<?php

/*

 * This file is part of the Symfony package.

 *

 * (c) Fabien Potencier <fabien@symfony.com>

 *

 * For the full copyright and license information, please view the LICENSE

 * file that was distributed with this source code.

 */

namespace Symfony\Component\BrowserKit;

/**

 * History.

 *

 * @author Fabien Potencier <fabien@symfony.com>

 */

class History

{

    protected $stack = array();

    protected $position = -1;

    /**

     * Constructor.

     */

    public function __construct()

    {

        $this->clear();

    }

    /**

     * Clears the history.

     */

    public function clear()

    {

        $this->stack = array();

        $this->position = -1;

    }

    /**

     * Adds a Request to the history.

     *

     * @param Request $request A Request instance

     */

    public function add(Request $request)

    {

        $this->stack = array_slice($this->stack, 0, $this->position + 1);

        $this->stack[] = clone $request;

        $this->position = count($this->stack) - 1;

    }

    /**

     * Returns true if the history is empty.

     *

     * @return Boolean true if the history is empty, false otherwise

     */

    public function isEmpty()

    {

        return count($this->stack) == 0;

    }

    /**

     * Goes back in the history.

     *

     * @return Request A Request instance

     *

     * @throws \LogicException if the stack is already on the first page

     */

    public function back()

    {

        if ($this->position < 1) {

            throw new \LogicException('You are already on the first page.');

        }

        return clone $this->stack[--$this->position];

    }

    /**

     * Goes forward in the history.

     *

     * @return Request A Request instance

     *

     * @throws \LogicException if the stack is already on the last page

     */

    public function forward()

    {

        if ($this->position > count($this->stack) - 2) {

            throw new \LogicException('You are already on the last page.');

        }

        return clone $this->stack[++$this->position];

    }

    /**

     * Returns the current element in the history.

     *

     * @return Request A Request instance

     *

     * @throws \LogicException if the stack is empty

     */

    public function current()

    {

        if (-1 == $this->position) {

            throw new \LogicException('The page history is empty.');

        }

        return clone $this->stack[$this->position];

    }

}