<?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
 */

/**
 * Collation that orders text with numbers "naturally", so that 'Foo 1' < 'Foo 2' < 'Foo 12'.
 *
 * Note that this only works in terms of sequences of digits, and the behavior for decimal fractions
 * or pretty-formatted numbers may be unexpected.
 *
 * @since 1.28
 */
class NumericUppercaseCollation extends UppercaseCollation {
	public function getSortKey( $string ) {
		$sortkey = parent::getSortKey( $string );

		// For each sequence of digits, insert the digit '0' and then the length of the sequence
		// (encoded in two bytes) before it. That's all folks, it sorts correctly now! The '0' ensures
		// correct position (where digits would normally sort), then the length will be compared putting
		// shorter numbers before longer ones; if identical, then the characters will be compared, which
		// generates the correct results for numbers of equal length.
		$sortkey = preg_replace_callback( '/\d+/', function ( $matches ) {
			$len = strlen( $matches[0] );
			// This allows sequences of up to 65536 numeric characters to be handled correctly. One byte
			// would allow only for 256, which doesn't feel future-proof.
			$prefix = chr( floor( $len / 256 ) ) . chr( $len % 256 );
			return '0' . $prefix . $matches[0];
		}, $sortkey );

		return $sortkey;
	}

	public function getFirstLetter( $string ) {
		if ( preg_match( '/^\d/', $string ) ) {
			// Note that we pass 0 and 9 as normal params, not numParams(). This only works for 0-9
			// and not localised digits, so we don't want them to be converted.
			return wfMessage( 'category-header-numerals' )->params( 0, 9 )->text();
		} else {
			return parent::getFirstLetter( $string );
		}
	}
}