<?php /* SVN FILE: $Id: SassScriptLexer.php 118 2010-09-21 09:45:11Z chris.l.yates@gmail.com $ */ /**

* SassScriptLexer class file.
* @author                      Chris Yates <chris.l.yates@gmail.com>
* @copyright   Copyright (c) 2010 PBM Web Development
* @license                     http://phamlp.googlecode.com/files/license.txt
* @package                     PHamlP
* @subpackage  Sass.script
*/

require_once('literals/SassBoolean.php'); require_once('literals/SassColour.php'); require_once('literals/SassNumber.php'); require_once('literals/SassString.php'); require_once('SassScriptFunction.php'); require_once('SassScriptOperation.php'); require_once('SassScriptVariable.php');

/**

* SassScriptLexer class.
* Lexes SassSCript into tokens for the parser.
* 
* Implements a {@link http://en.wikipedia.org/wiki/Shunting-yard_algorithm Shunting-yard algorithm} to provide {@link http://en.wikipedia.org/wiki/Reverse_Polish_notation Reverse Polish notation} output.
* @package                     PHamlP
* @subpackage  Sass.script
*/

class SassScriptLexer {

const MATCH_WHITESPACE = '/^\s+/';

/**
 * @var SassScriptParser the parser object
 */
private $parser;

/**
* SassScriptLexer constructor.
* @return SassScriptLexer
*/
public function __construct($parser) {
        $this->parser = $parser;
}

/**
 * Lex an expression into SassScript tokens.
 * @param string expression to lex
 * @param SassContext the context in which the expression is lexed
 * @return array tokens
 */
public function lex($string, $context) {
        $tokens = array();
        while ($string !== false) {
                if (($match = $this->isWhitespace($string)) !== false) {
                        $tokens[] = null;
                }
                elseif (($match = SassScriptFunction::isa($string)) !== false) {
                        preg_match(SassScriptFunction::MATCH_FUNC, $match, $matches);

                        $args = array();
                        foreach (SassScriptFunction::extractArgs($matches[SassScriptFunction::ARGS])
                                        as $expression) {
                                $args[] = $this->parser->evaluate($expression, $context);
                        }

                        $tokens[] = new SassScriptFunction(
                                        $matches[SassScriptFunction::NAME], $args);
                }
                elseif (($match = SassString::isa($string)) !== false) {
                        $tokens[] = new SassString($match);
                }
                elseif (($match = SassBoolean::isa($string)) !== false) {
                        $tokens[] = new SassBoolean($match);
                }
                elseif (($match = SassColour::isa($string)) !== false) {
                        $tokens[] = new SassColour($match);
                }
                elseif (($match = SassNumber::isa($string)) !== false) {                                
                        $tokens[] = new SassNumber($match);
                }
                elseif (($match = SassScriptOperation::isa($string)) !== false) {
                        $tokens[] = new SassScriptOperation($match);
                }
                elseif (($match = SassScriptVariable::isa($string)) !== false) {
                        $tokens[] = new SassScriptVariable($match);
                }
                else {
                        $_string = $string;
                        $match = '';
                        while (strlen($_string) && !$this->isWhitespace($_string)) {
                                foreach (SassScriptOperation::$inStrOperators as $operator) {
                                        if (substr($_string, 0, strlen($operator)) == $operator) {
                                                break 2;
                                        }
                                }
                                $match .= $_string[0];
                                $_string = substr($_string, 1);                 
                        }
                        $tokens[] = new SassString($match);
                }                       
                $string = substr($string, strlen($match));
        }
        return $tokens; 
}

/**
 * Returns a value indicating if a token of this type can be matched at
 * the start of the subject string.
 * @param string the subject string
 * @return mixed match at the start of the string or false if no match
 */
public function isWhitespace($subject) {
        return (preg_match(self::MATCH_WHITESPACE, $subject, $matches) ? $matches[0] : false);
}

}