CSSJanus.php

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<?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,
                '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']}+)";
                $patterns['url_chars'] = "(?:{$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/";
                $patterns['four_notation_quantity'] = "/{$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}(\s+){$patterns['possibly_negative_quantity']}/i";
                $patterns['four_notation_color'] = "/(-color\s*:\s*){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}/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::fixBackgroundPosition( $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$7$4$5$6$3', $css );
                $css = preg_replace( self::$patterns['four_notation_color'], '$1$2$3$8$5$6$7$4', $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;
        }
}