symfony/src/Symfony/Components/CssSelector/Parser.php

<?php

namespace Symfony\Components\CssSelector;

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien.potencier@symfony-project.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * Parser is the main entry point of the component and can convert CSS
 * selectors to XPath expressions.
 *
 * $xpath = Parser::cssToXpath('h1.foo');
 *
 * This component is a port of the Python lxml library,
 * which is copyright Infrae and distributed under the BSD license.
 *
 * @package    Symfony
 * @subpackage Components_CssSelector
 * @author     Fabien Potencier <fabien.potencier@symfony-project.com>
 */
class Parser
{
  /**
   * @throws SyntaxError When got None for xpath expression
   */
  static public function cssToXpath($cssExpr, $prefix = 'descendant-or-self::')
  {
    if (is_string($cssExpr))
    {
      if (preg_match('#^\w+\s*$#u', $cssExpr, $match))
      {
        return $prefix.trim($match[0]);
      }

      if (preg_match('~^(\w*)#(\w+)\s*$~u', $cssExpr, $match))
      {
        return sprintf("%s%s[@id = '%s']", $prefix, $match[1] ? $match[1] : '*', $match[2]);
      }

      if (preg_match('#^(\w*)\.(\w+)\s*$#u', $cssExpr, $match))
      {
        return sprintf("%s%s[contains(concat(' ', normalize-space(@class), ' '), ' %s ')]", $prefix, $match[1] ? $match[1] : '*', $match[2]);
      }

      $parser = new self();
      $cssExpr = $parser->parse($cssExpr);
    }

    $expr = $cssExpr->toXpath();

    // @codeCoverageIgnoreStart
    if (!$expr)
    {
      throw new SyntaxError(sprintf('Got None for xpath expression from %s.', $cssExpr));
    }
    // @codeCoverageIgnoreEnd

    if ($prefix)
    {
      $expr->addPrefix($prefix);
    }

    return (string) $expr;
  }

  /**
   * @throws \Exception When tokenizer throws it while parsing
   */
  public function parse($string)
  {
    $tokenizer = new Tokenizer();

    $stream = new TokenStream($tokenizer->tokenize($string), $string);

    try
    {
      return $this->parseSelectorGroup($stream);
    }
    catch (\Exception $e)
    {
      $class = get_class($e);

      throw new $class(sprintf('%s at %s -> %s', $e->getMessage(), implode($stream->getUsed(), ''), $stream->peek()));
    }
  }

  protected function parseSelectorGroup($stream)
  {
    $result = array();
    while (1)
    {
      $result[] = $this->parseSelector($stream);
      if ($stream->peek() == ',')
      {
        $stream->next();
      }
      else
      {
        break;
      }
    }

    if (count($result) == 1)
    {
      return $result[0];
    }

    return new Node\OrNode($result);
  }

  /**
   * @throws SyntaxError When expected selector but got something else
   */
  protected function parseSelector($stream)
  {
    $result = $this->parseSimpleSelector($stream);

    while (1)
    {
      $peek = $stream->peek();
      if ($peek == ',' || $peek === null)
      {
        return $result;
      }
      elseif (in_array($peek, array('+', '>', '~')))
      {
        // A combinator
        $combinator = (string) $stream->next();
      }
      else
      {
        $combinator = ' ';
      }
      $consumed = count($stream->getUsed());
      $next_selector = $this->parseSimpleSelector($stream);
      if ($consumed == count($stream->getUsed()))
      {
        throw new SyntaxError(sprintf("Expected selector, got '%s'", $stream->peek()));
      }

      $result = new Node\CombinedSelectorNode($result, $combinator, $next_selector);
    }

    return $result;
  }

  /**
   * @throws SyntaxError When expected symbol but got something else
   */
  protected function parseSimpleSelector($stream)
  {
    $peek = $stream->peek();
    if ($peek != '*' && !$peek->isType('Symbol'))
    {
      $element = $namespace = '*';
    }
    else
    {
      $next = $stream->next();
      if ($next != '*' && !$next->isType('Symbol'))
      {
        throw new SyntaxError(sprintf("Expected symbol, got '%s'", $next));
      }

      if ($stream->peek() == '|')
      {
        $namespace = $next;
        $stream->next();
        $element = $stream->next();
        if ($element != '*' && !$next->isType('Symbol'))
        {
          throw new SyntaxError(sprintf("Expected symbol, got '%s'", $next));
        }
      }
      else
      {
        $namespace = '*';
        $element = $next;
      }
    }

    $result = new Node\ElementNode($namespace, $element);
    $has_hash = false;
    while (1)
    {
      $peek = $stream->peek();
      if ($peek == '#')
      {
        if ($has_hash)
        {
          /* You can't have two hashes
            (FIXME: is there some more general rule I'm missing?) */
          // @codeCoverageIgnoreStart
          break;
          // @codeCoverageIgnoreEnd
        }
        $stream->next();
        $result = new Node\HashNode($result, $stream->next());
        $has_hash = true;

        continue;
      }
      elseif ($peek == '.')
      {
        $stream->next();
        $result = new Node\ClassNode($result, $stream->next());

        continue;
      }
      elseif ($peek == '[')
      {
        $stream->next();
        $result = $this->parseAttrib($result, $stream);
        $next = $stream->next();
        if ($next != ']')
        {
          throw new SyntaxError(sprintf("] expected, got '%s'", $next));
        }

        continue;
      }
      elseif ($peek == ':' || $peek == '::')
      {
        $type = $stream->next();
        $ident = $stream->next();
        if (!$ident || !$ident->isType('Symbol'))
        {
          throw new SyntaxError(sprintf("Expected symbol, got '%s'", $ident));
        }

        if ($stream->peek() == '(')
        {
          $stream->next();
          $peek = $stream->peek();
          if ($peek->isType('String'))
          {
            $selector = $stream->next();
          }
          elseif ($peek->isType('Symbol') && is_int($peek))
          {
            $selector = intval($stream->next());
          }
          else
          {
            // FIXME: parseSimpleSelector, or selector, or...?
            $selector = $this->parseSimpleSelector($stream);
          }
          $next = $stream->next();
          if ($next != ')')
          {
            throw new SyntaxError(sprintf("Expected ')', got '%s' and '%s'", $next, $selector));
          }

          $result = new Node\FunctionNode($result, $type, $ident, $selector);
        }
        else
        {
          $result = new Node\PseudoNode($result, $type, $ident);
        }

        continue;
      }
      else
      {
        if ($peek == ' ')
        {
          $stream->next();
        }

        break;
      }
      // FIXME: not sure what "negation" is
    }

    return $result;
  }

  /**
   * @throws SyntaxError When encountered unexpected selector
   */
  protected function parseAttrib($selector, $stream)
  {
    $attrib = $stream->next();
    if ($stream->peek() == '|')
    {
      $namespace = $attrib;
      $stream->next();
      $attrib = $stream->next();
    }
    else
    {
      $namespace = '*';
    }

    if ($stream->peek() == ']')
    {
      return new Node\AttribNode($selector, $namespace, $attrib, 'exists', null);
    }

    $op = $stream->next();
    if (!in_array($op, array('^=', '$=', '*=', '=', '~=', '|=', '!=')))
    {
      throw new SyntaxError(sprintf("Operator expected, got '%s'", $op));
    }

    $value = $stream->next();
    if (!$value->isType('Symbol') && !$value->isType('String'))
    {
      throw new SyntaxError(sprintf("Expected string or symbol, got '%s'", $value));
    }

    return new Node\AttribNode($selector, $namespace, $attrib, $op, $value);
  }
}