API: Pretty-printed responses should always use HTTP status 200

[mediawiki.git] / includes / resourceloader / ResourceLoaderFileModule.php

<?php
/**
 * ResourceLoader module based on local JavaScript/CSS files.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @author Trevor Parscal
 * @author Roan Kattouw
 */

/**
 * ResourceLoader module based on local JavaScript/CSS files.
 */
class ResourceLoaderFileModule extends ResourceLoaderModule {
        /* Protected Members */

        /** @var string Local base path, see __construct() */
        protected $localBasePath = '';

        /** @var string Remote base path, see __construct() */
        protected $remoteBasePath = '';

        /** @var array Saves a list of the templates named by the modules. */
        protected $templates = [];

        /**
         * @var array List of paths to JavaScript files to always include
         * @par Usage:
         * @code
         * [ [file-path], [file-path], ... ]
         * @endcode
         */
        protected $scripts = [];

        /**
         * @var array List of JavaScript files to include when using a specific language
         * @par Usage:
         * @code
         * [ [language-code] => [ [file-path], [file-path], ... ], ... ]
         * @endcode
         */
        protected $languageScripts = [];

        /**
         * @var array List of JavaScript files to include when using a specific skin
         * @par Usage:
         * @code
         * [ [skin-name] => [ [file-path], [file-path], ... ], ... ]
         * @endcode
         */
        protected $skinScripts = [];

        /**
         * @var array List of paths to JavaScript files to include in debug mode
         * @par Usage:
         * @code
         * [ [skin-name] => [ [file-path], [file-path], ... ], ... ]
         * @endcode
         */
        protected $debugScripts = [];

        /**
         * @var array List of paths to CSS files to always include
         * @par Usage:
         * @code
         * [ [file-path], [file-path], ... ]
         * @endcode
         */
        protected $styles = [];

        /**
         * @var array List of paths to CSS files to include when using specific skins
         * @par Usage:
         * @code
         * [ [file-path], [file-path], ... ]
         * @endcode
         */
        protected $skinStyles = [];

        /**
         * @var array List of modules this module depends on
         * @par Usage:
         * @code
         * [ [file-path], [file-path], ... ]
         * @endcode
         */
        protected $dependencies = [];

        /**
         * @var string File name containing the body of the skip function
         */
        protected $skipFunction = null;

        /**
         * @var array List of message keys used by this module
         * @par Usage:
         * @code
         * [ [message-key], [message-key], ... ]
         * @endcode
         */
        protected $messages = [];

        /** @var string Name of group to load this module in */
        protected $group;

        /** @var string Position on the page to load this module at */
        protected $position = 'bottom';

        /** @var bool Link to raw files in debug mode */
        protected $debugRaw = true;

        /** @var bool Whether mw.loader.state() call should be omitted */
        protected $raw = false;

        protected $targets = [ 'desktop' ];

        /** @var bool Whether CSSJanus flipping should be skipped for this module */
        protected $noflip = false;

        /**
         * @var bool Whether getStyleURLsForDebug should return raw file paths,
         * or return load.php urls
         */
        protected $hasGeneratedStyles = false;

        /**
         * @var array Place where readStyleFile() tracks file dependencies
         * @par Usage:
         * @code
         * [ [file-path], [file-path], ... ]
         * @endcode
         */
        protected $localFileRefs = [];

        /**
         * @var array Place where readStyleFile() tracks file dependencies for non-existent files.
         * Used in tests to detect missing dependencies.
         */
        protected $missingLocalFileRefs = [];

        /* Methods */

        /**
         * Constructs a new module from an options array.
         *
         * @param array $options List of options; if not given or empty, an empty module will be
         *     constructed
         * @param string $localBasePath Base path to prepend to all local paths in $options. Defaults
         *     to $IP
         * @param string $remoteBasePath Base path to prepend to all remote paths in $options. Defaults
         *     to $wgResourceBasePath
         *
         * Below is a description for the $options array:
         * @throws InvalidArgumentException
         * @par Construction options:
         * @code
         *     [
         *         // Base path to prepend to all local paths in $options. Defaults to $IP
         *         'localBasePath' => [base path],
         *         // Base path to prepend to all remote paths in $options. Defaults to $wgResourceBasePath
         *         'remoteBasePath' => [base path],
         *         // Equivalent of remoteBasePath, but relative to $wgExtensionAssetsPath
         *         'remoteExtPath' => [base path],
         *         // Equivalent of remoteBasePath, but relative to $wgStylePath
         *         'remoteSkinPath' => [base path],
         *         // Scripts to always include
         *         'scripts' => [file path string or array of file path strings],
         *         // Scripts to include in specific language contexts
         *         'languageScripts' => [
         *             [language code] => [file path string or array of file path strings],
         *         ],
         *         // Scripts to include in specific skin contexts
         *         'skinScripts' => [
         *             [skin name] => [file path string or array of file path strings],
         *         ],
         *         // Scripts to include in debug contexts
         *         'debugScripts' => [file path string or array of file path strings],
         *         // Modules which must be loaded before this module
         *         'dependencies' => [module name string or array of module name strings],
         *         'templates' => [
         *             [template alias with file.ext] => [file path to a template file],
         *         ],
         *         // Styles to always load
         *         'styles' => [file path string or array of file path strings],
         *         // Styles to include in specific skin contexts
         *         'skinStyles' => [
         *             [skin name] => [file path string or array of file path strings],
         *         ],
         *         // Messages to always load
         *         'messages' => [array of message key strings],
         *         // Group which this module should be loaded together with
         *         'group' => [group name string],
         *         // Position on the page to load this module at
         *         'position' => ['bottom' (default) or 'top']
         *         // Function that, if it returns true, makes the loader skip this module.
         *         // The file must contain valid JavaScript for execution in a private function.
         *         // The file must not contain the "function () {" and "}" wrapper though.
         *         'skipFunction' => [file path]
         *     ]
         * @endcode
         */
        public function __construct(
                $options = [],
                $localBasePath = null,
                $remoteBasePath = null
        ) {
                // Flag to decide whether to automagically add the mediawiki.template module
                $hasTemplates = false;
                // localBasePath and remoteBasePath both have unbelievably long fallback chains
                // and need to be handled separately.
                list( $this->localBasePath, $this->remoteBasePath ) =
                        self::extractBasePaths( $options, $localBasePath, $remoteBasePath );

                // Extract, validate and normalise remaining options
                foreach ( $options as $member => $option ) {
                        switch ( $member ) {
                                // Lists of file paths
                                case 'scripts':
                                case 'debugScripts':
                                case 'styles':
                                        $this->{$member} = (array)$option;
                                        break;
                                case 'templates':
                                        $hasTemplates = true;
                                        $this->{$member} = (array)$option;
                                        break;
                                // Collated lists of file paths
                                case 'languageScripts':
                                case 'skinScripts':
                                case 'skinStyles':
                                        if ( !is_array( $option ) ) {
                                                throw new InvalidArgumentException(
                                                        "Invalid collated file path list error. " .
                                                        "'$option' given, array expected."
                                                );
                                        }
                                        foreach ( $option as $key => $value ) {
                                                if ( !is_string( $key ) ) {
                                                        throw new InvalidArgumentException(
                                                                "Invalid collated file path list key error. " .
                                                                "'$key' given, string expected."
                                                        );
                                                }
                                                $this->{$member}[$key] = (array)$value;
                                        }
                                        break;
                                case 'deprecated':
                                        $this->deprecated = $option;
                                        break;
                                // Lists of strings
                                case 'dependencies':
                                case 'messages':
                                case 'targets':
                                        // Normalise
                                        $option = array_values( array_unique( (array)$option ) );
                                        sort( $option );

                                        $this->{$member} = $option;
                                        break;
                                // Single strings
                                case 'position':
                                case 'group':
                                case 'skipFunction':
                                        $this->{$member} = (string)$option;
                                        break;
                                // Single booleans
                                case 'debugRaw':
                                case 'raw':
                                case 'noflip':
                                        $this->{$member} = (bool)$option;
                                        break;
                        }
                }
                if ( $hasTemplates ) {
                        $this->dependencies[] = 'mediawiki.template';
                        // Ensure relevant template compiler module gets loaded
                        foreach ( $this->templates as $alias => $templatePath ) {
                                if ( is_int( $alias ) ) {
                                        $alias = $templatePath;
                                }
                                $suffix = explode( '.', $alias );
                                $suffix = end( $suffix );
                                $compilerModule = 'mediawiki.template.' . $suffix;
                                if ( $suffix !== 'html' && !in_array( $compilerModule, $this->dependencies ) ) {
                                        $this->dependencies[] = $compilerModule;
                                }
                        }
                }
        }

        /**
         * Extract a pair of local and remote base paths from module definition information.
         * Implementation note: the amount of global state used in this function is staggering.
         *
         * @param array $options Module definition
         * @param string $localBasePath Path to use if not provided in module definition. Defaults
         *     to $IP
         * @param string $remoteBasePath Path to use if not provided in module definition. Defaults
         *     to $wgResourceBasePath
         * @return array Array( localBasePath, remoteBasePath )
         */
        public static function extractBasePaths(
                $options = [],
                $localBasePath = null,
                $remoteBasePath = null
        ) {
                global $IP, $wgResourceBasePath;

                // The different ways these checks are done, and their ordering, look very silly,
                // but were preserved for backwards-compatibility just in case. Tread lightly.

                if ( $localBasePath === null ) {
                        $localBasePath = $IP;
                }
                if ( $remoteBasePath === null ) {
                        $remoteBasePath = $wgResourceBasePath;
                }

                if ( isset( $options['remoteExtPath'] ) ) {
                        global $wgExtensionAssetsPath;
                        $remoteBasePath = $wgExtensionAssetsPath . '/' . $options['remoteExtPath'];
                }

                if ( isset( $options['remoteSkinPath'] ) ) {
                        global $wgStylePath;
                        $remoteBasePath = $wgStylePath . '/' . $options['remoteSkinPath'];
                }

                if ( array_key_exists( 'localBasePath', $options ) ) {
                        $localBasePath = (string)$options['localBasePath'];
                }

                if ( array_key_exists( 'remoteBasePath', $options ) ) {
                        $remoteBasePath = (string)$options['remoteBasePath'];
                }

                return [ $localBasePath, $remoteBasePath ];
        }

        /**
         * Gets all scripts for a given context concatenated together.
         *
         * @param ResourceLoaderContext $context Context in which to generate script
         * @return string JavaScript code for $context
         */
        public function getScript( ResourceLoaderContext $context ) {
                $files = $this->getScriptFiles( $context );
                return $this->getDeprecationInformation() . $this->readScriptFiles( $files );
        }

        /**
         * @param ResourceLoaderContext $context
         * @return array
         */
        public function getScriptURLsForDebug( ResourceLoaderContext $context ) {
                $urls = [];
                foreach ( $this->getScriptFiles( $context ) as $file ) {
                        $urls[] = OutputPage::transformResourcePath(
                                $this->getConfig(),
                                $this->getRemotePath( $file )
                        );
                }
                return $urls;
        }

        /**
         * @return bool
         */
        public function supportsURLLoading() {
                return $this->debugRaw;
        }

        /**
         * Get all styles for a given context.
         *
         * @param ResourceLoaderContext $context
         * @return array CSS code for $context as an associative array mapping media type to CSS text.
         */
        public function getStyles( ResourceLoaderContext $context ) {
                $styles = $this->readStyleFiles(
                        $this->getStyleFiles( $context ),
                        $this->getFlip( $context ),
                        $context
                );
                // Collect referenced files
                $this->saveFileDependencies( $context, $this->localFileRefs );

                return $styles;
        }

        /**
         * @param ResourceLoaderContext $context
         * @return array
         */
        public function getStyleURLsForDebug( ResourceLoaderContext $context ) {
                if ( $this->hasGeneratedStyles ) {
                        // Do the default behaviour of returning a url back to load.php
                        // but with only=styles.
                        return parent::getStyleURLsForDebug( $context );
                }
                // Our module consists entirely of real css files,
                // in debug mode we can load those directly.
                $urls = [];
                foreach ( $this->getStyleFiles( $context ) as $mediaType => $list ) {
                        $urls[$mediaType] = [];
                        foreach ( $list as $file ) {
                                $urls[$mediaType][] = OutputPage::transformResourcePath(
                                        $this->getConfig(),
                                        $this->getRemotePath( $file )
                                );
                        }
                }
                return $urls;
        }

        /**
         * Gets list of message keys used by this module.
         *
         * @return array List of message keys
         */
        public function getMessages() {
                return $this->messages;
        }

        /**
         * Gets the name of the group this module should be loaded in.
         *
         * @return string Group name
         */
        public function getGroup() {
                return $this->group;
        }

        /**
         * @return string
         */
        public function getPosition() {
                return $this->position;
        }

        /**
         * Gets list of names of modules this module depends on.
         * @param ResourceLoaderContext|null $context
         * @return array List of module names
         */
        public function getDependencies( ResourceLoaderContext $context = null ) {
                return $this->dependencies;
        }

        /**
         * Get the skip function.
         * @return null|string
         * @throws MWException
         */
        public function getSkipFunction() {
                if ( !$this->skipFunction ) {
                        return null;
                }

                $localPath = $this->getLocalPath( $this->skipFunction );
                if ( !file_exists( $localPath ) ) {
                        throw new MWException( __METHOD__ . ": skip function file not found: \"$localPath\"" );
                }
                $contents = $this->stripBom( file_get_contents( $localPath ) );
                if ( $this->getConfig()->get( 'ResourceLoaderValidateStaticJS' ) ) {
                        $contents = $this->validateScriptFile( $localPath, $contents );
                }
                return $contents;
        }

        /**
         * @return bool
         */
        public function isRaw() {
                return $this->raw;
        }

        /**
         * Disable module content versioning.
         *
         * This class uses getDefinitionSummary() instead, to avoid filesystem overhead
         * involved with building the full module content inside a startup request.
         *
         * @return bool
         */
        public function enableModuleContentVersion() {
                return false;
        }

        /**
         * Helper method to gather file hashes for getDefinitionSummary.
         *
         * This function is context-sensitive, only computing hashes of files relevant to the
         * given language, skin, etc.
         *
         * @see ResourceLoaderModule::getFileDependencies
         * @param ResourceLoaderContext $context
         * @return array
         */
        protected function getFileHashes( ResourceLoaderContext $context ) {
                $files = [];

                // Flatten style files into $files
                $styles = self::collateFilePathListByOption( $this->styles, 'media', 'all' );
                foreach ( $styles as $styleFiles ) {
                        $files = array_merge( $files, $styleFiles );
                }

                $skinFiles = self::collateFilePathListByOption(
                        self::tryForKey( $this->skinStyles, $context->getSkin(), 'default' ),
                        'media',
                        'all'
                );
                foreach ( $skinFiles as $styleFiles ) {
                        $files = array_merge( $files, $styleFiles );
                }

                // Final merge, this should result in a master list of dependent files
                $files = array_merge(
                        $files,
                        $this->scripts,
                        $this->templates,
                        $context->getDebug() ? $this->debugScripts : [],
                        $this->getLanguageScripts( $context->getLanguage() ),
                        self::tryForKey( $this->skinScripts, $context->getSkin(), 'default' )
                );
                if ( $this->skipFunction ) {
                        $files[] = $this->skipFunction;
                }
                $files = array_map( [ $this, 'getLocalPath' ], $files );
                // File deps need to be treated separately because they're already prefixed
                $files = array_merge( $files, $this->getFileDependencies( $context ) );
                // Filter out any duplicates from getFileDependencies() and others.
                // Most commonly introduced by compileLessFile(), which always includes the
                // entry point Less file we already know about.
                $files = array_values( array_unique( $files ) );

                // Don't include keys or file paths here, only the hashes. Including that would needlessly
                // cause global cache invalidation when files move or if e.g. the MediaWiki path changes.
                // Any significant ordering is already detected by the definition summary.
                return array_map( [ __CLASS__, 'safeFileHash' ], $files );
        }

        /**
         * Get the definition summary for this module.
         *
         * @param ResourceLoaderContext $context
         * @return array
         */
        public function getDefinitionSummary( ResourceLoaderContext $context ) {
                $summary = parent::getDefinitionSummary( $context );

                $options = [];
                foreach ( [
                        // The following properties are omitted because they don't affect the module reponse:
                        // - localBasePath (Per T104950; Changes when absolute directory name changes. If
                        //    this affects 'scripts' and other file paths, getFileHashes accounts for that.)
                        // - remoteBasePath (Per T104950)
                        // - dependencies (provided via startup module)
                        // - targets
                        // - group (provided via startup module)
                        // - position (only used by OutputPage)
                        'scripts',
                        'debugScripts',
                        'styles',
                        'languageScripts',
                        'skinScripts',
                        'skinStyles',
                        'messages',
                        'templates',
                        'skipFunction',
                        'debugRaw',
                        'raw',
                ] as $member ) {
                        $options[$member] = $this->{$member};
                };

                $summary[] = [
                        'options' => $options,
                        'fileHashes' => $this->getFileHashes( $context ),
                        'messageBlob' => $this->getMessageBlob( $context ),
                ];
                return $summary;
        }

        /**
         * @param string|ResourceLoaderFilePath $path
         * @return string
         */
        protected function getLocalPath( $path ) {
                if ( $path instanceof ResourceLoaderFilePath ) {
                        return $path->getLocalPath();
                }

                return "{$this->localBasePath}/$path";
        }

        /**
         * @param string|ResourceLoaderFilePath $path
         * @return string
         */
        protected function getRemotePath( $path ) {
                if ( $path instanceof ResourceLoaderFilePath ) {
                        return $path->getRemotePath();
                }

                return "{$this->remoteBasePath}/$path";
        }

        /**
         * Infer the stylesheet language from a stylesheet file path.
         *
         * @since 1.22
         * @param string $path
         * @return string The stylesheet language name
         */
        public function getStyleSheetLang( $path ) {
                return preg_match( '/\.less$/i', $path ) ? 'less' : 'css';
        }

        /**
         * Collates file paths by option (where provided).
         *
         * @param array $list List of file paths in any combination of index/path
         *     or path/options pairs
         * @param string $option Option name
         * @param mixed $default Default value if the option isn't set
         * @return array List of file paths, collated by $option
         */
        protected static function collateFilePathListByOption( array $list, $option, $default ) {
                $collatedFiles = [];
                foreach ( (array)$list as $key => $value ) {
                        if ( is_int( $key ) ) {
                                // File name as the value
                                if ( !isset( $collatedFiles[$default] ) ) {
                                        $collatedFiles[$default] = [];
                                }
                                $collatedFiles[$default][] = $value;
                        } elseif ( is_array( $value ) ) {
                                // File name as the key, options array as the value
                                $optionValue = isset( $value[$option] ) ? $value[$option] : $default;
                                if ( !isset( $collatedFiles[$optionValue] ) ) {
                                        $collatedFiles[$optionValue] = [];
                                }
                                $collatedFiles[$optionValue][] = $key;
                        }
                }
                return $collatedFiles;
        }

        /**
         * Get a list of element that match a key, optionally using a fallback key.
         *
         * @param array $list List of lists to select from
         * @param string $key Key to look for in $map
         * @param string $fallback Key to look for in $list if $key doesn't exist
         * @return array List of elements from $map which matched $key or $fallback,
         *  or an empty list in case of no match
         */
        protected static function tryForKey( array $list, $key, $fallback = null ) {
                if ( isset( $list[$key] ) && is_array( $list[$key] ) ) {
                        return $list[$key];
                } elseif ( is_string( $fallback )
                        && isset( $list[$fallback] )
                        && is_array( $list[$fallback] )
                ) {
                        return $list[$fallback];
                }
                return [];
        }

        /**
         * Get a list of file paths for all scripts in this module, in order of proper execution.
         *
         * @param ResourceLoaderContext $context
         * @return array List of file paths
         */
        protected function getScriptFiles( ResourceLoaderContext $context ) {
                $files = array_merge(
                        $this->scripts,
                        $this->getLanguageScripts( $context->getLanguage() ),
                        self::tryForKey( $this->skinScripts, $context->getSkin(), 'default' )
                );
                if ( $context->getDebug() ) {
                        $files = array_merge( $files, $this->debugScripts );
                }

                return array_unique( $files, SORT_REGULAR );
        }

        /**
         * Get the set of language scripts for the given language,
         * possibly using a fallback language.
         *
         * @param string $lang
         * @return array
         */
        private function getLanguageScripts( $lang ) {
                $scripts = self::tryForKey( $this->languageScripts, $lang );
                if ( $scripts ) {
                        return $scripts;
                }
                $fallbacks = Language::getFallbacksFor( $lang );
                foreach ( $fallbacks as $lang ) {
                        $scripts = self::tryForKey( $this->languageScripts, $lang );
                        if ( $scripts ) {
                                return $scripts;
                        }
                }

                return [];
        }

        /**
         * Get a list of file paths for all styles in this module, in order of proper inclusion.
         *
         * @param ResourceLoaderContext $context
         * @return array List of file paths
         */
        public function getStyleFiles( ResourceLoaderContext $context ) {
                return array_merge_recursive(
                        self::collateFilePathListByOption( $this->styles, 'media', 'all' ),
                        self::collateFilePathListByOption(
                                self::tryForKey( $this->skinStyles, $context->getSkin(), 'default' ),
                                'media',
                                'all'
                        )
                );
        }

        /**
         * Gets a list of file paths for all skin styles in the module used by
         * the skin.
         *
         * @param string $skinName The name of the skin
         * @return array A list of file paths collated by media type
         */
        protected function getSkinStyleFiles( $skinName ) {
                return self::collateFilePathListByOption(
                        self::tryForKey( $this->skinStyles, $skinName ),
                        'media',
                        'all'
                );
        }

        /**
         * Gets a list of file paths for all skin style files in the module,
         * for all available skins.
         *
         * @return array A list of file paths collated by media type
         */
        protected function getAllSkinStyleFiles() {
                $styleFiles = [];
                $internalSkinNames = array_keys( Skin::getSkinNames() );
                $internalSkinNames[] = 'default';

                foreach ( $internalSkinNames as $internalSkinName ) {
                        $styleFiles = array_merge_recursive(
                                $styleFiles,
                                $this->getSkinStyleFiles( $internalSkinName )
                        );
                }

                return $styleFiles;
        }

        /**
         * Returns all style files and all skin style files used by this module.
         *
         * @return array
         */
        public function getAllStyleFiles() {
                $collatedStyleFiles = array_merge_recursive(
                        self::collateFilePathListByOption( $this->styles, 'media', 'all' ),
                        $this->getAllSkinStyleFiles()
                );

                $result = [];

                foreach ( $collatedStyleFiles as $media => $styleFiles ) {
                        foreach ( $styleFiles as $styleFile ) {
                                $result[] = $this->getLocalPath( $styleFile );
                        }
                }

                return $result;
        }

        /**
         * Gets the contents of a list of JavaScript files.
         *
         * @param array $scripts List of file paths to scripts to read, remap and concetenate
         * @throws MWException
         * @return string Concatenated and remapped JavaScript data from $scripts
         */
        protected function readScriptFiles( array $scripts ) {
                if ( empty( $scripts ) ) {
                        return '';
                }
                $js = '';
                foreach ( array_unique( $scripts, SORT_REGULAR ) as $fileName ) {
                        $localPath = $this->getLocalPath( $fileName );
                        if ( !file_exists( $localPath ) ) {
                                throw new MWException( __METHOD__ . ": script file not found: \"$localPath\"" );
                        }
                        $contents = $this->stripBom( file_get_contents( $localPath ) );
                        if ( $this->getConfig()->get( 'ResourceLoaderValidateStaticJS' ) ) {
                                // Static files don't really need to be checked as often; unlike
                                // on-wiki module they shouldn't change unexpectedly without
                                // admin interference.
                                $contents = $this->validateScriptFile( $fileName, $contents );
                        }
                        $js .= $contents . "\n";
                }
                return $js;
        }

        /**
         * Gets the contents of a list of CSS files.
         *
         * @param array $styles List of media type/list of file paths pairs, to read, remap and
         * concetenate
         * @param bool $flip
         * @param ResourceLoaderContext $context
         *
         * @throws MWException
         * @return array List of concatenated and remapped CSS data from $styles,
         *     keyed by media type
         *
         * @since 1.27 Calling this method without a ResourceLoaderContext instance
         *   is deprecated.
         */
        public function readStyleFiles( array $styles, $flip, $context = null ) {
                if ( $context === null ) {
                        wfDeprecated( __METHOD__ . ' without a ResourceLoader context', '1.27' );
                        $context = ResourceLoaderContext::newDummyContext();
                }

                if ( empty( $styles ) ) {
                        return [];
                }
                foreach ( $styles as $media => $files ) {
                        $uniqueFiles = array_unique( $files, SORT_REGULAR );
                        $styleFiles = [];
                        foreach ( $uniqueFiles as $file ) {
                                $styleFiles[] = $this->readStyleFile( $file, $flip, $context );
                        }
                        $styles[$media] = implode( "\n", $styleFiles );
                }
                return $styles;
        }

        /**
         * Reads a style file.
         *
         * This method can be used as a callback for array_map()
         *
         * @param string $path File path of style file to read
         * @param bool $flip
         * @param ResourceLoaderContext $context
         *
         * @return string CSS data in script file
         * @throws MWException If the file doesn't exist
         */
        protected function readStyleFile( $path, $flip, $context ) {
                $localPath = $this->getLocalPath( $path );
                $remotePath = $this->getRemotePath( $path );
                if ( !file_exists( $localPath ) ) {
                        $msg = __METHOD__ . ": style file not found: \"$localPath\"";
                        wfDebugLog( 'resourceloader', $msg );
                        throw new MWException( $msg );
                }

                if ( $this->getStyleSheetLang( $localPath ) === 'less' ) {
                        $style = $this->compileLessFile( $localPath, $context );
                        $this->hasGeneratedStyles = true;
                } else {
                        $style = $this->stripBom( file_get_contents( $localPath ) );
                }

                if ( $flip ) {
                        $style = CSSJanus::transform( $style, true, false );
                }
                $localDir = dirname( $localPath );
                $remoteDir = dirname( $remotePath );
                // Get and register local file references
                $localFileRefs = CSSMin::getLocalFileReferences( $style, $localDir );
                foreach ( $localFileRefs as $file ) {
                        if ( file_exists( $file ) ) {
                                $this->localFileRefs[] = $file;
                        } else {
                                $this->missingLocalFileRefs[] = $file;
                        }
                }
                // Don't cache this call. remap() ensures data URIs embeds are up to date,
                // and urls contain correct content hashes in their query string. (T128668)
                return CSSMin::remap( $style, $localDir, $remoteDir, true );
        }

        /**
         * Get whether CSS for this module should be flipped
         * @param ResourceLoaderContext $context
         * @return bool
         */
        public function getFlip( $context ) {
                return $context->getDirection() === 'rtl' && !$this->noflip;
        }

        /**
         * Get target(s) for the module, eg ['desktop'] or ['desktop', 'mobile']
         *
         * @return array Array of strings
         */
        public function getTargets() {
                return $this->targets;
        }

        /**
         * Get the module's load type.
         *
         * @since 1.28
         * @return string
         */
        public function getType() {
                $canBeStylesOnly = !(
                        // All options except 'styles', 'skinStyles' and 'debugRaw'
                        $this->scripts
                        || $this->debugScripts
                        || $this->templates
                        || $this->languageScripts
                        || $this->skinScripts
                        || $this->dependencies
                        || $this->messages
                        || $this->skipFunction
                        || $this->raw
                );
                return $canBeStylesOnly ? self::LOAD_STYLES : self::LOAD_GENERAL;
        }

        /**
         * Compile a LESS file into CSS.
         *
         * Keeps track of all used files and adds them to localFileRefs.
         *
         * @since 1.22
         * @since 1.27 Added $context paramter.
         * @throws Exception If less.php encounters a parse error
         * @param string $fileName File path of LESS source
         * @param ResourceLoaderContext $context Context in which to generate script
         * @return string CSS source
         */
        protected function compileLessFile( $fileName, ResourceLoaderContext $context ) {
                static $cache;

                if ( !$cache ) {
                        $cache = ObjectCache::getLocalServerInstance( CACHE_ANYTHING );
                }

                // Construct a cache key from the LESS file name and a hash digest
                // of the LESS variables used for compilation.
                $vars = $this->getLessVars( $context );
                ksort( $vars );
                $varsHash = hash( 'md4', serialize( $vars ) );
                $cacheKey = $cache->makeGlobalKey( 'LESS', $fileName, $varsHash );
                $cachedCompile = $cache->get( $cacheKey );

                // If we got a cached value, we have to validate it by getting a
                // checksum of all the files that were loaded by the parser and
                // ensuring it matches the cached entry's.
                if ( isset( $cachedCompile['hash'] ) ) {
                        $contentHash = FileContentsHasher::getFileContentsHash( $cachedCompile['files'] );
                        if ( $contentHash === $cachedCompile['hash'] ) {
                                $this->localFileRefs = array_merge( $this->localFileRefs, $cachedCompile['files'] );
                                return $cachedCompile['css'];
                        }
                }

                $compiler = $context->getResourceLoader()->getLessCompiler( $vars );
                $css = $compiler->parseFile( $fileName )->getCss();
                $files = $compiler->AllParsedFiles();
                $this->localFileRefs = array_merge( $this->localFileRefs, $files );

                $cache->set( $cacheKey, [
                        'css'   => $css,
                        'files' => $files,
                        'hash'  => FileContentsHasher::getFileContentsHash( $files ),
                ], 60 * 60 * 24 );  // 86400 seconds, or 24 hours.

                return $css;
        }

        /**
         * Takes named templates by the module and returns an array mapping.
         * @return array of templates mapping template alias to content
         * @throws MWException
         */
        public function getTemplates() {
                $templates = [];

                foreach ( $this->templates as $alias => $templatePath ) {
                        // Alias is optional
                        if ( is_int( $alias ) ) {
                                $alias = $templatePath;
                        }
                        $localPath = $this->getLocalPath( $templatePath );
                        if ( file_exists( $localPath ) ) {
                                $content = file_get_contents( $localPath );
                                $templates[$alias] = $this->stripBom( $content );
                        } else {
                                $msg = __METHOD__ . ": template file not found: \"$localPath\"";
                                wfDebugLog( 'resourceloader', $msg );
                                throw new MWException( $msg );
                        }
                }
                return $templates;
        }

        /**
         * Takes an input string and removes the UTF-8 BOM character if present
         *
         * We need to remove these after reading a file, because we concatenate our files and
         * the BOM character is not valid in the middle of a string.
         * We already assume UTF-8 everywhere, so this should be safe.
         *
         * @return string input minus the intial BOM char
         */
        protected function stripBom( $input ) {
                if ( substr_compare( "\xef\xbb\xbf", $input, 0, 3 ) === 0 ) {
                        return substr( $input, 3 );
                }
                return $input;
        }
}