<?php
/**
 * @copyright Copyright (c) 2016, ownCloud, Inc.
 *
 * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
 * @author Christoph Wurst <christoph@winzerhof-wurst.at>
 * @author Joas Schilling <coding@schilljs.com>
 * @author Lukas Reschke <lukas@statuscode.ch>
 * @author Morris Jobke <hey@morrisjobke.de>
 * @author Roeland Jago Douma <roeland@famdouma.nl>
 * @author Thomas Citharel <nextcloud@tcit.fr>
 * @author Thomas Müller <thomas.mueller@tmit.eu>
 *
 * @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 OCA\DAV\DAV\Sharing;

use OCA\DAV\Connector\Sabre\Principal;
use OCP\AppFramework\Db\TTransactional;
use OCP\Cache\CappedMemoryCache;
use OCP\DB\QueryBuilder\IQueryBuilder;
use OCP\IDBConnection;
use OCP\IGroupManager;
use OCP\IUserManager;

class Backend {
	use TTransactional;

	private IDBConnection $db;
	private IUserManager $userManager;
	private IGroupManager $groupManager;
	private Principal $principalBackend;
	private string $resourceType;

	public const ACCESS_OWNER = 1;
	public const ACCESS_READ_WRITE = 2;
	public const ACCESS_READ = 3;

	private CappedMemoryCache $shareCache;

	public function __construct(IDBConnection $db, IUserManager $userManager, IGroupManager $groupManager, Principal $principalBackend, string $resourceType) {
		$this->db = $db;
		$this->userManager = $userManager;
		$this->groupManager = $groupManager;
		$this->principalBackend = $principalBackend;
		$this->resourceType = $resourceType;
		$this->shareCache = new CappedMemoryCache();
	}

	/**
	 * @param list<array{href: string, commonName: string, readOnly: bool}> $add
	 * @param list<string> $remove
	 */
	public function updateShares(IShareable $shareable, array $add, array $remove): void {
		$this->shareCache->clear();
		$this->atomic(function () use ($shareable, $add, $remove) {
			foreach ($add as $element) {
				$principal = $this->principalBackend->findByUri($element['href'], '');
				if ($principal !== '') {
					$this->shareWith($shareable, $element);
				}
			}
			foreach ($remove as $element) {
				$principal = $this->principalBackend->findByUri($element, '');
				if ($principal !== '') {
					$this->unshare($shareable, $element);
				}
			}
		}, $this->db);
	}

	/**
	 * @param array{href: string, commonName: string, readOnly: bool} $element
	 */
	private function shareWith(IShareable $shareable, array $element): void {
		$this->shareCache->clear();
		$user = $element['href'];
		$parts = explode(':', $user, 2);
		if ($parts[0] !== 'principal') {
			return;
		}

		// don't share with owner
		if ($shareable->getOwner() === $parts[1]) {
			return;
		}

		$principal = explode('/', $parts[1], 3);
		if (count($principal) !== 3 || $principal[0] !== 'principals' || !in_array($principal[1], ['users', 'groups', 'circles'], true)) {
			// Invalid principal
			return;
		}

		$principal[2] = urldecode($principal[2]);
		if (($principal[1] === 'users' && !$this->userManager->userExists($principal[2])) ||
			($principal[1] === 'groups' && !$this->groupManager->groupExists($principal[2]))) {
			// User or group does not exist
			return;
		}

		// remove the share if it already exists
		$this->unshare($shareable, $element['href']);
		$access = self::ACCESS_READ;
		if (isset($element['readOnly'])) {
			$access = $element['readOnly'] ? self::ACCESS_READ : self::ACCESS_READ_WRITE;
		}

		$query = $this->db->getQueryBuilder();
		$query->insert('dav_shares')
			->values([
				'principaluri' => $query->createNamedParameter($parts[1]),
				'type' => $query->createNamedParameter($this->resourceType),
				'access' => $query->createNamedParameter($access),
				'resourceid' => $query->createNamedParameter($shareable->getResourceId())
			]);
		$query->executeStatement();
	}

	public function deleteAllShares(int $resourceId): void {
		$this->shareCache->clear();
		$query = $this->db->getQueryBuilder();
		$query->delete('dav_shares')
			->where($query->expr()->eq('resourceid', $query->createNamedParameter($resourceId)))
			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
			->executeStatement();
	}

	public function deleteAllSharesByUser(string $principaluri): void {
		$this->shareCache->clear();
		$query = $this->db->getQueryBuilder();
		$query->delete('dav_shares')
			->where($query->expr()->eq('principaluri', $query->createNamedParameter($principaluri)))
			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
			->executeStatement();
	}

	private function unshare(IShareable $shareable, string $element): void {
		$this->shareCache->clear();
		$parts = explode(':', $element, 2);
		if ($parts[0] !== 'principal') {
			return;
		}

		// don't share with owner
		if ($shareable->getOwner() === $parts[1]) {
			return;
		}

		$query = $this->db->getQueryBuilder();
		$query->delete('dav_shares')
			->where($query->expr()->eq('resourceid', $query->createNamedParameter($shareable->getResourceId())))
			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
			->andWhere($query->expr()->eq('principaluri', $query->createNamedParameter($parts[1])))
		;
		$query->executeStatement();
	}

	/**
	 * Returns the list of people whom this resource is shared with.
	 *
	 * Every element in this array should have the following properties:
	 *   * href - Often a mailto: address
	 *   * commonName - Optional, for example a first + last name
	 *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
	 *   * readOnly - boolean
	 *
	 * @param int $resourceId
	 * @return list<array{href: string, commonName: string, status: int, readOnly: bool, '{http://owncloud.org/ns}principal': string, '{http://owncloud.org/ns}group-share': bool}>
	 */
	public function getShares(int $resourceId): array {
		$cached = $this->shareCache->get($resourceId);
		if ($cached) {
			return $cached;
		}
		$query = $this->db->getQueryBuilder();
		$result = $query->select(['principaluri', 'access'])
			->from('dav_shares')
			->where($query->expr()->eq('resourceid', $query->createNamedParameter($resourceId, IQueryBuilder::PARAM_INT)))
			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
			->groupBy(['principaluri', 'access'])
			->executeQuery();

		$shares = [];
		while ($row = $result->fetch()) {
			$p = $this->principalBackend->getPrincipalByPath($row['principaluri']);
			$shares[] = [
				'href' => "principal:{$row['principaluri']}",
				'commonName' => isset($p['{DAV:}displayname']) ? (string)$p['{DAV:}displayname'] : '',
				'status' => 1,
				'readOnly' => (int) $row['access'] === self::ACCESS_READ,
				'{http://owncloud.org/ns}principal' => (string)$row['principaluri'],
				'{http://owncloud.org/ns}group-share' => isset($p['uri']) ? str_starts_with($p['uri'], 'principals/groups') : false
			];
		}

		$this->shareCache->set((string)$resourceId, $shares);
		return $shares;
	}

	public function preloadShares(array $resourceIds): void {
		$resourceIds = array_filter($resourceIds, function (int $resourceId) {
			return !isset($this->shareCache[$resourceId]);
		});
		if (count($resourceIds) === 0) {
			return;
		}
		$query = $this->db->getQueryBuilder();
		$result = $query->select(['resourceid', 'principaluri', 'access'])
			->from('dav_shares')
			->where($query->expr()->in('resourceid', $query->createNamedParameter($resourceIds, IQueryBuilder::PARAM_INT_ARRAY)))
			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
			->groupBy(['principaluri', 'access', 'resourceid'])
			->executeQuery();

		$sharesByResource = array_fill_keys($resourceIds, []);
		while ($row = $result->fetch()) {
			$resourceId = (int)$row['resourceid'];
			$p = $this->principalBackend->getPrincipalByPath($row['principaluri']);
			$sharesByResource[$resourceId][] = [
				'href' => "principal:{$row['principaluri']}",
				'commonName' => isset($p['{DAV:}displayname']) ? (string)$p['{DAV:}displayname'] : '',
				'status' => 1,
				'readOnly' => (int) $row['access'] === self::ACCESS_READ,
				'{http://owncloud.org/ns}principal' => (string)$row['principaluri'],
				'{http://owncloud.org/ns}group-share' => isset($p['uri']) ? str_starts_with($p['uri'], 'principals/groups') : false
			];
		}

		foreach ($resourceIds as $resourceId) {
			$this->shareCache->set($resourceId, $sharesByResource[$resourceId]);
		}
	}

	/**
	 * For shared resources the sharee is set in the ACL of the resource
	 *
	 * @param int $resourceId
	 * @param list<array{privilege: string, principal: string, protected: bool}> $acl
	 * @return list<array{privilege: string, principal: string, protected: bool}>
	 */
	public function applyShareAcl(int $resourceId, array $acl): array {
		$shares = $this->getShares($resourceId);
		foreach ($shares as $share) {
			$acl[] = [
				'privilege' => '{DAV:}read',
				'principal' => $share['{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}principal'],
				'protected' => true,
			];
			if (!$share['readOnly']) {
				$acl[] = [
					'privilege' => '{DAV:}write',
					'principal' => $share['{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}principal'],
					'protected' => true,
				];
			} elseif ($this->resourceType === 'calendar') {
				// Allow changing the properties of read only calendars,
				// so users can change the visibility.
				$acl[] = [
					'privilege' => '{DAV:}write-properties',
					'principal' => $share['{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}principal'],
					'protected' => true,
				];
			}
		}
		return $acl;
	}
}
