<?php
/**
 * @package   FOF
 * @copyright Copyright (c)2010-2020 Nicholas K. Dionysopoulos / Akeeba Ltd
 * @license   GNU General Public License version 2, or later
 */

namespace FOF30\Less\Parser;

use FOF30\Less\Less;
use Exception;

defined('_JEXEC') or die;

/**
 * This class is taken verbatim from:
 *
 * 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
 *
 * Responsible for taking a string of LESS code and converting it into a syntax tree
 *
 * @since  2.0
 */
class Parser
{
	// Used to uniquely identify blocks
	protected static $nextBlockId = 0;

	protected static $precedence = array(
		'=<'					 => 0,
		'>='					 => 0,
		'='						 => 0,
		'<'						 => 0,
		'>'						 => 0,
		'+'						 => 1,
		'-'						 => 1,
		'*'						 => 2,
		'/'						 => 2,
		'%'						 => 2,
	);

	protected static $whitePattern;

	protected static $commentMulti;

	protected static $commentSingle = "//";

	protected static $commentMultiLeft = "/*";

	protected static $commentMultiRight = "*/";

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

	// These properties will supress division unless it's inside parenthases
	protected static $supressDivisionProps = array('/border-radius$/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 resolve to a single value and thus is less
	 * ambiguous.
	 *
	 * Consider:
	 *     property1: 10 -5; // is two numbers, 10 and -5
	 *     property2: (10 -5); // should resolve to 5
	 */
	protected $inParens = false;

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

	/**
	 * Constructor
	 *
	 * @param   [type]  $lessc       [description]
	 * @param   string  $sourceName  [description]
	 */
	public function __construct($lessc, $sourceName = null)
	{
		$this->eatWhiteDefault = true;

		// Reference to less needed for vPrefix, mPrefix, and parentSelector
		$this->lessc = $lessc;

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

		$this->writeComments = false;

		if (!self::$operatorString)
		{
			self::$operatorString = '(' . implode('|', array_map(array('\\FOF30\\Less\\Less', 'preg_quote'), array_keys(self::$precedence))) . ')';

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

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

	/**
	 * Parse text
	 *
	 * @param   string  $buffer  [description]
	 *
	 * @return  [type]           [description]
	 */
	public function parse($buffer)
	{
		$this->count = 0;
		$this->line = 1;

		// Block stack
		$this->env = null;
		$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.
	 *
	 * @return  boolean
	 */
	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;
		}

		// Got nothing, throw error
		return false;
	}

	/**
	 * [isDirective description]
	 *
	 * @param   string  $dirname     [description]
	 * @param   [type]  $directives  [description]
	 *
	 * @return  boolean
	 */
	protected function isDirective($dirname, $directives)
	{
		// TODO: cache pattern in parser
		$pattern = implode("|", array_map(array("\\FOF30\\Less\\Less", "preg_quote"), $directives));
		$pattern = '/^(-[a-z-]+-)?(' . $pattern . ')$/i';

		return preg_match($pattern, $dirname);
	}

	/**
	 * [fixTags description]
	 *
	 * @param   [type]  $tags  [description]
	 *
	 * @return  [type]         [description]
	 */
	protected function fixTags($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
	 *
	 * @param   [type]  &$exps  [description]
	 *
	 * @return  boolean
	 */
	protected function expressionList(&$exps)
	{
		$values = array();

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

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

		$exps = Less::compressList($values, ' ');

		return true;
	}

	/**
	 * Attempt to consume an expression.
	 *
	 * @param   string  &$out  [description]
	 *
	 * @link http://en.wikipedia.org/wiki/Operator-precedence_parser#Pseudo-code
	 *
	 * @return  boolean
	 */
	protected function expression(&$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
	 *
	 * @param   type  $lhs   [description]
	 * @param   type  $minP  [description]
	 *
	 * @return   string
	 */
	protected function expHelper($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
	 *
	 * @param   [type]  &$value   [description]
	 * @param   [type]  $keyName  [description]
	 *
	 * @return  boolean
	 */
	public function propertyValue(&$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;
		}

		$value = Less::compressList($values, ', ');

		return true;
	}

	/**
	 * [parenValue description]
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  boolean
	 */
	protected function parenValue(&$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
	 *
	 * @param   [type]  &$value  [description]
	 *
	 * @return  boolean
	 */
	protected function value(&$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
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  boolean
	 */
	protected function import(&$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;
		}
	}

	/**
	 * [mediaQueryList description]
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  boolean
	 */
	protected function mediaQueryList(&$out)
	{
		if ($this->genericList($list, "mediaQuery", ",", false))
		{
			$out = $list[2];

			return true;
		}

		return false;
	}

	/**
	 * [mediaQuery description]
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  [type]        [description]
	 */
	protected function mediaQuery(&$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;
	}

	/**
	 * [mediaExpression description]
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  boolean
	 */
	protected function mediaExpression(&$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
	 *
	 * @param   [type]  $end          [description]
	 * @param   [type]  &$out         [description]
	 * @param   [type]  $nestingOpen  [description]
	 * @param   [type]  $rejectStrs   [description]
	 *
	 * @return  boolean
	 */
	protected function openString($end, &$out, $nestingOpen = null, $rejectStrs = null)
	{
		$oldWhite = $this->eatWhiteDefault;
		$this->eatWhiteDefault = false;

		$stop = array("'", '"', "@{", $end);
		$stop = array_map(array("\\FOF30\\Less\\Less", "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 (in_array($tok, $rejectStrs))
			{
				$count = null;
				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;
	}

	/**
	 * [string description]
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  boolean
	 */
	protected function string(&$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
		$patt = '([^\n]*?)(@\{|\\\\|' . Less::preg_quote($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]);

					// Ignore it
					$content[] = "@{";
				}
			}
			elseif ($m[2] == '\\')
			{
				$content[] = $m[2];

				if ($this->literal($delim, false))
				{
					$content[] = $delim;
				}
			}
			else
			{
				$this->count -= strlen($delim);

				// Delim
				break;
			}
		}

		$this->eatWhiteDefault = $oldWhite;

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

			return true;
		}

		$this->seek($s);

		return false;
	}

	/**
	 * [interpolation description]
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  boolean
	 */
	protected function interpolation(&$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;
	}

	/**
	 * [unit description]
	 *
	 * @param   [type]  &$unit  [description]
	 *
	 * @return  boolean
	 */
	protected function unit(&$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
	 *
	 * @param   [type]  &$out  [description]
	 *
	 * @return  boolean
	 */
	protected function color(&$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 ()
	 *
	 * @param   [type]  &$args  [description]
	 * @param   [type]  $delim  [description]
	 *
	 * @return  boolean
	 */
	protected function argumentValues(&$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 ...
	 *
	 * @param   [type]  &$args      [description]
	 * @param   [type]  &$isVararg  [description]
	 * @param   [type]  $delim      [description]
	 *
	 * @return  boolean
	 */
	protected function argumentDef(&$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
	 *
	 * @param   [type]  &$tags   [description]
	 * @param   [type]  $simple  [description]
	 * @param   [type]  $delim   [description]
	 *
	 * @return  boolean
	 */
	protected function tags(&$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 >)
	 *
	 * @param   [type]  &$tags  [description]
	 *
	 * @return  boolean
	 */
	protected function mixinTags(&$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)
	 *
	 * @param   [type]  &$value  [description]
	 *
	 * @return  boolean
	 */
	protected function tagBracket(&$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;
	}

	/**
	 * [tagExpression description]
	 *
	 * @param   [type]  &$value  [description]
	 *
	 * @return  boolean
	 */
	protected function tagExpression(&$value)
	{
		$s = $this->seek();

		if ($this->literal("(") && $this->expression($exp) && $this->literal(")"))
		{
			$value = array('exp', $exp);

			return true;
		}

		$this->seek($s);

		return false;
	}

	/**
	 * A single tag
	 *
	 * @param   [type]   &$tag    [description]
	 * @param   boolean  $simple  [description]
	 *
	 * @return  boolean
	 */
	protected function tag(&$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;

					// Don't unescape
					$interp[2] = true;
					$parts[] = $interp;

					continue;
				}

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

					continue;
				}
			}

			// For keyframes
			if ($this->unit($unit))
			{
				$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
	 *
	 * @param   [type]  &$func  [description]
	 *
	 * @return  boolean
	 */
	protected function func(&$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
	 *
	 * @param   [type]  &$name  [description]
	 *
	 * @return  boolean
	 */
	protected function variable(&$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
	 *
	 * @param   string  $name  [description]
	 *
	 * @return  boolean
	 */
	protected function assign($name = null)
	{
		if ($name)
		{
			$this->currentProperty = $name;
		}

		return $this->literal(':') || $this->literal('=');
	}

	/**
	 * Consume a keyword
	 *
	 * @param   [type]  &$word  [description]
	 *
	 * @return  boolean
	 */
	protected function keyword(&$word)
	{
		if ($this->match('([\w_\-\*!"][\w\-_"]*)', $m))
		{
			$word = $m[1];

			return true;
		}

		return false;
	}

	/**
	 * Consume an end of statement delimiter
	 *
	 * @return  boolean
	 */
	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;
	}

	/**
	 * [guards description]
	 *
	 * @param   [type]  &$guards  [description]
	 *
	 * @return  boolean
	 */
	protected function guards(&$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
	 *
	 * @param   [type]  &$guardGroup  [description]
	 *
	 * @todo rename to guardGroup
	 *
	 * @return  boolean
	 */
	protected function guardGroup(&$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;
	}

	/**
	 * [guard description]
	 *
	 * @param   [type]  &$guard  [description]
	 *
	 * @return  boolean
	 */
	protected function guard(&$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 */

	/**
	 * [literal description]
	 *
	 * @param   [type]  $what           [description]
	 * @param   [type]  $eatWhitespace  [description]
	 *
	 * @return  boolean
	 */
	protected function literal($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;
				}
			}
			else
			{
				return false;
			}
		}

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

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

	/**
	 * [genericList description]
	 *
	 * @param   [type]   &$out       [description]
	 * @param   [type]   $parseItem  [description]
	 * @param   string   $delim      [description]
	 * @param   boolean  $flatten    [description]
	 *
	 * @return  boolean
	 */
	protected function genericList(&$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
	 *
	 * @param   [type]   $what          [description]
	 * @param   [type]   &$out          [description]
	 * @param   boolean  $until         [description]
	 * @param   boolean  $allowNewline  [description]
	 *
	 * @return  boolean
	 */
	protected function to($what, &$out, $until = false, $allowNewline = false)
	{
		if (is_string($allowNewline))
		{
			$validChars = $allowNewline;
		}
		else
		{
			$validChars = $allowNewline ? "." : "[^\n]";
		}

		if (!$this->match('(' . $validChars . '*?)' . Less::preg_quote($what), $m, !$until))
		{
			return false;
		}

		if ($until)
		{
			// Give back $what
			$this->count -= strlen($what);
		}

		$out = $m[1];

		return true;
	}

	/**
	 * Try to match something on head of buffer
	 *
	 * @param   [type]  $regex          [description]
	 * @param   [type]  &$out           [description]
	 * @param   [type]  $eatWhitespace  [description]
	 *
	 * @return  boolean
	 */
	protected function match($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;
	}

	/**
	 * Watch some whitespace
	 *
	 * @return  boolean
	 */
	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
	 *
	 * @param   [type]  $regex  [description]
	 * @param   [type]  &$out   [description]
	 * @param   [type]  $from   [description]
	 *
	 * @return  boolean
	 */
	protected function peek($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
	 *
	 * @param   [type]  $where  [description]
	 *
	 * @return  boolean
	 */
	protected function seek($where = null)
	{
		if ($where === null)
		{
			return $this->count;
		}
		else
		{
			$this->count = $where;
		}

		return true;
	}

	/* misc functions */

	/**
	 * [throwError description]
	 *
	 * @param   string  $msg    [description]
	 * @param   [type]  $count  [description]
	 *
	 * @return  void
	 */
	public function throwError($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");
		}
	}

	/**
	 * [pushBlock description]
	 *
	 * @param   [type]  $selectors  [description]
	 * @param   [type]  $type       [description]
	 *
	 * @return  \stdClass
	 */
	protected function pushBlock($selectors = null, $type = null)
	{
		$b = new \stdClass;
		$b->parent = $this->env;

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

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

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

		$this->env = $b;

		return $b;
	}

	/**
	 * Push a block that doesn't multiply tags
	 *
	 * @param   [type]  $type  [description]
	 *
	 * @return  \stdClass
	 */
	protected function pushSpecialBlock($type)
	{
		return $this->pushBlock(null, $type);
	}

	/**
	 * Append a property to the current block
	 *
	 * @param   [type]  $prop  [description]
	 * @param   [type]  $pos   [description]
	 *
	 * @return  void
	 */
	protected function append($prop, $pos = null)
	{
		if ($pos !== null)
		{
			$prop[-1] = $pos;
		}

		$this->env->props[] = $prop;
	}

	/**
	 * Pop something off the stack
	 *
	 * @return  [type]  [description]
	 */
	protected function pop()
	{
		$old = $this->env;
		$this->env = $this->env->parent;

		return $old;
	}

	/**
	 * Remove comments from $text
	 *
	 * @param   [type]  $text  [description]
	 *
	 * @todo: make it work for all functions, not just url
	 *
	 * @return  [type]         [description]
	 */
	protected function removeComments($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;
	}
}
