<?php

/**
 * PHPExcel_Calculation_Token_Stack
 *
 * Copyright (c) 2006 - 2015 PHPExcel
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category   PHPExcel
 * @package    PHPExcel_Calculation
 * @copyright  Copyright (c) 2006 - 2015 PHPExcel (http://www.codeplex.com/PHPExcel)
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
 * @version    ##VERSION##, ##DATE##
 */
class PHPExcel_Calculation_Token_Stack
{
  /**
   * The parser stack for formulae
   *
   * @var mixed[]
   */
  private $stack = array ();
  
  /**
   * Count of entries in the parser stack
   *
   * @var integer
   */
  private $count = 0;
  
  /**
   * Return the number of entries on the stack
   *
   * @return integer
   */
  public function count()
  {
    return $this->count;
  }
  
  /**
   * Push a new entry onto the stack
   *
   * @param mixed $type          
   * @param mixed $value          
   * @param mixed $reference          
   */
  public function push($type, $value, $reference = null)
  {
    $this->stack [$this->count ++] = array (
        'type' => $type,
        'value' => $value,
        'reference' => $reference 
    );
    if ($type == 'Function')
    {
      $localeFunction = PHPExcel_Calculation::localeFunc ( $value );
      if ($localeFunction != $value)
      {
        $this->stack [($this->count - 1)] ['localeValue'] = $localeFunction;
      }
    }
  }
  
  /**
   * Pop the last entry from the stack
   *
   * @return mixed
   */
  public function pop()
  {
    if ($this->count > 0)
    {
      return $this->stack [-- $this->count];
    }
    return null;
  }
  
  /**
   * Return an entry from the stack without removing it
   *
   * @param integer $n
   *          number indicating how far back in the stack we want to look
   * @return mixed
   */
  public function last($n = 1)
  {
    if ($this->count - $n < 0)
    {
      return null;
    }
    return $this->stack [$this->count - $n];
  }
  
  /**
   * Clear the stack
   */
  public function clear()
  {
    $this->stack = array ();
    $this->count = 0;
  }
}
