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diff --git a/www/wiki/includes/collation/Collation.php b/www/wiki/includes/collation/Collation.php
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+<?php
+/**
+ * Database row sorting.
+ *
+ * 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 1.16.3
+ * @author Tim Starling
+ */
+abstract class Collation {
+	private static $instance;
+
+	/**
+	 * @since 1.16.3
+	 * @return Collation
+	 */
+	public static function singleton() {
+		if ( !self::$instance ) {
+			global $wgCategoryCollation;
+			self::$instance = self::factory( $wgCategoryCollation );
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * @since 1.16.3
+	 * @throws MWException
+	 * @param string $collationName
+	 * @return Collation
+	 */
+	public static function factory( $collationName ) {
+		global $wgContLang;
+
+		switch ( $collationName ) {
+			case 'uppercase':
+				return new UppercaseCollation;
+			case 'numeric':
+				return new NumericUppercaseCollation( $wgContLang );
+			case 'identity':
+				return new IdentityCollation;
+			case 'uca-default':
+				return new IcuCollation( 'root' );
+			case 'uca-default-u-kn':
+				return new IcuCollation( 'root-u-kn' );
+			case 'xx-uca-ckb':
+				return new CollationCkb;
+			case 'xx-uca-et':
+				return new CollationEt;
+			case 'xx-uca-fa':
+				return new CollationFa;
+			case 'uppercase-ab':
+				return new AbkhazUppercaseCollation;
+			case 'uppercase-ba':
+				return new BashkirUppercaseCollation;
+			case 'uppercase-se':
+				return new NorthernSamiUppercaseCollation;
+			default:
+				$match = [];
+				if ( preg_match( '/^uca-([A-Za-z@=-]+)$/', $collationName, $match ) ) {
+					return new IcuCollation( $match[1] );
+				}
+
+				# Provide a mechanism for extensions to hook in.
+				$collationObject = null;
+				Hooks::run( 'Collation::factory', [ $collationName, &$collationObject ] );
+
+				if ( $collationObject instanceof Collation ) {
+					return $collationObject;
+				}
+
+				// If all else fails...
+				throw new MWException( __METHOD__ . ": unknown collation type \"$collationName\"" );
+		}
+	}
+
+	/**
+	 * Given a string, convert it to a (hopefully short) key that can be used
+	 * for efficient sorting.  A binary sort according to the sortkeys
+	 * corresponds to a logical sort of the corresponding strings.  Current
+	 * code expects that a line feed character should sort before all others, but
+	 * has no other particular expectations (and that one can be changed if
+	 * necessary).
+	 *
+	 * @since 1.16.3
+	 *
+	 * @param string $string UTF-8 string
+	 * @return string Binary sortkey
+	 */
+	abstract function getSortKey( $string );
+
+	/**
+	 * Given a string, return the logical "first letter" to be used for
+	 * grouping on category pages and so on.  This has to be coordinated
+	 * carefully with convertToSortkey(), or else the sorted list might jump
+	 * back and forth between the same "initial letters" or other pathological
+	 * behavior.  For instance, if you just return the first character, but "a"
+	 * sorts the same as "A" based on getSortKey(), then you might get a
+	 * list like
+	 *
+	 * == A ==
+	 * * [[Aardvark]]
+	 *
+	 * == a ==
+	 * * [[antelope]]
+	 *
+	 * == A ==
+	 * * [[Ape]]
+	 *
+	 * etc., assuming for the sake of argument that $wgCapitalLinks is false.
+	 *
+	 * @since 1.16.3
+	 *
+	 * @param string $string UTF-8 string
+	 * @return string UTF-8 string corresponding to the first letter of input
+	 */
+	abstract function getFirstLetter( $string );
+
+}