ExpressionParser.php

<?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:
            if ('(' === $this->parser
              ->getCurrentToken()
              ->getValue()) {
              $node = $this
                ->getFunctionNode($token
                ->getValue(), $token
                ->getLine());
            }
            else {
              $node = new Twig_Node_Expression_Name($token
                ->getValue(), $token
                ->getLine());
            }
        }
        break;
      case Twig_Token::NUMBER_TYPE:
        $this->parser
          ->getStream()
          ->next();
        $node = new Twig_Node_Expression_Constant($token
          ->getValue(), $token
          ->getLine());
        break;
      case Twig_Token::STRING_TYPE:
      case Twig_Token::INTERPOLATION_START_TYPE:
        $node = $this
          ->parseStringExpression();
        break;
      default:
        if ($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 parseStringExpression() {
    $stream = $this->parser
      ->getStream();
    $nodes = array();

    // a string cannot be followed by another string in a single expression
    $nextCanBeString = true;
    while (true) {
      if ($stream
        ->test(Twig_Token::STRING_TYPE) && $nextCanBeString) {
        $token = $stream
          ->next();
        $nodes[] = new Twig_Node_Expression_Constant($token
          ->getValue(), $token
          ->getLine());
        $nextCanBeString = false;
      }
      elseif ($stream
        ->test(Twig_Token::INTERPOLATION_START_TYPE)) {
        $stream
          ->next();
        $nodes[] = $this
          ->parseExpression();
        $stream
          ->expect(Twig_Token::INTERPOLATION_END_TYPE);
        $nextCanBeString = true;
      }
      else {
        break;
      }
    }
    $expr = array_shift($nodes);
    foreach ($nodes as $node) {
      $expr = new Twig_Node_Expression_Binary_Concat($expr, $node, $node
        ->getLine());
    }
    return $expr;
  }
  public function parseArrayExpression() {
    $stream = $this->parser
      ->getStream();
    $stream
      ->expect(Twig_Token::PUNCTUATION_TYPE, '[', 'An array element was expected');
    $node = new Twig_Node_Expression_Array(array(), $stream
      ->getCurrent()
      ->getLine());
    $first = true;
    while (!$stream
      ->test(Twig_Token::PUNCTUATION_TYPE, ']')) {
      if (!$first) {
        $stream
          ->expect(Twig_Token::PUNCTUATION_TYPE, ',', 'An array element must be followed by a comma');

        // trailing ,?
        if ($stream
          ->test(Twig_Token::PUNCTUATION_TYPE, ']')) {
          break;
        }
      }
      $first = false;
      $node
        ->addElement($this
        ->parseExpression());
    }
    $stream
      ->expect(Twig_Token::PUNCTUATION_TYPE, ']', 'An opened array is not properly closed');
    return $node;
  }
  public function parseHashExpression() {
    $stream = $this->parser
      ->getStream();
    $stream
      ->expect(Twig_Token::PUNCTUATION_TYPE, '{', 'A hash element was expected');
    $node = new Twig_Node_Expression_Array(array(), $stream
      ->getCurrent()
      ->getLine());
    $first = true;
    while (!$stream
      ->test(Twig_Token::PUNCTUATION_TYPE, '}')) {
      if (!$first) {
        $stream
          ->expect(Twig_Token::PUNCTUATION_TYPE, ',', 'A hash value must be followed by a comma');

        // trailing ,?
        if ($stream
          ->test(Twig_Token::PUNCTUATION_TYPE, '}')) {
          break;
        }
      }
      $first = false;

      // a hash key can be:
      //
      //  * a number -- 12
      //  * a string -- 'a'
      //  * a name, which is equivalent to a string -- a
      //  * an expression, which must be enclosed in parentheses -- (1 + 2)
      if ($stream
        ->test(Twig_Token::STRING_TYPE) || $stream
        ->test(Twig_Token::NAME_TYPE) || $stream
        ->test(Twig_Token::NUMBER_TYPE)) {
        $token = $stream
          ->next();
        $key = new Twig_Node_Expression_Constant($token
          ->getValue(), $token
          ->getLine());
      }
      elseif ($stream
        ->test(Twig_Token::PUNCTUATION_TYPE, '(')) {
        $key = $this
          ->parseExpression();
      }
      else {
        $current = $stream
          ->getCurrent();
        throw new Twig_Error_Syntax(sprintf('A hash key must be a quoted string, a number, a name, or an expression enclosed in parentheses (unexpected token "%s" of value "%s"', Twig_Token::typeToEnglish($current
          ->getType(), $current
          ->getLine()), $current
          ->getValue()), $current
          ->getLine());
      }
      $stream
        ->expect(Twig_Token::PUNCTUATION_TYPE, ':', 'A hash key must be followed by a colon (:)');
      $value = $this
        ->parseExpression();
      $node
        ->addElement($value, $key);
    }
    $stream
      ->expect(Twig_Token::PUNCTUATION_TYPE, '}', 'An opened hash is not properly closed');
    return $node;
  }
  public function parsePostfixExpression($node) {
    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);
        }
        else {
          break;
        }
      }
      else {
        break;
      }
    }
    return $node;
  }
  public function getFunctionNode($name, $line) {
    $args = $this
      ->parseArguments();
    switch ($name) {
      case 'parent':
        if (!count($this->parser
          ->getBlockStack())) {
          throw new Twig_Error_Syntax('Calling "parent" outside a block is forbidden', $line);
        }
        if (!$this->parser
          ->getParent() && !$this->parser
          ->hasTraits()) {
          throw new Twig_Error_Syntax('Calling "parent" on a template that does not extend nor "use" another template is forbidden', $line);
        }
        return new Twig_Node_Expression_Parent($this->parser
          ->peekBlockStack(), $line);
      case 'block':
        return new Twig_Node_Expression_BlockReference($args
          ->getNode(0), false, $line);
      case 'attribute':
        if (count($args) < 2) {
          throw new Twig_Error_Syntax('The "attribute" function takes at least two arguments (the variable and the attributes)', $line);
        }
        return new Twig_Node_Expression_GetAttr($args
          ->getNode(0), $args
          ->getNode(1), count($args) > 2 ? $args
          ->getNode(2) : new Twig_Node_Expression_Array(array(), $line), Twig_TemplateInterface::ANY_CALL, $line);
      default:
        if (null !== ($alias = $this->parser
          ->getImportedFunction($name))) {
          $arguments = new Twig_Node_Expression_Array(array(), $line);
          foreach ($args as $n) {
            $arguments
              ->addElement($n);
          }
          $node = new Twig_Node_Expression_MethodCall($alias['node'], $alias['name'], $arguments, $line);
          $node
            ->setAttribute('safe', true);
          return $node;
        }
        $class = $this
          ->getFunctionNodeClass($name);
        return new $class($name, $args, $line);
    }
  }
  public function parseSubscriptExpression($node) {
    $stream = $this->parser
      ->getStream();
    $token = $stream
      ->next();
    $lineno = $token
      ->getLine();
    $arguments = new Twig_Node_Expression_Array(array(), $lineno);
    $type = Twig_TemplateInterface::ANY_CALL;
    if ($token
      ->getValue() == '.') {
      $token = $stream
        ->next();
      if ($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(), $lineno);
        if ($stream
          ->test(Twig_Token::PUNCTUATION_TYPE, '(')) {
          $type = Twig_TemplateInterface::METHOD_CALL;
          foreach ($this
            ->parseArguments() as $n) {
            $arguments
              ->addElement($n);
          }
        }
      }
      else {
        throw new Twig_Error_Syntax('Expected name or number', $lineno);
      }
    }
    else {
      $type = Twig_TemplateInterface::ARRAY_CALL;
      $arg = $this
        ->parseExpression();

      // slice?
      if ($stream
        ->test(Twig_Token::PUNCTUATION_TYPE, ':')) {
        $stream
          ->next();
        if ($stream
          ->test(Twig_Token::PUNCTUATION_TYPE, ']')) {
          $length = new Twig_Node_Expression_Constant(null, $token
            ->getLine());
        }
        else {
          $length = $this
            ->parseExpression();
        }
        $class = $this
          ->getFilterNodeClass('slice');
        $arguments = new Twig_Node(array(
          $arg,
          $length,
        ));
        $filter = new $class($node, new Twig_Node_Expression_Constant('slice', $token
          ->getLine()), $arguments, $token
          ->getLine());
        $stream
          ->expect(Twig_Token::PUNCTUATION_TYPE, ']');
        return $filter;
      }
      $stream
        ->expect(Twig_Token::PUNCTUATION_TYPE, ']');
    }
    return new Twig_Node_Expression_GetAttr($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();
      }
      $class = $this
        ->getFilterNodeClass($name
        ->getAttribute('value'));
      $node = new $class($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);
  }
  protected function getFunctionNodeClass($name) {
    $functionMap = $this->parser
      ->getEnvironment()
      ->getFunctions();
    if (isset($functionMap[$name]) && $functionMap[$name] instanceof Twig_Function_Node) {
      return $functionMap[$name]
        ->getClass();
    }
    return 'Twig_Node_Expression_Function';
  }
  protected function getFilterNodeClass($name) {
    $filterMap = $this->parser
      ->getEnvironment()
      ->getFilters();
    if (isset($filterMap[$name]) && $filterMap[$name] instanceof Twig_Filter_Node) {
      return $filterMap[$name]
        ->getClass();
    }
    return 'Twig_Node_Expression_Filter';
  }

}