xref: /plugin/mikioplugin/inc/stemmechanics/lesserphp/lessc.inc.php (revision 16f233320bea3cc69785d1b79bb43ffac559a4e3)

<?php

/**
 * lessphp v0.7.1
 * http://leafo.net/lessphp
 *
 * LESS CSS compiler, adapted from http://lesscss.org
 *
 * Copyright 2013, Leaf Corcoran <leafot@gmail.com>
 * Copyright 2016, Marcus Schwarz <github@maswaba.de>
 * Copyright 2024, James Collins <james@stemmechanics.com.au>
 * Licensed under MIT or GPLv3, see LICENSE
 */


/**
 * The LESS compiler and parser.
 *
 * Converting LESS to CSS is a three stage process. The incoming file is parsed
 * by `lessc_parser` into a syntax tree, then it is compiled into another tree
 * representing the CSS structure by `lessc`. The CSS tree is fed into a
 * formatter, like `lessc_formatter` which then outputs CSS as a string.
 *
 * During the first compile, all values are *reduced*, which means that their
 * types are brought to the lowest form before being dump as strings. This
 * handles math equations, variable dereferences, and the like.
 *
 * The `parse` function of `lessc` is the entry point.
 *
 * In summary:
 *
 * The `lessc` class creates an instance of the parser, feeds it LESS code,
 * then transforms the resulting tree to a CSS tree. This class also holds the
 * evaluation context, such as all available mixins and variables at any given
 * time.
 *
 * The `lessc_parser` class is only concerned with parsing its input.
 *
 * The `lessc_formatter` takes a CSS tree, and dumps it to a formatted string,
 * handling things like indentation.
 */
class lessc
{
	static public $VERSION = "v0.7.1";

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

	protected $libFunctions = array();
	protected $registeredVars = array();
	protected $preserveComments = false;

	public $vPrefix = '@'; // prefix of abstract properties
	public $mPrefix = '$'; // prefix of abstract blocks
	public $parentSelector = '&';

	static public $lengths = array("px", "m", "cm", "mm", "in", "pt", "pc");
	static public $times = array("s", "ms");
	static public $angles = array("rad", "deg", "grad", "turn");

	static public $lengths_to_base = array(1, 3779.52755906, 37.79527559, 3.77952756, 96, 1.33333333, 16);
	public $importDisabled = false;
	public $importDir = array();

	protected $numberPrecision = null;

	protected $allParsedFiles = array();

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

	static protected $nextImportId = 0; // uniquely identify imports

	protected $parser;
	protected $env;
	protected $scope;
	protected $formatter;

	// attempts to find the path of an import url, returns null for css files
	protected 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;
	}

	protected function fileExists($name)
	{
		return is_file($name);
	}

	static public function compressList($items, $delim)
	{
		if (!isset($items[1]) && isset($items[0])) return $items[0];
		else return array('list', $delim, $items);
	}

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

	protected function tryImport($importPath, $parentBlock, $out)
	{
		if ($importPath[0] == "function" && $importPath[1] == "url") {
			$importPath = $this->flattenList($importPath[2]);
		}

		$str = $this->coerceString($importPath);
		if ($str === null) return false;

		$url = $this->compileValue($this->lib_e($str));

		// don't import if it ends in css
		if (substr_compare($url, '.css', -4, 4) === 0) return false;

		$realPath = $this->findImport($url);

		if ($realPath === null) return false;

		if ($this->importDisabled) {
			return array(false, "/* import disabled */");
		}

		if (isset($this->allParsedFiles[realpath($realPath)])) {
			return array(false, null);
		}

		$this->addParsedFile($realPath);
		$parser = $this->makeParser($realPath);
		$root = $parser->parse(file_get_contents($realPath));

		// set the parents of all the block props
		foreach ($root->props as $prop) {
			if ($prop[0] == "block") {
				$prop[1]->parent = $parentBlock;
			}
		}

		// copy mixins into scope, set their parents
		// bring blocks from import into current block
		// TODO: need to mark the source parser	these came from this file
		foreach ($root->children as $childName => $child) {
			if (isset($parentBlock->children[$childName])) {
				$parentBlock->children[$childName] = array_merge(
					$parentBlock->children[$childName],
					$child
				);
			} else {
				$parentBlock->children[$childName] = $child;
			}
		}

		$pi = pathinfo($realPath);
		$dir = $pi["dirname"];

		[$top, $bottom] = $this->sortProps($root->props, true);
		$this->compileImportedProps($top, $parentBlock, $out, $parser, $dir);

		return array(true, $bottom, $parser, $dir);
	}

	protected function compileImportedProps($props, $block, $out, $sourceParser, $importDir)
	{
		$oldSourceParser = $this->sourceParser;

		$oldImport = $this->importDir;

		// TODO: this is because the importDir api is stupid
		$this->importDir = (array)$this->importDir;
		array_unshift($this->importDir, $importDir);

		foreach ($props as $prop) {
			$this->compileProp($prop, $block, $out);
		}

		$this->importDir = $oldImport;
		$this->sourceParser = $oldSourceParser;
	}

	/**
	 * Recursively compiles a block.
	 *
	 * 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.
	 * This is used to look up mixins when performing a mixin.
	 *
	 * Compiling the block involves pushing a fresh environment on the stack,
	 * and iterating through the props, compiling each one.
	 *
	 * See lessc::compileProp()
	 *
	 */
	protected function compileBlock($block)
	{
		switch ($block->type) {
			case "root":
				$this->compileRoot($block);
				break;
			case null:
				$this->compileCSSBlock($block);
				break;
			case "media":
				$this->compileMedia($block);
				break;
			case "directive":
				$name = "@" . $block->name;
				if (!empty($block->value)) {
					$name .= " " . $this->compileValue($this->reduce($block->value));
				}

				$this->compileNestedBlock($block, array($name));
				break;
			default:
				$block->parser->throwError("unknown block type: $block->type\n", $block->count);
		}
	}

	protected function compileCSSBlock($block)
	{
		$env = $this->pushEnv();

		$selectors = $this->compileSelectors($block->tags);
		$env->selectors = $this->multiplySelectors($selectors);
		$out = $this->makeOutputBlock(null, $env->selectors);

		$this->scope->children[] = $out;
		$this->compileProps($block, $out);

		$block->scope = $env; // mixins carry scope with them!
		$this->popEnv();
	}

	protected function compileMedia($media)
	{
		$env = $this->pushEnv($media);
		$parentScope = $this->mediaParent($this->scope);

		$query = $this->compileMediaQuery($this->multiplyMedia($env));

		$this->scope = $this->makeOutputBlock($media->type, array($query));
		$parentScope->children[] = $this->scope;

		$this->compileProps($media, $this->scope);

		if (count($this->scope->lines) > 0) {
			$orphanSelelectors = $this->findClosestSelectors();
			if (!is_null($orphanSelelectors)) {
				$orphan = $this->makeOutputBlock(null, $orphanSelelectors);
				$orphan->lines = $this->scope->lines;
				array_unshift($this->scope->children, $orphan);
				$this->scope->lines = array();
			}
		}

		$this->scope = $this->scope->parent;
		$this->popEnv();
	}

	protected function mediaParent($scope)
	{
		while (!empty($scope->parent)) {
			if (!empty($scope->type) && $scope->type != "media") {
				break;
			}
			$scope = $scope->parent;
		}

		return $scope;
	}

	protected function compileNestedBlock($block, $selectors)
	{
		$this->pushEnv($block);
		$this->scope = $this->makeOutputBlock($block->type, $selectors);
		$this->scope->parent->children[] = $this->scope;

		$this->compileProps($block, $this->scope);

		$this->scope = $this->scope->parent;
		$this->popEnv();
	}

	protected function compileRoot($root)
	{
		$this->pushEnv();
		$this->scope = $this->makeOutputBlock($root->type);
		$this->compileProps($root, $this->scope);
		$this->popEnv();
	}

	protected function compileProps($block, $out)
	{
		foreach ($this->sortProps($block->props) as $prop) {
			$this->compileProp($prop, $block, $out);
		}
		$out->lines = $this->deduplicate($out->lines);
	}

	/**
	 * Deduplicate lines in a block. Comments are not deduplicated. If a
	 * duplicate rule is detected, the comments immediately preceding each
	 * occurence are consolidated.
	 */
	protected function deduplicate($lines)
	{
		$unique = array();
		$comments = array();

		foreach ($lines as $line) {
			if (strpos($line, '/*') === 0) {
				$comments[] = $line;
				continue;
			}
			if (!in_array($line, $unique)) {
				$unique[] = $line;
			}
			array_splice($unique, array_search($line, $unique), 0, $comments);
			$comments = array();
		}
		return array_merge($unique, $comments);
	}

	protected function sortProps($props, $split = false)
	{
		$vars = array();
		$imports = array();
		$other = array();
		$stack = array();

		foreach ($props as $prop) {
			switch ($prop[0]) {
				case "comment":
					$stack[] = $prop;
					break;
				case "assign":
					$stack[] = $prop;
					if (isset($prop[1][0]) && $prop[1][0] == $this->vPrefix) {
						$vars = array_merge($vars, $stack);
					} else {
						$other = array_merge($other, $stack);
					}
					$stack = array();
					break;
				case "import":
					$id = self::$nextImportId++;
					$prop[] = $id;
					$stack[] = $prop;
					$imports = array_merge($imports, $stack);
					$other[] = array("import_mixin", $id);
					$stack = array();
					break;
				default:
					$stack[] = $prop;
					$other = array_merge($other, $stack);
					$stack = array();
					break;
			}
		}
		$other = array_merge($other, $stack);

		if ($split) {
			return array(array_merge($vars, $imports, $vars), $other);
		} else {
			return array_merge($vars, $imports, $vars, $other);
		}
	}

	protected function compileMediaQuery($queries)
	{
		$compiledQueries = array();
		foreach ($queries as $query) {
			$parts = array();
			foreach ($query as $q) {
				switch ($q[0]) {
					case "mediaType":
						$parts[] = implode(" ", array_slice($q, 1));
						break;
					case "mediaExp":
						if (isset($q[2])) {
							$parts[] = "($q[1]: " .
								$this->compileValue($this->reduce($q[2])) . ")";
						} else {
							$parts[] = "($q[1])";
						}
						break;
					case "variable":
						$parts[] = $this->compileValue($this->reduce($q));
						break;
				}
			}

			if (count($parts) > 0) {
				$compiledQueries[] =  implode(" and ", $parts);
			}
		}

		$out = "@media";
		if (!empty($parts)) {
			$out .= " " .
				implode($this->formatter->selectorSeparator, $compiledQueries);
		}
		return $out;
	}

	protected function multiplyMedia($env, $childQueries = null)
	{
		if (
			is_null($env) ||
			!empty($env->block->type) && $env->block->type != "media"
		) {
			return $childQueries;
		}

		// plain old block, skip
		if (empty($env->block->type)) {
			return $this->multiplyMedia($env->parent, $childQueries);
		}

		$out = array();
		$queries = $env->block->queries;
		if (is_null($childQueries)) {
			$out = $queries;
		} else {
			foreach ($queries as $parent) {
				foreach ($childQueries as $child) {
					$out[] = array_merge($parent, $child);
				}
			}
		}

		return $this->multiplyMedia($env->parent, $out);
	}

	protected function expandParentSelectors(&$tag, $replace)
	{
		$parts = explode("$&$", $tag);
		$count = 0;
		foreach ($parts as &$part) {
			$part = str_replace($this->parentSelector, $replace, $part, $c);
			$count += $c;
		}
		$tag = implode($this->parentSelector, $parts);
		return $count;
	}

	protected function findClosestSelectors()
	{
		$env = $this->env;
		$selectors = null;
		while ($env !== null) {
			if (isset($env->selectors)) {
				$selectors = $env->selectors;
				break;
			}
			$env = $env->parent;
		}

		return $selectors;
	}


	// multiply $selectors against the nearest selectors in env
	protected function multiplySelectors($selectors)
	{
		// find parent selectors

		$parentSelectors = $this->findClosestSelectors();
		if (is_null($parentSelectors)) {
			// kill parent reference in top level selector
			foreach ($selectors as &$s) {
				$this->expandParentSelectors($s, "");
			}

			return $selectors;
		}

		$out = array();
		foreach ($parentSelectors as $parent) {
			foreach ($selectors as $child) {
				$count = $this->expandParentSelectors($child, $parent);

				// don't prepend the parent tag if & was used
				if ($count > 0) {
					$out[] = trim($child);
				} else {
					$out[] = trim($parent . ' ' . $child);
				}
			}
		}

		return $out;
	}

	// reduces selector expressions
	protected function compileSelectors($selectors)
	{
		$out = array();

		foreach ($selectors as $s) {
			if (is_array($s)) {
				[, $value] = $s;
				$out[] = trim($this->compileValue($this->reduce($value)));
			} else {
				$out[] = $s;
			}
		}

		return $out;
	}

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

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

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

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

					$this->popEnv();

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

				if ($groupPassed) break;
			}

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

		if (empty($block->args)) {
			return $block->isVararg || empty($orderedArgs) && empty($keywordArgs);
		}

		$remainingArgs = $block->args;
		if ($keywordArgs) {
			$remainingArgs = array();
			foreach ($block->args as $arg) {
				if ($arg[0] == "arg" && isset($keywordArgs[$arg[1]])) {
					continue;
				}

				$remainingArgs[] = $arg;
			}
		}

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

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

	protected function patternMatchAll($blocks, $orderedArgs, $keywordArgs, $skip = array())
	{
		$matches = null;
		foreach ($blocks as $block) {
			// skip seen blocks that don't have arguments
			if (isset($skip[$block->id]) && !isset($block->args)) {
				continue;
			}

			if ($this->patternMatch($block, $orderedArgs, $keywordArgs)) {
				$matches[] = $block;
			}
		}

		return $matches;
	}

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

		$name = $path[0];

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

					if (!is_null($subMatches)) {
						foreach ($subMatches as $sm) {
							$matches[] = $sm;
						}
					}
				}

				return count($matches) > 0 ? $matches : null;
			}
		}
		if ($searchIn->parent === $searchIn) return null;
		return $this->findBlocks($searchIn->parent, $path, $orderedArgs, $keywordArgs, $seen);
	}

	// sets all argument names in $args to either the default value
	// or the one passed in through $values
	protected function zipSetArgs($args, $orderedValues, $keywordValues)
	{
		$assignedValues = array();

		$i = 0;
		foreach ($args as  $a) {
			if ($a[0] == "arg") {
				if (isset($keywordValues[$a[1]])) {
					// has keyword arg
					$value = $keywordValues[$a[1]];
				} elseif (isset($orderedValues[$i])) {
					// has ordered arg
					$value = $orderedValues[$i];
					$i++;
				} elseif (isset($a[2])) {
					// has default value
					$value = $a[2];
				} else {
					$this->throwError("Failed to assign arg " . $a[1]);
					$value = null; // :(
				}

				$value = $this->reduce($value);
				$this->set($a[1], $value);
				$assignedValues[] = $value;
			} else {
				// a lit
				$i++;
			}
		}

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

		// wow is this the only true use of PHP's + operator for arrays?
		$this->env->arguments = $assignedValues + $orderedValues;
	}

	// compile a prop and update $lines or $blocks appropriately
	protected function compileProp($prop, $block, $out)
	{
		// set error position context
		$this->sourceLoc = isset($prop[-1]) ? $prop[-1] : -1;

		switch ($prop[0]) {
			case 'assign':
				[, $name, $value] = $prop;
				if ($name[0] == $this->vPrefix) {
					$this->set($name, $value);
				} else {
					$out->lines[] = $this->formatter->property(
						$name,
						$this->compileValue($this->reduce($value))
					);
				}
				break;
			case 'block':
				[, $child] = $prop;
				$this->compileBlock($child);
				break;
			case 'ruleset':
			case 'mixin':
				[, $path, $args, $suffix] = $prop;

				$orderedArgs = array();
				$keywordArgs = array();
				foreach ((array)$args as $arg) {
					$argval = null;
					switch ($arg[0]) {
						case "arg":
							if (!isset($arg[2])) {
								$orderedArgs[] = $this->reduce(array("variable", $arg[1]));
							} else {
								$keywordArgs[$arg[1]] = $this->reduce($arg[2]);
							}
							break;

						case "lit":
							$orderedArgs[] = $this->reduce($arg[1]);
							break;
						default:
							$this->throwError("Unknown arg type: " . $arg[0]);
					}
				}

				$mixins = $this->findBlocks($block, $path, $orderedArgs, $keywordArgs);

				if ($mixins === null) {
					$block->parser->throwError("{$prop[1][0]} is undefined", $block->count);
				}

				if (strpos($prop[1][0], "$") === 0) {
					//Use Ruleset Logic - Only last element
					$mixins = array(array_pop($mixins));
				}

				foreach ($mixins as $mixin) {
					if ($mixin === $block && !$orderedArgs) {
						continue;
					}

					$haveScope = false;
					if (isset($mixin->parent->scope)) {
						$haveScope = true;
						$mixinParentEnv = $this->pushEnv();
						$mixinParentEnv->storeParent = $mixin->parent->scope;
					}

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

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

					foreach ($this->sortProps($mixin->props) as $subProp) {
						if (
							$suffix !== null &&
							$subProp[0] == "assign" &&
							is_string($subProp[1]) &&
							$subProp[1][0] != $this->vPrefix
						) {
							$subProp[2] = array(
								'list',
								' ',
								array($subProp[2], array('keyword', $suffix))
							);
						}

						$this->compileProp($subProp, $mixin, $out);
					}

					$mixin->parent = $oldParent;

					if ($haveArgs) $this->popEnv();
					if ($haveScope) $this->popEnv();
				}

				break;
			case 'raw':
				$out->lines[] = $prop[1];
				break;
			case "directive":
				[, $name, $value] = $prop;
				$out->lines[] = "@$name " . $this->compileValue($this->reduce($value)) . ';';
				break;
			case "comment":
				$out->lines[] = $prop[1];
				break;
			case "import";
				[, $importPath, $importId] = $prop;
				$importPath = $this->reduce($importPath);

				if (!isset($this->env->imports)) {
					$this->env->imports = array();
				}

				$result = $this->tryImport($importPath, $block, $out);

				$this->env->imports[$importId] = $result === false ?
					array(false, "@import " . $this->compileValue($importPath) . ";") :
					$result;

				break;
			case "import_mixin":
				[, $importId] = $prop;
				$import = $this->env->imports[$importId];
				if ($import[0] === false) {
					if (isset($import[1])) {
						$out->lines[] = $import[1];
					}
				} else {
					[, $bottom, $parser, $importDir] = $import;
					$this->compileImportedProps($bottom, $block, $out, $parser, $importDir);
				}

				break;
			default:
				$block->parser->throwError("unknown op: {$prop[0]}\n", $block->count);
		}
	}


	/**
	 * 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]*)
	 *
	 * The input is expected to be reduced. This function will not work on
	 * things like expressions and variables.
	 */
	public function compileValue($value)
	{
		switch ($value[0]) {
			case 'list':
				// [1] - delimiter
				// [2] - array of values
				return implode($value[1], array_map(array($this, 'compileValue'), $value[2]));
			case 'raw_color':
				if (!empty($this->formatter->compressColors)) {
					return $this->compileValue($this->coerceColor($value));
				}
				return $value[1];
			case 'keyword':
				// [1] - the keyword
				return $value[1];
			case 'number':
				[, $num, $unit] = $value;
				// [1] - the number
				// [2] - the unit
				if ($this->numberPrecision !== null) {
					$num = round($num, $this->numberPrecision);
				}
				return $num . $unit;
			case 'string':
				// [1] - contents of string (includes quotes)
				[, $delim, $content] = $value;
				foreach ($content as &$part) {
					if (is_array($part)) {
						$part = $this->compileValue($part);
					}
				}
				return $delim . implode($content) . $delim;
			case 'color':
				// [1] - red component (either number or a %)
				// [2] - green component
				// [3] - blue component
				// [4] - optional alpha component
				[, $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] . ')';
				}

				$h = sprintf("#%02x%02x%02x", $r, $g, $b);

				if (!empty($this->formatter->compressColors)) {
					// Converting hex color to short notation (e.g. #003399 to #039)
					if ($h[1] === $h[2] && $h[3] === $h[4] && $h[5] === $h[6]) {
						$h = '#' . $h[1] . $h[3] . $h[5];
					}
				}

				return $h;

			case 'function':
				[, $name, $args] = $value;
				return $name . '(' . $this->compileValue($args) . ')';
			default: // assumed to be unit
				$this->throwError("unknown value type: $value[0]");
		}
	}

	protected function lib_pow($args)
	{
		[$base, $exp] = $this->assertArgs($args, 2, "pow");
		return array("number", pow($this->assertNumber($base), $this->assertNumber($exp)), $args[2][0][2]);
	}

	protected function lib_pi()
	{
		return pi();
	}

	protected function lib_mod($args)
	{
		[$a, $b] = $this->assertArgs($args, 2, "mod");
		return array("number", $this->assertNumber($a) % $this->assertNumber($b), $args[2][0][2]);
	}

	protected function lib_convert($args)
	{
		[$value, $to] = $this->assertArgs($args, 2, "convert");

		// If it's a keyword, grab the string version instead
		if (is_array($to) && $to[0] == "keyword")
			$to = $to[1];

		return $this->convert($value, $to);
	}

	protected function lib_abs($num)
	{
		return array("number", abs($this->assertNumber($num)), $num[2]);
	}

	protected function lib_min($args)
	{
		$values = $this->assertMinArgs($args, 1, "min");

		$first_format = $values[0][2];

		$min_index = 0;
		$min_value = $values[0][1];

		for ($a = 0; $a < sizeof($values); $a++) {
			$converted = $this->convert($values[$a], $first_format);

			if ($converted[1] < $min_value) {
				$min_index = $a;
				$min_value = $values[$a][1];
			}
		}

		return $values[$min_index];
	}

	protected function lib_max($args)
	{
		$values = $this->assertMinArgs($args, 1, "max");

		$first_format = $values[0][2];

		$max_index = 0;
		$max_value = $values[0][1];

		for ($a = 0; $a < sizeof($values); $a++) {
			$converted = $this->convert($values[$a], $first_format);

			if ($converted[1] > $max_value) {
				$max_index = $a;
				$max_value = $values[$a][1];
			}
		}

		return $values[$max_index];
	}

	protected function lib_tan($num)
	{
		return tan($this->assertNumber($num));
	}

	protected function lib_sin($num)
	{
		return sin($this->assertNumber($num));
	}

	protected function lib_cos($num)
	{
		return cos($this->assertNumber($num));
	}

	protected function lib_atan($num)
	{
		$num = atan($this->assertNumber($num));
		return array("number", $num, "rad");
	}

	protected function lib_asin($num)
	{
		$num = asin($this->assertNumber($num));
		return array("number", $num, "rad");
	}

	protected function lib_acos($num)
	{
		$num = acos($this->assertNumber($num));
		return array("number", $num, "rad");
	}

	protected function lib_sqrt($num)
	{
		return sqrt($this->assertNumber($num));
	}

	protected function lib_extract($value)
	{
		[$list, $idx] = $this->assertArgs($value, 2, "extract");
		$idx = $this->assertNumber($idx);
		// 1 indexed
		if ($list[0] == "list" && isset($list[2][$idx - 1])) {
			return $list[2][$idx - 1];
		}
	}

	protected function lib_isnumber($value)
	{
		return $this->toBool($value[0] == "number");
	}

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

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

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

	protected function lib_ispixel($value)
	{
		return $this->toBool($value[0] == "number" && $value[2] == "px");
	}

	protected function lib_ispercentage($value)
	{
		return $this->toBool($value[0] == "number" && $value[2] == "%");
	}

	protected function lib_isem($value)
	{
		return $this->toBool($value[0] == "number" && $value[2] == "em");
	}

	protected function lib_isrem($value)
	{
		return $this->toBool($value[0] == "number" && $value[2] == "rem");
	}

	protected 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 : 255,
			$color[1],
			$color[2],
			$color[3]
		);
	}

	protected function lib_argb($color)
	{
		return $this->lib_rgbahex($color);
	}

	/**
	 * Given an url, decide whether to output a regular link or the base64-encoded contents of the file
	 *
	 * @param  array  $value either an argument list (two strings) or a single string
	 * @return string        formatted url(), either as a link or base64-encoded
	 */
	protected function lib_data_uri($value)
	{
		$mime = ($value[0] === 'list') ? $value[2][0][2] : null;
		$url = ($value[0] === 'list') ? $value[2][1][2][0] : $value[2][0];

		$fullpath = $this->findImport($url);

		if ($fullpath && ($fsize = filesize($fullpath)) !== false) {
			// IE8 can't handle data uris larger than 32KB
			if ($fsize / 1024 < 32) {
				if (is_null($mime)) {
					if (class_exists('finfo')) { // php 5.3+
						$finfo = new finfo(FILEINFO_MIME);
						$mime = explode('; ', $finfo->file($fullpath));
						$mime = $mime[0];
					} elseif (function_exists('mime_content_type')) { // PHP 5.2
						$mime = mime_content_type($fullpath);
					}
				}

				if (!is_null($mime)) // fallback if the mime type is still unknown
					$url = sprintf('data:%s;base64,%s', $mime, base64_encode(file_get_contents($fullpath)));
			}
		}

		return 'url("' . $url . '")';
	}

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

	protected function lib__sprintf($args)
	{
		if ($args[0] != "list") return $args;
		$values = $args[2];
		$string = array_shift($values);
		$template = $this->compileValue($this->lib_e($string));

		$i = 0;
		if (preg_match_all('/%[dsa]/', $template, $m)) {
			foreach ($m[0] as $match) {
				$val = isset($values[$i]) ?
					$this->reduce($values[$i]) : array('keyword', '');

				// lessjs compat, renders fully expanded color, not raw color
				if ($color = $this->coerceColor($val)) {
					$val = $color;
				}

				$i++;
				$rep = $this->compileValue($this->lib_e($val));
				$template = preg_replace(
					'/' . self::preg_quote($match) . '/',
					$rep,
					$template,
					1
				);
			}
		}

		$d = $string[0] == "string" ? $string[1] : '"';
		return array("string", $d, array($template));
	}

	protected function lib_floor($arg)
	{
		$value = $this->assertNumber($arg);
		return array("number", floor($value), $arg[2]);
	}

	protected function lib_ceil($arg)
	{
		$value = $this->assertNumber($arg);
		return array("number", ceil($value), $arg[2]);
	}

	protected function lib_round($arg)
	{
		if ($arg[0] != "list") {
			$value = $this->assertNumber($arg);
			return array("number", round($value), $arg[2]);
		} else {
			$value = $this->assertNumber($arg[2][0]);
			$precision = $this->assertNumber($arg[2][1]);
			return array("number", round($value, $precision), $arg[2][0][2]);
		}
	}

	protected function lib_unit($arg)
	{
		if ($arg[0] == "list") {
			[$number, $newUnit] = $arg[2];
			return array(
				"number",
				$this->assertNumber($number),
				$this->compileValue($this->lib_e($newUnit))
			);
		} else {
			return array("number", $this->assertNumber($arg), "");
		}
	}

	/**
	 * Helper function to get arguments for color manipulation functions.
	 * takes a list that contains a color like thing and a percentage
	 */
	public function colorArgs($args)
	{
		if ($args[0] != 'list' || count($args[2]) < 2) {
			return array(array('color', 0, 0, 0), 0);
		}
		[$color, $delta] = $args[2];
		$color = $this->assertColor($color);
		$delta = floatval($delta[1]);

		return array($color, $delta);
	}

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

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

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

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

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

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

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

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

	protected function lib_spin($args)
	{
		[$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);
	}

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

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

	protected function lib_hue($color)
	{
		$hsl = $this->toHSL($this->assertColor($color));
		return round($hsl[1]);
	}

	protected function lib_saturation($color)
	{
		$hsl = $this->toHSL($this->assertColor($color));
		return round($hsl[2]);
	}

	protected function lib_lightness($color)
	{
		$hsl = $this->toHSL($this->assertColor($color));
		return round($hsl[3]);
	}

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

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

	protected function lib_percentage($arg)
	{
		$num = $this->assertNumber($arg);
		return array("number", $num * 100, "%");
	}

	// mixes two colors by weight
	// mix(@color1, @color2, [@weight: 50%]);
	// http://sass-lang.com/docs/yardoc/Sass/Script/Functions.html#mix-instance_method
	protected function lib_mix($args)
	{
		if ($args[0] != "list" || count($args[2]) < 2)
			$this->throwError("mix expects (color1, color2, weight)");

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

		$first_a = $this->lib_alpha($first);
		$second_a = $this->lib_alpha($second);

		if (isset($args[2][2])) {
			$weight = $args[2][2][1] / 100.0;
		} else {
			$weight = 0.5;
		}

		$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);
	}

	protected function lib_contrast($args)
	{
		$darkColor  = array('color', 0, 0, 0);
		$lightColor = array('color', 255, 255, 255);
		$threshold  = 0.43;

		if ($args[0] == 'list') {
			$inputColor = (isset($args[2][0])) ? $this->assertColor($args[2][0])  : $lightColor;
			$darkColor  = (isset($args[2][1])) ? $this->assertColor($args[2][1])  : $darkColor;
			$lightColor = (isset($args[2][2])) ? $this->assertColor($args[2][2])  : $lightColor;
			if (isset($args[2][3])) {
				if (isset($args[2][3][2]) && $args[2][3][2] == '%') {
					$args[2][3][1] /= 100;
					unset($args[2][3][2]);
				}
				$threshold = $this->assertNumber($args[2][3]);
			}
		} else {
			$inputColor  = $this->assertColor($args);
		}

		$inputColor = $this->coerceColor($inputColor);
		$darkColor  = $this->coerceColor($darkColor);
		$lightColor = $this->coerceColor($lightColor);

		//Figure out which is actually light and dark!
		if ($this->lib_luma($darkColor) > $this->lib_luma($lightColor)) {
			$t  = $lightColor;
			$lightColor = $darkColor;
			$darkColor  = $t;
		}

		$inputColor_alpha = $this->lib_alpha($inputColor);
		if (($this->lib_luma($inputColor) * $inputColor_alpha) < $threshold) {
			return $lightColor;
		}
		return $darkColor;
	}

	protected function lib_luma($color)
	{
		$color = $this->coerceColor($color);
		return (0.2126 * $color[1] / 255) + (0.7152 * $color[2] / 255) + (0.0722 * $color[3] / 255);
	}


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

	public function assertNumber($value, $error = "expecting number")
	{
		if ($value[0] == "number") return $value[1];
		$this->throwError($error);
	}

	public function assertArgs($value, $expectedArgs, $name = "")
	{
		if ($expectedArgs == 1) {
			return $value;
		} else {
			if ($value[0] !== "list" || $value[1] != ",") $this->throwError("expecting list");
			$values = $value[2];
			$numValues = count($values);
			if ($expectedArgs != $numValues) {
				if ($name) {
					$name = $name . ": ";
				}

				$this->throwError("{$name}expecting $expectedArgs arguments, got $numValues");
			}

			return $values;
		}
	}

	public function assertMinArgs($value, $expectedMinArgs, $name = "")
	{
		if ($value[0] !== "list" || $value[1] != ",") $this->throwError("expecting list");
		$values = $value[2];
		$numValues = count($values);
		if ($expectedMinArgs > $numValues) {
			if ($name) {
				$name = $name . ": ";
			}

			$this->throwError("{$name}expecting at least $expectedMinArgs arguments, got $numValues");
		}

		return $values;
	}

	protected 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;
	}

	protected 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
	 */
	protected function toRGB($color)
	{
		if ($color[0] == '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;
	}

	protected 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.
	 */
	protected 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 < 3) $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] == "number" && $c[2] == "%") {
						$components[] = 255 * ($c[1] / 100);
					} else {
						$components[] = floatval($c[1]);
					}
				} elseif ($i == 4) {
					if ($c[0] == "number" && $c[2] == "%") {
						$components[] = 1.0 * ($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;
	}

	protected function reduce($value, $forExpression = false)
	{
		switch ($value[0]) {
			case "interpolate":
				$reduced = $this->reduce($value[1]);
				$var = $this->compileValue($reduced);
				$res = $this->reduce(array("variable", $this->vPrefix . $var));

				if ($res[0] == "raw_color") {
					$res = $this->coerceColor($res);
				}

				if (empty($value[2])) $res = $this->lib_e($res);

				return $res;
			case "variable":
				$key = $value[1];
				if (is_array($key)) {
					$key = $this->reduce($key);
					$key = $this->vPrefix . $this->compileValue($this->lib_e($key));
				}

				$seen = &$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 $out;
			case "list":
				foreach ($value[2] as &$item) {
					$item = $this->reduce($item, $forExpression);
				}
				return $value;
			case "expression":
				return $this->evaluate($value);
			case "string":
				foreach ($value[2] as &$part) {
					if (is_array($part)) {
						$strip = $part[0] == "variable";
						$part = $this->reduce($part);
						if ($strip) $part = $this->lib_e($part);
					}
				}
				return $value;
			case "escape":
				[, $inner] = $value;
				return $this->lib_e($this->reduce($inner));
			case "function":
				$color = $this->funcToColor($value);
				if ($color) return $color;

				[, $name, $args] = $value;
				if ($name == "%") $name = "_sprintf";

				$f = isset($this->libFunctions[$name]) ?
					$this->libFunctions[$name] : array($this, 'lib_' . str_replace('-', '_', $name));

				if (is_callable($f)) {
					if ($args[0] == 'list')
						$args = self::compressList($args[2], $args[1]);

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

					if (is_null($ret)) {
						return array("string", "", array(
							$name,
							"(",
							$args,
							")"
						));
					}

					// convert to a typed value if the result is a php primitive
					if (is_numeric($ret)) $ret = array('number', $ret, "");
					elseif (!is_array($ret)) $ret = array('keyword', $ret);

					return $ret;
				}

				// plain function, reduce args
				$value[2] = $this->reduce($value[2]);
				return $value;
			case "unary":
				[, $op, $exp] = $value;
				$exp = $this->reduce($exp);

				if ($exp[0] == "number") {
					switch ($op) {
						case "+":
							return $exp;
						case "-":
							$exp[1] *= -1;
							return $exp;
					}
				}
				return array("string", "", array($op, $exp));
		}

		if ($forExpression) {
			switch ($value[0]) {
				case "keyword":
					if ($color = $this->coerceColor($value)) {
						return $color;
					}
					break;
				case "raw_color":
					return $this->coerceColor($value);
			}
		}

		return $value;
	}


	// coerce a value for use in color operation
	protected function coerceColor($value)
	{
		switch ($value[0]) {
			case 'color':
				return $value;
			case 'raw_color':
				$c = array("color", 0, 0, 0);
				$colorStr = substr($value[1], 1);
				$num = hexdec($colorStr);
				$width = strlen($colorStr) == 3 ? 16 : 256;

				for ($i = 3; $i > 0; $i--) { // 3 2 1
					$t = $num % $width;
					$num /= $width;

					$c[$i] = $t * (256 / $width) + $t * floor(16 / $width);
				}

				return $c;
			case 'keyword':
				$name = $value[1];
				if (isset(self::$cssColors[$name])) {
					$rgba = explode(',', self::$cssColors[$name]);

					if (isset($rgba[3]))
						return array('color', $rgba[0], $rgba[1], $rgba[2], $rgba[3]);

					return array('color', $rgba[0], $rgba[1], $rgba[2]);
				}
				return null;
		}
	}

	// make something string like into a string
	protected function coerceString($value)
	{
		switch ($value[0]) {
			case "string":
				return $value;
			case "keyword":
				return array("string", "", array($value[1]));
		}
		return null;
	}

	// turn list of length 1 into value type
	protected function flattenList($value)
	{
		if ($value[0] == "list" && count($value[2]) == 1) {
			return $this->flattenList($value[2][0]);
		}
		return $value;
	}

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

	// evaluate an expression
	protected function evaluate($exp)
	{
		[, $op, $left, $right, $whiteBefore, $whiteAfter] = $exp;

		$left = $this->reduce($left, true);
		$right = $this->reduce($right, true);

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

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

		$ltype = $left[0];
		$rtype = $right[0];

		// operators that work on all types
		if ($op == "and") {
			return $this->toBool($left == self::$TRUE && $right == self::$TRUE);
		}

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

		if ($op == "+" && !is_null($str = $this->stringConcatenate($left, $right))) {
			return $str;
		}

		// type based operators
		$fname = "op_{$ltype}_{$rtype}";
		if (is_callable(array($this, $fname))) {
			$out = $this->$fname($op, $left, $right);
			if (!is_null($out)) return $out;
		}

		// make the expression look it did before being parsed
		$paddedOp = $op;
		if ($whiteBefore) $paddedOp = " " . $paddedOp;
		if ($whiteAfter) $paddedOp .= " ";

		return array("string", "", array($left, $paddedOp, $right));
	}

	protected function stringConcatenate($left, $right)
	{
		if ($strLeft = $this->coerceString($left)) {
			if ($right[0] == "string") {
				$right[1] = "";
			}
			$strLeft[2][] = $right;
			return $strLeft;
		}

		if ($strRight = $this->coerceString($right)) {
			array_unshift($strRight[2], $left);
			return $strRight;
		}
	}

	protected function convert($number, $to)
	{
		$value = $this->assertNumber($number);
		$from = $number[2];

		// easy out
		if ($from == $to)
			return $number;

		// check if the from value is a length
		if (($from_index = array_search($from, self::$lengths)) !== false) {
			// make sure to value is too
			if (in_array($to, self::$lengths)) {
				// do the actual conversion
				$to_index = array_search($to, self::$lengths);
				$px = $value * self::$lengths_to_base[$from_index];
				$result = $px * (1 / self::$lengths_to_base[$to_index]);

				$result = round($result, 8);
				return array("number", $result, $to);
			}
		}

		// do the same check for times
		if (in_array($from, self::$times)) {
			if (in_array($to, self::$times)) {
				// currently only ms and s are valid
				if ($to == "ms")
					$result = $value * 1000;
				else
					$result = $value / 1000;

				$result = round($result, 8);
				return array("number", $result, $to);
			}
		}

		// lastly check for an angle
		if (in_array($from, self::$angles)) {
			// convert whatever angle it is into degrees
			if ($from == "rad")
				$deg = rad2deg($value);

			else if ($from == "turn")
				$deg = $value * 360;

			else if ($from == "grad")
				$deg = $value / (400 / 360);

			else
				$deg = $value;

			// Then convert it from degrees into desired unit
			if ($to == "deg")
				$result = $deg;

			if ($to == "rad")
				$result = deg2rad($deg);

			if ($to == "turn")
				$result = $value / 360;

			if ($to == "grad")
				$result = $value * (400 / 360);

			$result = round($result, 8);
			return array("number", $result, $to);
		}

		// we don't know how to convert these
		$this->throwError("Cannot convert {$from} to {$to}");
	}

	// make sure a color's components don't go out of bounds
	protected 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;
	}

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

	protected 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])
		);
	}

	protected 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);
	}

	function lib_red($color)
	{
		$color = $this->coerceColor($color);
		if (is_null($color)) {
			$this->throwError('color expected for red()');
		}

		return $color[1];
	}

	function lib_green($color)
	{
		$color = $this->coerceColor($color);
		if (is_null($color)) {
			$this->throwError('color expected for green()');
		}

		return $color[2];
	}

	function lib_blue($color)
	{
		$color = $this->coerceColor($color);
		if (is_null($color)) {
			$this->throwError('color expected for blue()');
		}

		return $color[3];
	}


	// operator on two numbers
	protected function op_number_number($op, $left, $right)
	{
		$unit = empty($left[2]) ? $right[2] : $left[2];

		$value = 0;
		switch ($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("number", $value, $unit);
	}


	/* environment functions */

	protected function makeOutputBlock($type, $selectors = null)
	{
		$b = new stdclass;
		$b->lines = array();
		$b->children = array();
		$b->selectors = $selectors;
		$b->type = $type;
		$b->parent = $this->scope;
		return $b;
	}

	// the state of execution
	protected function pushEnv($block = null)
	{
		$e = new stdclass;
		$e->parent = $this->env;
		$e->store = array();
		$e->block = $block;

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

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

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


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

		// track scope to evaluate
		$scope_secondary = array();

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

			if (isset($current->store[$name]))
				return $current->store[$name];
			// has secondary scope?
			if (isset($current->storeParent))
				$scope_secondary[] = $current->storeParent;

			if (isset($current->parent))
				$current = $current->parent;
			else
				$current = null;
		}

		while (count($scope_secondary)) {
			// pop one off
			$current = array_shift($scope_secondary);
			while ($current) {
				if ($isArguments && isset($current->arguments)) {
					return array('list', ' ', $current->arguments);
				}

				if (isset($current->store[$name])) {
					return $current->store[$name];
				}

				// has secondary scope?
				if (isset($current->storeParent)) {
					$scope_secondary[] = $current->storeParent;
				}

				if (isset($current->parent)) {
					$current = $current->parent;
				} else {
					$current = null;
				}
			}
		}

		$this->throwError("variable $name is undefined");
	}

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

			$this->set($name, $value);
		}
	}

	/**
	 * Initialize any static state, can initialize parser for a file
	 * $opts isn't used yet
	 */
	public function __construct($fname = null)
	{
		if ($fname !== null) {
			// used for deprecated parse method
			$this->_parseFile = $fname;
		}
	}

	public function compile($string, $name = null)
	{
		$locale = setlocale(LC_NUMERIC, 0);
		setlocale(LC_NUMERIC, "C");

		$this->parser = $this->makeParser($name);
		$root = $this->parser->parse($string);

		$this->env = null;
		$this->scope = null;
		$this->allParsedFiles = array();

		$this->formatter = $this->newFormatter();

		if (!empty($this->registeredVars)) {
			$this->injectVariables($this->registeredVars);
		}

		$this->sourceParser = $this->parser; // used for error messages
		$this->compileBlock($root);

		ob_start();
		$this->formatter->block($this->scope);
		$out = ob_get_clean();
		setlocale(LC_NUMERIC, $locale);
		return $out;
	}

	public function compileFile($fname, $outFname = null)
	{
		if (!is_readable($fname)) {
			throw new \Exception('load error: failed to find ' . $fname);
		}

		$pi = pathinfo($fname);

		$oldImport = $this->importDir;

		$this->importDir = (array)$this->importDir;
		$this->importDir[] = $pi['dirname'] . '/';

		$this->addParsedFile($fname);

		$out = $this->compile(file_get_contents($fname), $fname);

		$this->importDir = $oldImport;

		if ($outFname !== null) {
			return file_put_contents($outFname, $out);
		}

		return $out;
	}

	/**
	 * Based on explicit input/output files does a full change check on cache before compiling.
	 *
	 * @param string $in
	 * @param string $out
	 * @param boolean $force
	 * @return string Compiled CSS results
	 * @throws Exception
	 */
	public function checkedCachedCompile($in, $out, $force = false)
	{
		if (!is_file($in) || !is_readable($in)) {
			throw new Exception('Invalid or unreadable input file specified.');
		}
		if (is_dir($out) || !is_writable(file_exists($out) ? $out : dirname($out))) {
			throw new Exception('Invalid or unwritable output file specified.');
		}

		$outMeta = $out . '.meta';
		$metadata = null;
		if (!$force && is_file($outMeta)) {
			$metadata = unserialize(file_get_contents($outMeta));
		}

		$output = $this->cachedCompile($metadata ? $metadata : $in);

		if (!$metadata || $metadata['updated'] != $output['updated']) {
			$css = $output['compiled'];
			unset($output['compiled']);
			file_put_contents($out, $css);
			file_put_contents($outMeta, serialize($output));
		} else {
			$css = file_get_contents($out);
		}

		return $css;
	}

	// compile only if changed input has changed or output doesn't exist
	public function checkedCompile($in, $out)
	{
		if (!is_file($out) || filemtime($in) > filemtime($out)) {
			$this->compileFile($in, $out);
			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 $force Force rebuild?
	 * @return array lessphp cache structure
	 */
	public function cachedCompile($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.
			$out = array();
			$out['root'] = $root;
			$out['compiled'] = $this->compileFile($root);
			$out['files'] = $this->allParsedFiles();
			$out['updated'] = time();
			return $out;
		} else {
			// No changes, pass back the structure
			// we were given initially.
			return $in;
		}
	}

	// parse and compile buffer
	// This is deprecated
	public function parse($str = null, $initialVariables = null)
	{
		if (is_array($str)) {
			$initialVariables = $str;
			$str = null;
		}

		$oldVars = $this->registeredVars;
		if ($initialVariables !== null) {
			$this->setVariables($initialVariables);
		}

		if ($str == null) {
			if (empty($this->_parseFile)) {
				throw new \Exception("nothing to parse");
			}

			$out = $this->compileFile($this->_parseFile);
		} else {
			$out = $this->compile($str);
		}

		$this->registeredVars = $oldVars;
		return $out;
	}

	protected function makeParser($name)
	{
		$parser = new lessc_parser($this, $name);
		$parser->writeComments = $this->preserveComments;

		return $parser;
	}

	public function setFormatter($name)
	{
		$this->formatterName = $name;
	}

	protected function newFormatter()
	{
		$className = "lessc_formatter_lessjs";
		if (!empty($this->formatterName)) {
			if (!is_string($this->formatterName))
				return $this->formatterName;
			$className = "lessc_formatter_$this->formatterName";
		}

		return new $className;
	}

	public function setPreserveComments($preserve)
	{
		$this->preserveComments = $preserve;
	}

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

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

	public function setVariables($variables)
	{
		$this->registeredVars = array_merge($this->registeredVars, $variables);
	}

	public function unsetVariable($name)
	{
		unset($this->registeredVars[$name]);
	}

	public function setImportDir($dirs)
	{
		$this->importDir = (array)$dirs;
	}

	public function addImportDir($dir)
	{
		$this->importDir = (array)$this->importDir;
		$this->importDir[] = $dir;
	}

	public function allParsedFiles()
	{
		return $this->allParsedFiles;
	}

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

	/**
	 * Uses the current value of $this->count to show line and line number
	 */
	public function throwError($msg = null)
	{
		if ($this->sourceLoc >= 0) {
			$this->sourceParser->throwError($msg, $this->sourceLoc);
		}
		throw new \Exception($msg);
	}

	// 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, $less = null)
	{
		if ($less === null) {
			$less = new self;
		}
		return $less->checkedCompile($in, $out);
	}

	public static function cexecute($in, $force = false, $less = null)
	{
		if ($less === null) {
			$less = new self;
		}
		return $less->cachedCompile($in, $force);
	}

	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',
		'transparent' => '0,0,0,0',
		'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'
	);
}

// responsible for taking a string of LESS code and converting it into a
// syntax tree
class lessc_parser
{
	static protected $nextBlockId = 0; // used to uniquely identify blocks

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

		'+' => 1,
		'-' => 1,
		'*' => 2,
		'/' => 2,
		'%' => 2,
	);

	static protected $whitePattern;
	static protected $commentMulti;

	static protected $commentSingle = "//";
	static protected $commentMultiLeft = "/*";
	static protected $commentMultiRight = "*/";

	// regex string to match any of the operators
	static protected $operatorString;

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

	protected $blockDirectives = array("font-face", "keyframes", "page", "-moz-document", "viewport", "-moz-viewport", "-o-viewport", "-ms-viewport");
	protected $lineDirectives = array("charset");

	/**
	 * 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;

	// caches preg escaped literals
	static protected $literalCache = array();

	protected $eatWhiteDefault;
	protected $lessc;
	protected $sourceName;
	public $writeComments;
	public $count;
	protected $line;
	protected $env;
	public $buffer;
	protected $seenComments;
	protected $inExp;


	public function __construct($lessc, $sourceName = null)
	{
		$this->eatWhiteDefault = true;
		// reference to less needed for vPrefix, mPrefix, and parentSelector
		$this->lessc = $lessc;

		$this->sourceName = $sourceName; // name used for error messages

		$this->writeComments = false;

		if (!self::$operatorString) {
			self::$operatorString =
				'(' . implode('|', array_map(
					array('lessc', 'preg_quote'),
					array_keys(self::$precedence)
				)) . ')';

			$commentSingle = lessc::preg_quote(self::$commentSingle);
			$commentMultiLeft = lessc::preg_quote(self::$commentMultiLeft);
			$commentMultiRight = lessc::preg_quote(self::$commentMultiRight);

			self::$commentMulti = $commentMultiLeft . '.*?' . $commentMultiRight;
			self::$whitePattern = '/' . $commentSingle . '[^\n]*\s*|(' . self::$commentMulti . ')\s*|\s+/Ais';
		}
	}

	public function parse($buffer)
	{
		$this->count = 0;
		$this->line = 1;

		$this->env = null; // block stack
		$this->buffer = $this->writeComments ? $buffer : $this->removeComments($buffer);
		$this->pushSpecialBlock("root");
		$this->eatWhiteDefault = true;
		$this->seenComments = array();

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

		// parse the entire file
		while (false !== $this->parseChunk());

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

		// TODO report where the block was opened
		if (!property_exists($this->env, 'parent') || !is_null($this->env->parent))
			throw new \Exception('parse error: unclosed block');

		return $this->env;
	}

	/**
	 * Parse a single chunk off the head of the buffer and append it to the
	 * current parse environment.
	 * Returns 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.
	 */
	protected function parseChunk()
	{
		if (empty($this->buffer)) return false;
		$s = $this->seek();

		if ($this->whitespace()) {
			return true;
		}

		// 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->literal('@', false)) {
			$this->count--;

			// media
			if ($this->literal('@media')) {
				if (($this->mediaQueryList($mediaQueries) || true)
					&& $this->literal('{')
				) {
					$media = $this->pushSpecialBlock("media");
					$media->queries = is_null($mediaQueries) ? array() : $mediaQueries;
					return true;
				} else {
					$this->seek($s);
					return false;
				}
			}

			if ($this->literal("@", false) && $this->keyword($dirName)) {
				if ($this->isDirective($dirName, $this->blockDirectives)) {
					if (($this->openString("{", $dirValue, null, array(";")) || true) &&
						$this->literal("{")
					) {
						$dir = $this->pushSpecialBlock("directive");
						$dir->name = $dirName;
						if (isset($dirValue)) $dir->value = $dirValue;
						return true;
					}
				} elseif ($this->isDirective($dirName, $this->lineDirectives)) {
					if ($this->propertyValue($dirValue) && $this->end()) {
						$this->append(array("directive", $dirName, $dirValue));
						return true;
					}
				} elseif ($this->literal(":", true)) {
					//Ruleset Definition
					if (($this->openString("{", $dirValue, null, array(";")) || true) &&
						$this->literal("{")
					) {
						$dir = $this->pushBlock($this->fixTags(array("@" . $dirName)));
						$dir->name = $dirName;
						if (isset($dirValue)) $dir->value = $dirValue;
						return true;
					}
				}
			}

			$this->seek($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 ($this->import($importValue)) {
			$this->append($importValue, $s);
			return true;
		}

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

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

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

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

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

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

			// this is done here so comments aren't bundled into he block that
			// was just closed
			$this->whitespace();
			return true;
		}

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

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

		return false; // got nothing, throw error
	}

	protected function isDirective($dirname, $directives)
	{
		// TODO: cache pattern in parser
		$pattern = implode(
			"|",
			array_map(array("lessc", "preg_quote"), $directives)
		);
		$pattern = '/^(-[a-z-]+-)?(' . $pattern . ')$/i';

		return preg_match($pattern, $dirname);
	}

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

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

		while ($this->expression($exp)) {
			$values[] = $exp;
		}

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

		$exps = lessc::compressList($values, ' ');
		return true;
	}

	/**
	 * Attempt to consume an expression.
	 * @link http://en.wikipedia.org/wiki/Operator-precedence_parser#Pseudo-code
	 */
	protected function expression(&$out)
	{
		if ($this->value($lhs)) {
			$out = $this->expHelper($lhs, 0);

			// look for / shorthand
			if (!empty($this->env->supressedDivision)) {
				unset($this->env->supressedDivision);
				$s = $this->seek();
				if ($this->literal("/") && $this->value($rhs)) {
					$out = array(
						"list",
						"",
						array($out, array("keyword", "/"), $rhs)
					);
				} else {
					$this->seek($s);
				}
			}

			return true;
		}
		return false;
	}

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

		while (true) {
			$whiteBefore = isset($this->buffer[$this->count - 1]) &&
				ctype_space($this->buffer[$this->count - 1]);

			// If there is whitespace before the operator, then we require
			// whitespace after the operator for it to be an expression
			$needWhite = $whiteBefore && !$this->inParens;

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


				$whiteAfter = isset($this->buffer[$this->count - 1]) &&
					ctype_space($this->buffer[$this->count - 1]);

				if (!$this->value($rhs)) 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]]);
				}

				$lhs = array('expression', $m[1], $lhs, $rhs, $whiteBefore, $whiteAfter);
				$ss = $this->seek();

				continue;
			}

			break;
		}

		$this->seek($ss);

		return $lhs;
	}

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

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

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

		$value = lessc::compressList($values, ', ');
		return true;
	}

	protected function parenValue(&$out)
	{
		$s = $this->seek();

		// speed shortcut
		if (isset($this->buffer[$this->count]) && $this->buffer[$this->count] != "(") {
			return false;
		}

		$inParens = $this->inParens;
		if (
			$this->literal("(") &&
			($this->inParens = true) && $this->expression($exp) &&
			$this->literal(")")
		) {
			$out = $exp;
			$this->inParens = $inParens;
			return true;
		} else {
			$this->inParens = $inParens;
			$this->seek($s);
		}

		return false;
	}

	// a single value
	protected function value(&$value)
	{
		$s = $this->seek();

		// speed shortcut
		if (isset($this->buffer[$this->count]) && $this->buffer[$this->count] == "-") {
			// negation
			if (
				$this->literal("-", false) &&
				(($this->variable($inner) && $inner = array("variable", $inner)) ||
					$this->unit($inner) ||
					$this->parenValue($inner))
			) {
				$value = array("unary", "-", $inner);
				return true;
			} else {
				$this->seek($s);
			}
		}

		if ($this->parenValue($value)) return true;
		if ($this->unit($value)) return true;
		if ($this->color($value)) return true;
		if ($this->func($value)) return true;
		if ($this->stringValue($value)) return true;

		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 (should this work on any type?
		if ($this->literal("~") && $this->stringValue($str)) {
			$value = array("escape", $str);
			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);
		}

		return false;
	}

	// an import statement
	protected function import(&$out)
	{
		if (!$this->literal('@import')) return false;

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

		if ($this->propertyValue($value)) {
			$out = array("import", $value);
			return true;
		}
	}

	protected function mediaQueryList(&$out)
	{
		if ($this->genericList($list, "mediaQuery", ",", false)) {
			$out = $list[2];
			return true;
		}
		return false;
	}

	protected function mediaQuery(&$out)
	{
		$s = $this->seek();

		$expressions = null;
		$parts = array();

		if (($this->literal("only") && ($only = true) || $this->literal("not") && ($not = true) || true) && $this->keyword($mediaType)) {
			$prop = array("mediaType");
			if (isset($only)) $prop[] = "only";
			if (isset($not)) $prop[] = "not";
			$prop[] = $mediaType;
			$parts[] = $prop;
		} else {
			$this->seek($s);
		}


		if (!empty($mediaType) && !$this->literal("and")) {
			// ~
		} else {
			$this->genericList($expressions, "mediaExpression", "and", false);
			if (is_array($expressions)) $parts = array_merge($parts, $expressions[2]);
		}

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

		$out = $parts;
		return true;
	}

	protected function mediaExpression(&$out)
	{
		$s = $this->seek();
		$value = null;
		if (
			$this->literal("(") &&
			$this->keyword($feature) &&
			($this->literal(":") && $this->expression($value) || true) &&
			$this->literal(")")
		) {
			$out = array("mediaExp", $feature);
			if ($value) $out[] = $value;
			return true;
		} elseif ($this->variable($variable)) {
			$out = array('variable', $variable);
			return true;
		}

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

	// an unbounded string stopped by $end
	protected function openString($end, &$out, $nestingOpen = null, $rejectStrs = null)
	{
		$oldWhite = $this->eatWhiteDefault;
		$this->eatWhiteDefault = false;

		$stop = array("'", '"', "@{", $end);
		$stop = array_map(array("lessc", "preg_quote"), $stop);
		// $stop[] = self::$commentMulti;

		if (!is_null($rejectStrs)) {
			$stop = array_merge($stop, $rejectStrs);
		}

		$patt = '(.*?)(' . implode("|", $stop) . ')';

		$nestingLevel = 0;

		$content = array();
		while ($this->match($patt, $m, false)) {
			if (!empty($m[1])) {
				$content[] = $m[1];
				if ($nestingOpen) {
					$nestingLevel += substr_count($m[1], $nestingOpen);
				}
			}

			$tok = $m[2];

			$this->count -= strlen($tok);
			if ($tok == $end) {
				if ($nestingLevel == 0) {
					break;
				} else {
					$nestingLevel--;
				}
			}

			if (($tok == "'" || $tok == '"') && $this->stringValue($str)) {
				$content[] = $str;
				continue;
			}

			if ($tok == "@{" && $this->interpolation($inter)) {
				$content[] = $inter;
				continue;
			}

			if (!empty($rejectStrs) && in_array($tok, $rejectStrs)) {
				break;
			}

			$content[] = $tok;
			$this->count += strlen($tok);
		}

		$this->eatWhiteDefault = $oldWhite;

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

		// trim the end
		if (is_string(end($content))) {
			$content[count($content) - 1] = rtrim(end($content));
		}

		$out = array("string", "", $content);
		return true;
	}

	protected function stringValue(&$out)
	{
		$s = $this->seek();
		if ($this->literal('"', false)) {
			$delim = '"';
		} elseif ($this->literal("'", false)) {
			$delim = "'";
		} else {
			return false;
		}

		$content = array();

		// look for either ending delim , escape, or string interpolation
		$patt = '([^\n]*?)(@\{|\\\\|' .
			lessc::preg_quote($delim) . ')';

		$oldWhite = $this->eatWhiteDefault;
		$this->eatWhiteDefault = false;

		while ($this->match($patt, $m, false)) {
			$content[] = $m[1];
			if ($m[2] == "@{") {
				$this->count -= strlen($m[2]);
				if ($this->interpolation($inter, false)) {
					$content[] = $inter;
				} else {
					$this->count += strlen($m[2]);
					$content[] = "@{"; // ignore it
				}
			} elseif ($m[2] == '\\') {
				$content[] = $m[2];
				if ($this->literal($delim, false)) {
					$content[] = $delim;
				}
			} else {
				$this->count -= strlen($delim);
				break; // delim
			}
		}

		$this->eatWhiteDefault = $oldWhite;

		if ($this->literal($delim)) {
			$out = array("string", $delim, $content);
			return true;
		}

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

	protected function interpolation(&$out)
	{
		$oldWhite = $this->eatWhiteDefault;
		$this->eatWhiteDefault = true;

		$s = $this->seek();
		if (
			$this->literal("@{") &&
			$this->openString("}", $interp, null, array("'", '"', ";")) &&
			$this->literal("}", false)
		) {
			$out = array("interpolate", $interp);
			$this->eatWhiteDefault = $oldWhite;
			if ($this->eatWhiteDefault) $this->whitespace();
			return true;
		}

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

	protected function unit(&$unit)
	{
		// speed shortcut
		if (isset($this->buffer[$this->count])) {
			$char = $this->buffer[$this->count];
			if (!ctype_digit($char) && $char != ".") return false;
		}

		if ($this->match('([0-9]+(?:\.[0-9]*)?|\.[0-9]+)([%a-zA-Z]+)?', $m)) {
			$unit = array("number", $m[1], empty($m[2]) ? "" : $m[2]);
			return true;
		}
		return false;
	}

	// a # color
	protected function color(&$out)
	{
		if ($this->match('(#(?:[0-9a-f]{8}|[0-9a-f]{6}|[0-9a-f]{3}))', $m)) {
			if (strlen($m[1]) > 7) {
				$out = array("string", "", array($m[1]));
			} else {
				$out = array("raw_color", $m[1]);
			}
			return true;
		}

		return false;
	}

	// 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 ...
	// arguments are separated by , unless a ; is in the list, then ; is the
	// delimiter.
	protected function argumentDef(&$args, &$isVararg)
	{
		$s = $this->seek();
		if (!$this->literal('(')) return false;

		$values = array();
		$delim = ",";
		$method = "expressionList";

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

			if ($this->$method($value)) {
				if ($value[0] == "variable") {
					$arg = array("arg", $value[1]);
					$ss = $this->seek();

					if ($this->assign() && $this->$method($rhs)) {
						$arg[] = $rhs;
					} else {
						$this->seek($ss);
						if ($this->literal("...")) {
							$arg[0] = "rest";
							$isVararg = true;
						}
					}

					$values[] = $arg;
					if ($isVararg) break;
					continue;
				} else {
					$values[] = array("lit", $value);
				}
			}


			if (!$this->literal($delim)) {
				if ($delim == "," && $this->literal(";")) {
					// found new delim, convert existing args
					$delim = ";";
					$method = "propertyValue";

					// transform arg list
					if (isset($values[1])) { // 2 items
						$newList = array();
						foreach ($values as $i => $arg) {
							switch ($arg[0]) {
								case "arg":
									if ($i) {
										$this->throwError("Cannot mix ; and , as delimiter types");
									}
									$newList[] = $arg[2];
									break;
								case "lit":
									$newList[] = $arg[1];
									break;
								case "rest":
									$this->throwError("Unexpected rest before semicolon");
							}
						}

						$newList = array("list", ", ", $newList);

						switch ($values[0][0]) {
							case "arg":
								$newArg = array("arg", $values[0][1], $newList);
								break;
							case "lit":
								$newArg = array("lit", $newList);
								break;
						}
					} elseif ($values) { // 1 item
						$newArg = $values[0];
					}

					if ($newArg) {
						$values = array($newArg);
					}
				} else {
					break;
				}
			}
		}

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

		$args = $values;

		return true;
	}

	// consume a list of tags
	// this accepts a hanging delimiter
	protected 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 >)
	protected function mixinTags(&$tags)
	{
		$tags = array();
		while ($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)
	protected function tagBracket(&$parts, &$hasExpression)
	{
		// speed shortcut
		if (isset($this->buffer[$this->count]) && $this->buffer[$this->count] != "[") {
			return false;
		}

		$s = $this->seek();

		$hasInterpolation = false;

		if ($this->literal("[", false)) {
			$attrParts = array("[");
			// keyword, string, operator
			while (true) {
				if ($this->literal("]", false)) {
					$this->count--;
					break; // get out early
				}

				if ($this->match('\s+', $m)) {
					$attrParts[] = " ";
					continue;
				}
				if ($this->stringValue($str)) {
					// escape parent selector, (yuck)
					foreach ($str[2] as &$chunk) {
						if (is_string($chunk)) {
							$chunk = str_replace($this->lessc->parentSelector, "$&$", $chunk);
						}
					}

					$attrParts[] = $str;
					$hasInterpolation = true;
					continue;
				}

				if ($this->keyword($word)) {
					$attrParts[] = $word;
					continue;
				}

				if ($this->interpolation($inter, false)) {
					$attrParts[] = $inter;
					$hasInterpolation = true;
					continue;
				}

				// operator, handles attr namespace too
				if ($this->match('[|-~\$\*\^=]+', $m)) {
					$attrParts[] = $m[0];
					continue;
				}

				break;
			}

			if ($this->literal("]", false)) {
				$attrParts[] = "]";
				foreach ($attrParts as $part) {
					$parts[] = $part;
				}
				$hasExpression = $hasExpression || $hasInterpolation;
				return true;
			}
			$this->seek($s);
		}

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

	// a space separated list of selectors
	protected function tag(&$tag, $simple = false)
	{
		if ($simple)
			$chars = '^@,:;{}\][>\(\) "\'';
		else
			$chars = '^@,;{}["\'';

		$s = $this->seek();

		$hasExpression = false;
		$parts = array();
		while ($this->tagBracket($parts, $hasExpression));

		$oldWhite = $this->eatWhiteDefault;
		$this->eatWhiteDefault = false;

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

				while ($this->tagBracket($parts, $hasExpression));
				continue;
			}

			if (isset($this->buffer[$this->count]) && $this->buffer[$this->count] == "@") {
				if ($this->interpolation($interp)) {
					$hasExpression = true;
					$interp[2] = true; // don't unescape
					$parts[] = $interp;
					continue;
				}

				if ($this->literal("@")) {
					$parts[] = "@";
					continue;
				}
			}

			if ($this->unit($unit)) { // for keyframes
				$parts[] = $unit[1];
				$parts[] = $unit[2];
				continue;
			}

			break;
		}

		$this->eatWhiteDefault = $oldWhite;
		if (!$parts) {
			$this->seek($s);
			return false;
		}

		if ($hasExpression) {
			$tag = array("exp", array("string", "", $parts));
		} else {
			$tag = trim(implode($parts));
		}

		$this->whitespace();
		return true;
	}

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

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

			$sPreArgs = $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)) {
					$args[] = array("string", "", array($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
				$this->seek($sPreArgs);
				if ($this->openString(")", $string) && $this->literal(")")) {
					$func = array('function', $fname, $string);
					return true;
				}
			}
		}

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

	// consume a less variable
	protected function variable(&$name)
	{
		$s = $this->seek();
		if (
			$this->literal($this->lessc->vPrefix, false) &&
			($this->variable($sub) || $this->keyword($name))
		) {
			if (!empty($sub)) {
				$name = array('variable', $sub);
			} else {
				$name = $this->lessc->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
	 */
	protected function assign($name = null)
	{
		if ($name) $this->currentProperty = $name;
		return $this->literal(':') || $this->literal('=');
	}

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

	// consume an end of statement delimiter
	protected function end()
	{
		if ($this->literal(';', false)) {
			return true;
		} elseif ($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;
	}

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

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

		$guards = array();

		while ($this->guardGroup($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
	// TODO rename to guardGroup
	protected function guardGroup(&$guardGroup)
	{
		$s = $this->seek();
		$guardGroup = array();
		while ($this->guard($guard)) {
			$guardGroup[] = $guard;
			if (!$this->literal("and")) break;
		}

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

		return true;
	}

	protected 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;
	}

	/* raw parsing functions */

	protected function literal($what, $eatWhitespace = null)
	{
		if ($eatWhitespace === null) $eatWhitespace = $this->eatWhiteDefault;

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

		if (!isset(self::$literalCache[$what])) {
			self::$literalCache[$what] = lessc::preg_quote($what);
		}

		return $this->match(self::$literalCache[$what], $m, $eatWhitespace);
	}

	protected function genericList(&$out, $parseItem, $delim = "", $flatten = true)
	{
		$s = $this->seek();
		$items = array();
		while ($this->$parseItem($value)) {
			$items[] = $value;
			if ($delim) {
				if (!$this->literal($delim)) break;
			}
		}

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

		if ($flatten && count($items) == 1) {
			$out = $items[0];
		} else {
			$out = array("list", $delim, $items);
		}

		return true;
	}


	// advance counter to next occurrence of $what
	// $until - don't include $what in advance
	// $allowNewline, if string, will be used as valid char set
	protected function to($what, &$out, $until = false, $allowNewline = false)
	{
		if (is_string($allowNewline)) {
			$validChars = $allowNewline;
		} else {
			$validChars = $allowNewline ? "." : "[^\n]";
		}
		if (!$this->match('(' . $validChars . '*?)' . lessc::preg_quote($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
	protected function match($regex, &$out, $eatWhitespace = null)
	{
		if ($eatWhitespace === null) $eatWhitespace = $this->eatWhiteDefault;

		$r = '/' . $regex . ($eatWhitespace && !$this->writeComments ? '\s*' : '') . '/Ais';
		if (preg_match($r, $this->buffer, $out, 0, $this->count)) {
			$this->count += strlen($out[0]);
			if ($eatWhitespace && $this->writeComments) $this->whitespace();
			return true;
		}
		return false;
	}

	// match some whitespace
	protected function whitespace()
	{
		if ($this->writeComments) {
			$gotWhite = false;
			while (preg_match(self::$whitePattern, $this->buffer, $m, 0, $this->count)) {
				if (isset($m[1]) && empty($this->seenComments[$this->count])) {
					$this->append(array("comment", $m[1]));
					$this->seenComments[$this->count] = true;
				}
				$this->count += strlen($m[0]);
				$gotWhite = true;
			}
			return $gotWhite;
		} else {
			$this->match("", $m);
			return strlen($m[0]) > 0;
		}
	}

	// match something without consuming it
	protected function peek($regex, &$out = null, $from = null)
	{
		if (is_null($from)) $from = $this->count;
		$r = '/' . $regex . '/Ais';
		$result = preg_match($r, $this->buffer, $out, 0, $from);

		return $result;
	}

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

	/* misc functions */

	public function throwError($msg = "parse error", $count = null)
	{
		$count = is_null($count) ? $this->count : $count;

		$line = $this->line +
			substr_count(substr($this->buffer, 0, $count), "\n");

		if (!empty($this->sourceName)) {
			$loc = "$this->sourceName on line $line";
		} else {
			$loc = "line: $line";
		}

		// TODO this depends on $this->count
		if ($this->peek("(.*?)(\n|$)", $m, $count)) {
			throw new \Exception("$msg: failed at `$m[1]` $loc");
		} else {
			throw new \Exception("$msg: $loc");
		}
	}

	protected function pushBlock($selectors = null, $type = null)
	{
		$b = new \stdClass();
		$b->parent = $this->env;

		$b->type = $type;
		$b->id = self::$nextBlockId++;

		$b->isVararg = false; // TODO: kill me from here
		$b->tags = $selectors;

		$b->props = array();
		$b->children = array();

		// add a reference to the parser so
		// we can access the parser to throw errors
		// or retrieve the sourceName of this block.
		$b->parser = $this;

		// so we know the position of this block
		$b->count = $this->count;

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

	// push a block that doesn't multiply tags
	protected function pushSpecialBlock($type)
	{
		return $this->pushBlock(null, $type);
	}

	// append a property to the current block
	protected function append($prop, $pos = null)
	{
		if ($pos !== null) $prop[-1] = $pos;
		$this->env->props[] = $prop;
	}

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

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

		$out = '';
		$min = null;
		while (true) {
			// find the next item
			foreach ($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;
	}
}

class lessc_formatter_classic
{
	public $indentChar = "  ";

	public $break = "\n";
	public $open = " {";
	public $close = "}";
	public $selectorSeparator = ", ";
	public $assignSeparator = ":";

	public $openSingle = " { ";
	public $closeSingle = " }";

	public $disableSingle = false;
	public $breakSelectors = false;

	public $compressColors = false;

	public function __construct()
	{
		$this->indentLevel = 0;
	}

	public function indentStr($n = 0)
	{
		return str_repeat($this->indentChar, max($this->indentLevel + $n, 0));
	}

	public function property($name, $value)
	{
		return $name . $this->assignSeparator . $value . ";";
	}

	protected function isEmpty($block)
	{
		if (empty($block->lines)) {
			foreach ($block->children as $child) {
				if (!$this->isEmpty($child)) return false;
			}

			return true;
		}
		return false;
	}

	public function block($block)
	{
		if ($this->isEmpty($block)) return;

		$inner = $pre = $this->indentStr();

		$isSingle = !$this->disableSingle &&
			is_null($block->type) && count($block->lines) == 1;

		if (!empty($block->selectors)) {
			$this->indentLevel++;

			if ($this->breakSelectors) {
				$selectorSeparator = $this->selectorSeparator . $this->break . $pre;
			} else {
				$selectorSeparator = $this->selectorSeparator;
			}

			echo $pre .
				implode($selectorSeparator, $block->selectors);
			if ($isSingle) {
				echo $this->openSingle;
				$inner = "";
			} else {
				echo $this->open . $this->break;
				$inner = $this->indentStr();
			}
		}

		if (!empty($block->lines)) {
			$glue = $this->break . $inner;
			echo $inner . implode($glue, $block->lines);
			if (!$isSingle && !empty($block->children)) {
				echo $this->break;
			}
		}

		foreach ($block->children as $child) {
			$this->block($child);
		}

		if (!empty($block->selectors)) {
			if (!$isSingle && empty($block->children)) echo $this->break;

			if ($isSingle) {
				echo $this->closeSingle . $this->break;
			} else {
				echo $pre . $this->close . $this->break;
			}

			$this->indentLevel--;
		}
	}
}

class lessc_formatter_compressed extends lessc_formatter_classic
{
	public $disableSingle = true;
	public $open = "{";
	public $selectorSeparator = ",";
	public $assignSeparator = ":";
	public $break = "";
	public $compressColors = true;

	public function indentStr($n = 0)
	{
		return "";
	}
}

class lessc_formatter_lessjs extends lessc_formatter_classic
{
	public $disableSingle = true;
	public $breakSelectors = true;
	public $assignSeparator = ": ";
	public $selectorSeparator = ",";
	public $indentLevel;
}