/src/lib/engines/simple_parser_engine.php

<?php

/**
 * Simple Parser Engine
 * Finds text between given delimiters and evaluates the enclosed buffer.
 * ---
 * Written by Jose Carlos Nieto <xiam@menteslibres.org>
 * Copyright (c) 2007 Astrata Software S.A. de C.V.
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @author          Jose Carlos Nieto <xiam@menteslibres.org>
 * @copyright       Copyright (c) 2007-2008, Astrata Software S.A. de C.V.
 * @link            http://opensource.astrata.com.mx Astrata Open Source Projects
 * @version         $Revision: $
 * @modifiedby      $LastChangedBy: $
 * @lastmodified    $Date: $
 * @license         http://www.opensource.org/licenses/mit-license.php The MIT License
 *
 */

class simple_parser_engine extends tm_object {
  
  public $escape_char = null;
  public $delimiters = array();
  public $use_stack = false;
  public $recursive = true;
  
  public function set_delimiters($arr) {
    $this->delimiters = $arr;
  }

  public function eval_enclosed($buff, $delimiter) {
    return $buff;
  }

  public function parse(&$buff) {

    $stack = array();

    $search_for_index = -1;

    for ($i = 0; isset($buff[$i]); $i++) {

      foreach ($this->delimiters as $index => $delimiter) {

        if ($search_for_index == -1 || $search_for_index == $index) {

          // escape sequences
          if ($search_for_index == -1 && $this->escape_char) {
            if ($buff[$i] == $this->escape_char && isset($buff[$i+1])) {
              $break = false;
              // checking if this escape sequence is before a delimiting character
              for ($j = 0; $break == false && $j <= 1; $j++) {
                if ($buff[$i+1] == $delimiter[$j]{0}) {
                  $buff = substr($buff, 0, $i).substr($buff, $i + 1);
                  $break = true;
                }
              }
              if ($break) {
                break;
              }
            }
          }

          // lenght of start delimiter
          $len    = strlen($delimiter[0]);
          $match  = ($len > 0);

          if ($match && isset($buff[$i+$len-1])) {
            for ($j = 0; $match && $j < $len; $j++) {
              if ($buff[$i+$j] != $delimiter[0][$j]) {
                $match = false;
              }
            }
            if ($match) {
              if (!$stack) {
                $search_for_index = $index;
              }
              array_push($stack, $i);
              $i = $i + $len;
              $i = $i - 1;
              break;
            }
          }

          if ($stack) {
          
            // length of ending delimiter
            $len    = strlen($delimiter[1]);
            $match  = ($len > 0);

            if ($match && isset($buff[$i+$len-1])) {
              for ($j = 0; $match && $j < $len; $j++) {
                if ($buff[$i+$j] != $delimiter[1][$j]) {
                  $match = false;
                }
              }

              if ($match) {

                // what did we close?
                $start = array_pop($stack);

                if (substr($buff, $start, strlen($delimiter[0])) == $delimiter[0]) {
                  
                  $i = $i + $len;

                  $portion = substr($buff, $start, $i - $start);

                  if ($this->recursive) {
                    if ($stack) {
                      // silently discarding this break point
                      $i -= 1;
                      break;
                    } else {
                      $portion = substr($portion, strlen($delimiter[0]), -1*strlen($delimiter[1]));
                      if ($this->parse($portion)) {
                        $portion = $delimiter[0].$portion.$delimiter[1];
                        $search_for_index = -1;
                      } else {
                        debug('PANIC!');
                        return false;
                      }
                    }
                  }

                  $portion = $this->eval_enclosed($portion, $delimiter); 

                  $search_for_index = -1;

                  $buff = substr($buff, 0, $start).$portion.substr($buff, $i);

                  $i = $start + strlen($portion);
                  
                  $i = $i - 1;

                } else {
                  array_push($stack, $start);
                }
              }
            }
          }
        }
      }
    }

    if ($stack) { 
      debug("Filter syntax error near '".substr($buff, array_pop($stack), 60)."'");
      return false;
    }

    return true;
  }
}
?>