MessageCache.php

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<?php
use MediaWiki\MediaWikiServices;
use Wikimedia\ScopedCallback;

define( 'MSG_CACHE_VERSION', 2 );

class MessageCache {
    const FOR_UPDATE = 1; // force message reload

    const WAIT_SEC = 15;
    const LOCK_TTL = 30;

    protected $mCache;

    protected $mDisable;

    protected $mExpiry;

    protected $mParserOptions, $mParser;

    protected $mLoadedLanguages = [];

    protected $mInParser = false;

    protected $mMemc;
    protected $wanCache;

    private static $instance;

    public static function singleton() {
        if ( self::$instance === null ) {
            global $wgUseDatabaseMessages, $wgMsgCacheExpiry;
            self::$instance = new self(
                wfGetMessageCacheStorage(),
                $wgUseDatabaseMessages,
                $wgMsgCacheExpiry
            );
        }

        return self::$instance;
    }

    public static function destroyInstance() {
        self::$instance = null;
    }

    public static function normalizeKey( $key ) {
        global $wgContLang;
        $lckey = strtr( $key, ' ', '_' );
        if ( ord( $lckey ) < 128 ) {
            $lckey[0] = strtolower( $lckey[0] );
        } else {
            $lckey = $wgContLang->lcfirst( $lckey );
        }

        return $lckey;
    }

    function __construct( $memCached, $useDB, $expiry ) {
        global $wgUseLocalMessageCache;

        if ( !$memCached ) {
            $memCached = wfGetCache( CACHE_NONE );
        }

        $this->mMemc = $memCached;
        $this->mDisable = !$useDB;
        $this->mExpiry = $expiry;

        if ( $wgUseLocalMessageCache ) {
            $this->localCache = MediaWikiServices::getInstance()->getLocalServerObjectCache();
        } else {
            $this->localCache = new EmptyBagOStuff();
        }

        $this->wanCache = ObjectCache::getMainWANInstance();
    }

    function getParserOptions() {
        global $wgUser;

        if ( !$this->mParserOptions ) {
            if ( !$wgUser->isSafeToLoad() ) {
                // $wgUser isn't unstubbable yet, so don't try to get a
                // ParserOptions for it. And don't cache this ParserOptions
                // either.
                $po = ParserOptions::newFromAnon();
                $po->setEditSection( false );
                return $po;
            }

            $this->mParserOptions = new ParserOptions;
            $this->mParserOptions->setEditSection( false );
        }

        return $this->mParserOptions;
    }

    protected function getLocalCache( $code ) {
        $cacheKey = wfMemcKey( __CLASS__, $code );

        return $this->localCache->get( $cacheKey );
    }

    protected function saveToLocalCache( $code, $cache ) {
        $cacheKey = wfMemcKey( __CLASS__, $code );
        $this->localCache->set( $cacheKey, $cache );
    }

    protected function load( $code, $mode = null ) {
        if ( !is_string( $code ) ) {
            throw new InvalidArgumentException( "Missing language code" );
        }

        # Don't do double loading...
        if ( isset( $this->mLoadedLanguages[$code] ) && $mode != self::FOR_UPDATE ) {
            return true;
        }

        # 8 lines of code just to say (once) that message cache is disabled
        if ( $this->mDisable ) {
            static $shownDisabled = false;
            if ( !$shownDisabled ) {
                wfDebug( __METHOD__ . ": disabled\n" );
                $shownDisabled = true;
            }

            return true;
        }

        # Loading code starts
        $success = false; # Keep track of success
        $staleCache = false; # a cache array with expired data, or false if none has been loaded
        $where = []; # Debug info, delayed to avoid spamming debug log too much

        # Hash of the contents is stored in memcache, to detect if data-center cache
        # or local cache goes out of date (e.g. due to replace() on some other server)
        list( $hash, $hashVolatile ) = $this->getValidationHash( $code );

        # Try the local cache and check against the cluster hash key...
        $cache = $this->getLocalCache( $code );
        if ( !$cache ) {
            $where[] = 'local cache is empty';
        } elseif ( !isset( $cache['HASH'] ) || $cache['HASH'] !== $hash ) {
            $where[] = 'local cache has the wrong hash';
            $staleCache = $cache;
        } elseif ( $this->isCacheExpired( $cache ) ) {
            $where[] = 'local cache is expired';
            $staleCache = $cache;
        } elseif ( $hashVolatile ) {
            $where[] = 'local cache validation key is expired/volatile';
            $staleCache = $cache;
        } else {
            $where[] = 'got from local cache';
            $success = true;
            $this->mCache[$code] = $cache;
        }

        if ( !$success ) {
            $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages
            # Try the global cache. If it is empty, try to acquire a lock. If
            # the lock can't be acquired, wait for the other thread to finish
            # and then try the global cache a second time.
            for ( $failedAttempts = 0; $failedAttempts <= 1; $failedAttempts++ ) {
                if ( $hashVolatile && $staleCache ) {
                    # Do not bother fetching the whole cache blob to avoid I/O.
                    # Instead, just try to get the non-blocking $statusKey lock
                    # below, and use the local stale value if it was not acquired.
                    $where[] = 'global cache is presumed expired';
                } else {
                    $cache = $this->mMemc->get( $cacheKey );
                    if ( !$cache ) {
                        $where[] = 'global cache is empty';
                    } elseif ( $this->isCacheExpired( $cache ) ) {
                        $where[] = 'global cache is expired';
                        $staleCache = $cache;
                    } elseif ( $hashVolatile ) {
                        # DB results are replica DB lag prone until the holdoff TTL passes.
                        # By then, updates should be reflected in loadFromDBWithLock().
                        # One thread renerates the cache while others use old values.
                        $where[] = 'global cache is expired/volatile';
                        $staleCache = $cache;
                    } else {
                        $where[] = 'got from global cache';
                        $this->mCache[$code] = $cache;
                        $this->saveToCaches( $cache, 'local-only', $code );
                        $success = true;
                    }
                }

                if ( $success ) {
                    # Done, no need to retry
                    break;
                }

                # We need to call loadFromDB. Limit the concurrency to one process.
                # This prevents the site from going down when the cache expires.
                # Note that the DB slam protection lock here is non-blocking.
                $loadStatus = $this->loadFromDBWithLock( $code, $where, $mode );
                if ( $loadStatus === true ) {
                    $success = true;
                    break;
                } elseif ( $staleCache ) {
                    # Use the stale cache while some other thread constructs the new one
                    $where[] = 'using stale cache';
                    $this->mCache[$code] = $staleCache;
                    $success = true;
                    break;
                } elseif ( $failedAttempts > 0 ) {
                    # Already blocked once, so avoid another lock/unlock cycle.
                    # This case will typically be hit if memcached is down, or if
                    # loadFromDB() takes longer than LOCK_WAIT.
                    $where[] = "could not acquire status key.";
                    break;
                } elseif ( $loadStatus === 'cantacquire' ) {
                    # Wait for the other thread to finish, then retry. Normally,
                    # the memcached get() will then yeild the other thread's result.
                    $where[] = 'waited for other thread to complete';
                    $this->getReentrantScopedLock( $cacheKey );
                } else {
                    # Disable cache; $loadStatus is 'disabled'
                    break;
                }
            }
        }

        if ( !$success ) {
            $where[] = 'loading FAILED - cache is disabled';
            $this->mDisable = true;
            $this->mCache = false;
            wfDebugLog( 'MessageCacheError', __METHOD__ . ": Failed to load $code\n" );
            # This used to throw an exception, but that led to nasty side effects like
            # the whole wiki being instantly down if the memcached server died
        } else {
            # All good, just record the success
            $this->mLoadedLanguages[$code] = true;
        }

        $info = implode( ', ', $where );
        wfDebugLog( 'MessageCache', __METHOD__ . ": Loading $code... $info\n" );

        return $success;
    }

    protected function loadFromDBWithLock( $code, array &$where, $mode = null ) {
        global $wgUseLocalMessageCache;

        # If cache updates on all levels fail, give up on message overrides.
        # This is to avoid easy site outages; see $saveSuccess comments below.
        $statusKey = wfMemcKey( 'messages', $code, 'status' );
        $status = $this->mMemc->get( $statusKey );
        if ( $status === 'error' ) {
            $where[] = "could not load; method is still globally disabled";
            return 'disabled';
        }

        # Now let's regenerate
        $where[] = 'loading from database';

        # Lock the cache to prevent conflicting writes.
        # This lock is non-blocking so stale cache can quickly be used.
        # Note that load() will call a blocking getReentrantScopedLock()
        # after this if it really need to wait for any current thread.
        $cacheKey = wfMemcKey( 'messages', $code );
        $scopedLock = $this->getReentrantScopedLock( $cacheKey, 0 );
        if ( !$scopedLock ) {
            $where[] = 'could not acquire main lock';
            return 'cantacquire';
        }

        $cache = $this->loadFromDB( $code, $mode );
        $this->mCache[$code] = $cache;
        $saveSuccess = $this->saveToCaches( $cache, 'all', $code );

        if ( !$saveSuccess ) {
            if ( !$wgUseLocalMessageCache ) {
                $this->mMemc->set( $statusKey, 'error', 60 * 5 );
                $where[] = 'could not save cache, disabled globally for 5 minutes';
            } else {
                $where[] = "could not save global cache";
            }
        }

        return true;
    }

    function loadFromDB( $code, $mode = null ) {
        global $wgMaxMsgCacheEntrySize, $wgLanguageCode, $wgAdaptiveMessageCache;

        $dbr = wfGetDB( ( $mode == self::FOR_UPDATE ) ? DB_MASTER : DB_REPLICA );

        $cache = [];

        # Common conditions
        $conds = [
            'page_is_redirect' => 0,
            'page_namespace' => NS_MEDIAWIKI,
        ];

        $mostused = [];
        if ( $wgAdaptiveMessageCache && $code !== $wgLanguageCode ) {
            if ( !isset( $this->mCache[$wgLanguageCode] ) ) {
                $this->load( $wgLanguageCode );
            }
            $mostused = array_keys( $this->mCache[$wgLanguageCode] );
            foreach ( $mostused as $key => $value ) {
                $mostused[$key] = "$value/$code";
            }
        }

        if ( count( $mostused ) ) {
            $conds['page_title'] = $mostused;
        } elseif ( $code !== $wgLanguageCode ) {
            $conds[] = 'page_title' . $dbr->buildLike( $dbr->anyString(), '/', $code );
        } else {
            # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
            # other than language code.
            $conds[] = 'page_title NOT' . $dbr->buildLike( $dbr->anyString(), '/', $dbr->anyString() );
        }

        # Conditions to fetch oversized pages to ignore them
        $bigConds = $conds;
        $bigConds[] = 'page_len > ' . intval( $wgMaxMsgCacheEntrySize );

        # Load titles for all oversized pages in the MediaWiki namespace
        $res = $dbr->select( 'page', 'page_title', $bigConds, __METHOD__ . "($code)-big" );
        foreach ( $res as $row ) {
            $cache[$row->page_title] = '!TOO BIG';
        }

        # Conditions to load the remaining pages with their contents
        $smallConds = $conds;
        $smallConds[] = 'page_latest=rev_id';
        $smallConds[] = 'rev_text_id=old_id';
        $smallConds[] = 'page_len <= ' . intval( $wgMaxMsgCacheEntrySize );

        $res = $dbr->select(
            [ 'page', 'revision', 'text' ],
            [ 'page_title', 'old_text', 'old_flags' ],
            $smallConds,
            __METHOD__ . "($code)-small"
        );

        foreach ( $res as $row ) {
            $text = Revision::getRevisionText( $row );
            if ( $text === false ) {
                // Failed to fetch data; possible ES errors?
                // Store a marker to fetch on-demand as a workaround...
                $entry = '!TOO BIG';
                wfDebugLog(
                    'MessageCache',
                    __METHOD__
                        . ": failed to load message page text for {$row->page_title} ($code)"
                );
            } else {
                $entry = ' ' . $text;
            }
            $cache[$row->page_title] = $entry;
        }

        $cache['VERSION'] = MSG_CACHE_VERSION;
        ksort( $cache );
        $cache['HASH'] = md5( serialize( $cache ) );
        $cache['EXPIRY'] = wfTimestamp( TS_MW, time() + $this->mExpiry );

        return $cache;
    }

    public function replace( $title, $text ) {
        global $wgMaxMsgCacheEntrySize, $wgContLang, $wgLanguageCode;

        if ( $this->mDisable ) {
            return;
        }

        list( $msg, $code ) = $this->figureMessage( $title );
        if ( strpos( $title, '/' ) !== false && $code === $wgLanguageCode ) {
            // Content language overrides do not use the /<code> suffix
            return;
        }

        // Note that if the cache is volatile, load() may trigger a DB fetch.
        // In that case we reenter/reuse the existing cache key lock to avoid
        // a self-deadlock. This is safe as no reads happen *directly* in this
        // method between getReentrantScopedLock() and load() below. There is
        // no risk of data "changing under our feet" for replace().
        $cacheKey = wfMemcKey( 'messages', $code );
        $scopedLock = $this->getReentrantScopedLock( $cacheKey );
        $this->load( $code, self::FOR_UPDATE );

        $titleKey = wfMemcKey( 'messages', 'individual', $title );
        if ( $text === false ) {
            // Article was deleted
            $this->mCache[$code][$title] = '!NONEXISTENT';
            $this->wanCache->delete( $titleKey );
        } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
            // Check for size
            $this->mCache[$code][$title] = '!TOO BIG';
            $this->wanCache->set( $titleKey, ' ' . $text, $this->mExpiry );
        } else {
            $this->mCache[$code][$title] = ' ' . $text;
            $this->wanCache->delete( $titleKey );
        }

        // Mark this cache as definitely "latest" (non-volatile) so
        // load() calls do try to refresh the cache with replica DB data
        $this->mCache[$code]['LATEST'] = time();

        // Update caches if the lock was acquired
        if ( $scopedLock ) {
            $this->saveToCaches( $this->mCache[$code], 'all', $code );
        }

        ScopedCallback::consume( $scopedLock );
        // Relay the purge to APC and other DCs
        $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );

        // Also delete cached sidebar... just in case it is affected
        $codes = [ $code ];
        if ( $code === 'en' ) {
            // Delete all sidebars, like for example on action=purge on the
            // sidebar messages
            $codes = array_keys( Language::fetchLanguageNames() );
        }

        foreach ( $codes as $code ) {
            $sidebarKey = wfMemcKey( 'sidebar', $code );
            $this->wanCache->delete( $sidebarKey );
        }

        // Update the message in the message blob store
        $resourceloader = RequestContext::getMain()->getOutput()->getResourceLoader();
        $blobStore = $resourceloader->getMessageBlobStore();
        $blobStore->updateMessage( $wgContLang->lcfirst( $msg ) );

        Hooks::run( 'MessageCacheReplace', [ $title, $text ] );
    }

    protected function isCacheExpired( $cache ) {
        if ( !isset( $cache['VERSION'] ) || !isset( $cache['EXPIRY'] ) ) {
            return true;
        }
        if ( $cache['VERSION'] != MSG_CACHE_VERSION ) {
            return true;
        }
        if ( wfTimestampNow() >= $cache['EXPIRY'] ) {
            return true;
        }

        return false;
    }

    protected function saveToCaches( array $cache, $dest, $code = false ) {
        if ( $dest === 'all' ) {
            $cacheKey = wfMemcKey( 'messages', $code );
            $success = $this->mMemc->set( $cacheKey, $cache );
            $this->setValidationHash( $code, $cache );
        } else {
            $success = true;
        }

        $this->saveToLocalCache( $code, $cache );

        return $success;
    }

    protected function getValidationHash( $code ) {
        $curTTL = null;
        $value = $this->wanCache->get(
            wfMemcKey( 'messages', $code, 'hash', 'v1' ),
            $curTTL,
            [ wfMemcKey( 'messages', $code ) ]
        );

        if ( !$value ) {
            // No hash found at all; cache must regenerate to be safe
            $hash = false;
            $expired = true;
        } else {
            $hash = $value['hash'];
            if ( ( time() - $value['latest'] ) < WANObjectCache::HOLDOFF_TTL ) {
                // Cache was recently updated via replace() and should be up-to-date
                $expired = false;
            } else {
                // See if the "check" key was bumped after the hash was generated
                $expired = ( $curTTL < 0 );
            }
        }

        return [ $hash, $expired ];
    }

    protected function setValidationHash( $code, array $cache ) {
        $this->wanCache->set(
            wfMemcKey( 'messages', $code, 'hash', 'v1' ),
            [
                'hash' => $cache['HASH'],
                'latest' => isset( $cache['LATEST'] ) ? $cache['LATEST'] : 0
            ],
            WANObjectCache::TTL_INDEFINITE
        );
    }

    protected function getReentrantScopedLock( $key, $timeout = self::WAIT_SEC ) {
        return $this->mMemc->getScopedLock( $key, $timeout, self::LOCK_TTL, __METHOD__ );
    }

    function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
        if ( is_int( $key ) ) {
            // Fix numerical strings that somehow become ints
            // on their way here
            $key = (string)$key;
        } elseif ( !is_string( $key ) ) {
            throw new MWException( 'Non-string key given' );
        } elseif ( $key === '' ) {
            // Shortcut: the empty key is always missing
            return false;
        }

        // For full keys, get the language code from the key
        $pos = strrpos( $key, '/' );
        if ( $isFullKey && $pos !== false ) {
            $langcode = substr( $key, $pos + 1 );
            $key = substr( $key, 0, $pos );
        }

        // Normalise title-case input (with some inlining)
        $lckey = MessageCache::normalizeKey( $key );

        Hooks::run( 'MessageCache::get', [ &$lckey ] );

        // Loop through each language in the fallback list until we find something useful
        $lang = wfGetLangObj( $langcode );
        $message = $this->getMessageFromFallbackChain(
            $lang,
            $lckey,
            !$this->mDisable && $useDB
        );

        // If we still have no message, maybe the key was in fact a full key so try that
        if ( $message === false ) {
            $parts = explode( '/', $lckey );
            // We may get calls for things that are http-urls from sidebar
            // Let's not load nonexistent languages for those
            // They usually have more than one slash.
            if ( count( $parts ) == 2 && $parts[1] !== '' ) {
                $message = Language::getMessageFor( $parts[0], $parts[1] );
                if ( $message === null ) {
                    $message = false;
                }
            }
        }

        // Post-processing if the message exists
        if ( $message !== false ) {
            // Fix whitespace
            $message = str_replace(
                [
                    # Fix for trailing whitespace, removed by textarea
                    '&#32;',
                    # Fix for NBSP, converted to space by firefox
                    '&nbsp;',
                    '&#160;',
                    '&shy;'
                ],
                [
                    ' ',
                    "\xc2\xa0",
                    "\xc2\xa0",
                    "\xc2\xad"
                ],
                $message
            );
        }

        return $message;
    }

    protected function getMessageFromFallbackChain( $lang, $lckey, $useDB ) {
        global $wgContLang;

        $alreadyTried = [];

         // First try the requested language.
        $message = $this->getMessageForLang( $lang, $lckey, $useDB, $alreadyTried );
        if ( $message !== false ) {
            return $message;
        }

        // Now try checking the site language.
        $message = $this->getMessageForLang( $wgContLang, $lckey, $useDB, $alreadyTried );
        return $message;
    }

    private function getMessageForLang( $lang, $lckey, $useDB, &$alreadyTried ) {
        global $wgContLang;
        $langcode = $lang->getCode();

        // Try checking the database for the requested language
        if ( $useDB ) {
            $uckey = $wgContLang->ucfirst( $lckey );

            if ( !isset( $alreadyTried[ $langcode ] ) ) {
                $message = $this->getMsgFromNamespace(
                    $this->getMessagePageName( $langcode, $uckey ),
                    $langcode
                );

                if ( $message !== false ) {
                    return $message;
                }
                $alreadyTried[ $langcode ] = true;
            }
        } else {
            $uckey = null;
        }

        // Check the CDB cache
        $message = $lang->getMessage( $lckey );
        if ( $message !== null ) {
            return $message;
        }

        // Try checking the database for all of the fallback languages
        if ( $useDB ) {
            $fallbackChain = Language::getFallbacksFor( $langcode );

            foreach ( $fallbackChain as $code ) {
                if ( isset( $alreadyTried[ $code ] ) ) {
                    continue;
                }

                $message = $this->getMsgFromNamespace(
                    $this->getMessagePageName( $code, $uckey ), $code );

                if ( $message !== false ) {
                    return $message;
                }
                $alreadyTried[ $code ] = true;
            }
        }

        return false;
    }

    private function getMessagePageName( $langcode, $uckey ) {
        global $wgLanguageCode;
        if ( $langcode === $wgLanguageCode ) {
            // Messages created in the content language will not have the /lang extension
            return $uckey;
        } else {
            return "$uckey/$langcode";
        }
    }

    public function getMsgFromNamespace( $title, $code ) {
        $this->load( $code );
        if ( isset( $this->mCache[$code][$title] ) ) {
            $entry = $this->mCache[$code][$title];
            if ( substr( $entry, 0, 1 ) === ' ' ) {
                // The message exists, so make sure a string
                // is returned.
                return (string)substr( $entry, 1 );
            } elseif ( $entry === '!NONEXISTENT' ) {
                return false;
            } elseif ( $entry === '!TOO BIG' ) {
                // Fall through and try invididual message cache below
            }
        } else {
            // XXX: This is not cached in process cache, should it?
            $message = false;
            Hooks::run( 'MessagesPreLoad', [ $title, &$message ] );
            if ( $message !== false ) {
                return $message;
            }

            return false;
        }

        // Try the individual message cache
        $titleKey = wfMemcKey( 'messages', 'individual', $title );

        $curTTL = null;
        $entry = $this->wanCache->get(
            $titleKey,
            $curTTL,
            [ wfMemcKey( 'messages', $code ) ]
        );
        $entry = ( $curTTL >= 0 ) ? $entry : false;

        if ( $entry ) {
            if ( substr( $entry, 0, 1 ) === ' ' ) {
                $this->mCache[$code][$title] = $entry;
                // The message exists, so make sure a string is returned
                return (string)substr( $entry, 1 );
            } elseif ( $entry === '!NONEXISTENT' ) {
                $this->mCache[$code][$title] = '!NONEXISTENT';

                return false;
            } else {
                // Corrupt/obsolete entry, delete it
                $this->wanCache->delete( $titleKey );
            }
        }

        // Try loading it from the database
        $dbr = wfGetDB( DB_REPLICA );
        $cacheOpts = Database::getCacheSetOptions( $dbr );
        // Use newKnownCurrent() to avoid querying revision/user tables
        $titleObj = Title::makeTitle( NS_MEDIAWIKI, $title );
        if ( $titleObj->getLatestRevID() ) {
            $revision = Revision::newKnownCurrent(
                $dbr,
                $titleObj->getArticleID(),
                $titleObj->getLatestRevID()
            );
        } else {
            $revision = false;
        }

        if ( $revision ) {
            $content = $revision->getContent();
            if ( !$content ) {
                // A possibly temporary loading failure.
                wfDebugLog(
                    'MessageCache',
                    __METHOD__ . ": failed to load message page text for {$title} ($code)"
                );
                $message = null; // no negative caching
            } else {
                // XXX: Is this the right way to turn a Content object into a message?
                // NOTE: $content is typically either WikitextContent, JavaScriptContent or
                //       CssContent. MessageContent is *not* used for storing messages, it's
                //       only used for wrapping them when needed.
                $message = $content->getWikitextForTransclusion();

                if ( $message === false || $message === null ) {
                    wfDebugLog(
                        'MessageCache',
                        __METHOD__ . ": message content doesn't provide wikitext "
                            . "(content model: " . $content->getModel() . ")"
                    );

                    $message = false; // negative caching
                } else {
                    $this->mCache[$code][$title] = ' ' . $message;
                    $this->wanCache->set( $titleKey, ' ' . $message, $this->mExpiry, $cacheOpts );
                }
            }
        } else {
            $message = false; // negative caching
        }

        if ( $message === false ) { // negative caching
            $this->mCache[$code][$title] = '!NONEXISTENT';
            $this->wanCache->set( $titleKey, '!NONEXISTENT', $this->mExpiry, $cacheOpts );
        }

        return $message;
    }

    function transform( $message, $interface = false, $language = null, $title = null ) {
        // Avoid creating parser if nothing to transform
        if ( strpos( $message, '{{' ) === false ) {
            return $message;
        }

        if ( $this->mInParser ) {
            return $message;
        }

        $parser = $this->getParser();
        if ( $parser ) {
            $popts = $this->getParserOptions();
            $popts->setInterfaceMessage( $interface );
            $popts->setTargetLanguage( $language );

            $userlang = $popts->setUserLang( $language );
            $this->mInParser = true;
            $message = $parser->transformMsg( $message, $popts, $title );
            $this->mInParser = false;
            $popts->setUserLang( $userlang );
        }

        return $message;
    }

    function getParser() {
        global $wgParser, $wgParserConf;
        if ( !$this->mParser && isset( $wgParser ) ) {
            # Do some initialisation so that we don't have to do it twice
            $wgParser->firstCallInit();
            # Clone it and store it
            $class = $wgParserConf['class'];
            if ( $class == 'ParserDiffTest' ) {
                # Uncloneable
                $this->mParser = new $class( $wgParserConf );
            } else {
                $this->mParser = clone $wgParser;
            }
        }

        return $this->mParser;
    }

    public function parse( $text, $title = null, $linestart = true,
        $interface = false, $language = null
    ) {
        if ( $this->mInParser ) {
            return htmlspecialchars( $text );
        }

        $parser = $this->getParser();
        $popts = $this->getParserOptions();
        $popts->setInterfaceMessage( $interface );

        if ( is_string( $language ) ) {
            $language = Language::factory( $language );
        }
        $popts->setTargetLanguage( $language );

        if ( !$title || !$title instanceof Title ) {
            global $wgTitle;
            wfDebugLog( 'GlobalTitleFail', __METHOD__ . ' called by ' .
                wfGetAllCallers( 6 ) . ' with no title set.' );
            $title = $wgTitle;
        }
        // Sometimes $wgTitle isn't set either...
        if ( !$title ) {
            # It's not uncommon having a null $wgTitle in scripts. See r80898
            # Create a ghost title in such case
            $title = Title::makeTitle( NS_SPECIAL, 'Badtitle/title not set in ' . __METHOD__ );
        }

        $this->mInParser = true;
        $res = $parser->parse( $text, $title, $popts, $linestart );
        $this->mInParser = false;

        return $res;
    }

    function disable() {
        $this->mDisable = true;
    }

    function enable() {
        $this->mDisable = false;
    }

    public function isDisabled() {
        return $this->mDisable;
    }

    function clear() {
        $langs = Language::fetchLanguageNames( null, 'mw' );
        foreach ( array_keys( $langs ) as $code ) {
            # Global and local caches
            $this->wanCache->touchCheckKey( wfMemcKey( 'messages', $code ) );
        }

        $this->mLoadedLanguages = [];
    }

    public function figureMessage( $key ) {
        global $wgLanguageCode;

        $pieces = explode( '/', $key );
        if ( count( $pieces ) < 2 ) {
            return [ $key, $wgLanguageCode ];
        }

        $lang = array_pop( $pieces );
        if ( !Language::fetchLanguageName( $lang, null, 'mw' ) ) {
            return [ $key, $wgLanguageCode ];
        }

        $message = implode( '/', $pieces );

        return [ $message, $lang ];
    }

    public function getAllMessageKeys( $code ) {
        global $wgContLang;
        $this->load( $code );
        if ( !isset( $this->mCache[$code] ) ) {
            // Apparently load() failed
            return null;
        }
        // Remove administrative keys
        $cache = $this->mCache[$code];
        unset( $cache['VERSION'] );
        unset( $cache['EXPIRY'] );
        // Remove any !NONEXISTENT keys
        $cache = array_diff( $cache, [ '!NONEXISTENT' ] );

        // Keys may appear with a capital first letter. lcfirst them.
        return array_map( [ $wgContLang, 'lcfirst' ], array_keys( $cache ) );
    }
}