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[mediawiki.git] / includes / interwiki / ClassicInterwikiLookup.php

<?php
namespace MediaWiki\Interwiki;

/**
 * InterwikiLookup implementing the "classic" interwiki storage (hardcoded up to MW 1.26).
 *
 * 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
 */
use \Cdb\Exception as CdbException;
use \Cdb\Reader as CdbReader;
use Database;
use Hooks;
use Interwiki;
use Language;
use MapCacheLRU;
use WANObjectCache;

/**
 * InterwikiLookup implementing the "classic" interwiki storage (hardcoded up to MW 1.26).
 *
 * This implements two levels of caching (in-process array and a WANObjectCache)
 * and tree storage backends (SQL, CDB, and plain PHP arrays).
 *
 * All information is loaded on creation when called by $this->fetch( $prefix ).
 * All work is done on replica DB, because this should *never* change (except during
 * schema updates etc, which aren't wiki-related)
 *
 * @since 1.28
 */
class ClassicInterwikiLookup implements InterwikiLookup {

        /**
         * @var MapCacheLRU
         */
        private $localCache;

        /**
         * @var Language
         */
        private $contentLanguage;

        /**
         * @var WANObjectCache
         */
        private $objectCache;

        /**
         * @var int
         */
        private $objectCacheExpiry;

        /**
         * @var bool|array|string
         */
        private $cdbData;

        /**
         * @var int
         */
        private $interwikiScopes;

        /**
         * @var string
         */
        private $fallbackSite;

        /**
         * @var CdbReader|null
         */
        private $cdbReader = null;

        /**
         * @var string|null
         */
        private $thisSite = null;

        /**
         * @param Language $contentLanguage Language object used to convert prefixes to lower case
         * @param WANObjectCache $objectCache Cache for interwiki info retrieved from the database
         * @param int $objectCacheExpiry Expiry time for $objectCache, in seconds
         * @param bool|array|string $cdbData The path of a CDB file, or
         *        an array resembling the contents of a CDB file,
         *        or false to use the database.
         * @param int $interwikiScopes Specify number of domains to check for messages:
         *    - 1: Just local wiki level
         *    - 2: wiki and global levels
         *    - 3: site level as well as wiki and global levels
         * @param string $fallbackSite The code to assume for the local site,
         */
        function __construct(
                Language $contentLanguage,
                WANObjectCache $objectCache,
                $objectCacheExpiry,
                $cdbData,
                $interwikiScopes,
                $fallbackSite
        ) {
                $this->localCache = new MapCacheLRU( 100 );

                $this->contentLanguage = $contentLanguage;
                $this->objectCache = $objectCache;
                $this->objectCacheExpiry = $objectCacheExpiry;
                $this->cdbData = $cdbData;
                $this->interwikiScopes = $interwikiScopes;
                $this->fallbackSite = $fallbackSite;
        }

        /**
         * Check whether an interwiki prefix exists
         *
         * @param string $prefix Interwiki prefix to use
         * @return bool Whether it exists
         */
        public function isValidInterwiki( $prefix ) {
                $result = $this->fetch( $prefix );

                return (bool)$result;
        }

        /**
         * Fetch an Interwiki object
         *
         * @param string $prefix Interwiki prefix to use
         * @return Interwiki|null|bool
         */
        public function fetch( $prefix ) {
                if ( $prefix == '' ) {
                        return null;
                }

                $prefix = $this->contentLanguage->lc( $prefix );
                if ( $this->localCache->has( $prefix ) ) {
                        return $this->localCache->get( $prefix );
                }

                if ( $this->cdbData ) {
                        $iw = $this->getInterwikiCached( $prefix );
                } else {
                        $iw = $this->load( $prefix );
                        if ( !$iw ) {
                                $iw = false;
                        }
                }
                $this->localCache->set( $prefix, $iw );

                return $iw;
        }

        /**
         * Resets locally cached Interwiki objects. This is intended for use during testing only.
         * This does not invalidate entries in the persistent cache, as invalidateCache() does.
         * @since 1.27
         */
        public function resetLocalCache() {
                $this->localCache->clear();
        }

        /**
         * Purge the in-process and object cache for an interwiki prefix
         * @param string $prefix
         */
        public function invalidateCache( $prefix ) {
                $this->localCache->clear( $prefix );

                $key = $this->objectCache->makeKey( 'interwiki', $prefix );
                $this->objectCache->delete( $key );
        }

        /**
         * Fetch interwiki prefix data from local cache in constant database.
         *
         * @note More logic is explained in DefaultSettings.
         *
         * @param string $prefix Interwiki prefix
         * @return Interwiki|false
         */
        private function getInterwikiCached( $prefix ) {
                $value = $this->getInterwikiCacheEntry( $prefix );

                if ( $value ) {
                        // Split values
                        list( $local, $url ) = explode( ' ', $value, 2 );
                        return new Interwiki( $prefix, $url, '', '', (int)$local );
                } else {
                        return false;
                }
        }

        /**
         * Get entry from interwiki cache
         *
         * @note More logic is explained in DefaultSettings.
         *
         * @param string $prefix Database key
         * @return bool|string The interwiki entry or false if not found
         */
        private function getInterwikiCacheEntry( $prefix ) {
                wfDebug( __METHOD__ . "( $prefix )\n" );
                $value = false;
                try {
                        // Resolve site name
                        if ( $this->interwikiScopes >= 3 && !$this->thisSite ) {
                                $this->thisSite = $this->getCacheValue( '__sites:' . wfWikiID() );
                                if ( $this->thisSite == '' ) {
                                        $this->thisSite = $this->fallbackSite;
                                }
                        }

                        $value = $this->getCacheValue( wfMemcKey( $prefix ) );
                        // Site level
                        if ( $value == '' && $this->interwikiScopes >= 3 ) {
                                $value = $this->getCacheValue( "_{$this->thisSite}:{$prefix}" );
                        }
                        // Global Level
                        if ( $value == '' && $this->interwikiScopes >= 2 ) {
                                $value = $this->getCacheValue( "__global:{$prefix}" );
                        }
                        if ( $value == 'undef' ) {
                                $value = '';
                        }
                } catch ( CdbException $e ) {
                        wfDebug( __METHOD__ . ": CdbException caught, error message was "
                                . $e->getMessage() );
                }

                return $value;
        }

        private function getCacheValue( $key ) {
                if ( $this->cdbReader === null ) {
                        if ( is_string( $this->cdbData ) ) {
                                $this->cdbReader = \Cdb\Reader::open( $this->cdbData );
                        } elseif ( is_array( $this->cdbData ) ) {
                                $this->cdbReader = new \Cdb\Reader\Hash( $this->cdbData );
                        } else {
                                $this->cdbReader = false;
                        }
                }

                if ( $this->cdbReader ) {
                        return $this->cdbReader->get( $key );
                } else {
                        return false;
                }
        }

        /**
         * Load the interwiki, trying first memcached then the DB
         *
         * @param string $prefix The interwiki prefix
         * @return Interwiki|bool Interwiki if $prefix is valid, otherwise false
         */
        private function load( $prefix ) {
                $iwData = [];
                if ( !Hooks::run( 'InterwikiLoadPrefix', [ $prefix, &$iwData ] ) ) {
                        return $this->loadFromArray( $iwData );
                }

                if ( is_array( $iwData ) ) {
                        $iw = $this->loadFromArray( $iwData );
                        if ( $iw ) {
                                return $iw; // handled by hook
                        }
                }

                $iwData = $this->objectCache->getWithSetCallback(
                        $this->objectCache->makeKey( 'interwiki', $prefix ),
                        $this->objectCacheExpiry,
                        function ( $oldValue, &$ttl, array &$setOpts ) use ( $prefix ) {
                                $dbr = wfGetDB( DB_REPLICA ); // TODO: inject LoadBalancer

                                $setOpts += Database::getCacheSetOptions( $dbr );

                                $row = $dbr->selectRow(
                                        'interwiki',
                                        ClassicInterwikiLookup::selectFields(),
                                        [ 'iw_prefix' => $prefix ],
                                        __METHOD__
                                );

                                return $row ? (array)$row : '!NONEXISTENT';
                        }
                );

                if ( is_array( $iwData ) ) {
                        return $this->loadFromArray( $iwData ) ?: false;
                }

                return false;
        }

        /**
         * Fill in member variables from an array (e.g. memcached result, Database::fetchRow, etc)
         *
         * @param array $mc Associative array: row from the interwiki table
         * @return Interwiki|bool Interwiki object or false if $mc['iw_url'] is not set
         */
        private function loadFromArray( $mc ) {
                if ( isset( $mc['iw_url'] ) ) {
                        $url = $mc['iw_url'];
                        $local = isset( $mc['iw_local'] ) ? $mc['iw_local'] : 0;
                        $trans = isset( $mc['iw_trans'] ) ? $mc['iw_trans'] : 0;
                        $api = isset( $mc['iw_api'] ) ? $mc['iw_api'] : '';
                        $wikiId = isset( $mc['iw_wikiid'] ) ? $mc['iw_wikiid'] : '';

                        return new Interwiki( null, $url, $api, $wikiId, $local, $trans );
                }

                return false;
        }

        /**
         * Fetch all interwiki prefixes from interwiki cache
         *
         * @param null|string $local If not null, limits output to local/non-local interwikis
         * @return array List of prefixes, where each row is an associative array
         */
        private function getAllPrefixesCached( $local ) {
                wfDebug( __METHOD__ . "()\n" );
                $data = [];
                try {
                        /* Resolve site name */
                        if ( $this->interwikiScopes >= 3 && !$this->thisSite ) {
                                $site = $this->getCacheValue( '__sites:' . wfWikiID() );

                                if ( $site == '' ) {
                                        $this->thisSite = $this->fallbackSite;
                                } else {
                                        $this->thisSite = $site;
                                }
                        }

                        // List of interwiki sources
                        $sources = [];
                        // Global Level
                        if ( $this->interwikiScopes >= 2 ) {
                                $sources[] = '__global';
                        }
                        // Site level
                        if ( $this->interwikiScopes >= 3 ) {
                                $sources[] = '_' . $this->thisSite;
                        }
                        $sources[] = wfWikiID();

                        foreach ( $sources as $source ) {
                                $list = $this->getCacheValue( '__list:' . $source );
                                foreach ( explode( ' ', $list ) as $iw_prefix ) {
                                        $row = $this->getCacheValue( "{$source}:{$iw_prefix}" );
                                        if ( !$row ) {
                                                continue;
                                        }

                                        list( $iw_local, $iw_url ) = explode( ' ', $row );

                                        if ( $local !== null && $local != $iw_local ) {
                                                continue;
                                        }

                                        $data[$iw_prefix] = [
                                                'iw_prefix' => $iw_prefix,
                                                'iw_url' => $iw_url,
                                                'iw_local' => $iw_local,
                                        ];
                                }
                        }
                } catch ( CdbException $e ) {
                        wfDebug( __METHOD__ . ": CdbException caught, error message was "
                                . $e->getMessage() );
                }

                ksort( $data );

                return array_values( $data );
        }

        /**
         * Fetch all interwiki prefixes from DB
         *
         * @param string|null $local If not null, limits output to local/non-local interwikis
         * @return array[] Interwiki rows
         */
        private function getAllPrefixesDB( $local ) {
                $db = wfGetDB( DB_REPLICA ); // TODO: inject DB LoadBalancer

                $where = [];

                if ( $local !== null ) {
                        if ( $local == 1 ) {
                                $where['iw_local'] = 1;
                        } elseif ( $local == 0 ) {
                                $where['iw_local'] = 0;
                        }
                }

                $res = $db->select( 'interwiki',
                        $this->selectFields(),
                        $where, __METHOD__, [ 'ORDER BY' => 'iw_prefix' ]
                );

                $retval = [];
                foreach ( $res as $row ) {
                        $retval[] = (array)$row;
                }

                return $retval;
        }

        /**
         * Returns all interwiki prefixes
         *
         * @param string|null $local If set, limits output to local/non-local interwikis
         * @return array[] Interwiki rows, where each row is an associative array
         */
        public function getAllPrefixes( $local = null ) {
                if ( $this->cdbData ) {
                        return $this->getAllPrefixesCached( $local );
                }

                return $this->getAllPrefixesDB( $local );
        }

        /**
         * Return the list of interwiki fields that should be selected to create
         * a new Interwiki object.
         * @return string[]
         */
        private static function selectFields() {
                return [
                        'iw_prefix',
                        'iw_url',
                        'iw_api',
                        'iw_wikiid',
                        'iw_local',
                        'iw_trans'
                ];
        }

}