invitation maybe button

		['name' => 'settings#setConfig', 'url' => '/v1/config/{key}', 'verb' => 'POST'],

		// Tools

		['name' => 'email#sendEmailPublicLink', 'url' => '/v1/public/sendmail', 'verb' => 'POST'],

		//Maybe invitiation

		['name' => 'invitation_maybe#tentative', 'url' => '/invitation/tentative/{token}', 'verb' => 'GET'],

	],

	'resources' => [

		'appointmentConfig' => ['url' => '/v1/appointment_configs']

<?php

declare(strict_types=1);

namespace OCA\Calendar\Controller;

use OCA\DAV\CalDAV\InvitationResponse\InvitationResponseServer;

use OCP\AppFramework\Controller;

use OCP\AppFramework\Http\TemplateResponse;

use OCP\AppFramework\Utility\ITimeFactory;

use OCP\IDBConnection;

use OCP\IRequest;

use Sabre\VObject\ITip\Message;

use Sabre\VObject\Reader;

class InvitationMaybeController extends Controller {

	/** @var IDBConnection */

	private $db;

	/** @var ITimeFactory */

	private $timeFactory;

	/** @var InvitationResponseServer */

	private $responseServer;

	/**

	 * InvitationResponseController constructor.

	 *

	 * @param string $appName

	 * @param IRequest $request

	 * @param IDBConnection $db

	 * @param ITimeFactory $timeFactory

	 * @param InvitationResponseServer $responseServer

	 */

	public function __construct(string $appName, IRequest $request,

								IDBConnection $db, ITimeFactory $timeFactory,

								InvitationResponseServer $responseServer) {

		parent::__construct($appName, $request);

		$this->db = $db;

		$this->timeFactory = $timeFactory;

		$this->responseServer = $responseServer;

		// Don't run `$server->exec()`, because we just need access to the

		// fully initialized schedule plugin, but we don't want Sabre/DAV

		// to actually handle and reply to the request

	}

	/**

	 * @PublicPage

	 * @NoCSRFRequired

	 *

	 * @param string $token

	 * @return TemplateResponse

	 */

	public function tentative(string $token):TemplateResponse {

		$row = $this->getTokenInformation($token);

		if (!$row) {

			return new TemplateResponse($this->appName, 'schedule-response-error', [], 'guest');

		}

		$iTipMessage = $this->buildITipResponse($row, 'TENTATIVE');

		$this->responseServer->handleITipMessage($iTipMessage);

		if ($iTipMessage->getScheduleStatus() === '1.2') {

			return new TemplateResponse($this->appName, 'schedule-response-success', [], 'guest');

		}

		return new TemplateResponse($this->appName, 'schedule-response-error', [

			'organizer' => $row['organizer'],

		], 'guest');

	}

	/**

	 * @param array $row

	 * @param string $partStat participation status of attendee - SEE RFC 5545

	 * @param int|null $guests

	 * @param string|null $comment

	 * @return Message

	 */

	private function buildITipResponse(array $row, string $partStat, int $guests = null,

									   string $comment = null):Message {

		$iTipMessage = new Message();

		$iTipMessage->uid = $row['uid'];

		$iTipMessage->component = 'VEVENT';

		$iTipMessage->method = 'REPLY';

		$iTipMessage->sequence = $row['sequence'];

		$iTipMessage->sender = $row['attendee'];

		if ($this->responseServer->isExternalAttendee($row['attendee'])) {

			$iTipMessage->recipient = $row['organizer'];

		} else {

			$iTipMessage->recipient = $row['attendee'];

		}

		$message = <<<EOF

BEGIN:VCALENDAR

PRODID:-//Nextcloud/Nextcloud CalDAV Server//EN

METHOD:REPLY

VERSION:2.0

BEGIN:VEVENT

ATTENDEE;PARTSTAT=%s:%s

ORGANIZER:%s

UID:%s

SEQUENCE:%s

REQUEST-STATUS:2.0;Success

%sEND:VEVENT

END:VCALENDAR

EOF;

		$vObject = Reader::read(vsprintf($message, [

			$partStat, $row['attendee'], $row['organizer'],

			$row['uid'], $row['sequence'] ?? 0, $row['recurrenceid'] ?? ''

		]));

		$vEvent = $vObject->{'VEVENT'};

		/** @var \Sabre\VObject\Property\ICalendar\CalAddress $attendee */

		$attendee = $vEvent->{'ATTENDEE'};

		$vEvent->DTSTAMP = date('Ymd\\THis\\Z', $this->timeFactory->getTime());

		if ($comment) {

			$attendee->add('X-RESPONSE-COMMENT', $comment);

			$vEvent->add('COMMENT', $comment);

		}

		if ($guests) {

			$attendee->add('X-NUM-GUESTS', $guests);

		}

		$iTipMessage->message = $vObject;

		return $iTipMessage;

	}

	/**

	 * @param string $token

	 * @return array|null

	 */

	private function getTokenInformation(string $token) {

		$query = $this->db->getQueryBuilder();

		$query->select('*')

			->from('calendar_invitations')

			->where($query->expr()->eq('token', $query->createNamedParameter($token)));

		$stmt = $query->execute();

		$row = $stmt->fetch(\PDO::FETCH_ASSOC);

		if (!$row) {

			return null;

		}

		$currentTime = $this->timeFactory->getTime();

		if (((int) $row['expiration']) < $currentTime) {

			return null;

		}

		return $row;

	}

}