MarcusSchwarz / lesserphp

src/LesserPhp/Parser.php

<?php

namespace LesserPhp;

use LesserPhp\Exception\GeneralException;

/**
 * lesserphp
 * https://www.maswaba.de/lesserphp
 *
 * LESS CSS compiler, adapted from http://lesscss.org
 *
 * Copyright 2013, Leaf Corcoran <leafot@gmail.com>
 * Copyright 2016, Marcus Schwarz <github@maswaba.de>
 * Licensed under MIT or GPLv3, see LICENSE
 * @package LesserPhp
 * // responsible for taking a string of LESS code and converting it into a
 * // syntax tree
 */
class Parser
{

    static protected $nextBlockId = 0; // used to uniquely identify blocks

    static protected $precedence = [
        '=<' => 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 $supressDivisionProps =
        ['/border-radius$/i', '/^font$/i'];

    protected $blockDirectives = [
        'font-face',
        'keyframes',
        'page',
        '-moz-document',
        'viewport',
        '-moz-viewport',
        '-o-viewport',
        '-ms-viewport',
    ];
    protected $lineDirectives = ['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 = [];
    /** @var int */
    public $count;
    /** @var int */
    private $line;
    /** @var array */
    private $seenComments;
    /** @var string */
    public $buffer;

    private $env;
    /** @var bool */
    private $inExp;
    /** @var string */
    private $currentProperty;

    /**
     * @var bool
     */
    private $writeComments = false;

    /**
     * Parser constructor.
     *
     * @param \LesserPhp\Compiler $lessc
     * @param null                $sourceName
     */
    public function __construct(Compiler $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

        if (!self::$operatorString) {
            self::$operatorString =
                '(' . implode('|', array_map(['\LesserPhp\Compiler', 'pregQuote'],
                    array_keys(self::$precedence))) . ')';

            $commentSingle = \LesserPhp\Compiler::pregQuote(self::$commentSingle);
            $commentMultiLeft = \LesserPhp\Compiler::pregQuote(self::$commentMultiLeft);
            $commentMultiRight = \LesserPhp\Compiler::pregQuote(self::$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 = [];

        $this->whitespace();

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

        if ($this->count !== strlen($this->buffer)) {
//            var_dump($this->count);

59% of this comment could be valid code. Did you maybe forget this after debugging?

//            var_dump($this->buffer);
            $this->throwError();
        }

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

        return $this->env;
    }

    /**
     * Parse a single chunk off the head of the buffer and append it to the
     * current parse environment.
     * Returns false when the buffer is empty, or when there is an error.
     *
     * This function is called repeatedly until the entire document is
     * parsed.
     *
     * This parser is most similar to a recursive descent parser. Single
     * functions represent discrete grammatical rules for the language, and
     * they are able to capture the text that represents those rules.
     *
     * Consider the function \LesserPhp\Compiler::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 \LesserPhp\Compiler::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, \LesserPhp\Compiler::seek() is used to remember and set buffer positions.
     *
     * Before parsing a chain, use $s = $this->seek() to remember the current
     * position into $s. Then if a chain fails, use $this->seek($s) to
     * go back where we started.
     */
    protected function parseChunk()
    {
        if (empty($this->buffer)) {
            return false;
        }
        $s = $this->seek();

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

        // setting a property
        if ($this->keyword($key) && $this->assign() &&
            $this->propertyValue($value, $key) && $this->end()
        ) {
            $this->append(['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 = $mediaQueries === null ? [] : $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, [";"]) || 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(["directive", $dirName, $dirValue]);

                        return true;
                    }
                } elseif ($this->literal(":", true)) {
                    //Ruleset Definition
                    if (($this->openString("{", $dirValue, null, [";"]) || true) &&
                        $this->literal("{")
                    ) {
                        $dir = $this->pushBlock($this->fixTags(["@" . $dirName]));
                        $dir->name = $dirName;
                        if (isset($dirValue)) {
                            $dir->value = $dirValue;
                        }

                        return true;
                    }
                }
            }

            $this->seek($s);
        }


        if ($this->literal('&', false)) {
            $this->count--;
            if ($this->literal('&:extend')) {

This if statement is empty and can be removed.

                // hierauf folgt was in runden klammern, und zwar das element, das erweitert werden soll
                // heißt also, das was in klammern steht wird um die aktuellen klassen erweitert
                /*
Aus

nav ul {
  &:extend(.inline);
  background: blue;
}
.inline {
  color: red;
}


Wird:

nav ul {
  background: blue;
}
.inline,
nav ul {
  color: red;
}

                 */
//                echo "Here we go";
            }
        }


        // setting a variable
        if ($this->variable($var) && $this->assign() &&
            $this->propertyValue($value) && $this->end()
        ) {
            $this->append(['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([$tag]));
            $block->args = $args;
            $block->isVararg = $isVararg;
            if (!empty($guards)) {
                $block->guards = $guards;
            }

            return true;
        } else {
            $this->seek($s);
        }

        // opening a simple block
        if ($this->tags($tags) && $this->literal('{', false)) {
            $tags = $this->fixTags($tags);
            $this->pushBlock($tags);

            return true;
        } else {
            $this->seek($s);
        }

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

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

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

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

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

            return true;
        }

        // mixin
        if ($this->mixinTags($tags) &&
            ($this->argumentDef($argv, $isVararg) || true) &&
            ($this->keyword($suffix) || true) && $this->end()
        ) {
            $tags = $this->fixTags($tags);
            $this->append(['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(['\LesserPhp\Compiler', "pregQuote"], $directives));
        $pattern = '/^(-[a-z-]+-)?(' . $pattern . ')$/i';

        return preg_match($pattern, $dirname);
    }

    /**
     * @param array $tags
     *
     * @return mixed
     */
    protected function fixTags(array $tags)
    {
        // move @ tags out of variable namespace
        foreach ($tags as &$tag) {
            if ($tag[0] === $this->lessc->getVPrefix()) {
                $tag[0] = $this->lessc->getMPrefix();
            }
        }

        return $tags;
    }

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

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

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

        $exps = \LesserPhp\Compiler::compressList($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)) {
                    $out = [
                        "list",
                        "",
                        [$out, ["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 = ['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 = [];

        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;
        }

        $value = \LesserPhp\Compiler::compressList($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 = ["variable", $inner]) ||
                    $this->unit($inner) ||
                    $this->parenValue($inner))
            ) {
                $value = ["unary", "-", $inner];

                return true;
            } else {
                $this->seek($s);
            }
        }

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

        if ($this->keyword($word)) {
            $value = ['keyword', $word];

            return true;
        }

        // try a variable
        if ($this->variable($var)) {
            $value = ['variable', $var];

            return true;
        }

        // unquote string (should this work on any type?
        if ($this->literal("~") && $this->stringValue($str)) {
            $value = ["escape", $str];

            return true;
        } else {
            $this->seek($s);
        }

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

            return true;
        } else {
            $this->seek($s);
        }

        return false;
    }

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

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

40% of this comment could be valid code. Did you maybe forget this after debugging?

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

        if ($this->propertyValue($value)) {
            $out = ["import", $value];

            return true;
        }

        return null;
    }

    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 = [];

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


        if (!empty($mediaType) && !$this->literal("and")) {

This if statement is empty and can be removed.

            // ~
        } 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 = ["mediaExp", $feature];
            if ($value) {
                $out[] = $value;
            }

            return true;
        } elseif ($this->variable($variable)) {
            $out = ['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 = ["'", '"', "@{", $end];
        $stop = array_map(['\LesserPhp\Compiler', "pregQuote"], $stop);
        // $stop[] = self::$commentMulti;

64% of this comment could be valid code. Did you maybe forget this after debugging?

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

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

        $nestingLevel = 0;

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

            $tok = $m[2];

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

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

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

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

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

        $this->eatWhiteDefault = $oldWhite;

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

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

        $out = ["string", "", $content];

        return true;
    }

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

        $content = [];

        // look for either ending delim , escape, or string interpolation
        $patt = '([^\n]*?)(@\{|\\\\|' .
            \LesserPhp\Compiler::pregQuote($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 = ["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, ["'", '"', ";"]) &&
            $this->literal("}", false)
        ) {
            $out = ["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 = ["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) {
                $out = ["string", "", [$m[1]]];
            } else {
                $out = ["raw_color", $m[1]];
            }

            return true;
        }

        return false;
    }

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

        $values = [];
        $delim = ",";
        $method = "expressionList";

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

            if ($this->$method($value)) {

The variable $value does not exist. Did you mean $values?

                if ($value[0] === "variable") {

The variable $value does not exist. Did you mean $values?

                    $arg = ["arg", $value[1]];

The variable $value does not exist. Did you mean $values?

                    $ss = $this->seek();

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

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

The variable $value does not exist. Did you mean $values?

                }
            }


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

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

                        $newList = ["list", ", ", $newList];

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

                    } elseif ($values) { // 1 item

The expression $values of type null[] is implicitly converted to a boolean; are you sure this is intended? If so, consider using ! empty($expr) instead to make it clear that you intend to check for an array without elements.

                        $newArg = $values[0];
                    }

                    if ($newArg !== null) {
                        $values = [$newArg];
                    }
                } else {
                    break;
                }
            }
        }

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

            return false;
        }

        $args = $values;

        return true;
    }

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

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

        return count($tags) !== 0;
    }

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

        $s = $this->seek();

        $hasInterpolation = false;

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

                if ($this->match('\s+', $m)) {
                    $attrParts[] = " ";
                    continue;
                }
                if ($this->stringValue($str)) {
                    // escape parent selector, (yuck)

37% of this comment could be valid code. Did you maybe forget this after debugging?

                    foreach ($str[2] as &$chunk) {
                        $chunk = str_replace($this->lessc->getParentSelector(), '$&$', $chunk);
                    }

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

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

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

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

                break;
            }

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

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

        $this->seek($s);

        return false;
    }

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

        $s = $this->seek();

        $hasExpression = false;
        $parts = [];
        while ($this->tagBracket($parts, $hasExpression)) {
            ;
        }

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

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

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

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

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

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

            break;
        }

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

            return false;
        }

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

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

            if ($this->literal(')')) {
                $func = ['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 = ['function', $fname, $string];

                    return true;
                }
            }
        }

        $this->seek($s);

        return false;
    }

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

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

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

            return true;
        }

        return false;
    }

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

        return false;
    }

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

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

            return false;
        }

        $guards = [];

        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
    protected function guardGroup(&$guardGroup)
    {
        $s = $this->seek();
        $guardGroup = [];
        while ($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 = ["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] = \LesserPhp\Compiler::pregQuote($what);
        }

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

    protected function genericList(&$out, $parseItem, $delim = "", $flatten = true)
    {
        $s = $this->seek();
        $items = [];
        while ($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 = ["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('(' . $validChars . '*?)' . \LesserPhp\Compiler::pregQuote($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($this->seenComments[$this->count])) {
                    $this->append(["comment", $m[1]]);
                    $this->seenComments[$this->count] = true;
                }
                $this->count += strlen($m[0]);
                $gotWhite = true;
            }

            return $gotWhite;
        } else {
            $this->match("", $m);

            return strlen($m[0]) > 0;
        }
    }

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

    // 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 = $count === null ? $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, $count)) {
            throw new GeneralException("$msg: failed at `$m[1]` $loc");
        } else {
            throw new GeneralException("$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 = [];
        $b->children = [];

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

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

        $this->env = $b;

        return $b;
    }

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

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

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

        return $old;
    }

    // remove comments from $text
    // todo: make it work for all functions, not just url
    protected function removeComments($text)
    {
        $look = [
            '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]) {
                        $min = [$token, $pos];
                    }
                }
            }

            if ($min === null) {
                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;
    }

    /**
     * @param bool $writeComments
     */
    public function setWriteComments($writeComments)
    {
        $this->writeComments = $writeComments;
    }
}