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CSSJanus.php
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CSSJanus.php
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<?php
/**
* PHP port of CSSJanus. https://www.mediawiki.org/wiki/CSSJanus
*
* Copyright 2020 Timo Tijhof
* Copyright 2014 Trevor Parscal
* Copyright 2010 Roan Kattouw
* Copyright 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* @file
*/
/**
* CSSJanus is a utility that converts CSS stylesheets
* from left-to-right (LTR) to right-to-left (RTL).
*/
class CSSJanus {
private const TOKEN_TMP = '`TMP`';
private const TOKEN_LTR_TMP = '`TMPLTR`';
private const TOKEN_RTL_TMP = '`TMPRTL`';
private const TOKEN_COMMENT = '`COMMENT`';
private static $patterns = null;
private static function buildPatterns() {
if ( self::$patterns !== null ) {
return;
}
// Patterns defined as null are built dynamically
$patterns = [
'nonAscii' => '[\200-\377]',
'unicode' => '(?:(?:\\\\[0-9a-f]{1,6})(?:\r\n|\s)?)',
'num' => '(?:[0-9]*\.[0-9]+|[0-9]+)',
'unit' => '(?:em|ex|px|cm|mm|in|pt|pc|deg|rad|grad|ms|s|hz|khz|%)',
'body_selector' => 'body\s*{\s*',
'direction' => 'direction\s*:\s*',
'escape' => null,
'nmstart' => null,
'nmchar' => null,
'ident' => null,
'quantity' => null,
'possibly_negative_quantity' => null,
'color' => null,
'url_special_chars' => '[!#$%&*-~]',
'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_dir_selector' => '/(:dir\( *)ltr( *\))/',
'rtl_dir_selector' => '/(:dir\( *)rtl( *\))/',
'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,
'suffix' => '(\s*(?:!important\s*)?[;}])'
];
// @codingStandardsIgnoreStart Generic.Files.LineLength.TooLong
$patterns['escape'] = "(?:{$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))";
$patterns['possibly_negative_simple_quantity'] = "(?:-?{$patterns['num']}(?:\s*{$patterns['unit']})?)";
$patterns['math_operator'] = '(?:\+|\-|\*|\/)';
$patterns['allowed_chars'] = '(?:\(|\)|\t| )';
$patterns['calc_equation'] = "(?:{$patterns['allowed_chars']}|{$patterns['possibly_negative_simple_quantity']}|{$patterns['math_operator']}){3,}";
$patterns['calc'] = "(?:calc\((?:{$patterns['calc_equation']})\))";
$patterns['possibly_negative_quantity_calc'] = "((?:-?{$patterns['quantity']})|(?:inherit|auto)|{$patterns['calc']})";
$patterns['color'] = "(#?{$patterns['nmchar']}+|(?:rgba?|hsla?)\([ \d.,%-]+\))";
// Use "*+" instead of "*?" to avoid reaching the backtracking limit.
// <https://phabricator.wikimedia.org/T326481>, <https://phabricator.wikimedia.org/T215746#4944830>.
$patterns['url_chars'] = "(?:{$patterns['url_special_chars']}|{$patterns['nonAscii']}|{$patterns['escape']})*+";
$patterns['lookahead_not_open_brace'] = "(?!({$patterns['nmchar']}|\\r?\\n|\s|#|\:|\.|\,|\+|>|~|\(|\)|\[|\]|=|\*=|~=|\^=|'[^']*'|\"[^\"]*\"|" . self::TOKEN_COMMENT . ")*+{)";
$patterns['lookahead_not_closing_paren'] = "(?!{$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_props'] = "((?:margin|padding|border-width)\s*:\s*)";
$patterns['four_notation_quantity'] = "/{$patterns['four_notation_quantity_props']}{$patterns['possibly_negative_quantity_calc']}(\s+){$patterns['possibly_negative_quantity_calc']}(\s+){$patterns['possibly_negative_quantity_calc']}(\s+){$patterns['possibly_negative_quantity_calc']}{$patterns['suffix']}/i";
$patterns['four_notation_color'] = "/((?:-color|border-style)\s*:\s*){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}(\s+){$patterns['color']}{$patterns['suffix']}/i";
// border-radius: <length or percentage>{1,4} [optional: / <length or percentage>{1,4} ]
$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*\/\s*)' . $patterns['possibly_negative_quantity'] . ')(?:\s+' . $patterns['possibly_negative_quantity'] . ')?(?:\s+' . $patterns['possibly_negative_quantity'] . ')?(?:\s+' . $patterns['possibly_negative_quantity'] . ')?)?' . $patterns['suffix']
. '/i';
$patterns['box_shadow'] = "/(box-shadow\s*:\s*(?:inset\s*)?){$patterns['possibly_negative_quantity']}/i";
$patterns['text_shadow1'] = "/(text-shadow\s*:\s*){$patterns['possibly_negative_quantity']}(\s*){$patterns['color']}/i";
$patterns['text_shadow2'] = "/(text-shadow\s*:\s*){$patterns['color']}(\s*){$patterns['possibly_negative_quantity']}/i";
$patterns['text_shadow3'] = "/(text-shadow\s*:\s*){$patterns['possibly_negative_quantity']}/i";
$patterns['bg_horizontal_percentage'] = "/(background(?:-position)?\s*:\s*(?:[^:;}\s]+\s+)*?)({$patterns['quantity']})/i";
$patterns['bg_horizontal_percentage_x'] = "/(background-position-x\s*:\s*)(-?{$patterns['num']}%)/i";
$patterns['translate_x'] = "/(transform\s*:[^;}]*)(translateX\s*\(\s*){$patterns['possibly_negative_quantity']}(\s*\))/i";
$patterns['translate'] = "/(transform\s*:[^;}]*)(translate\s*\(\s*){$patterns['possibly_negative_quantity']}((?:\s*,\s*{$patterns['possibly_negative_quantity']}){0,2}\s*\))/i";
// @codingStandardsIgnoreEnd
self::$patterns = $patterns;
}
/**
* Transform an LTR stylesheet to RTL
*
* @param string $css Stylesheet to transform
* @param bool|array{transformDirInUrl?:bool,transformEdgeInUrl?:bool} $options Options array,
* or value of transformDirInUrl option (back-compat)
* - transformDirInUrl: Transform directions in URLs (ltr/rtl). Default: false.
* - transformEdgeInUrl: Transform edges in URLs (left/right). Default: false.
* @param bool $transformEdgeInUrl [optional] For back-compat
* @return string Transformed stylesheet
*/
public static function transform( $css, $options = [], $transformEdgeInUrl = false ) {
if ( !is_array( $options ) ) {
$options = [
'transformDirInUrl' => (bool)$options,
'transformEdgeInUrl' => (bool)$transformEdgeInUrl,
];
}
// Defaults
$options += [
'transformDirInUrl' => false,
'transformEdgeInUrl' => false,
];
self::buildPatterns();
// 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 );
// Tokenize single line rules with /* @noflip */
$noFlipSingle = new CSSJanusTokenizer( self::$patterns['noflip_single'], '`NOFLIP_SINGLE`' );
$css = $noFlipSingle->tokenize( $css );
// Tokenize class rules with /* @noflip */
$noFlipClass = new CSSJanusTokenizer( self::$patterns['noflip_class'], '`NOFLIP_CLASS`' );
$css = $noFlipClass->tokenize( $css );
// Tokenize comments
$comments = new CSSJanusTokenizer( self::$patterns['comment'], self::TOKEN_COMMENT );
$css = $comments->tokenize( $css );
// LTR->RTL fixes start here
$css = self::fixDirection( $css );
if ( $options['transformDirInUrl'] ) {
$css = self::fixLtrRtlInURL( $css );
}
if ( $options['transformEdgeInUrl'] ) {
$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 );
$css = self::fixTranslate( $css );
// Detokenize stuff we tokenized before
$css = $comments->detokenize( $css );
$css = $noFlipClass->detokenize( $css );
$css = $noFlipSingle->detokenize( $css );
return $css;
}
/**
* Replace direction: ltr; with direction: rtl; and vice versa.
*
* The original implementation only does this inside body selectors
* and misses "body\n{\ndirection:ltr;\n}". This function does not have
* these problems.
*
* See https://code.google.com/p/cssjanus/issues/detail?id=15
*
* @param string $css
* @return string
*/
private static function fixDirection( $css ) {
$css = preg_replace(
self::$patterns['direction_ltr'],
'$1' . self::TOKEN_TMP,
$css
);
$css = preg_replace( self::$patterns['direction_rtl'], '$1ltr', $css );
$css = str_replace( self::TOKEN_TMP, 'rtl', $css );
return $css;
}
/**
* Replace 'ltr' with 'rtl' and vice versa in background URLs
* @param string $css
* @return string
*/
private static function fixLtrRtlInURL( $css ) {
$css = preg_replace( self::$patterns['ltr_dir_selector'], '$1' . self::TOKEN_LTR_TMP . '$2', $css );
$css = preg_replace( self::$patterns['rtl_dir_selector'], '$1' . self::TOKEN_RTL_TMP . '$2', $css );
$css = preg_replace( self::$patterns['ltr_in_url'], self::TOKEN_TMP, $css );
$css = preg_replace( self::$patterns['rtl_in_url'], 'ltr', $css );
$css = str_replace( self::TOKEN_TMP, 'rtl', $css );
$css = str_replace( self::TOKEN_LTR_TMP, 'ltr', $css );
$css = str_replace( self::TOKEN_RTL_TMP, 'rtl', $css );
return $css;
}
/**
* Replace 'left' with 'right' and vice versa in background URLs
* @param string $css
* @return string
*/
private static function fixLeftRightInURL( $css ) {
$css = preg_replace( self::$patterns['left_in_url'], self::TOKEN_TMP, $css );
$css = preg_replace( self::$patterns['right_in_url'], 'left', $css );
$css = str_replace( self::TOKEN_TMP, 'right', $css );
return $css;
}
/**
* Flip rules like left: , padding-right: , etc.
* @param string $css
* @return string
*/
private static function fixLeftAndRight( $css ) {
$css = preg_replace( self::$patterns['left'], self::TOKEN_TMP, $css );
$css = preg_replace( self::$patterns['right'], 'left', $css );
$css = str_replace( self::TOKEN_TMP, 'right', $css );
return $css;
}
/**
* Flip East and West in rules like cursor: nw-resize;
* @param string $css
* @return string
*/
private static function fixCursorProperties( $css ) {
$css = preg_replace(
self::$patterns['cursor_east'],
'$1' . self::TOKEN_TMP,
$css
);
$css = preg_replace( self::$patterns['cursor_west'], '$1e-resize', $css );
$css = str_replace( self::TOKEN_TMP, 'w-resize', $css );
return $css;
}
/**
* Swap the second and fourth parts in four-part notation rules like
* padding: 1px 2px 3px 4px;
*
* Unlike the original implementation, this function doesn't suffer from
* the bug where whitespace is not preserved when flipping four-part rules
* and four-part color rules with multiple whitespace characters between
* colors are not recognized.
* See https://code.google.com/p/cssjanus/issues/detail?id=16
* @param string $css
* @return string
*/
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;
}
/**
* Swaps appropriate corners in border-radius values.
*
* @param string $css
* @return string
*/
private static function fixBorderRadius( $css ) {
return preg_replace_callback(
self::$patterns['border_radius'],
[ self::class, 'calculateBorderRadius' ],
$css
);
}
/**
* Callback for fixBorderRadius()
* @param array $matches
* @return string
*/
private static function calculateBorderRadius( $matches ) {
$pre = $matches[1];
$firstGroup = array_filter( array_slice( $matches, 2, 4 ), 'strlen' );
$secondGroup = array_filter( array_slice( $matches, 6, 4 ), 'strlen' );
$post = $matches[10] ?: '';
if ( $secondGroup ) {
$values = self::flipBorderRadiusValues( $firstGroup )
. ' / ' . self::flipBorderRadiusValues( $secondGroup );
} else {
$values = self::flipBorderRadiusValues( $firstGroup );
}
return $pre . $values . $post;
}
/**
* Callback for fixBorderRadius()
* @param array $values Matched values
* @return string Flipped values
*/
private static function flipBorderRadiusValues( $values ) {
switch ( count( $values ) ) {
case 4:
$values = [ $values[1], $values[0], $values[3], $values[2] ];
break;
case 3:
$values = [ $values[1], $values[0], $values[1], $values[2] ];
break;
case 2:
$values = [ $values[1], $values[0] ];
break;
case 1:
$values = [ $values[0] ];
break;
}
return implode( ' ', $values );
}
/**
* 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.
*
* @param string $cssValue
* @return string
*/
private static function flipSign( $cssValue ) {
// Don't mangle zeroes
if ( floatval( $cssValue ) === 0.0 ) {
return $cssValue;
} elseif ( $cssValue[0] === '-' ) {
return substr( $cssValue, 1 );
} else {
return "-" . $cssValue;
}
}
/**
* Negates horizontal offset in box-shadow and text-shadow rules.
*
* @param string $css
* @return string
*/
private static function fixShadows( $css ) {
$css = preg_replace_callback( self::$patterns['box_shadow'], function ( $matches ) {
return $matches[1] . self::flipSign( $matches[2] );
}, $css );
$css = preg_replace_callback( self::$patterns['text_shadow1'], function ( $matches ) {
return $matches[1] . $matches[2] . $matches[3] . self::flipSign( $matches[4] );
}, $css );
$css = preg_replace_callback( self::$patterns['text_shadow2'], function ( $matches ) {
return $matches[1] . $matches[2] . $matches[3] . self::flipSign( $matches[4] );
}, $css );
$css = preg_replace_callback( self::$patterns['text_shadow3'], function ( $matches ) {
return $matches[1] . self::flipSign( $matches[2] );
}, $css );
return $css;
}
/**
* Negates horizontal offset in tranform: translate()
*
* @param string $css
* @return string
*/
private static function fixTranslate( $css ) {
$css = preg_replace_callback( self::$patterns['translate'], function ( $matches ) {
return $matches[1] . $matches[2] . self::flipSign( $matches[3] ) . $matches[4];
}, $css );
$css = preg_replace_callback( self::$patterns['translate_x'], function ( $matches ) {
return $matches[1] . $matches[2] . self::flipSign( $matches[3] ) . $matches[4];
}, $css );
return $css;
}
/**
* Flip horizontal background percentages.
* @param string $css
* @return string
*/
private static function fixBackgroundPosition( $css ) {
$replaced = preg_replace_callback(
self::$patterns['bg_horizontal_percentage'],
[ self::class, 'calculateNewBackgroundPosition' ],
$css
);
if ( $replaced !== null ) {
// preg_replace_callback() sometimes returns null
$css = $replaced;
}
$replaced = preg_replace_callback(
self::$patterns['bg_horizontal_percentage_x'],
[ self::class, 'calculateNewBackgroundPosition' ],
$css
);
if ( $replaced !== null ) {
$css = $replaced;
}
return $css;
}
/**
* Callback for fixBackgroundPosition()
* @param array $matches
* @return string
*/
private static function calculateNewBackgroundPosition( $matches ) {
$value = $matches[2];
if ( substr( $value, -1 ) === '%' ) {
$idx = strpos( $value, '.' );
if ( $idx !== false ) {
$len = strlen( $value ) - $idx - 2;
$value = number_format( 100 - (float)$value, $len ) . '%';
} else {
$value = ( 100 - (float)$value ) . '%';
}
}
return $matches[1] . $value;
}
}
/**
* Utility class used by CSSJanus that tokenizes and untokenizes things we want
* to protect from being janused.
*/
class CSSJanusTokenizer {
private $regex;
private $token;
private $originals;
/**
* Constructor
* @param string $regex Regular expression whose matches to replace by a token.
* @param string $token Token
*/
public function __construct( $regex, $token ) {
$this->regex = $regex;
$this->token = $token;
$this->originals = [];
}
/**
* Replace all occurrences of $regex in $str with a token and remember
* the original strings.
* @param string $str to tokenize
* @return string Tokenized string
*/
public function tokenize( $str ) {
return preg_replace_callback( $this->regex, [ $this, 'tokenizeCallback' ], $str );
}
/**
* @param array $matches
* @return string
*/
private function tokenizeCallback( $matches ) {
$this->originals[] = $matches[0];
return $this->token;
}
/**
* Replace tokens with their originals. If multiple strings were tokenized, it's important they be
* detokenized in exactly the SAME ORDER.
* @param string $str previously run through tokenize()
* @return string Original string
*/
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, '/' ) . '/',
[ $this, 'detokenizeCallback' ],
$str
);
}
/**
* @param array $matches
* @return mixed
*/
private function detokenizeCallback( $matches ) {
$retval = current( $this->originals );
next( $this->originals );
return $retval;
}
}

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