/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 = array(); // 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);

			# Limit the concurrency of loadFromDB to a single process 
			# This prevents the site from going down when the cache expires
			$statusKey = wfMemcKey( 'messages', $code, 'status' );
			$success = $this->mMemc->add( $statusKey, 'loading', MSG_LOAD_TIMEOUT );
			if ( $success ) {
				$cache = $this->loadFromDB( $code );
				$success = $this->setCache( $cache, $code );
			}
			if ( $success ) {
				$success = $this->saveToCaches( $cache, true, $code );
				if ( $success ) {
					$this->mMemc->delete( $statusKey );
				} else {
					$this->mMemc->set( $statusKey, 'error', 60*5 );
					wfDebug( "MemCached set error in MessageCache: restart memcached server!\n" );
				}
			}
			$this->unlock($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 );

		$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 ) {
			$success = false;
		} else {
			$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, $language = null ) {
		// 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 );
			$popts->setTargetLanguage( $language );
			$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' ) {
		global $wgContLang;
		# Normalise title-case input
		$lckey = str_replace( ' ', '_', $wgContLang->lcfirst( $key ) );
		$this->mExtensionMessages[$lang][$lckey] = $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( $lang = false ) {
		global $wgExtensionMessagesFiles;
		$key = $lang === false ? '*' : $lang;
		if ( isset( $this->mAllMessagesLoaded[$key] ) ) {
			return;
		}
		$this->mAllMessagesLoaded[$key] = 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, $lang );
		}
		# 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;
		wfProfileIn( __METHOD__ );
		$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 );
		}
		wfProfileOut( __METHOD__ );
	}

	/**
	 * 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 ) {
		wfProfileIn( __METHOD__ );
		$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 );
		wfProfileOut( __METHOD__ );
	}

	public function figureMessage( $key ) {
		global $wgContLanguageCode;
		$pieces = explode( '/', $key );
		if( count( $pieces ) < 2 )
			return array( $key, $wgContLanguageCode );

		$lang = array_pop( $pieces );
		$validCodes = Language::getLanguageNames();
		if( !array_key_exists( $lang, $validCodes ) )
			return array( $key, $wgContLanguageCode );

		$message = implode( '/', $pieces );
		return array( $message, $lang );
	}

}