+<?php
+/**
+ * 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
+ * @ingroup Language
+ */
+
+/**
+ * Methods for dealing with language codes.
+ * @todo Move some of the code-related static methods out of Language into this class
+ *
+ * @since 1.29
+ * @ingroup Language
+ */
+class LanguageCode {
+ /**
+ * Returns a mapping of deprecated language codes that were used in previous
+ * versions of MediaWiki to up-to-date, current language codes.
+ *
+ * This array is merged into $wgDummyLanguageCodes in Setup.php, along with
+ * the fake language codes 'qqq' and 'qqx', which are used internally by
+ * MediaWiki's localisation system.
+ *
+ * @return string[]
+ */
+ public static function getDeprecatedCodeMapping() {
+ return [
+ // Note that als is actually a valid ISO 639 code (Tosk Albanian), but it
+ // was previously used in MediaWiki for Alsatian, which comes under gsw
+ 'als' => 'gsw',
+ 'bat-smg' => 'sgs',
+ 'be-x-old' => 'be-tarask',
+ 'fiu-vro' => 'vro',
+ 'roa-rup' => 'rup',
+ 'zh-classical' => 'lzh',
+ 'zh-min-nan' => 'nan',
+ 'zh-yue' => 'yue',
+ ];
+ }
+}