CSSJanus.php

Go to the documentation of this file.

<?php
class CSSJanus {
    // Patterns defined as null are built dynamically by buildPatterns()
    private static $patterns = array(
        'tmpToken' => '`TMP`',
        'nonAscii' => '[\200-\377]',
        'unicode' => '(?:(?:\\[0-9a-f]{1,6})(?:\r\n|\s)?)',
        'num' => '(?:[0-9]*\.[0-9]+|[0-9]+)',
        'unit' => '(?:em|ex|px|cm|mm|in|pt|pc|deg|rad|grad|ms|s|hz|khz|%)',
        'body_selector' => 'body\s*{\s*',
        'direction' => 'direction\s*:\s*',
        'escape' => null,
        'nmstart' => null,
        'nmchar' => null,
        'ident' => null,
        'quantity' => null,
        'possibly_negative_quantity' => null,
        'color' => null,
        'url_special_chars' => '[!#$%&*-~]',
        'valid_after_uri_chars' => '[\'\"]?\s*',
        'url_chars' => null,
        'lookahead_not_open_brace' => null,
        'lookahead_not_closing_paren' => null,
        'lookahead_for_closing_paren' => null,
        'lookahead_not_letter' => '(?![a-zA-Z])',
        'lookbehind_not_letter' => '(?<![a-zA-Z])',
        'chars_within_selector' => '[^\}]*?',
        'noflip_annotation' => '\/\*\s*@noflip\s*\*\/',
        'noflip_single' => null,
        'noflip_class' => null,
        'comment' => '/\/\*[^*]*\*+([^\/*][^*]*\*+)*\//',
        'direction_ltr' => null,
        'direction_rtl' => null,
        'left' => null,
        'right' => null,
        'left_in_url' => null,
        'right_in_url' => null,
        'ltr_in_url' => null,
        'rtl_in_url' => null,
        'cursor_east' => null,
        'cursor_west' => null,
        'four_notation_quantity' => null,
        'four_notation_color' => null,
        'border_radius' => null,
        'box_shadow' => null,
        'text_shadow1' => null,
        'text_shadow2' => null,
        'bg_horizontal_percentage' => null,
        'bg_horizontal_percentage_x' => null,
    );
 
    private static function buildPatterns() {
        if ( !is_null( self::$patterns['escape'] ) ) {
            // Patterns have already been built
            return;
        }
 
        $patterns =& self::$patterns;
        $patterns['escape'] = "(?:{$patterns['unicode']}|\\[^\r\n\f0-9a-f])";
        $patterns['nmstart'] = "(?:[_a-z]|{$patterns['nonAscii']}|{$patterns['escape']})";
        $patterns['nmchar'] = "(?:[_a-z0-9-]|{$patterns['nonAscii']}|{$patterns['escape']})";
        $patterns['ident'] = "-?{$patterns['nmstart']}{$patterns['nmchar']}*";
        $patterns['quantity'] = "{$patterns['num']}(?:\s*{$patterns['unit']}|{$patterns['ident']})?";
        $patterns['possibly_negative_quantity'] = "((?:-?{$patterns['quantity']})|(?:inherit|auto))";
        $patterns['color'] = "(#?{$patterns['nmchar']}+|(?:rgba?|hsla?)\([ \d.,%-]+\))";
        $patterns['url_chars'] = "(?:{$patterns['url_special_chars']}|{$patterns['nonAscii']}|{$patterns['escape']})*";
        $patterns['lookahead_not_open_brace'] = "(?!({$patterns['nmchar']}|\r?\n|\s|#|\:|\.|\,|\+|>|\(|\)|\[|\]|=|\*=|~=|\^=|'[^']*'])*?{)";
        $patterns['lookahead_not_closing_paren'] = "(?!{$patterns['url_chars']}?{$patterns['valid_after_uri_chars']}\))";
        $patterns['lookahead_for_closing_paren'] = "(?={$patterns['url_chars']}?{$patterns['valid_after_uri_chars']}\))";
        $patterns['noflip_single'] = "/({$patterns['noflip_annotation']}{$patterns['lookahead_not_open_brace']}[^;}]+;?)/i";
        $patterns['noflip_class'] = "/({$patterns['noflip_annotation']}{$patterns['chars_within_selector']}})/i";
        $patterns['direction_ltr'] = "/({$patterns['direction']})ltr/i";
        $patterns['direction_rtl'] = "/({$patterns['direction']})rtl/i";
        $patterns['left'] = "/{$patterns['lookbehind_not_letter']}(left){$patterns['lookahead_not_letter']}{$patterns['lookahead_not_closing_paren']}{$patterns['lookahead_not_open_brace']}/i";
        $patterns['right'] = "/{$patterns['lookbehind_not_letter']}(right){$patterns['lookahead_not_letter']}{$patterns['lookahead_not_closing_paren']}{$patterns['lookahead_not_open_brace']}/i";
        $patterns['left_in_url'] = "/{$patterns['lookbehind_not_letter']}(left){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['right_in_url'] = "/{$patterns['lookbehind_not_letter']}(right){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['ltr_in_url'] = "/{$patterns['lookbehind_not_letter']}(ltr){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['rtl_in_url'] = "/{$patterns['lookbehind_not_letter']}(rtl){$patterns['lookahead_for_closing_paren']}/i";
        $patterns['cursor_east'] = "/{$patterns['lookbehind_not_letter']}([ns]?)e-resize/";
        $patterns['cursor_west'] = "/{$patterns['lookbehind_not_letter']}([ns]?)w-resize/";
        $patterns['four_notation_quantity'] = "/(:\s*){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s*[;}])/i";
        $patterns['four_notation_color'] = "/(-color\s*:\s*){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}(\s*[;}])/i";
        $patterns['border_radius'] = "/(border-radius\s*:\s*){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s*[;}])/i";
        $patterns['box_shadow'] = "/(box-shadow\s*:\s*(?:inset\s*)?){$patterns['possibly_negative_quantity']}/i";
        $patterns['text_shadow1'] = "/(text-shadow\s*:\s*){$patterns['color']}(\s*){$patterns['possibly_negative_quantity']}/i";
        $patterns['text_shadow2'] = "/(text-shadow\s*:\s*){$patterns['possibly_negative_quantity']}/i";
        // The two regexes below are parenthesized differently then in the original implementation to make the
        // callback's job more straightforward
        $patterns['bg_horizontal_percentage'] = "/(background(?:-position)?\s*:\s*[^%]*?)(-?{$patterns['num']})(%\s*(?:{$patterns['quantity']}|{$patterns['ident']}))/";
        $patterns['bg_horizontal_percentage_x'] = "/(background-position-x\s*:\s*)(-?{$patterns['num']})(%)/";
    }
 
    public static function transform( $css, $swapLtrRtlInURL = false, $swapLeftRightInURL = false ) {
        // We wrap tokens in ` , not ~ like the original implementation does.
        // This was done because ` is not a legal character in CSS and can only
        // occur in URLs, where we escape it to %60 before inserting our tokens.
        $css = str_replace( '`', '%60', $css );
 
        self::buildPatterns();
 
        // Tokenize single line rules with /* @noflip */
        $noFlipSingle = new CSSJanus_Tokenizer( self::$patterns['noflip_single'], '`NOFLIP_SINGLE`' );
        $css = $noFlipSingle->tokenize( $css );
 
        // Tokenize class rules with /* @noflip */
        $noFlipClass = new CSSJanus_Tokenizer( self::$patterns['noflip_class'], '`NOFLIP_CLASS`' );
        $css = $noFlipClass->tokenize( $css );
 
        // Tokenize comments
        $comments = new CSSJanus_Tokenizer( self::$patterns['comment'], '`C`' );
        $css = $comments->tokenize( $css );
 
        // LTR->RTL fixes start here
        $css = self::fixDirection( $css );
        if ( $swapLtrRtlInURL ) {
            $css = self::fixLtrRtlInURL( $css );
        }
 
        if ( $swapLeftRightInURL ) {
            $css = self::fixLeftRightInURL( $css );
        }
        $css = self::fixLeftAndRight( $css );
        $css = self::fixCursorProperties( $css );
        $css = self::fixFourPartNotation( $css );
        $css = self::fixBorderRadius( $css );
        $css = self::fixBackgroundPosition( $css );
        $css = self::fixShadows( $css );
 
        // Detokenize stuff we tokenized before
        $css = $comments->detokenize( $css );
        $css = $noFlipClass->detokenize( $css );
        $css = $noFlipSingle->detokenize( $css );
 
        return $css;
    }
 
    private static function fixDirection( $css ) {
        $css = preg_replace( self::$patterns['direction_ltr'],
            '$1' . self::$patterns['tmpToken'], $css );
        $css = preg_replace( self::$patterns['direction_rtl'], '$1ltr', $css );
        $css = str_replace( self::$patterns['tmpToken'], 'rtl', $css );
 
        return $css;
    }
 
    private static function fixLtrRtlInURL( $css ) {
        $css = preg_replace( self::$patterns['ltr_in_url'], self::$patterns['tmpToken'], $css );
        $css = preg_replace( self::$patterns['rtl_in_url'], 'ltr', $css );
        $css = str_replace( self::$patterns['tmpToken'], 'rtl', $css );
 
        return $css;
    }
 
    private static function fixLeftRightInURL( $css ) {
        $css = preg_replace( self::$patterns['left_in_url'], self::$patterns['tmpToken'], $css );
        $css = preg_replace( self::$patterns['right_in_url'], 'left', $css );
        $css = str_replace( self::$patterns['tmpToken'], 'right', $css );
 
        return $css;
    }
 
    private static function fixLeftAndRight( $css ) {
        $css = preg_replace( self::$patterns['left'], self::$patterns['tmpToken'], $css );
        $css = preg_replace( self::$patterns['right'], 'left', $css );
        $css = str_replace( self::$patterns['tmpToken'], 'right', $css );
 
        return $css;
    }
 
    private static function fixCursorProperties( $css ) {
        $css = preg_replace( self::$patterns['cursor_east'],
            '$1' . self::$patterns['tmpToken'], $css );
        $css = preg_replace( self::$patterns['cursor_west'], '$1e-resize', $css );
        $css = str_replace( self::$patterns['tmpToken'], 'w-resize', $css );
 
        return $css;
    }
 
    private static function fixFourPartNotation( $css ) {
        $css = preg_replace( self::$patterns['four_notation_quantity'], '$1$2$3$8$5$6$7$4$9', $css );
        $css = preg_replace( self::$patterns['four_notation_color'], '$1$2$3$8$5$6$7$4$9', $css );
        return $css;
    }
 
    private static function fixBorderRadius( $css ) {
        // Undo four_notation_quantity
        $css = preg_replace( self::$patterns['border_radius'], '$1$2$3$8$5$6$7$4$9', $css );
        // Do the real thing
        $css = preg_replace( self::$patterns['border_radius'], '$1$4$3$2$5$8$7$6$9', $css );
 
        return $css;
    }
 
    private static function fixShadows( $css ) {
        // Flips the sign of a CSS value, possibly with a unit.
        // (We can't just negate the value with unary minus due to the units.)
        $flipSign = function ( $cssValue ) {
            // Don't mangle zeroes
            if ( intval( $cssValue ) === 0 ) {
                return $cssValue;
            } elseif ( $cssValue[0] === '-' ) {
                return substr( $cssValue, 1 );
            } else {
                return "-" . $cssValue;
            }
        };
 
        $css = preg_replace_callback( self::$patterns['box_shadow'], function ( $matches ) use ( $flipSign ) {
            return $matches[1] . $flipSign( $matches[2] );
        }, $css );
 
        $css = preg_replace_callback( self::$patterns['text_shadow1'], function ( $matches ) use ( $flipSign ) {
            return $matches[1] . $matches[2] . $matches[3] . $flipSign( $matches[4] );
        }, $css );
 
        $css = preg_replace_callback( self::$patterns['text_shadow2'], function ( $matches ) use ( $flipSign ) {
            return $matches[1] . $flipSign( $matches[2] );
        }, $css );
 
        return $css;
    }
 
    private static function fixBackgroundPosition( $css ) {
        $replaced = preg_replace_callback( self::$patterns['bg_horizontal_percentage'],
            array( 'self', 'calculateNewBackgroundPosition' ), $css );
        if ( $replaced !== null ) {
            // Check for null; sometimes preg_replace_callback() returns null here for some weird reason
            $css = $replaced;
        }
        $replaced = preg_replace_callback( self::$patterns['bg_horizontal_percentage_x'],
            array( 'self', 'calculateNewBackgroundPosition' ), $css );
        if ( $replaced !== null ) {
            $css = $replaced;
        }
 
        return $css;
    }
 
    private static function calculateNewBackgroundPosition( $matches ) {
        return $matches[1] . ( 100 - $matches[2] ) . $matches[3];
    }
}
 
class CSSJanus_Tokenizer {
    private $regex, $token;
    private $originals;
 
    public function __construct( $regex, $token ) {
        $this->regex = $regex;
        $this->token = $token;
        $this->originals = array();
    }
 
    public function tokenize( $str ) {
        return preg_replace_callback( $this->regex, array( $this, 'tokenizeCallback' ), $str );
    }
 
    private function tokenizeCallback( $matches ) {
        $this->originals[] = $matches[0];
        return $this->token;
    }
 
    public function detokenize( $str ) {
        // PHP has no function to replace only the first occurrence or to
        // replace occurrences of the same string with different values,
        // so we use preg_replace_callback() even though we don't really need a regex
        return preg_replace_callback( '/' . preg_quote( $this->token, '/' ) . '/',
            array( $this, 'detokenizeCallback' ), $str );
    }
 
    private function detokenizeCallback( $matches ) {
        $retval = current( $this->originals );
        next( $this->originals );
 
        return $retval;
    }
}