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diff --git a/www/wiki/includes/interwiki/ClassicInterwikiLookup.php b/www/wiki/includes/interwiki/ClassicInterwikiLookup.php
new file mode 100644
index 00000000..d5103da9
--- /dev/null
+++ b/www/wiki/includes/interwiki/ClassicInterwikiLookup.php
@@ -0,0 +1,452 @@
+<?php
+/**
+ * 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
+ */
+
+namespace MediaWiki\Interwiki;
+
+use Cdb\Exception as CdbException;
+use Cdb\Reader as CdbReader;
+use Hooks;
+use Interwiki;
+use Language;
+use MapCacheLRU;
+use WANObjectCache;
+use Wikimedia\Rdbms\Database;
+
+/**
+ * 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( wfWikiID() . ':' . $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',
+					self::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() );
+		}
+
+		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',
+			self::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'
+		];
+	}
+
+}
diff --git a/www/wiki/includes/interwiki/Interwiki.php b/www/wiki/includes/interwiki/Interwiki.php
new file mode 100644
index 00000000..5a996d9d
--- /dev/null
+++ b/www/wiki/includes/interwiki/Interwiki.php
@@ -0,0 +1,185 @@
+<?php
+/**
+ * Interwiki table entry.
+ *
+ * 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 MediaWiki\MediaWikiServices;
+
+/**
+ * Value object for representing interwiki records.
+ */
+class Interwiki {
+
+	/** @var string The interwiki prefix, (e.g. "Meatball", or the language prefix "de") */
+	protected $mPrefix;
+
+	/** @var string The URL of the wiki, with "$1" as a placeholder for an article name. */
+	protected $mURL;
+
+	/** @var string The URL of the file api.php */
+	protected $mAPI;
+
+	/** @var string The name of the database (for a connection to be established
+	 *    with wfGetLB( 'wikiid' ))
+	 */
+	protected $mWikiID;
+
+	/** @var bool Whether the wiki is in this project */
+	protected $mLocal;
+
+	/** @var bool Whether interwiki transclusions are allowed */
+	protected $mTrans;
+
+	public function __construct( $prefix = null, $url = '', $api = '', $wikiId = '', $local = 0,
+		$trans = 0
+	) {
+		$this->mPrefix = $prefix;
+		$this->mURL = $url;
+		$this->mAPI = $api;
+		$this->mWikiID = $wikiId;
+		$this->mLocal = (bool)$local;
+		$this->mTrans = (bool)$trans;
+	}
+
+	/**
+	 * Check whether an interwiki prefix exists
+	 *
+	 * @deprecated since 1.28, use InterwikiLookup instead
+	 *
+	 * @param string $prefix Interwiki prefix to use
+	 * @return bool Whether it exists
+	 */
+	public static function isValidInterwiki( $prefix ) {
+		return MediaWikiServices::getInstance()->getInterwikiLookup()->isValidInterwiki( $prefix );
+	}
+
+	/**
+	 * Fetch an Interwiki object
+	 *
+	 * @deprecated since 1.28, use InterwikiLookup instead
+	 *
+	 * @param string $prefix Interwiki prefix to use
+	 * @return Interwiki|null|bool
+	 */
+	public static function fetch( $prefix ) {
+		return MediaWikiServices::getInstance()->getInterwikiLookup()->fetch( $prefix );
+	}
+
+	/**
+	 * Purge the cache (local and persistent) for an interwiki prefix.
+	 *
+	 * @param string $prefix
+	 * @since 1.26
+	 */
+	public static function invalidateCache( $prefix ) {
+		MediaWikiServices::getInstance()->getInterwikiLookup()->invalidateCache( $prefix );
+	}
+
+	/**
+	 * Returns all interwiki prefix definitions.
+	 *
+	 * @deprecated since 1.28, unused. Use InterwikiLookup instead.
+	 *
+	 * @param string|null $local If set, limits output to local/non-local interwikis
+	 * @return array[] List of interwiki rows
+	 * @since 1.19
+	 */
+	public static function getAllPrefixes( $local = null ) {
+		return MediaWikiServices::getInstance()->getInterwikiLookup()->getAllPrefixes( $local );
+	}
+
+	/**
+	 * Get the URL for a particular title (or with $1 if no title given)
+	 *
+	 * @param string $title What text to put for the article name
+	 * @return string The URL
+	 * @note Prior to 1.19 The getURL with an argument was broken.
+	 *       If you if you use this arg in an extension that supports MW earlier
+	 *       than 1.19 please wfUrlencode and substitute $1 on your own.
+	 */
+	public function getURL( $title = null ) {
+		$url = $this->mURL;
+		if ( $title !== null ) {
+			$url = str_replace( "$1", wfUrlencode( $title ), $url );
+		}
+
+		return $url;
+	}
+
+	/**
+	 * Get the API URL for this wiki
+	 *
+	 * @return string The URL
+	 */
+	public function getAPI() {
+		return $this->mAPI;
+	}
+
+	/**
+	 * Get the DB name for this wiki
+	 *
+	 * @return string The DB name
+	 */
+	public function getWikiID() {
+		return $this->mWikiID;
+	}
+
+	/**
+	 * Is this a local link from a sister project, or is
+	 * it something outside, like Google
+	 *
+	 * @return bool
+	 */
+	public function isLocal() {
+		return $this->mLocal;
+	}
+
+	/**
+	 * Can pages from this wiki be transcluded?
+	 * Still requires $wgEnableScaryTransclusion
+	 *
+	 * @return bool
+	 */
+	public function isTranscludable() {
+		return $this->mTrans;
+	}
+
+	/**
+	 * Get the name for the interwiki site
+	 *
+	 * @return string
+	 */
+	public function getName() {
+		$msg = wfMessage( 'interwiki-name-' . $this->mPrefix )->inContentLanguage();
+
+		return !$msg->exists() ? '' : $msg->text();
+	}
+
+	/**
+	 * Get a description for this interwiki
+	 *
+	 * @return string
+	 */
+	public function getDescription() {
+		$msg = wfMessage( 'interwiki-desc-' . $this->mPrefix )->inContentLanguage();
+
+		return !$msg->exists() ? '' : $msg->text();
+	}
+
+}
diff --git a/www/wiki/includes/interwiki/InterwikiLookup.php b/www/wiki/includes/interwiki/InterwikiLookup.php
new file mode 100644
index 00000000..697e39d5
--- /dev/null
+++ b/www/wiki/includes/interwiki/InterwikiLookup.php
@@ -0,0 +1,74 @@
+<?php
+namespace MediaWiki\Interwiki;
+
+/**
+ * Service interface for looking up Interwiki records.
+ *
+ * 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 Interwiki;
+
+/**
+ * Service interface for looking up Interwiki records.
+ *
+ * @since 1.28
+ */
+interface InterwikiLookup {
+
+	/**
+	 * Check whether an interwiki prefix exists
+	 *
+	 * @param string $prefix Interwiki prefix to use
+	 * @return bool Whether it exists
+	 */
+	public function isValidInterwiki( $prefix );
+
+	/**
+	 * Fetch an Interwiki object
+	 *
+	 * @param string $prefix Interwiki prefix to use
+	 * @return Interwiki|null|bool
+	 */
+	public function fetch( $prefix );
+
+	/**
+	 * Returns information about all interwiki prefixes, in the form of rows
+	 * of the interwiki table. Each row may have the following keys:
+	 *
+	 * - iw_prefix: the prefix. Always present.
+	 * - iw_url: the URL to use for linking, with $1 as a placeholder for the target page.
+	 *           Always present.
+	 * - iw_api: the URL of the API. Optional.
+	 * - iw_wikiid: the wiki ID (usually the database name for local wikis). Optional.
+	 * - iw_local: whether the wiki is local, and the "magic redirect" mechanism should apply.
+	 *             Defaults to false.
+	 * - iw_trans: whether "scary transclusion" is allowed for this site.
+	 *             Defaults to false.
+	 *
+	 * @param string|null $local If set, limits output to local/non-local interwikis
+	 * @return array[] interwiki rows.
+	 */
+	public function getAllPrefixes( $local = null );
+
+	/**
+	 * Purge the in-process and persistent object cache for an interwiki prefix
+	 * @param string $prefix
+	 */
+	public function invalidateCache( $prefix );
+
+}
diff --git a/www/wiki/includes/interwiki/InterwikiLookupAdapter.php b/www/wiki/includes/interwiki/InterwikiLookupAdapter.php
new file mode 100644
index 00000000..076c37fe
--- /dev/null
+++ b/www/wiki/includes/interwiki/InterwikiLookupAdapter.php
@@ -0,0 +1,178 @@
+<?php
+namespace MediaWiki\Interwiki;
+
+/**
+ * InterwikiLookupAdapter on top of SiteLookup
+ *
+ * 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
+ *
+ * @since 1.29
+ * @ingroup InterwikiLookup
+ *
+ * @license GNU GPL v2+
+ */
+
+use Interwiki;
+use Site;
+use SiteLookup;
+use MediaWikiSite;
+
+class InterwikiLookupAdapter implements InterwikiLookup {
+
+	/**
+	 * @var SiteLookup
+	 */
+	private $siteLookup;
+
+	/**
+	 * @var Interwiki[]|null associative array mapping interwiki prefixes to Interwiki objects
+	 */
+	private $interwikiMap;
+
+	function __construct(
+		SiteLookup $siteLookup,
+		array $interwikiMap = null
+	) {
+		$this->siteLookup = $siteLookup;
+		$this->interwikiMap = $interwikiMap;
+	}
+
+	/**
+	 * See InterwikiLookup::isValidInterwiki
+	 * It loads the whole interwiki map.
+	 *
+	 * @param string $prefix Interwiki prefix to use
+	 * @return bool Whether it exists
+	 */
+	public function isValidInterwiki( $prefix ) {
+		return array_key_exists( $prefix, $this->getInterwikiMap() );
+	}
+
+	/**
+	 * See InterwikiLookup::fetch
+	 * It loads the whole interwiki map.
+	 *
+	 * @param string $prefix Interwiki prefix to use
+	 * @return Interwiki|null|bool
+	 */
+	public function fetch( $prefix ) {
+		if ( $prefix == '' ) {
+			return null;
+		}
+
+		if ( !$this->isValidInterwiki( $prefix ) ) {
+			return false;
+		}
+
+		return $this->interwikiMap[$prefix];
+	}
+
+	/**
+	 * See InterwikiLookup::getAllPrefixes
+	 *
+	 * @param string|null $local If set, limits output to local/non-local interwikis
+	 * @return array[] interwiki rows
+	 */
+	public function getAllPrefixes( $local = null ) {
+		$res = [];
+		foreach ( $this->getInterwikiMap() as $interwikiId => $interwiki ) {
+			if ( $local === null || $interwiki->isLocal() === $local ) {
+				$res[] = [
+					'iw_prefix' => $interwikiId,
+					'iw_url' => $interwiki->getURL(),
+					'iw_api' => $interwiki->getAPI(),
+					'iw_wikiid' => $interwiki->getWikiID(),
+					'iw_local' => $interwiki->isLocal(),
+					'iw_trans' => $interwiki->isTranscludable(),
+				];
+			}
+		}
+		return $res;
+	}
+
+	/**
+	 * See InterwikiLookup::invalidateCache
+	 *
+	 * @param string $prefix
+	 */
+	public function invalidateCache( $prefix ) {
+		if ( !isset( $this->interwikiMap[$prefix] ) ) {
+			return;
+		}
+		$globalId = $this->interwikiMap[$prefix]->getWikiID();
+		unset( $this->interwikiMap[$prefix] );
+
+		// Reload the interwiki
+		$site = $this->siteLookup->getSites()->getSite( $globalId );
+		$interwikis = $this->getSiteInterwikis( $site );
+		$this->interwikiMap = array_merge( $this->interwikiMap, [ $interwikis[$prefix] ] );
+	}
+
+	/**
+	 * Load interwiki map to use as cache
+	 */
+	private function loadInterwikiMap() {
+		$interwikiMap = [];
+		$siteList = $this->siteLookup->getSites();
+		foreach ( $siteList as $site ) {
+			$interwikis = $this->getSiteInterwikis( $site );
+			$interwikiMap = array_merge( $interwikiMap, $interwikis );
+		}
+		$this->interwikiMap = $interwikiMap;
+	}
+
+	/**
+	 * Get interwikiMap attribute, load if needed.
+	 *
+	 * @return Interwiki[]
+	 */
+	private function getInterwikiMap() {
+		if ( $this->interwikiMap === null ) {
+			$this->loadInterwikiMap();
+		}
+		return $this->interwikiMap;
+	}
+
+	/**
+	 * Load interwikis for the given site
+	 *
+	 * @param Site $site
+	 * @return Interwiki[]
+	 */
+	private function getSiteInterwikis( Site $site ) {
+		$interwikis = [];
+		foreach ( $site->getInterwikiIds() as $interwiki ) {
+			$url = $site->getPageUrl();
+			if ( $site instanceof MediaWikiSite ) {
+				$path = $site->getFileUrl( 'api.php' );
+			} else {
+				$path = '';
+			}
+			$local = $site->getSource() === 'local';
+			// TODO: How to adapt trans?
+			$interwikis[$interwiki] = new Interwiki(
+				$interwiki,
+				$url,
+				$path,
+				$site->getGlobalId(),
+				$local
+			);
+		}
+		return $interwikis;
+	}
+}
diff --git a/www/wiki/includes/interwiki/NullInterwikiLookup.php b/www/wiki/includes/interwiki/NullInterwikiLookup.php
new file mode 100644
index 00000000..09fa1ecd
--- /dev/null
+++ b/www/wiki/includes/interwiki/NullInterwikiLookup.php
@@ -0,0 +1,57 @@
+<?php
+/**
+ * Copyright (C) 2018 Kunal Mehta <legoktm@member.fsf.org>
+ *
+ * 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.
+ *
+ */
+
+namespace MediaWiki\Interwiki;
+
+/**
+ * An interwiki lookup that has no data, intended
+ * for use in the installer.
+ *
+ * @since 1.31
+ */
+class NullInterwikiLookup implements InterwikiLookup {
+
+	/**
+	 * @inheritDoc
+	 */
+	public function isValidInterwiki( $prefix ) {
+		return false;
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function fetch( $prefix ) {
+		return false;
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function getAllPrefixes( $local = null ) {
+		return [];
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public function invalidateCache( $prefix ) {
+	}
+}