MWException: Don't send headers multiple times

[mediawiki.git] / includes / MessageBlobStore.php

<?php
/**
 * Resource message blobs storage used by the resource loader.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @author Roan Kattouw
 * @author Trevor Parscal
 */

/**
 * This class provides access to the resource message blobs storage used by
 * the ResourceLoader.
 *
 * A message blob is a JSON object containing the interface messages for a
 * certain resource in a certain language. These message blobs are cached
 * in the msg_resource table and automatically invalidated when one of their
 * constituent messages or the resource itself is changed.
 */
class MessageBlobStore {
        /**
         * Get the message blobs for a set of modules
         *
         * @param ResourceLoader $resourceLoader
         * @param array $modules Array of module objects keyed by module name
         * @param string $lang Language code
         * @return array An array mapping module names to message blobs
         */
        public static function get( ResourceLoader $resourceLoader, $modules, $lang ) {
                wfProfileIn( __METHOD__ );
                if ( !count( $modules ) ) {
                        wfProfileOut( __METHOD__ );
                        return array();
                }
                // Try getting from the DB first
                $blobs = self::getFromDB( $resourceLoader, array_keys( $modules ), $lang );

                // Generate blobs for any missing modules and store them in the DB
                $missing = array_diff( array_keys( $modules ), array_keys( $blobs ) );
                foreach ( $missing as $name ) {
                        $blob = self::insertMessageBlob( $name, $modules[$name], $lang );
                        if ( $blob ) {
                                $blobs[$name] = $blob;
                        }
                }

                wfProfileOut( __METHOD__ );
                return $blobs;
        }

        /**
         * Generate and insert a new message blob. If the blob was already
         * present, it is not regenerated; instead, the preexisting blob
         * is fetched and returned.
         *
         * @param string $name Module name
         * @param ResourceLoaderModule $module
         * @param string $lang Language code
         * @return mixed Message blob or false if the module has no messages
         */
        public static function insertMessageBlob( $name, ResourceLoaderModule $module, $lang ) {
                $blob = self::generateMessageBlob( $module, $lang );

                if ( !$blob ) {
                        return false;
                }

                try {
                        $dbw = wfGetDB( DB_MASTER );
                        $success = $dbw->insert( 'msg_resource', array(
                                        'mr_lang' => $lang,
                                        'mr_resource' => $name,
                                        'mr_blob' => $blob,
                                        'mr_timestamp' => $dbw->timestamp()
                                ),
                                __METHOD__,
                                array( 'IGNORE' )
                        );

                        if ( $success ) {
                                if ( $dbw->affectedRows() == 0 ) {
                                        // Blob was already present, fetch it
                                        $blob = $dbw->selectField( 'msg_resource', 'mr_blob', array(
                                                        'mr_resource' => $name,
                                                        'mr_lang' => $lang,
                                                ),
                                                __METHOD__
                                        );
                                } else {
                                        // Update msg_resource_links
                                        $rows = array();

                                        foreach ( $module->getMessages() as $key ) {
                                                $rows[] = array(
                                                        'mrl_resource' => $name,
                                                        'mrl_message' => $key
                                                );
                                        }
                                        $dbw->insert( 'msg_resource_links', $rows,
                                                __METHOD__, array( 'IGNORE' )
                                        );
                                }
                        }
                } catch ( Exception $e ) {
                        wfDebug( __METHOD__ . " failed to update DB: $e\n" );
                }
                return $blob;
        }

        /**
         * Update the message blob for a given module in a given language
         *
         * @param string $name Module name
         * @param ResourceLoaderModule $module
         * @param string $lang Language code
         * @return string Regenerated message blob, or null if there was no blob for
         *   the given module/language pair.
         */
        public static function updateModule( $name, ResourceLoaderModule $module, $lang ) {
                $dbw = wfGetDB( DB_MASTER );
                $row = $dbw->selectRow( 'msg_resource', 'mr_blob',
                        array( 'mr_resource' => $name, 'mr_lang' => $lang ),
                        __METHOD__
                );
                if ( !$row ) {
                        return null;
                }

                // Save the old and new blobs for later
                $oldBlob = $row->mr_blob;
                $newBlob = self::generateMessageBlob( $module, $lang );

                try {
                        $newRow = array(
                                'mr_resource' => $name,
                                'mr_lang' => $lang,
                                'mr_blob' => $newBlob,
                                'mr_timestamp' => $dbw->timestamp()
                        );

                        $dbw->replace( 'msg_resource',
                                array( array( 'mr_resource', 'mr_lang' ) ),
                                $newRow, __METHOD__
                        );

                        // Figure out which messages were added and removed
                        $oldMessages = array_keys( FormatJson::decode( $oldBlob, true ) );
                        $newMessages = array_keys( FormatJson::decode( $newBlob, true ) );
                        $added = array_diff( $newMessages, $oldMessages );
                        $removed = array_diff( $oldMessages, $newMessages );

                        // Delete removed messages, insert added ones
                        if ( $removed ) {
                                $dbw->delete( 'msg_resource_links', array(
                                                'mrl_resource' => $name,
                                                'mrl_message' => $removed
                                        ), __METHOD__
                                );
                        }

                        $newLinksRows = array();

                        foreach ( $added as $message ) {
                                $newLinksRows[] = array(
                                        'mrl_resource' => $name,
                                        'mrl_message' => $message
                                );
                        }

                        if ( $newLinksRows ) {
                                $dbw->insert( 'msg_resource_links', $newLinksRows, __METHOD__,
                                        array( 'IGNORE' ) // just in case
                                );
                        }
                } catch ( Exception $e ) {
                        wfDebug( __METHOD__ . " failed to update DB: $e\n" );
                }
                return $newBlob;
        }

        /**
         * Update a single message in all message blobs it occurs in.
         *
         * @param string $key Message key
         */
        public static function updateMessage( $key ) {
                try {
                        $dbw = wfGetDB( DB_MASTER );

                        // Keep running until the updates queue is empty.
                        // Due to update conflicts, the queue might not be emptied
                        // in one iteration.
                        $updates = null;
                        do {
                                $updates = self::getUpdatesForMessage( $key, $updates );

                                foreach ( $updates as $k => $update ) {
                                        // Update the row on the condition that it
                                        // didn't change since we fetched it by putting
                                        // the timestamp in the WHERE clause.
                                        $success = $dbw->update( 'msg_resource',
                                                array(
                                                        'mr_blob' => $update['newBlob'],
                                                        'mr_timestamp' => $dbw->timestamp() ),
                                                array(
                                                        'mr_resource' => $update['resource'],
                                                        'mr_lang' => $update['lang'],
                                                        'mr_timestamp' => $update['timestamp'] ),
                                                __METHOD__
                                        );

                                        // Only requeue conflicted updates.
                                        // If update() returned false, don't retry, for
                                        // fear of getting into an infinite loop
                                        if ( !( $success && $dbw->affectedRows() == 0 ) ) {
                                                // Not conflicted
                                                unset( $updates[$k] );
                                        }
                                }
                        } while ( count( $updates ) );

                        // No need to update msg_resource_links because we didn't add
                        // or remove any messages, we just changed their contents.
                } catch ( Exception $e ) {
                        wfDebug( __METHOD__ . " failed to update DB: $e\n" );
                }
        }

        public static function clear() {
                // TODO: Give this some more thought
                try {
                        // Not using TRUNCATE, because that needs extra permissions,
                        // which maybe not granted to the database user.
                        $dbw = wfGetDB( DB_MASTER );
                        $dbw->delete( 'msg_resource', '*', __METHOD__ );
                        $dbw->delete( 'msg_resource_links', '*', __METHOD__ );
                } catch ( Exception $e ) {
                        wfDebug( __METHOD__ . " failed to update DB: $e\n" );
                }
        }

        /**
         * Create an update queue for updateMessage()
         *
         * @param string $key Message key
         * @param array $prevUpdates Updates queue to refresh or null to build a fresh update queue
         * @return array Updates queue
         */
        private static function getUpdatesForMessage( $key, $prevUpdates = null ) {
                $dbw = wfGetDB( DB_MASTER );

                if ( is_null( $prevUpdates ) ) {
                        // Fetch all blobs referencing $key
                        $res = $dbw->select(
                                array( 'msg_resource', 'msg_resource_links' ),
                                array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
                                array( 'mrl_message' => $key, 'mr_resource=mrl_resource' ),
                                __METHOD__
                        );
                } else {
                        // Refetch the blobs referenced by $prevUpdates

                        // Reorganize the (resource, lang) pairs in the format
                        // expected by makeWhereFrom2d()
                        $twoD = array();

                        foreach ( $prevUpdates as $update ) {
                                $twoD[$update['resource']][$update['lang']] = true;
                        }

                        $res = $dbw->select( 'msg_resource',
                                array( 'mr_resource', 'mr_lang', 'mr_blob', 'mr_timestamp' ),
                                $dbw->makeWhereFrom2d( $twoD, 'mr_resource', 'mr_lang' ),
                                __METHOD__
                        );
                }

                // Build the new updates queue
                $updates = array();

                foreach ( $res as $row ) {
                        $updates[] = array(
                                'resource' => $row->mr_resource,
                                'lang' => $row->mr_lang,
                                'timestamp' => $row->mr_timestamp,
                                'newBlob' => self::reencodeBlob( $row->mr_blob, $key, $row->mr_lang )
                        );
                }

                return $updates;
        }

        /**
         * Reencode a message blob with the updated value for a message
         *
         * @param string $blob Message blob (JSON object)
         * @param string $key Message key
         * @param string $lang Language code
         * @return string Message blob with $key replaced with its new value
         */
        private static function reencodeBlob( $blob, $key, $lang ) {
                $decoded = FormatJson::decode( $blob, true );
                $decoded[$key] = wfMessage( $key )->inLanguage( $lang )->plain();

                return FormatJson::encode( (object)$decoded );
        }

        /**
         * Get the message blobs for a set of modules from the database.
         * Modules whose blobs are not in the database are silently dropped.
         *
         * @param ResourceLoader $resourceLoader
         * @param array $modules Array of module names
         * @param string $lang Language code
         * @throws MWException
         * @return array Array mapping module names to blobs
         */
        private static function getFromDB( ResourceLoader $resourceLoader, $modules, $lang ) {
                global $wgCacheEpoch;

                $retval = array();
                $dbr = wfGetDB( DB_SLAVE );
                $res = $dbr->select( 'msg_resource',
                        array( 'mr_blob', 'mr_resource', 'mr_timestamp' ),
                        array( 'mr_resource' => $modules, 'mr_lang' => $lang ),
                        __METHOD__
                );

                foreach ( $res as $row ) {
                        $module = $resourceLoader->getModule( $row->mr_resource );
                        if ( !$module ) {
                                // This shouldn't be possible
                                throw new MWException( __METHOD__ . ' passed an invalid module name' );
                        }

                        // Update the module's blobs if the set of messages changed or if the blob is
                        // older than $wgCacheEpoch
                        $keys = array_keys( FormatJson::decode( $row->mr_blob, true ) );
                        $values = array_values( array_unique( $module->getMessages() ) );
                        if ( $keys !== $values
                                || wfTimestamp( TS_MW, $row->mr_timestamp ) <= $wgCacheEpoch
                        ) {
                                $retval[$row->mr_resource] = self::updateModule( $row->mr_resource, $module, $lang );
                        } else {
                                $retval[$row->mr_resource] = $row->mr_blob;
                        }
                }

                return $retval;
        }

        /**
         * Generate the message blob for a given module in a given language.
         *
         * @param ResourceLoaderModule $module
         * @param string $lang Language code
         * @return string JSON object
         */
        private static function generateMessageBlob( ResourceLoaderModule $module, $lang ) {
                $messages = array();

                foreach ( $module->getMessages() as $key ) {
                        $messages[$key] = wfMessage( $key )->inLanguage( $lang )->plain();
                }

                return FormatJson::encode( (object)$messages );
        }
}