<?php

namespace PhpOffice\PhpSpreadsheet\CalcEngine;

/**
 * Copyright (c) 2006 - 2016 PhpSpreadsheet.
 *
 * 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   PhpSpreadsheet
 *
 * @copyright  Copyright (c) 2006 - 2016 PhpSpreadsheet (https://github.com/PHPOffice/PhpSpreadsheet)
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
 */
class CyclicReferenceStack
{
    /**
     * The call stack for calculated cells.
     *
     * @var mixed[]
     */
    private $stack = [];

    /**
     * Return the number of entries on the stack.
     *
     * @return int
     */
    public function count()
    {
        return count($this->stack);
    }

    /**
     * Push a new entry onto the stack.
     *
     * @param mixed $value
     */
    public function push($value)
    {
        $this->stack[$value] = $value;
    }

    /**
     * Pop the last entry from the stack.
     *
     * @return mixed
     */
    public function pop()
    {
        return array_pop($this->stack);
    }

    /**
     * Test to see if a specified entry exists on the stack.
     *
     * @param mixed $value The value to test
     */
    public function onStack($value)
    {
        return isset($this->stack[$value]);
    }

    /**
     * Clear the stack.
     */
    public function clear()
    {
        $this->stack = [];
    }

    /**
     * Return an array of all entries on the stack.
     *
     * @return mixed[]
     */
    public function showStack()
    {
        return $this->stack;
    }
}