1 files changed, 597 insertions, 0 deletions

diff --git a/apps/dav/lib/CalDAV/Schedule/IMipService.php b/apps/dav/lib/CalDAV/Schedule/IMipService.php
new file mode 100644
index 00000000000..88f8bb8f54e
--- /dev/null
+++ b/apps/dav/lib/CalDAV/Schedule/IMipService.php
@@ -0,0 +1,597 @@
+<?php
+declare(strict_types=1);
+/*
+ * DAV App
+ *
+ * @copyright 2022 Anna Larch <anna.larch@gmx.net>
+ *
+ * @author Anna Larch <anna.larch@gmx.net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or any later version.
+ *
+ * This library 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 library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace OCA\DAV\CalDAV\Schedule;
+
+use OC\URLGenerator;
+use OCP\IConfig;
+use OCP\IDBConnection;
+use OCP\IL10N;
+use OCP\L10N\IFactory as L10NFactory;
+use OCP\Mail\IEMailTemplate;
+use OCP\Security\ISecureRandom;
+use Sabre\VObject\Component\VCalendar;
+use Sabre\VObject\Component\VEvent;
+use Sabre\VObject\DateTimeParser;
+use Sabre\VObject\ITip\Message;
+use Sabre\VObject\Parameter;
+use Sabre\VObject\Property;
+use Sabre\VObject\Recur\EventIterator;
+
+class IMipService {
+
+	private URLGenerator $urlGenerator;
+	private IConfig $config;
+	private IDBConnection $db;
+	private ISecureRandom $random;
+	private L10NFactory $l10nFactory;
+	private IL10N $l10n;
+
+	/** @var string[] */
+	private const STRING_DIFF = [
+		'meeting_title' => 'SUMMARY',
+		'meeting_description' => 'DESCRIPTION',
+		'meeting_url' => 'URL',
+		'meeting_location' => 'LOCATION'
+	];
+
+	public function __construct(URLGenerator $urlGenerator,
+								IConfig $config,
+								IDBConnection $db,
+								ISecureRandom $random,
+								L10NFactory $l10nFactory) {
+		$this->urlGenerator = $urlGenerator;
+		$this->config = $config;
+		$this->db = $db;
+		$this->random = $random;
+		$this->l10nFactory = $l10nFactory;
+		$default = $this->l10nFactory->findGenericLanguage();
+		$this->l10n = $this->l10nFactory->get('dav', $default);
+	}
+
+	/**
+	 * @param string $senderName
+	 * @param $default
+	 * @return string
+	 */
+	public function getFrom(string $senderName, $default): string {
+		return $this->l10n->t('%1$s via %2$s', [$senderName, $default]);
+	}
+
+	public static function readPropertyWithDefault(VEvent $vevent, string $property, string $default) {
+		if (isset($vevent->$property)) {
+			$value = $vevent->$property->getValue();
+			if (!empty($value)) {
+				return $value;
+			}
+		}
+		return $default;
+	}
+
+	private function generateDiffString(VEvent $vevent, VEvent $oldVEvent, string $property, string $default): ?string {
+		$strikethrough = "<span style='text-decoration: line-through'>%s</span><br />%s";
+		if (!isset($vevent->$property)) {
+			return $default;
+		}
+		$newstring = $vevent->$property->getValue();
+		if(isset($oldVEvent->$property)) {
+			$oldstring = $oldVEvent->$property->getValue();
+			return sprintf($strikethrough, $oldstring, $newstring);
+		}
+		return $newstring;
+	}
+
+	/**
+	 * @param VEvent $vEvent
+	 * @param VEvent|null $oldVEvent
+	 * @return array
+	 */
+	public function buildBodyData(VEvent $vEvent, ?VEvent $oldVEvent): array {
+		$defaultVal = '';
+		$data = [];
+		$data['meeting_when'] = $this->generateWhenString($vEvent);
+
+		foreach(self::STRING_DIFF as $key => $property) {
+			$data[$key] = self::readPropertyWithDefault($vEvent, $property, $defaultVal);
+		}
+
+		$data['meeting_url_html'] = self::readPropertyWithDefault($vEvent, 'URL', $defaultVal);
+
+		if(!empty($oldVEvent)) {
+			$oldMeetingWhen = $this->generateWhenString($oldVEvent);
+			$data['meeting_title_html']	= $this->generateDiffString($vEvent, $oldVEvent, 'SUMMARY', $data['meeting_title']);
+			$data['meeting_description_html'] = $this->generateDiffString($vEvent, $oldVEvent, 'DESCRIPTION', $data['meeting_description']);
+			$data['meeting_location_html'] = $this->generateDiffString($vEvent, $oldVEvent, 'LOCATION', $data['meeting_location']);
+
+			$oldUrl = self::readPropertyWithDefault($oldVEvent, 'URL', $defaultVal);
+			$data['meeting_url_html'] = !empty($oldUrl) ? sprintf('<a href="%1$s">%1$s</a>', $oldUrl) : $data['meeting_url'];
+
+			$data['meeting_when_html'] =
+				($oldMeetingWhen !== $data['meeting_when'] && $oldMeetingWhen !== null)
+					? sprintf("<span style='text-decoration: line-through'>%s</span><br />%s", $oldMeetingWhen, $data['meeting_when'])
+					: $data['meeting_when'];
+		}
+		return $data;
+	}
+
+	/**
+	 * @param IL10N $this->l10n
+	 * @param VEvent $vevent
+	 * @return false|int|string
+	 */
+	public function generateWhenString(VEvent $vevent) {
+		/** @var Property\ICalendar\DateTime $dtstart */
+		$dtstart = $vevent->DTSTART;
+		if (isset($vevent->DTEND)) {
+			/** @var Property\ICalendar\DateTime $dtend */
+			$dtend = $vevent->DTEND;
+		} elseif (isset($vevent->DURATION)) {
+			$isFloating = $dtstart->isFloating();
+			$dtend = clone $dtstart;
+			$endDateTime = $dtend->getDateTime();
+			$endDateTime = $endDateTime->add(DateTimeParser::parse($vevent->DURATION->getValue()));
+			$dtend->setDateTime($endDateTime, $isFloating);
+		} elseif (!$dtstart->hasTime()) {
+			$isFloating = $dtstart->isFloating();
+			$dtend = clone $dtstart;
+			$endDateTime = $dtend->getDateTime();
+			$endDateTime = $endDateTime->modify('+1 day');
+			$dtend->setDateTime($endDateTime, $isFloating);
+		} else {
+			$dtend = clone $dtstart;
+		}
+
+		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtstart */
+		/** @var \DateTimeImmutable $dtstartDt */
+		$dtstartDt = $dtstart->getDateTime();
+
+		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtend */
+		/** @var \DateTimeImmutable $dtendDt */
+		$dtendDt = $dtend->getDateTime();
+
+		$diff = $dtstartDt->diff($dtendDt);
+
+		$dtstartDt = new \DateTime($dtstartDt->format(\DateTimeInterface::ATOM));
+		$dtendDt = new \DateTime($dtendDt->format(\DateTimeInterface::ATOM));
+
+		if ($dtstart instanceof Property\ICalendar\Date) {
+			// One day event
+			if ($diff->days === 1) {
+				return $this->l10n->l('date', $dtstartDt, ['width' => 'medium']);
+			}
+
+			// DTEND is exclusive, so if the ics data says 2020-01-01 to 2020-01-05,
+			// the email should show 2020-01-01 to 2020-01-04.
+			$dtendDt->modify('-1 day');
+
+			//event that spans over multiple days
+			$localeStart = $this->l10n->l('date', $dtstartDt, ['width' => 'medium']);
+			$localeEnd = $this->l10n->l('date', $dtendDt, ['width' => 'medium']);
+
+			return $localeStart . ' - ' . $localeEnd;
+		}
+
+		/** @var Property\ICalendar\DateTime $dtstart */
+		/** @var Property\ICalendar\DateTime $dtend */
+		$isFloating = $dtstart->isFloating();
+		$startTimezone = $endTimezone = null;
+		if (!$isFloating) {
+			$prop = $dtstart->offsetGet('TZID');
+			if ($prop instanceof Parameter) {
+				$startTimezone = $prop->getValue();
+			}
+
+			$prop = $dtend->offsetGet('TZID');
+			if ($prop instanceof Parameter) {
+				$endTimezone = $prop->getValue();
+			}
+		}
+
+		$localeStart = $this->l10n->l('weekdayName', $dtstartDt, ['width' => 'abbreviated']) . ', ' .
+			$this->l10n->l('datetime', $dtstartDt, ['width' => 'medium|short']);
+
+		// always show full date with timezone if timezones are different
+		if ($startTimezone !== $endTimezone) {
+			$localeEnd = $this->l10n->l('datetime', $dtendDt, ['width' => 'medium|short']);
+
+			return $localeStart . ' (' . $startTimezone . ') - ' .
+				$localeEnd . ' (' . $endTimezone . ')';
+		}
+
+		// show only end time if date is the same
+		if ($dtstartDt->format('Y-m-d') === $dtendDt->format('Y-m-d')) {
+			$localeEnd = $this->l10n->l('time', $dtendDt, ['width' => 'short']);
+		} else {
+			$localeEnd = $this->l10n->l('weekdayName', $dtendDt, ['width' => 'abbreviated']) . ', ' .
+				$this->l10n->l('datetime', $dtendDt, ['width' => 'medium|short']);
+		}
+
+		return $localeStart . ' - ' . $localeEnd . ' (' . $startTimezone . ')';
+	}
+
+	/**
+	 * @param VEvent $vEvent
+	 * @return array
+	 */
+	public function buildCancelledBodyData(VEvent $vEvent): array {
+		$defaultVal = '';
+		$strikethrough = "<span style='text-decoration: line-through'>%s</span>";
+
+		$newMeetingWhen = $this->generateWhenString($vEvent);
+		$newSummary = isset($vEvent->SUMMARY) && (string)$vEvent->SUMMARY !== '' ? (string)$vEvent->SUMMARY : $this->l10n->t('Untitled event');;
+		$newDescription = isset($vEvent->DESCRIPTION) && (string)$vEvent->DESCRIPTION !== '' ? (string)$vEvent->DESCRIPTION : $defaultVal;
+		$newUrl = isset($vEvent->URL) && (string)$vEvent->URL !== '' ? sprintf('<a href="%1$s">%1$s</a>', $vEvent->URL) : $defaultVal;
+		$newLocation = isset($vEvent->LOCATION) && (string)$vEvent->LOCATION !== '' ? (string)$vEvent->LOCATION : $defaultVal;
+
+		$data = [];
+		$data['meeting_when_html'] = $newMeetingWhen === '' ?: sprintf($strikethrough, $newMeetingWhen);
+		$data['meeting_when'] = $newMeetingWhen;
+		$data['meeting_title_html'] = sprintf($strikethrough, $newSummary);
+		$data['meeting_title'] = $newSummary !== '' ? $newSummary: $this->l10n->t('Untitled event');
+		$data['meeting_description_html'] = $newDescription !== '' ? sprintf($strikethrough, $newDescription) : '';
+		$data['meeting_description'] = $newDescription;
+		$data['meeting_url_html'] = $newUrl !== '' ? sprintf($strikethrough, $newUrl) : '';
+		$data['meeting_url'] = isset($vEvent->URL) ? (string)$vEvent->URL : '';
+		$data['meeting_location_html'] = $newLocation !== '' ? sprintf($strikethrough, $newLocation) : '';
+		$data['meeting_location'] = $newLocation;
+		return $data;
+	}
+
+	/**
+	 * Check if event took place in the past
+	 *
+	 * @param VCalendar $vObject
+	 * @return int
+	 */
+	public function getLastOccurrence(VCalendar $vObject) {
+		/** @var VEvent $component */
+		$component = $vObject->VEVENT;
+
+		if (isset($component->RRULE)) {
+			$it = new EventIterator($vObject, (string)$component->UID);
+			$maxDate = new \DateTime(IMipPlugin::MAX_DATE);
+			if ($it->isInfinite()) {
+				return $maxDate->getTimestamp();
+			}
+
+			$end = $it->getDtEnd();
+			while ($it->valid() && $end < $maxDate) {
+				$end = $it->getDtEnd();
+				$it->next();
+			}
+			return $end->getTimestamp();
+		}
+
+		/** @var Property\ICalendar\DateTime $dtStart */
+		$dtStart = $component->DTSTART;
+
+		if (isset($component->DTEND)) {
+			/** @var Property\ICalendar\DateTime $dtEnd */
+			$dtEnd = $component->DTEND;
+			return $dtEnd->getDateTime()->getTimeStamp();
+		}
+
+		if(isset($component->DURATION)) {
+			/** @var \DateTime $endDate */
+			$endDate = clone $dtStart->getDateTime();
+			// $component->DTEND->getDateTime() returns DateTimeImmutable
+			$endDate = $endDate->add(DateTimeParser::parse($component->DURATION->getValue()));
+			return $endDate->getTimestamp();
+		}
+
+		if(!$dtStart->hasTime()) {
+			/** @var \DateTime $endDate */
+			// $component->DTSTART->getDateTime() returns DateTimeImmutable
+			$endDate = clone $dtStart->getDateTime();
+			$endDate = $endDate->modify('+1 day');
+			return $endDate->getTimestamp();
+		}
+
+		// No computation of end time possible - return start date
+		return $dtStart->getDateTime()->getTimeStamp();
+	}
+
+	/**
+	 * @param Property|null $attendee
+	 */
+	public function setL10n(?Property $attendee = null) {
+		if($attendee === null) {
+			return;
+		}
+
+		$lang = $attendee->offsetGet('LANGUAGE');
+		if ($lang instanceof Parameter) {
+			$lang = $lang->getValue();
+			$this->l10n = $this->l10nFactory->get('dav', $lang);
+		}
+	}
+
+	/**
+	 * @param Property|null $attendee
+	 * @return bool
+	 */
+	public function getAttendeeRsvpOrReqForParticipant(?Property $attendee = null) {
+		if($attendee === null) {
+			return false;
+		}
+
+		$rsvp = $attendee->offsetGet('RSVP');
+		if (($rsvp instanceof Parameter) && (strcasecmp($rsvp->getValue(), 'TRUE') === 0)) {
+			return true;
+		}
+		$role = $attendee->offsetGet('ROLE');
+		// @see https://datatracker.ietf.org/doc/html/rfc5545#section-3.2.16
+		// Attendees without a role are assumed required and should receive an invitation link even if they have no RSVP set
+		if ($role === null
+			|| (($role instanceof Parameter) && (strcasecmp($role->getValue(), 'REQ-PARTICIPANT') === 0))
+			|| (($role instanceof Parameter) && (strcasecmp($role->getValue(), 'OPT-PARTICIPANT') === 0))
+		) {
+			return true;
+		}
+
+		// RFC 5545 3.2.17: default RSVP is false
+		return false;
+	}
+
+	/**
+	 * @param IEMailTemplate $template
+	 * @param string $method
+	 * @param string $sender
+	 * @param string $summary
+	 * @param string|null $partstat
+	 */
+	public function addSubjectAndHeading(IEMailTemplate $template,
+		string $method, string $sender, string $summary): void {
+		if ($method === IMipPlugin::METHOD_CANCEL) {
+			// TRANSLATORS Subject for email, when an invitation is cancelled. Ex: "Cancelled: {{Event Name}}"
+			$template->setSubject($this->l10n->t('Cancelled: %1$s', [$summary]));
+			$template->addHeading($this->l10n->t('"%1$s" has been canceled', [$summary]));
+		} elseif ($method === IMipPlugin::METHOD_REPLY) {
+			// TRANSLATORS Subject for email, when an invitation is replied to. Ex: "Re: {{Event Name}}"
+			$template->setSubject($this->l10n->t('Re: %1$s', [$summary]));
+			$template->addHeading($this->l10n->t('%1$s has responded your invitation', [$sender]));
+		} else {
+			// TRANSLATORS Subject for email, when an invitation is sent. Ex: "Invitation: {{Event Name}}"
+			$template->setSubject($this->l10n->t('Invitation: %1$s', [$summary]));
+			$template->addHeading($this->l10n->t('%1$s would like to invite you to "%2$s"', [$sender, $summary]));
+		}
+	}
+
+	/**
+	 * @param string $path
+	 * @return string
+	 */
+	public function getAbsoluteImagePath($path): string {
+		return $this->urlGenerator->getAbsoluteURL(
+			$this->urlGenerator->imagePath('core', $path)
+		);
+	}
+
+	/**
+	 * addAttendees: add organizer and attendee names/emails to iMip mail.
+	 *
+	 * Enable with DAV setting: invitation_list_attendees (default: no)
+	 *
+	 * The default is 'no', which matches old behavior, and is privacy preserving.
+	 *
+	 * To enable including attendees in invitation emails:
+	 *   % php occ config:app:set dav invitation_list_attendees --value yes
+	 *
+	 * @param IEMailTemplate $template
+	 * @param IL10N $this->l10n
+	 * @param VEvent $vevent
+	 * @author brad2014 on github.com
+	 */
+	public function addAttendees(IEMailTemplate $template, VEvent $vevent) {
+		if ($this->config->getAppValue('dav', 'invitation_list_attendees', 'no') === 'no') {
+			return;
+		}
+
+		if (isset($vevent->ORGANIZER)) {
+			/** @var Property | Property\ICalendar\CalAddress $organizer */
+			$organizer = $vevent->ORGANIZER;
+			$organizerEmail = substr($organizer->getNormalizedValue(), 7);
+			/** @var string|null $organizerName */
+			$organizerName = isset($organizer->CN) ? $organizer->CN->getValue() : null;
+			$organizerHTML = sprintf('<a href="%s">%s</a>',
+				htmlspecialchars($organizer->getNormalizedValue()),
+				htmlspecialchars($organizerName ?: $organizerEmail));
+			$organizerText = sprintf('%s <%s>', $organizerName, $organizerEmail);
+			if(isset($organizer['PARTSTAT']) ) {
+				/** @var Parameter $partstat */
+				$partstat = $organizer['PARTSTAT'];
+				if(strcasecmp($partstat->getValue(), 'ACCEPTED') === 0) {
+					$organizerHTML .= ' ✔︎';
+					$organizerText .= ' ✔︎';
+				}
+			}
+			$template->addBodyListItem($organizerHTML, $this->l10n->t('Organizer:'),
+				$this->getAbsoluteImagePath('caldav/organizer.png'),
+				$organizerText, '', IMipPlugin::IMIP_INDENT);
+		}
+
+		$attendees = $vevent->select('ATTENDEE');
+		if (count($attendees) === 0) {
+			return;
+		}
+
+		$attendeesHTML = [];
+		$attendeesText = [];
+		foreach ($attendees as $attendee) {
+			$attendeeEmail = substr($attendee->getNormalizedValue(), 7);
+			$attendeeName = isset($attendee['CN']) ? $attendee['CN']->getValue() : null;
+			$attendeeHTML = sprintf('<a href="%s">%s</a>',
+				htmlspecialchars($attendee->getNormalizedValue()),
+				htmlspecialchars($attendeeName ?: $attendeeEmail));
+			$attendeeText = sprintf('%s <%s>', $attendeeName, $attendeeEmail);
+			if (isset($attendee['PARTSTAT'])) {
+				/** @var Parameter $partstat */
+				$partstat = $attendee['PARTSTAT'];
+				if (strcasecmp($partstat->getValue(), 'ACCEPTED') === 0) {
+					$attendeeHTML .= ' ✔︎';
+					$attendeeText .= ' ✔︎';
+				}
+			}
+			$attendeesHTML[] = $attendeeHTML;
+			$attendeesText[] = $attendeeText;
+		}
+
+		$template->addBodyListItem(implode('<br/>', $attendeesHTML), $this->l10n->t('Attendees:'),
+			$this->getAbsoluteImagePath('caldav/attendees.png'),
+			implode("\n", $attendeesText), '', IMipPlugin::IMIP_INDENT);
+	}
+
+	/**
+	 * @param IEMailTemplate $template
+	 * @param VEVENT $vevent
+	 * @param $data
+	 */
+	public function addBulletList(IEMailTemplate $template, VEvent $vevent, $data) {
+		$template->addBodyListItem(
+			$data['meeting_title'], $this->l10n->t('Title:'),
+			$this->getAbsoluteImagePath('caldav/title.png'), $data['meeting_title'], '', IMipPlugin::IMIP_INDENT);
+		if ($data['meeting_when'] !== '') {
+			$template->addBodyListItem($data['meeting_when_html'] ?? $data['meeting_when'], $this->l10n->t('Time:'),
+				$this->getAbsoluteImagePath('caldav/time.png'), $data['meeting_when'], '', IMipPlugin::IMIP_INDENT);
+		}
+		if ($data['meeting_location'] !== '') {
+			$template->addBodyListItem($data['meeting_location_html'] ?? $data['meeting_location'], $this->l10n->t('Location:'),
+				$this->getAbsoluteImagePath('caldav/location.png'), $data['meeting_location'], '', IMipPlugin::IMIP_INDENT);
+		}
+		if ($data['meeting_url'] !== '') {
+			$template->addBodyListItem($data['meeting_url_html'] ?? $data['meeting_url'], $this->l10n->t('Link:'),
+				$this->getAbsoluteImagePath('caldav/link.png'), $data['meeting_url'], '', IMipPlugin::IMIP_INDENT);
+		}
+
+		$this->addAttendees($template, $vevent);
+
+		/* Put description last, like an email body, since it can be arbitrarily long */
+		if ($data['meeting_description']) {
+			$template->addBodyListItem($data['meeting_description_html'] ?? $data['meeting_description'], $this->l10n->t('Description:'),
+				$this->getAbsoluteImagePath('caldav/description.png'), $data['meeting_description'], '', IMipPlugin::IMIP_INDENT);
+		}
+	}
+
+	/**
+	 * @param Message $iTipMessage
+	 * @return null|Property
+	 */
+	public function getCurrentAttendee(Message $iTipMessage): ?Property {
+		/** @var VEvent $vevent */
+		$vevent = $iTipMessage->message->VEVENT;
+		$attendees = $vevent->select('ATTENDEE');
+		foreach ($attendees as $attendee) {
+			/** @var Property $attendee */
+			if (strcasecmp($attendee->getValue(), $iTipMessage->recipient) === 0) {
+				return $attendee;
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * @param Message $iTipMessage
+	 * @param VEvent $vevent
+	 * @param int $lastOccurrence
+	 * @return string
+	 */
+	public function createInvitationToken(Message $iTipMessage, VEvent $vevent, int $lastOccurrence): string {
+		$token = $this->random->generate(60, ISecureRandom::CHAR_ALPHANUMERIC);
+
+		$attendee = $iTipMessage->recipient;
+		$organizer = $iTipMessage->sender;
+		$sequence = $iTipMessage->sequence;
+		$recurrenceId = isset($vevent->{'RECURRENCE-ID'}) ?
+			$vevent->{'RECURRENCE-ID'}->serialize() : null;
+		$uid = $vevent->{'UID'};
+
+		$query = $this->db->getQueryBuilder();
+		$query->insert('calendar_invitations')
+			->values([
+				'token' => $query->createNamedParameter($token),
+				'attendee' => $query->createNamedParameter($attendee),
+				'organizer' => $query->createNamedParameter($organizer),
+				'sequence' => $query->createNamedParameter($sequence),
+				'recurrenceid' => $query->createNamedParameter($recurrenceId),
+				'expiration' => $query->createNamedParameter($lastOccurrence),
+				'uid' => $query->createNamedParameter($uid)
+			])
+			->execute();
+
+		return $token;
+	}
+
+	/**
+	 * Create a valid VCalendar object out of the details of
+	 * a VEvent and its associated iTip Message
+	 *
+	 * We do this to filter out all unchanged VEvents
+	 * This is especially important in iTip Messages with recurrences
+	 * and recurrence exceptions
+	 *
+	 * @param Message $iTipMessage
+	 * @param VEvent $vEvent
+	 * @return VCalendar
+	 */
+	public function generateVCalendar(Message $iTipMessage, VEvent $vEvent): VCalendar {
+		$vCalendar = new VCalendar();
+		$vCalendar->add('METHOD', $iTipMessage->method);
+		foreach ($iTipMessage->message->getComponents() as $component) {
+			if ($component instanceof VEvent) {
+				continue;
+			}
+			$vCalendar->add(clone $component);
+		}
+		$vCalendar->add($vEvent);
+		return $vCalendar;
+	}
+
+	/**
+	 * @param IEMailTemplate $template
+	 * @param $token
+	 */
+	public function addResponseButtons(IEMailTemplate $template, $token) {
+		$template->addBodyButtonGroup(
+			$this->l10n->t('Accept'),
+			$this->urlGenerator->linkToRouteAbsolute('dav.invitation_response.accept', [
+				'token' => $token,
+			]),
+			$this->l10n->t('Decline'),
+			$this->urlGenerator->linkToRouteAbsolute('dav.invitation_response.decline', [
+				'token' => $token,
+			])
+		);
+	}
+
+	public function addMoreOptionsButton(IEMailTemplate $template, $token) {
+		$moreOptionsURL = $this->urlGenerator->linkToRouteAbsolute('dav.invitation_response.options', [
+			'token' => $token,
+		]);
+		$html = vsprintf('<small><a href="%s">%s</a></small>', [
+			$moreOptionsURL, $this->l10n->t('More options …')
+		]);
+		$text = $this->l10n->t('More options at %s', [$moreOptionsURL]);
+
+		$template->addBodyText($html, $text);
+	}
+}