CSSMin.php
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	<?php
	/**
	* Copyright 2010 Trevor Parscal <tparscal@wikimedia.org>
	*
	* 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
	* @license Apache-2.0
	*/

	namespace Wikimedia\Minify;

	use Net_URL2;

	/**
	* Transforms CSS data.
	*
	* This class provides minification, URL remapping, URL extracting, and data-URL embedding.
	*/
	class CSSMin {

	/**
	* Strip marker for comments
	*/
	private const PLACEHOLDER = "\x7fPLACEHOLDER\x7f";

	/**
	* Maximum file size to embed in a stylesheet.
	*
	* Use of `@embed` is generally discouraged (see T121730, T118514, and T120984).
	*
	* In a nut shell: Stylesheets, and thus any images we embed inside of them,
	* are required to be fully downloaded by a browser before literally any content
	* or interface component can be rendered on-screen. Embedding an image means
	* you are saying it is more important to render this image than to render the
	* page content (or that it is undesirable to render even the first paragraph
	* of an article unless this image is also immediately there in the first paint).
	*
	* There are some cases where a small image can be worth embedding, for example
	* if the image's file size is comparable or smaller than to size of the URL from
	* which it would be lazy-loaded when CSS rules are applied. In that case, embedding
	* the file content in place of the web address could be an uncompromising win for
	* all users.
	*
	* To avoid mistakes and protect performance, we put an arbitrary limit on this.
	* If a file is larger than this limit, it should probably be loaded using the
	* default CSS behaviour (by URL, without `@embed` instruction), or embedded as
	* SVG directly in the HTML response if it is such a vital part of the page.
	*
	* See encodeImageAsDataURI().
	*/
	private const DATA_URI_SIZE_LIMIT = 32768;

	private const EMBED_REGEX = '\/\\s\@embed\s\\/';
	private const COMMENT_REGEX = '\/\.?\*\/';

	/**
	* List of common image files extensions and MIME-types
	*/
	private const MIME_TYPES = [
	'gif' => 'image/gif',
	'jpe' => 'image/jpeg',
	'jpeg' => 'image/jpeg',
	'jpg' => 'image/jpeg',
	'png' => 'image/png',
	'tif' => 'image/tiff',
	'tiff' => 'image/tiff',
	'xbm' => 'image/x-xbitmap',
	'svg' => 'image/svg+xml',
	];

	/**
	* Get a list of local files referenced in a stylesheet (includes non-existent files).
	*
	* @param string $source CSS stylesheet source to process
	* @param string $path File path where the source was read from
	* @return string[] List of local file references
	*/
	public static function getLocalFileReferences( $source, $path ) {
	$stripped = preg_replace( '/' . self::COMMENT_REGEX . '/s', '', $source );
	$path = rtrim( $path, '/' ) . '/';
	$files = [];

	$rFlags = PREG_OFFSET_CAPTURE \| PREG_SET_ORDER;
	if ( preg_match_all( '/' . self::getUrlRegex() . '/J', $stripped, $matches, $rFlags ) ) {
	foreach ( $matches as $match ) {
	$url = $match['file'][0];

	// Skip fully-qualified and protocol-relative URLs and data URIs
	if (
	strpos( $url, '//' ) === 0 \|\|
	parse_url( $url, PHP_URL_SCHEME )
	) {
	break;
	}

	// Strip trailing anchors - T115436
	$anchor = strpos( $url, '#' );
	if ( $anchor !== false ) {
	$url = substr( $url, 0, $anchor );

	// '#some-anchors' is not a file
	if ( $url === '' ) {
	break;
	}
	}

	$files[] = $path . $url;
	}
	}
	return $files;
	}

	/**
	* Encode an image file as a data URI.
	*
	* If the image file has a suitable MIME type and size, encode it as a data URI, base64-encoded
	* for binary files or just percent-encoded otherwise. Return false if the image type is
	* unfamiliar or the file exceeds the size limit.
	*
	* @param string $file Image file to encode.
	* @param string\|null $type File's MIME type or null. If null, CSSMin will
	* try to autodetect the type.
	* @return string\|false Image contents encoded as a data URI or false.
	*/
	public static function encodeImageAsDataURI( $file, $type = null ) {
	// Fast-fail for files that exceed the maximum data URI length
	if ( filesize( $file ) >= self::DATA_URI_SIZE_LIMIT ) {
	trigger_error( "File exceeds limit for embedded files: $file", E_USER_WARNING );
	return false;
	}

	if ( $type === null ) {
	$type = self::getMimeType( $file );
	}
	if ( !$type ) {
	return false;
	}

	return self::encodeStringAsDataURI( file_get_contents( $file ), $type );
	}

	/**
	* Encode file contents as a data URI with chosen MIME type.
	*
	* The URI will be base64-encoded for binary files or just percent-encoded otherwise.
	*
	* @since 2.0.0
	* @param string $contents File contents to encode.
	* @param string $type File's MIME type.
	* @return string Image contents encoded as a data URI or false.
	*/
	public static function encodeStringAsDataURI( $contents, $type ) {
	// Try #1: Non-encoded data URI
	// Remove XML declaration, it's not needed with data URI usage
	$contents = preg_replace( "/<\\?xml.*?\\?>/", '', $contents );
	// The regular expression matches ASCII whitespace and printable characters.
	if ( preg_match( '/^[\r\n\t\x20-\x7e]+$/', $contents ) ) {
	// Do not base64-encode non-binary files (sensible SVGs).
	// (This often produces longer URLs, but they compress better, yielding a net smaller size.)
	$encoded = rawurlencode( $contents );
	// Unencode some things that don't need to be encoded, to make the encoding smaller
	$encoded = strtr( $encoded, [
	// Unencode spaces
	'%20' => ' ',
	// Unencode slashes
	'%2F' => '/',
	// Unencode colons
	'%3A' => ':',
	// Unencode equals signs
	'%3D' => '=',
	// Change newlines to spaces
	'%0A' => ' ',
	// Change carriage returns to spaces
	'%0D' => ' ',
	// Change tabs to spaces
	'%09' => ' ',
	] );
	// Consolidate runs of multiple spaces in a row
	$encoded = preg_replace( '/ {2,}/', ' ', $encoded );
	// Remove leading and trailing spaces
	$encoded = trim( $encoded, ' ' );
	return 'data:' . $type . ',' . $encoded;
	}

	// Try #2: Encoded data URI
	return 'data:' . $type . ';base64,' . base64_encode( $contents );
	}

	/**
	* Serialize a string (escape and quote) for use as a CSS string value.
	* https://drafts.csswg.org/cssom/#serialize-a-string
	*
	* @param string $value
	* @return string
	*/
	public static function serializeStringValue( $value ) {
	$value = strtr( $value, [ "\0" => "\u{FFFD}", '\\' => '\\\\', '"' => '\\"' ] );
	$value = preg_replace_callback( '/[\x01-\x1f\x7f]/', static function ( $match ) {
	return '\\' . base_convert( (string)ord( $match[0] ), 10, 16 ) . ' ';
	}, $value );
	return '"' . $value . '"';
	}

	/**
	* @param string $file
	* @return bool\|string
	*/
	public static function getMimeType( $file ) {
	// Infer the MIME-type from the file extension
	$ext = strtolower( pathinfo( $file, PATHINFO_EXTENSION ) );
	return self::MIME_TYPES[$ext] ?? mime_content_type( realpath( $file ) );
	}

	/**
	* Build a CSS 'url()' value for the given URL, quoting parentheses (and other funny characters)
	* and escaping quotes as necessary.
	*
	* See http://www.w3.org/TR/css-syntax-3/#consume-a-url-token
	*
	* @param string $url URL to process
	* @return string 'url()' value, usually just `"url($url)"`, quoted/escaped if necessary
	*/
	public static function buildUrlValue( $url ) {
	// The list below has been crafted to match URLs such as:
	// scheme://user@domain:port/~user/fi%20le.png?query=yes&really=y+s
	// data:image/png;base64,R0lGODlh/+==
	if ( preg_match( '!^[\w:@/~.%+;,?&=-]+$!', $url ) ) {
	return "url($url)";
	} else {
	return 'url("' . strtr( $url, [ '\\' => '\\\\', '"' => '\\"' ] ) . '")';
	}
	}

	/**
	* Remaps CSS URL paths and automatically embeds data URIs for CSS rules
	* or url() values preceded by an `/ * @embed * /` comment.
	*
	* @param string $source CSS data to remap
	* @param string $local File path where the source was read from
	* @param string $remote Full URL to the file's directory (may be protocol-relative, trailing slash is optional)
	* @param bool $embedData If false, never do any data URI embedding,
	* even if `/ * @embed * /` is found.
	* @return string Remapped CSS data
	*/
	public static function remap( $source, $local, $remote, $embedData = true ) {
	// High-level overview:
	// * For each CSS rule in $source that includes at least one url() value:
	// * Check for an @embed comment at the start indicating that all URIs should be embedded
	// * For each url() value:
	// * Check for an @embed comment directly preceding the value
	// * If either @embed comment exists:
	// * Embedding the URL as data: URI, if it's possible / allowed
	// * Otherwise remap the URL to work in generated stylesheets

	// Guard against trailing slashes, because "some/remote/../foo.png"
	// resolves to "some/remote/foo.png" on (some?) clients (T29052).
	// But, don't turn "/" into "" since that is invalid as base URL (T282280).
	$remote = $remote === '/' ? $remote : rtrim( $remote, '/' );

	// Disallow U+007F DELETE, which is illegal anyway, and which
	// we use for comment placeholders.
	$source = strtr( $source, "\x7f", "?" );

	// Replace all comments by a placeholder so they will not interfere with the remapping.
	// Warning: This will also catch on anything looking like the start of a comment between
	// quotation marks (e.g. "foo /* bar").
	$comments = [];

	$pattern = '/(?!' . self::EMBED_REGEX . ')(' . self::COMMENT_REGEX . ')/s';

	$source = preg_replace_callback(
	$pattern,
	static function ( $match ) use ( &$comments ) {
	$comments[] = $match[ 0 ];
	return self::PLACEHOLDER . ( count( $comments ) - 1 ) . 'x';
	},
	$source
	);

	// Note: This will not correctly handle cases where ';', '{' or '}'
	// appears in the rule itself, e.g. in a quoted string. You are advised
	// not to use such characters in file names. We also match start/end of
	// the string to be consistent in edge-cases ('@import url(…)').
	$pattern = '/(?:^\|[;{])\K[^;{}]' . self::getUrlRegex() . '[^;}]+(?=[;}]\|$)/J';

	$source = preg_replace_callback(
	$pattern,
	static function ( $matchOuter ) use ( $local, $remote, $embedData ) {
	$rule = $matchOuter[0];

	// Check for global @embed comment and remove it. Allow other comments to be present
	// before @embed (they have been replaced with placeholders at this point).
	$embedAll = false;
	$rule = preg_replace(
	'/^((?:\s++\|' .
	self::PLACEHOLDER .
	'(\d+)x)*+)' .
	self::EMBED_REGEX .
	'\s*/',
	'$1',
	$rule,
	1,
	$embedAll
	);

	// Build two versions of current rule: with remapped URLs
	// and with embedded data: URIs (where possible).
	$pattern = '/(?P<embed>' . self::EMBED_REGEX . '\s*\|)' . self::getUrlRegex() . '/J';

	return preg_replace_callback(
	$pattern,
	static function ( $match ) use ( $local, $remote, $embedData, $embedAll ) {
	// For each url reference in the CSS, call remapOne()
	// to insert either a remapped URL or an embedded data URI.
	// We enable use of data URIs if both of these are true:
	// 1. The PHP caller enabled the option,
	// 2. and, the CSS declared `@embed` either above the rule
	// for all URLs inside that block, or above the individual
	// property for that one property.
	$embedOne = $embedData && ( $embedAll \|\| $match['embed'] );
	$remapped = self::remapOne(
	$match['file'],
	$match['query'],
	$local,
	$remote,
	$embedOne
	);
	return self::buildUrlValue( $remapped );
	},
	$rule
	);
	}, $source );

	// Re-insert comments
	$pattern = '/' . self::PLACEHOLDER . '(\d+)x/';
	return preg_replace_callback( $pattern, static function ( $match ) use ( &$comments ) {
	return $comments[ $match[1] ];
	}, $source );
	}

	/**
	* Is this CSS rule referencing a remote URL?
	*
	* @param string $maybeUrl
	* @return bool
	*/
	protected static function isRemoteUrl( $maybeUrl ) {
	return strpos( $maybeUrl, '//' ) === 0 \|\| parse_url( $maybeUrl, PHP_URL_SCHEME );
	}

	/**
	* Is this CSS rule referencing a local URL?
	*
	* @param string $maybeUrl
	* @return bool
	*/
	protected static function isLocalUrl( $maybeUrl ) {
	// Accept "/" (known local)
	// Accept "/anything" (known local)
	// Reject "//anything" (known remote)
	// Reject "" (invalid/uncertain)
	return $maybeUrl === '/' \|\| ( isset( $maybeUrl[1] ) && $maybeUrl[0] === '/' && $maybeUrl[1] !== '/' );
	}

	/**
	* @codeCoverageIgnore
	* @return string
	*/
	private static function getUrlRegex() {
	static $urlRegex;
	if ( $urlRegex === null ) {
	// The extra + avoid backtracking where it is not needed
	$urlRegex = 'url\(\s*+(?:' .
	// Unquoted url
	'(?P<file>[^\'"][^?)]+?)(?P<query>\?[^)]*?\|)' .
	// Single quoted url
	'\|\'(?P<file>[^?\']++)(?P<query>\?[^\']*+\|)\'' .
	// Double quoted url
	'\|"(?P<file>[^?"]++)(?P<query>\?[^"]*+\|)"' .
	')\s*\)';
	}
	return $urlRegex;
	}

	/**
	* Resolve a possibly-relative URL against a base URL.
	*
	* @param string $base
	* @param string $url
	* @return string
	*/
	private static function resolveUrl( string $base, string $url ): string {
	// Net_URL2::resolve() doesn't allow for resolving against server-less URLs.
	// We need this as for MediaWiki/ResourceLoader, the remote base path may either
	// be separate (e.g. a separate domain), or simply local (like "/w"). In the
	// local case, we don't want to needlessly include the server in the output.
	$isServerless = self::isLocalUrl( $base );
	if ( $isServerless ) {
	$base = "https://placeholder.invalid$base";
	}
	// Net_URL2::resolve() doesn't allow for protocol-relative URLs, but we want to.
	$isProtoRelative = strpos( $base, '//' ) === 0;
	if ( $isProtoRelative ) {
	$base = "https:$base";
	}

	$baseUrl = new Net_URL2( $base );
	$ret = $baseUrl->resolve( $url );
	if ( $isProtoRelative ) {
	$ret->setScheme( false );
	}
	if ( $isServerless ) {
	$ret->setScheme( false );
	$ret->setHost( false );
	}
	return $ret->getURL();
	}

	/**
	* Remap or embed a CSS URL path.
	*
	* @param string $file URL to remap/embed
	* @param string $query
	* @param string $local File path where the source was read from
	* @param string $remote Full URL to the file's directory (may be protocol-relative, trailing slash is optional)
	* @param bool $embed Whether to do any data URI embedding
	* @return string Remapped/embedded URL data
	*/
	public static function remapOne( $file, $query, $local, $remote, $embed ) {
	// The full URL possibly with query, as passed to the 'url()' value in CSS
	$url = $file . $query;

	// Expand local URLs with absolute paths to a full URL (possibly protocol-relative).
	if ( self::isLocalUrl( $url ) ) {
	return self::resolveUrl( $remote, $url );
	}

	// Pass through fully-qualified and protocol-relative URLs and data URIs, as well as local URLs if
	// we can't expand them.
	// Also skips anchors or the rare `behavior` property specifying application's default behavior
	if (
	self::isRemoteUrl( $url ) \|\|
	( $url[0] ?? '' ) === '#'
	) {
	return $url;
	}

	// The $remote must have a trailing slash beyond this point for correct path resolution.
	if ( ( $remote[-1] ?? '' ) !== '/' ) {
	$remote .= '/';
	}

	if ( $local === false ) {
	// CSS specifies a path that is neither a local file path, nor a local URL.
	// It is probably already a fully-qualitied URL or data URI, but try to expand
	// it just in case.
	$url = self::resolveUrl( $remote, $url );
	} else {
	// We drop the query part here and instead make the path relative to $remote
	$url = self::resolveUrl( $remote, $file );
	// Path to the actual file on the filesystem
	$localFile = "{$local}/{$file}";
	if ( file_exists( $localFile ) ) {
	if ( $embed ) {
	$data = self::encodeImageAsDataURI( $localFile );
	if ( $data !== false ) {
	return $data;
	}
	}
	// Add version parameter as the first five hex digits
	// of the MD5 hash of the file's contents.
	$url .= '?' . substr( md5_file( $localFile ), 0, 5 );
	}
	// If any of these conditions failed (file missing, we don't want to embed it
	// or it's not embeddable), return the URL (possibly with ?timestamp part)
	}
	return $url;
	}

	/**
	* Removes whitespace from CSS data
	*
	* @param string $css CSS data to minify
	* @return string Minified CSS data
	*/
	public static function minify( $css ) {
	return trim(
	str_replace(
	[ '; ', ': ', ' {', '{ ', ', ', '} ', ';}', '( ', ' )', '[ ', ' ]' ],
	[ ';', ':', '{', '{', ',', '}', '}', '(', ')', '[', ']' ],
	preg_replace( [ '/\s+/', '/\/\.?\*\//s' ], [ ' ', '' ], $css )
	)
	);
	}
	}

	/**
	* @deprecated since 2.1.0 Use Wikimedia\Minify\CSSMin instead
	*/
	class_alias( CSSMin::class, 'CSSMin' );

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