<?php

/*

 * This file is part of Twig.

 *

 * (c) 2010 Fabien Potencier

 *

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

 * file that was distributed with this source code.

 */

/**

 * Twig_NodeVisitor_Optimizer tries to optimizes the AST.

 *

 * This visitor is always the last registered one.

 *

 * You can configure which optimizations you want to activate via the

 * optimizer mode.

 *

 * @package twig

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

 */

class Twig_NodeVisitor_Optimizer implements Twig_NodeVisitorInterface

{

    const OPTIMIZE_ALL         = -1;

    const OPTIMIZE_NONE        = 0;

    const OPTIMIZE_FOR         = 2;

    const OPTIMIZE_RAW_FILTER  = 4;

    protected $loops = array();

    protected $optimizers;

    /**

     * Constructor.

     *

     * @param integer $optimizers The optimizer mode

     */

    public function __construct($optimizers = -1)

    {

        if (!is_int($optimizers) || $optimizers > 2) {

            throw new InvalidArgumentException(sprintf('Optimizer mode "%s" is not valid.', $optimizers));

        }

        $this->optimizers = $optimizers;

    }

    /**

     * {@inheritdoc}

     */

    public function enterNode(Twig_NodeInterface $node, Twig_Environment $env)

    {

        if (self::OPTIMIZE_FOR === (self::OPTIMIZE_FOR & $this->optimizers)) {

            $this->enterOptimizeFor($node, $env);

        }

        return $node;

    }

    /**

     * {@inheritdoc}

     */

    public function leaveNode(Twig_NodeInterface $node, Twig_Environment $env)

    {

        if (self::OPTIMIZE_FOR === (self::OPTIMIZE_FOR & $this->optimizers)) {

            $this->leaveOptimizeFor($node, $env);

        }

        if (self::OPTIMIZE_RAW_FILTER === (self::OPTIMIZE_RAW_FILTER & $this->optimizers)) {

            $node = $this->optimizeRawFilter($node, $env);

        }

        $node = $this->optimizeRenderBlock($node, $env);

        return $node;

    }

    /**

     * Replaces "echo $this->renderBlock()" with "$this->displayBlock()".

     *

     * @param Twig_NodeInterface $node A Node

     * @param Twig_Environment   $env  The current Twig environment

     */

    protected function optimizeRenderBlock($node, $env)

    {

        if ($node instanceof Twig_Node_Print && $node->getNode('expr') instanceof Twig_Node_Expression_BlockReference) {

            $node->getNode('expr')->setAttribute('output', true);

            return $node->getNode('expr');

        }

        return $node;

    }

    /**

     * Removes "raw" filters.

     *

     * @param Twig_NodeInterface $node A Node

     * @param Twig_Environment   $env  The current Twig environment

     */

    protected function optimizeRawFilter($node, $env)

    {

        if ($node instanceof Twig_Node_Expression_Filter && 'raw' == $node->getNode('filter')->getAttribute('value')) {

            return $node->getNode('node');

        }

        return $node;

    }

    /**

     * Optimizes "for" tag by removing the "loop" variable creation whenever possible.

     *

     * @param Twig_NodeInterface $node A Node

     * @param Twig_Environment   $env  The current Twig environment

     */

    protected function enterOptimizeFor($node, $env)

    {

        if ($node instanceof Twig_Node_For) {

            // disable the loop variable by default

            $node->setAttribute('with_loop', false);

            array_unshift($this->loops, $node);

        } elseif (!$this->loops) {

            // we are outside a loop

            return;

        }

        // when do we need to add the loop variable back?

        // the loop variable is referenced for the current loop

        elseif ($node instanceof Twig_Node_Expression_Name && 'loop' === $node->getAttribute('name')) {

            $this->addLoopToCurrent();

        }

        // block reference

        elseif ($node instanceof Twig_Node_BlockReference || $node instanceof Twig_Node_Expression_BlockReference) {

            $this->addLoopToCurrent();

        }

        // include without the only attribute

        elseif ($node instanceof Twig_Node_Include && !$node->getAttribute('only')) {

            $this->addLoopToAll();

        }

        // the loop variable is referenced via an attribute

        elseif ($node instanceof Twig_Node_Expression_GetAttr

            && (!$node->getNode('attribute') instanceof Twig_Node_Expression_Constant

                || 'parent' === $node->getNode('attribute')->getAttribute('value')

               )

            && (true === $this->loops[0]->getAttribute('with_loop')

                || ($node->getNode('node') instanceof Twig_Node_Expression_Name

                    && 'loop' === $node->getNode('node')->getAttribute('name')

                   )

               )

        ) {

            $this->addLoopToAll();

        }

    }

    /**

     * Optimizes "for" tag by removing the "loop" variable creation whenever possible.

     *

     * @param Twig_NodeInterface $node A Node

     * @param Twig_Environment   $env  The current Twig environment

     */

    protected function leaveOptimizeFor($node, $env)

    {

        if ($node instanceof Twig_Node_For) {

            array_shift($this->loops);

        }

    }

    protected function addLoopToCurrent()

    {

        $this->loops[0]->setAttribute('with_loop', true);

    }

    protected function addLoopToAll()

    {

        foreach ($this->loops as $loop) {

            $loop->setAttribute('with_loop', true);

        }

    }

    /**

     * {@inheritdoc}

     */

    public function getPriority()

    {

        return 255;

    }

}