nextcloud / server

apps/dav/lib/CalDAV/Schedule/Plugin.php

Indentation +699 added lines, -699 removed lines

@@ -42,260 +42,260 @@ 
 
 class Plugin extends \Sabre\CalDAV\Schedule\Plugin {
 
-	/** @var ITip\Message[] */
-	private $schedulingResponses = [];
-
-	/** @var string|null */
-	private $pathOfCalendarObjectChange = null;
-
-	public const CALENDAR_USER_TYPE = '{' . self::NS_CALDAV . '}calendar-user-type';
-	public const SCHEDULE_DEFAULT_CALENDAR_URL = '{' . Plugin::NS_CALDAV . '}schedule-default-calendar-URL';
-
-	/**
-	 * @param IConfig $config
-	 */
-	public function __construct(
-		private IConfig $config,
-		private LoggerInterface $logger,
-		private DefaultCalendarValidator $defaultCalendarValidator,
-	) {
-	}
-
-	/**
-	 * Initializes the plugin
-	 *
-	 * @param Server $server
-	 * @return void
-	 */
-	public function initialize(Server $server) {
-		parent::initialize($server);
-		$server->on('propFind', [$this, 'propFindDefaultCalendarUrl'], 90);
-		$server->on('afterWriteContent', [$this, 'dispatchSchedulingResponses']);
-		$server->on('afterCreateFile', [$this, 'dispatchSchedulingResponses']);
-
-		// We allow mutating the default calendar URL through the CustomPropertiesBackend
-		// (oc_properties table)
-		$server->protectedProperties = array_filter(
-			$server->protectedProperties,
-			static fn (string $property) => $property !== self::SCHEDULE_DEFAULT_CALENDAR_URL,
-		);
-	}
-
-	/**
-	 * Returns an instance of the iTip\Broker.
-	 */
-	protected function createITipBroker(): TipBroker {
-		return new TipBroker();
-	}
-
-	/**
-	 * Allow manual setting of the object change URL
-	 * to support public write
-	 *
-	 * @param string $path
-	 */
-	public function setPathOfCalendarObjectChange(string $path): void {
-		$this->pathOfCalendarObjectChange = $path;
-	}
-
-	/**
-	 * This method handler is invoked during fetching of properties.
-	 *
-	 * We use this event to add calendar-auto-schedule-specific properties.
-	 *
-	 * @param PropFind $propFind
-	 * @param INode $node
-	 * @return void
-	 */
-	public function propFind(PropFind $propFind, INode $node) {
-		if ($node instanceof IPrincipal) {
-			// overwrite Sabre/Dav's implementation
-			$propFind->handle(self::CALENDAR_USER_TYPE, function () use ($node) {
-				if ($node instanceof IProperties) {
-					$props = $node->getProperties([self::CALENDAR_USER_TYPE]);
-
-					if (isset($props[self::CALENDAR_USER_TYPE])) {
-						return $props[self::CALENDAR_USER_TYPE];
-					}
-				}
-
-				return 'INDIVIDUAL';
-			});
-		}
-
-		parent::propFind($propFind, $node);
-	}
-
-	/**
-	 * Returns a list of addresses that are associated with a principal.
-	 *
-	 * @param string $principal
-	 * @return array
-	 */
-	protected function getAddressesForPrincipal($principal) {
-		$result = parent::getAddressesForPrincipal($principal);
-
-		if ($result === null) {
-			$result = [];
-		}
-
-		// iterate through items and html decode values
-		foreach ($result as $key => $value) {
-			$result[$key] = urldecode($value);
-		}
-
-		return $result;
-	}
-
-	/**
-	 * @param RequestInterface $request
-	 * @param ResponseInterface $response
-	 * @param VCalendar $vCal
-	 * @param mixed $calendarPath
-	 * @param mixed $modified
-	 * @param mixed $isNew
-	 */
-	public function calendarObjectChange(RequestInterface $request, ResponseInterface $response, VCalendar $vCal, $calendarPath, &$modified, $isNew) {
-		// Save the first path we get as a calendar-object-change request
-		if (!$this->pathOfCalendarObjectChange) {
-			$this->pathOfCalendarObjectChange = $request->getPath();
-		}
-
-		try {
-
-			// Do not generate iTip and iMip messages if scheduling is disabled for this message
-			if ($request->getHeader('x-nc-scheduling') === 'false') {
-				return;
-			}
-
-			if (!$this->scheduleReply($this->server->httpRequest)) {
-				return;
-			}
-
-			/** @var Calendar $calendarNode */
-			$calendarNode = $this->server->tree->getNodeForPath($calendarPath);
-			// extract addresses for owner
-			$addresses = $this->getAddressesForPrincipal($calendarNode->getOwner());
-			// determine if request is from a sharee
-			if ($calendarNode->isShared()) {
-				// extract addresses for sharee and add to address collection
-				$addresses = array_merge(
-					$addresses,
-					$this->getAddressesForPrincipal($calendarNode->getPrincipalURI())
-				);
-			}
-			// determine if we are updating a calendar event
-			if (!$isNew) {
-				// retrieve current calendar event node
-				/** @var CalendarObject $currentNode */
-				$currentNode = $this->server->tree->getNodeForPath($request->getPath());
-				// convert calendar event string data to VCalendar object
-				/** @var \Sabre\VObject\Component\VCalendar $currentObject */
-				$currentObject = Reader::read($currentNode->get());
-			} else {
-				$currentObject = null;
-			}
-			// process request
-			$this->processICalendarChange($currentObject, $vCal, $addresses, [], $modified);
-
-			if ($currentObject) {
-				// Destroy circular references so PHP will GC the object.
-				$currentObject->destroy();
-			}
-
-		} catch (SameOrganizerForAllComponentsException $e) {
-			$this->handleSameOrganizerException($e, $vCal, $calendarPath);
-		}
-	}
-
-	/**
-	 * @inheritDoc
-	 */
-	public function beforeUnbind($path): void {
-		try {
-			parent::beforeUnbind($path);
-		} catch (SameOrganizerForAllComponentsException $e) {
-			$node = $this->server->tree->getNodeForPath($path);
-			if (!$node instanceof ICalendarObject || $node instanceof ISchedulingObject) {
-				throw $e;
-			}
-
-			/** @var VCalendar $vCal */
-			$vCal = Reader::read($node->get());
-			$this->handleSameOrganizerException($e, $vCal, $path);
-		}
-	}
-
-	/**
-	 * @inheritDoc
-	 */
-	public function scheduleLocalDelivery(ITip\Message $iTipMessage):void {
-		/** @var VEvent|null $vevent */
-		$vevent = $iTipMessage->message->VEVENT ?? null;
-
-		// Strip VALARMs from incoming VEVENT
-		if ($vevent && isset($vevent->VALARM)) {
-			$vevent->remove('VALARM');
-		}
-
-		parent::scheduleLocalDelivery($iTipMessage);
-		// We only care when the message was successfully delivered locally
-		// Log all possible codes returned from the parent method that mean something went wrong
-		// 3.7, 3.8, 5.0, 5.2
-		if ($iTipMessage->scheduleStatus !== '1.2;Message delivered locally') {
-			$this->logger->debug('Message not delivered locally with status: ' . $iTipMessage->scheduleStatus);
-			return;
-		}
-		// We only care about request. reply and cancel are properly handled
-		// by parent::scheduleLocalDelivery already
-		if (strcasecmp($iTipMessage->method, 'REQUEST') !== 0) {
-			return;
-		}
-
-		// If parent::scheduleLocalDelivery set scheduleStatus to 1.2,
-		// it means that it was successfully delivered locally.
-		// Meaning that the ACL plugin is loaded and that a principal
-		// exists for the given recipient id, no need to double check
-		/** @var \Sabre\DAVACL\Plugin $aclPlugin */
-		$aclPlugin = $this->server->getPlugin('acl');
-		$principalUri = $aclPlugin->getPrincipalByUri($iTipMessage->recipient);
-		$calendarUserType = $this->getCalendarUserTypeForPrincipal($principalUri);
-		if (strcasecmp($calendarUserType, 'ROOM') !== 0 && strcasecmp($calendarUserType, 'RESOURCE') !== 0) {
-			$this->logger->debug('Calendar user type is neither room nor resource, not processing further');
-			return;
-		}
-
-		$attendee = $this->getCurrentAttendee($iTipMessage);
-		if (!$attendee) {
-			$this->logger->debug('No attendee set for scheduling message');
-			return;
-		}
-
-		// We only respond when a response was actually requested
-		$rsvp = $this->getAttendeeRSVP($attendee);
-		if (!$rsvp) {
-			$this->logger->debug('No RSVP requested for attendee ' . $attendee->getValue());
-			return;
-		}
-
-		if (!$vevent) {
-			$this->logger->debug('No VEVENT set to process on scheduling message');
-			return;
-		}
-
-		// We don't support autoresponses for recurrencing events for now
-		if (isset($vevent->RRULE) || isset($vevent->RDATE)) {
-			$this->logger->debug('VEVENT is a recurring event, autoresponding not supported');
-			return;
-		}
-
-		$dtstart = $vevent->DTSTART;
-		$dtend = $this->getDTEndFromVEvent($vevent);
-		$uid = $vevent->UID->getValue();
-		$sequence = isset($vevent->SEQUENCE) ? $vevent->SEQUENCE->getValue() : 0;
-		$recurrenceId = isset($vevent->{'RECURRENCE-ID'}) ? $vevent->{'RECURRENCE-ID'}->serialize() : '';
-
-		$message = <<<EOF
+    /** @var ITip\Message[] */
+    private $schedulingResponses = [];
+
+    /** @var string|null */
+    private $pathOfCalendarObjectChange = null;
+
+    public const CALENDAR_USER_TYPE = '{' . self::NS_CALDAV . '}calendar-user-type';
+    public const SCHEDULE_DEFAULT_CALENDAR_URL = '{' . Plugin::NS_CALDAV . '}schedule-default-calendar-URL';
+
+    /**
+     * @param IConfig $config
+     */
+    public function __construct(
+        private IConfig $config,
+        private LoggerInterface $logger,
+        private DefaultCalendarValidator $defaultCalendarValidator,
+    ) {
+    }
+
+    /**
+     * Initializes the plugin
+     *
+     * @param Server $server
+     * @return void
+     */
+    public function initialize(Server $server) {
+        parent::initialize($server);
+        $server->on('propFind', [$this, 'propFindDefaultCalendarUrl'], 90);
+        $server->on('afterWriteContent', [$this, 'dispatchSchedulingResponses']);
+        $server->on('afterCreateFile', [$this, 'dispatchSchedulingResponses']);
+
+        // We allow mutating the default calendar URL through the CustomPropertiesBackend
+        // (oc_properties table)
+        $server->protectedProperties = array_filter(
+            $server->protectedProperties,
+            static fn (string $property) => $property !== self::SCHEDULE_DEFAULT_CALENDAR_URL,
+        );
+    }
+
+    /**
+     * Returns an instance of the iTip\Broker.
+     */
+    protected function createITipBroker(): TipBroker {
+        return new TipBroker();
+    }
+
+    /**
+     * Allow manual setting of the object change URL
+     * to support public write
+     *
+     * @param string $path
+     */
+    public function setPathOfCalendarObjectChange(string $path): void {
+        $this->pathOfCalendarObjectChange = $path;
+    }
+
+    /**
+     * This method handler is invoked during fetching of properties.
+     *
+     * We use this event to add calendar-auto-schedule-specific properties.
+     *
+     * @param PropFind $propFind
+     * @param INode $node
+     * @return void
+     */
+    public function propFind(PropFind $propFind, INode $node) {
+        if ($node instanceof IPrincipal) {
+            // overwrite Sabre/Dav's implementation
+            $propFind->handle(self::CALENDAR_USER_TYPE, function () use ($node) {
+                if ($node instanceof IProperties) {
+                    $props = $node->getProperties([self::CALENDAR_USER_TYPE]);
+
+                    if (isset($props[self::CALENDAR_USER_TYPE])) {
+                        return $props[self::CALENDAR_USER_TYPE];
+                    }
+                }
+
+                return 'INDIVIDUAL';
+            });
+        }
+
+        parent::propFind($propFind, $node);
+    }
+
+    /**
+     * Returns a list of addresses that are associated with a principal.
+     *
+     * @param string $principal
+     * @return array
+     */
+    protected function getAddressesForPrincipal($principal) {
+        $result = parent::getAddressesForPrincipal($principal);
+
+        if ($result === null) {
+            $result = [];
+        }
+
+        // iterate through items and html decode values
+        foreach ($result as $key => $value) {
+            $result[$key] = urldecode($value);
+        }
+
+        return $result;
+    }
+
+    /**
+     * @param RequestInterface $request
+     * @param ResponseInterface $response
+     * @param VCalendar $vCal
+     * @param mixed $calendarPath
+     * @param mixed $modified
+     * @param mixed $isNew
+     */
+    public function calendarObjectChange(RequestInterface $request, ResponseInterface $response, VCalendar $vCal, $calendarPath, &$modified, $isNew) {
+        // Save the first path we get as a calendar-object-change request
+        if (!$this->pathOfCalendarObjectChange) {
+            $this->pathOfCalendarObjectChange = $request->getPath();
+        }
+
+        try {
+
+            // Do not generate iTip and iMip messages if scheduling is disabled for this message
+            if ($request->getHeader('x-nc-scheduling') === 'false') {
+                return;
+            }
+
+            if (!$this->scheduleReply($this->server->httpRequest)) {
+                return;
+            }
+
+            /** @var Calendar $calendarNode */
+            $calendarNode = $this->server->tree->getNodeForPath($calendarPath);
+            // extract addresses for owner
+            $addresses = $this->getAddressesForPrincipal($calendarNode->getOwner());
+            // determine if request is from a sharee
+            if ($calendarNode->isShared()) {
+                // extract addresses for sharee and add to address collection
+                $addresses = array_merge(
+                    $addresses,
+                    $this->getAddressesForPrincipal($calendarNode->getPrincipalURI())
+                );
+            }
+            // determine if we are updating a calendar event
+            if (!$isNew) {
+                // retrieve current calendar event node
+                /** @var CalendarObject $currentNode */
+                $currentNode = $this->server->tree->getNodeForPath($request->getPath());
+                // convert calendar event string data to VCalendar object
+                /** @var \Sabre\VObject\Component\VCalendar $currentObject */
+                $currentObject = Reader::read($currentNode->get());
+            } else {
+                $currentObject = null;
+            }
+            // process request
+            $this->processICalendarChange($currentObject, $vCal, $addresses, [], $modified);
+
+            if ($currentObject) {
+                // Destroy circular references so PHP will GC the object.
+                $currentObject->destroy();
+            }
+
+        } catch (SameOrganizerForAllComponentsException $e) {
+            $this->handleSameOrganizerException($e, $vCal, $calendarPath);
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function beforeUnbind($path): void {
+        try {
+            parent::beforeUnbind($path);
+        } catch (SameOrganizerForAllComponentsException $e) {
+            $node = $this->server->tree->getNodeForPath($path);
+            if (!$node instanceof ICalendarObject || $node instanceof ISchedulingObject) {
+                throw $e;
+            }
+
+            /** @var VCalendar $vCal */
+            $vCal = Reader::read($node->get());
+            $this->handleSameOrganizerException($e, $vCal, $path);
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function scheduleLocalDelivery(ITip\Message $iTipMessage):void {
+        /** @var VEvent|null $vevent */
+        $vevent = $iTipMessage->message->VEVENT ?? null;
+
+        // Strip VALARMs from incoming VEVENT
+        if ($vevent && isset($vevent->VALARM)) {
+            $vevent->remove('VALARM');
+        }
+
+        parent::scheduleLocalDelivery($iTipMessage);
+        // We only care when the message was successfully delivered locally
+        // Log all possible codes returned from the parent method that mean something went wrong
+        // 3.7, 3.8, 5.0, 5.2
+        if ($iTipMessage->scheduleStatus !== '1.2;Message delivered locally') {
+            $this->logger->debug('Message not delivered locally with status: ' . $iTipMessage->scheduleStatus);
+            return;
+        }
+        // We only care about request. reply and cancel are properly handled
+        // by parent::scheduleLocalDelivery already
+        if (strcasecmp($iTipMessage->method, 'REQUEST') !== 0) {
+            return;
+        }
+
+        // If parent::scheduleLocalDelivery set scheduleStatus to 1.2,
+        // it means that it was successfully delivered locally.
+        // Meaning that the ACL plugin is loaded and that a principal
+        // exists for the given recipient id, no need to double check
+        /** @var \Sabre\DAVACL\Plugin $aclPlugin */
+        $aclPlugin = $this->server->getPlugin('acl');
+        $principalUri = $aclPlugin->getPrincipalByUri($iTipMessage->recipient);
+        $calendarUserType = $this->getCalendarUserTypeForPrincipal($principalUri);
+        if (strcasecmp($calendarUserType, 'ROOM') !== 0 && strcasecmp($calendarUserType, 'RESOURCE') !== 0) {
+            $this->logger->debug('Calendar user type is neither room nor resource, not processing further');
+            return;
+        }
+
+        $attendee = $this->getCurrentAttendee($iTipMessage);
+        if (!$attendee) {
+            $this->logger->debug('No attendee set for scheduling message');
+            return;
+        }
+
+        // We only respond when a response was actually requested
+        $rsvp = $this->getAttendeeRSVP($attendee);
+        if (!$rsvp) {
+            $this->logger->debug('No RSVP requested for attendee ' . $attendee->getValue());
+            return;
+        }
+
+        if (!$vevent) {
+            $this->logger->debug('No VEVENT set to process on scheduling message');
+            return;
+        }
+
+        // We don't support autoresponses for recurrencing events for now
+        if (isset($vevent->RRULE) || isset($vevent->RDATE)) {
+            $this->logger->debug('VEVENT is a recurring event, autoresponding not supported');
+            return;
+        }
+
+        $dtstart = $vevent->DTSTART;
+        $dtend = $this->getDTEndFromVEvent($vevent);
+        $uid = $vevent->UID->getValue();
+        $sequence = isset($vevent->SEQUENCE) ? $vevent->SEQUENCE->getValue() : 0;
+        $recurrenceId = isset($vevent->{'RECURRENCE-ID'}) ? $vevent->{'RECURRENCE-ID'}->serialize() : '';
+
+        $message = <<<EOF
 BEGIN:VCALENDAR
 PRODID:-//Nextcloud/Nextcloud CalDAV Server//EN
 METHOD:REPLY
@@ -310,449 +310,449 @@ 
 END:VCALENDAR
 EOF;
 
-		if ($this->isAvailableAtTime($attendee->getValue(), $dtstart->getDateTime(), $dtend->getDateTime(), $uid)) {
-			$partStat = 'ACCEPTED';
-		} else {
-			$partStat = 'DECLINED';
-		}
-
-		$vObject = Reader::read(vsprintf($message, [
-			$partStat,
-			$iTipMessage->recipient,
-			$iTipMessage->sender,
-			$uid,
-			$sequence,
-			$recurrenceId
-		]));
-
-		$responseITipMessage = new ITip\Message();
-		$responseITipMessage->uid = $uid;
-		$responseITipMessage->component = 'VEVENT';
-		$responseITipMessage->method = 'REPLY';
-		$responseITipMessage->sequence = $sequence;
-		$responseITipMessage->sender = $iTipMessage->recipient;
-		$responseITipMessage->recipient = $iTipMessage->sender;
-		$responseITipMessage->message = $vObject;
-
-		// We can't dispatch them now already, because the organizers calendar-object
-		// was not yet created. Hence Sabre/DAV won't find a calendar-object, when we
-		// send our reply.
-		$this->schedulingResponses[] = $responseITipMessage;
-	}
-
-	/**
-	 * @param string $uri
-	 */
-	public function dispatchSchedulingResponses(string $uri):void {
-		if ($uri !== $this->pathOfCalendarObjectChange) {
-			return;
-		}
-
-		foreach ($this->schedulingResponses as $schedulingResponse) {
-			$this->scheduleLocalDelivery($schedulingResponse);
-		}
-	}
-
-	/**
-	 * Always use the personal calendar as target for scheduled events
-	 *
-	 * @param PropFind $propFind
-	 * @param INode $node
-	 * @return void
-	 */
-	public function propFindDefaultCalendarUrl(PropFind $propFind, INode $node) {
-		if ($node instanceof IPrincipal) {
-			$propFind->handle(self::SCHEDULE_DEFAULT_CALENDAR_URL, function () use ($node) {
-				/** @var \OCA\DAV\CalDAV\Plugin $caldavPlugin */
-				$caldavPlugin = $this->server->getPlugin('caldav');
-				$principalUrl = $node->getPrincipalUrl();
-
-				$calendarHomePath = $caldavPlugin->getCalendarHomeForPrincipal($principalUrl);
-				if (!$calendarHomePath) {
-					return null;
-				}
-
-				$isResourceOrRoom = str_starts_with($principalUrl, 'principals/calendar-resources') ||
-					str_starts_with($principalUrl, 'principals/calendar-rooms');
-
-				if (str_starts_with($principalUrl, 'principals/users')) {
-					[, $userId] = split($principalUrl);
-					$uri = $this->config->getUserValue($userId, 'dav', 'defaultCalendar', CalDavBackend::PERSONAL_CALENDAR_URI);
-					$displayName = CalDavBackend::PERSONAL_CALENDAR_NAME;
-				} elseif ($isResourceOrRoom) {
-					$uri = CalDavBackend::RESOURCE_BOOKING_CALENDAR_URI;
-					$displayName = CalDavBackend::RESOURCE_BOOKING_CALENDAR_NAME;
-				} else {
-					// How did we end up here?
-					// TODO - throw exception or just ignore?
-					return null;
-				}
-
-				/** @var CalendarHome $calendarHome */
-				$calendarHome = $this->server->tree->getNodeForPath($calendarHomePath);
-				$currentCalendarDeleted = false;
-				if (!$calendarHome->childExists($uri) || $currentCalendarDeleted = $this->isCalendarDeleted($calendarHome, $uri)) {
-					// If the default calendar doesn't exist
-					if ($isResourceOrRoom) {
-						// Resources or rooms can't be in the trashbin, so we're fine
-						$this->createCalendar($calendarHome, $principalUrl, $uri, $displayName);
-					} else {
-						// And we're not handling scheduling on resource/room booking
-						$userCalendars = [];
-						/**
-						 * If the default calendar of the user isn't set and the
-						 * fallback doesn't match any of the user's calendar
-						 * try to find the first "personal" calendar we can write to
-						 * instead of creating a new one.
-						 * A appropriate personal calendar to receive invites:
-						 * - isn't a calendar subscription
-						 * - user can write to it (no virtual/3rd-party calendars)
-						 * - calendar isn't a share
-						 * - calendar supports VEVENTs
-						 */
-						foreach ($calendarHome->getChildren() as $node) {
-							if (!($node instanceof Calendar)) {
-								continue;
-							}
-
-							try {
-								$this->defaultCalendarValidator->validateScheduleDefaultCalendar($node);
-							} catch (DavException $e) {
-								continue;
-							}
-
-							$userCalendars[] = $node;
-						}
-
-						if (count($userCalendars) > 0) {
-							// Calendar backend returns calendar by calendarorder property
-							$uri = $userCalendars[0]->getName();
-						} else {
-							// Otherwise if we have really nothing, create a new calendar
-							if ($currentCalendarDeleted) {
-								// If the calendar exists but is in the trash bin, we try to rename its uri
-								// so that we can create the new one and still restore the previous one
-								// otherwise we just purge the calendar by removing it before recreating it
-								$calendar = $this->getCalendar($calendarHome, $uri);
-								if ($calendar instanceof Calendar) {
-									$backend = $calendarHome->getCalDAVBackend();
-									if ($backend instanceof CalDavBackend) {
-										// If the CalDAV backend supports moving calendars
-										$this->moveCalendar($backend, $principalUrl, $uri, $uri . '-back-' . time());
-									} else {
-										// Otherwise just purge the calendar
-										$calendar->disableTrashbin();
-										$calendar->delete();
-									}
-								}
-							}
-							$this->createCalendar($calendarHome, $principalUrl, $uri, $displayName);
-						}
-					}
-				}
-
-				$result = $this->server->getPropertiesForPath($calendarHomePath . '/' . $uri, [], 1);
-				if (empty($result)) {
-					return null;
-				}
-
-				return new LocalHref($result[0]['href']);
-			});
-		}
-	}
-
-	/**
-	 * Returns a list of addresses that are associated with a principal.
-	 *
-	 * @param string $principal
-	 * @return string|null
-	 */
-	protected function getCalendarUserTypeForPrincipal($principal):?string {
-		$calendarUserType = '{' . self::NS_CALDAV . '}calendar-user-type';
-		$properties = $this->server->getProperties(
-			$principal,
-			[$calendarUserType]
-		);
-
-		// If we can't find this information, we'll stop processing
-		if (!isset($properties[$calendarUserType])) {
-			return null;
-		}
-
-		return $properties[$calendarUserType];
-	}
-
-	/**
-	 * @param ITip\Message $iTipMessage
-	 * @return null|Property
-	 */
-	private function getCurrentAttendee(ITip\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 Property|null $attendee
-	 * @return bool
-	 */
-	private function getAttendeeRSVP(?Property $attendee = null):bool {
-		if ($attendee !== null) {
-			$rsvp = $attendee->offsetGet('RSVP');
-			if (($rsvp instanceof Parameter) && (strcasecmp($rsvp->getValue(), 'TRUE') === 0)) {
-				return true;
-			}
-		}
-		// RFC 5545 3.2.17: default RSVP is false
-		return false;
-	}
-
-	/**
-	 * @param VEvent $vevent
-	 * @return Property\ICalendar\DateTime
-	 */
-	private function getDTEndFromVEvent(VEvent $vevent):Property\ICalendar\DateTime {
-		if (isset($vevent->DTEND)) {
-			return $vevent->DTEND;
-		}
-
-		if (isset($vevent->DURATION)) {
-			$isFloating = $vevent->DTSTART->isFloating();
-			/** @var Property\ICalendar\DateTime $end */
-			$end = clone $vevent->DTSTART;
-			$endDateTime = $end->getDateTime();
-			$endDateTime = $endDateTime->add(DateTimeParser::parse($vevent->DURATION->getValue()));
-			$end->setDateTime($endDateTime, $isFloating);
-			return $end;
-		}
-
-		if (!$vevent->DTSTART->hasTime()) {
-			$isFloating = $vevent->DTSTART->isFloating();
-			/** @var Property\ICalendar\DateTime $end */
-			$end = clone $vevent->DTSTART;
-			$endDateTime = $end->getDateTime();
-			$endDateTime = $endDateTime->modify('+1 day');
-			$end->setDateTime($endDateTime, $isFloating);
-			return $end;
-		}
-
-		return clone $vevent->DTSTART;
-	}
-
-	/**
-	 * @param string $email
-	 * @param \DateTimeInterface $start
-	 * @param \DateTimeInterface $end
-	 * @param string $ignoreUID
-	 * @return bool
-	 */
-	private function isAvailableAtTime(string $email, \DateTimeInterface $start, \DateTimeInterface $end, string $ignoreUID):bool {
-		// This method is heavily inspired by Sabre\CalDAV\Schedule\Plugin::scheduleLocalDelivery
-		// and Sabre\CalDAV\Schedule\Plugin::getFreeBusyForEmail
-
-		$aclPlugin = $this->server->getPlugin('acl');
-		$this->server->removeListener('propFind', [$aclPlugin, 'propFind']);
-
-		$result = $aclPlugin->principalSearch(
-			['{http://sabredav.org/ns}email-address' => $this->stripOffMailTo($email)],
-			[
-				'{DAV:}principal-URL',
-				'{' . self::NS_CALDAV . '}calendar-home-set',
-				'{' . self::NS_CALDAV . '}schedule-inbox-URL',
-				'{http://sabredav.org/ns}email-address',
-
-			]
-		);
-		$this->server->on('propFind', [$aclPlugin, 'propFind'], 20);
-
-
-		// Grabbing the calendar list
-		$objects = [];
-		$calendarTimeZone = new DateTimeZone('UTC');
-
-		$homePath = $result[0][200]['{' . self::NS_CALDAV . '}calendar-home-set']->getHref();
-		/** @var Calendar $node */
-		foreach ($this->server->tree->getNodeForPath($homePath)->getChildren() as $node) {
-
-			if (!$node instanceof ICalendar) {
-				continue;
-			}
-
-			// Getting the list of object uris within the time-range
-			$urls = $node->calendarQuery([
-				'name' => 'VCALENDAR',
-				'comp-filters' => [
-					[
-						'name' => 'VEVENT',
-						'is-not-defined' => false,
-						'time-range' => [
-							'start' => $start,
-							'end' => $end,
-						],
-						'comp-filters' => [],
-						'prop-filters' => [],
-					],
-					[
-						'name' => 'VEVENT',
-						'is-not-defined' => false,
-						'time-range' => null,
-						'comp-filters' => [],
-						'prop-filters' => [
-							[
-								'name' => 'UID',
-								'is-not-defined' => false,
-								'time-range' => null,
-								'text-match' => [
-									'value' => $ignoreUID,
-									'negate-condition' => true,
-									'collation' => 'i;octet',
-								],
-								'param-filters' => [],
-							],
-						]
-					],
-				],
-				'prop-filters' => [],
-				'is-not-defined' => false,
-				'time-range' => null,
-			]);
-
-			foreach ($urls as $url) {
-				$objects[] = $node->getChild($url)->get();
-			}
-		}
-
-		$inboxProps = $this->server->getProperties(
-			$result[0][200]['{' . self::NS_CALDAV . '}schedule-inbox-URL']->getHref(),
-			['{' . self::NS_CALDAV . '}calendar-availability']
-		);
-
-		$vcalendar = new VCalendar();
-		$vcalendar->METHOD = 'REPLY';
-
-		$generator = new FreeBusyGenerator();
-		$generator->setObjects($objects);
-		$generator->setTimeRange($start, $end);
-		$generator->setBaseObject($vcalendar);
-		$generator->setTimeZone($calendarTimeZone);
-
-		if (isset($inboxProps['{' . self::NS_CALDAV . '}calendar-availability'])) {
-			$generator->setVAvailability(
-				Reader::read(
-					$inboxProps['{' . self::NS_CALDAV . '}calendar-availability']
-				)
-			);
-		}
-
-		$result = $generator->getResult();
-		if (!isset($result->VFREEBUSY)) {
-			return false;
-		}
-
-		/** @var Component $freeBusyComponent */
-		$freeBusyComponent = $result->VFREEBUSY;
-		$freeBusyProperties = $freeBusyComponent->select('FREEBUSY');
-		// If there is no Free-busy property at all, the time-range is empty and available
-		if (count($freeBusyProperties) === 0) {
-			return true;
-		}
-
-		// If more than one Free-Busy property was returned, it means that an event
-		// starts or ends inside this time-range, so it's not available and we return false
-		if (count($freeBusyProperties) > 1) {
-			return false;
-		}
-
-		/** @var Property $freeBusyProperty */
-		$freeBusyProperty = $freeBusyProperties[0];
-		if (!$freeBusyProperty->offsetExists('FBTYPE')) {
-			// If there is no FBTYPE, it means it's busy
-			return false;
-		}
-
-		$fbTypeParameter = $freeBusyProperty->offsetGet('FBTYPE');
-		if (!($fbTypeParameter instanceof Parameter)) {
-			return false;
-		}
-
-		return (strcasecmp($fbTypeParameter->getValue(), 'FREE') === 0);
-	}
-
-	/**
-	 * @param string $email
-	 * @return string
-	 */
-	private function stripOffMailTo(string $email): string {
-		if (stripos($email, 'mailto:') === 0) {
-			return substr($email, 7);
-		}
-
-		return $email;
-	}
-
-	private function getCalendar(CalendarHome $calendarHome, string $uri): INode {
-		return $calendarHome->getChild($uri);
-	}
-
-	private function isCalendarDeleted(CalendarHome $calendarHome, string $uri): bool {
-		$calendar = $this->getCalendar($calendarHome, $uri);
-		return $calendar instanceof Calendar && $calendar->isDeleted();
-	}
-
-	private function createCalendar(CalendarHome $calendarHome, string $principalUri, string $uri, string $displayName): void {
-		$calendarHome->getCalDAVBackend()->createCalendar($principalUri, $uri, [
-			'{DAV:}displayname' => $displayName,
-		]);
-	}
-
-	private function moveCalendar(CalDavBackend $calDavBackend, string $principalUri, string $oldUri, string $newUri): void {
-		$calDavBackend->moveCalendar($oldUri, $principalUri, $principalUri, $newUri);
-	}
-
-	/**
-	 * Try to handle the given exception gracefully or throw it if necessary.
-	 *
-	 * @throws SameOrganizerForAllComponentsException If the exception should not be ignored
-	 */
-	private function handleSameOrganizerException(
-		SameOrganizerForAllComponentsException $e,
-		VCalendar $vCal,
-		string $calendarPath,
-	): void {
-		// This is very hacky! However, we want to allow saving events with multiple
-		// organizers. Those events are not RFC compliant, but sometimes imported from major
-		// external calendar services (e.g. Google). If the current user is not an organizer of
-		// the event we ignore the exception as no scheduling messages will be sent anyway.
-
-		// It would be cleaner to patch Sabre to validate organizers *after* checking if
-		// scheduling messages are necessary. Currently, organizers are validated first and
-		// afterwards the broker checks if messages should be scheduled. So the code will throw
-		// even if the organizers are not relevant. This is to ensure compliance with RFCs but
-		// a bit too strict for real world usage.
-
-		if (!isset($vCal->VEVENT)) {
-			throw $e;
-		}
-
-		$calendarNode = $this->server->tree->getNodeForPath($calendarPath);
-		if (!($calendarNode instanceof IACL)) {
-			// Should always be an instance of IACL but just to be sure
-			throw $e;
-		}
-
-		$addresses = $this->getAddressesForPrincipal($calendarNode->getOwner());
-		foreach ($vCal->VEVENT as $vevent) {
-			if (in_array($vevent->ORGANIZER->getNormalizedValue(), $addresses, true)) {
-				// User is an organizer => throw the exception
-				throw $e;
-			}
-		}
-	}
+        if ($this->isAvailableAtTime($attendee->getValue(), $dtstart->getDateTime(), $dtend->getDateTime(), $uid)) {
+            $partStat = 'ACCEPTED';
+        } else {
+            $partStat = 'DECLINED';
+        }
+
+        $vObject = Reader::read(vsprintf($message, [
+            $partStat,
+            $iTipMessage->recipient,
+            $iTipMessage->sender,
+            $uid,
+            $sequence,
+            $recurrenceId
+        ]));
+
+        $responseITipMessage = new ITip\Message();
+        $responseITipMessage->uid = $uid;
+        $responseITipMessage->component = 'VEVENT';
+        $responseITipMessage->method = 'REPLY';
+        $responseITipMessage->sequence = $sequence;
+        $responseITipMessage->sender = $iTipMessage->recipient;
+        $responseITipMessage->recipient = $iTipMessage->sender;
+        $responseITipMessage->message = $vObject;
+
+        // We can't dispatch them now already, because the organizers calendar-object
+        // was not yet created. Hence Sabre/DAV won't find a calendar-object, when we
+        // send our reply.
+        $this->schedulingResponses[] = $responseITipMessage;
+    }
+
+    /**
+     * @param string $uri
+     */
+    public function dispatchSchedulingResponses(string $uri):void {
+        if ($uri !== $this->pathOfCalendarObjectChange) {
+            return;
+        }
+
+        foreach ($this->schedulingResponses as $schedulingResponse) {
+            $this->scheduleLocalDelivery($schedulingResponse);
+        }
+    }
+
+    /**
+     * Always use the personal calendar as target for scheduled events
+     *
+     * @param PropFind $propFind
+     * @param INode $node
+     * @return void
+     */
+    public function propFindDefaultCalendarUrl(PropFind $propFind, INode $node) {
+        if ($node instanceof IPrincipal) {
+            $propFind->handle(self::SCHEDULE_DEFAULT_CALENDAR_URL, function () use ($node) {
+                /** @var \OCA\DAV\CalDAV\Plugin $caldavPlugin */
+                $caldavPlugin = $this->server->getPlugin('caldav');
+                $principalUrl = $node->getPrincipalUrl();
+
+                $calendarHomePath = $caldavPlugin->getCalendarHomeForPrincipal($principalUrl);
+                if (!$calendarHomePath) {
+                    return null;
+                }
+
+                $isResourceOrRoom = str_starts_with($principalUrl, 'principals/calendar-resources') ||
+                    str_starts_with($principalUrl, 'principals/calendar-rooms');
+
+                if (str_starts_with($principalUrl, 'principals/users')) {
+                    [, $userId] = split($principalUrl);
+                    $uri = $this->config->getUserValue($userId, 'dav', 'defaultCalendar', CalDavBackend::PERSONAL_CALENDAR_URI);
+                    $displayName = CalDavBackend::PERSONAL_CALENDAR_NAME;
+                } elseif ($isResourceOrRoom) {
+                    $uri = CalDavBackend::RESOURCE_BOOKING_CALENDAR_URI;
+                    $displayName = CalDavBackend::RESOURCE_BOOKING_CALENDAR_NAME;
+                } else {
+                    // How did we end up here?
+                    // TODO - throw exception or just ignore?
+                    return null;
+                }
+
+                /** @var CalendarHome $calendarHome */
+                $calendarHome = $this->server->tree->getNodeForPath($calendarHomePath);
+                $currentCalendarDeleted = false;
+                if (!$calendarHome->childExists($uri) || $currentCalendarDeleted = $this->isCalendarDeleted($calendarHome, $uri)) {
+                    // If the default calendar doesn't exist
+                    if ($isResourceOrRoom) {
+                        // Resources or rooms can't be in the trashbin, so we're fine
+                        $this->createCalendar($calendarHome, $principalUrl, $uri, $displayName);
+                    } else {
+                        // And we're not handling scheduling on resource/room booking
+                        $userCalendars = [];
+                        /**
+                         * If the default calendar of the user isn't set and the
+                         * fallback doesn't match any of the user's calendar
+                         * try to find the first "personal" calendar we can write to
+                         * instead of creating a new one.
+                         * A appropriate personal calendar to receive invites:
+                         * - isn't a calendar subscription
+                         * - user can write to it (no virtual/3rd-party calendars)
+                         * - calendar isn't a share
+                         * - calendar supports VEVENTs
+                         */
+                        foreach ($calendarHome->getChildren() as $node) {
+                            if (!($node instanceof Calendar)) {
+                                continue;
+                            }
+
+                            try {
+                                $this->defaultCalendarValidator->validateScheduleDefaultCalendar($node);
+                            } catch (DavException $e) {
+                                continue;
+                            }
+
+                            $userCalendars[] = $node;
+                        }
+
+                        if (count($userCalendars) > 0) {
+                            // Calendar backend returns calendar by calendarorder property
+                            $uri = $userCalendars[0]->getName();
+                        } else {
+                            // Otherwise if we have really nothing, create a new calendar
+                            if ($currentCalendarDeleted) {
+                                // If the calendar exists but is in the trash bin, we try to rename its uri
+                                // so that we can create the new one and still restore the previous one
+                                // otherwise we just purge the calendar by removing it before recreating it
+                                $calendar = $this->getCalendar($calendarHome, $uri);
+                                if ($calendar instanceof Calendar) {
+                                    $backend = $calendarHome->getCalDAVBackend();
+                                    if ($backend instanceof CalDavBackend) {
+                                        // If the CalDAV backend supports moving calendars
+                                        $this->moveCalendar($backend, $principalUrl, $uri, $uri . '-back-' . time());
+                                    } else {
+                                        // Otherwise just purge the calendar
+                                        $calendar->disableTrashbin();
+                                        $calendar->delete();
+                                    }
+                                }
+                            }
+                            $this->createCalendar($calendarHome, $principalUrl, $uri, $displayName);
+                        }
+                    }
+                }
+
+                $result = $this->server->getPropertiesForPath($calendarHomePath . '/' . $uri, [], 1);
+                if (empty($result)) {
+                    return null;
+                }
+
+                return new LocalHref($result[0]['href']);
+            });
+        }
+    }
+
+    /**
+     * Returns a list of addresses that are associated with a principal.
+     *
+     * @param string $principal
+     * @return string|null
+     */
+    protected function getCalendarUserTypeForPrincipal($principal):?string {
+        $calendarUserType = '{' . self::NS_CALDAV . '}calendar-user-type';
+        $properties = $this->server->getProperties(
+            $principal,
+            [$calendarUserType]
+        );
+
+        // If we can't find this information, we'll stop processing
+        if (!isset($properties[$calendarUserType])) {
+            return null;
+        }
+
+        return $properties[$calendarUserType];
+    }
+
+    /**
+     * @param ITip\Message $iTipMessage
+     * @return null|Property
+     */
+    private function getCurrentAttendee(ITip\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 Property|null $attendee
+     * @return bool
+     */
+    private function getAttendeeRSVP(?Property $attendee = null):bool {
+        if ($attendee !== null) {
+            $rsvp = $attendee->offsetGet('RSVP');
+            if (($rsvp instanceof Parameter) && (strcasecmp($rsvp->getValue(), 'TRUE') === 0)) {
+                return true;
+            }
+        }
+        // RFC 5545 3.2.17: default RSVP is false
+        return false;
+    }
+
+    /**
+     * @param VEvent $vevent
+     * @return Property\ICalendar\DateTime
+     */
+    private function getDTEndFromVEvent(VEvent $vevent):Property\ICalendar\DateTime {
+        if (isset($vevent->DTEND)) {
+            return $vevent->DTEND;
+        }
+
+        if (isset($vevent->DURATION)) {
+            $isFloating = $vevent->DTSTART->isFloating();
+            /** @var Property\ICalendar\DateTime $end */
+            $end = clone $vevent->DTSTART;
+            $endDateTime = $end->getDateTime();
+            $endDateTime = $endDateTime->add(DateTimeParser::parse($vevent->DURATION->getValue()));
+            $end->setDateTime($endDateTime, $isFloating);
+            return $end;
+        }
+
+        if (!$vevent->DTSTART->hasTime()) {
+            $isFloating = $vevent->DTSTART->isFloating();
+            /** @var Property\ICalendar\DateTime $end */
+            $end = clone $vevent->DTSTART;
+            $endDateTime = $end->getDateTime();
+            $endDateTime = $endDateTime->modify('+1 day');
+            $end->setDateTime($endDateTime, $isFloating);
+            return $end;
+        }
+
+        return clone $vevent->DTSTART;
+    }
+
+    /**
+     * @param string $email
+     * @param \DateTimeInterface $start
+     * @param \DateTimeInterface $end
+     * @param string $ignoreUID
+     * @return bool
+     */
+    private function isAvailableAtTime(string $email, \DateTimeInterface $start, \DateTimeInterface $end, string $ignoreUID):bool {
+        // This method is heavily inspired by Sabre\CalDAV\Schedule\Plugin::scheduleLocalDelivery
+        // and Sabre\CalDAV\Schedule\Plugin::getFreeBusyForEmail
+
+        $aclPlugin = $this->server->getPlugin('acl');
+        $this->server->removeListener('propFind', [$aclPlugin, 'propFind']);
+
+        $result = $aclPlugin->principalSearch(
+            ['{http://sabredav.org/ns}email-address' => $this->stripOffMailTo($email)],
+            [
+                '{DAV:}principal-URL',
+                '{' . self::NS_CALDAV . '}calendar-home-set',
+                '{' . self::NS_CALDAV . '}schedule-inbox-URL',
+                '{http://sabredav.org/ns}email-address',
+
+            ]
+        );
+        $this->server->on('propFind', [$aclPlugin, 'propFind'], 20);
+
+
+        // Grabbing the calendar list
+        $objects = [];
+        $calendarTimeZone = new DateTimeZone('UTC');
+
+        $homePath = $result[0][200]['{' . self::NS_CALDAV . '}calendar-home-set']->getHref();
+        /** @var Calendar $node */
+        foreach ($this->server->tree->getNodeForPath($homePath)->getChildren() as $node) {
+
+            if (!$node instanceof ICalendar) {
+                continue;
+            }
+
+            // Getting the list of object uris within the time-range
+            $urls = $node->calendarQuery([
+                'name' => 'VCALENDAR',
+                'comp-filters' => [
+                    [
+                        'name' => 'VEVENT',
+                        'is-not-defined' => false,
+                        'time-range' => [
+                            'start' => $start,
+                            'end' => $end,
+                        ],
+                        'comp-filters' => [],
+                        'prop-filters' => [],
+                    ],
+                    [
+                        'name' => 'VEVENT',
+                        'is-not-defined' => false,
+                        'time-range' => null,
+                        'comp-filters' => [],
+                        'prop-filters' => [
+                            [
+                                'name' => 'UID',
+                                'is-not-defined' => false,
+                                'time-range' => null,
+                                'text-match' => [
+                                    'value' => $ignoreUID,
+                                    'negate-condition' => true,
+                                    'collation' => 'i;octet',
+                                ],
+                                'param-filters' => [],
+                            ],
+                        ]
+                    ],
+                ],
+                'prop-filters' => [],
+                'is-not-defined' => false,
+                'time-range' => null,
+            ]);
+
+            foreach ($urls as $url) {
+                $objects[] = $node->getChild($url)->get();
+            }
+        }
+
+        $inboxProps = $this->server->getProperties(
+            $result[0][200]['{' . self::NS_CALDAV . '}schedule-inbox-URL']->getHref(),
+            ['{' . self::NS_CALDAV . '}calendar-availability']
+        );
+
+        $vcalendar = new VCalendar();
+        $vcalendar->METHOD = 'REPLY';
+
+        $generator = new FreeBusyGenerator();
+        $generator->setObjects($objects);
+        $generator->setTimeRange($start, $end);
+        $generator->setBaseObject($vcalendar);
+        $generator->setTimeZone($calendarTimeZone);
+
+        if (isset($inboxProps['{' . self::NS_CALDAV . '}calendar-availability'])) {
+            $generator->setVAvailability(
+                Reader::read(
+                    $inboxProps['{' . self::NS_CALDAV . '}calendar-availability']
+                )
+            );
+        }
+
+        $result = $generator->getResult();
+        if (!isset($result->VFREEBUSY)) {
+            return false;
+        }
+
+        /** @var Component $freeBusyComponent */
+        $freeBusyComponent = $result->VFREEBUSY;
+        $freeBusyProperties = $freeBusyComponent->select('FREEBUSY');
+        // If there is no Free-busy property at all, the time-range is empty and available
+        if (count($freeBusyProperties) === 0) {
+            return true;
+        }
+
+        // If more than one Free-Busy property was returned, it means that an event
+        // starts or ends inside this time-range, so it's not available and we return false
+        if (count($freeBusyProperties) > 1) {
+            return false;
+        }
+
+        /** @var Property $freeBusyProperty */
+        $freeBusyProperty = $freeBusyProperties[0];
+        if (!$freeBusyProperty->offsetExists('FBTYPE')) {
+            // If there is no FBTYPE, it means it's busy
+            return false;
+        }
+
+        $fbTypeParameter = $freeBusyProperty->offsetGet('FBTYPE');
+        if (!($fbTypeParameter instanceof Parameter)) {
+            return false;
+        }
+
+        return (strcasecmp($fbTypeParameter->getValue(), 'FREE') === 0);
+    }
+
+    /**
+     * @param string $email
+     * @return string
+     */
+    private function stripOffMailTo(string $email): string {
+        if (stripos($email, 'mailto:') === 0) {
+            return substr($email, 7);
+        }
+
+        return $email;
+    }
+
+    private function getCalendar(CalendarHome $calendarHome, string $uri): INode {
+        return $calendarHome->getChild($uri);
+    }
+
+    private function isCalendarDeleted(CalendarHome $calendarHome, string $uri): bool {
+        $calendar = $this->getCalendar($calendarHome, $uri);
+        return $calendar instanceof Calendar && $calendar->isDeleted();
+    }
+
+    private function createCalendar(CalendarHome $calendarHome, string $principalUri, string $uri, string $displayName): void {
+        $calendarHome->getCalDAVBackend()->createCalendar($principalUri, $uri, [
+            '{DAV:}displayname' => $displayName,
+        ]);
+    }
+
+    private function moveCalendar(CalDavBackend $calDavBackend, string $principalUri, string $oldUri, string $newUri): void {
+        $calDavBackend->moveCalendar($oldUri, $principalUri, $principalUri, $newUri);
+    }
+
+    /**
+     * Try to handle the given exception gracefully or throw it if necessary.
+     *
+     * @throws SameOrganizerForAllComponentsException If the exception should not be ignored
+     */
+    private function handleSameOrganizerException(
+        SameOrganizerForAllComponentsException $e,
+        VCalendar $vCal,
+        string $calendarPath,
+    ): void {
+        // This is very hacky! However, we want to allow saving events with multiple
+        // organizers. Those events are not RFC compliant, but sometimes imported from major
+        // external calendar services (e.g. Google). If the current user is not an organizer of
+        // the event we ignore the exception as no scheduling messages will be sent anyway.
+
+        // It would be cleaner to patch Sabre to validate organizers *after* checking if
+        // scheduling messages are necessary. Currently, organizers are validated first and
+        // afterwards the broker checks if messages should be scheduled. So the code will throw
+        // even if the organizers are not relevant. This is to ensure compliance with RFCs but
+        // a bit too strict for real world usage.
+
+        if (!isset($vCal->VEVENT)) {
+            throw $e;
+        }
+
+        $calendarNode = $this->server->tree->getNodeForPath($calendarPath);
+        if (!($calendarNode instanceof IACL)) {
+            // Should always be an instance of IACL but just to be sure
+            throw $e;
+        }
+
+        $addresses = $this->getAddressesForPrincipal($calendarNode->getOwner());
+        foreach ($vCal->VEVENT as $vevent) {
+            if (in_array($vevent->ORGANIZER->getNormalizedValue(), $addresses, true)) {
+                // User is an organizer => throw the exception
+                throw $e;
+            }
+        }
+    }
 }