* (bug 15497) Removed encoding attribute from <?xml ?> tags

[mediawiki.git] / includes / MessageCache.php

<?php
/**
 * @file
 * @ingroup Cache
 */

/**
 *
 */
define( 'MSG_LOAD_TIMEOUT', 60);
define( 'MSG_LOCK_TIMEOUT', 10);
define( 'MSG_WAIT_TIMEOUT', 10);
define( 'MSG_CACHE_VERSION', 1 );

/**
 * Message cache
 * Performs various MediaWiki namespace-related functions
 * @ingroup Cache
 */
class MessageCache {
        // Holds loaded messages that are defined in MediaWiki namespace.
        var $mCache;

        var $mUseCache, $mDisable, $mExpiry;
        var $mKeys, $mParserOptions, $mParser;
        var $mExtensionMessages = array();
        var $mInitialised = false;
        var $mAllMessagesLoaded; // Extension messages

        // Variable for tracking which variables are loaded
        var $mLoadedLanguages = array();

        function __construct( &$memCached, $useDB, $expiry, /*ignored*/ $memcPrefix ) {
                $this->mUseCache = !is_null( $memCached );
                $this->mMemc = &$memCached;
                $this->mDisable = !$useDB;
                $this->mExpiry = $expiry;
                $this->mDisableTransform = false;
                $this->mKeys = false; # initialised on demand
                $this->mInitialised = true;
                $this->mParser = null;
        }


        /**
         * ParserOptions is lazy initialised.
         */
        function getParserOptions() {
                if ( !$this->mParserOptions ) {
                        $this->mParserOptions = new ParserOptions;
                }
                return $this->mParserOptions;
        }

        /**
         * Try to load the cache from a local file.
         * Actual format of the file depends on the $wgLocalMessageCacheSerialized
         * setting.
         *
         * @param $hash String: the hash of contents, to check validity.
         * @param $code Mixed: Optional language code, see documenation of load().
         * @return false on failure.
         */
        function loadFromLocal( $hash, $code ) {
                global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;

                $filename = "$wgLocalMessageCache/messages-" . wfWikiID() . "-$code";

                # Check file existence
                wfSuppressWarnings();
                $file = fopen( $filename, 'r' );
                wfRestoreWarnings();
                if ( !$file ) {
                        return false; // No cache file
                }

                if ( $wgLocalMessageCacheSerialized ) {
                        // Check to see if the file has the hash specified
                        $localHash = fread( $file, 32 );
                        if ( $hash === $localHash ) {
                                // All good, get the rest of it
                                $serialized = '';
                                while ( !feof( $file ) ) {
                                        $serialized .= fread( $file, 100000 );
                                }
                                fclose( $file );
                                return $this->setCache( unserialize( $serialized ), $code );
                        } else {
                                fclose( $file );
                                return false; // Wrong hash
                        }
                } else {
                        $localHash=substr(fread($file,40),8);
                        fclose($file);
                        if ($hash!=$localHash) {
                                return false; // Wrong hash
                        }

                        # Require overwrites the member variable or just shadows it?
                        require( $filename );
                        return $this->setCache( $this->mCache, $code );
                }
        }

        /**
         * Save the cache to a local file.
         */
        function saveToLocal( $serialized, $hash, $code ) {
                global $wgLocalMessageCache;

                $filename = "$wgLocalMessageCache/messages-" . wfWikiID() . "-$code";
                wfMkdirParents( $wgLocalMessageCache ); // might fail

                wfSuppressWarnings();
                $file = fopen( $filename, 'w' );
                wfRestoreWarnings();

                if ( !$file ) {
                        wfDebug( "Unable to open local cache file for writing\n" );
                        return;
                }

                fwrite( $file, $hash . $serialized );
                fclose( $file );
                @chmod( $filename, 0666 );
        }

        function saveToScript( $array, $hash, $code ) {
                global $wgLocalMessageCache;

                $filename = "$wgLocalMessageCache/messages-" . wfWikiID() . "-$code";
                $tempFilename = $filename . '.tmp';
                wfMkdirParents( $wgLocalMessageCache ); // might fail

                wfSuppressWarnings();
                $file = fopen( $tempFilename, 'w');
                wfRestoreWarnings();

                if ( !$file ) {
                        wfDebug( "Unable to open local cache file for writing\n" );
                        return;
                }

                fwrite($file,"<?php\n//$hash\n\n \$this->mCache = array(");

                foreach ($array as $key => $message) {
                        $key = $this->escapeForScript($key);
                        $messages = $this->escapeForScript($message);
                        fwrite($file, "'$key' => '$message',\n");
                }

                fwrite($file,");\n?>");
                fclose($file);
                rename($tempFilename, $filename);
        }

        function escapeForScript($string) {
                $string = str_replace( '\\', '\\\\', $string );
                $string = str_replace( '\'', '\\\'', $string );
                return $string;
        }

        /**
         * Set the cache to $cache, if it is valid. Otherwise set the cache to false.
         */
        function setCache( $cache, $code ) {
                if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
                        $this->mCache[$code] = $cache;
                        return true;
                } else {
                        return false;
                }
        }

        /**
         * Loads messages from caches or from database in this order:
         * (1) local message cache (if $wgLocalMessageCache is enabled)
         * (2) memcached
         * (3) from the database.
         *
         * When succesfully loading from (2) or (3), all higher level caches are
         * updated for the newest version.
         *
         * Nothing is loaded if  member variable mDisabled is true, either manually
         * set by calling code or if message loading fails (is this possible?).
         *
         * Returns true if cache is already populated or it was succesfully populated,
         * or false if populating empty cache fails. Also returns true if MessageCache
         * is disabled.
         *
         * @param $code String: language to which load messages
         */
        function load( $code = false ) {
                global $wgLocalMessageCache;

                if ( !$this->mUseCache ) {
                        return true;
                }

                if( !is_string( $code ) ) {
                        # This isn't really nice, so at least make a note about it and try to
                        # fall back
                        wfDebug( __METHOD__ . " called without providing a language code\n" );
                        $code = 'en';
                }

                # Don't do double loading...
                if ( isset($this->mLoadedLanguages[$code]) ) 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
                wfProfileIn( __METHOD__ );
                $success = false; # Keep track of success
                $where = array(); # Debug info, delayed to avoid spamming debug log too much
                $cacheKey = wfMemcKey( 'messages', $code ); # Key in memc for messages


                # (1) local cache
                # Hash of the contents is stored in memcache, to detect if local cache goes
                # out of date (due to update in other thread?)
                if ( $wgLocalMessageCache !== false ) {
                        wfProfileIn( __METHOD__ . '-fromlocal' );

                        $hash = $this->mMemc->get( wfMemcKey( 'messages', $code, 'hash' ) );
                        if ( $hash ) {
                                $success = $this->loadFromLocal( $hash, $code );
                                if ( $success ) $where[] = 'got from local cache';
                        }
                        wfProfileOut( __METHOD__ . '-fromlocal' );
                }

                # (2) memcache
                # Fails if nothing in cache, or in the wrong version.
                if ( !$success ) {
                        wfProfileIn( __METHOD__ . '-fromcache' );
                        $cache = $this->mMemc->get( $cacheKey );
                        $success = $this->setCache( $cache, $code );
                        if ( $success ) {
                                $where[] = 'got from global cache';
                                $this->saveToCaches( $cache, false, $code );
                        }
                        wfProfileOut( __METHOD__ . '-fromcache' );
                }


                # (3)
                # Nothing in caches... so we need create one and store it in caches
                if ( !$success ) {
                        $where[] = 'cache is empty';
                        $where[] = 'loading from database';

                        $this->lock($cacheKey);

                        $cache = $this->loadFromDB( $code );
                        $success = $this->setCache( $cache, $code );
                        if ( $success ) {
                                $this->saveToCaches( $cache, true, $code );
                        }

                        $this->unlock($cacheKey);
                }

                if ( !$success ) {
                        # Bad luck... this should not happen
                        $where[] = 'loading FAILED - cache is disabled';
                        $info = implode( ', ', $where );
                        wfDebug( __METHOD__ . ": Loading $code... $info\n" );
                        $this->mDisable = true;
                        $this->mCache = false;
                } else {
                        # All good, just record the success
                        $info = implode( ', ', $where );
                        wfDebug( __METHOD__ . ": Loading $code... $info\n" );
                        $this->mLoadedLanguages[$code] = true;
                }
                wfProfileOut( __METHOD__ );
                return $success;
        }

        /**
         * Loads cacheable messages from the database. Messages bigger than
         * $wgMaxMsgCacheEntrySize are assigned a special value, and are loaded
         * on-demand from the database later.
         *
         * @param $code Optional language code, see documenation of load().
         * @return Array: Loaded messages for storing in caches.
         */
        function loadFromDB( $code = false ) {
                wfProfileIn( __METHOD__ );
                global $wgMaxMsgCacheEntrySize, $wgContLanguageCode;
                $dbr = wfGetDB( DB_SLAVE );
                $cache = array();

                # Common conditions
                $conds = array(
                        'page_is_redirect' => 0,
                        'page_namespace' => NS_MEDIAWIKI,
                );

                if ( $code ) {
                        # Is this fast enough. Should not matter if the filtering is done in the
                        # database or in code.
                        if ( $code !== $wgContLanguageCode ) {
                                # Messages for particular language
                                $escapedCode = $dbr->escapeLike( $code );
                                $conds[] = "page_title like '%%/$escapedCode'";
                        } else {
                                # Effectively disallows use of '/' character in NS_MEDIAWIKI for uses
                                # other than language code.
                                $conds[] = "page_title not like '%%/%%'";
                        }
                }

                # 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__ );
                while ( $row = $dbr->fetchObject( $res ) ) {
                        $cache[$row->page_title] = '!TOO BIG';
                }
                $dbr->freeResult( $res );

                # 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( array( 'page', 'revision', 'text' ),
                        array( 'page_title', 'old_text', 'old_flags' ),
                        $smallConds, __METHOD__ );

                for ( $row = $dbr->fetchObject( $res ); $row; $row = $dbr->fetchObject( $res ) ) {
                        $cache[$row->page_title] = ' ' . Revision::getRevisionText( $row );
                }
                $dbr->freeResult( $res );

                $cache['VERSION'] = MSG_CACHE_VERSION;
                wfProfileOut( __METHOD__ );
                return $cache;
        }

        /**
         * Updates cache as necessary when message page is changed
         *
         * @param $title String: name of the page changed.
         * @param $text Mixed: new contents of the page.
         */
        public function replace( $title, $text ) {
                global $wgMaxMsgCacheEntrySize;
                wfProfileIn( __METHOD__ );


                list( , $code ) = $this->figureMessage( $title );

                $cacheKey = wfMemcKey( 'messages', $code );
                $this->load($code);
                $this->lock($cacheKey);

                if ( is_array($this->mCache[$code]) ) {
                        $titleKey = wfMemcKey( 'messages', 'individual', $title );

                        if ( $text === false ) {
                                # Article was deleted
                                unset( $this->mCache[$code][$title] );
                                $this->mMemc->delete( $titleKey );

                        } elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
                                # Check for size
                                $this->mCache[$code][$title] = '!TOO BIG';
                                $this->mMemc->set( $titleKey, ' ' . $text, $this->mExpiry );

                        } else {
                                $this->mCache[$code][$title] = ' ' . $text;
                                $this->mMemc->delete( $titleKey );
                        }

                        # Update caches
                        $this->saveToCaches( $this->mCache[$code], true, $code );
                }
                $this->unlock($cacheKey);

                // Also delete cached sidebar... just in case it is affected
                global $parserMemc;
                $sidebarKey = wfMemcKey( 'sidebar', $code );
                $parserMemc->delete( $sidebarKey );

                wfProfileOut( __METHOD__ );
        }

        /**
         * Shortcut to update caches.
         *
         * @param $cache Array: cached messages with a version.
         * @param $cacheKey String: Identifier for the cache.
         * @param $memc Bool: Wether to update or not memcache.
         * @param $code String: Language code.
         * @return False on somekind of error.
         */
        protected function saveToCaches( $cache, $memc = true, $code = false ) {
                wfProfileIn( __METHOD__ );
                global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;

                $cacheKey = wfMemcKey( 'messages', $code );
                $statusKey = wfMemcKey( 'messages', $code, 'status' );

                $success = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
                if ( !$success ) return true; # Other process should be updating them now

                $i = 0;
                if ( $memc ) {
                        # Save in memcached
                        # Keep trying if it fails, this is kind of important

                        for ($i=0; $i<20 &&
                                !$this->mMemc->set( $cacheKey, $cache, $this->mExpiry );
                                $i++ ) {
                                usleep(mt_rand(500000,1500000));
                        }
                }

                # Save to local cache
                if ( $wgLocalMessageCache !== false ) {
                        $serialized = serialize( $cache );
                        $hash = md5( $serialized );
                        $this->mMemc->set( wfMemcKey( 'messages', $code, 'hash' ), $hash, $this->mExpiry );
                        if ($wgLocalMessageCacheSerialized) {
                                $this->saveToLocal( $serialized, $hash, $code );
                        } else {
                                $this->saveToScript( $cache, $hash, $code );
                        }
                }

                if ( $i == 20 ) {
                        $this->mMemc->set( $statusKey, 'error', 60*5 );
                        wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
                        $success = false;
                } else {
                        $this->mMemc->delete( $statusKey );
                        $success = true;
                }
                wfProfileOut( __METHOD__ );
                return $success;
        }

        /**
         * Returns success
         * Represents a write lock on the messages key
         */
        function lock($key) {
                if ( !$this->mUseCache ) {
                        return true;
                }

                $lockKey = $key . ':lock';
                for ($i=0; $i < MSG_WAIT_TIMEOUT && !$this->mMemc->add( $lockKey, 1, MSG_LOCK_TIMEOUT ); $i++ ) {
                        sleep(1);
                }

                return $i >= MSG_WAIT_TIMEOUT;
        }

        function unlock($key) {
                if ( !$this->mUseCache ) {
                        return;
                }

                $lockKey = $key . ':lock';
                $this->mMemc->delete( $lockKey );
        }

        /**
         * Get a message from either the content language or the user language.
         *
         * @param string $key The message cache key
         * @param bool $useDB Get the message from the DB, false to use only the localisation
         * @param string $langcode Code of the language to get the message for, if
         *                         it is a valid code create a language for that
         *                         language, if it is a string but not a valid code
         *                         then make a basic language object, if it is a
         *                         false boolean then use the current users
         *                         language (as a fallback for the old parameter
         *                         functionality), or if it is a true boolean then
         *                         use the wikis content language (also as a
         *                         fallback).
         * @param bool $isFullKey Specifies whether $key is a two part key "lang/msg".
         */
        function get( $key, $useDB = true, $langcode = true, $isFullKey = false ) {
                global $wgContLanguageCode, $wgContLang;

                $lang = wfGetLangObj( $langcode );
                $langcode = $lang->getCode();

                # If uninitialised, someone is trying to call this halfway through Setup.php
                if( !$this->mInitialised ) {
                        return '&lt;' . htmlspecialchars($key) . '&gt;';
                }

                $message = false;

                # Normalise title-case input
                $lckey = $wgContLang->lcfirst( $key );
                $lckey = str_replace( ' ', '_', $lckey );

                # Try the MediaWiki namespace
                if( !$this->mDisable && $useDB ) {
                        $title = $wgContLang->ucfirst( $lckey );
                        if(!$isFullKey && ($langcode != $wgContLanguageCode) ) {
                                $title .= '/' . $langcode;
                        }
                        $message = $this->getMsgFromNamespace( $title, $langcode );
                }

                # Try the extension array
                if ( $message === false && isset( $this->mExtensionMessages[$langcode][$lckey] ) ) {
                        $message = $this->mExtensionMessages[$langcode][$lckey];
                }
                if ( $message === false && isset( $this->mExtensionMessages['en'][$lckey] ) ) {
                        $message = $this->mExtensionMessages['en'][$lckey];
                }

                # Try the array in the language object
                if ( $message === false ) {
                        $message = $lang->getMessage( $lckey );
                        if ( is_null( $message ) ) {
                                $message = false;
                        }
                }

                # Try the array of another language
                $pos = strrpos( $lckey, '/' );
                if( $message === false && $pos !== false) {
                        $mkey = substr( $lckey, 0, $pos );
                        $code = substr( $lckey, $pos+1 );
                        if ( $code ) {
                                # We may get calls for things that are http-urls from sidebar
                                # Let's not load nonexistent languages for those
                                $validCodes = array_keys( Language::getLanguageNames() );
                                if ( in_array( $code, $validCodes ) ) {
                                        $message = Language::getMessageFor( $mkey, $code );
                                        if ( is_null( $message ) ) {
                                                $message = false;
                                        }
                                }
                        }
                }

                # Is this a custom message? Try the default language in the db...
                if( ($message === false || $message === '-' ) &&
                        !$this->mDisable && $useDB &&
                        !$isFullKey && ($langcode != $wgContLanguageCode) ) {
                        $message = $this->getMsgFromNamespace( $wgContLang->ucfirst( $lckey ), $wgContLanguageCode );
                }

                # Final fallback
                if( $message === false ) {
                        return '&lt;' . htmlspecialchars($key) . '&gt;';
                }
                return $message;
        }

        /**
         * Get a message from the MediaWiki namespace, with caching. The key must
         * first be converted to two-part lang/msg form if necessary.
         *
         * @param $title String: Message cache key with initial uppercase letter.
         * @param $code String: code denoting the language to try.
         */
        function getMsgFromNamespace( $title, $code ) {
                $type = false;
                $message = false;

                if ( $this->mUseCache ) {
                        $this->load( $code );
                        if (isset( $this->mCache[$code][$title] ) ) {
                                $entry = $this->mCache[$code][$title];
                                $type = substr( $entry, 0, 1 );
                                if ( $type == ' ' ) {
                                        return substr( $entry, 1 );
                                }
                        }
                }

                # Call message hooks, in case they are defined
                wfRunHooks('MessagesPreLoad', array( $title, &$message ) );
                if ( $message !== false ) {
                        return $message;
                }

                # If there is no cache entry and no placeholder, it doesn't exist
                if ( $type !== '!' ) {
                        return false;
                }

                $titleKey = wfMemcKey( 'messages', 'individual', $title );

                # Try the individual message cache
                if ( $this->mUseCache ) {
                        $entry = $this->mMemc->get( $titleKey );
                        if ( $entry ) {
                                $type = substr( $entry, 0, 1 );

                                if ( $type === ' ' ) {
                                        # Ok!
                                        $message = substr( $entry, 1 );
                                        $this->mCache[$code][$title] = $entry;
                                        return $message;
                                } elseif ( $entry === '!NONEXISTENT' ) {
                                        return false;
                                } else {
                                        # Corrupt/obsolete entry, delete it
                                        $this->mMemc->delete( $titleKey );
                                }

                        }
                }

                # Try loading it from the DB
                $revision = Revision::newFromTitle( Title::makeTitle( NS_MEDIAWIKI, $title ) );
                if( $revision ) {
                        $message = $revision->getText();
                        if ($this->mUseCache) {
                                $this->mCache[$code][$title] = ' ' . $message;
                                $this->mMemc->set( $titleKey, $message, $this->mExpiry );
                        }
                } else {
                        # Negative caching
                        # Use some special text instead of false, because false gets converted to '' somewhere
                        $this->mMemc->set( $titleKey, '!NONEXISTENT', $this->mExpiry );
                        $this->mCache[$code][$title] = false;
                }
                return $message;
        }

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

                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 == 'Parser_DiffTest' ) {
                                # Uncloneable
                                $this->mParser = new $class( $wgParserConf );
                        } else {
                                $this->mParser = clone $wgParser;
                        }
                        #wfDebug( __METHOD__ . ": following contents triggered transform: $message\n" );
                }
                if ( $this->mParser ) {
                        $popts = $this->getParserOptions();
                        $popts->setInterfaceMessage( $interface );
                        $message = $this->mParser->transformMsg( $message, $popts );
                }
                return $message;
        }

        function disable() { $this->mDisable = true; }
        function enable() { $this->mDisable = false; }
 
        /** @deprecated */
        function disableTransform(){
                wfDeprecated( __METHOD__ );
        }
        function enableTransform() {
                wfDeprecated( __METHOD__ );
        }
        function setTransform( $x ) {
                wfDeprecated( __METHOD__ );
        }
        function getTransform() {
                wfDeprecated( __METHOD__ );
                return false;
        }

        /**
         * Add a message to the cache
         *
         * @param mixed $key
         * @param mixed $value
         * @param string $lang The messages language, English by default
         */
        function addMessage( $key, $value, $lang = 'en' ) {
                $this->mExtensionMessages[$lang][$key] = $value;
        }

        /**
         * Add an associative array of message to the cache
         *
         * @param array $messages An associative array of key => values to be added
         * @param string $lang The messages language, English by default
         */
        function addMessages( $messages, $lang = 'en' ) {
                wfProfileIn( __METHOD__ );
                if ( !is_array( $messages ) ) {
                        throw new MWException( __METHOD__.': Invalid message array' );
                }
                if ( isset( $this->mExtensionMessages[$lang] ) ) {
                        $this->mExtensionMessages[$lang] = $messages + $this->mExtensionMessages[$lang];
                } else {
                        $this->mExtensionMessages[$lang] = $messages;
                }
                wfProfileOut( __METHOD__ );
        }

        /**
         * Add a 2-D array of messages by lang. Useful for extensions.
         *
         * @param array $messages The array to be added
         */
        function addMessagesByLang( $messages ) {
                wfProfileIn( __METHOD__ );
                foreach ( $messages as $key => $value ) {
                        $this->addMessages( $value, $key );
                }
                wfProfileOut( __METHOD__ );
        }

        /**
         * Get the extension messages for a specific language. Only English, interface
         * and content language are guaranteed to be loaded.
         *
         * @param string $lang The messages language, English by default
         */
        function getExtensionMessagesFor( $lang = 'en' ) {
                wfProfileIn( __METHOD__ );
                $messages = array();
                if ( isset( $this->mExtensionMessages[$lang] ) ) {
                        $messages = $this->mExtensionMessages[$lang];
                }
                if ( $lang != 'en' ) {
                        $messages = $messages + $this->mExtensionMessages['en'];
                }
                wfProfileOut( __METHOD__ );
                return $messages;
        }

        /**
         * Clear all stored messages. Mainly used after a mass rebuild.
         */
        function clear() {
                if( $this->mUseCache ) {
                        $langs = Language::getLanguageNames( false );
                        foreach ( array_keys($langs) as $code ) {
                                # Global cache
                                $this->mMemc->delete( wfMemcKey( 'messages', $code ) );
                                # Invalidate all local caches
                                $this->mMemc->delete( wfMemcKey( 'messages', $code, 'hash' ) );
                        }
                }
        }

        function loadAllMessages() {
                global $wgExtensionMessagesFiles;
                if ( $this->mAllMessagesLoaded ) {
                        return;
                }
                $this->mAllMessagesLoaded = true;

                # Some extensions will load their messages when you load their class file
                wfLoadAllExtensions();
                # Others will respond to this hook
                wfRunHooks( 'LoadAllMessages' );
                # Some register their messages in $wgExtensionMessagesFiles
                foreach ( $wgExtensionMessagesFiles as $name => $file ) {
                        wfLoadExtensionMessages( $name );
                }
                # Still others will respond to neither, they are EVIL. We sometimes need to know!
        }

        /**
         * Load messages from a given file
         * 
         * @param string $filename Filename of file to load.
         * @param string $langcode Language to load messages for, or false for 
     *                         default behvaiour (en, content language and user
     *                         language).
         */
        function loadMessagesFile( $filename, $langcode = false ) {
                global $wgLang, $wgContLang;
                $messages = $magicWords = false;
                require( $filename );

                $validCodes = Language::getLanguageNames();
                if( is_string( $langcode ) && array_key_exists( $langcode, $validCodes ) ) {
                        # Load messages for given language code.
                        $this->processMessagesArray( $messages, $langcode );
                } elseif( is_string( $langcode ) && !array_key_exists( $langcode, $validCodes ) ) {
                        wfDebug( "Invalid language '$langcode' code passed to MessageCache::loadMessagesFile()" );
                } else {
                        # Load only languages that are usually used, and merge all
                        # fallbacks, except English.
                        $langs = array_unique( array( 'en', $wgContLang->getCode(), $wgLang->getCode() ) );
                        foreach( $langs as $code ) {
                                $this->processMessagesArray( $messages, $code );
                        }
                }

                if ( $magicWords !== false ) {
                        global $wgContLang;
                        $wgContLang->addMagicWordsByLang( $magicWords );
                }
        }

        /**
         * Process an array of messages, loading it into the message cache.
         *
         * @param array $messages Messages array.
         * @param string $langcode Language code to process.
         */
        function processMessagesArray( $messages, $langcode ) {
                $fallbackCode = $langcode;
                $mergedMessages = array();
                do {
                        if ( isset($messages[$fallbackCode]) ) {
                                $mergedMessages += $messages[$fallbackCode];
                        }
                        $fallbackCode = Language::getFallbackfor( $fallbackCode );
                } while( $fallbackCode && $fallbackCode !== 'en' );
                
                if ( !empty($mergedMessages) )
                        $this->addMessages( $mergedMessages, $langcode );
        }

        public function figureMessage( $key ) {
                global $wgContLanguageCode;
                $pieces = explode('/', $key, 2);

                $key = $pieces[0];

                # Language the user is translating to
                $langCode = isset($pieces[1]) ? $pieces[1] : $wgContLanguageCode;
                return array( $key, $langCode );
        }

}