<?php

class Twig_NodeVisitor_SafeAnalysis implements Twig_NodeVisitorInterface

{

    protected $data = array();

    public function getSafe(Twig_NodeInterface $node)

    {

        $hash = spl_object_hash($node);

        if (isset($this->data[$hash])) {

            foreach($this->data[$hash] as $bucket) {

                if ($bucket['key'] === $node) {

                    return $bucket['value'];

                }

            }

        }

        return null;

    }

    protected function setSafe(Twig_NodeInterface $node, array $safe)

    {

        $hash = spl_object_hash($node);

        if (isset($this->data[$hash])) {

            foreach($this->data[$hash] as &$bucket) {

                if ($bucket['key'] === $node) {

                    $bucket['value'] = $safe;

                    return;

                }

            }

        }

        $this->data[$hash][] = array(

            'key' => $node,

            'value' => $safe,

        );

    }

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

    {

        return $node;

    }

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

    {

        if ($node instanceof Twig_Node_Expression_Constant) {

            // constants are marked safe for all

            $this->setSafe($node, array('all'));

        } elseif ($node instanceof Twig_Node_Expression_BlockReference) {

            // blocks are safe by definition

            $this->setSafe($node, array('all'));

        } elseif ($node instanceof Twig_Node_Expression_Parent) {

            // parent block is safe by definition

            $this->setSafe($node, array('all'));

        } elseif ($node instanceof Twig_Node_Expression_Conditional) {

            // intersect safeness of both operands

            $safe = $this->intersectSafe($this->getSafe($node->getNode('expr2')), $this->getSafe($node->getNode('expr3')));

            $this->setSafe($node, $safe);

        } elseif ($node instanceof Twig_Node_Expression_Filter) {

            // filter expression is safe when the filter is safe

            $name = $node->getNode('filter')->getAttribute('value');

            $args = $node->getNode('arguments');

            if (false !== $filter = $env->getFilter($name)) {

                $this->setSafe($node, $filter->getSafe($args));

            } else {

                $this->setSafe($node, array());

            }

        } elseif ($node instanceof Twig_Node_Expression_Function) {

            // function expression is safe when the function is safe

            $name = $node->getNode('name')->getAttribute('name');

            $args = $node->getNode('arguments');

            $function = $env->getFunction($name);

            if (false !== $function) {

                $this->setSafe($node, $function->getSafe($args));

            } else {

                $this->setSafe($node, array());

            }

        } else {

            $this->setSafe($node, array());

        }

        return $node;

    }

    protected function intersectSafe(array $a = null, array $b = null)

    {

        if (null === $a || null === $b) {

            return array();

        }

        if (in_array('all', $a)) {

            return $b;

        }

        if (in_array('all', $b)) {

            return $a;

        }

        return array_intersect($a, $b);

    }

    /**

     * {@inheritdoc}

     */

    public function getPriority()

    {

        return 0;

    }

}