback;
				break;
			default:
				return false;
		}
		
		return true;
	}
	
	/**
	 * Remove all filters
	 *
	 * @access public
	 * @param int $type The type of the filter or 0 for all
	 * @return bool
	 * @see STRINGPARSER_FILTER_PRE, STRINGPARSER_FILTER_POST
	 */
	function clearFilters ($type = 0) {
		switch ($type) {
			case 0:
				$this->_prefilters = array ();
				$this->_postfilters = array ();
				break;
			case STRINGPARSER_FILTER_PRE:
				$this->_prefilters = array ();
				break;
			case STRINGPARSER_FILTER_POST:
				$this->_postfilters = array ();
				break;
			default:
				return false;
		}
		return true;
	}
	
	/**
	 * This function parses the text
	 *
	 * @access public
	 * @param string $text The text to parse
	 * @return mixed Either the root object of the tree if no output method
	 *               is defined, the tree reoutput to e.g. a string or false
	 *               if an internal error occured, such as a parse error if
	 *               in strict mode or the object is already parsing a text.
	 */
	function parse ($text) {
		if ($this->_parsing) {
			return false;
		}
		$this->_parsing = true;
		$this->_text = $this->_applyPrefilters ($text);
		$this->_output = null;
		$this->_length = strlen ($this->_text);
		$this->_cpos = 0;
		unset ($this->_stack);
		$this->_stack = array ();
		if (is_object ($this->_root)) {
			StringParser_Node::destroyNode ($this->_root);
		}
		unset ($this->_root);
		$this->_root =& new StringParser_Node_Root ();
		$this->_stack[0] =& $this->_root;
		
		$this->_parserInit ();
		
		$finished = false;
		
		while (!$finished) {
			switch ($this->_parserMode) {
				case STRINGPARSER_MODE_SEARCH:
					$res = $this->_searchLoop ();
					if (!$res) {
						$this->_parsing = false;
						return false;
					}
					break;
				case STRINGPARSER_MODE_LOOP:
					$res = $this->_loop ();
					if (!$res) {
						$this->_parsing = false;
						return false;
					}
					break;
				default:
					$this->_parsing = false;
					return false;
			}
			
			$res = $this->_closeRemainingBlocks ();
			if (!$res) {
				if ($this->strict) {
					$this->_parsing = false;
					return false;
				} else {
					$res = $this->_reparseAfterCurrentBlock ();
					if (!$res) {
						$this->_parsing = false;
						return false;
					}
					continue;
				}
			}
			$finished = true;
		}
		
		$res = $this->_modifyTree ();
		
		if (!$res) {
			$this->_parsing = false;
			return false;
		}
		
		$res = $this->_outputTree ();
		
		if (!$res) {
			$this->_parsing = false;
			return false;
		}
		
		if (is_null ($this->_output)) {
			$root =& $this->_root;
			unset ($this->_root);
			$this->_root = null;
			while (count ($this->_stack)) {
				unset ($this->_stack[count($this->_stack)-1]);
			}
			$this->_stack = array ();
			$this->_parsing = false;
			return $root;
		}
		
		$res = StringParser_Node::destroyNode ($this->_root);
		if (!$res) {
			$this->_parsing = false;
			return false;
		}
		unset ($this->_root);
		$this->_root = null;
		while (count ($this->_stack)) {
			unset ($this->_stack[count($this->_stack)-1]);
		}
		$this->_stack = array ();
		
		$this->_parsing = false;
		return $this->_output;
	}
	
	/**
	 * Apply prefilters
	 *
	 * It is possible to specify prefilters for the parser to do some
	 * manipulating of the string beforehand.
	 */
	function _applyPrefilters ($text) {
		foreach ($this->_prefilters as $filter) {
			if (is_callable ($filter)) {
				$ntext = call_user_func ($filter, $text);
				if (is_string ($ntext)) {
					$text = $ntext;
				}
			}
		}
		return $text;
	}
	
	/**
	 * Apply postfilters
	 *
	 * It is possible to specify postfilters for the parser to do some
	 * manipulating of the string afterwards.
	 */
	function _applyPostfilters ($text) {
		foreach ($this->_postfilters as $filter) {
			if (is_callable ($filter)) {
				$ntext = call_user_func ($filter, $text);
				if (is_string ($ntext)) {
					$text = $ntext;
				}
			}
		}
		return $text;
	}
	
	/**
	 * Abstract method: Manipulate the tree
	 * @access private
	 * @return bool
	 */
	function _modifyTree () {
		return true;
	}
	
	/**
	 * Abstract method: Output tree
	 * @access private
	 * @return bool
	 */
	function _outputTree () {
		// this could e.g. call _applyPostfilters
		return true;
	}
	
	/**
	 * Restart parsing after current block
	 *
	 * To achieve this the current top stack object is removed from the
	 * tree. Then the current item
	 *
	 * @access protected
	 * @return bool
	 */
	function _reparseAfterCurrentBlock () {
		// this should definitely not happen!
		if (($stack_count = count ($this->_stack)) < 2) {
			return false;
		}
		$topelem =& $this->_stack[$stack_count-1];
		
		$node_parent =& $topelem->_parent;
		// remove the child from the tree
		$res = $node_parent->removeChild ($topelem, false);
		if (!$res) {
			return false;
		}
		$res = $this->_popNode ();
		if (!$res) {
			return false;
		}
		
		// now try to get the position of the object
		if ($topelem->occurredAt < 0) {
			return false;
		}
		// HACK: could it be necessary to set a different status
		// if yes, how should this be achieved? Another member of
		// StringParser_Node?
		$this->_setStatus (0);
		$res = $this->_appendText ($this->_text{$topelem->occurredAt});
		if (!$res) {
			return false;
		}
		
		$this->_cpos = $topelem->occurredAt + 1;
		$this->_recentlyReparsed = true;
		
		return true;
	}
	
	/**
	 * Abstract method: Close remaining blocks
	 * @access private
	 */
	function _closeRemainingBlocks () {
		// everything closed
		if (count ($this->_stack) == 1) {
			return true;
		}
		// not everything closed
		if ($this->strict) {
			return false;
		}
		while (count ($this->_stack) > 1) {
			$res = $this->_popNode ();
			if (!$res) {
				return false;
			}
		}
		return true;
	}
	
	/**
	 * Abstract method: Initialize the parser
	 * @access private
	 */
	function _parserInit () {
		$this->_setStatus (0);
	}
	
	/**
	 * Abstract method: Set a specific status
	 * @access private
	 */
	function _setStatus ($status) {
		if ($status != 0) {
			return false;
		}
		$this->_charactersSearch = array ();
		$this->_charactersAllowed = array ();
		$this->_status = $status;
		return true;
	}
	
	/**
	 * Abstract method: Handle status
	 * @access private
	 * @param int $status The current status
	 * @param string $needle The needle that was found
	 * @return bool
	 */
	function _handleStatus ($status, $needle) {
		$this->_appendText ($needle);
		$this->_cpos += strlen ($needle);
		return true;
	}
	
	/**
	 * Search mode loop
	 * @access private
	 * @return bool
	 */
	function _searchLoop () {
		$i = 0;
		while (1) {
			// make sure this is false!
			$this->_recentlyReparsed = false;
			
			list ($needle, $offset) = $this->_strpos ($this->_charactersSearch, $this->_cpos);
			// parser ends here
			if ($needle === false) {
				// original status 0 => no problem
				if (!$this->_status) {
					break;
				}
				// not in original status? strict mode?
				if ($this->strict) {
					return false;
				}
				// break up parsing operation of current node
				$res = $this->_reparseAfterCurrentBlock ();
				if (!$res) {
					return false;
				}
				continue;
			}
			// get subtext
			$subtext = substr ($this->_text, $this->_cpos, $offset - $this->_cpos);
			$res = $this->_appendText ($subtext);
			if (!$res) {
				return false;
			}
			$this->_cpos = $offset;
			$res = $this->_handleStatus ($this->_status, $needle);
			if (!$res && $strict) {
				return false;
			}
			if (!$res) {
				$res = $this->_appendText ($this->_text{$this->_cpos});
				if (!$res) {
					return false;
				}
				$this->_cpos++;
				continue;
			}
			if ($this->_recentlyReparsed) {
				$this->_recentlyReparsed = false;
				continue;
			}
			$this->_cpos += strlen ($needle);
		}
		
		// get subtext
		if ($this->_cpos < strlen ($this->_text)) {
			$subtext = substr ($this->_text, $this->_cpos);
			$res = $this->_appendText ($subtext);
			if (!$res) {
				return false;
			}
		}
		
		return true;
	}
	
	/**
	 * Loop mode loop
	 *
	 * @access private
	 * @return bool
	 */
	function _loop () {
		// HACK: This method ist not yet implemented correctly, the code below
		// DOES NOT WORK! Do not use!
		
		return false;
		/*
		while ($this->_cpos < $this->_length) {
			$needle = $this->_strDetect ($this->_charactersSearch, $this->_cpos);
			
			if ($needle === false) {
				// not found => see if character is allowed
				if (!in_array ($this->_text{$this->_cpos}, $this->_charactersAllowed)) {
					if ($strict) {
						return false;
					}
					// ignore
					continue;
				}
				// lot's of FIXMES
				$res = $this->_appendText ($this->_text{$this->_cpos});
				if (!$res) {
					return false;
				}
			}
			
			// get subtext
			$subtext = substr ($this->_text, $offset, $offset - $this->_cpos);
			$res = $this->_appendText ($subtext);
			if (!$res) {
				return false;
			}
			$this->_cpos = $subtext;
			$res = $this->_handleStatus ($this->_status, $needle);
			if (!$res && $strict) {
				return false;
			}
		}
		// original status 0 => no problem
		if (!$this->_status) {
			return true;
		}
		// not in original status? strict mode?
		if ($this->strict) {
			return false;
		}
		// break up parsing operation of current node
		$res = $this->_reparseAfterCurrentBlock ();
		if (!$res) {
			return false;
		}
		// this will not cause an infinite loop because
		// _reparseAfterCurrentBlock will increase _cpos by one!
		return $this->_loop ();
		*/
	}
	
	/**
	 * Abstract method Append text depending on current status
	 * @access private
	 * @param string $text The text to append
	 * @return bool On success, the function returns true, else false
	 */
	function _appendText ($text) {
		if (!strlen ($text)) {
			return true;
		}
		// default: call _appendToLastTextChild
		return $this->_appendToLastTextChild ($text);
	}
	
	/**
	 * Append text to last text child of current top parser stack node
	 * @access private
	 * @param string $text The text to append
	 * @return bool On success, the function returns true, else false
	 */
	function _appendToLastTextChild ($text) {
		$scount = count ($this->_stack);
		if ($scount == 0) {
			return false;
		}
		return $this->_stack[$scount-1]->appendToLastTextChild ($text);
	}
	
	/**
	 * Searches {@link StringParser::_text _text} for every needle that is
	 * specified by using the {@link PHP_MANUAL#strpos strpos} function. It
	 * returns an associative array with the key <code>'needle'</code>
	 * pointing at the string that was found first and the key
	 * <code>'offset'</code> pointing at the offset at which the string was
	 * found first. If no needle was found, the <code>'needle'</code>
	 * element is <code>false</code> and the <code>'offset'</code> element
	 * is <code>-1</code>.
	 *
	 * @access private
	 * @param array $needles
	 * @param int $offset
	 * @return array
	 * @see StringParser::_text
	 */
	function _strpos ($needles, $offset) {
		$cur_needle = false;
		$cur_offset = -1;
		
		if ($offset < strlen ($this->_text)) {
			foreach ($needles as $needle) {
				$n_offset = strpos ($this->_text, $needle, $offset);
				if ($n_offset !== false && ($n_offset < $cur_offset || $cur_offset < 0)) {
					$cur_needle = $needle;
					$cur_offset = $n_offset;
				}
			}
		}
		
		return array ($cur_needle, $cur_offset, 'needle' => $cur_needle, 'offset' => $cur_offset);
	}
	
	/**
	 * Detects a string at the current position
	 *
	 * @access private
	 * @param array $needles The strings that are to be detected
	 * @param int $offset The current offset
	 * @return mixed The string that was detected or the needle
	 */
	function _strDetect ($needles, $offset) {
		foreach ($needles as $needle) {
			$l = strlen ($needle);
			if (substr ($this->_text, $offset, $l) == $needle) {
				return $needle;
			}
		}
		return false;
	}
	
	
	/**
	 * Adds a node to the current parse stack
	 *
	 * @access private
	 * @param object $node The node that is to be added
	 * @return bool True on success, else false.
	 * @see StringParser_Node, StringParser::_stack
	 */
	function _pushNode (&$node) {
		$stack_count = count ($this->_stack);
		$max_node =& $this->_stack[$stack_count-1];
		if (!$max_node->appendChild ($node)) {
			return false;
		}
		$this->_stack[$stack_count] =& $node;
		return true;
	}
	
	/**
	 * Removes a node from the current parse stack
	 *
	 * @access private
	 * @return bool True on success, else false.
	 * @see StringParser_Node, StringParser::_stack
	 */
	function _popNode () {
		$stack_count = count ($this->_stack);
		unset ($this->_stack[$stack_count-1]);
		return true;
	}
	
	/**
	 * Execute a method on the top element
	 *
	 * @access private
	 * @return mixed
	 */
	function _topNode () {
		$args = func_get_args ();
		if (!count ($args)) {
			return; // oops?
		}
		$method = array_shift ($args);
		$stack_count = count ($this->_stack);
		$method = array (&$this->_stack[$stack_count-1], $method);
		if (!is_callable ($method)) {
			return; // oops?
		}
		return call_user_func_array ($method, $args);
	}
	
	/**
	 * Get a variable of the top element
	 *
	 * @access private
	 * @return mixed
	 */
	function _topNodeVar ($var) {
		$stack_count = count ($this->_stack);
		return $this->_stack[$stack_count-1]->$var;
	}
}

/**
 * Node type: Unknown node
 * @see StringParser_Node::_type
 */
define ('STRINGPARSER_NODE_UNKNOWN', 0);

/**
 * Node type: Root node
 * @see StringParser_Node::_type
 */
define ('STRINGPARSER_NODE_ROOT', 1);

/**
 * Node type: Text node
 * @see StringParser_Node::_type
 */
define ('STRINGPARSER_NODE_TEXT', 2);

/**
 * Global value that is a counter of string parser node ids. Compare it to a
 * sequence in databases.
 * @var int
 */
$GLOBALS['__STRINGPARSER_NODE_ID'] = 0;

/**
 * Generic string parser node class
 *
 * This is an abstract class for any type of node that is used within the
 * string parser. General warning: This class contains code regarding references
 * that is very tricky. Please do not touch this code unless you exactly know
 * what you are doing. Incorrect handling of references may cause PHP to crash
 * with a segmentation fault! You have been warned.
 *
 * @package stringparser
 */
class StringParser_Node {
	/**
	 * The type of this node.
	 * 
	 * There are three standard node types: root node, text node and unknown
	 * node. All node types are integer constants. Any node type of a
	 * subclass must be at least 32 to allow future developements.
	 *
	 * @access private
	 * @var int
	 * @see STRINGPARSER_NODE_ROOT, STRINGPARSER_NODE_TEXT
	 * @see STRINGPARSER_NODE_UNKNOWN
	 */
	var $_type = STRINGPARSER_NODE_UNKNOWN;
	
	/**
	 * The node ID
	 *
	 * This ID uniquely identifies this node. This is needed when searching
	 * for a specific node in the children array. Please note that this is
	 * only an internal variable and should never be used - not even in
	 * subclasses and especially not in external data structures. This ID
	 * has nothing to do with any type of ID in HTML oder XML.
	 *
	 * @access private
	 * @var int
	 * @see StringParser_Node::_children
	 */
	var $_id = -1;
	
	/**
	 * The parent of this node.
	 *
	 * It is either null (root node) or a reference to the parent object.
	 *
	 * @access private
	 * @var mixed
	 * @see StringParser_Node::_children
	 */
	var $_parent = null;
	
	/**
	 * The children of this node.
	 *
	 * It contains an array of references to all the children nodes of this
	 * node.
	 *
	 * @access private
	 * @var array
	 * @see StringParser_Node::_parent
	 */
	var $_children = array ();
	
	/**
	 * Occured at
	 *
	 * This defines the position in the parsed text where this node occurred
	 * at. If -1, this value was not possible to be determined.
	 *
	 * @access public
	 * @var int
	 */
	var $occurredAt = -1;
	
	/**
	 * Constructor
	 *
	 * Currently, the constructor only allocates a new ID for the node and
	 * assigns it.
	 *
	 * @access public
	 * @param int $occurredAt The position in the text where this node
	 *                        occurred at. If not determinable, it is -1.
	 * @global __STRINGPARSER_NODE_ID
	 */
	function StringParser_Node ($occurredAt = -1) {
		$this->_id = $GLOBALS['__STRINGPARSER_NODE_ID']++;
		$this->occurredAt = $occurredAt;
	}
	
	/**
	 * Type of the node
	 *
	 * This function returns the type of the node
	 *
	 * @access public
	 * @return int
	 */
	function type () {
		return $this->_type;
	}
	
	/**
	 * Prepend a node
	 *
	 * @access public
	 * @param object $node The node to be prepended.
	 * @return bool On success, the function returns true, else false.
	 */
	function prependChild (&$node) {
		if (!is_object ($node)) {
			return false;
		}
		
		// root nodes may not be children of other nodes!
		if ($node->_type == STRINGPARSER_NODE_ROOT) {
			return false;
		}
		
		// if node already has a parent
		if ($node->_parent !== false) {
			// remove node from there
			$parent =& $node->_parent;
			if (!$parent->_removeChild ($node, false)) {
				return false;
			}
			unset ($parent);
		}
		
		$index = count ($this->_children) - 1;
		// move all nodes to a new index
		while ($index >= 0) {
			// save object
			$object =& $this->_children[$index];
			// we have to unset it because else it will be
			// overridden in in the loop
			unset ($this->_children[$index]);
			// put object to new position
			$this->_children[$index+1] =& $object;
			$index--;
		}
		$this->_children[0] =& $node;
		return true;
	}
	
	/**
	 * Append text to last text child
	 * @access public
	 * @param string $text The text to append
	 * @return bool On success, the function returns true, else false
	 */
	function appendToLastTextChild ($text) {
		$ccount = count ($this->_children);
		if ($ccount == 0 || $this->_children[$ccount-1]->_type != STRINGPARSER_NODE_TEXT) {
			$ntextnode =& new StringParser_Node_Text ($text);
			return $this->appendChild ($ntextnode);
		} else {
			$this->_children[$ccount-1]->appendText ($text);
			return true;
		}
	}
	
	/**
	 * Append a node to the children
	 *
	 * This function appends a node to the children array(). It
	 * automatically sets the {@link StrinParser_Node::_parent _parent}
	 * property of the node that is to be appended.
	 *
	 * @access public
	 * @param object $node The node that is to be appended.
	 * @return bool On success, the function returns true, else false.
	 */
	function appendChild (&$node) {
		if (!is_object ($node)) {
			return false;
		}
		
		// root nodes may not be children of other nodes!
		if ($node->_type == STRINGPARSER_NODE_ROOT) {
			return false;
		}
		
		// if node already has a parent
		if ($node->_parent !== null) {
			// remove node from there
			$parent =& $node->_parent;
			if (!$parent->removeChild ($node, false)) {
				return false;
			}
			unset ($parent);
		}
		
		// append it to current node
		$new_index = count ($this->_children);
		$this->_children[$new_index] =& $node;
		$node->_parent =& $this;
		return true;
	}
	
	/**
	 * Insert a node before another node
	 *
	 * @access public
	 * @param object $node The node to be inserted.
	 * @param object $reference The reference node where the new node is
	 *                          to be inserted before.
	 * @return bool On success, the function returns true, else false.
	 */
	function insertChildBefore (&$node, &$reference) {
		if (!is_object ($node)) {
			return false;
		}
		
		// root nodes may not be children of other nodes!
		if ($node->_type == STRINGPARSER_NODE_ROOT) {
			return false;
		}
		
		// is the reference node a child?
		$child = $this->_findChild ($reference);
		
		if ($child === false) {
			return false;
		}
		
		// if node already has a parent
		if ($node->_parent !== null) {
			// remove node from there
			$parent =& $node->_parent;
			if (!$parent->_removeChild ($node, false)) {
				return false;
			}
			unset ($parent);
		}
		
		$index = count ($this->_children) - 1;
		// move all nodes to a new index
		while ($index >= $child) {
			// save object
			$object =& $this->_children[$index];
			// we have to unset it because else it will be
			// overridden in in the loop
			unset ($this->_children[$index]);
			// put object to new position
			$this->_children[$index+1] =& $object;
			$index--;
		}
		$this->_children[$child] =& $node;
		return true;
	}
	
	/**
	 * Insert a node after another node
	 *
	 * @access public
	 * @param object $node The node to be inserted.
	 * @param object $reference The reference node where the new node is
	 *                          to be inserted after.
	 * @return bool On success, the function returns true, else false.
	 */
	function insertChildAfter (&$node, &$reference) {
		if (!is_object ($node)) {
			return false;
		}
		
		// root nodes may not be children of other nodes!
		if ($node->_type == STRINGPARSER_NODE_ROOT) {
			return false;
		}
		
		// is the reference node a child?
		$child = $this->_findChild ($reference);
		
		if ($child === false) {
			return false;
		}
		
		// if node already has a parent
		if ($node->_parent !== false) {
			// remove node from there
			$parent =& $node->_parent;
			if (!$parent->_removeChild ($node, false)) {
				return false;
			}
			unset ($parent);
		}
		
		$index = count ($this->_children) - 1;
		// move all nodes to a new index
		while ($index >= $child + 1) {
			// save object
			$object =& $this->_children[$index];
			// we have to unset it because else it will be
			// overridden in in the loop
			unset ($this->_children[$index]);
			// put object to new position
			$this->_children[$index+1] =& $object;
			$index--;
		}
		$this->_children[$child + 1] =& $node;
		return true;
	}
	
	/**
	 * Remove a child node
	 *
	 * This function removes a child from the children array. A parameter
	 * tells the function whether to destroy the child afterwards or not.
	 * If the specified node is not a child of this node, the function will
	 * return false.
	 *
	 * @access public
	 * @param mixed $child The child to destroy; either an integer
	 *                     specifying the index of the child or a reference
	 *                     to the child itself.
	 * @param bool $destroy Destroy the child afterwards.
	 * @return bool On success, the function returns true, else false.
	 */
	function removeChild (&$child, $destroy = false) {
		if (is_object ($child)) {
			// if object: get index
			$object =& $child;
			unset ($child);
			$child = $this->_findChild ($object);
			if ($child === false) {
				return false;
			}
		} else {
			// else: get object
			$object =& $this->_children[$child];
		}
		
		// store count for later use
		$ccount = count ($this->_children);
		
		// index out of bounds
		if (!is_int ($child) || $child < 0 || $child >= $ccount) {
			return false;
		}
		
		// inkonsistency
		if ($this->_children[$child]->_parent === null ||
		    $this->_children[$child]->_parent->_id != $this->_id) {
			return false;
		}
		
		// $object->_parent = null would equal to $this = null
		// as $object->_parent is a reference to $this!
		// because of this, we have to unset the variable to remove
		// the reference and then redeclare the variable
		unset ($object->_parent); $object->_parent = null;
		
		// we have to unset it because else it will be overridden in
		// in the loop
		unset ($this->_children[$child]);
		unset ($obj);
		
		// move all remaining objects one index higher
		while ($child < $ccount - 1) {
			// save object
			$obj =& $this->_children[$child+1];
			// we have to unset it because else it will be
			// overridden in in the loop
			unset ($this->_children[$child+1]);
			// put object to new position
			$this->_children[$child] =& $obj;
			// UNSET THE OBJECT!
			unset ($obj);
			$child++;
		}
		
		if ($destroy) {
			return StringParser_Node::destroyNode ($object);
		}
		return true;
	}
	
	/**
	 * Get the first child of this node
	 *
	 * @access public
	 * @return mixed
	 */
	function &firstChild () {
		$ret = null;
		if (!count ($this->_children)) {
			return $ret;
		}
		return $this->_children[0];
	}
	
	/**
	 * Get the last child of this node
	 *
	 * @access public
	 * @return mixed
	 */
	function &lastChild () {
		$ret = null;
		$c = count ($this->_children);
		if (!$c) {
			return $ret;
		}
		return $this->_children[$c-1];
	}
	
	/**
	 * Destroy a node
	 *
	 * @access public
	 * @static
	 * @param object $node The node to destroy
	 * @return bool True on success, else false.
	 */
	function destroyNode (&$node) {
		// if parent exists: remove node from tree!
		if ($node->_parent !== null) {
			$parent =& $node->_parent;
			// directly return that result because the removeChild
			// method will call destroyNode again
			return $parent->removeChild ($node, true);
		}
		
		// node has children
		while (count ($node->_children)) {
			$child = 0;
			// remove first child until no more children remain
			if (!$node->removeChild ($child, true)) {
				return false;
			}
		}
		
		// now call the nodes destructor
		if (!$node->_destroy ()) {
			return false;
		}
		
		// now just unset it and prey that there are no more references
		// to this node
		unset ($node);
		
		return true;
	}
	
	/**
	 * Destroy this node
	 *
	 *
	 * @access private
	 * @return bool True on success, else false.
	 */
	function _destroy () {
		return true;
	}
	
	/** 
	 * Find a child node
	 *
	 * This function searches for a node in the own children and returns
	 * the index of the node or false if the node is not a child of this
	 * node.
	 *
	 * @access private
	 * @param mixed $child The node to look for.
	 * @return mixed The index of the child node on success, else false.
	 */
	function _findChild (&$child) {
		if (!is_object ($child)) {
			return false;
		}
		
		$ccount = count ($this->_children);
		for ($i = 0; $i < $ccount; $i++) {
			if ($this->_children[$i]->_id == $child->_id) {
				return $i;
			}
		}
		
		return false;
	}
	
	/** 
	 * Checks equality of this node and another node
	 *
	 * @access public
	 * @param mixed $node The node to be compared with
	 * @return bool True if the other node equals to this node, else false.
	 */
	function equals (&$node) {
		return ($this->_id == $node->_id);
	}
	
	/**
	 * Determines whether a criterium matches this node
	 *
	 * @access public
	 * @param string $criterium The criterium that is to be checked
	 * @param mixed $value The value that is to be compared
	 * @return bool True if this node matches that criterium
	 */
	function matchesCriterium ($criterium, $value) {
		return false;
	}
	
	/**
	 * Search for nodes with a certain criterium
	 *
	 * This may be used to implement getElementsByTagName etc.
	 *
	 * @access public
	 * @param string $criterium The criterium that is to be checked
	 * @param mixed $value The value that is to be compared
	 * @return array All subnodes that match this criterium
	 */
	function getNodesByCriterium ($criterium, $value) {
		$nodes = array ();
		$node_ctr = 0;
		for ($i = 0; $i < count ($this->_children); $i++) {
			if ($this->_children[$i]->matchesCriterium ($criterium, $value)) {
				$nodes[$node_ctr++] =& $this->_children[$i];
			}
			$subnodes = $this->_children[$i]->getNodesByCriterium ($criterium, $value);
			if (count ($subnodes)) {
				$subnodes_count = count ($subnodes);
				for ($j = 0; $j < $subnodes_count; $j++) {
					$nodes[$node_ctr++] =& $subnodes[$j];
					unset ($subnodes[$j]);
				}
			}
			unset ($subnodes);
		}
		return $nodes;
	}
	
	/**
	 * Search for nodes with a certain criterium and return the count
	 *
	 * Similar to getNodesByCriterium
	 *
	 * @access public
	 * @param string $criterium The criterium that is to be checked
	 * @param mixed $value The value that is to be compared
	 * @return int The number of subnodes that match this criterium
	 */
	function getNodeCountByCriterium ($criterium, $value) {
		$node_ctr = 0;
		for ($i = 0; $i < count ($this->_children); $i++) {
			if ($this->_children[$i]->matchesCriterium ($criterium, $value)) {
				$node_ctr++;
			}
			$subnodes = $this->_children[$i]->getNodeCountByCriterium ($criterium, $value);
			$node_ctr += $subnodes;
		}
		return $node_ctr;
	}
	
	/**
	 * Dump nodes
	 *
	 * This dumps a tree of nodes
	 *
	 * @access public
	 * @param string $prefix The prefix that is to be used for indentation
	 * @param string $linesep The line separator
	 * @param int $level The initial level of indentation
	 * @return string
	 */
	function dump ($prefix = " ", $linesep = "\n", $level = 0) {
		$str = str_repeat ($prefix, $level) . $this->_id . ": " . $this->_dumpToString () . $linesep;
		for ($i = 0; $i < count ($this->_children); $i++) {
			$str .= $this->_children[$i]->dump ($prefix, $linesep, $level + 1);
		}
		return $str;
	}
	
	/**
	 * Dump this node to a string
	 *
	 * @access protected
	 * @return string
	 */
	function _dumpToString () {
		if ($this->_type == STRINGPARSER_NODE_ROOT) {
			return "root";
		}
		return (string)$this->_type;
	}
}

/**
 * String parser root node class
 *
 * @package stringparser
 */
class StringParser_Node_Root extends StringParser_Node {
	/**
	 * The type of this node.
	 * 
	 * This node is a root node.
	 *
	 * @access private
	 * @var int
	 * @see STRINGPARSER_NODE_ROOT
	 */
	var $_type = STRINGPARSER_NODE_ROOT;
}

/**
 * String parser text node class
 *
 * @package stringparser
 */
class StringParser_Node_Text extends StringParser_Node {
	/**
	 * The type of this node.
	 * 
	 * This node is a text node.
	 *
	 * @access private
	 * @var int
	 * @see STRINGPARSER_NODE_TEXT
	 */
	var $_type = STRINGPARSER_NODE_TEXT;
	
	/**
	 * Node flags
	 * 
	 * @access private
	 * @var array
	 */
	var $_flags = array ();
	
	/**
	 * The content of this node
	 * @access public
	 * @var string
	 */
	var $content = '';
	
	/**
	 * Constructor
	 *
	 * @access public
	 * @param string $content The initial content of this element
	 * @param int $occurredAt The position in the text where this node
	 *                        occurred at. If not determinable, it is -1.
	 * @see StringParser_Node_Text::content
	 */
	function StringParser_Node_Text ($content, $occurredAt = -1) {
		parent::StringParser_Node ($occurredAt);
		$this->content = $content;
	}
	
	/**
	 * Append text to content
	 *
	 * @access public
	 * @param string $text The text to append
	 * @see StringParser_Node_Text::content
	 */
	function appendText ($text) {
		$this->content .= $text;
	}
	
	/**
	 * Set a flag
	 *
	 * @access public
	 * @param string $name The name of the flag
	 * @param mixed $value The value of the flag
	 */
	function setFlag ($name, $value) {
		$this->_flags[$name] = $value;
		return true;
	}
	
	/**
	 * Get Flag
	 *
	 * @access public
	 * @param string $flag The requested flag
	 * @param string $type The requested type of the return value
	 * @param mixed $default The default return value
	 */
	function getFlag ($flag, $type = 'mixed', $default = null) {
		if (!isset ($this->_flags[$flag])) {
			return $default;
		}
		$return = $this->_flags[$flag];
		if ($type != 'mixed') {
			settype ($return, $type);
		}
		return $return;
	}
	
	/**
	 * Dump this node to a string
	 */
	function _dumpToString () {
		return "text \"".substr (preg_replace ('/\s+/', ' ', $this->content), 0, 40)."\" [f:".preg_replace ('/\s+/', ' ', join(':', array_keys ($this->_flags)))."]";
	}
}

?>