lessc.inc.php

<?php

/**
 * lessphp v0.3.4-2
 * http://leafo.net/lessphp
 *
 * LESS css compiler, adapted from http://lesscss.org
 *
 * Copyright 2012, Leaf Corcoran <leafot@gmail.com>
 * Licensed under MIT or GPLv3, see LICENSE
 */


/**
 * The less compiler and parser.
 *
 * Converting LESS to CSS is a two stage process. First the incoming document
 * must be parsed. Parsing creates a tree in memory that represents the 
 * structure of the document. Then, the tree of the document is recursively
 * compiled into the CSS text. The compile step has an implicit step called
 * reduction, where values are brought to their lowest form before being
 * turned to text, eg. mathematical equations are solved, and variables are
 * dereferenced.
 *
 * The parsing stage produces the final structure of the document, for this
 * reason mixins are mixed in and attribute accessors are referenced during
 * the parse step. A reduction is done on the mixed in block as it is mixed in.
 *
 *  See the following:
 *    - entry point for parsing and compiling: lessc::parse()
 *    - parsing: lessc::parseChunk()
 *    - compiling: lessc::compileBlock()
 *
 */
class lessc {
	public static $VERSION = "v0.3.4-2";
	protected $buffer;
	protected $count;
	protected $line;
	protected $libFunctions = array();
	static protected $nextBlockId = 0;

	static protected $TRUE = array("keyword", "true");
	static protected $FALSE = array("keyword", "false");

	public $indentLevel;
	public $indentChar = '  ';

	protected $env = null;

	protected $allParsedFiles = array();

	public $vPrefix = '@'; // prefix of abstract properties
	public $mPrefix = '$'; // prefix of abstract blocks
	public $imPrefix = '!'; // special character to add !important
	public $parentSelector = '&';

	// set to the parser that generated the current line when compiling
	// so we know how to create error messages
	protected $sourceParser = null;

	static protected $precedence = array(
		'=<' => 0,
		'>=' => 0,
		'=' => 0,
		'<' => 0,
		'>' => 0,

		'+' => 1,
		'-' => 1,
		'*' => 2,
		'/' => 2,
		'%' => 2,
	);
	static protected $operatorString; // regex string to match any of the operators

	// types that have delayed computation
	static protected $dtypes = array('expression', 'variable',
		'function', 'negative', 'list', 'lookup');

	// these properties will supress division unless it's inside parenthases
	static protected $supressDivisionProps = array('/border-radius$/i', '/^font$/i');

	/**
	 * @link http://www.w3.org/TR/css3-values/
	 */
	static protected $units = array(
		'em', 'ex', 'px', 'gd', 'rem', 'vw', 'vh', 'vm', 'ch', // Relative length units
		'in', 'cm', 'mm', 'pt', 'pc', // Absolute length units
		'%', // Percentages
		'deg', 'grad', 'rad', 'turn', // Angles
		'ms', 's', // Times
		'Hz', 'kHz', //Frequencies
	);
    
	public $importDisabled = false;
	public $importDir = '';

	public $compat = false; // lessjs compatibility mode, does nothing right now

	/**
	 * if we are in an expression then we don't need to worry about parsing font shorthand
	 * $inExp becomes true after the first value in an expression, or if we enter parens
	 */
	protected $inExp = false;

	/**
	 * if we are in parens we can be more liberal with whitespace around operators because 
	 * it must evaluate to a single value and thus is less ambiguous.
	 *
	 * Consider:
	 *     property1: 10 -5; // is two numbers, 10 and -5
	 *     property2: (10 -5); // should evaluate to 5
	 */
	protected $inParens = false;

	/**
	 * Parse a single chunk off the head of the buffer and place it.
	 * @return false when the buffer is empty, or when there is an error.
	 *
	 * This function is called repeatedly until the entire document is
	 * parsed.
	 *
	 * This parser is most similar to a recursive descent parser. Single
	 * functions represent discrete grammatical rules for the language, and
	 * they are able to capture the text that represents those rules.
	 *
	 * Consider the function lessc::keyword(). (all parse functions are
	 * structured the same)
	 *
	 * The function takes a single reference argument. When calling the
	 * function it will attempt to match a keyword on the head of the buffer.
	 * If it is successful, it will place the keyword in the referenced
	 * argument, advance the position in the buffer, and return true. If it
	 * fails then it won't advance the buffer and it will return false.
	 *
	 * All of these parse functions are powered by lessc::match(), which behaves
	 * the same way, but takes a literal regular expression. Sometimes it is
	 * more convenient to use match instead of creating a new function.
	 *
	 * Because of the format of the functions, to parse an entire string of
	 * grammatical rules, you can chain them together using &&.
	 *
	 * But, if some of the rules in the chain succeed before one fails, then
	 * the buffer position will be left at an invalid state. In order to 
	 * avoid this, lessc::seek() is used to remember and set buffer positions.
	 *
	 * Before parsing a chain, use $s = $this->seek() to remember the current
	 * position into $s. Then if a chain fails, use $this->seek($s) to 
	 * go back where we started.
	 */
	function parseChunk() {
		if (empty($this->buffer)) return false;
		$s = $this->seek();
		
		// setting a property
		if ($this->keyword($key) && $this->assign() &&
			$this->propertyValue($value, $key) && $this->end())
		{
			$this->append(array('assign', $key, $value), $s);
			return true;
		} else {
			$this->seek($s);
		}

		// look for special css blocks
		if ($this->env->parent == null && $this->literal('@', false)) {
			$this->count--;

			// a font-face block
			if ($this->literal('@font-face') && $this->literal('{')) {
				$b = $this->pushSpecialBlock('@font-face');
				return true;
			} else {
				$this->seek($s);
			}

			// charset
			if ($this->literal('@charset') && $this->propertyValue($value) &&
				$this->end())
			{
				$this->append(array('charset', $value), $s);
				return true;
			} else {
				$this->seek($s);
			}


			// media
			if ($this->literal('@media') && $this->mediaTypes($types) &&
				$this->literal('{'))
			{
				$b = $this->pushSpecialBlock('@media');
				$b->media = $types;
				return true;
			} else {
				$this->seek($s);
			}

			// css animations
			if ($this->match('(@(-[a-z]+-)?keyframes)', $m) &&
				$this->propertyValue($value) && $this->literal('{'))
			{
				$b = $this->pushSpecialBlock(trim($m[0]));
				$b->keyframes = $value;
				return true;
			} else {
				$this->seek($s);
			}
		}

		if (isset($this->env->keyframes)) {
			if ($this->match("(to|from|[0-9]+%)", $m) && $this->literal('{')) {
				$this->pushSpecialBlock($m[1]);
				return true;
			} else {
				$this->seek($s);
			}
		}

		// setting a variable
		if ($this->variable($var) && $this->assign() &&
			$this->propertyValue($value) && $this->end())
		{
			$this->append(array('assign', $var, $value), $s);
			return true;
		} else {
			$this->seek($s);
		}

		if ($this->import($url, $media)) {
			// don't check .css files
			if (empty($media) && substr_compare($url, '.css', -4, 4) !== 0) {
				if ($this->importDisabled) {
					$this->append(array('raw', '/* import disabled */'));
				} else {
					$path = $this->findImport($url);
					if (!is_null($path)) {
						$this->append(array('import', $path), $s);
						return true;
					}
				}
			}

			$this->append(array('raw', '@import url("'.$url.'")'.
				($media ? ' '.$media : '').';'), $s);
			return true;
		}

		// opening parametric mixin
		if ($this->tag($tag, true) && $this->argumentDef($args, $is_vararg) &&
			($this->guards($guards) || true) &&
			$this->literal('{'))
		{
			$block = $this->pushBlock($this->fixTags(array($tag)));
			$block->args = $args;
			$block->is_vararg = $is_vararg;
			if (!empty($guards)) $block->guards = $guards;
			return true;
		} else {
			$this->seek($s);
		}

		// opening a simple block
		if ($this->tags($tags) && $this->literal('{')) {
			$tags = $this->fixTags($tags);
			$this->pushBlock($tags);
			return true;
		} else {
			$this->seek($s);
		}

		// closing a block
		if ($this->literal('}')) {
			try {
				$block = $this->pop();
			} catch (exception $e) {
				$this->seek($s);
				$this->throwError($e->getMessage());
			}

			$hidden = true;
			if (!isset($block->args)) foreach ($block->tags as $tag) {
				if (!is_string($tag) || $tag{0} != $this->mPrefix) {
					$hidden = false;
					break;
				}
			}

			if (!$hidden) $this->append(array('block', $block), $s);

			foreach ($block->tags as $tag) {
				if (is_string($tag)) {
					$this->env->children[$tag][] = $block;
				}
			}

			return true;
		}

		// mixin
		if ($this->mixinTags($tags) &&
			($this->argumentValues($argv) || true) && $this->end())
		{
			$tags = $this->fixTags($tags);
			$this->append(array('mixin', $tags, $argv), $s);
			return true;
		} else {
			$this->seek($s);
		}

		// spare ;
		if ($this->literal(';')) return true;

		return false; // got nothing, throw error
	}

	function fixTags($tags) {
		// move @ tags out of variable namespace
		foreach ($tags as &$tag) {
			if ($tag{0} == $this->vPrefix) $tag[0] = $this->mPrefix;
		}
		return $tags;
	}

	// attempts to find the path of an import url, returns null for css files
	function findImport($url) {
		foreach ((array)$this->importDir as $dir) {
			$full = $dir.(substr($dir, -1) != '/' ? '/' : '').$url;
			if ($this->fileExists($file = $full.'.less') || $this->fileExists($file = $full)) {
				return $file;
			}
		}

		return null;
	}

	function fileExists($name) {
		// sym link workaround
		return file_exists($name) || file_exists(realpath(preg_replace('/\w+\/\.\.\//', '', $name)));
	}

	// a list of expressions
	function expressionList(&$exps) {
		$values = array();	

		while ($this->expression($exp)) {
			$values[] = $exp;
		}
		
		if (count($values) == 0) return false;

		$exps = $this->compressList($values, ' ');
		return true;
	}

	/**
	 * Attempt to consume an expression.
	 * @link http://en.wikipedia.org/wiki/Operator-precedence_parser#Pseudo-code
	 */
	function expression(&$out) {
		$s = $this->seek();
		if ($this->literal('(') && ($this->inExp = $this->inParens = true) && $this->expression($exp) && $this->literal(')')) {
			$lhs = $exp;
		} elseif ($this->seek($s) && $this->value($val)) {
			$lhs = $val;
		} else {
			$this->inParens = $this->inExp = false;
			$this->seek($s);
			return false;
		}

		$out = $this->expHelper($lhs, 0);
		$this->inParens = $this->inExp = false;
		return true;
	}

	/**
	 * recursively parse infix equation with $lhs at precedence $minP
	 */
	function expHelper($lhs, $minP) {
		$this->inExp = true;
		$ss = $this->seek();

		// if there was whitespace before the operator, then we require whitespace after
		// the operator for it to be a mathematical operator.

		$needWhite = false;
		if (!$this->inParens && preg_match('/\s/', $this->buffer{$this->count - 1})) {
			$needWhite = true;
		}

		// try to find a valid operator
		while ($this->match(self::$operatorString.($needWhite ? '\s' : ''), $m) && self::$precedence[$m[1]] >= $minP) {
			if (!$this->inParens && isset($this->env->currentProperty) && $m[1] == "/") {
				foreach (self::$supressDivisionProps as $pattern) {
					if (preg_match($pattern, $this->env->currentProperty)) {
						$this->env->supressedDivision = true;
						break 2;
					}
				}
			}

			// get rhs
			$s = $this->seek();
			$p = $this->inParens;
			if ($this->literal('(') && ($this->inParens = true) && $this->expression($exp) && $this->literal(')')) {
				$this->inParens = $p;
				$rhs = $exp;
			} else {
				$this->inParens = $p;
				if ($this->seek($s) && $this->value($val)) {
					$rhs = $val;
				} else {
					break;
				}
			}

			// peek for next operator to see what to do with rhs
			if ($this->peek(self::$operatorString, $next) && self::$precedence[$next[1]] > self::$precedence[$m[1]]) {
				$rhs = $this->expHelper($rhs, self::$precedence[$next[1]]);
			}

			// don't evaluate yet if it is dynamic
			if (in_array($rhs[0], self::$dtypes) || in_array($lhs[0], self::$dtypes))
				$lhs = array('expression', $m[1], $lhs, $rhs);
			else
				$lhs = $this->evaluate($m[1], $lhs, $rhs);

			$ss = $this->seek();

			$needWhite = false;
			if (!$this->inParens && preg_match('/\s/', $this->buffer{$this->count - 1})) {
				$needWhite = true;
			}
		}
		$this->seek($ss);

		return $lhs;
	}

	// consume a list of values for a property
	function propertyValue(&$value, $keyName=null) {
		$values = array();	

		if (!is_null($keyName)) $this->env->currentProperty = $keyName;
		
		$s = null;
		while ($this->expressionList($v)) {
			$values[] = $v;
			$s = $this->seek();
			if (!$this->literal(',')) break;
		}

		if ($s) $this->seek($s);

		if (!is_null($keyName)) unset($this->env->currentProperty);

		if (count($values) == 0) return false;

		$value = $this->compressList($values, ', ');
		return true;
	}

	// a single value
	function value(&$value) {
		// try a unit
		if ($this->unit($value)) return true;	

		// see if there is a negation
		$s = $this->seek();
		if ($this->literal('-', false)) {
			$value = null;
			if ($this->variable($var)) {
				$value = array('variable', $var);
			} elseif ($this->buffer{$this->count} == "(" && $this->expression($exp)) {
				$value = $exp;
			} else {
				$this->seek($s);
			}

			if (!is_null($value)) {
				$value = array('negative', $value);
				return true;
			}
		} else {
			$this->seek($s);
		}

		// accessor 
		// must be done before color
		// this needs negation too
		if ($this->accessor($a)) {
			$a[1] = $this->fixTags($a[1]);
			$value = $a;
			return true;
		}
		
		// color
		if ($this->color($value)) return true;

		// css function
		// must be done after color
		if ($this->func($value)) return true;

		// string
		if ($this->string($tmp, $d)) {
			$value = array('string', $d.$tmp.$d);
			return true;
		}

		// try a keyword
		if ($this->keyword($word)) {
			$value = array('keyword', $word);
			return true;
		}

		// try a variable
		if ($this->variable($var)) {
			$value = array('variable', $var);
			return true;
		}

		// unquote string
		if ($this->literal("~") && $this->string($value, $d)) {
			$value = array("escape", $value);
			return true;
		} else {
			$this->seek($s);
		}

		// css hack: \0
		if ($this->literal('\\') && $this->match('([0-9]+)', $m)) {
			$value = array('keyword', '\\'.$m[1]);
			return true;
		} else {
			$this->seek($s);
		}

		// the spare / when supressing division
		if (!empty($this->env->supressedDivision)) {
			unset($this->env->supressedDivision);
			if ($this->literal("/")) {
				$value = array('keyword', '/');
				return true;
			}
		}

		return false;
	}

	// an import statement
	function import(&$url, &$media) {
		$s = $this->seek();
		if (!$this->literal('@import')) return false;

		// @import "something.css" media;
		// @import url("something.css") media;
		// @import url(something.css) media; 

		if ($this->literal('url(')) $parens = true; else $parens = false;

		if (!$this->string($url)) {
			if ($parens && $this->to(')', $url)) {
				$parens = false; // got em
			} else {
				$this->seek($s);
				return false;
			}
		}

		if ($parens && !$this->literal(')')) {
			$this->seek($s);
			return false;
		}

		// now the rest is media
		return $this->to(';', $media, false, true);
	}

	// a list of media types, very lenient
	function mediaTypes(&$parts) {
		$parts = array();
		while ($this->to("(", $chunk, false, "[^{]")) {
			$parts[] = array('raw', $chunk."(");
			$s = $this->seek();
			if ($this->keyword($name) && $this->assign() &&
				$this->propertyValue($value))
			{
				$parts[] = array('assign', $name, $value);
			} else {
				$this->seek($s);
			}
		}

		if ($this->to('{', $rest, true, true)) {
			$parts[] = array('raw', $rest);
			return true;
		}

		$parts = null;
		return false;
	}

	// a scoped value accessor
	// .hello > @scope1 > @scope2['value'];
	function accessor(&$var) {
		$s = $this->seek();

		if (!$this->tags($scope, true, '>') || !$this->literal('[')) {
			$this->seek($s);
			return false;
		}

		// either it is a variable or a property
		// why is a property wrapped in quotes, who knows!
		if ($this->variable($name)) {
			// ~
		} elseif ($this->literal("'") && $this->keyword($name) && $this->literal("'")) {
			// .. $this->count is messed up if we wanted to test another access type
		} else {
			$this->seek($s);
			return false;
		}

		if (!$this->literal(']')) {
			$this->seek($s);
			return false;
		}

		$var = array('lookup', $scope, $name);
		return true;
	}

	// a string 
	function string(&$string, &$d = null) {
		$s = $this->seek();
		if ($this->literal('"', false)) {
			$delim = '"';
		} elseif ($this->literal("'", false)) {
			$delim = "'";
		} else {
			return false;
		}

		if (!$this->to($delim, $string)) {
			$this->seek($s);
			return false;
		}
		
		$d = $delim;
		return true;
	}

	/**
	 * Consume a number and optionally a unit.
	 * Can also consume a font shorthand if it is a simple case.
	 * $allowed restricts the types that are matched.
	 */
	function unit(&$unit, $allowed = null) {
		if (!$allowed) $allowed = self::$units;

		if ($this->match('(-?[0-9]*(\.)?[0-9]+)('.implode('|', $allowed).')?', $m)) {
			if (!isset($m[3])) $m[3] = 'number';
			$unit = array($m[3], $m[1]);

			return true;
		}

		return false;
	}

	// a # color
	function color(&$out) {
		$color = array('color');

		if ($this->match('(#([0-9a-f]{6})|#([0-9a-f]{3}))', $m)) {
			if (isset($m[3])) {
				$num = $m[3];
				$width = 16;
			} else {
				$num = $m[2];
				$width = 256;
			}

			$num = hexdec($num);
			foreach (array(3,2,1) as $i) {
				$t = $num % $width;
				$num /= $width;

				$color[$i] = $t * (256/$width) + $t * floor(16/$width);
			}
			
			$out = $color;
			return true;
		} 

		return false;
	}

	// consume a list of property values delimited by ; and wrapped in ()
	function argumentValues(&$args, $delim = ',') {
		$s = $this->seek();
		if (!$this->literal('(')) return false;

		$values = array();
		while (true) {
			if ($this->expressionList($value)) $values[] = $value;
			if (!$this->literal($delim)) break;
			else {
				if ($value == null) $values[] = null;
				$value = null;
			}
		}	

		if (!$this->literal(')')) {
			$this->seek($s);
			return false;
		}
		
		$args = $values;
		return true;
	}

	// consume an argument definition list surrounded by ()
	// each argument is a variable name with optional value
	// or at the end a ... or a variable named followed by ...
	function argumentDef(&$args, &$is_vararg, $delim = ',') {
		$s = $this->seek();
		if (!$this->literal('(')) return false;

		$values = array();

		$is_vararg = false;
		while (true) {
			if ($this->literal("...")) {
				$is_vararg = true;
				break;
			}

			if ($this->variable($vname)) {
				$arg = array("arg", $vname);
				$ss = $this->seek();
				if ($this->assign() && $this->expressionList($value)) {
					$arg[] = $value;
				} else {
					$this->seek($ss);
					if ($this->literal("...")) {
						$arg[0] = "rest";
						$is_vararg = true;
					}
				}
				$values[] = $arg;
				if ($is_vararg) break;
				continue;
			}

			if ($this->value($literal)) {
				$values[] = array("lit", $literal);
			}

			if (!$this->literal($delim)) break;
		}

		if (!$this->literal(')')) {
			$this->seek($s);
			return false;
		}

		$args = $values;

		return true;
	}

	// consume a list of tags
	// this accepts a hanging delimiter
	function tags(&$tags, $simple = false, $delim = ',') {
		$tags = array();
		while ($this->tag($tt, $simple)) {
			$tags[] = $tt;
			if (!$this->literal($delim)) break;
		}
		if (count($tags) == 0) return false;

		return true;
	}

	// list of tags of specifying mixin path
	// optionally separated by > (lazy, accepts extra >)
	function mixinTags(&$tags) {
		$s = $this->seek();
		$tags = array();
		while ($this->tag($tt, true)) {
			$tags[] = $tt;
			$this->literal(">");
		}

		if (count($tags) == 0) return false;

		return true;
	}

	// a bracketed value (contained within in a tag definition)
	function tagBracket(&$value) {
		$s = $this->seek();
		if ($this->literal('[') && $this->to(']', $c, true) && $this->literal(']', false)) {
			$value = '['.$c.']';
			// whitespace?
			if ($this->match('', $_)) $value .= $_[0];

			// escape parent selector
			$value = str_replace($this->parentSelector, "&&", $value);
			return true;
		}

		$this->seek($s);
		return false;
	}

	function tagExpression(&$value) {
		$s = $this->seek();
		if ($this->literal("(") && $this->expression($exp) && $this->literal(")")) {
			$value = array('exp', $exp);
			return true;
		}

		$this->seek($s);
		return false;
	}

	// a single tag
	function tag(&$tag, $simple = false) {
		if ($simple)
			$chars = '^,:;{}\][>\(\) "\'';
		else
			$chars = '^,;{}["\'';

		if (!$simple && $this->tagExpression($tag)) {
			return true;
		}

		$tag = '';
		while ($this->tagBracket($first)) $tag .= $first;
		while ($this->match('(['.$chars.'0-9]['.$chars.']*)', $m)) {
			$tag .= $m[1];
			if ($simple) break;

			while ($this->tagBracket($brack)) $tag .= $brack;
		}
		$tag = trim($tag);
		if ($tag == '') return false;

		return true;
	}

	// a css function
	function func(&$func) {
		$s = $this->seek();

		if ($this->match('(%|[\w\-_][\w\-_:\.]+|[\w_])', $m) && $this->literal('(')) {
			$fname = $m[1];

			$s_pre_args = $this->seek();

			$args = array();
			while (true) {
				$ss = $this->seek();
				// this ugly nonsense is for ie filter properties
				if ($this->keyword($name) && $this->literal('=') && $this->expressionList($value)) {
					$args[] = array('list', '=', array(array('keyword', $name), $value));
				} else {
					$this->seek($ss);
					if ($this->expressionList($value)) {
						$args[] = $value;
					}
				}

				if (!$this->literal(',')) break;
			}
			$args = array('list', ',', $args);

			if ($this->literal(')')) {
				$func = array('function', $fname, $args);
				return true;
			} elseif ($fname == 'url') {
				// couldn't parse and in url? treat as string
				$this->seek($s_pre_args);
				if ($this->to(')', $content, true) && $this->literal(')')) {
					$func = array('function', $fname,array('string', $content));
					return true;
				}
			}
		}

		$this->seek($s);
		return false;
	}

	// consume a less variable
	function variable(&$name) {
		$s = $this->seek();
		if ($this->literal($this->vPrefix, false) &&
			($this->variable($sub) || $this->keyword($name)))
		{
			if (!empty($sub)) {
				$name = array('variable', $sub);
			} else {
				$name = $this->vPrefix.$name;
			}
			return true;	
		}

		$name = null;
		$this->seek($s);
		return false;
	}

	/**
	 * Consume an assignment operator
	 * Can optionally take a name that will be set to the current property name
	 */
	function assign($name = null) {
		if ($name) $this->currentProperty = $name;
		return $this->literal(':') || $this->literal('=');
	}

	// consume a keyword
	function keyword(&$word) {
		if ($this->match('([\w_\-\*!"][\w\-_"]*)', $m)) {
			$word = $m[1];
			return true;
		}
		return false;
	}

	// consume an end of statement delimiter
	function end() {
		if ($this->literal(';'))
			return true;
		elseif ($this->count == strlen($this->buffer) || $this->buffer{$this->count} == '}') {
			// if there is end of file or a closing block next then we don't need a ;
			return true;
		}
		return false;
	}

	function guards(&$guards) {
		$s = $this->seek();

		if (!$this->literal("when")) {
			$this->seek($s);
			return false;
		}

		$guards = array();

		while ($this->guard_group($g)) {
			$guards[] = $g;
			if (!$this->literal(",")) break;
		}

		if (count($guards) == 0) {
			$guards = null;
			$this->seek($s);
			return false;
		}

		return true;
	}

	// a bunch of guards that are and'd together
	function guard_group(&$guard_group) {
		$s = $this->seek();
		$guard_group = array();
		while ($this->guard($guard)) {
			$guard_group[] = $guard;
			if (!$this->literal("and")) break;
		}

		if (count($guard_group) == 0) {
			$guard_group = null;
			$this->seek($s);
			return false;
		}

		return true;
	}

	function guard(&$guard) {
		$s = $this->seek();
		$negate = $this->literal("not");

		if ($this->literal("(") && $this->expression($exp) && $this->literal(")")) {
			$guard = $exp;
			if ($negate) $guard = array("negate", $guard);
			return true;
		}

		$this->seek($s);
		return false;
	}

	function compressList($items, $delim) {
		if (count($items) == 1) return $items[0];	
		else return array('list', $delim, $items);
	}

	// just do a shallow property merge, seems to be what lessjs does
	function mergeBlock($target, $from) {
		$target = clone $target;
		$target->props = array_merge($target->props, $from->props);
		return $target;
	}

	// import all imports into the block
	function mixImports($block) {
		$props = array();
		foreach ($block->props as $prop) {
			if ($prop[0] == 'import') {
				list(, $path) = $prop;
				$this->addParsedFile($path);
				$child_less = $this->createChild($path);
				$root = $child_less->parseTree();

				$root->parent = $block;
				$this->mixImports($root);

				// inject imported blocks into this block, local will overwrite import
				$block->children = array_merge($root->children, $block->children);

				// splice in all the props
				foreach ($root->props as $sub_prop) {
					if (isset($sub_prop[-1])) {
						// leave a reference to the imported file for error messages
						$sub_prop[-1] = array($child_less, $sub_prop[-1]);
					}
					$props[] = $sub_prop;
				}
			} else {
				$props[] = $prop;
			}
		}
		$block->props = $props;
	}

	/**
	 * Recursively compiles a block. 
	 * @param $block the block
	 * @param $parentTags the tags of the block that contained this one
	 *
	 * A block is analogous to a CSS block in most cases. A single less document
	 * is encapsulated in a block when parsed, but it does not have parent tags
	 * so all of it's children appear on the root level when compiled.
	 *
	 * Blocks are made up of props and children.
	 *
	 * Props are property instructions, array tuples which describe an action
	 * to be taken, eg. write a property, set a variable, mixin a block.
	 *
	 * The children of a block are just all the blocks that are defined within.
	 *
	 * Compiling the block involves pushing a fresh environment on the stack,
	 * and iterating through the props, compiling each one.
	 *
	 * See lessc::compileProp()
	 *
	 */
	function compileBlock($block, $parent_tags = null) {
		$isRoot = $parent_tags == null && $block->tags == null;

		$indent = str_repeat($this->indentChar, $this->indentLevel);

		if (!empty($block->no_multiply)) {
			$special_block = true;
			$this->indentLevel++;
			$tags = array();
		} else {
			$special_block = false;

			// evaluate expression tags
			$tags = null;
			if (is_array($block->tags)) {
				$tags = array();
				foreach ($block->tags as $tag) {
					if (is_array($tag)) {
						list(, $value) = $tag;
						$tags[] = $this->compileValue($this->reduce($value));
					} else {
						$tags[] = $tag;
					}
				}
			}

			$tags = $this->multiplyTags($parent_tags, $tags);
		}

		$env = $this->pushEnv();
		$env->nameDepth = array();

		$lines = array();
		$blocks = array();
		$this->mixImports($block);
		foreach ($block->props as $prop) {
			$this->compileProp($prop, $block, $tags, $lines, $blocks);
		}

		$block->scope = $env;

		$this->pop();

		$nl = $isRoot ? "\n".$indent :
			"\n".$indent.$this->indentChar;

		ob_start();

		if ($special_block) {
			$this->indentLevel--;
			if (isset($block->media)) {
				echo $this->compileMedia($block);
			} elseif (isset($block->keyframes)) {
				echo $block->tags[0]." ".
					$this->compileValue($this->reduce($block->keyframes));
			} else {
				list($name) = $block->tags;
				echo $indent.$name;
			}

			echo ' {'.(count($lines) > 0 ? $nl : "\n");
		}

		// dump it
		if (count($lines) > 0) {
			if (!$special_block && !$isRoot) {
				echo $indent.implode(", ", $tags);
				if (count($lines) > 1) echo " {".$nl;
				else echo " { ";
			}

			echo implode($nl, $lines);

			if (!$special_block && !$isRoot) {
				if (count($lines) > 1) echo "\n".$indent."}\n";
				else echo " }\n";
			} else echo "\n";
		}

		foreach ($blocks as $b) echo $b;

		if ($special_block) {
			echo $indent."}\n";
		}

		return ob_get_clean();
	}

	// find the fully qualified tags for a block and its parent's tags
	function multiplyTags($parents, $current) {
		if ($parents == null) return $current;

		$tags = array();
		foreach ($parents as $ptag) {
			foreach ($current as $tag) {
				// inject parent in place of parent selector, ignoring escaped values
				$count = 0;
				$parts = explode("&&", $tag);

				foreach ($parts as $i => $chunk) {
					$parts[$i] = str_replace($this->parentSelector, $ptag, $chunk, $c);
					$count += $c;
				}
				
				$tag = implode("&", $parts);

				if ($count > 0) {
					$tags[] = trim($tag);
				} else {
					$tags[] = trim($ptag . ' ' . $tag);
				}
			}
		}

		return $tags;
	}

	function eq($left, $right) {
		return $left == $right;
	}

	function patternMatch($block, $callingArgs) {
		// match the guards if it has them
		// any one of the groups must have all its guards pass for a match
		if (!empty($block->guards)) {
			$group_passed = false;
			foreach ($block->guards as $guard_group) {
				foreach ($guard_group as $guard) {
					$this->pushEnv();
					$this->zipSetArgs($block->args, $callingArgs);

					$negate = false;
					if ($guard[0] == "negate") {
						$guard = $guard[1];
						$negate = true;
					}

					$passed = $this->reduce($guard) == self::$TRUE;
					if ($negate) $passed = !$passed;

					$this->pop();

					if ($passed) {
						$group_passed = true;
					} else {
						$group_passed = false;
						break;
					}
				}

				if ($group_passed) break;
			}

			if (!$group_passed) {
				return false;
			}
		}

		$numCalling = count($callingArgs);

		if (empty($block->args)) {
			return $block->is_vararg || $numCalling == 0;
		}

		$i = -1; // no args
		// try to match by arity or by argument literal
		foreach ($block->args as $i => $arg) {
			switch ($arg[0]) {
			case "lit":
				if (empty($callingArgs[$i]) || !$this->eq($arg[1], $callingArgs[$i])) {
					return false;
				}
				break;
			case "arg":
				// no arg and no default value
				if (!isset($callingArgs[$i]) && !isset($arg[2])) {
					return false;
				}
				break;
			case "rest":
				$i--; // rest can be empty
				break 2;
			}
		}

		if ($block->is_vararg) {
			return true; // not having enough is handled above
		} else {
			$numMatched = $i + 1;
			// greater than becuase default values always match
			return $numMatched >= $numCalling;
		}
	}

	function patternMatchAll($blocks, $callingArgs) {
		$matches = null;
		foreach ($blocks as $block) {
			if ($this->patternMatch($block, $callingArgs)) {
				$matches[] = $block;
			}
		}

		return $matches;
	}

	// attempt to find blocks matched by path and args
	function findBlocks($search_in, $path, $args, $seen=array()) {
		if ($search_in == null) return null;
		if (isset($seen[$search_in->id])) return null;
		$seen[$search_in->id] = true;

		$name = $path[0];

		if (isset($search_in->children[$name])) {
			$blocks = $search_in->children[$name];
			if (count($path) == 1) {
				$matches = $this->patternMatchAll($blocks, $args);
				if (!empty($matches)) {
					// This will return all blocks that match in the closest 
					// scope that has any matching block, like lessjs
					return $matches;
				}
			} else {
				return $this->findBlocks($blocks[0],
					array_slice($path, 1), $args, $seen);
			}
		}

		if ($search_in->parent === $search_in) return null;
		return $this->findBlocks($search_in->parent, $path, $args, $seen);
	}

	// sets all argument names in $args to either the default value
	// or the one passed in through $values
	function zipSetArgs($args, $values) {
		$i = 0;
		$assigned_values = array();
		foreach ($args as $a) {
			if ($a[0] == "arg") {
				if ($i < count($values) && !is_null($values[$i])) {
					$value = $values[$i];
				} elseif (isset($a[2])) {
					$value = $a[2];
				} else $value = null;

				$value = $this->reduce($value);
				$this->set($a[1], $value);
				$assigned_values[] = $value;
			}
			$i++;
		}

		// check for a rest
		$last = end($args);
		if ($last[0] == "rest") {
			$rest = array_slice($values, count($args) - 1);
			$this->set($last[1], $this->reduce(array("list", " ", $rest)));
		}

		$this->env->arguments = $assigned_values;
	}

	// compile a prop and update $lines or $blocks appropriately
	function compileProp($prop, $block, $tags, &$_lines, &$_blocks) {
		// set error position context
		if (isset($prop[-1])) {
			if (is_array($prop[-1])) {
				list($less, $count) = $prop[-1];
				$parentParser = $this->sourceParser;
				$this->sourceParser = $less;
				$this->count = $count;
			} else {
				$this->count = $prop[-1];
			}
		} else {
			$this->count = -1;
		}

		switch ($prop[0]) {
		case 'assign':
			list(, $name, $value) = $prop;
			if ($name[0] == $this->vPrefix) {
				$this->set($name, $value);
			} else {
				$_lines[] = "$name:".
					$this->compileValue($this->reduce($value)).";";
			}
			break;
		case 'block':
			list(, $child) = $prop;
			$_blocks[] = $this->compileBlock($child, $tags);
			break;
		case 'mixin':
			list(, $path, $args) = $prop;

			$args = array_map(array($this, "reduce"), (array)$args);
			$mixins = $this->findBlocks($block, $path, $args);
			if (is_null($mixins)) {
				// echo "failed to find block: ".implode(" > ", $path)."\n";
				break; // throw error here??
			}

			foreach ($mixins as $mixin) {
				$old_scope = null;
				if (isset($mixin->parent->scope)) {
					$old_scope = $this->env;
					$this->env = $mixin->parent->scope;
				}

				$have_args = false;
				if (isset($mixin->args)) {
					$have_args = true;
					$this->pushEnv();
					$this->zipSetArgs($mixin->args, $args);
				}

				$old_parent = $mixin->parent;
				if ($mixin != $block) $mixin->parent = $block;

				foreach ($mixin->props as $sub_prop) {
					$this->compileProp($sub_prop, $mixin, $tags, $_lines, $_blocks);
				}

				$mixin->parent = $old_parent;

				if ($have_args) $this->pop();

				if ($old_scope) {
					$this->env = $old_scope;
				}
			}

			break;
		case 'raw':
			$_lines[] = $prop[1];
			break;
		case 'charset':
			list(, $value) = $prop;
			$_lines[] = '@charset '.$this->compileValue($this->reduce($value)).';';
			break;
		default:
			$this->throwError("unknown op: {$prop[0]}\n");
		}

		if (isset($parentParser)) {
			$this->sourceParser = $parentParser;
		}
	}


	/**
	 * Compiles a primitive value into a CSS property value.
	 *
	 * Values in lessphp are typed by being wrapped in arrays, their format is
	 * typically:
	 *
	 *     array(type, contents [, additional_contents]*)
	 *
	 * Will not work on non reduced values (expressions, variables, etc)
	 */
	function compileValue($value) {
		switch ($value[0]) {
		case 'list':
			// [1] - delimiter
			// [2] - array of values
			return implode($value[1], array_map(array($this, 'compileValue'), $value[2]));
		case 'keyword':
			// [1] - the keyword 
		case 'number':
			// [1] - the number 
			return $value[1];
		case 'escape':
		case 'string':
			// [1] - contents of string (includes quotes)
			
			// search for inline variables to replace
			$replace = array();
			if (preg_match_all('/'.$this->preg_quote($this->vPrefix).'\{([\w-_][0-9\w-_]*)\}/', $value[1], $m)) {
				foreach ($m[1] as $name) {
					if (!isset($replace[$name]))
						$replace[$name] = $this->compileValue($this->reduce(array('variable', $this->vPrefix . $name)));
				}
			}

			foreach ($replace as $var=>$val) {
				if ($this->quoted($val)) {
					$val = substr($val, 1, -1);
				}
				$value[1] = str_replace($this->vPrefix. '{'.$var.'}', $val, $value[1]);
			}

			return $value[1];
		case 'color':
			// [1] - red component (either number for a %)
			// [2] - green component
			// [3] - blue component
			// [4] - optional alpha component
			list(, $r, $g, $b) = $value;
			$r = round($r);
			$g = round($g);
			$b = round($b);

			if (count($value) == 5 && $value[4] != 1) { // rgba
				return 'rgba('.$r.','.$g.','.$b.','.$value[4].')';
			}
			return sprintf("#%02x%02x%02x", $r, $g, $b);
		case 'function':
			// [1] - function name
			// [2] - some array value representing arguments, either ['string', value] or ['list', ',', values[]]

			// see if function evaluates to something else
			$value = $this->reduce($value);
			if ($value[0] == 'function') {
				return $value[1].'('.$this->compileValue($value[2]).')';
			}
			else return $this->compileValue($value);
		default: // assumed to be unit	
			return $value[1].$value[0];
		}
	}

	function compileMedia($block) {
		$mediaParts = array();
		foreach ($block->media as $part) {
			if ($part[0] == "raw") {
				$mediaParts[] = $part[1];
			} elseif ($part[0] == "assign") {
				list(, $propName, $propVal) = $part;
				$mediaParts[] = "$propName: ".
					$this->compileValue($this->reduce($propVal));
			}
		}

		return "@media ".trim(implode($mediaParts));
	}

	function lib_isnumber($value) {
		return $this->toBool(is_numeric($value[1]));
	}

	function lib_isstring($value) {
		return $this->toBool($value[0] == "string");
	}

	function lib_iscolor($value) {
		return $this->toBool($this->coerceColor($value));
	}

	function lib_iskeyword($value) {
		return $this->toBool($value[0] == "keyword");
	}

	function lib_ispixel($value) {
		return $this->toBool($value[0] == "px");
	}

	function lib_ispercentage($value) {
		return $this->toBool($value[0] == "%");
	}

	function lib_isem($value) {
		return $this->toBool($value[0] == "em");
	}

	function lib_rgbahex($color) {
		$color = $this->coerceColor($color);
		if (is_null($color))
			$this->throwError("color expected for rgbahex");

		return sprintf("#%02x%02x%02x%02x",
			isset($color[4]) ? $color[4]*255 : 0,
			$color[1],$color[2], $color[3]);
	}
	
	function lib_argb($color){
            return $this->lib_rgbahex($color);
        }

	// utility func to unquote a string
	function lib_e($arg) {
		switch ($arg[0]) {
			case "list":
				$items = $arg[2];
				if (isset($items[0])) {
					return $this->lib_e($items[0]);
				}
				return "";
			case "string":
				$str = $this->compileValue($arg);
				return substr($str, 1, -1);
			default:
				return $this->compileValue($arg);
		}
	}

	function lib__sprintf($args) {
		if ($args[0] != "list") return $args;
		$values = $args[2];
		$source = $this->reduce(array_shift($values));
		if ($source[0] != "string") {
			return $source;
		}

		$str = $source[1];
		$i = 0;
		if (preg_match_all('/%[dsa]/', $str, $m)) {
			foreach ($m[0] as $match) {
				$val = isset($values[$i]) ? $this->reduce($values[$i]) : array('keyword', '');
				$i++;
				switch ($match[1]) {
				case "s":
					if ($val[0] == "string") {
						$rep = substr($val[1], 1, -1);
						break;
					}
				default:
					$rep = $this->compileValue($val);
				}
				$str = preg_replace('/'.$this->preg_quote($match).'/', $rep, $str, 1);
			}
		}

		return array('string', $str);
	}

	function lib_floor($arg) {
		return array($arg[0], floor($arg[1]));
	}
	
	function lib_ceil($arg) {
		return array($arg[0], ceil($arg[1]));
	}

	function lib_round($arg) {
		return array($arg[0], round($arg[1]));
	}

	// is a string surrounded in quotes? returns the quoting char if true
	function quoted($s) {
		if (preg_match('/^("|\').*?\1$/', $s, $m))
			return $m[1];
		else return false;
	}

	/**
	 * Helper function to get arguments for color functions.
	 * Accepts invalid input, non colors interpreted as being black.
	 */
	function colorArgs($args) {
		if ($args[0] != 'list' || count($args[2]) < 2) {
			return array(array('color', 0, 0, 0));
		}
		list($color, $delta) = $args[2];
		$color = $this->coerceColor($color);
		if (is_null($color))
			$color = array('color', 0, 0, 0);

		$delta = floatval($delta[1]);

		return array($color, $delta);
	}

	function lib_darken($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[3] = $this->clamp($hsl[3] - $delta, 100);
		return $this->toRGB($hsl);
	}

	function lib_lighten($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[3] = $this->clamp($hsl[3] + $delta, 100);
		return $this->toRGB($hsl);
	}

	function lib_saturate($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[2] = $this->clamp($hsl[2] + $delta, 100);
		return $this->toRGB($hsl);
	}

	function lib_desaturate($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);
		$hsl[2] = $this->clamp($hsl[2] - $delta, 100);
		return $this->toRGB($hsl);
	}

	function lib_spin($args) {
		list($color, $delta) = $this->colorArgs($args);

		$hsl = $this->toHSL($color);

		$hsl[1] = $hsl[1] + $delta % 360;
		if ($hsl[1] < 0) $hsl[1] += 360;

		return $this->toRGB($hsl);
	}

	function lib_fadeout($args) {
		list($color, $delta) = $this->colorArgs($args);
		$color[4] = $this->clamp((isset($color[4]) ? $color[4] : 1) - $delta/100);
		return $color;
	}

	function lib_fadein($args) {
		list($color, $delta) = $this->colorArgs($args);
		$color[4] = $this->clamp((isset($color[4]) ? $color[4] : 1) + $delta/100);
		return $color;
	}

	function lib_hue($color) {
		if ($color[0] != 'color') return 0;
		$hsl = $this->toHSL($color);
		return round($hsl[1]);
	}

	function lib_saturation($color) {
		if ($color[0] != 'color') return 0;
		$hsl = $this->toHSL($color);
		return round($hsl[2]);
	}

	function lib_lightness($color) {
		if ($color[0] != 'color') return 0;
		$hsl = $this->toHSL($color);
		return round($hsl[3]);
	}

	// get the alpha of a color
	// defaults to 1 for non-colors or colors without an alpha
	function lib_alpha($color) {
		if ($color[0] != 'color') return 1;
		return isset($color[4]) ? $color[4] : 1;
	}

	// set the alpha of the color
	function lib_fade($args) {
		list($color, $alpha) = $this->colorArgs($args);
		$color[4] = $this->clamp($alpha / 100.0);
		return $color;
	}

	function lib_percentage($number) {
		return array('%', $number[1]*100);
	}

	// mixes two colors by weight
	// mix(@color1, @color2, @weight);
	// http://sass-lang.com/docs/yardoc/Sass/Script/Functions.html#mix-instance_method
	function lib_mix($args) {
		if ($args[0] != "list" || count($args[2]) < 3)
			$this->throwError("mix expects (color1, color2, weight)");

		list($first, $second, $weight) = $args[2];
		$first = $this->assertColor($first);
		$second = $this->assertColor($second);

		$first_a = $this->lib_alpha($first);
		$second_a = $this->lib_alpha($second);
		$weight = $weight[1] / 100.0;

		$w = $weight * 2 - 1;
		$a = $first_a - $second_a;

		$w1 = (($w * $a == -1 ? $w : ($w + $a)/(1 + $w * $a)) + 1) / 2.0;
		$w2 = 1.0 - $w1;

		$new = array('color',
			$w1 * $first[1] + $w2 * $second[1],
			$w1 * $first[2] + $w2 * $second[2],
			$w1 * $first[3] + $w2 * $second[3],
		);

		if ($first_a != 1.0 || $second_a != 1.0) {
			$new[] = $first_a * $weight + $second_a * ($weight - 1);
		}

		return $this->fixColor($new);
	}

	function assertColor($value, $error = "expected color value") {
		$color = $this->coerceColor($value);
		if (is_null($color)) $this->throwError($error);
		return $color;
	}

	function toHSL($color) {
		if ($color[0] == 'hsl') return $color;

		$r = $color[1] / 255;
		$g = $color[2] / 255;
		$b = $color[3] / 255;

		$min = min($r, $g, $b);
		$max = max($r, $g, $b);

		$L = ($min + $max) / 2;
		if ($min == $max) {
			$S = $H = 0;
		} else {
			if ($L < 0.5)
				$S = ($max - $min)/($max + $min);
			else
				$S = ($max - $min)/(2.0 - $max - $min);

			if ($r == $max) $H = ($g - $b)/($max - $min);
			elseif ($g == $max) $H = 2.0 + ($b - $r)/($max - $min);
			elseif ($b == $max) $H = 4.0 + ($r - $g)/($max - $min);

		}

		$out = array('hsl',
			($H < 0 ? $H + 6 : $H)*60,
			$S*100,
			$L*100,
		);

		if (count($color) > 4) $out[] = $color[4]; // copy alpha
		return $out;
	}

	function toRGB_helper($comp, $temp1, $temp2) {
		if ($comp < 0) $comp += 1.0;
		elseif ($comp > 1) $comp -= 1.0;

		if (6 * $comp < 1) return $temp1 + ($temp2 - $temp1) * 6 * $comp;
		if (2 * $comp < 1) return $temp2;
		if (3 * $comp < 2) return $temp1 + ($temp2 - $temp1)*((2/3) - $comp) * 6;

		return $temp1;
	}

	/**
	 * Converts a hsl array into a color value in rgb.
	 * Expects H to be in range of 0 to 360, S and L in 0 to 100
	 */
	function toRGB($color) {
		if ($color == 'color') return $color;

		$H = $color[1] / 360;
		$S = $color[2] / 100;
		$L = $color[3] / 100;

		if ($S == 0) {
			$r = $g = $b = $L;
		} else {
			$temp2 = $L < 0.5 ?
				$L*(1.0 + $S) :
				$L + $S - $L * $S;

			$temp1 = 2.0 * $L - $temp2;

			$r = $this->toRGB_helper($H + 1/3, $temp1, $temp2);
			$g = $this->toRGB_helper($H, $temp1, $temp2);
			$b = $this->toRGB_helper($H - 1/3, $temp1, $temp2);
		}

		// $out = array('color', round($r*255), round($g*255), round($b*255));
		$out = array('color', $r*255, $g*255, $b*255);
		if (count($color) > 4) $out[] = $color[4]; // copy alpha
		return $out;
	}

	function clamp($v, $max = 1, $min = 0) {
		return min($max, max($min, $v));
	}

	/**
	 * Convert the rgb, rgba, hsl color literals of function type
	 * as returned by the parser into values of color type.
	 */
	function funcToColor($func) {
		$fname = $func[1];
		if ($func[2][0] != 'list') return false; // need a list of arguments
		$rawComponents = $func[2][2];

		if ($fname == 'hsl' || $fname == 'hsla') {
			$hsl = array('hsl');
			$i = 0;
			foreach ($rawComponents as $c) {
				$val = $this->reduce($c);
				$val = isset($val[1]) ? floatval($val[1]) : 0;

				if ($i == 0) $clamp = 360;
				elseif ($i < 4) $clamp = 100;
				else $clamp = 1;

				$hsl[] = $this->clamp($val, $clamp);
				$i++;
			}

			while (count($hsl) < 4) $hsl[] = 0;
			return $this->toRGB($hsl);

		} elseif ($fname == 'rgb' || $fname == 'rgba') {
			$components = array();
			$i = 1;
			foreach	($rawComponents as $c) {
				$c = $this->reduce($c);
				if ($i < 4) {
					if ($c[0] == '%') $components[] = 255 * ($c[1] / 100);
					else $components[] = floatval($c[1]); 
				} elseif ($i == 4) {
					if ($c[0] == '%') $components[] = 1.0 * ($c[1] / 100);
					else $components[] = floatval($c[1]);
				} else break;

				$i++;
			}
			while (count($components) < 3) $components[] = 0;
			array_unshift($components, 'color');
			return $this->fixColor($components);
		}

		return false;
	}

	function toName($val) {
		switch($val[0]) {
		case "string":
			return substr($val[1], 1, -1);
		default:
			return $val[1];
		}
	}

	// reduce a delayed type to its final value
	// dereference variables and solve equations
	function reduce($var) {
		// this is done here for infinite loop checking
		if ($var[0] == "variable") {
			$key = is_array($var[1]) ?
				$this->vPrefix.$this->toName($this->reduce($var[1])) : $var[1];

			$seen =& $this->env->seenNames;

			if (!empty($seen[$key])) {
				$this->throwError("infinite loop detected: $key");
			}

			$seen[$key] = true;

			$out = $this->reduce($this->get($key));

			$seen[$key] = false;

			return $out;
		}

		while (in_array($var[0], self::$dtypes)) {
			if ($var[0] == 'list') {
				foreach ($var[2] as &$value) $value = $this->reduce($value);
				break;
			} elseif ($var[0] == 'expression') {
				$var = $this->evaluate($var[1], $var[2], $var[3]);
			} elseif ($var[0] == 'lookup') {
				// do accessor here....
				$var = array('number', 0);
			} elseif ($var[0] == 'function') {
				$color = $this->funcToColor($var);
				if ($color) $var = $color;
				else {
					list($_, $name, $args) = $var;
					if ($name == "%") $name = "_sprintf";
					$f = isset($this->libFunctions[$name]) ?
						$this->libFunctions[$name] : array($this, 'lib_'.$name);

					if (is_callable($f)) {
						if ($args[0] == 'list')
							$args = $this->compressList($args[2], $args[1]);

						$var = call_user_func($f, $this->reduce($args), $this);

						// convert to a typed value if the result is a php primitive
						if (is_numeric($var)) $var = array('number', $var);
						elseif (!is_array($var)) $var = array('keyword', $var);
					} else {
						// plain function, reduce args
						$var[2] = $this->reduce($var[2]);
					}
				}
				break; // done reducing after a function
			} elseif ($var[0] == 'negative') {
				$value = $this->reduce($var[1]);
				if (is_numeric($value[1])) {
					$value[1] = -1*$value[1];
				} 
				$var = $value;
			}
		}

		return $var;
	}

	function coerceColor($value) {
		switch($value[0]) {
			case 'color': return $value;
			case 'keyword':
				$name = $value[1];
				if (isset(self::$cssColors[$name])) {
					list($r, $g, $b) = explode(',', self::$cssColors[$name]);
					return array('color', $r, $g, $b);
				}
				return null;
		}
	}

	function toBool($a) {
		if ($a) return self::$TRUE;
		else return self::$FALSE;
	}

	// evaluate an expression
	function evaluate($op, $left, $right) {
		$left = $this->reduce($left);
		$right = $this->reduce($right);

		if ($left_color = $this->coerceColor($left)) {
			$left = $left_color;
		}

		if ($right_color = $this->coerceColor($right)) {
			$right = $right_color;
		}

		if ($op == "and") {
			return $this->toBool($left == self::$TRUE && $right == self::$TRUE);
		}

		if ($op == "=") {
			return $this->toBool($this->eq($left, $right) );
		}

		if ($left[0] == 'color' && $right[0] == 'color') {
			$out = $this->op_color_color($op, $left, $right);
			return $out;
		}

		if ($left[0] == 'color') {
			return $this->op_color_number($op, $left, $right);
		}

		if ($right[0] == 'color') {
			return $this->op_number_color($op, $left, $right);
		}

		// concatenate strings
		if ($op == '+' && $left[0] == 'string') {
			$append = $this->compileValue($right);
			if ($this->quoted($append)) $append = substr($append, 1, -1);

			$lhs = $this->compileValue($left);
			if ($q = $this->quoted($lhs)) $lhs = substr($lhs, 1, -1);
			if (!$q) $q = '';

			return array('string', $q.$lhs.$append.$q);
		}

		if ($left[0] == 'keyword' || $right[0] == 'keyword' ||
			$left[0] == 'string' || $right[0] == 'string')
		{
			// look for negative op
			if ($op == '-') $right[1] = '-'.$right[1];
			return array('keyword', $this->compileValue($left) .' '. $this->compileValue($right));
		}
	
		// default to number operation
		return $this->op_number_number($op, $left, $right);
	}

	// make sure a color's components don't go out of bounds
	function fixColor($c) {
		foreach (range(1, 3) as $i) {
			if ($c[$i] < 0) $c[$i] = 0;
			if ($c[$i] > 255) $c[$i] = 255;
		}

		return $c;
	}

	function op_number_color($op, $lft, $rgt) {
		if ($op == '+' || $op = '*') {
			return $this->op_color_number($op, $rgt, $lft);
		}
	}

	function op_color_number($op, $lft, $rgt) {
		if ($rgt[0] == '%') $rgt[1] /= 100;

		return $this->op_color_color($op, $lft,
			array_fill(1, count($lft) - 1, $rgt[1]));
	}

	function op_color_color($op, $left, $right) {
		$out = array('color');
		$max = count($left) > count($right) ? count($left) : count($right);
		foreach (range(1, $max - 1) as $i) {
			$lval = isset($left[$i]) ? $left[$i] : 0;
			$rval = isset($right[$i]) ? $right[$i] : 0;
			switch ($op) {
			case '+':
				$out[] = $lval + $rval;
				break;
			case '-':
				$out[] = $lval - $rval;
				break;
			case '*':
				$out[] = $lval * $rval;
				break;
			case '%':
				$out[] = $lval % $rval;
				break;
			case '/':
				if ($rval == 0) $this->throwError("evaluate error: can't divide by zero");
				$out[] = $lval / $rval;
				break;
			default:
				$this->throwError('evaluate error: color op number failed on op '.$op);
			}
		}
		return $this->fixColor($out);
	}

	// operator on two numbers
	function op_number_number($op, $left, $right) {
		$type = is_null($left) ? "number" : $left[0];
		if ($type == "number") $type = $right[0];

		$value = 0;
		switch ($op) {
		case '+':
			$value = $left[1] + $right[1];
			break;	
		case '*':
			$value = $left[1] * $right[1];
			break;	
		case '-':
			$value = $left[1] - $right[1];
			break;	
		case '%':
			$value = $left[1] % $right[1];
			break;	
		case '/':
			if ($right[1] == 0) $this->throwError('parse error: divide by zero');
			$value = $left[1] / $right[1];
			break;
		case '<':
			return $this->toBool($left[1] < $right[1]);
		case '>':
			return $this->toBool($left[1] > $right[1]);
		case '>=':
			return $this->toBool($left[1] >= $right[1]);
		case '=<':
			return $this->toBool($left[1] <= $right[1]);
		default:
			$this->throwError('parse error: unknown number operator: '.$op);
		}

		return array($type, $value);
	}


	/* environment functions */

	// push a new block on the stack, used for parsing
	function pushBlock($tags) {
		$b = new stdclass;
		$b->parent = $this->env;

		$b->id = self::$nextBlockId++;
		$b->is_vararg = false;
		$b->tags = $tags;
		$b->props = array();
		$b->children = array();

		$this->env = $b;
		return $b;
	}
	
	// push a block that doesn't multiply tags
	function pushSpecialBlock($name) {
		$b = $this->pushBlock(array($name));
		$b->no_multiply = true;
		return $b;
	}

	// used for compiliation variable state
	function pushEnv() {
		$e = new stdclass;
		$e->parent = $this->env;

		$this->store = array();

		$this->env = $e;
		return $e;
	}

	// pop something off the stack
	function pop() {
		$old = $this->env;
		$this->env = $this->env->parent;
		return $old;
	}

	// set something in the current env
	function set($name, $value) {
		$this->env->store[$name] = $value;
	}

	// append an property
	function append($prop, $pos = null) {
		if (!is_null($pos)) $prop[-1] = $pos;
		$this->env->props[] = $prop;
	}

	// get the highest occurrence entry for a name
	function get($name) {
		$current = $this->env;

		$is_arguments = $name == $this->vPrefix . 'arguments';
		while ($current) {
			if ($is_arguments && isset($current->arguments)) {
				return array('list', ' ', $current->arguments);
			}

			if (isset($current->store[$name]))
				return $current->store[$name];
			else
				$current = $current->parent;
		}

		return null;
	}
	
	/* raw parsing functions */

	function literal($what, $eatWhitespace = true) {
		// this is here mainly prevent notice from { } string accessor 
		if ($this->count >= strlen($this->buffer)) return false;

		// shortcut on single letter
		if (!$eatWhitespace && strlen($what) == 1) {
			if ($this->buffer{$this->count} == $what) {
				$this->count++;
				return true;
			}
			else return false;
		}

		return $this->match($this->preg_quote($what), $m, $eatWhitespace);
	}

	function preg_quote($what) {
		return preg_quote($what, '/');
	}

	// advance counter to next occurrence of $what
	// $until - don't include $what in advance
	// $allowNewline, if string, will be used as valid char set
	function to($what, &$out, $until = false, $allowNewline = false) {
		if (is_string($allowNewline)) {
			$validChars = $allowNewline;
		} else {
			$validChars = $allowNewline ? "." : "[^\n]";
		}
		if (!$this->match('('.$validChars.'*?)'.$this->preg_quote($what), $m, !$until)) return false;
		if ($until) $this->count -= strlen($what); // give back $what
		$out = $m[1];
		return true;
	}
	
	// try to match something on head of buffer
	function match($regex, &$out, $eatWhitespace = true) {
		$r = '/'.$regex.($eatWhitespace ? '\s*' : '').'/Ais';
		if (preg_match($r, $this->buffer, $out, null, $this->count)) {
			$this->count += strlen($out[0]);
			return true;
		}
		return false;
	}

	// match something without consuming it
	function peek($regex, &$out = null) {
		$r = '/'.$regex.'/Ais';
		$result = preg_match($r, $this->buffer, $out, null, $this->count);
		
		return $result;
	}

	// seek to a spot in the buffer or return where we are on no argument
	function seek($where = null) {
		if ($where === null) return $this->count;
		else $this->count = $where;
		return true;
	}

	/**
	 * Initialize state for a fresh parse
	 */
	protected function prepareParser($buff) {
		$this->env = null;
		$this->expandStack = array();
		$this->indentLevel = 0;
		$this->count = 0;
		$this->line = 1;

		$this->buffer = $this->removeComments($buff);
		$this->pushBlock(null); // set up global scope

		// trim whitespace on head
		if (preg_match('/^\s+/', $this->buffer, $m)) {
			$this->line  += substr_count($m[0], "\n");
			$this->buffer = ltrim($this->buffer);
		}
	}

	// create a child parser (for compiling an import)
	protected function createChild($fname) {
		$less = new lessc($fname);
		$less->importDir = array_merge((array)$less->importDir, (array)$this->importDir);
		$less->indentChar = $this->indentChar;
		$less->compat = $this->compat;
		return $less;
	}

	// parse code and return intermediate tree
	public function parseTree($str = null) {
		$this->prepareParser(is_null($str) ? $this->buffer : $str);
		while (false !== $this->parseChunk());

		if ($this->count != strlen($this->buffer))
			$this->throwError();

		if (!is_null($this->env->parent))
			throw new exception('parse error: unclosed block');

		$root = $this->env;
		$this->env = null;
		return $root;
	}

	// inject array of unparsed strings into environment as variables
	protected function injectVariables($args) {
		$this->pushEnv();
		$parser = new lessc();
		foreach ($args as $name => $str_value) {
			if ($name{0} != '@') $name = '@'.$name;
			$parser->count = 0;
			$parser->buffer = (string)$str_value;
			if (!$parser->propertyValue($value)) {
				throw new Exception("failed to parse passed in variable $name: $str_value");
			}

			$this->set($name, $value);
		}
	}
	
	// parse and compile buffer
	function parse($str = null, $initial_variables = null) {
		$locale = setlocale(LC_NUMERIC, 0);
		setlocale(LC_NUMERIC, "C");
		$root = $this->parseTree($str);

		if ($initial_variables) $this->injectVariables($initial_variables);
		$out = $this->compileBlock($root);
		setlocale(LC_NUMERIC, $locale);
		return $out;
	}

	/**
	 * Uses the current value of $this->count to show line and line number
	 */
	function throwError($msg = 'parse error') {
		if (!empty($this->sourceParser)) {
			$this->sourceParser->count = $this->count;
			return $this->sourceParser->throwError($msg);
		} elseif ($this->count > 0) {
			$line = $this->line + substr_count(substr($this->buffer, 0, $this->count), "\n");
			if (isset($this->fileName)) {
				$loc = $this->fileName.' on line '.$line;
			} else {
				$loc = "line: ".$line;
			}

			if ($this->peek("(.*?)(\n|$)", $m))
				throw new exception($msg.': failed at `'.$m[1].'` '.$loc);
		}

		throw new exception($msg);
	}

	/**
	 * Initialize any static state, can initialize parser for a file
	 */
	function __construct($fname = null, $opts = null) {
		if (!self::$operatorString) {
			self::$operatorString = 
				'('.implode('|', array_map(array($this, 'preg_quote'),
					array_keys(self::$precedence))).')';
		}

		if ($fname) {
			if (!is_file($fname)) {
				throw new Exception('load error: failed to find '.$fname);
			}
			$pi = pathinfo($fname);

			$this->fileName = $fname;
			$this->importDir = $pi['dirname'].'/';
			$this->buffer = file_get_contents($fname);

			$this->addParsedFile($fname);
		}
	}

	public function registerFunction($name, $func) {
		$this->libFunctions[$name] = $func;
	}

	public function unregisterFunction($name) {
		unset($this->libFunctions[$name]);
	}

	// remove comments from $text
	// todo: make it work for all functions, not just url
	function removeComments($text) {
		$look = array(
			'url(', '//', '/*', '"', "'"
		);

		$out = '';
		$min = null;
		$done = false;
		while (true) {
			// find the next item
			foreach ($look as $token) {
				$pos = strpos($text, $token);
				if ($pos !== false) {
					if (!isset($min) || $pos < $min[1]) $min = array($token, $pos);
				}
			}

			if (is_null($min)) break;

			$count = $min[1];
			$skip = 0;
			$newlines = 0;
			switch ($min[0]) {
			case 'url(':
				if (preg_match('/url\(.*?\)/', $text, $m, 0, $count))
					$count += strlen($m[0]) - strlen($min[0]);
				break;
			case '"':
			case "'":
				if (preg_match('/'.$min[0].'.*?'.$min[0].'/', $text, $m, 0, $count))
					$count += strlen($m[0]) - 1;
				break;
			case '//':
				$skip = strpos($text, "\n", $count);
				if ($skip === false) $skip = strlen($text) - $count;
				else $skip -= $count;
				break;
			case '/*': 
				if (preg_match('/\/\*.*?\*\//s', $text, $m, 0, $count)) {
					$skip = strlen($m[0]);
					$newlines = substr_count($m[0], "\n");
				}
				break;
			}

			if ($skip == 0) $count += strlen($min[0]);

			$out .= substr($text, 0, $count).str_repeat("\n", $newlines);
			$text = substr($text, $count + $skip);

			$min = null;
		}

		return $out.$text;
	}

	public function allParsedFiles() { return $this->allParsedFiles; }
	protected function addParsedFile($file) {
		$this->allParsedFiles[realpath($file)] = filemtime($file);
	}


	// compile file $in to file $out if $in is newer than $out
	// returns true when it compiles, false otherwise
	public static function ccompile($in, $out) {
		if (!is_file($out) || filemtime($in) > filemtime($out)) {
			$less = new lessc($in);
			file_put_contents($out, $less->parse());
			return true;
		}

		return false;
	}

	/**
	 * Execute lessphp on a .less file or a lessphp cache structure
	 * 
	 * The lessphp cache structure contains information about a specific
	 * less file having been parsed. It can be used as a hint for future
	 * calls to determine whether or not a rebuild is required.
	 * 
	 * The cache structure contains two important keys that may be used
	 * externally:
	 * 
	 * compiled: The final compiled CSS
	 * updated: The time (in seconds) the CSS was last compiled
	 * 
	 * The cache structure is a plain-ol' PHP associative array and can
	 * be serialized and unserialized without a hitch.
	 * 
	 * @param mixed $in Input
	 * @param bool $force Force rebuild?
	 * @return array lessphp cache structure
	 */
	public static function cexecute($in, $force = false) {

		// assume no root
		$root = null;

		if (is_string($in)) {
			$root = $in;
		} elseif (is_array($in) and isset($in['root'])) {
			if ($force or ! isset($in['files'])) {
				// If we are forcing a recompile or if for some reason the
				// structure does not contain any file information we should
				// specify the root to trigger a rebuild.
				$root = $in['root'];
			} elseif (isset($in['files']) and is_array($in['files'])) {
				foreach ($in['files'] as $fname => $ftime ) {
					if (!file_exists($fname) or filemtime($fname) > $ftime) {
						// One of the files we knew about previously has changed
						// so we should look at our incoming root again.
						$root = $in['root'];
						break;
					}
				}
			}
		} else {
			// TODO: Throw an exception? We got neither a string nor something
			// that looks like a compatible lessphp cache structure.
			return null;
		}

		if ($root !== null) {
			// If we have a root value which means we should rebuild.
			$less = new lessc($root);
			$out = array();
			$out['root'] = $root;
			$out['compiled'] = $less->parse();
			$out['files'] = $less->allParsedFiles();
			$out['updated'] = time();
			return $out;
		} else {
			// No changes, pass back the structure
			// we were given initially.
			return $in;
		}

	}

	static protected $cssColors = array(
		'aliceblue' => '240,248,255',
		'antiquewhite' => '250,235,215',
		'aqua' => '0,255,255',
		'aquamarine' => '127,255,212',
		'azure' => '240,255,255',
		'beige' => '245,245,220',
		'bisque' => '255,228,196',
		'black' => '0,0,0',
		'blanchedalmond' => '255,235,205',
		'blue' => '0,0,255',
		'blueviolet' => '138,43,226',
		'brown' => '165,42,42',
		'burlywood' => '222,184,135',
		'cadetblue' => '95,158,160',
		'chartreuse' => '127,255,0',
		'chocolate' => '210,105,30',
		'coral' => '255,127,80',
		'cornflowerblue' => '100,149,237',
		'cornsilk' => '255,248,220',
		'crimson' => '220,20,60',
		'cyan' => '0,255,255',
		'darkblue' => '0,0,139',
		'darkcyan' => '0,139,139',
		'darkgoldenrod' => '184,134,11',
		'darkgray' => '169,169,169',
		'darkgreen' => '0,100,0',
		'darkgrey' => '169,169,169',
		'darkkhaki' => '189,183,107',
		'darkmagenta' => '139,0,139',
		'darkolivegreen' => '85,107,47',
		'darkorange' => '255,140,0',
		'darkorchid' => '153,50,204',
		'darkred' => '139,0,0',
		'darksalmon' => '233,150,122',
		'darkseagreen' => '143,188,143',
		'darkslateblue' => '72,61,139',
		'darkslategray' => '47,79,79',
		'darkslategrey' => '47,79,79',
		'darkturquoise' => '0,206,209',
		'darkviolet' => '148,0,211',
		'deeppink' => '255,20,147',
		'deepskyblue' => '0,191,255',
		'dimgray' => '105,105,105',
		'dimgrey' => '105,105,105',
		'dodgerblue' => '30,144,255',
		'firebrick' => '178,34,34',
		'floralwhite' => '255,250,240',
		'forestgreen' => '34,139,34',
		'fuchsia' => '255,0,255',
		'gainsboro' => '220,220,220',
		'ghostwhite' => '248,248,255',
		'gold' => '255,215,0',
		'goldenrod' => '218,165,32',
		'gray' => '128,128,128',
		'green' => '0,128,0',
		'greenyellow' => '173,255,47',
		'grey' => '128,128,128',
		'honeydew' => '240,255,240',
		'hotpink' => '255,105,180',
		'indianred' => '205,92,92',
		'indigo' => '75,0,130',
		'ivory' => '255,255,240',
		'khaki' => '240,230,140',
		'lavender' => '230,230,250',
		'lavenderblush' => '255,240,245',
		'lawngreen' => '124,252,0',
		'lemonchiffon' => '255,250,205',
		'lightblue' => '173,216,230',
		'lightcoral' => '240,128,128',
		'lightcyan' => '224,255,255',
		'lightgoldenrodyellow' => '250,250,210',
		'lightgray' => '211,211,211',
		'lightgreen' => '144,238,144',
		'lightgrey' => '211,211,211',
		'lightpink' => '255,182,193',
		'lightsalmon' => '255,160,122',
		'lightseagreen' => '32,178,170',
		'lightskyblue' => '135,206,250',
		'lightslategray' => '119,136,153',
		'lightslategrey' => '119,136,153',
		'lightsteelblue' => '176,196,222',
		'lightyellow' => '255,255,224',
		'lime' => '0,255,0',
		'limegreen' => '50,205,50',
		'linen' => '250,240,230',
		'magenta' => '255,0,255',
		'maroon' => '128,0,0',
		'mediumaquamarine' => '102,205,170',
		'mediumblue' => '0,0,205',
		'mediumorchid' => '186,85,211',
		'mediumpurple' => '147,112,219',
		'mediumseagreen' => '60,179,113',
		'mediumslateblue' => '123,104,238',
		'mediumspringgreen' => '0,250,154',
		'mediumturquoise' => '72,209,204',
		'mediumvioletred' => '199,21,133',
		'midnightblue' => '25,25,112',
		'mintcream' => '245,255,250',
		'mistyrose' => '255,228,225',
		'moccasin' => '255,228,181',
		'navajowhite' => '255,222,173',
		'navy' => '0,0,128',
		'oldlace' => '253,245,230',
		'olive' => '128,128,0',
		'olivedrab' => '107,142,35',
		'orange' => '255,165,0',
		'orangered' => '255,69,0',
		'orchid' => '218,112,214',
		'palegoldenrod' => '238,232,170',
		'palegreen' => '152,251,152',
		'paleturquoise' => '175,238,238',
		'palevioletred' => '219,112,147',
		'papayawhip' => '255,239,213',
		'peachpuff' => '255,218,185',
		'peru' => '205,133,63',
		'pink' => '255,192,203',
		'plum' => '221,160,221',
		'powderblue' => '176,224,230',
		'purple' => '128,0,128',
		'red' => '255,0,0',
		'rosybrown' => '188,143,143',
		'royalblue' => '65,105,225',
		'saddlebrown' => '139,69,19',
		'salmon' => '250,128,114',
		'sandybrown' => '244,164,96',
		'seagreen' => '46,139,87',
		'seashell' => '255,245,238',
		'sienna' => '160,82,45',
		'silver' => '192,192,192',
		'skyblue' => '135,206,235',
		'slateblue' => '106,90,205',
		'slategray' => '112,128,144',
		'slategrey' => '112,128,144',
		'snow' => '255,250,250',
		'springgreen' => '0,255,127',
		'steelblue' => '70,130,180',
		'tan' => '210,180,140',
		'teal' => '0,128,128',
		'thistle' => '216,191,216',
		'tomato' => '255,99,71',
		'turquoise' => '64,224,208',
		'violet' => '238,130,238',
		'wheat' => '245,222,179',
		'white' => '255,255,255',
		'whitesmoke' => '245,245,245',
		'yellow' => '255,255,0',
		'yellowgreen' => '154,205,50'
	);
}