<?php

/*

 * This file is part of Twig.

 *

 * (c) 2009 Fabien Potencier

 * (c) 2009 Armin Ronacher

 *

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

 * file that was distributed with this source code.

 */

/**

 * Parses expressions.

 *

 * This parser implements a "Precedence climbing" algorithm.

 *

 * @see http://www.engr.mun.ca/~theo/Misc/exp_parsing.htm

 * @see http://en.wikipedia.org/wiki/Operator-precedence_parser

 *

 * @package    twig

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

 */

class Twig_ExpressionParser

{

    const OPERATOR_LEFT = 1;

    const OPERATOR_RIGHT = 2;

    protected $parser;

    protected $unaryOperators;

    protected $binaryOperators;

    public function __construct(Twig_Parser $parser, array $unaryOperators, array $binaryOperators)

    {

        $this->parser = $parser;

        $this->unaryOperators = $unaryOperators;

        $this->binaryOperators = $binaryOperators;

    }

    public function parseExpression($precedence = 0)

    {

        $expr = $this->getPrimary();

        $token = $this->parser->getCurrentToken();

        while ($this->isBinary($token) && $this->binaryOperators[$token->getValue()]['precedence'] >= $precedence) {

            $op = $this->binaryOperators[$token->getValue()];

            $this->parser->getStream()->next();

            if (isset($op['callable'])) {

                $expr = call_user_func($op['callable'], $this->parser, $expr);

            } else {

                $expr1 = $this->parseExpression(self::OPERATOR_LEFT === $op['associativity'] ? $op['precedence'] + 1 : $op['precedence']);

                $class = $op['class'];

                $expr = new $class($expr, $expr1, $token->getLine());

            }

            $token = $this->parser->getCurrentToken();

        }

        if (0 === $precedence) {

            return $this->parseConditionalExpression($expr);

        }

        return $expr;

    }

    protected function getPrimary()

    {

        $token = $this->parser->getCurrentToken();

        if ($this->isUnary($token)) {

            $operator = $this->unaryOperators[$token->getValue()];

            $this->parser->getStream()->next();

            $expr = $this->parseExpression($operator['precedence']);

            $class = $operator['class'];

            return $this->parsePostfixExpression(new $class($expr, $token->getLine()));

        } elseif ($token->test(Twig_Token::PUNCTUATION_TYPE, '(')) {

            $this->parser->getStream()->next();

            $expr = $this->parseExpression();

            $this->parser->getStream()->expect(Twig_Token::PUNCTUATION_TYPE, ')', 'An opened parenthesis is not properly closed');

            return $this->parsePostfixExpression($expr);

        }

        return $this->parsePrimaryExpression();

    }

    protected function parseConditionalExpression($expr)

    {

        while ($this->parser->getStream()->test(Twig_Token::PUNCTUATION_TYPE, '?')) {

            $this->parser->getStream()->next();

            $expr2 = $this->parseExpression();

            $this->parser->getStream()->expect(Twig_Token::PUNCTUATION_TYPE, ':', 'The ternary operator must have a default value');

            $expr3 = $this->parseExpression();

            $expr = new Twig_Node_Expression_Conditional($expr, $expr2, $expr3, $this->parser->getCurrentToken()->getLine());

        }

        return $expr;

    }

    protected function isUnary(Twig_Token $token)

    {

        return $token->test(Twig_Token::OPERATOR_TYPE) && isset($this->unaryOperators[$token->getValue()]);

    }

    protected function isBinary(Twig_Token $token)

    {

        return $token->test(Twig_Token::OPERATOR_TYPE) && isset($this->binaryOperators[$token->getValue()]);

    }

    public function parsePrimaryExpression()

    {

        $token = $this->parser->getCurrentToken();

        switch ($token->getType()) {

            case Twig_Token::NAME_TYPE:

                $this->parser->getStream()->next();

                switch ($token->getValue()) {

                    case 'true':

                    case 'TRUE':

                        $node = new Twig_Node_Expression_Constant(true, $token->getLine());

                        break;

                    case 'false':

                    case 'FALSE':

                        $node = new Twig_Node_Expression_Constant(false, $token->getLine());

                        break;

                    case 'none':

                    case 'NONE':

                    case 'null':

                    case 'NULL':

                        $node = new Twig_Node_Expression_Constant(null, $token->getLine());

                        break;

                    default:

                        $node = new Twig_Node_Expression_Name($token->getValue(), $token->getLine());

                }

                break;

            case Twig_Token::NUMBER_TYPE:

            case Twig_Token::STRING_TYPE:

                $this->parser->getStream()->next();

                $node = new Twig_Node_Expression_Constant($token->getValue(), $token->getLine());

                break;

            default:

                if ($token->test(Twig_Token::PUNCTUATION_TYPE, '[')) {

                    $node = $this->parseArrayExpression();

                } elseif ($token->test(Twig_Token::PUNCTUATION_TYPE, '{')) {

                    $node = $this->parseHashExpression();

                } else {

                    throw new Twig_Error_Syntax(sprintf('Unexpected token "%s" of value "%s"', Twig_Token::typeToEnglish($token->getType(), $token->getLine()), $token->getValue()), $token->getLine());

                }

        }

        return $this->parsePostfixExpression($node);

    }

    public function parseArrayExpression()

    {

        $stream = $this->parser->getStream();

        $stream->expect(Twig_Token::PUNCTUATION_TYPE, '[', 'An array element was expected');

        $elements = array();

        while (!$stream->test(Twig_Token::PUNCTUATION_TYPE, ']')) {

            if (!empty($elements)) {

                $stream->expect(Twig_Token::PUNCTUATION_TYPE, ',', 'An array element must be followed by a comma');

                // trailing ,?

                if ($stream->test(Twig_Token::PUNCTUATION_TYPE, ']')) {

                    break;

                }

            }

            $elements[] = $this->parseExpression();

        }

        $stream->expect(Twig_Token::PUNCTUATION_TYPE, ']', 'An opened array is not properly closed');

        return new Twig_Node_Expression_Array($elements, $stream->getCurrent()->getLine());

    }

    public function parseHashExpression()

    {

        $stream = $this->parser->getStream();

        $stream->expect(Twig_Token::PUNCTUATION_TYPE, '{', 'A hash element was expected');

        $elements = array();

        while (!$stream->test(Twig_Token::PUNCTUATION_TYPE, '}')) {

            if (!empty($elements)) {

                $stream->expect(Twig_Token::PUNCTUATION_TYPE, ',', 'A hash value must be followed by a comma');

                // trailing ,?

                if ($stream->test(Twig_Token::PUNCTUATION_TYPE, '}')) {

                    break;

                }

            }

            if (!$stream->test(Twig_Token::STRING_TYPE) && !$stream->test(Twig_Token::NUMBER_TYPE)) {

                $current = $stream->getCurrent();

                throw new Twig_Error_Syntax(sprintf('A hash key must be a quoted string or a number (unexpected token "%s" of value "%s"', Twig_Token::typeToEnglish($current->getType(), $current->getLine()), $current->getValue()), $current->getLine());

            }

            $key = $stream->next()->getValue();

            $stream->expect(Twig_Token::PUNCTUATION_TYPE, ':', 'A hash key must be followed by a colon (:)');

            $elements[$key] = $this->parseExpression();

        }

        $stream->expect(Twig_Token::PUNCTUATION_TYPE, '}', 'An opened hash is not properly closed');

        return new Twig_Node_Expression_Array($elements, $stream->getCurrent()->getLine());

    }

    public function parsePostfixExpression($node)

    {

        $firstPass = true;

        while (true) {

            $token = $this->parser->getCurrentToken();

            if ($token->getType() == Twig_Token::PUNCTUATION_TYPE) {

                if ('.' == $token->getValue() || '[' == $token->getValue()) {

                    $node = $this->parseSubscriptExpression($node);

                } elseif ('|' == $token->getValue()) {

                    $node = $this->parseFilterExpression($node);

                } elseif ($firstPass && $node instanceof Twig_Node_Expression_Name && '(' == $token->getValue()) {

                    $node = $this->getFunctionNode($node);

                } else {

                    break;

                }

            } else {

                break;

            }

            $firstPass = false;

        }

        return $node;

    }

    public function getFunctionNode(Twig_Node_Expression_Name $node)

    {

        $args = $this->parseArguments();

        if ('parent' === $node->getAttribute('name')) {

            if (!count($this->parser->getBlockStack())) {

                throw new Twig_Error_Syntax('Calling "parent" outside a block is forbidden', $node->getLine());

            }

            if (!$this->parser->getParent()) {

                throw new Twig_Error_Syntax('Calling "parent" on a template that does not extend another one is forbidden', $node->getLine());

            }

            return new Twig_Node_Expression_Parent($this->parser->peekBlockStack(), $node->getLine());

        }

        if ('block' === $node->getAttribute('name')) {

            return new Twig_Node_Expression_BlockReference($args->getNode(0), false, $node->getLine());

        }

        if (null !== $alias = $this->parser->getImportedFunction($node->getAttribute('name'))) {

            return new Twig_Node_Expression_GetAttr($alias['node'], new Twig_Node_Expression_Constant($alias['name'], $node->getLine()), $args, Twig_TemplateInterface::METHOD_CALL, $node->getLine());

        }

        return new Twig_Node_Expression_Function($node, $args, $node->getLine());

    }

    public function parseSubscriptExpression($node)

    {

        $token = $this->parser->getStream()->next();

        $lineno = $token->getLine();

        $arguments = new Twig_Node();

        $type = Twig_TemplateInterface::ANY_CALL;

        if ($token->getValue() == '.') {

            $token = $this->parser->getStream()->next();

            if (

                $token->getType() == Twig_Token::NAME_TYPE

                ||

                $token->getType() == Twig_Token::NUMBER_TYPE

                ||

                ($token->getType() == Twig_Token::OPERATOR_TYPE && preg_match(Twig_Lexer::REGEX_NAME, $token->getValue()))

            ) {

                $arg = new Twig_Node_Expression_Constant($token->getValue(), $lineno);

                if ($this->parser->getStream()->test(Twig_Token::PUNCTUATION_TYPE, '(')) {

                    $type = Twig_TemplateInterface::METHOD_CALL;

                    $arguments = $this->parseArguments();

                } else {

                    $arguments = new Twig_Node();

                }

            } else {

                throw new Twig_Error_Syntax('Expected name or number', $lineno);

            }

        } else {

            $type = Twig_TemplateInterface::ARRAY_CALL;

            $arg = $this->parseExpression();

            $this->parser->getStream()->expect(Twig_Token::PUNCTUATION_TYPE, ']');

        }

        return new Twig_Node_Expression_GetAttr($node, $arg, $arguments, $type, $lineno);

    }

    public function parseFilterExpression($node)

    {

        $this->parser->getStream()->next();

        return $this->parseFilterExpressionRaw($node);

    }

    public function parseFilterExpressionRaw($node, $tag = null)

    {

        while (true) {

            $token = $this->parser->getStream()->expect(Twig_Token::NAME_TYPE);

            $name = new Twig_Node_Expression_Constant($token->getValue(), $token->getLine());

            if (!$this->parser->getStream()->test(Twig_Token::PUNCTUATION_TYPE, '(')) {

                $arguments = new Twig_Node();

            } else {

                $arguments = $this->parseArguments();

            }

            $node = new Twig_Node_Expression_Filter($node, $name, $arguments, $token->getLine(), $tag);

            if (!$this->parser->getStream()->test(Twig_Token::PUNCTUATION_TYPE, '|')) {

                break;

            }

            $this->parser->getStream()->next();

        }

        return $node;

    }

    public function parseArguments()

    {

        $args = array();

        $stream = $this->parser->getStream();

        $stream->expect(Twig_Token::PUNCTUATION_TYPE, '(', 'A list of arguments must be opened by a parenthesis');

        while (!$stream->test(Twig_Token::PUNCTUATION_TYPE, ')')) {

            if (!empty($args)) {

                $stream->expect(Twig_Token::PUNCTUATION_TYPE, ',', 'Arguments must be separated by a comma');

            }

            $args[] = $this->parseExpression();

        }

        $stream->expect(Twig_Token::PUNCTUATION_TYPE, ')', 'A list of arguments must be closed by a parenthesis');

        return new Twig_Node($args);

    }

    public function parseAssignmentExpression()

    {

        $targets = array();

        while (true) {

            $token = $this->parser->getStream()->expect(Twig_Token::NAME_TYPE, null, 'Only variables can be assigned to');

            if (in_array($token->getValue(), array('true', 'false', 'none'))) {

                throw new Twig_Error_Syntax(sprintf('You cannot assign a value to "%s"', $token->getValue()), $token->getLine());

            }

            $targets[] = new Twig_Node_Expression_AssignName($token->getValue(), $token->getLine());

            if (!$this->parser->getStream()->test(Twig_Token::PUNCTUATION_TYPE, ',')) {

                break;

            }

            $this->parser->getStream()->next();

        }

        return new Twig_Node($targets);

    }

    public function parseMultitargetExpression()

    {

        $targets = array();

        while (true) {

            $targets[] = $this->parseExpression();

            if (!$this->parser->getStream()->test(Twig_Token::PUNCTUATION_TYPE, ',')) {

                break;

            }

            $this->parser->getStream()->next();

        }

        return new Twig_Node($targets);

    }

}