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

	function __construct( &$memCached, $useDB, $expiry, $memcPrefix) {
		wfProfileIn( __METHOD__ );

		$this->mUseCache = !is_null( $memCached );
		$this->mMemc = &$memCached;
		$this->mDisable = !$useDB;
		$this->mExpiry = $expiry;
		$this->mDisableTransform = false;
		$this->mMemcKey = $memcPrefix.':messages';
		$this->mKeys = false; # initialised on demand
		$this->mInitialised = true;
		$this->mParser = null;

		wfProfileOut( __METHOD__ );
	}


	/**
	 * ParserOptions is lazy initialised.
	 * Access should probably be protected.
	 */
	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();
		if ( $code ) $filename .= '-' . $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 ) );
			} else {
				fclose( $file );
				return false; // Wrong hash
			}
		} else {
			$localHash=substr(fread($file,40),8);
			fclose($file);
			if ($hash!=$localHash) {
				return false; // Wrong hash
			}

			require( $filename );
			return $this->setCache( $this->mCache );
		}
	}

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

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

		# Make sure the directories exist
		$this->createCacheDir( $wgLocalMessageCache );

		$file = fopen( $filename, 'w' );
		if ( !$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();
		if ( $code ) $filename .= '-' . $code;
		$tempFilename = $filename . '.tmp';

		# Make sure the directories exist
		$this->createCacheDir( $wgLocalMessageCache );

		$file = fopen( $tempFilename, 'w');
		fwrite($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);
	}

	/**
	 * Creates directory with correct permissions.
	 *
	 * @param $path String: path that is created if it does not exist.
	 */
	protected function createCacheDir( $path ) {
		$oldUmask = umask( 0 );
		wfMkdirParents( $path, 0777 );
		umask( $oldUmask );
	}

	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 ) {
		if ( isset( $cache['VERSION'] ) && $cache['VERSION'] == MSG_CACHE_VERSION ) {
			if ( $this->mCache ) {
				$this->mCache = $cache + $this->mCache;
			} else {
				$this->mCache = $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 Mixed: if evaluates to false, messages for all languages is
	 *              loaded and stored in cache as one object. If code is provided
	 *              and $wgPerLanguageCaching is true, messages are loaded per
	 *              language and stored individually in caches 1 to 2.
	 */
	function load( $code = false ) {
		global $wgLocalMessageCache, $wgPerLanguageCaching;

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

		# Keep track of loaded messages. Either array of loaded codes as keys,
		# or just true if all languages are loaded.
		static $loaded = false;

		if ( !$wgPerLanguageCaching ) {
			// Disable language separation for normal use case
			$code = false;
		} elseif( !is_string( $code ) ) {
			# This isn't really nice, so at least make a note about it
			wfDebug( __METHOD__ . " called without providing a language code\n" );
		}

		# Don't do double loading...
		if ( $loaded === true || ($code && isset($loaded[$code])) ) return true;

		# Adjust cache key if we are handling only single language
		$cacheKey = wfMemcKeyLang( $this->mMemcKey, $code );

		# 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

		# (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 = $this->mMemc->get( "$cacheKey-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 );
			if ( $success ) {
				$where[] = 'got from global cache';
				$this->saveToCaches( $cache, $cacheKey, false );
			}
			wfProfileOut( __METHOD__ . '-fromcache' );
		}


		# (3)
		# Nothing in caches... so we need create one and store it in caches
		if ( !$success ) {
			$where[] = 'cache is empty';
			$this->lock($cacheKey);
			wfProfileIn( __METHOD__ . '-load' );
			$where[] = 'loading from database';
			# We want to store messages of particular language here, not everything
			# from mCache.
			$cache = $this->loadFromDB( $code );
			$success = $this->setCache( $cache );
			wfProfileOut( __METHOD__ . '-load' );
			if ( $success ) {
				$this->saveToCaches( $cache, $cacheKey );
			}
			$this->unlock($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" );
			if ( $code ) {
				$loaded[$code] = true;
			} else {
				$loaded = 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 ) {
			# Should $code be escaped?
			# 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
				$conds[] = "page_title like '%%/$code'";
			} 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, $wgPerLanguageCaching;

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

		# TODO: Should we define the sidebar key name somewhere?
		$sidebarKey = wfMemcKeyLang( 'sidebar' , $code );

		# Load only messages for affected language, if possible
		if ( !$wgPerLanguageCaching ) $code = false;
		$cacheKey = wfMemcKeyLang( $this->mMemcKey, $code );

		wfProfileIn( __METHOD__ );
		$this->lock($cacheKey);

		$cache = $this->mMemc->get( $cacheKey );
		if ( is_array( $cache ) ) {
			if ( $text === false ) {
				# Article was deleted
				unset( $this->mCache[$title] );
				$this->mMemc->delete( "$this->mMemcKey:{$title}" );
			} elseif ( strlen( $text ) > $wgMaxMsgCacheEntrySize ) {
				$cache[$title] = $this->mCache[$title] = '!TOO BIG';
				$this->mMemc->set( "$this->mMemcKey:{$title}", ' '.$text, $this->mExpiry );
			} else {
				$cache[$title] = $this->mCache[$title] = ' ' . $text;
				$this->mMemc->delete( "$this->mMemcKey:{$title}" );
			}

			# Update per-request cache
			$success = $this->setCache( $cache, $cacheKey );
			if ( $success ) {
				# And then all caches
				$this->saveToCaches( $cache, $cacheKey );
			}
		}
		$this->unlock($cacheKey);

		// Also delete cached sidebar... just in case it is affected
		global $parserMemc;
		$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.
	 * @return False on somekind of error.
	 */
	protected function saveToCaches( $cache, $cacheKey, $memc = true ) {
		wfProfileIn( __METHOD__ );
		global $wgLocalMessageCache, $wgLocalMessageCacheSerialized;

		$success = $this->mMemc->add( $cacheKey.'-status', "loading", MSG_LOAD_TIMEOUT );
		if ( !$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 );
			$this->mMemc->set( "$cacheKey-hash", $hash, $this->mExpiry );
			if ($wgLocalMessageCacheSerialized) {
				$this->saveToLocal( $serialized, $hash, $code );
			} else {
				$this->saveToScript( $cache, $hash, $code );
			}
		}

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

		# Identify which language to get or create a language object for.
		if( $langcode === $wgContLang->getCode() || $langcode === true ) {
			# $langcode is the language code of the wikis content language object.
			# or it is a boolean and value is true
			$lang =& $wgContLang;
		} elseif( $langcode === $wgLang->getCode() || $langcode === false ) {
			# $langcode is the language code of user language object.
			# or it was a boolean and value is false
			$lang =& $wgLang;
		} else {
			$validCodes = array_keys( Language::getLanguageNames() );
			if( in_array( $langcode, $validCodes ) ) {
				# $langcode corresponds to a valid language.
				$lang = Language::factory( $langcode );
			} else {
				# $langcode is a string, but not a valid language code; use content language.
				$lang =& $wgContLang;
				wfDebug( 'Invalid language code passed to MessageCache::get, falling back to content language.' );
			}
		}

		$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 ) {
				$validCodes = array_keys( Language::getLanguageNames() );
				if ( in_array( $code, $validCodes ) ) {
					$message = Language::getMessageFor( $mkey, $code );
					if ( is_null( $message ) ) {
						$message = false;
					}
				} else {
					wfDebug( __METHOD__ . ": Invalid code $code for $mkey/$code, not trying messages array\n" );
				}
			}
		}

		# 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 ) {
		$message = false;
		$type = false;

		if ( $this->mUseCache ) {
			if ( !isset($this->mCache[$title]) ) {
				# Delay loading as far as possible, and only load messages for requested
				# language.
				$this->load( $code );
			}
			if (isset( $this->mCache[$title] ) ) {
				$entry = $this->mCache[$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 != '!' && $message === false ) {
			return false;
		}

		$memcKey = $this->mMemcKey . ':' . $title;

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

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

			}
		}

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

	function transform( $message, $interface = false ) {
		global $wgParser;
		if ( !$this->mParser && isset( $wgParser ) ) {
			# Do some initialisation so that we don't have to do it twice
			$wgParser->firstCallInit();
			# Clone it and store it
			$this->mParser = clone $wgParser;
		}
		if ( $this->mParser ) {
			if( strpos( $message, '{{' ) !== false ) {
				$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() {
		global $wgLocalMessageCache;
		if( $this->mUseCache ) {
			# Global cache
			$this->mMemc->delete( $this->mMemcKey );
			# Invalidate all local caches
			$this->mMemc->delete( "{$this->mMemcKey}-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 );
	}

}