<?php
/**
 * @copyright Copyright (c) 2016, ownCloud, Inc.
 *
 * @author Joas Schilling <coding@schilljs.com>
 * @author Jörn Friedrich Dreyer <jfd@butonic.de>
 * @author Lukas Reschke <lukas@statuscode.ch>
 * @author Morris Jobke <hey@morrisjobke.de>
 * @author Noveen Sachdeva <noveen.sachdeva@research.iiit.ac.in>
 * @author Robin Appelman <robin@icewind.nl>
 * @author Robin McCorkell <robin@mccorkell.me.uk>
 *
 * @license AGPL-3.0
 *
 * This code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * 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, version 3,
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

namespace OC\BackgroundJob;

use OCP\AppFramework\QueryException;
use OCP\AppFramework\Utility\ITimeFactory;
use OCP\BackgroundJob\IJob;
use OCP\BackgroundJob\IJobList;
use OCP\AutoloadNotAllowedException;
use OCP\DB\QueryBuilder\IQueryBuilder;
use OCP\IConfig;
use OCP\IDBConnection;

class JobList implements IJobList {

	/** @var IDBConnection */
	protected $connection;

	/**@var IConfig */
	protected $config;

	/**@var ITimeFactory */
	protected $timeFactory;

	/** @var int - 12 hours * 3600 seconds*/
	private $jobTimeOut = 43200;

	/**
	 * @param IDBConnection $connection
	 * @param IConfig $config
	 * @param ITimeFactory $timeFactory
	 */
	public function __construct(IDBConnection $connection, IConfig $config, ITimeFactory $timeFactory) {
		$this->connection = $connection;
		$this->config = $config;
		$this->timeFactory = $timeFactory;
	}

	/**
	 * @param IJob|string $job
	 * @param mixed $argument
	 */
	public function add($job, $argument = null) {
		if (!$this->has($job, $argument)) {
			if ($job instanceof IJob) {
				$class = get_class($job);
			} else {
				$class = $job;
			}

			$argument = json_encode($argument);
			if (strlen($argument) > 4000) {
				throw new \InvalidArgumentException('Background job arguments can\'t exceed 4000 characters (json encoded)');
			}

			$query = $this->connection->getQueryBuilder();
			$query->insert('jobs')
				->values([
					'class' => $query->createNamedParameter($class),
					'argument' => $query->createNamedParameter($argument),
					'last_run' => $query->createNamedParameter(0, IQueryBuilder::PARAM_INT),
					'last_checked' => $query->createNamedParameter($this->timeFactory->getTime(), IQueryBuilder::PARAM_INT),
				]);
			$query->execute();
		}
	}

	/**
	 * @param IJob|string $job
	 * @param mixed $argument
	 */
	public function remove($job, $argument = null) {
		if ($job instanceof IJob) {
			$class = get_class($job);
		} else {
			$class = $job;
		}

		$query = $this->connection->getQueryBuilder();
		$query->delete('jobs')
			->where($query->expr()->eq('class', $query->createNamedParameter($class)));
		if (!is_null($argument)) {
			$argument = json_encode($argument);
			$query->andWhere($query->expr()->eq('argument', $query->createNamedParameter($argument)));
		}
		$query->execute();
	}

	/**
	 * @param int $id
	 */
	protected function removeById($id) {
		$query = $this->connection->getQueryBuilder();
		$query->delete('jobs')
			->where($query->expr()->eq('id', $query->createNamedParameter($id, IQueryBuilder::PARAM_INT)));
		$query->execute();
	}

	/**
	 * check if a job is in the list
	 *
	 * @param IJob|string $job
	 * @param mixed $argument
	 * @return bool
	 */
	public function has($job, $argument) {
		if ($job instanceof IJob) {
			$class = get_class($job);
		} else {
			$class = $job;
		}
		$argument = json_encode($argument);

		$query = $this->connection->getQueryBuilder();
		$query->select('id')
			->from('jobs')
			->where($query->expr()->eq('class', $query->createNamedParameter($class)))
			->andWhere($query->expr()->eq('argument', $query->createNamedParameter($argument)))
			->setMaxResults(1);

		$result = $query->execute();
		$row = $result->fetch();
		$result->closeCursor();

		return (bool) $row;
	}

	/**
	 * get all jobs in the list
	 *
	 * @return IJob[]
	 * @deprecated 9.0.0 - This method is dangerous since it can cause load and
	 * memory problems when creating too many instances.
	 */
	public function getAll() {
		$query = $this->connection->getQueryBuilder();
		$query->select('*')
			->from('jobs');
		$result = $query->execute();

		$jobs = [];
		while ($row = $result->fetch()) {
			$job = $this->buildJob($row);
			if ($job) {
				$jobs[] = $job;
			}
		}
		$result->closeCursor();

		return $jobs;
	}

	/**
	 * get the next job in the list
	 *
	 * @return IJob|null
	 * @suppress SqlInjectionChecker
	 */
	public function getNext() {
		$query = $this->connection->getQueryBuilder();
		$query->select('*')
			->from('jobs')
			->where($query->expr()->lte('reserved_at', $query->createNamedParameter($this->timeFactory->getTime() - $this->jobTimeOut, IQueryBuilder::PARAM_INT)))
			->andWhere($query->expr()->lte('last_checked', $query->createNamedParameter($this->timeFactory->getTime(), IQueryBuilder::PARAM_INT)))
			->orderBy('last_checked', 'ASC')
			->setMaxResults(1);

		$update = $this->connection->getQueryBuilder();
		$update->update('jobs')
			->set('reserved_at', $update->createNamedParameter($this->timeFactory->getTime()))
			->set('last_checked', $update->createNamedParameter($this->timeFactory->getTime()))
			->where($update->expr()->eq('id', $update->createParameter('jobid')))
			->andWhere($update->expr()->eq('reserved_at', $update->createParameter('reserved_at')))
			->andWhere($update->expr()->eq('last_checked', $update->createParameter('last_checked')));

		$result = $query->execute();
		$row = $result->fetch();
		$result->closeCursor();

		if ($row) {
			$update->setParameter('jobid', $row['id']);
			$update->setParameter('reserved_at', $row['reserved_at']);
			$update->setParameter('last_checked', $row['last_checked']);
			$count = $update->execute();

			if ($count === 0) {
				// Background job already executed elsewhere, try again.
				return $this->getNext();
			}
			$job = $this->buildJob($row);

			if ($job === null) {
				// set the last_checked to 12h in the future to not check failing jobs all over again
				$reset = $this->connection->getQueryBuilder();
				$reset->update('jobs')
					->set('reserved_at', $reset->expr()->literal(0, IQueryBuilder::PARAM_INT))
					->set('last_checked', $reset->createNamedParameter($this->timeFactory->getTime() + 12 * 3600, IQueryBuilder::PARAM_INT))
					->where($reset->expr()->eq('id', $reset->createNamedParameter($row['id'], IQueryBuilder::PARAM_INT)));
				$reset->execute();

				// Background job from disabled app, try again.
				return $this->getNext();
			}

			return $job;
		} else {
			return null;
		}
	}

	/**
	 * @param int $id
	 * @return IJob|null
	 */
	public function getById($id) {
		$query = $this->connection->getQueryBuilder();
		$query->select('*')
			->from('jobs')
			->where($query->expr()->eq('id', $query->createNamedParameter($id, IQueryBuilder::PARAM_INT)));
		$result = $query->execute();
		$row = $result->fetch();
		$result->closeCursor();

		if ($row) {
			return $this->buildJob($row);
		} else {
			return null;
		}
	}

	/**
	 * get the job object from a row in the db
	 *
	 * @param array $row
	 * @return IJob|null
	 */
	private function buildJob($row) {
		try {
			try {
				// Try to load the job as a service
				/** @var IJob $job */
				$job = \OC::$server->query($row['class']);
			} catch (QueryException $e) {
				if (class_exists($row['class'])) {
					$class = $row['class'];
					$job = new $class();
				} else {
					// job from disabled app or old version of an app, no need to do anything
					return null;
				}
			}

			$job->setId($row['id']);
			$job->setLastRun($row['last_run']);
			$job->setArgument(json_decode($row['argument'], true));
			return $job;
		} catch (AutoloadNotAllowedException $e) {
			// job is from a disabled app, ignore
			return null;
		}
	}

	/**
	 * set the job that was last ran
	 *
	 * @param IJob $job
	 */
	public function setLastJob(IJob $job) {
		$this->unlockJob($job);
		$this->config->setAppValue('backgroundjob', 'lastjob', $job->getId());
	}

	/**
	 * Remove the reservation for a job
	 *
	 * @param IJob $job
	 * @suppress SqlInjectionChecker
	 */
	public function unlockJob(IJob $job) {
		$query = $this->connection->getQueryBuilder();
		$query->update('jobs')
			->set('reserved_at', $query->expr()->literal(0, IQueryBuilder::PARAM_INT))
			->where($query->expr()->eq('id', $query->createNamedParameter($job->getId(), IQueryBuilder::PARAM_INT)));
		$query->execute();
	}

	/**
	 * get the id of the last ran job
	 *
	 * @return int
	 * @deprecated 9.1.0 - The functionality behind the value is deprecated, it
	 *    only tells you which job finished last, but since we now allow multiple
	 *    executors to run in parallel, it's not used to calculate the next job.
	 */
	public function getLastJob() {
		return (int) $this->config->getAppValue('backgroundjob', 'lastjob', 0);
	}

	/**
	 * set the lastRun of $job to now
	 *
	 * @param IJob $job
	 */
	public function setLastRun(IJob $job) {
		$query = $this->connection->getQueryBuilder();
		$query->update('jobs')
			->set('last_run', $query->createNamedParameter(time(), IQueryBuilder::PARAM_INT))
			->where($query->expr()->eq('id', $query->createNamedParameter($job->getId(), IQueryBuilder::PARAM_INT)));
		$query->execute();
	}

	/**
	 * @param IJob $job
	 * @param $timeTaken
	 */
	public function setExecutionTime(IJob $job, $timeTaken) {
		$query = $this->connection->getQueryBuilder();
		$query->update('jobs')
			->set('execution_duration', $query->createNamedParameter($timeTaken, IQueryBuilder::PARAM_INT))
			->where($query->expr()->eq('id', $query->createNamedParameter($job->getId(), IQueryBuilder::PARAM_INT)));
		$query->execute();
	}

	/**
	 * checks if a job is still running (reserved_at time is smaller than 12 hours ago)
	 *
	 * Background information:
	 *
	 * The 12 hours is the same timeout that is also used to re-schedule an non-terminated
	 * job (see getNext()). The idea here is to give a job enough time to run very
	 * long but still be able to recognize that it maybe crashed and re-schedule it
	 * after the timeout. It's more likely to be crashed at that time than it ran
	 * that long.
	 *
	 * In theory it could lead to an nearly endless loop (as in - at most 12 hours).
	 * The cron command will not start new jobs when maintenance mode is active and
	 * this method is only executed in maintenance mode (see where it is called in
	 * the upgrader class. So this means in the worst case we wait 12 hours when a
	 * job has crashed. On the other hand: then the instance should be fixed anyways.
	 *
	 * @return bool
	 */
	public function isAnyJobRunning(): bool {
		$query = $this->connection->getQueryBuilder();
		$query->select('*')
			->from('jobs')
			->where($query->expr()->gt('reserved_at', $query->createNamedParameter($this->timeFactory->getTime() - $this->jobTimeOut, IQueryBuilder::PARAM_INT)))
			->setMaxResults(1);
		$result = $query->execute();
		$row = $result->fetch();
		$result->closeCursor();

		if ($row) {
			return true;
		}
		return false;
	}
}
