<?php

/*

 * This file is part of Twig.

 *

 * (c) 2009 Fabien Potencier

 *

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

 * file that was distributed with this source code.

 */

/**

 * Twig_NodeTraverser is a node traverser.

 *

 * It visits all nodes and their children and call the given visitor for each.

 *

 * @package    twig

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

 */

class Twig_NodeTraverser

{

    protected $env;

    protected $visitors;

    /**

     * Constructor.

     *

     * @param Twig_Environment $env      A Twig_Environment instance

     * @param array            $visitors An array of Twig_NodeVisitorInterface instances

     */

    public function __construct(Twig_Environment $env, array $visitors = array())

    {

        $this->env = $env;

        $this->visitors = array();

        foreach ($visitors as $visitor) {

            $this->addVisitor($visitor);

        }

    }

    /**

     * Adds a visitor.

     *

     * @param Twig_NodeVisitorInterface $visitor A Twig_NodeVisitorInterface instance

     */

    public function addVisitor(Twig_NodeVisitorInterface $visitor)

    {

        if (!isset($this->visitors[$visitor->getPriority()])) {

            $this->visitors[$visitor->getPriority()] = array();

        }

        $this->visitors[$visitor->getPriority()][] = $visitor;

    }

    /**

     * Traverses a node and calls the registered visitors.

     *

     * @param Twig_NodeInterface $node A Twig_NodeInterface instance

     */

    public function traverse(Twig_NodeInterface $node)

    {

        ksort($this->visitors);

        foreach ($this->visitors as $visitors) {

            foreach ($visitors as $visitor) {

                $node = $this->traverseForVisitor($visitor, $node);

            }

        }

        return $node;

    }

    protected function traverseForVisitor(Twig_NodeVisitorInterface $visitor, Twig_NodeInterface $node = null)

    {

        if (null === $node) {

            return null;

        }

        $node = $visitor->enterNode($node, $this->env);

        foreach ($node as $k => $n) {

            if (false !== $n = $this->traverseForVisitor($visitor, $n)) {

                $node->setNode($k, $n);

            } else {

                $node->removeNode($k);

            }

        }

        return $visitor->leaveNode($node, $this->env);

    }

}