<?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_NodeVisitor_Escaper implements output escaping.
 *
 * @author Fabien Potencier <fabien@symfony.com>
 */
class Twig_NodeVisitor_Escaper extends Twig_BaseNodeVisitor
{
  protected $statusStack = [];
  protected $blocks = [];
  protected $safeAnalysis;
  protected $traverser;
  protected $defaultStrategy = false;
  protected $safeVars = [];

  public function __construct()
  {
    $this->safeAnalysis = new Twig_NodeVisitor_SafeAnalysis();
  }

  /**
   * {@inheritdoc}
   */
  protected function doEnterNode(Twig_Node $node, Twig_Environment $env)
  {
    if ($node instanceof Twig_Node_Module) {
      if ($env->hasExtension('escaper') && ($defaultStrategy = $env->getExtension('escaper')->getDefaultStrategy($node->getAttribute('filename')))) {
        $this->defaultStrategy = $defaultStrategy;
      }
      $this->safeVars = [];
    } elseif ($node instanceof Twig_Node_AutoEscape) {
      $this->statusStack[] = $node->getAttribute('value');
    } elseif ($node instanceof Twig_Node_Block) {
      $this->statusStack[] = isset($this->blocks[$node->getAttribute('name')]) ? $this->blocks[$node->getAttribute('name')] : $this->needEscaping($env);
    } elseif ($node instanceof Twig_Node_Import) {
      $this->safeVars[] = $node->getNode('var')->getAttribute('name');
    }

    return $node;
  }

  /**
   * {@inheritdoc}
   */
  protected function doLeaveNode(Twig_Node $node, Twig_Environment $env)
  {
    if ($node instanceof Twig_Node_Module) {
      $this->defaultStrategy = false;
      $this->safeVars = [];
    } elseif ($node instanceof Twig_Node_Expression_Filter) {
      return $this->preEscapeFilterNode($node, $env);
    } elseif ($node instanceof Twig_Node_Print) {
      return $this->escapePrintNode($node, $env, $this->needEscaping($env));
    }

    if ($node instanceof Twig_Node_AutoEscape || $node instanceof Twig_Node_Block) {
      array_pop($this->statusStack);
    } elseif ($node instanceof Twig_Node_BlockReference) {
      $this->blocks[$node->getAttribute('name')] = $this->needEscaping($env);
    }

    return $node;
  }

  protected function escapePrintNode(Twig_Node_Print $node, Twig_Environment $env, $type)
  {
    if (false === $type) {
      return $node;
    }

    $expression = $node->getNode('expr');

    if ($this->isSafeFor($type, $expression, $env)) {
      return $node;
    }

    $class = get_class($node);

    return new $class($this->getEscaperFilter($type, $expression), $node->getLine());
  }

  protected function preEscapeFilterNode(Twig_Node_Expression_Filter $filter, Twig_Environment $env)
  {
    $name = $filter->getNode('filter')->getAttribute('value');

    $type = $env->getFilter($name)->getPreEscape();
    if (null === $type) {
      return $filter;
    }

    $node = $filter->getNode('node');
    if ($this->isSafeFor($type, $node, $env)) {
      return $filter;
    }

    $filter->setNode('node', $this->getEscaperFilter($type, $node));

    return $filter;
  }

  protected function isSafeFor($type, Twig_NodeInterface $expression, $env)
  {
    $safe = $this->safeAnalysis->getSafe($expression);

    if (null === $safe) {
      if (null === $this->traverser) {
        $this->traverser = new Twig_NodeTraverser($env, [$this->safeAnalysis]);
      }

      $this->safeAnalysis->setSafeVars($this->safeVars);

      $this->traverser->traverse($expression);
      $safe = $this->safeAnalysis->getSafe($expression);
    }

    return in_array($type, $safe) || in_array('all', $safe);
  }

  protected function needEscaping(Twig_Environment $env)
  {
    if (count($this->statusStack)) {
      return $this->statusStack[count($this->statusStack) - 1];
    }

    return $this->defaultStrategy ? $this->defaultStrategy : false;
  }

  protected function getEscaperFilter($type, Twig_NodeInterface $node)
  {
    $line = $node->getLine();
    $name = new Twig_Node_Expression_Constant('escape', $line);
    $args = new Twig_Node([new Twig_Node_Expression_Constant((string) $type, $line), new Twig_Node_Expression_Constant(null, $line), new Twig_Node_Expression_Constant(true, $line)]);

    return new Twig_Node_Expression_Filter($node, $name, $args, $line);
  }

  /**
   * {@inheritdoc}
   */
  public function getPriority()
  {
    return 0;
  }
}
