lessc.inc.php

<?php

/**
 * lessphp v0.3.9
 * http://leafo.net/lessphp
 *
 * LESS css compiler, adapted from http://lesscss.org
 *
 * Copyright 2012, Leaf Corcoran <leafot@gmail.com>
 * Licensed under MIT or GPLv3, see LICENSE
 */


/**
 * The less compiler and parser.
 *
 * Converting LESS to CSS is a 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 intstance 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 = "v0.3.9";
  static protected $TRUE = array("keyword", "true");
  static protected $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 = '&';

  public $importDisabled = false;
  public $importDir = '';

  protected $numberPrecision = null;

  // 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 public $defaultValue = array("keyword", "");

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

  /**
   * Write a file to disk.
   *
   * @param string $file - path of file to write
   * @param string $contents - the content to be written to the file
   */
  protected function put_contents($file, $contents) {
    global $wp_filesystem;

    if (empty($wp_filesystem)) {
      require_once(ABSPATH . 'wp-admin/includes/file.php');
      WP_Filesystem();
    }

    return $wp_filesystem->put_contents($file, $contents);
  }

  /**
   * Read a file's contents.
   *
   * @param string $file - path of file to read
   */
  protected function get_contents($file) {
    global $wp_filesystem;

    if (empty($wp_filesystem)) {
      require_once(ABSPATH . 'wp-admin/includes/file.php');
      WP_Filesystem();
    }

    return $wp_filesystem->get_contents($file);
  }

  // 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 */");
    }

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

    list($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:
      $this->throwError("unknown block type: $block->type\n");
    }
  }

  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);
    }
  }

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

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

    if ($split) {
      return array(array_merge($vars, $imports), $other);
    } else {
      return array_merge($vars, $imports, $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)) {
        list(, $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, $callingArgs) {
    // match the guards if it has them
    // any one of the groups must have all its guards pass for a match
    if (!empty($block->guards)) {
      $groupPassed = false;
      foreach ($block->guards as $guardGroup) {
        foreach ($guardGroup as $guard) {
          $this->pushEnv();
          $this->zipSetArgs($block->args, $callingArgs);

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

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

          $this->popEnv();

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

        if ($groupPassed) break;
      }

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

    $numCalling = count($callingArgs);

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

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

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

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

    return $matches;
  }

  // attempt to find blocks matched by path and args
  protected function findBlocks($searchIn, $path, $args, $seen=array()) {
    if ($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, $args);
        if (!empty($matches)) {
          // This will return all blocks that match in the closest
          // scope that has any matching block, like lessjs
          return $matches;
        }
      } else {
        $matches = array();
        foreach ($blocks as $subBlock) {
          $subMatches = $this->findBlocks($subBlock,
            array_slice($path, 1), $args, $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, $args, $seen);
  }

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

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

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

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

  // 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':
      list(, $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':
      list(, $child) = $prop;
      $this->compileBlock($child);
      break;
    case 'mixin':
      list(, $path, $args, $suffix) = $prop;

      $args = array_map(array($this, "reduce"), (array)$args);
      $mixins = $this->findBlocks($block, $path, $args);

      if ($mixins === null) {
        // fwrite(STDERR,"failed to find block: ".implode(" > ", $path)."\n");
        break; // @TODO ? throw error here??
      }

      foreach ($mixins as $mixin) {
        $haveScope = false;
        if (isset($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, $args);
        }

        $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":
      list(, $name, $value) = $prop;
      $out->lines[] = "@$name " . $this->compileValue($this->reduce($value)).';';
      break;
    case "comment":
      $out->lines[] = $prop[1];
      break;
    case "import";
      list(, $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":
      list(,$importId) = $prop;
      $import = $this->env->imports[$importId];
      if ($import[0] === false) {
        $out->lines[] = $import[1];
      } else {
        list(, $bottom, $parser, $importDir) = $import;
        $this->compileImportedProps($bottom, $block, $out, $parser, $importDir);
      }

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


  /**
   * 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.
   */
  protected 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':
      list(, $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)
      list(, $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
      list(, $r, $g, $b) = $value;
      $r = round($r);
      $g = round($g);
      $b = round($b);

      if (count($value) == 5 && $value[4] != 1) { // rgba
        return 'rgba('.$r.','.$g.','.$b.','.$value[4].')';
      }

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

  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);
  }

  // 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]);
        }
        return self::$defaultValue;
      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) {
    $value = $this->assertNumber($arg);
    return array("number", round($value), $arg[2]);
  }

  protected function lib_unit($arg) {
    if ($arg[0] == "list") {
      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
   */
  protected function colorArgs($args) {
    if ($args[0] != 'list' || count($args[2]) < 2) {
      return array(array('color', 0, 0, 0), 0);
    }
    list($color, $delta) = $args[2];
    $color = $this->assertColor($color);
    $delta = floatval($delta[1]);

    return array($color, $delta);
  }

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

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

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

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

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

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

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

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

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

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

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

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

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

  protected function lib_fadein($args) {
    list($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($args) {
    list($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);
  // 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]) < 3)
      $this->throwError("mix expects (color1, color2, weight)");

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

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

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

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

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

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

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

  protected function lib_contrast($args) {
    if ($args[0] != 'list' || count($args[2]) < 3) {
      return array(array('color', 0, 0, 0), 0);
    }

    list($inputColor, $darkColor, $lightColor) = $args[2];

    $inputColor = $this->assertColor($inputColor);
    $darkColor = $this->assertColor($darkColor);
    $lightColor = $this->assertColor($lightColor);
    $hsl = $this->toHSL($inputColor);

    if ($hsl[3] > 50) {
      return $darkColor;
    }

    return $lightColor;
  }

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

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

  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 (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($key, self::$defaultValue));
      $seen[$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 $value;
    case "escape":
      list(,$inner) = $value;
      return $this->lib_e($this->reduce($inner));
    case "function":
      $color = $this->funcToColor($value);
      if ($color) return $color;

      list(, $name, $args) = $value;
      if ($name == "%") $name = "_sprintf";
      $f = isset($this->libFunctions[$name]) ?
        $this->libFunctions[$name] : array($this, 'lib_'.$name);

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

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

  // evaluate an expression
  protected function evaluate($exp) {
    list(, $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;
    }
  }


  // 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, $default=null) {
    $current = $this->env;

    $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];
      else {
        $current = isset($current->storeParent) ?
          $current->storeParent : $current->parent;
      }
    }

    return $default;
  }

  // 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->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->allParsedFiles = array();
    $this->addParsedFile($fname);

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

    $this->importDir = $oldImport;

    if ($outFname !== null) {
      return $this->put_contents($outFname, $out);
    }

    return $out;
  }

  // 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;
  }

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

  /**
   * Uses the current value of $this->count to show line and line number
   */
  protected function throwError($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");
  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();

  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
    $lastCount = $this->count;
    while (false !== $this->parseChunk());

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

    // TODO report where the block was opened
    if (!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();

    // 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;
          }
        }
      }

      $this->seek($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('{')) {
      $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) &&
      ($this->argumentValues($argv) || 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 ($this->string($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("~") && $this->string($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) {
    $s = $this->seek();
    if (!$this->literal('@import')) return false;

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

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

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

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

    $args = $values;
    return true;
  }

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

    $values = array();

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

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

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

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

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

    $args = $values;

    return true;
  }

  // consume a list of tags
  // this accepts a hanging delimiter
  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) {
    $s = $this->seek();
    $tags = array();
    while ($this->tag($tt, true)) {
      $tags[] = $tt;
      $this->literal(">");
    }

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

    return true;
  }

  // a bracketed value (contained within in a tag definition)
  protected function tagBracket(&$value) {
    // speed shortcut
    if (isset($this->buffer[$this->count]) && $this->buffer[$this->count] != "[") {
      return false;
    }

    $s = $this->seek();
    if ($this->literal('[') && $this->to(']', $c, true) && $this->literal(']', false)) {
      $value = '['.$c.']';
      // whitespace?
      if ($this->whitespace()) $value .= " ";

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

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

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

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

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

    $s = $this->seek();

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

    $hasExpression = false;
    $parts = array();
    while ($this->tagBracket($first)) $parts[] = $first;

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

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

        while ($this->tagBracket($brack)) {
          $parts[] = $brack;
        }
        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 ($this->literal(';')) {
      return true;
    } elseif ($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, null, $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, null, $this->count)) {
        if (isset($m[1]) && empty($this->commentsSeen[$this->count])) {
          $this->append(array("comment", $m[1]));
          $this->commentsSeen[$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, null, $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();

    $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 = ",";
}