<?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
 */

use MediaWiki\Title\Title;
use MediaWiki\Title\TitleFactory;

/**
 * A class to convert page titles on a foreign wiki (ForeignTitle objects) into
 * page titles on the local wiki (Title objects), using a default namespace
 * mapping.
 *
 * For built-in namespaces (0 <= ID < 100), we try to find a local namespace
 * with the same namespace ID as the foreign page. If no such namespace exists,
 * or the namespace ID is unknown or > 100, we look for a local namespace with
 * a matching namespace name. If that can't be found, we dump the page in the
 * main namespace as a last resort.
 */
class NaiveImportTitleFactory implements ImportTitleFactory {
	/** @var Language */
	private $contentLanguage;

	/** @var NamespaceInfo */
	private $namespaceInfo;

	/** @var TitleFactory */
	private $titleFactory;

	/**
	 * @param Language $contentLanguage
	 * @param NamespaceInfo $namespaceInfo
	 * @param TitleFactory $titleFactory
	 */
	public function __construct(
		Language $contentLanguage,
		NamespaceInfo $namespaceInfo,
		TitleFactory $titleFactory
	) {
		$this->contentLanguage = $contentLanguage;
		$this->namespaceInfo = $namespaceInfo;
		$this->titleFactory = $titleFactory;
	}

	/**
	 * Determines which local title best corresponds to the given foreign title.
	 * If such a title can't be found or would be locally invalid, null is
	 * returned.
	 *
	 * @param ForeignTitle $foreignTitle The ForeignTitle to convert
	 * @return Title|null
	 */
	public function createTitleFromForeignTitle( ForeignTitle $foreignTitle ) {
		if ( $foreignTitle->isNamespaceIdKnown() ) {
			$foreignNs = $foreignTitle->getNamespaceId();

			// For built-in namespaces (0 <= ID < 100), we try to find a local NS with
			// the same namespace ID
			if (
				$foreignNs < 100 &&
				$this->namespaceInfo->exists( $foreignNs )
			) {
				return $this->titleFactory->makeTitleSafe( $foreignNs, $foreignTitle->getText() );
			}
		}

		// Do we have a local namespace by the same name as the foreign
		// namespace?
		$targetNs = $this->contentLanguage->getNsIndex( $foreignTitle->getNamespaceName() );
		if ( $targetNs !== false ) {
			return $this->titleFactory->makeTitleSafe( $targetNs, $foreignTitle->getText() );
		}

		// Otherwise, just fall back to main namespace
		return $this->titleFactory->makeTitleSafe( 0, $foreignTitle->getFullText() );
	}
}
