<?php

declare(strict_types=1);

/**
 * @copyright Copyright (c) 2021 Thomas Citharel <nextcloud@tcit.fr>
 *
 * @author Thomas Citharel <nextcloud@tcit.fr>
 *
 * @license GNU AGPL version 3 or any later version
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 */
namespace OCA\DAV\Migration;

use OCP\DB\Exception;
use OCP\IDBConnection;
use OCP\IUserManager;
use OCP\Migration\IOutput;
use OCP\Migration\IRepairStep;

class RemoveDeletedUsersCalendarSubscriptions implements IRepairStep {
	/** @var IDBConnection */
	private $connection;

	/** @var IUserManager */
	private $userManager;

	/** @var int */
	private $progress = 0;

	private $orphanSubscriptions = [];

	private const SUBSCRIPTIONS_CHUNK_SIZE = 1000;

	public function __construct(IDBConnection $connection, IUserManager $userManager) {
		$this->connection = $connection;
		$this->userManager = $userManager;
	}

	/**
	 * @inheritdoc
	 */
	public function getName(): string {
		return 'Clean up old calendar subscriptions from deleted users that were not cleaned-up';
	}

	/**
	 * @inheritdoc
	 */
	public function run(IOutput $output) {
		$nbSubscriptions = $this->countSubscriptions();

		$output->startProgress($nbSubscriptions);

		while ($this->progress < $nbSubscriptions) {
			$this->checkSubscriptions();

			$this->progress += self::SUBSCRIPTIONS_CHUNK_SIZE;
			$output->advance(min(self::SUBSCRIPTIONS_CHUNK_SIZE, $nbSubscriptions));
		}
		$output->finishProgress();
		$this->deleteOrphanSubscriptions();

		$output->info(sprintf('%d calendar subscriptions without an user have been cleaned up', count($this->orphanSubscriptions)));
	}

	/**
	 * @throws Exception
	 */
	private function countSubscriptions(): int {
		$qb = $this->connection->getQueryBuilder();
		$query = $qb->select($qb->func()->count('*'))
			->from('calendarsubscriptions');

		$result = $query->execute();
		$count = $result->fetchOne();
		$result->closeCursor();

		if ($count !== false) {
			$count = (int)$count;
		} else {
			$count = 0;
		}

		return $count;
	}

	/**
	 * @throws Exception
	 */
	private function checkSubscriptions(): void {
		$qb = $this->connection->getQueryBuilder();
		$query = $qb->selectDistinct(['id', 'principaluri'])
			->from('calendarsubscriptions')
			->setMaxResults(self::SUBSCRIPTIONS_CHUNK_SIZE)
			->setFirstResult($this->progress);

		$result = $query->execute();
		while ($row = $result->fetch()) {
			$username = $this->getPrincipal($row['principaluri']);
			if (!$this->userManager->userExists($username)) {
				$this->orphanSubscriptions[] = $row['id'];
			}
		}
		$result->closeCursor();
	}

	/**
	 * @throws Exception
	 */
	private function deleteOrphanSubscriptions(): void {
		foreach ($this->orphanSubscriptions as $orphanSubscriptionID) {
			$this->deleteOrphanSubscription($orphanSubscriptionID);
		}
	}

	/**
	 * @throws Exception
	 */
	private function deleteOrphanSubscription(int $orphanSubscriptionID): void {
		$qb = $this->connection->getQueryBuilder();
		$qb->delete('calendarsubscriptions')
			->where($qb->expr()->eq('id', $qb->createNamedParameter($orphanSubscriptionID)))
			->executeStatement();
	}

	private function getPrincipal(string $principalUri): string {
		$uri = explode('/', $principalUri);
		return array_pop($uri);
	}
}
