Merge "registration: Avoid redundant LBYL check in ExtensionRegistry::queue()"

[lhc/web/wiklou.git] / includes / resourceloader / ResourceLoader.php

<?php
/**
 * Base class for resource loading system.
 *
 * 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 Roan Kattouw
 * @author Trevor Parscal
 */

use MediaWiki\MediaWikiServices;
use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use Wikimedia\Rdbms\DBConnectionError;
use Wikimedia\WrappedString;

/**
 * Dynamic JavaScript and CSS resource loading system.
 *
 * Most of the documentation is on the MediaWiki documentation wiki starting at:
 *    https://www.mediawiki.org/wiki/ResourceLoader
 */
class ResourceLoader implements LoggerAwareInterface {
        /** @var Config $config */
        protected $config;
        /** @var MessageBlobStore */
        protected $blobStore;

        /** @var LoggerInterface */
        private $logger;

        /** @var ResourceLoaderModule[] Map of (module name => ResourceLoaderModule) */
        protected $modules = [];
        /** @var array[] Map of (module name => associative info array) */
        protected $moduleInfos = [];
        /**
         * Associative array mapping framework ids to a list of names of test suite modules
         * like [ 'qunit' => [ 'mediawiki.tests.qunit.suites', 'ext.foo.tests', ... ], ... ]
         * @var array
         */
        protected $testModuleNames = [];
        /** @var string[] List of module names that contain QUnit test suites */
        protected $testSuiteModuleNames = [];

        /** @var array Map of (source => path); E.g. [ 'source-id' => 'http://.../load.php' ] */
        protected $sources = [];
        /** @var array Errors accumulated during current respond() call */
        protected $errors = [];
        /** @var string[] Extra HTTP response headers from modules loaded in makeModuleResponse() */
        protected $extraHeaders = [];

        /** @var bool */
        protected static $debugMode = null;

        /** @var int */
        const CACHE_VERSION = 8;

        /** @var string JavaScript / CSS pragma to disable minification. * */
        const FILTER_NOMIN = '/*@nomin*/';

        /**
         * Load information stored in the database about modules.
         *
         * This method grabs modules dependencies from the database and updates modules
         * objects.
         *
         * This is not inside the module code because it is much faster to
         * request all of the information at once than it is to have each module
         * requests its own information. This sacrifice of modularity yields a substantial
         * performance improvement.
         *
         * @param array $moduleNames List of module names to preload information for
         * @param ResourceLoaderContext $context Context to load the information within
         */
        public function preloadModuleInfo( array $moduleNames, ResourceLoaderContext $context ) {
                if ( !$moduleNames ) {
                        // Or else Database*::select() will explode, plus it's cheaper!
                        return;
                }
                $dbr = wfGetDB( DB_REPLICA );
                $lang = $context->getLanguage();

                // Batched version of ResourceLoaderModule::getFileDependencies
                $vary = ResourceLoaderModule::getVary( $context );
                $res = $dbr->select( 'module_deps', [ 'md_module', 'md_deps' ], [
                                'md_module' => $moduleNames,
                                'md_skin' => $vary,
                        ], __METHOD__
                );

                // Prime in-object cache for file dependencies
                $modulesWithDeps = [];
                foreach ( $res as $row ) {
                        $module = $this->getModule( $row->md_module );
                        if ( $module ) {
                                $module->setFileDependencies( $context, ResourceLoaderModule::expandRelativePaths(
                                        json_decode( $row->md_deps, true )
                                ) );
                                $modulesWithDeps[] = $row->md_module;
                        }
                }
                // Register the absence of a dependency row too
                foreach ( array_diff( $moduleNames, $modulesWithDeps ) as $name ) {
                        $module = $this->getModule( $name );
                        if ( $module ) {
                                $this->getModule( $name )->setFileDependencies( $context, [] );
                        }
                }

                // Batched version of ResourceLoaderWikiModule::getTitleInfo
                ResourceLoaderWikiModule::preloadTitleInfo( $context, $dbr, $moduleNames );

                // Prime in-object cache for message blobs for modules with messages
                $modules = [];
                foreach ( $moduleNames as $name ) {
                        $module = $this->getModule( $name );
                        if ( $module && $module->getMessages() ) {
                                $modules[$name] = $module;
                        }
                }
                $store = $this->getMessageBlobStore();
                $blobs = $store->getBlobs( $modules, $lang );
                foreach ( $blobs as $name => $blob ) {
                        $modules[$name]->setMessageBlob( $blob, $lang );
                }
        }

        /**
         * Run JavaScript or CSS data through a filter, caching the filtered result for future calls.
         *
         * Available filters are:
         *
         *    - minify-js \see JavaScriptMinifier::minify
         *    - minify-css \see CSSMin::minify
         *
         * If $data is empty, only contains whitespace or the filter was unknown,
         * $data is returned unmodified.
         *
         * @param string $filter Name of filter to run
         * @param string $data Text to filter, such as JavaScript or CSS text
         * @param array $options Keys:
         *  - (bool) cache: Whether to allow caching this data. Default: true.
         * @return string Filtered data, or a comment containing an error message
         */
        public static function filter( $filter, $data, array $options = [] ) {
                if ( strpos( $data, self::FILTER_NOMIN ) !== false ) {
                        return $data;
                }

                if ( isset( $options['cache'] ) && $options['cache'] === false ) {
                        return self::applyFilter( $filter, $data );
                }

                $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
                $cache = ObjectCache::getLocalServerInstance( CACHE_ANYTHING );

                $key = $cache->makeGlobalKey(
                        'resourceloader-filter',
                        $filter,
                        self::CACHE_VERSION,
                        md5( $data )
                );

                $result = $cache->get( $key );
                if ( $result === false ) {
                        $stats->increment( "resourceloader_cache.$filter.miss" );
                        $result = self::applyFilter( $filter, $data );
                        $cache->set( $key, $result, 24 * 3600 );
                } else {
                        $stats->increment( "resourceloader_cache.$filter.hit" );
                }
                if ( $result === null ) {
                        // Cached failure
                        $result = $data;
                }

                return $result;
        }

        private static function applyFilter( $filter, $data ) {
                $data = trim( $data );
                if ( $data ) {
                        try {
                                $data = ( $filter === 'minify-css' )
                                        ? CSSMin::minify( $data )
                                        : JavaScriptMinifier::minify( $data );
                        } catch ( Exception $e ) {
                                MWExceptionHandler::logException( $e );
                                return null;
                        }
                }
                return $data;
        }

        /**
         * Register core modules and runs registration hooks.
         * @param Config|null $config
         * @param LoggerInterface|null $logger [optional]
         */
        public function __construct( Config $config = null, LoggerInterface $logger = null ) {
                $this->logger = $logger ?: new NullLogger();

                if ( !$config ) {
                        wfDeprecated( __METHOD__ . ' without a Config instance', '1.34' );
                        $config = MediaWikiServices::getInstance()->getMainConfig();
                }
                $this->config = $config;

                // Add 'local' source first
                $this->addSource( 'local', $config->get( 'LoadScript' ) );

                // Special module that always exists
                $this->register( 'startup', [ 'class' => ResourceLoaderStartUpModule::class ] );

                $this->setMessageBlobStore( new MessageBlobStore( $this, $this->logger ) );
        }

        /**
         * @return Config
         */
        public function getConfig() {
                return $this->config;
        }

        /**
         * @since 1.26
         * @param LoggerInterface $logger
         */
        public function setLogger( LoggerInterface $logger ) {
                $this->logger = $logger;
        }

        /**
         * @since 1.27
         * @return LoggerInterface
         */
        public function getLogger() {
                return $this->logger;
        }

        /**
         * @since 1.26
         * @return MessageBlobStore
         */
        public function getMessageBlobStore() {
                return $this->blobStore;
        }

        /**
         * @since 1.25
         * @param MessageBlobStore $blobStore
         */
        public function setMessageBlobStore( MessageBlobStore $blobStore ) {
                $this->blobStore = $blobStore;
        }

        /**
         * Register a module with the ResourceLoader system.
         *
         * @param string|array[] $name Module name as a string or, array of module info arrays
         *  keyed by name.
         * @param array|null $info Module info array. When using the first parameter to register
         *  multiple modules at once, this parameter is optional.
         * @throws MWException If a duplicate module registration is attempted
         * @throws MWException If a module name contains illegal characters (pipes or commas)
         * @throws InvalidArgumentException If the module info is not an array
         */
        public function register( $name, $info = null ) {
                $moduleSkinStyles = $this->config->get( 'ResourceModuleSkinStyles' );

                // Allow multiple modules to be registered in one call
                $registrations = is_array( $name ) ? $name : [ $name => $info ];
                foreach ( $registrations as $name => $info ) {
                        // Warn on duplicate registrations
                        if ( isset( $this->moduleInfos[$name] ) ) {
                                // A module has already been registered by this name
                                $this->logger->warning(
                                        'ResourceLoader duplicate registration warning. ' .
                                        'Another module has already been registered as ' . $name
                                );
                        }

                        // Check validity
                        if ( !self::isValidModuleName( $name ) ) {
                                throw new MWException( "ResourceLoader module name '$name' is invalid, "
                                        . "see ResourceLoader::isValidModuleName()" );
                        }
                        if ( !is_array( $info ) ) {
                                throw new InvalidArgumentException(
                                        'Invalid module info for "' . $name . '": expected array, got ' . gettype( $info )
                                );
                        }

                        // Attach module
                        $this->moduleInfos[$name] = $info;

                        // Last-minute changes
                        // Apply custom skin-defined styles to existing modules.
                        if ( $this->isFileModule( $name ) ) {
                                foreach ( $moduleSkinStyles as $skinName => $skinStyles ) {
                                        // If this module already defines skinStyles for this skin, ignore $wgResourceModuleSkinStyles.
                                        if ( isset( $this->moduleInfos[$name]['skinStyles'][$skinName] ) ) {
                                                continue;
                                        }

                                        // If $name is preceded with a '+', the defined style files will be added to 'default'
                                        // skinStyles, otherwise 'default' will be ignored as it normally would be.
                                        if ( isset( $skinStyles[$name] ) ) {
                                                $paths = (array)$skinStyles[$name];
                                                $styleFiles = [];
                                        } elseif ( isset( $skinStyles['+' . $name] ) ) {
                                                $paths = (array)$skinStyles['+' . $name];
                                                $styleFiles = isset( $this->moduleInfos[$name]['skinStyles']['default'] ) ?
                                                        (array)$this->moduleInfos[$name]['skinStyles']['default'] :
                                                        [];
                                        } else {
                                                continue;
                                        }

                                        // Add new file paths, remapping them to refer to our directories and not use settings
                                        // from the module we're modifying, which come from the base definition.
                                        list( $localBasePath, $remoteBasePath ) =
                                                ResourceLoaderFileModule::extractBasePaths( $skinStyles );

                                        foreach ( $paths as $path ) {
                                                $styleFiles[] = new ResourceLoaderFilePath( $path, $localBasePath, $remoteBasePath );
                                        }

                                        $this->moduleInfos[$name]['skinStyles'][$skinName] = $styleFiles;
                                }
                        }
                }
        }

        /**
         * @internal For use by ServiceWiring only
         * @codeCoverageIgnore
         */
        public function registerTestModules() {
                global $IP;

                if ( $this->config->get( 'EnableJavaScriptTest' ) !== true ) {
                        throw new MWException( 'Attempt to register JavaScript test modules '
                                . 'but <code>$wgEnableJavaScriptTest</code> is false. '
                                . 'Edit your <code>LocalSettings.php</code> to enable it.' );
                }

                // This has a 'qunit' key for compat with the below hook.
                $testModulesMeta = [ 'qunit' => [] ];

                // Get test suites from extensions
                // Avoid PHP 7.1 warning from passing $this by reference
                $rl = $this;
                Hooks::run( 'ResourceLoaderTestModules', [ &$testModulesMeta, &$rl ] );
                $extRegistry = ExtensionRegistry::getInstance();
                // In case of conflict, the deprecated hook has precedence.
                $testModules = $testModulesMeta['qunit'] + $extRegistry->getAttribute( 'QUnitTestModules' );

                $testSuiteModuleNames = [];
                foreach ( $testModules as $name => &$module ) {
                        // Turn any single-module dependency into an array
                        if ( isset( $module['dependencies'] ) && is_string( $module['dependencies'] ) ) {
                                $module['dependencies'] = [ $module['dependencies'] ];
                        }

                        // Ensure the testrunner loads before any test suites
                        $module['dependencies'][] = 'test.mediawiki.qunit.testrunner';

                        // Keep track of the test suites to load on SpecialJavaScriptTest
                        $testSuiteModuleNames[] = $name;
                }

                // Core test suites (their names have further precedence).
                $testModules = ( include "$IP/tests/qunit/QUnitTestResources.php" ) + $testModules;
                $testSuiteModuleNames[] = 'test.mediawiki.qunit.suites';

                $this->register( $testModules );
                $this->testSuiteModuleNames = $testSuiteModuleNames;
        }

        /**
         * Add a foreign source of modules.
         *
         * Source IDs are typically the same as the Wiki ID or database name (e.g. lowercase a-z).
         *
         * @param array|string $id Source ID (string), or [ id1 => loadUrl, id2 => loadUrl, ... ]
         * @param string|array|null $loadUrl load.php url (string), or array with loadUrl key for
         *  backwards-compatibility.
         * @throws MWException
         */
        public function addSource( $id, $loadUrl = null ) {
                // Allow multiple sources to be registered in one call
                if ( is_array( $id ) ) {
                        foreach ( $id as $key => $value ) {
                                $this->addSource( $key, $value );
                        }
                        return;
                }

                // Disallow duplicates
                if ( isset( $this->sources[$id] ) ) {
                        throw new MWException(
                                'ResourceLoader duplicate source addition error. ' .
                                'Another source has already been registered as ' . $id
                        );
                }

                // Pre 1.24 backwards-compatibility
                if ( is_array( $loadUrl ) ) {
                        if ( !isset( $loadUrl['loadScript'] ) ) {
                                throw new MWException(
                                        __METHOD__ . ' was passed an array with no "loadScript" key.'
                                );
                        }

                        $loadUrl = $loadUrl['loadScript'];
                }

                $this->sources[$id] = $loadUrl;
        }

        /**
         * Get a list of module names.
         *
         * @return array List of module names
         */
        public function getModuleNames() {
                return array_keys( $this->moduleInfos );
        }

        /**
         * Get a list of module names with QUnit test suites.
         *
         * @internal For use by SpecialJavaScriptTest only
         * @return array
         * @codeCoverageIgnore
         */
        public function getTestSuiteModuleNames() {
                return $this->testSuiteModuleNames;
        }

        /**
         * Check whether a ResourceLoader module is registered
         *
         * @since 1.25
         * @param string $name
         * @return bool
         */
        public function isModuleRegistered( $name ) {
                return isset( $this->moduleInfos[$name] );
        }

        /**
         * Get the ResourceLoaderModule object for a given module name.
         *
         * If an array of module parameters exists but a ResourceLoaderModule object has not
         * yet been instantiated, this method will instantiate and cache that object such that
         * subsequent calls simply return the same object.
         *
         * @param string $name Module name
         * @return ResourceLoaderModule|null If module has been registered, return a
         *  ResourceLoaderModule instance. Otherwise, return null.
         */
        public function getModule( $name ) {
                if ( !isset( $this->modules[$name] ) ) {
                        if ( !isset( $this->moduleInfos[$name] ) ) {
                                // No such module
                                return null;
                        }
                        // Construct the requested module object
                        $info = $this->moduleInfos[$name];
                        if ( isset( $info['factory'] ) ) {
                                /** @var ResourceLoaderModule $object */
                                $object = call_user_func( $info['factory'], $info );
                        } else {
                                $class = $info['class'] ?? ResourceLoaderFileModule::class;
                                /** @var ResourceLoaderModule $object */
                                $object = new $class( $info );
                        }
                        $object->setConfig( $this->getConfig() );
                        $object->setLogger( $this->logger );
                        $object->setName( $name );
                        $this->modules[$name] = $object;
                }

                return $this->modules[$name];
        }

        /**
         * Whether the module is a ResourceLoaderFileModule (including subclasses).
         *
         * @param string $name Module name
         * @return bool
         */
        protected function isFileModule( $name ) {
                if ( !isset( $this->moduleInfos[$name] ) ) {
                        return false;
                }
                $info = $this->moduleInfos[$name];
                return !isset( $info['factory'] ) && (
                        // The implied default for 'class' is ResourceLoaderFileModule
                        !isset( $info['class'] ) ||
                        // Explicit default
                        $info['class'] === ResourceLoaderFileModule::class ||
                        is_subclass_of( $info['class'], ResourceLoaderFileModule::class )
                );
        }

        /**
         * Get the list of sources.
         *
         * @return array Like [ id => load.php url, ... ]
         */
        public function getSources() {
                return $this->sources;
        }

        /**
         * Get the URL to the load.php endpoint for the given
         * ResourceLoader source
         *
         * @since 1.24
         * @param string $source
         * @throws MWException On an invalid $source name
         * @return string
         */
        public function getLoadScript( $source ) {
                if ( !isset( $this->sources[$source] ) ) {
                        throw new MWException( "The $source source was never registered in ResourceLoader." );
                }
                return $this->sources[$source];
        }

        /**
         * @internal For use by ResourceLoaderStartUpModule only.
         */
        const HASH_LENGTH = 5;

        /**
         * Create a hash for module versioning purposes.
         *
         * This hash is used in three ways:
         *
         * - To differentiate between the current version and a past version
         *   of a module by the same name.
         *
         *   In the cache key of localStorage in the browser (mw.loader.store).
         *   This store keeps only one version of any given module. As long as the
         *   next version the client encounters has a different hash from the last
         *   version it saw, it will correctly discard it in favour of a network fetch.
         *
         *   A browser may evict a site's storage container for any reason (e.g. when
         *   the user hasn't visited a site for some time, and/or when the device is
         *   low on storage space). Anecdotally it seems devices rarely keep unused
         *   storage beyond 2 weeks on mobile devices and 4 weeks on desktop.
         *   But, there is no hard limit or expiration on localStorage.
         *   ResourceLoader's Client also clears localStorage when the user changes
         *   their language preference or when they (temporarily) use Debug Mode.
         *
         *   The only hard factors that reduce the range of possible versions are
         *   1) the name and existence of a given module, and
         *   2) the TTL for mw.loader.store, and
         *   3) the `$wgResourceLoaderStorageVersion` configuration variable.
         *
         * - To identify a batch response of modules from load.php in an HTTP cache.
         *
         *   When fetching modules in a batch from load.php, a combined hash
         *   is created by the JS code, and appended as query parameter.
         *
         *   In cache proxies (e.g. Varnish, Nginx) and in the browser's HTTP cache,
         *   these urls are used to identify other previously cached responses.
         *   The range of possible versions a given version has to be unique amongst
         *   is determined by the maximum duration each response is stored for, which
         *   is controlled by `$wgResourceLoaderMaxage['versioned']`.
         *
         * - To detect race conditions between multiple web servers in a MediaWiki
         *   deployment of which some have the newer version and some still the older
         *   version.
         *
         *   An HTTP request from a browser for the Startup manifest may be responded
         *   to by a server with the newer version. The browser may then use that to
         *   request a given module, which may then be responded to by a server with
         *   the older version. To avoid caching this for too long (which would pollute
         *   all other users without repairing itself), the combined hash that the JS
         *   client adds to the url is verified by the server (in ::sendResponseHeaders).
         *   If they don't match, we instruct cache proxies and clients to not cache
         *   this response as long as they normally would. This is also the reason
         *   that the algorithm used here in PHP must match the one used in JS.
         *
         * The fnv132 digest creates a 32-bit integer, which goes upto 4 Giga and
         * needs up to 7 chars in base 36.
         * Within 7 characters, base 36 can count up to 78,364,164,096 (78 Giga),
         * (but with fnv132 we'd use very little of this range, mostly padding).
         * Within 6 characters, base 36 can count up to 2,176,782,336 (2 Giga).
         * Within 5 characters, base 36 can count up to 60,466,176 (60 Mega).
         *
         * @since 1.26
         * @param string $value
         * @return string Hash
         */
        public static function makeHash( $value ) {
                $hash = hash( 'fnv132', $value );
                // The base_convert will pad it (if too short),
                // then substr() will trim it (if too long).
                return substr(
                        Wikimedia\base_convert( $hash, 16, 36, self::HASH_LENGTH ),
                        0,
                        self::HASH_LENGTH
                );
        }

        /**
         * Add an error to the 'errors' array and log it.
         *
         * @private For internal use by ResourceLoader and ResourceLoaderStartUpModule.
         * @since 1.29
         * @param Exception $e
         * @param string $msg
         * @param array $context
         */
        public function outputErrorAndLog( Exception $e, $msg, array $context = [] ) {
                MWExceptionHandler::logException( $e );
                $this->logger->warning(
                        $msg,
                        $context + [ 'exception' => $e ]
                );
                $this->errors[] = self::formatExceptionNoComment( $e );
        }

        /**
         * Helper method to get and combine versions of multiple modules.
         *
         * @since 1.26
         * @param ResourceLoaderContext $context
         * @param string[] $moduleNames List of known module names
         * @return string Hash
         */
        public function getCombinedVersion( ResourceLoaderContext $context, array $moduleNames ) {
                if ( !$moduleNames ) {
                        return '';
                }
                $hashes = array_map( function ( $module ) use ( $context ) {
                        try {
                                return $this->getModule( $module )->getVersionHash( $context );
                        } catch ( Exception $e ) {
                                // If modules fail to compute a version, don't fail the request (T152266)
                                // and still compute versions of other modules.
                                $this->outputErrorAndLog( $e,
                                        'Calculating version for "{module}" failed: {exception}',
                                        [
                                                'module' => $module,
                                        ]
                                );
                                return '';
                        }
                }, $moduleNames );
                return self::makeHash( implode( '', $hashes ) );
        }

        /**
         * Get the expected value of the 'version' query parameter.
         *
         * This is used by respond() to set a short Cache-Control header for requests with
         * information newer than the current server has. This avoids pollution of edge caches.
         * Typically during deployment. (T117587)
         *
         * This MUST match return value of `mw.loader#getCombinedVersion()` client-side.
         *
         * @since 1.28
         * @param ResourceLoaderContext $context
         * @return string Hash
         */
        public function makeVersionQuery( ResourceLoaderContext $context ) {
                // As of MediaWiki 1.28, the server and client use the same algorithm for combining
                // version hashes. There is no technical reason for this to be same, and for years the
                // implementations differed. If getCombinedVersion in PHP (used for StartupModule and
                // E-Tag headers) differs in the future from getCombinedVersion in JS (used for 'version'
                // query parameter), then this method must continue to match the JS one.
                $moduleNames = [];
                foreach ( $context->getModules() as $name ) {
                        if ( !$this->getModule( $name ) ) {
                                // If a versioned request contains a missing module, the version is a mismatch
                                // as the client considered a module (and version) we don't have.
                                return '';
                        }
                        $moduleNames[] = $name;
                }
                return $this->getCombinedVersion( $context, $moduleNames );
        }

        /**
         * Output a response to a load request, including the content-type header.
         *
         * @param ResourceLoaderContext $context Context in which a response should be formed
         */
        public function respond( ResourceLoaderContext $context ) {
                // Buffer output to catch warnings. Normally we'd use ob_clean() on the
                // top-level output buffer to clear warnings, but that breaks when ob_gzhandler
                // is used: ob_clean() will clear the GZIP header in that case and it won't come
                // back for subsequent output, resulting in invalid GZIP. So we have to wrap
                // the whole thing in our own output buffer to be sure the active buffer
                // doesn't use ob_gzhandler.
                // See https://bugs.php.net/bug.php?id=36514
                ob_start();

                $this->measureResponseTime( RequestContext::getMain()->getTiming() );

                // Find out which modules are missing and instantiate the others
                $modules = [];
                $missing = [];
                foreach ( $context->getModules() as $name ) {
                        $module = $this->getModule( $name );
                        if ( $module ) {
                                // Do not allow private modules to be loaded from the web.
                                // This is a security issue, see T36907.
                                if ( $module->getGroup() === 'private' ) {
                                        // Not a serious error, just means something is trying to access it (T101806)
                                        $this->logger->debug( "Request for private module '$name' denied" );
                                        $this->errors[] = "Cannot build private module \"$name\"";
                                        continue;
                                }
                                $modules[$name] = $module;
                        } else {
                                $missing[] = $name;
                        }
                }

                try {
                        // Preload for getCombinedVersion() and for batch makeModuleResponse()
                        $this->preloadModuleInfo( array_keys( $modules ), $context );
                } catch ( Exception $e ) {
                        $this->outputErrorAndLog( $e, 'Preloading module info failed: {exception}' );
                }

                // Combine versions to propagate cache invalidation
                $versionHash = '';
                try {
                        $versionHash = $this->getCombinedVersion( $context, array_keys( $modules ) );
                } catch ( Exception $e ) {
                        $this->outputErrorAndLog( $e, 'Calculating version hash failed: {exception}' );
                }

                // See RFC 2616 § 3.11 Entity Tags
                // https://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.11
                $etag = 'W/"' . $versionHash . '"';

                // Try the client-side cache first
                if ( $this->tryRespondNotModified( $context, $etag ) ) {
                        return; // output handled (buffers cleared)
                }

                // Use file cache if enabled and available...
                if ( $this->config->get( 'UseFileCache' ) ) {
                        $fileCache = ResourceFileCache::newFromContext( $context );
                        if ( $this->tryRespondFromFileCache( $fileCache, $context, $etag ) ) {
                                return; // output handled
                        }
                } else {
                        $fileCache = null;
                }

                // Generate a response
                $response = $this->makeModuleResponse( $context, $modules, $missing );

                // Capture any PHP warnings from the output buffer and append them to the
                // error list if we're in debug mode.
                if ( $context->getDebug() ) {
                        $warnings = ob_get_contents();
                        if ( strlen( $warnings ) ) {
                                $this->errors[] = $warnings;
                        }
                }

                // Consider saving the response to file cache (unless there are errors).
                if ( $fileCache &&
                        !$this->errors &&
                        $missing === [] &&
                        ResourceFileCache::useFileCache( $context )
                ) {
                        if ( $fileCache->isCacheWorthy() ) {
                                // There were enough hits, save the response to the cache
                                $fileCache->saveText( $response );
                        } else {
                                $fileCache->incrMissesRecent( $context->getRequest() );
                        }
                }

                $this->sendResponseHeaders( $context, $etag, (bool)$this->errors, $this->extraHeaders );

                // Remove the output buffer and output the response
                ob_end_clean();

                if ( $context->getImageObj() && $this->errors ) {
                        // We can't show both the error messages and the response when it's an image.
                        $response = implode( "\n\n", $this->errors );
                } elseif ( $this->errors ) {
                        $errorText = implode( "\n\n", $this->errors );
                        $errorResponse = self::makeComment( $errorText );
                        if ( $context->shouldIncludeScripts() ) {
                                $errorResponse .= 'if (window.console && console.error) {'
                                        . Xml::encodeJsCall( 'console.error', [ $errorText ] )
                                        . "}\n";
                        }

                        // Prepend error info to the response
                        $response = $errorResponse . $response;
                }

                $this->errors = [];
                echo $response;
        }

        protected function measureResponseTime( Timing $timing ) {
                DeferredUpdates::addCallableUpdate( function () use ( $timing ) {
                        $measure = $timing->measure( 'responseTime', 'requestStart', 'requestShutdown' );
                        if ( $measure !== false ) {
                                $stats = MediaWikiServices::getInstance()->getStatsdDataFactory();
                                $stats->timing( 'resourceloader.responseTime', $measure['duration'] * 1000 );
                        }
                } );
        }

        /**
         * Send main response headers to the client.
         *
         * Deals with Content-Type, CORS (for stylesheets), and caching.
         *
         * @param ResourceLoaderContext $context
         * @param string $etag ETag header value
         * @param bool $errors Whether there are errors in the response
         * @param string[] $extra Array of extra HTTP response headers
         * @return void
         */
        protected function sendResponseHeaders(
                ResourceLoaderContext $context, $etag, $errors, array $extra = []
        ) {
                \MediaWiki\HeaderCallback::warnIfHeadersSent();
                $rlMaxage = $this->config->get( 'ResourceLoaderMaxage' );
                // Use a short cache expiry so that updates propagate to clients quickly, if:
                // - No version specified (shared resources, e.g. stylesheets)
                // - There were errors (recover quickly)
                // - Version mismatch (T117587, T47877)
                if ( is_null( $context->getVersion() )
                        || $errors
                        || $context->getVersion() !== $this->makeVersionQuery( $context )
                ) {
                        $maxage = $rlMaxage['unversioned']['client'];
                        $smaxage = $rlMaxage['unversioned']['server'];
                // If a version was specified we can use a longer expiry time since changing
                // version numbers causes cache misses
                } else {
                        $maxage = $rlMaxage['versioned']['client'];
                        $smaxage = $rlMaxage['versioned']['server'];
                }
                if ( $context->getImageObj() ) {
                        // Output different headers if we're outputting textual errors.
                        if ( $errors ) {
                                header( 'Content-Type: text/plain; charset=utf-8' );
                        } else {
                                $context->getImageObj()->sendResponseHeaders( $context );
                        }
                } elseif ( $context->getOnly() === 'styles' ) {
                        header( 'Content-Type: text/css; charset=utf-8' );
                        header( 'Access-Control-Allow-Origin: *' );
                } else {
                        header( 'Content-Type: text/javascript; charset=utf-8' );
                }
                // See RFC 2616 § 14.19 ETag
                // https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.19
                header( 'ETag: ' . $etag );
                if ( $context->getDebug() ) {
                        // Do not cache debug responses
                        header( 'Cache-Control: private, no-cache, must-revalidate' );
                        header( 'Pragma: no-cache' );
                } else {
                        header( "Cache-Control: public, max-age=$maxage, s-maxage=$smaxage" );
                        $exp = min( $maxage, $smaxage );
                        header( 'Expires: ' . wfTimestamp( TS_RFC2822, $exp + time() ) );
                }
                foreach ( $extra as $header ) {
                        header( $header );
                }
        }

        /**
         * Respond with HTTP 304 Not Modified if appropiate.
         *
         * If there's an If-None-Match header, respond with a 304 appropriately
         * and clear out the output buffer. If the client cache is too old then do nothing.
         *
         * @param ResourceLoaderContext $context
         * @param string $etag ETag header value
         * @return bool True if HTTP 304 was sent and output handled
         */
        protected function tryRespondNotModified( ResourceLoaderContext $context, $etag ) {
                // See RFC 2616 § 14.26 If-None-Match
                // https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.26
                $clientKeys = $context->getRequest()->getHeader( 'If-None-Match', WebRequest::GETHEADER_LIST );
                // Never send 304s in debug mode
                if ( $clientKeys !== false && !$context->getDebug() && in_array( $etag, $clientKeys ) ) {
                        // There's another bug in ob_gzhandler (see also the comment at
                        // the top of this function) that causes it to gzip even empty
                        // responses, meaning it's impossible to produce a truly empty
                        // response (because the gzip header is always there). This is
                        // a problem because 304 responses have to be completely empty
                        // per the HTTP spec, and Firefox behaves buggily when they're not.
                        // See also https://bugs.php.net/bug.php?id=51579
                        // To work around this, we tear down all output buffering before
                        // sending the 304.
                        wfResetOutputBuffers( /* $resetGzipEncoding = */ true );

                        HttpStatus::header( 304 );

                        $this->sendResponseHeaders( $context, $etag, false );
                        return true;
                }
                return false;
        }

        /**
         * Send out code for a response from file cache if possible.
         *
         * @param ResourceFileCache $fileCache Cache object for this request URL
         * @param ResourceLoaderContext $context Context in which to generate a response
         * @param string $etag ETag header value
         * @return bool If this found a cache file and handled the response
         */
        protected function tryRespondFromFileCache(
                ResourceFileCache $fileCache,
                ResourceLoaderContext $context,
                $etag
        ) {
                $rlMaxage = $this->config->get( 'ResourceLoaderMaxage' );
                // Buffer output to catch warnings.
                ob_start();
                // Get the maximum age the cache can be
                $maxage = is_null( $context->getVersion() )
                        ? $rlMaxage['unversioned']['server']
                        : $rlMaxage['versioned']['server'];
                // Minimum timestamp the cache file must have
                $good = $fileCache->isCacheGood( wfTimestamp( TS_MW, time() - $maxage ) );
                if ( !$good ) {
                        try { // RL always hits the DB on file cache miss...
                                wfGetDB( DB_REPLICA );
                        } catch ( DBConnectionError $e ) { // ...check if we need to fallback to cache
                                $good = $fileCache->isCacheGood(); // cache existence check
                        }
                }
                if ( $good ) {
                        $ts = $fileCache->cacheTimestamp();
                        // Send content type and cache headers
                        $this->sendResponseHeaders( $context, $etag, false );
                        $response = $fileCache->fetchText();
                        // Capture any PHP warnings from the output buffer and append them to the
                        // response in a comment if we're in debug mode.
                        if ( $context->getDebug() ) {
                                $warnings = ob_get_contents();
                                if ( strlen( $warnings ) ) {
                                        $response = self::makeComment( $warnings ) . $response;
                                }
                        }
                        // Remove the output buffer and output the response
                        ob_end_clean();
                        echo $response . "\n/* Cached {$ts} */";
                        return true; // cache hit
                }
                // Clear buffer
                ob_end_clean();

                return false; // cache miss
        }

        /**
         * Generate a CSS or JS comment block.
         *
         * Only use this for public data, not error message details.
         *
         * @param string $text
         * @return string
         */
        public static function makeComment( $text ) {
                $encText = str_replace( '*/', '* /', $text );
                return "/*\n$encText\n*/\n";
        }

        /**
         * Handle exception display.
         *
         * @param Exception $e Exception to be shown to the user
         * @return string Sanitized text in a CSS/JS comment that can be returned to the user
         */
        public static function formatException( $e ) {
                return self::makeComment( self::formatExceptionNoComment( $e ) );
        }

        /**
         * Handle exception display.
         *
         * @since 1.25
         * @param Exception $e Exception to be shown to the user
         * @return string Sanitized text that can be returned to the user
         */
        protected static function formatExceptionNoComment( $e ) {
                global $wgShowExceptionDetails;

                if ( !$wgShowExceptionDetails ) {
                        return MWExceptionHandler::getPublicLogMessage( $e );
                }

                return MWExceptionHandler::getLogMessage( $e ) .
                        "\nBacktrace:\n" .
                        MWExceptionHandler::getRedactedTraceAsString( $e );
        }

        /**
         * Generate code for a response.
         *
         * Calling this method also populates the `errors` and `headers` members,
         * later used by respond().
         *
         * @param ResourceLoaderContext $context Context in which to generate a response
         * @param ResourceLoaderModule[] $modules List of module objects keyed by module name
         * @param string[] $missing List of requested module names that are unregistered (optional)
         * @return string Response data
         */
        public function makeModuleResponse( ResourceLoaderContext $context,
                array $modules, array $missing = []
        ) {
                $out = '';
                $states = [];

                if ( $modules === [] && $missing === [] ) {
                        return <<<MESSAGE
/* This file is the Web entry point for MediaWiki's ResourceLoader:
   <https://www.mediawiki.org/wiki/ResourceLoader>. In this request,
   no modules were requested. Max made me put this here. */
MESSAGE;
                }

                $image = $context->getImageObj();
                if ( $image ) {
                        $data = $image->getImageData( $context );
                        if ( $data === false ) {
                                $data = '';
                                $this->errors[] = 'Image generation failed';
                        }
                        return $data;
                }

                foreach ( $missing as $name ) {
                        $states[$name] = 'missing';
                }

                $filter = $context->getOnly() === 'styles' ? 'minify-css' : 'minify-js';

                foreach ( $modules as $name => $module ) {
                        try {
                                $content = $module->getModuleContent( $context );
                                $implementKey = $name . '@' . $module->getVersionHash( $context );
                                $strContent = '';

                                if ( isset( $content['headers'] ) ) {
                                        $this->extraHeaders = array_merge( $this->extraHeaders, $content['headers'] );
                                }

                                // Append output
                                switch ( $context->getOnly() ) {
                                        case 'scripts':
                                                $scripts = $content['scripts'];
                                                if ( is_string( $scripts ) ) {
                                                        // Load scripts raw...
                                                        $strContent = $scripts;
                                                } elseif ( is_array( $scripts ) ) {
                                                        // ...except when $scripts is an array of URLs or an associative array
                                                        $strContent = self::makeLoaderImplementScript( $implementKey, $scripts, [], [], [] );
                                                }
                                                break;
                                        case 'styles':
                                                $styles = $content['styles'];
                                                // We no longer separate into media, they are all combined now with
                                                // custom media type groups into @media .. {} sections as part of the css string.
                                                // Module returns either an empty array or a numerical array with css strings.
                                                $strContent = isset( $styles['css'] ) ? implode( '', $styles['css'] ) : '';
                                                break;
                                        default:
                                                $scripts = $content['scripts'] ?? '';
                                                if ( is_string( $scripts ) ) {
                                                        if ( $name === 'site' || $name === 'user' ) {
                                                                // Legacy scripts that run in the global scope without a closure.
                                                                // mw.loader.implement will use globalEval if scripts is a string.
                                                                // Minify manually here, because general response minification is
                                                                // not effective due it being a string literal, not a function.
                                                                if ( !$context->getDebug() ) {
                                                                        $scripts = self::filter( 'minify-js', $scripts ); // T107377
                                                                }
                                                        } else {
                                                                $scripts = new XmlJsCode( $scripts );
                                                        }
                                                }
                                                $strContent = self::makeLoaderImplementScript(
                                                        $implementKey,
                                                        $scripts,
                                                        $content['styles'] ?? [],
                                                        isset( $content['messagesBlob'] ) ? new XmlJsCode( $content['messagesBlob'] ) : [],
                                                        $content['templates'] ?? []
                                                );
                                                break;
                                }

                                if ( !$context->getDebug() ) {
                                        $strContent = self::filter( $filter, $strContent );
                                } else {
                                        // In debug mode, separate each response by a new line.
                                        // For example, between 'mw.loader.implement();' statements.
                                        $strContent = $this->ensureNewline( $strContent );
                                }

                                if ( $context->getOnly() === 'scripts' ) {
                                        // Use a linebreak between module scripts (T162719)
                                        $out .= $this->ensureNewline( $strContent );
                                } else {
                                        $out .= $strContent;
                                }

                        } catch ( Exception $e ) {
                                $this->outputErrorAndLog( $e, 'Generating module package failed: {exception}' );

                                // Respond to client with error-state instead of module implementation
                                $states[$name] = 'error';
                                unset( $modules[$name] );
                        }
                }

                // Update module states
                if ( $context->shouldIncludeScripts() && !$context->getRaw() ) {
                        if ( $modules && $context->getOnly() === 'scripts' ) {
                                // Set the state of modules loaded as only scripts to ready as
                                // they don't have an mw.loader.implement wrapper that sets the state
                                foreach ( $modules as $name => $module ) {
                                        $states[$name] = 'ready';
                                }
                        }

                        // Set the state of modules we didn't respond to with mw.loader.implement
                        if ( $states ) {
                                $stateScript = self::makeLoaderStateScript( $states );
                                if ( !$context->getDebug() ) {
                                        $stateScript = self::filter( 'minify-js', $stateScript );
                                }
                                // Use a linebreak between module script and state script (T162719)
                                $out = $this->ensureNewline( $out ) . $stateScript;
                        }
                } elseif ( $states ) {
                        $this->errors[] = 'Problematic modules: '
                                . self::encodeJsonForScript( $states );
                }

                return $out;
        }

        /**
         * Ensure the string is either empty or ends in a line break
         * @param string $str
         * @return string
         */
        private function ensureNewline( $str ) {
                $end = substr( $str, -1 );
                if ( $end === false || $end === '' || $end === "\n" ) {
                        return $str;
                }
                return $str . "\n";
        }

        /**
         * Get names of modules that use a certain message.
         *
         * @param string $messageKey
         * @return array List of module names
         */
        public function getModulesByMessage( $messageKey ) {
                $moduleNames = [];
                foreach ( $this->getModuleNames() as $moduleName ) {
                        $module = $this->getModule( $moduleName );
                        if ( in_array( $messageKey, $module->getMessages() ) ) {
                                $moduleNames[] = $moduleName;
                        }
                }
                return $moduleNames;
        }

        /**
         * Return JS code that calls mw.loader.implement with given module properties.
         *
         * @param string $name Module name or implement key (format "`[name]@[version]`")
         * @param XmlJsCode|array|string $scripts Code as XmlJsCode (to be wrapped in a closure),
         *  list of URLs to JavaScript files, string of JavaScript for `$.globalEval`, or array with
         *  'files' and 'main' properties (see ResourceLoaderModule::getScript())
         * @param mixed $styles Array of CSS strings keyed by media type, or an array of lists of URLs
         *   to CSS files keyed by media type
         * @param mixed $messages List of messages associated with this module. May either be an
         *   associative array mapping message key to value, or a JSON-encoded message blob containing
         *   the same data, wrapped in an XmlJsCode object.
         * @param array $templates Keys are name of templates and values are the source of
         *   the template.
         * @throws MWException
         * @return string JavaScript code
         */
        protected static function makeLoaderImplementScript(
                $name, $scripts, $styles, $messages, $templates
        ) {
                if ( $scripts instanceof XmlJsCode ) {
                        if ( $scripts->value === '' ) {
                                $scripts = null;
                        } elseif ( self::inDebugMode() ) {
                                $scripts = new XmlJsCode( "function ( $, jQuery, require, module ) {\n{$scripts->value}\n}" );
                        } else {
                                $scripts = new XmlJsCode( 'function($,jQuery,require,module){' . $scripts->value . '}' );
                        }
                } elseif ( is_array( $scripts ) && isset( $scripts['files'] ) ) {
                        $files = $scripts['files'];
                        foreach ( $files as $path => &$file ) {
                                // $file is changed (by reference) from a descriptor array to the content of the file
                                // All of these essentially do $file = $file['content'];, some just have wrapping around it
                                if ( $file['type'] === 'script' ) {
                                        // Multi-file modules only get two parameters ($ and jQuery are being phased out)
                                        if ( self::inDebugMode() ) {
                                                $file = new XmlJsCode( "function ( require, module ) {\n{$file['content']}\n}" );
                                        } else {
                                                $file = new XmlJsCode( 'function(require,module){' . $file['content'] . '}' );
                                        }
                                } else {
                                        $file = $file['content'];
                                }
                        }
                        $scripts = XmlJsCode::encodeObject( [
                                'main' => $scripts['main'],
                                'files' => XmlJsCode::encodeObject( $files, self::inDebugMode() )
                        ], self::inDebugMode() );
                } elseif ( !is_string( $scripts ) && !is_array( $scripts ) ) {
                        throw new MWException( 'Invalid scripts error. Array of URLs or string of code expected.' );
                }

                // mw.loader.implement requires 'styles', 'messages' and 'templates' to be objects (not
                // arrays). json_encode considers empty arrays to be numerical and outputs "[]" instead
                // of "{}". Force them to objects.
                $module = [
                        $name,
                        $scripts,
                        (object)$styles,
                        (object)$messages,
                        (object)$templates
                ];
                self::trimArray( $module );

                return Xml::encodeJsCall( 'mw.loader.implement', $module, self::inDebugMode() );
        }

        /**
         * Returns JS code which, when called, will register a given list of messages.
         *
         * @param mixed $messages Either an associative array mapping message key to value, or a
         *   JSON-encoded message blob containing the same data, wrapped in an XmlJsCode object.
         * @return string JavaScript code
         */
        public static function makeMessageSetScript( $messages ) {
                return 'mw.messages.set('
                        . self::encodeJsonForScript( (object)$messages )
                        . ');';
        }

        /**
         * Combines an associative array mapping media type to CSS into a
         * single stylesheet with "@media" blocks.
         *
         * @param array $stylePairs Array keyed by media type containing (arrays of) CSS strings
         * @return array
         */
        public static function makeCombinedStyles( array $stylePairs ) {
                $out = [];
                foreach ( $stylePairs as $media => $styles ) {
                        // ResourceLoaderFileModule::getStyle can return the styles
                        // as a string or an array of strings. This is to allow separation in
                        // the front-end.
                        $styles = (array)$styles;
                        foreach ( $styles as $style ) {
                                $style = trim( $style );
                                // Don't output an empty "@media print { }" block (T42498)
                                if ( $style !== '' ) {
                                        // Transform the media type based on request params and config
                                        // The way that this relies on $wgRequest to propagate request params is slightly evil
                                        $media = OutputPage::transformCssMedia( $media );

                                        if ( $media === '' || $media == 'all' ) {
                                                $out[] = $style;
                                        } elseif ( is_string( $media ) ) {
                                                $out[] = "@media $media {\n" . str_replace( "\n", "\n\t", "\t" . $style ) . "}";
                                        }
                                        // else: skip
                                }
                        }
                }
                return $out;
        }

        /**
         * Wrapper around json_encode that avoids needless escapes,
         * and pretty-prints in debug mode.
         *
         * @internal
         * @since 1.32
         * @param mixed $data
         * @return string JSON
         */
        public static function encodeJsonForScript( $data ) {
                // Keep output as small as possible by disabling needless escape modes
                // that PHP uses by default.
                // However, while most module scripts are only served on HTTP responses
                // for JavaScript, some modules can also be embedded in the HTML as inline
                // scripts. This, and the fact that we sometimes need to export strings
                // containing user-generated content and labels that may genuinely contain
                // a sequences like "</script>", we need to encode either '/' or '<'.
                // By default PHP escapes '/'. Let's escape '<' instead which is less common
                // and allows URLs to mostly remain readable.
                $jsonFlags = JSON_UNESCAPED_SLASHES |
                        JSON_UNESCAPED_UNICODE |
                        JSON_HEX_TAG |
                        JSON_HEX_AMP;
                if ( self::inDebugMode() ) {
                        $jsonFlags |= JSON_PRETTY_PRINT;
                }
                return json_encode( $data, $jsonFlags );
        }

        /**
         * Returns a JS call to mw.loader.state, which sets the state of one
         * ore more modules to a given value. Has two calling conventions:
         *
         *    - ResourceLoader::makeLoaderStateScript( $name, $state ):
         *         Set the state of a single module called $name to $state
         *
         *    - ResourceLoader::makeLoaderStateScript( [ $name => $state, ... ] ):
         *         Set the state of modules with the given names to the given states
         *
         * @param array|string $states
         * @param string|null $state
         * @return string JavaScript code
         */
        public static function makeLoaderStateScript( $states, $state = null ) {
                if ( !is_array( $states ) ) {
                        $states = [ $states => $state ];
                }
                return 'mw.loader.state('
                        . self::encodeJsonForScript( $states )
                        . ');';
        }

        private static function isEmptyObject( stdClass $obj ) {
                foreach ( $obj as $key => $value ) {
                        return false;
                }
                return true;
        }

        /**
         * Remove empty values from the end of an array.
         *
         * Values considered empty:
         *
         * - null
         * - []
         * - new XmlJsCode( '{}' )
         * - new stdClass() // (object) []
         *
         * @param array $array
         */
        private static function trimArray( array &$array ) {
                $i = count( $array );
                while ( $i-- ) {
                        if ( $array[$i] === null
                                || $array[$i] === []
                                || ( $array[$i] instanceof XmlJsCode && $array[$i]->value === '{}' )
                                || ( $array[$i] instanceof stdClass && self::isEmptyObject( $array[$i] ) )
                        ) {
                                unset( $array[$i] );
                        } else {
                                break;
                        }
                }
        }

        /**
         * Returns JS code which calls mw.loader.register with the given
         * parameter.
         *
         * @par Example
         * @code
         *
         *     ResourceLoader::makeLoaderRegisterScript( [
         *        [ $name1, $version1, $dependencies1, $group1, $source1, $skip1 ],
         *        [ $name2, $version2, $dependencies1, $group2, $source2, $skip2 ],
         *        ...
         *     ] ):
         * @endcode
         *
         * @internal
         * @since 1.32
         * @param array $modules Array of module registration arrays, each containing
         *  - string: module name
         *  - string: module version
         *  - array|null: List of dependencies (optional)
         *  - string|null: Module group (optional)
         *  - string|null: Name of foreign module source, or 'local' (optional)
         *  - string|null: Script body of a skip function (optional)
         * @return string JavaScript code
         */
        public static function makeLoaderRegisterScript( array $modules ) {
                // Optimisation: Transform dependency names into indexes when possible
                // to produce smaller output. They are expanded by mw.loader.register on
                // the other end using resolveIndexedDependencies().
                $index = [];
                foreach ( $modules as $i => &$module ) {
                        // Build module name index
                        $index[$module[0]] = $i;
                }
                foreach ( $modules as &$module ) {
                        if ( isset( $module[2] ) ) {
                                foreach ( $module[2] as &$dependency ) {
                                        if ( isset( $index[$dependency] ) ) {
                                                // Replace module name in dependency list with index
                                                $dependency = $index[$dependency];
                                        }
                                }
                        }
                }

                array_walk( $modules, [ self::class, 'trimArray' ] );

                return 'mw.loader.register('
                        . self::encodeJsonForScript( $modules )
                        . ');';
        }

        /**
         * Returns JS code which calls mw.loader.addSource() with the given
         * parameters. Has two calling conventions:
         *
         *   - ResourceLoader::makeLoaderSourcesScript( $id, $properties ):
         *       Register a single source
         *
         *   - ResourceLoader::makeLoaderSourcesScript( [ $id1 => $loadUrl, $id2 => $loadUrl, ... ] );
         *       Register sources with the given IDs and properties.
         *
         * @param string|array $sources Source ID
         * @param string|null $loadUrl load.php url
         * @return string JavaScript code
         */
        public static function makeLoaderSourcesScript( $sources, $loadUrl = null ) {
                if ( !is_array( $sources ) ) {
                        $sources = [ $sources => $loadUrl ];
                }
                return 'mw.loader.addSource('
                        . self::encodeJsonForScript( $sources )
                        . ');';
        }

        /**
         * Wraps JavaScript code to run after the startup module.
         *
         * @param string $script JavaScript code
         * @return string JavaScript code
         */
        public static function makeLoaderConditionalScript( $script ) {
                // Adds a function to lazy-created RLQ
                return '(RLQ=window.RLQ||[]).push(function(){' .
                        trim( $script ) . '});';
        }

        /**
         * Wraps JavaScript code to run after a required module.
         *
         * @since 1.32
         * @param string|string[] $modules Module name(s)
         * @param string $script JavaScript code
         * @return string JavaScript code
         */
        public static function makeInlineCodeWithModule( $modules, $script ) {
                // Adds an array to lazy-created RLQ
                return '(RLQ=window.RLQ||[]).push(['
                        . self::encodeJsonForScript( $modules ) . ','
                        . 'function(){' . trim( $script ) . '}'
                        . ']);';
        }

        /**
         * Returns an HTML script tag that runs given JS code after startup and base modules.
         *
         * The code will be wrapped in a closure, and it will be executed by ResourceLoader's
         * startup module if the client has adequate support for MediaWiki JavaScript code.
         *
         * @param string $script JavaScript code
         * @param string|null $nonce [optional] Content-Security-Policy nonce
         *  (from OutputPage::getCSPNonce)
         * @return string|WrappedString HTML
         */
        public static function makeInlineScript( $script, $nonce = null ) {
                $js = self::makeLoaderConditionalScript( $script );
                $escNonce = '';
                if ( $nonce === null ) {
                        wfWarn( __METHOD__ . " did not get nonce. Will break CSP" );
                } elseif ( $nonce !== false ) {
                        // If it was false, CSP is disabled, so no nonce attribute.
                        // Nonce should be only base64 characters, so should be safe,
                        // but better to be safely escaped than sorry.
                        $escNonce = ' nonce="' . htmlspecialchars( $nonce ) . '"';
                }

                return new WrappedString(
                        Html::inlineScript( $js, $nonce ),
                        "<script$escNonce>(RLQ=window.RLQ||[]).push(function(){",
                        '});</script>'
                );
        }

        /**
         * Returns JS code which will set the MediaWiki configuration array to
         * the given value.
         *
         * @param array $configuration List of configuration values keyed by variable name
         * @return string JavaScript code
         * @throws Exception
         */
        public static function makeConfigSetScript( array $configuration ) {
                $js = Xml::encodeJsCall(
                        'mw.config.set',
                        [ $configuration ],
                        self::inDebugMode()
                );
                if ( $js === false ) {
                        $e = new Exception(
                                'JSON serialization of config data failed. ' .
                                'This usually means the config data is not valid UTF-8.'
                        );
                        MWExceptionHandler::logException( $e );
                        $js = Xml::encodeJsCall( 'mw.log.error', [ $e->__toString() ] );
                }
                return $js;
        }

        /**
         * Convert an array of module names to a packed query string.
         *
         * For example, `[ 'foo.bar', 'foo.baz', 'bar.baz', 'bar.quux' ]`
         * becomes `'foo.bar,baz|bar.baz,quux'`.
         *
         * This process is reversed by ResourceLoader::expandModuleNames().
         * See also mw.loader#buildModulesString() which is a port of this, used
         * on the client-side.
         *
         * @param array $modules List of module names (strings)
         * @return string Packed query string
         */
        public static function makePackedModulesString( $modules ) {
                $moduleMap = []; // [ prefix => [ suffixes ] ]
                foreach ( $modules as $module ) {
                        $pos = strrpos( $module, '.' );
                        $prefix = $pos === false ? '' : substr( $module, 0, $pos );
                        $suffix = $pos === false ? $module : substr( $module, $pos + 1 );
                        $moduleMap[$prefix][] = $suffix;
                }

                $arr = [];
                foreach ( $moduleMap as $prefix => $suffixes ) {
                        $p = $prefix === '' ? '' : $prefix . '.';
                        $arr[] = $p . implode( ',', $suffixes );
                }
                return implode( '|', $arr );
        }

        /**
         * Expand a string of the form `jquery.foo,bar|jquery.ui.baz,quux` to
         * an array of module names like `[ 'jquery.foo', 'jquery.bar',
         * 'jquery.ui.baz', 'jquery.ui.quux' ]`.
         *
         * This process is reversed by ResourceLoader::makePackedModulesString().
         *
         * @since 1.33
         * @param string $modules Packed module name list
         * @return array Array of module names
         */
        public static function expandModuleNames( $modules ) {
                $retval = [];
                $exploded = explode( '|', $modules );
                foreach ( $exploded as $group ) {
                        if ( strpos( $group, ',' ) === false ) {
                                // This is not a set of modules in foo.bar,baz notation
                                // but a single module
                                $retval[] = $group;
                        } else {
                                // This is a set of modules in foo.bar,baz notation
                                $pos = strrpos( $group, '.' );
                                if ( $pos === false ) {
                                        // Prefixless modules, i.e. without dots
                                        $retval = array_merge( $retval, explode( ',', $group ) );
                                } else {
                                        // We have a prefix and a bunch of suffixes
                                        $prefix = substr( $group, 0, $pos ); // 'foo'
                                        $suffixes = explode( ',', substr( $group, $pos + 1 ) ); // [ 'bar', 'baz' ]
                                        foreach ( $suffixes as $suffix ) {
                                                $retval[] = "$prefix.$suffix";
                                        }
                                }
                        }
                }
                return $retval;
        }

        /**
         * Determine whether debug mode was requested
         * Order of priority is 1) request param, 2) cookie, 3) $wg setting
         * @return bool
         */
        public static function inDebugMode() {
                if ( self::$debugMode === null ) {
                        global $wgRequest, $wgResourceLoaderDebug;
                        self::$debugMode = $wgRequest->getFuzzyBool( 'debug',
                                $wgRequest->getCookie( 'resourceLoaderDebug', '', $wgResourceLoaderDebug )
                        );
                }
                return self::$debugMode;
        }

        /**
         * Reset static members used for caching.
         *
         * Global state and $wgRequest are evil, but we're using it right
         * now and sometimes we need to be able to force ResourceLoader to
         * re-evaluate the context because it has changed (e.g. in the test suite).
         *
         * @internal For use by unit tests
         * @codeCoverageIgnore
         */
        public static function clearCache() {
                self::$debugMode = null;
        }

        /**
         * Build a load.php URL
         *
         * @since 1.24
         * @param string $source Name of the ResourceLoader source
         * @param ResourceLoaderContext $context
         * @param array $extraQuery
         * @return string URL to load.php. May be protocol-relative if $wgLoadScript is, too.
         */
        public function createLoaderURL( $source, ResourceLoaderContext $context,
                $extraQuery = []
        ) {
                $query = self::createLoaderQuery( $context, $extraQuery );
                $script = $this->getLoadScript( $source );

                return wfAppendQuery( $script, $query );
        }

        /**
         * Helper for createLoaderURL()
         *
         * @since 1.24
         * @see makeLoaderQuery
         * @param ResourceLoaderContext $context
         * @param array $extraQuery
         * @return array
         */
        protected static function createLoaderQuery( ResourceLoaderContext $context, $extraQuery = [] ) {
                return self::makeLoaderQuery(
                        $context->getModules(),
                        $context->getLanguage(),
                        $context->getSkin(),
                        $context->getUser(),
                        $context->getVersion(),
                        $context->getDebug(),
                        $context->getOnly(),
                        $context->getRequest()->getBool( 'printable' ),
                        $context->getRequest()->getBool( 'handheld' ),
                        $extraQuery
                );
        }

        /**
         * Build a query array (array representation of query string) for load.php. Helper
         * function for createLoaderURL().
         *
         * @param array $modules
         * @param string $lang
         * @param string $skin
         * @param string|null $user
         * @param string|null $version
         * @param bool $debug
         * @param string|null $only
         * @param bool $printable
         * @param bool $handheld
         * @param array $extraQuery
         * @return array
         */
        public static function makeLoaderQuery( $modules, $lang, $skin, $user = null,
                $version = null, $debug = false, $only = null, $printable = false,
                $handheld = false, $extraQuery = []
        ) {
                $query = [
                        'modules' => self::makePackedModulesString( $modules ),
                ];
                // Keep urls short by omitting query parameters that
                // match the defaults assumed by ResourceLoaderContext.
                // Note: This relies on the defaults either being insignificant or forever constant,
                // as otherwise cached urls could change in meaning when the defaults change.
                if ( $lang !== ResourceLoaderContext::DEFAULT_LANG ) {
                        $query['lang'] = $lang;
                }
                if ( $skin !== ResourceLoaderContext::DEFAULT_SKIN ) {
                        $query['skin'] = $skin;
                }
                if ( $debug === true ) {
                        $query['debug'] = 'true';
                }
                if ( $user !== null ) {
                        $query['user'] = $user;
                }
                if ( $version !== null ) {
                        $query['version'] = $version;
                }
                if ( $only !== null ) {
                        $query['only'] = $only;
                }
                if ( $printable ) {
                        $query['printable'] = 1;
                }
                if ( $handheld ) {
                        $query['handheld'] = 1;
                }
                $query += $extraQuery;

                // Make queries uniform in order
                ksort( $query );
                return $query;
        }

        /**
         * Check a module name for validity.
         *
         * Module names may not contain pipes (|), commas (,) or exclamation marks (!) and can be
         * at most 255 bytes.
         *
         * @param string $moduleName Module name to check
         * @return bool Whether $moduleName is a valid module name
         */
        public static function isValidModuleName( $moduleName ) {
                return strcspn( $moduleName, '!,|', 0, 255 ) === strlen( $moduleName );
        }

        /**
         * Returns LESS compiler set up for use with MediaWiki
         *
         * @since 1.27
         * @param array $vars Associative array of variables that should be used
         *  for compilation. Since 1.32, this method no longer automatically includes
         *  global LESS vars from ResourceLoader::getLessVars (T191937).
         * @throws MWException
         * @return Less_Parser
         */
        public function getLessCompiler( $vars = [] ) {
                global $IP;
                // When called from the installer, it is possible that a required PHP extension
                // is missing (at least for now; see T49564). If this is the case, throw an
                // exception (caught by the installer) to prevent a fatal error later on.
                if ( !class_exists( 'Less_Parser' ) ) {
                        throw new MWException( 'MediaWiki requires the less.php parser' );
                }

                $parser = new Less_Parser;
                $parser->ModifyVars( $vars );
                $parser->SetImportDirs( [
                        "$IP/resources/src/mediawiki.less/" => '',
                ] );
                $parser->SetOption( 'relativeUrls', false );

                return $parser;
        }

        /**
         * Get global LESS variables.
         *
         * @since 1.27
         * @deprecated since 1.32 Use ResourceLoderModule::getLessVars() instead.
         * @return array Map of variable names to string CSS values.
         */
        public function getLessVars() {
                return [];
        }
}