<?php


namespace Nextend\Framework\Asset\Css\Less;

use Exception;
use stdClass;

class LessParser {

    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(
                    LessCompiler::class,
                    'preg_quote'
                ), array_keys(self::$precedence))) . ')';

            $commentSingle     = LessCompiler::preg_quote(self::$commentSingle);
            $commentMultiLeft  = LessCompiler::preg_quote(self::$commentMultiLeft);
            $commentMultiRight = LessCompiler::preg_quote(self::$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(
            LessCompiler::class,
            "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;

        $exps = LessCompiler::compressList($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[$this->count - 1]) && preg_match('/^\\s+$/', $this->buffer[$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[$this->count - 1]) && preg_match('/^\\s+$/', $this->buffer[$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;

        $value = LessCompiler::compressList($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(
            LessCompiler::class,
            "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)) {
                $ount = 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;
    }

    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
        $patt = '([^\n]*?)(@\{|\\\\|' . LessCompiler::preg_quote($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)) {
                    $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 (!preg_match('/^[0-9]+$/', $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] = LessCompiler::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('(' . $validChars . '*?)' . LessCompiler::preg_quote($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]` $loc<br>FILE: <strong>{$this->lessc->sourceParser->sourceName}</strong>");
        } else {
            throw new Exception("$msg: $loc<br>FILE: <strong>{$this->lessc->sourceParser->sourceName}</strong>");
        }
    }

    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;
    }


}