<?php

/**
 * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
 * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
 * SPDX-FileCopyrightText: 2007-2015 fruux GmbH (https://fruux.com/)
 * SPDX-License-Identifier: AGPL-3.0-only
 */
namespace OCA\DAV\CalDAV\Schedule;

use OCA\DAV\CalDAV\CalendarObject;
use OCA\DAV\CalDAV\EventComparisonService;
use OCP\AppFramework\Utility\ITimeFactory;
use OCP\Defaults;
use OCP\IAppConfig;
use OCP\IUserSession;
use OCP\Mail\IEmailValidator;
use OCP\Mail\IMailer;
use OCP\Mail\Provider\Address;
use OCP\Mail\Provider\Attachment;
use OCP\Mail\Provider\IManager as IMailManager;
use OCP\Mail\Provider\IMessageSend;
use OCP\Util;
use Psr\Log\LoggerInterface;
use Sabre\CalDAV\Schedule\IMipPlugin as SabreIMipPlugin;
use Sabre\DAV;
use Sabre\DAV\INode;
use Sabre\VObject\Component\VCalendar;
use Sabre\VObject\Component\VEvent;
use Sabre\VObject\ITip\Message;
use Sabre\VObject\Parameter;
use Sabre\VObject\Reader;

/**
 * iMIP handler.
 *
 * This class is responsible for sending out iMIP messages. iMIP is the
 * email-based transport for iTIP. iTIP deals with scheduling operations for
 * iCalendar objects.
 *
 * If you want to customize the email that gets sent out, you can do so by
 * extending this class and overriding the sendMessage method.
 *
 * @copyright Copyright (C) 2007-2015 fruux GmbH (https://fruux.com/).
 * @author Evert Pot (http://evertpot.com/)
 * @license http://sabre.io/license/ Modified BSD License
 */
class IMipPlugin extends SabreIMipPlugin {

	private ?VCalendar $vCalendar = null;
	public const MAX_DATE = '2038-01-01';
	public const METHOD_REQUEST = 'request';
	public const METHOD_REPLY = 'reply';
	public const METHOD_CANCEL = 'cancel';
	public const IMIP_INDENT = 15;

	public function __construct(
		private IAppConfig $config,
		private IMailer $mailer,
		private LoggerInterface $logger,
		private ITimeFactory $timeFactory,
		private Defaults $defaults,
		private IUserSession $userSession,
		private IMipService $imipService,
		private EventComparisonService $eventComparisonService,
		private IMailManager $mailManager,
		private IEmailValidator $emailValidator,
	) {
		parent::__construct('');
	}

	public function initialize(DAV\Server $server): void {
		parent::initialize($server);
		$server->on('beforeWriteContent', [$this, 'beforeWriteContent'], 10);
	}

	/**
	 * Check quota before writing content
	 *
	 * @param string $uri target file URI
	 * @param INode $node Sabre Node
	 * @param resource $data data
	 * @param bool $modified modified
	 */
	public function beforeWriteContent($uri, INode $node, $data, $modified): void {
		if (!$node instanceof CalendarObject) {
			return;
		}
		/** @var VCalendar $vCalendar */
		$vCalendar = Reader::read($node->get());
		$this->setVCalendar($vCalendar);
	}

	/**
	 * Event handler for the 'schedule' event.
	 *
	 * @param Message $iTipMessage
	 * @return void
	 */
	public function schedule(Message $iTipMessage) {

		// Not sending any emails if the system considers the update insignificant
		if (!$iTipMessage->significantChange) {
			if (!$iTipMessage->scheduleStatus) {
				$iTipMessage->scheduleStatus = '1.0;We got the message, but it\'s not significant enough to warrant an email';
			}
			return;
		}

		if (parse_url($iTipMessage->sender, PHP_URL_SCHEME) !== 'mailto'
			|| parse_url($iTipMessage->recipient, PHP_URL_SCHEME) !== 'mailto') {
			return;
		}

		// don't send out mails for events that already took place
		$lastOccurrence = $this->imipService->getLastOccurrence($iTipMessage->message);
		$currentTime = $this->timeFactory->getTime();
		if ($lastOccurrence < $currentTime) {
			return;
		}

		// Strip off mailto:
		$recipient = substr($iTipMessage->recipient, 7);
		if (!$this->emailValidator->isValid($recipient)) {
			// Nothing to send if the recipient doesn't have a valid email address
			$iTipMessage->scheduleStatus = '5.0; EMail delivery failed';
			return;
		}

		// Check if external attendees are disabled
		$externalAttendeesDisabled = $this->config->getValueBool('dav', 'caldav_external_attendees_disabled', false);
		if ($externalAttendeesDisabled && !$this->imipService->isSystemUser($recipient)) {
			$this->logger->debug('Invitation not sent to external attendee (external attendees disabled)', [
				'uid' => $iTipMessage->uid,
				'attendee' => $recipient,
			]);
			$iTipMessage->scheduleStatus = '5.0; External attendees are disabled';
			return;
		}

		$recipientName = $iTipMessage->recipientName ? (string)$iTipMessage->recipientName : null;

		$newEvents = $iTipMessage->message;
		$oldEvents = $this->getVCalendar();

		$modified = $this->eventComparisonService->findModified($newEvents, $oldEvents);
		/** @var VEvent $vEvent */
		$vEvent = array_pop($modified['new']);
		/** @var VEvent $oldVevent */
		$oldVevent = !empty($modified['old']) && is_array($modified['old']) ? array_pop($modified['old']) : null;
		$isModified = isset($oldVevent);

		// No changed events after all - this shouldn't happen if there is significant change yet here we are
		// The scheduling status is debatable
		if (empty($vEvent)) {
			$this->logger->warning('iTip message said the change was significant but comparison did not detect any updated VEvents');
			$iTipMessage->scheduleStatus = '1.0;We got the message, but it\'s not significant enough to warrant an email';
			return;
		}

		// we (should) have one event component left
		// as the ITip\Broker creates one iTip message per change
		// and triggers the "schedule" event once per message
		// we also might not have an old event as this could be a new
		// invitation, or a new recurrence exception
		$attendee = $this->imipService->getCurrentAttendee($iTipMessage);
		if ($attendee === null) {
			$uid = $vEvent->UID ?? 'no UID found';
			$this->logger->debug('Could not find recipient ' . $recipient . ' as attendee for event with UID ' . $uid);
			$iTipMessage->scheduleStatus = '5.0; EMail delivery failed';
			return;
		}
		// Don't send emails to rooms, resources and circles
		if ($this->imipService->isRoomOrResource($attendee)
				|| $this->imipService->isCircle($attendee)) {
			$this->logger->debug('No invitation sent as recipient is room, resource or circle', [
				'attendee' => $recipient,
			]);
			$iTipMessage->scheduleStatus = '1.0;We got the message, but it\'s not significant enough to warrant an email';
			return;
		}
		$this->imipService->setL10nFromAttendee($attendee);

		// Build the sender name.
		// Due to a bug in sabre, the senderName property for an iTIP message can actually also be a VObject Property
		// If the iTIP message senderName is null or empty use the user session name as the senderName
		if (($iTipMessage->senderName instanceof Parameter) && !empty(trim($iTipMessage->senderName->getValue()))) {
			$senderName = trim($iTipMessage->senderName->getValue());
		} elseif (is_string($iTipMessage->senderName) && !empty(trim($iTipMessage->senderName))) {
			$senderName = trim($iTipMessage->senderName);
		} elseif ($this->userSession->getUser() !== null) {
			$senderName = trim($this->userSession->getUser()->getDisplayName());
		} else {
			$senderName = '';
		}

		$sender = substr($iTipMessage->sender, 7);

		$replyingAttendee = null;
		switch (strtolower($iTipMessage->method)) {
			case self::METHOD_REPLY:
				$method = self::METHOD_REPLY;
				$data = $this->imipService->buildReplyBodyData($vEvent);
				$replyingAttendee = $this->imipService->getReplyingAttendee($iTipMessage);
				break;
			case self::METHOD_CANCEL:
				$method = self::METHOD_CANCEL;
				$data = $this->imipService->buildCancelledBodyData($vEvent);
				break;
			default:
				$method = self::METHOD_REQUEST;
				$data = $this->imipService->buildBodyData($vEvent, $oldVevent);
				break;
		}

		$data['attendee_name'] = ($recipientName ?: $recipient);
		$data['invitee_name'] = ($senderName ?: $sender);

		$fromEMail = Util::getDefaultEmailAddress('invitations-noreply');
		$fromName = $this->imipService->getFrom($senderName, $this->defaults->getName());

		$template = $this->mailer->createEMailTemplate('dav.calendarInvite.' . $method, $data);
		$template->addHeader();

		$this->imipService->addSubjectAndHeading($template, $method, $data['invitee_name'], $data['meeting_title'], $isModified, $replyingAttendee);
		$this->imipService->addBulletList($template, $vEvent, $data);

		// Only add response buttons to invitation requests: Fix Issue #11230
		if (strcasecmp($method, self::METHOD_REQUEST) === 0 && $this->imipService->getAttendeeRsvpOrReqForParticipant($attendee)) {

			/*
			** Only offer invitation accept/reject buttons, which link back to the
			** nextcloud server, to recipients who can access the nextcloud server via
			** their internet/intranet.  Issue #12156
			**
			** The app setting is stored in the appconfig database table.
			**
			** For nextcloud servers accessible to the public internet, the default
			** "invitation_link_recipients" value "yes" (all recipients) is appropriate.
			**
			** When the nextcloud server is restricted behind a firewall, accessible
			** only via an internal network or via vpn, you can set "dav.invitation_link_recipients"
			** to the email address or email domain, or comma separated list of addresses or domains,
			** of recipients who can access the server.
			**
			** To always deliver URLs, set invitation_link_recipients to "yes".
			** To suppress URLs entirely, set invitation_link_recipients to boolean "no".
			*/

			$recipientDomain = substr(strrchr($recipient, '@'), 1);
			$invitationLinkRecipients = explode(',', preg_replace('/\s+/', '', strtolower($this->config->getValueString('dav', 'invitation_link_recipients', 'yes'))));

			if (strcmp('yes', $invitationLinkRecipients[0]) === 0
				|| in_array(strtolower($recipient), $invitationLinkRecipients)
				|| in_array(strtolower($recipientDomain), $invitationLinkRecipients)) {
				$token = $this->imipService->createInvitationToken($iTipMessage, $vEvent, $lastOccurrence);
				$this->imipService->addResponseButtons($template, $token);
				$this->imipService->addMoreOptionsButton($template, $token);
			}
		}

		$template->addFooter();
		// convert iTip Message to string
		$itip_msg = $iTipMessage->message->serialize();

		$mailService = null;

		try {
			if ($this->config->getValueBool('core', 'mail_providers_enabled', true)) {
				// retrieve user object
				$user = $this->userSession->getUser();
				if ($user !== null) {
					// retrieve appropriate service with the same address as sender
					$mailService = $this->mailManager->findServiceByAddress($user->getUID(), $sender);
				}
			}

			// The display name in Nextcloud can use utf-8.
			// As the default charset for text/* is us-ascii, it's important to explicitly define it.
			// See https://www.rfc-editor.org/rfc/rfc6047.html#section-2.4.
			$contentType = 'text/calendar; method=' . $iTipMessage->method . '; charset="utf-8"';

			// evaluate if a mail service was found and has sending capabilities
			if ($mailService instanceof IMessageSend) {
				// construct mail message and set required parameters
				$message = $mailService->initiateMessage();
				$message->setFrom(
					(new Address($sender, $fromName))
				);
				$message->setTo(
					(new Address($recipient, $recipientName))
				);
				$message->setSubject($template->renderSubject());
				$message->setBodyPlain($template->renderText());
				$message->setBodyHtml($template->renderHtml());
				// Adding name=event.ics is a trick to make the invitation also appear
				// as a file attachment in mail clients like Thunderbird or Evolution.
				$message->setAttachments((new Attachment(
					$itip_msg,
					null,
					$contentType . '; name=event.ics',
					true
				)));
				// send message
				$mailService->sendMessage($message);
			} else {
				// construct symfony mailer message and set required parameters
				$message = $this->mailer->createMessage();
				$message->setFrom([$fromEMail => $fromName]);
				$message->setTo(
					(($recipientName !== null) ? [$recipient => $recipientName] : [$recipient])
				);
				$message->setReplyTo(
					(($senderName !== null) ? [$sender => $senderName] : [$sender])
				);
				$message->useTemplate($template);
				// Using a different content type because Symfony Mailer/Mime will append the name to
				// the content type header and attachInline does not allow null.
				$message->attachInline(
					$itip_msg,
					'event.ics',
					$contentType,
				);
				$failed = $this->mailer->send($message);
			}

			$iTipMessage->scheduleStatus = '1.1; Scheduling message is sent via iMip';
			if (!empty($failed)) {
				$this->logger->error('Unable to deliver message to {failed}', ['app' => 'dav', 'failed' => implode(', ', $failed)]);
				$iTipMessage->scheduleStatus = '5.0; EMail delivery failed';
			}
		} catch (\Exception $ex) {
			$this->logger->error($ex->getMessage(), ['app' => 'dav', 'exception' => $ex]);
			$iTipMessage->scheduleStatus = '5.0; EMail delivery failed';
		}
	}

	/**
	 * @return ?VCalendar
	 */
	public function getVCalendar(): ?VCalendar {
		return $this->vCalendar;
	}

	/**
	 * @param ?VCalendar $vCalendar
	 */
	public function setVCalendar(?VCalendar $vCalendar): void {
		$this->vCalendar = $vCalendar;
	}

}
