Support recurring events + repeating alarms

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

20 files changed, 1908 insertions, 576 deletions

diff --git a/apps/dav/appinfo/info.xml b/apps/dav/appinfo/info.xml
index 6e0219e91dd..81b93de055d 100644
--- a/apps/dav/appinfo/info.xml
+++ b/apps/dav/appinfo/info.xml
@@ -5,7 +5,7 @@
 	<name>WebDAV</name>
 	<summary>WebDAV endpoint</summary>
 	<description>WebDAV endpoint</description>
-	<version>1.11.1</version>
+	<version>1.13.0</version>
 	<licence>agpl</licence>
 	<author>owncloud.org</author>
 	<namespace>DAV</namespace>
diff --git a/apps/dav/composer/composer/autoload_classmap.php b/apps/dav/composer/composer/autoload_classmap.php
index bd26290cc9a..a1c2d671b8a 100644
--- a/apps/dav/composer/composer/autoload_classmap.php
+++ b/apps/dav/composer/composer/autoload_classmap.php
@@ -52,9 +52,10 @@ return array(
     'OCA\\DAV\\CalDAV\\PublicCalendarRoot' => $baseDir . '/../lib/CalDAV/PublicCalendarRoot.php',
     'OCA\\DAV\\CalDAV\\Publishing\\PublishPlugin' => $baseDir . '/../lib/CalDAV/Publishing/PublishPlugin.php',
     'OCA\\DAV\\CalDAV\\Publishing\\Xml\\Publisher' => $baseDir . '/../lib/CalDAV/Publishing/Xml/Publisher.php',
-    'OCA\\DAV\\CalDAV\\Reminder\\AbstractNotificationProvider' => $baseDir . '/../lib/CalDAV/Reminder/AbstractNotificationProvider.php',
     'OCA\\DAV\\CalDAV\\Reminder\\Backend' => $baseDir . '/../lib/CalDAV/Reminder/Backend.php',
+    'OCA\\DAV\\CalDAV\\Reminder\\INotificationProvider' => $baseDir . '/../lib/CalDAV/Reminder/INotificationProvider.php',
     'OCA\\DAV\\CalDAV\\Reminder\\NotificationProviderManager' => $baseDir . '/../lib/CalDAV/Reminder/NotificationProviderManager.php',
+    'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\AbstractProvider' => $baseDir . '/../lib/CalDAV/Reminder/NotificationProvider/AbstractProvider.php',
     'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\AudioProvider' => $baseDir . '/../lib/CalDAV/Reminder/NotificationProvider/AudioProvider.php',
     'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\EmailProvider' => $baseDir . '/../lib/CalDAV/Reminder/NotificationProvider/EmailProvider.php',
     'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\ProviderNotAvailableException' => $baseDir . '/../lib/CalDAV/Reminder/NotificationProvider/ProviderNotAvailableException.php',
@@ -188,7 +189,6 @@ return array(
     'OCA\\DAV\\Migration\\Version1005Date20180530124431' => $baseDir . '/../lib/Migration/Version1005Date20180530124431.php',
     'OCA\\DAV\\Migration\\Version1006Date20180619154313' => $baseDir . '/../lib/Migration/Version1006Date20180619154313.php',
     'OCA\\DAV\\Migration\\Version1006Date20180628111625' => $baseDir . '/../lib/Migration/Version1006Date20180628111625.php',
-    'OCA\\DAV\\Migration\\Version1007Date20181005133326' => $baseDir . '/../lib/Migration/Version1007Date20181005133326.php',
     'OCA\\DAV\\Migration\\Version1008Date20181030113700' => $baseDir . '/../lib/Migration/Version1008Date20181030113700.php',
     'OCA\\DAV\\Migration\\Version1008Date20181105104826' => $baseDir . '/../lib/Migration/Version1008Date20181105104826.php',
     'OCA\\DAV\\Migration\\Version1008Date20181105104833' => $baseDir . '/../lib/Migration/Version1008Date20181105104833.php',
@@ -197,6 +197,7 @@ return array(
     'OCA\\DAV\\Migration\\Version1008Date20181114084440' => $baseDir . '/../lib/Migration/Version1008Date20181114084440.php',
     'OCA\\DAV\\Migration\\Version1011Date20190725113607' => $baseDir . '/../lib/Migration/Version1011Date20190725113607.php',
     'OCA\\DAV\\Migration\\Version1011Date20190806104428' => $baseDir . '/../lib/Migration/Version1011Date20190806104428.php',
+    'OCA\\DAV\\Migration\\Version1012Date20190808122342' => $baseDir . '/../lib/Migration/Version1012Date20190808122342.php',
     'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningNode' => $baseDir . '/../lib/Provisioning/Apple/AppleProvisioningNode.php',
     'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningPlugin' => $baseDir . '/../lib/Provisioning/Apple/AppleProvisioningPlugin.php',
     'OCA\\DAV\\RootCollection' => $baseDir . '/../lib/RootCollection.php',
diff --git a/apps/dav/composer/composer/autoload_static.php b/apps/dav/composer/composer/autoload_static.php
index 1a0ce9d02f0..39488419f87 100644
--- a/apps/dav/composer/composer/autoload_static.php
+++ b/apps/dav/composer/composer/autoload_static.php
@@ -67,9 +67,10 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\CalDAV\\PublicCalendarRoot' => __DIR__ . '/..' . '/../lib/CalDAV/PublicCalendarRoot.php',
         'OCA\\DAV\\CalDAV\\Publishing\\PublishPlugin' => __DIR__ . '/..' . '/../lib/CalDAV/Publishing/PublishPlugin.php',
         'OCA\\DAV\\CalDAV\\Publishing\\Xml\\Publisher' => __DIR__ . '/..' . '/../lib/CalDAV/Publishing/Xml/Publisher.php',
-        'OCA\\DAV\\CalDAV\\Reminder\\AbstractNotificationProvider' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/AbstractNotificationProvider.php',
         'OCA\\DAV\\CalDAV\\Reminder\\Backend' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/Backend.php',
+        'OCA\\DAV\\CalDAV\\Reminder\\INotificationProvider' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/INotificationProvider.php',
         'OCA\\DAV\\CalDAV\\Reminder\\NotificationProviderManager' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/NotificationProviderManager.php',
+        'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\AbstractProvider' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/NotificationProvider/AbstractProvider.php',
         'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\AudioProvider' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/NotificationProvider/AudioProvider.php',
         'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\EmailProvider' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/NotificationProvider/EmailProvider.php',
         'OCA\\DAV\\CalDAV\\Reminder\\NotificationProvider\\ProviderNotAvailableException' => __DIR__ . '/..' . '/../lib/CalDAV/Reminder/NotificationProvider/ProviderNotAvailableException.php',
@@ -203,7 +204,6 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Migration\\Version1005Date20180530124431' => __DIR__ . '/..' . '/../lib/Migration/Version1005Date20180530124431.php',
         'OCA\\DAV\\Migration\\Version1006Date20180619154313' => __DIR__ . '/..' . '/../lib/Migration/Version1006Date20180619154313.php',
         'OCA\\DAV\\Migration\\Version1006Date20180628111625' => __DIR__ . '/..' . '/../lib/Migration/Version1006Date20180628111625.php',
-        'OCA\\DAV\\Migration\\Version1007Date20181005133326' => __DIR__ . '/..' . '/../lib/Migration/Version1007Date20181005133326.php',
         'OCA\\DAV\\Migration\\Version1008Date20181030113700' => __DIR__ . '/..' . '/../lib/Migration/Version1008Date20181030113700.php',
         'OCA\\DAV\\Migration\\Version1008Date20181105104826' => __DIR__ . '/..' . '/../lib/Migration/Version1008Date20181105104826.php',
         'OCA\\DAV\\Migration\\Version1008Date20181105104833' => __DIR__ . '/..' . '/../lib/Migration/Version1008Date20181105104833.php',
@@ -212,6 +212,7 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Migration\\Version1008Date20181114084440' => __DIR__ . '/..' . '/../lib/Migration/Version1008Date20181114084440.php',
         'OCA\\DAV\\Migration\\Version1011Date20190725113607' => __DIR__ . '/..' . '/../lib/Migration/Version1011Date20190725113607.php',
         'OCA\\DAV\\Migration\\Version1011Date20190806104428' => __DIR__ . '/..' . '/../lib/Migration/Version1011Date20190806104428.php',
+        'OCA\\DAV\\Migration\\Version1012Date20190808122342' => __DIR__ . '/..' . '/../lib/Migration/Version1012Date20190808122342.php',
         'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningNode' => __DIR__ . '/..' . '/../lib/Provisioning/Apple/AppleProvisioningNode.php',
         'OCA\\DAV\\Provisioning\\Apple\\AppleProvisioningPlugin' => __DIR__ . '/..' . '/../lib/Provisioning/Apple/AppleProvisioningPlugin.php',
         'OCA\\DAV\\RootCollection' => __DIR__ . '/..' . '/../lib/RootCollection.php',
diff --git a/apps/dav/lib/AppInfo/Application.php b/apps/dav/lib/AppInfo/Application.php
index 5d17dc5a241..80e9dea8829 100644
--- a/apps/dav/lib/AppInfo/Application.php
+++ b/apps/dav/lib/AppInfo/Application.php
@@ -231,12 +231,10 @@ class Application extends App {
 			);
 
 			/** @var ReminderService $reminderBackend */
-			$reminderService= $this->getContainer()->query(ReminderService::class);
+			$reminderService = $this->getContainer()->query(ReminderService::class);
 
 			$reminderService->onTouchCalendarObject(
 				$eventName,
-				$event->getArgument('calendarData'),
-				$event->getArgument('shares'),
 				$event->getArgument('objectData')
 			);
 		};
diff --git a/apps/dav/lib/CalDAV/Reminder/AbstractNotificationProvider.php b/apps/dav/lib/CalDAV/Reminder/AbstractNotificationProvider.php
deleted file mode 100644
index 1d858627de9..00000000000
--- a/apps/dav/lib/CalDAV/Reminder/AbstractNotificationProvider.php
+++ /dev/null
@@ -1,205 +0,0 @@
-<?php
-/**
- * @copyright Copyright (c) 2018 Thomas Citharel <tcit@tcit.fr>
- *
- * @author Thomas Citharel <tcit@tcit.fr>
- *
- * @license GNU AGPL version 3 or any later version
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as
- * published by the Free Software Foundation, either version 3 of the
- * License, or (at your option) any later version.
- *
- * 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
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- *
- */
-
-namespace OCA\DAV\CalDAV\Reminder;
-
-use \DateTime;
-use \DateTimeImmutable;
-use OCP\IConfig;
-use OCP\IL10N;
-use OCP\ILogger;
-use OCP\IURLGenerator;
-use OCP\L10N\IFactory as L10NFactory;
-use OCP\IUser;
-use Sabre\VObject\Component\VCalendar;
-use Sabre\VObject\Component\VEvent;
-use Sabre\VObject\DateTimeParser;
-use Sabre\VObject\Parameter;
-use Sabre\VObject\Property;
-
-abstract class AbstractNotificationProvider {
-
-	/** @var string */
-	public const NOTIFICATION_TYPE = '';
-
-    /** @var ILogger */
-    protected $logger;
-
-    /** @var L10NFactory */
-    protected $l10nFactory;
-
-    /** @var IL10N */
-    protected $l10n;
-
-    /** @var IURLGenerator */
-    protected $urlGenerator;
-
-    /** @var IConfig */
-	protected $config;
-
-	/**
-	 * @param ILogger $logger
-	 * @param L10NFactory $l10nFactory
-	 * @param IConfig $config
-	 * @param IUrlGenerator $urlGenerator
-	 */
-	public function __construct(ILogger $logger, L10NFactory $l10nFactory, IURLGenerator $urlGenerator, IConfig $config) {
-		$this->logger = $logger;
-		$this->l10nFactory = $l10nFactory;
-        $this->urlGenerator = $urlGenerator;
-		$this->config = $config;
-    }
-
-	/**
-	 * Send notification
-	 *
-	 * @param VCalendar $vcalendar
-	 * @param string $calendarDisplayName
-	 * @param IUser $user
-	 * @return void
-	 */
-    abstract function send(VCalendar $vcalendar, string $calendarDisplayName, IUser $user): void;
-
-	/**
-	 * @var VCalendar $vcalendar
-	 * @var string $defaultValue
-	 * @return array
-	 * @throws \Exception
-	 */
-    protected function extractEventDetails(VCalendar $vcalendar, $defaultValue = ''):array {
-		/** @var VEvent $vevent */
-        $vevent = $vcalendar->VEVENT;
-
-        /** @var Property $start */
-		$start = $vevent->DTSTART;
-		if (isset($vevent->DTEND)) {
-			$end = $vevent->DTEND;
-		} elseif (isset($vevent->DURATION)) {
-			$isFloating = $vevent->DTSTART->isFloating();
-			$end = clone $vevent->DTSTART;
-			$endDateTime = $end->getDateTime();
-			$endDateTime = $endDateTime->add(DateTimeParser::parse($vevent->DURATION->getValue()));
-			$end->setDateTime($endDateTime, $isFloating);
-		} elseif (!$vevent->DTSTART->hasTime()) {
-			$isFloating = $vevent->DTSTART->isFloating();
-			$end = clone $vevent->DTSTART;
-			$endDateTime = $end->getDateTime();
-			$endDateTime = $endDateTime->modify('+1 day');
-			$end->setDateTime($endDateTime, $isFloating);
-		} else {
-			$end = clone $vevent->DTSTART;
-		}
-
-        return [
-            'title' => (string) $vevent->SUMMARY ?: $defaultValue,
-            'description' => (string) $vevent->DESCRIPTION ?: $defaultValue,
-            'start'=> $start->getDateTime(),
-            'end' => $end->getDateTime(),
-            'when' => $this->generateWhenString($start, $end),
-            'url' => (string) $vevent->URL ?: $defaultValue,
-            'location' => (string) $vevent->LOCATION ?: $defaultValue,
-            'uid' => (string) $vevent->UID,
-        ];
-    }
-
-	/**
-	 * @param Property $dtstart
-	 * @param Property $dtend
-	 * @return string
-	 * @throws \Exception
-	 */
-	private function generateWhenString(Property $dtstart, Property $dtend):string {
-		$isAllDay = $dtstart instanceof Property\ICalendar\Date;
-
-		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtstart */
-		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtend */
-		/** @var DateTimeImmutable $dtstartDt */
-		$dtstartDt = $dtstart->getDateTime();
-		/** @var DateTimeImmutable $dtendDt */
-		$dtendDt = $dtend->getDateTime();
-
-		$diff = $dtstartDt->diff($dtendDt);
-
-		$dtstartDt = new DateTime($dtstartDt->format(DateTime::ATOM));
-		$dtendDt = new DateTime($dtendDt->format(DateTime::ATOM));
-
-		if ($isAllDay) {
-			// One day event
-			if ($diff->days === 1) {
-				return $this->l10n->l('date', $dtstartDt, ['width' => 'medium']);
-			}
-
-			//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 . ' (' . $endTimezone . ')';
-		}
-
-		// show only end time if date is the same
-		if ($this->isDayEqual($dtstartDt, $dtendDt)) {
-			$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 DateTime $dtStart
-	 * @param DateTime $dtEnd
-	 * @return bool
-	 */
-    private function isDayEqual(DateTime $dtStart, DateTime $dtEnd):bool {
-		return $dtStart->format('Y-m-d') === $dtEnd->format('Y-m-d');
-	}
-}
diff --git a/apps/dav/lib/CalDAV/Reminder/Backend.php b/apps/dav/lib/CalDAV/Reminder/Backend.php
index 087a5785f36..be65c35da0f 100644
--- a/apps/dav/lib/CalDAV/Reminder/Backend.php
+++ b/apps/dav/lib/CalDAV/Reminder/Backend.php
@@ -1,8 +1,11 @@
 <?php
+declare(strict_types=1);
 /**
- * @copyright Copyright (c) 2019 Thomas Citharel <tcit@tcit.fr>
+ * @copyright Copyright (c) 2019, Thomas Citharel
+ * @copyright Copyright (c) 2019, Georg Ehrke
  *
  * @author Thomas Citharel <tcit@tcit.fr>
+ * @author Georg Ehrke <oc.list@georgehrke.com>
  *
  * @license GNU AGPL version 3 or any later version
  *
@@ -20,7 +23,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
 namespace OCA\DAV\CalDAV\Reminder;
 
 use OCP\IDBConnection;
@@ -40,95 +42,178 @@ class Backend {
 	private $timeFactory;
 
 	/**
+	 * Backend constructor.
+	 *
 	 * @param IDBConnection $db
 	 * @param ITimeFactory $timeFactory
 	 */
-	public function __construct(IDBConnection $db, ITimeFactory $timeFactory) {
+	public function __construct(IDBConnection $db,
+								ITimeFactory $timeFactory) {
 		$this->db = $db;
 		$this->timeFactory = $timeFactory;
 	}
 
 	/**
+	 * Get all reminders with a notification date before now
+	 *
+	 * @return array
+	 * @throws \Exception
+	 */
+	public function getRemindersToProcess():array {
+		$query = $this->db->getQueryBuilder();
+		$query->select(['cr.*', 'co.calendardata', 'c.displayname', 'c.principaluri'])
+			->from('calendar_reminders', 'cr')
+//			->where($query->expr()->lte('cr.notification_date', $query->createNamedParameter($this->timeFactory->getTime())))
+			->leftJoin('cr', 'calendarobjects', 'co', $query->expr()->eq('cr.object_id', 'co.id'))
+			->leftJoin('cr', 'calendars', 'c', $query->expr()->eq('cr.calendar_id', 'c.id'));
+		$stmt = $query->execute();
+
+		return array_map(
+			[$this, 'fixRowTyping'],
+			$stmt->fetchAll()
+		);
+	}
+
+	/**
+	 * Get all scheduled reminders for an event
+	 *
+	 * @param int $objectId
+	 * @return array
+	 */
+	public function getAllScheduledRemindersForEvent(int $objectId):array {
+		$query = $this->db->getQueryBuilder();
+		$query->select('*')
+			->from('calendar_reminders')
+			->where($query->expr()->eq('object_id', $query->createNamedParameter($objectId)));
+		$stmt = $query->execute();
+
+		return array_map(
+			[$this, 'fixRowTyping'],
+			$stmt->fetchAll()
+		);
+	}
+
+	/**
+	 * Insert a new reminder into the database
+	 *
+	 * @param int $calendarId
+	 * @param int $objectId
 	 * @param string $uid
-	 * @param string $calendarId
-	 * @param string $uri
+	 * @param bool $isRecurring
+	 * @param int $recurrenceId
+	 * @param bool $isRecurrenceException
+	 * @param string $eventHash
+	 * @param string $alarmHash
 	 * @param string $type
+	 * @param bool $isRelative
 	 * @param int $notificationDate
-	 * @param int $eventStartDate
+	 * @param bool $isRepeatBased
+	 * @return int The insert id
 	 */
-	public function insertReminder(string $uid, string $calendarId, string $uri, string $type, int $notificationDate, int $eventStartDate):void {
+	public function insertReminder(int $calendarId,
+								   int $objectId,
+								   string $uid,
+								   bool $isRecurring,
+								   int $recurrenceId,
+								   bool $isRecurrenceException,
+								   string $eventHash,
+								   string $alarmHash,
+								   string $type,
+								   bool $isRelative,
+								   int $notificationDate,
+								   bool $isRepeatBased):int {
 		$query = $this->db->getQueryBuilder();
 		$query->insert('calendar_reminders')
 			->values([
+				'calendar_id' => $query->createNamedParameter($calendarId),
+				'object_id' => $query->createNamedParameter($objectId),
 				'uid' => $query->createNamedParameter($uid),
-				'calendarid' => $query->createNamedParameter($calendarId),
-				'objecturi' => $query->createNamedParameter($uri),
+				'is_recurring' => $query->createNamedParameter($isRecurring ? 1 : 0),
+				'recurrence_id' => $query->createNamedParameter($recurrenceId),
+				'is_recurrence_exception' => $query->createNamedParameter($isRecurrenceException ? 1 : 0),
+				'event_hash' => $query->createNamedParameter($eventHash),
+				'alarm_hash' => $query->createNamedParameter($alarmHash),
 				'type' => $query->createNamedParameter($type),
-				'notificationdate' => $query->createNamedParameter($notificationDate),
-				'eventstartdate' => $query->createNamedParameter($eventStartDate),
-			])->execute();
+				'is_relative' => $query->createNamedParameter($isRelative ? 1 : 0),
+				'notification_date' => $query->createNamedParameter($notificationDate),
+				'is_repeat_based' => $query->createNamedParameter($isRepeatBased ? 1 : 0),
+			])
+			->execute();
+
+		return $query->getLastInsertId();
 	}
 
 	/**
-	 * Cleans reminders in database
+	 * Sets a new notificationDate on an existing reminder
 	 *
-	 * @param int $calendarId
-	 * @param string $objectUri
+	 * @param int $reminderId
+	 * @param int $newNotificationDate
 	 */
-	public function cleanRemindersForEvent(int $calendarId, string $objectUri):void {
+	public function updateReminder(int $reminderId,
+								   int $newNotificationDate):void {
 		$query = $this->db->getQueryBuilder();
-
-		$query->delete('calendar_reminders')
-			->where($query->expr()->eq('calendarid', $query->createNamedParameter($calendarId)))
-			->andWhere($query->expr()->eq('objecturi', $query->createNamedParameter($objectUri)))
+		$query->update('calendar_reminders')
+			->set('notification_date', $query->createNamedParameter($newNotificationDate))
+			->where($query->expr()->eq('id', $query->createNamedParameter($reminderId)))
 			->execute();
 	}
 
 	/**
-	 * Remove all reminders for a calendar
+	 * Remove a reminder by it's id
 	 *
-	 * @param integer $calendarId
+	 * @param integer $reminderId
 	 * @return void
 	 */
-	public function cleanRemindersForCalendar(int $calendarId):void {
+	public function removeReminder(int $reminderId):void {
 		$query = $this->db->getQueryBuilder();
 
 		$query->delete('calendar_reminders')
-			->where($query->expr()->eq('calendarid', $query->createNamedParameter($calendarId)))
+			->where($query->expr()->eq('id', $query->createNamedParameter($reminderId)))
 			->execute();
 	}
 
 	/**
-	 * Remove a reminder by it's id
+	 * Cleans reminders in database
 	 *
-	 * @param integer $reminderId
-	 * @return void
+	 * @param int $objectId
 	 */
-	public function removeReminder(int $reminderId):void {
+	public function cleanRemindersForEvent(int $objectId):void {
 		$query = $this->db->getQueryBuilder();
 
 		$query->delete('calendar_reminders')
-			->where($query->expr()->eq('id', $query->createNamedParameter($reminderId)))
+			->where($query->expr()->eq('object_id', $query->createNamedParameter($objectId)))
 			->execute();
 	}
 
 	/**
-	 * Get all reminders with a notification date before now
+	 * Remove all reminders for a calendar
 	 *
-	 * @return array
-	 * @throws \Exception
+	 * @param int $calendarId
+	 * @return void
 	 */
-	public function getRemindersToProcess():array {
+	public function cleanRemindersForCalendar(int $calendarId):void {
 		$query = $this->db->getQueryBuilder();
-		$fields = ['cr.id', 'cr.calendarid', 'cr.objecturi', 'cr.type', 'cr.notificationdate', 'cr.uid', 'co.calendardata', 'c.displayname'];
-		$stmt = $query->select($fields)
-			->from('calendar_reminders', 'cr')
-			->where($query->expr()->lte('cr.notificationdate', $query->createNamedParameter($this->timeFactory->getTime())))
-			->andWhere($query->expr()->gte('cr.eventstartdate', $query->createNamedParameter($this->timeFactory->getTime()))) # We check that DTSTART isn't before
-			->leftJoin('cr', 'calendars', 'c', $query->expr()->eq('cr.calendarid', 'c.id'))
-			->leftJoin('cr', 'calendarobjects', 'co', $query->expr()->andX($query->expr()->eq('cr.calendarid', 'c.id'), $query->expr()->eq('co.uri', 'cr.objecturi')))
+
+		$query->delete('calendar_reminders')
+			->where($query->expr()->eq('calendar_id', $query->createNamedParameter($calendarId)))
 			->execute();
+	}
+
+	/**
+	 * @param array $row
+	 * @return array
+	 */
+	private function fixRowTyping(array $row): array {
+		$row['id'] = (int) $row['id'];
+		$row['calendar_id'] = (int) $row['calendar_id'];
+		$row['object_id'] = (int) $row['object_id'];
+		$row['is_recurring'] = (bool) $row['is_recurring'];
+		$row['recurrence_id'] = (int) $row['recurrence_id'];
+		$row['is_recurrence_exception'] = (bool) $row['is_recurrence_exception'];
+		$row['is_relative'] = (bool) $row['is_relative'];
+		$row['notification_date'] = (int) $row['notification_date'];
+		$row['is_repeat_based'] = (bool) $row['is_repeat_based'];
 
-		return $stmt->fetchAll();
+		return $row;
 	}
 }
diff --git a/apps/dav/lib/CalDAV/Reminder/INotificationProvider.php b/apps/dav/lib/CalDAV/Reminder/INotificationProvider.php
new file mode 100644
index 00000000000..d0e526eb0ee
--- /dev/null
+++ b/apps/dav/lib/CalDAV/Reminder/INotificationProvider.php
@@ -0,0 +1,47 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019, Georg Ehrke
+ *
+ * @author Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+namespace OCA\DAV\CalDAV\Reminder;
+
+use OCP\IUser;
+use Sabre\VObject\Component\VEvent;
+
+/**
+ * Interface INotificationProvider
+ *
+ * @package OCA\DAV\CalDAV\Reminder
+ */
+interface INotificationProvider {
+
+	/**
+	 * Send notification
+	 *
+	 * @param VEvent $vevent
+	 * @param string $calendarDisplayName
+	 * @param IUser[] $users
+	 * @return void
+	 */
+	public function send(VEvent $vevent,
+						 string $calendarDisplayName,
+						 array $users=[]): void;
+}
\ No newline at end of file
diff --git a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/AbstractProvider.php b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/AbstractProvider.php
new file mode 100644
index 00000000000..6b2364c8022
--- /dev/null
+++ b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/AbstractProvider.php
@@ -0,0 +1,191 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2019, Thomas Citharel
+ * @copyright Copyright (c) 2019, Georg Ehrke
+ *
+ * @author Thomas Citharel <tcit@tcit.fr>
+ * @author Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+namespace OCA\DAV\CalDAV\Reminder\NotificationProvider;
+
+use \DateTime;
+use \DateTimeImmutable;
+use OCA\DAV\CalDAV\Reminder\INotificationProvider;
+use OCP\IConfig;
+use OCP\IL10N;
+use OCP\ILogger;
+use OCP\IURLGenerator;
+use OCP\L10N\IFactory as L10NFactory;
+use OCP\IUser;
+use Sabre\VObject\Component\VEvent;
+use Sabre\VObject\DateTimeParser;
+use Sabre\VObject\Parameter;
+use Sabre\VObject\Property;
+
+/**
+ * Class AbstractProvider
+ *
+ * @package OCA\DAV\CalDAV\Reminder\NotificationProvider
+ */
+abstract class AbstractProvider implements INotificationProvider  {
+
+	/** @var string */
+	public const NOTIFICATION_TYPE = '';
+
+    /** @var ILogger */
+    protected $logger;
+
+    /** @var L10NFactory */
+    private $l10nFactory;
+
+    /** @var IL10N[] */
+	private $l10ns;
+
+	/** @var string */
+	private $fallbackLanguage;
+
+    /** @var IURLGenerator */
+    protected $urlGenerator;
+
+    /** @var IConfig */
+	protected $config;
+
+	/**
+	 * @param ILogger $logger
+	 * @param L10NFactory $l10nFactory
+	 * @param IConfig $config
+	 * @param IUrlGenerator $urlGenerator
+	 */
+	public function __construct(ILogger $logger,
+								L10NFactory $l10nFactory,
+								IURLGenerator $urlGenerator,
+								IConfig $config) {
+		$this->logger = $logger;
+		$this->l10nFactory = $l10nFactory;
+        $this->urlGenerator = $urlGenerator;
+		$this->config = $config;
+    }
+
+	/**
+	 * Send notification
+	 *
+	 * @param VEvent $vevent
+	 * @param string $calendarDisplayName
+	 * @param IUser[] $users
+	 * @return void
+	 */
+    abstract public function send(VEvent $vevent,
+						   string $calendarDisplayName,
+						   array $users=[]): void;
+
+	/**
+	 * @return string
+	 */
+    protected function getFallbackLanguage():string {
+    	if ($this->fallbackLanguage) {
+    		return $this->fallbackLanguage;
+		}
+
+    	$fallbackLanguage = $this->l10nFactory->findLanguage();
+    	$this->fallbackLanguage = $fallbackLanguage;
+
+    	return $fallbackLanguage;
+	}
+
+	/**
+	 * @param string $lang
+	 * @return bool
+	 */
+	protected function hasL10NForLang(string $lang):bool {
+    	return $this->l10nFactory->languageExists('dav', $lang);
+	}
+
+	/**
+	 * @param string $lang
+	 * @return IL10N
+	 */
+	protected function getL10NForLang(string $lang):IL10N {
+		if (isset($this->l10ns[$lang])) {
+			return $this->l10ns[$lang];
+		}
+
+		$l10n = $this->l10nFactory->get('dav', $lang);
+		$this->l10ns[$lang] = $l10n;
+
+		return $l10n;
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return string
+	 */
+	private function getStatusOfEvent(VEvent $vevent):string {
+		if ($vevent->STATUS) {
+			return (string) $vevent->STATUS;
+		}
+
+		// Doesn't say so in the standard,
+		// but we consider events without a status
+		// to be confirmed
+		return 'CONFIRMED';
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return bool
+	 */
+	protected function isEventTentative(VEvent $vevent):bool {
+		return $this->getStatusOfEvent($vevent) === 'TENTATIVE';
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return Property\ICalendar\DateTime
+	 */
+	protected function getDTEndFromEvent(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;
+	}
+}
diff --git a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/AudioProvider.php b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/AudioProvider.php
index 6e702bcacaa..ad4ac342f66 100644
--- a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/AudioProvider.php
+++ b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/AudioProvider.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * @copyright Copyright (c) 2019, Georg Ehrke
  *
diff --git a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/EmailProvider.php b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/EmailProvider.php
index f05439932b6..2a7eb2a4032 100644
--- a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/EmailProvider.php
+++ b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/EmailProvider.php
@@ -1,8 +1,11 @@
 <?php
+declare(strict_types=1);
 /**
- * @copyright Copyright (c) 2018 Thomas Citharel <tcit@tcit.fr>
+ * @copyright Copyright (c) 2019, Thomas Citharel
+ * @copyright Copyright (c) 2019, Georg Ehrke
  *
  * @author Thomas Citharel <tcit@tcit.fr>
+ * @author Georg Ehrke <oc.list@georgehrke.com>
  *
  * @license GNU AGPL version 3 or any later version
  *
@@ -20,27 +23,36 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
 namespace OCA\DAV\CalDAV\Reminder\NotificationProvider;
 
-use OCA\DAV\CalDAV\Reminder\AbstractNotificationProvider;
+use DateTime;
+use DateTimeImmutable;
 use OCP\IConfig;
+use OCP\IL10N;
 use OCP\ILogger;
 use OCP\IURLGenerator;
 use OCP\L10N\IFactory as L10NFactory;
 use OCP\Mail\IEMailTemplate;
 use OCP\Mail\IMailer;
 use OCP\IUser;
-use Sabre\VObject\Component\VCalendar;
-
-class EmailProvider extends AbstractNotificationProvider {
+use Sabre\VObject\Component\VEvent;
+use Sabre\VObject;
+use Sabre\VObject\Parameter;
+use Sabre\VObject\Property;
 
-	/** @var IMailer */
-	private $mailer;
+/**
+ * Class EmailProvider
+ *
+ * @package OCA\DAV\CalDAV\Reminder\NotificationProvider
+ */
+class EmailProvider extends AbstractProvider {
 
 	/** @var string */
 	public const NOTIFICATION_TYPE = 'EMAIL';
 
+	/** @var IMailer */
+	private $mailer;
+
 	/**
 	 * @param IConfig $config
 	 * @param IMailer $mailer
@@ -48,7 +60,9 @@ class EmailProvider extends AbstractNotificationProvider {
 	 * @param L10NFactory $l10nFactory
 	 * @param IUrlGenerator $urlGenerator
 	 */
-	public function __construct(IConfig $config, IMailer $mailer, ILogger $logger,
+	public function __construct(IConfig $config,
+								IMailer $mailer,
+								ILogger $logger,
 								L10NFactory $l10nFactory,
 								IURLGenerator $urlGenerator) {
 		parent::__construct($logger, $l10nFactory, $urlGenerator, $config);
@@ -56,90 +70,100 @@ class EmailProvider extends AbstractNotificationProvider {
 	}
 
 	/**
-	 * Send notification
+	 * Send out notification via email
 	 *
-	 * @param VCalendar $vcalendar
+	 * @param VEvent $vevent
 	 * @param string $calendarDisplayName
-	 * @param IUser $user
-	 * @return void
+	 * @param array $users
 	 * @throws \Exception
 	 */
-	public function send(VCalendar $vcalendar, string $calendarDisplayName, IUser $user):void {
-		if ($user->getEMailAddress() === null) {
-			return;
-		}
+	public function send(VEvent $vevent,
+						 string $calendarDisplayName,
+						 array $users=[]):void {
+		$fallbackLanguage = $this->getFallbackLanguage();
 
-		$lang = $this->config->getUserValue($user->getUID(), 'core', 'lang', $this->l10nFactory->findLanguage());
-		$this->l10n = $this->l10nFactory->get('dav', $lang);
+		$emailAddressesOfSharees = $this->getEMailAddressesOfAllUsersWithWriteAccessToCalendar($users);
+		$emailAddressesOfAttendees = $this->getAllEMailAddressesFromEvent($vevent);
 
-		$event = $this->extractEventDetails($vcalendar);
-		$fromEMail = \OCP\Util::getDefaultEmailAddress('invitations-noreply');
+		// Quote from php.net:
+		// If the input arrays have the same string keys, then the later value for that key will overwrite the previous one.
+		// => if there are duplicate email addresses, it will always take the system value
+		$emailAddresses = array_merge(
+			$emailAddressesOfAttendees,
+			$emailAddressesOfSharees
+		);
 
-		$message = $this->mailer->createMessage()
-			->setFrom([$fromEMail => 'Nextcloud'])
-			// TODO: Set reply to from event creator
-			// ->setReplyTo([$sender => $senderName])
-			->setTo([$user->getEMailAddress() => $user->getDisplayName()]);
+		$sortedByLanguage = $this->sortEMailAddressesByLanguage($emailAddresses, $fallbackLanguage);
+		$organizer = $this->getOrganizerEMailAndNameFromEvent($vevent);
+
+		foreach($sortedByLanguage as $lang => $emailAddresses) {
+			if ($this->hasL10NForLang($lang)) {
+				$lang = $fallbackLanguage;
+			}
+			$l10n = $this->getL10NForLang($lang);
+			$fromEMail = \OCP\Util::getDefaultEmailAddress('reminders-noreply');
 
-		$template = $this->mailer->createEMailTemplate('dav.calendarReminder', $event);
-		$template->addHeader();
+			$message = $this->mailer->createMessage();
+			$message->setFrom([$fromEMail]);
+			if ($organizer) {
+				$message->setReplyTo($organizer);
+			}
+			$message->setBcc($emailAddresses);
 
-		$this->addSubjectAndHeading($template, $event['title']);
-		$this->addBulletList($template, $event, $calendarDisplayName);
+			$template = $this->mailer->createEMailTemplate('dav.calendarReminder');
+			$template->addHeader();
 
-		$template->addFooter();
-		$message->useTemplate($template);
+			$this->addSubjectAndHeading($template, $l10n, $vevent);
+			$this->addBulletList($template, $l10n, $calendarDisplayName, $vevent);
 
-		$attachment = $this->mailer->createAttachment(
-			$vcalendar->serialize(),
-			$event['uid'].'.ics',// TODO(leon): Make file name unique, e.g. add event id
-			'text/calendar'
-		);
-		$message->attach($attachment);
+			$template->addFooter();
+			$message->useTemplate($template);
 
-		try {
-			$failed = $this->mailer->send($message);
-			if ($failed) {
-				$this->logger->error('Unable to deliver message to {failed}', ['app' => 'dav', 'failed' =>  implode(', ', $failed)]);
+			try {
+				$failed = $this->mailer->send($message);
+				if ($failed) {
+					$this->logger->error('Unable to deliver message to {failed}', ['app' => 'dav', 'failed' => implode(', ', $failed)]);
+				}
+			} catch (\Exception $ex) {
+				$this->logger->logException($ex, ['app' => 'dav']);
 			}
-		} catch(\Exception $ex) {
-			$this->logger->logException($ex, ['app' => 'dav']);
 		}
 	}
 
 	/**
 	 * @param IEMailTemplate $template
-	 * @param string $summary
+	 * @param IL10N $l10n
+	 * @param VEvent $vevent
 	 */
-	private function addSubjectAndHeading(IEMailTemplate $template, string $summary):void {
-		$template->setSubject('Notification: ' . $summary);
-		$template->addHeading($summary);
+	private function addSubjectAndHeading(IEMailTemplate $template, IL10N $l10n, VEvent $vevent):void {
+		$template->setSubject('Notification: ' . $this->getTitleFromVEvent($vevent, $l10n));
+		$template->addHeading($this->getTitleFromVEvent($vevent, $l10n));
 	}
 
 	/**
 	 * @param IEMailTemplate $template
-	 * @param array $eventData
+	 * @param IL10N $l10n
 	 * @param string $calendarDisplayName
+	 * @param array $eventData
 	 */
-	private function addBulletList(IEMailTemplate $template, array $eventData, string $calendarDisplayName):void {
-		$template->addBodyListItem($calendarDisplayName, $this->l10n->t('Calendar:'),
+	private function addBulletList(IEMailTemplate $template,
+								   IL10N $l10n,
+								   string $calendarDisplayName,
+								   VEvent $vevent):void {
+		$template->addBodyListItem($calendarDisplayName, $l10n->t('Calendar:'),
 			$this->getAbsoluteImagePath('actions/info.svg'));
 
-		$template->addBodyListItem($eventData['when'], $this->l10n->t('Date:'),
+		$template->addBodyListItem($this->generateDateString($l10n, $vevent), $l10n->t('Date:'),
 			$this->getAbsoluteImagePath('places/calendar.svg'));
 
-		if ($eventData['location']) {
-			$template->addBodyListItem((string) $eventData['location'], $this->l10n->t('Where:'),
+		if (isset($vevent->LOCATION)) {
+			$template->addBodyListItem((string) $vevent->LOCATION, $l10n->t('Where:'),
 				$this->getAbsoluteImagePath('actions/address.svg'));
 		}
-		if ($eventData['description']) {
-			$template->addBodyListItem((string) $eventData['description'], $this->l10n->t('Description:'),
+		if (isset($vevent->DESCRIPTION)) {
+			$template->addBodyListItem((string) $vevent->DESCRIPTION, $l10n->t('Description:'),
 				$this->getAbsoluteImagePath('actions/more.svg'));
 		}
-		if ($eventData['url']) {
-			$template->addBodyListItem((string) $eventData['url'], $this->l10n->t('Link:'),
-				$this->getAbsoluteImagePath('places/link.svg'));
-		}
     }
 
     /**
@@ -151,4 +175,355 @@ class EmailProvider extends AbstractNotificationProvider {
 			$this->urlGenerator->imagePath('core', $path)
 		);
 	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return array|null
+	 */
+	private function getOrganizerEMailAndNameFromEvent(VEvent $vevent):?array {
+		if (!$vevent->ORGANIZER) {
+			return null;
+		}
+
+		$organizer = $vevent->ORGANZIER;
+		if (strcasecmp($organizer->getValue(), 'mailto:') !== 0) {
+			return null;
+		}
+
+		$organizerEMail = substr($organizer->getValue(), 7);
+
+		$name = $organizer->offsetGet('CN');
+		if ($name instanceof Parameter) {
+			return [$organizerEMail => $name];
+		}
+
+		return [$organizerEMail];
+	}
+
+	/**
+	 * @param array $sortedByLanguage
+	 * @param IUser[] $users
+	 * @param string $defaultLanguage
+	 */
+	private function sortUsersByLanguage(array &$sortedByLanguage,
+										 array $users,
+										 string $defaultLanguage):void {
+		/**
+		 * @var array $sortedByLanguage
+		 * [
+		 *   'de' => ['a@b.com', 'c@d.com'],
+		 *   ...
+		 * ]
+		 */
+		foreach($users as $user) {
+			/** @var IUser $user */
+			$emailAddress = $user->getEMailAddress();
+			$lang = $this->config->getUserValue($user->getUID(),
+				'core', 'lang', $defaultLanguage);
+
+			if (!isset($sortedByLanguage[$lang])) {
+				$sortedByLanguage[$lang] = [];
+			}
+
+			$sortedByLanguage[$lang][] = $emailAddress;
+		}
+	}
+
+	/**
+	 * @param array $emails
+	 * @param string $defaultLanguage
+	 * @return array
+	 */
+	private function sortEMailAddressesByLanguage(array $emails,
+												  string $defaultLanguage):array {
+		$sortedByLanguage = [];
+
+		foreach($emails as $emailAddress => $parameters) {
+			if (isset($parameters['LANG'])) {
+				$lang = $parameters['LANG'];
+			} else {
+				$lang = $defaultLanguage;
+			}
+
+			if (!isset($sortedByLanguage[$lang])) {
+				$sortedByLanguage[$lang] = [];
+			}
+
+			$sortedByLanguage[$lang][] = $emailAddress;
+		}
+
+		return $sortedByLanguage;
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return array
+	 */
+	private function getAllEMailAddressesFromEvent(VEvent $vevent):array {
+		$emailAddresses = [];
+
+		if (isset($vevent->ATTENDEE)) {
+			foreach ($vevent->ATTENDEE as $attendee) {
+				if (!($attendee instanceof VObject\Property)) {
+					continue;
+				}
+
+				$cuType = $this->getCUTypeOfAttendee($attendee);
+				if (\in_array($cuType, ['RESOURCE', 'ROOM', 'UNKNOWN'])) {
+					// Don't send emails to things
+					continue;
+				}
+
+				$partstat = $this->getPartstatOfAttendee($attendee);
+				if ($partstat === 'DECLINED') {
+					// Don't send out emails to people who declined
+					continue;
+				}
+				if ($partstat === 'DELEGATED') {
+					$delegates = $attendee->offsetGet('DELEGATED-TO');
+					if (!($delegates instanceof VObject\Parameter)) {
+						continue;
+					}
+
+					$emailAddressesOfDelegates = $delegates->getParts();
+					foreach($emailAddressesOfDelegates as $addressesOfDelegate) {
+						if (strcasecmp($addressesOfDelegate, 'mailto:') === 0) {
+							$emailAddresses[substr($addressesOfDelegate, 7)] = [];
+						}
+					}
+
+					continue;
+				}
+
+				$emailAddressOfAttendee = $this->getEMailAddressOfAttendee($attendee);
+				if ($emailAddressOfAttendee !== null) {
+					$properties = [];
+
+					$langProp = $attendee->offsetGet('LANG');
+					if ($langProp instanceof VObject\Parameter) {
+						$properties['LANG'] = $langProp->getValue();
+					}
+
+					$emailAddresses[$emailAddressOfAttendee] = $properties;
+				}
+			}
+		}
+
+		if (isset($vevent->ORGANIZER)) {
+			$emailAddresses[$this->getEMailAddressOfAttendee($vevent->ORGANIZER)] = [];
+		}
+
+		return $emailAddresses;
+	}
+
+
+
+	/**
+	 * @param VObject\Property $attendee
+	 * @return string
+	 */
+	private function getCUTypeOfAttendee(VObject\Property $attendee):string {
+		$cuType = $attendee->offsetGet('CUTYPE');
+		if ($cuType instanceof VObject\Parameter) {
+			return strtoupper($cuType->getValue());
+		}
+
+		return 'INDIVIDUAL';
+	}
+
+	/**
+	 * @param VObject\Property $attendee
+	 * @return string
+	 */
+	private function getPartstatOfAttendee(VObject\Property $attendee):string {
+		$partstat = $attendee->offsetGet('PARTSTAT');
+		if ($partstat instanceof VObject\Parameter) {
+			return strtoupper($partstat->getValue());
+		}
+
+		return 'NEEDS-ACTION';
+	}
+
+	/**
+	 * @param VObject\Property $attendee
+	 * @return bool
+	 */
+	private function hasAttendeeMailURI(VObject\Property $attendee):bool {
+		return strcasecmp($attendee->getValue(), 'mailto:') === 0;
+	}
+
+	/**
+	 * @param VObject\Property $attendee
+	 * @return string|null
+	 */
+	private function getEMailAddressOfAttendee(VObject\Property $attendee):?string {
+		if (!$this->hasAttendeeMailURI($attendee)) {
+			return null;
+		}
+
+		return substr($attendee->getValue(), 7);
+	}
+
+	/**
+	 * @param array $users
+	 * @return array
+	 */
+	private function getEMailAddressesOfAllUsersWithWriteAccessToCalendar(array $users):array {
+		$emailAddresses = [];
+
+		foreach($users as $user) {
+			$emailAddress = $user->getEMailAddress();
+			if ($emailAddress) {
+				$lang = $this->getLangForUser($user);
+				if ($lang) {
+					$emailAddresses[$emailAddress] = [
+						'LANG' => $lang,
+					];
+				} else {
+					$emailAddresses[$emailAddress] = [];
+				}
+			}
+		}
+
+		return array_unique($emailAddresses);
+	}
+
+	/**
+	 * @param IUser $user
+	 * @return string
+	 */
+	private function getLangForUser(IUser $user): ?string {
+		return $this->config->getUserValue($user->getUID(), 'core', 'lang', null);
+	}
+
+	/**
+	 * @param IL10N $l10n
+	 * @param VEvent $vevent
+	 * @return string
+	 * @throws \Exception
+	 */
+	private function generateDateString(IL10N $l10n, VEvent $vevent):string {
+		$isAllDay = $vevent->DTSTART instanceof Property\ICalendar\Date;
+
+		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtstart */
+		/** @var Property\ICalendar\Date | Property\ICalendar\DateTime $dtend */
+		/** @var \DateTimeImmutable $dtstartDt */
+		$dtstartDt = $vevent->DTSTART->getDateTime();
+		/** @var \DateTimeImmutable $dtendDt */
+		$dtendDt = $this->getDTEndFromEvent($vevent)->getDateTime();
+
+		$diff = $dtstartDt->diff($dtendDt);
+
+		$dtstartDt = new \DateTime($dtstartDt->format(\DateTime::ATOM));
+		$dtendDt = new \DateTime($dtendDt->format(\DateTime::ATOM));
+
+		if ($isAllDay) {
+			// One day event
+			if ($diff->days === 1) {
+				return $this->getDateString($l10n, $dtstartDt);
+			}
+
+			return implode(' - ', [
+				$this->getDateString($l10n, $dtstartDt),
+				$this->getDateString($l10n, $dtendDt),
+			]);
+		}
+
+		$startTimezone = $endTimezone = null;
+		if (!$vevent->DTSTART->isFloating()) {
+			$startTimezone = $vevent->DTSTART->getDateTime()->getTimezone()->getName();
+			$endTimezone = $this->getDTEndFromEvent($vevent)->getDateTime()->getTimezone()->getName();
+		}
+
+		$localeStart = implode(', ', [
+			$this->getWeekDayName($l10n, $dtstartDt),
+			$this->getDateTimeString($l10n, $dtstartDt)
+		]);
+
+		// always show full date with timezone if timezones are different
+		if ($startTimezone !== $endTimezone) {
+			$localeEnd = implode(', ', [
+				$this->getWeekDayName($l10n, $dtendDt),
+				$this->getDateTimeString($l10n, $dtendDt)
+			]);
+
+			return $localeStart
+				. ' (' . $startTimezone . ') '
+				. ' - '
+				. $localeEnd
+				. ' (' . $endTimezone . ')';
+		}
+
+		// Show only the time if the day is the same
+		$localeEnd = $this->isDayEqual($dtstartDt, $dtendDt)
+			? $this->getTimeString($l10n, $dtendDt)
+			: implode(', ', [
+				$this->getWeekDayName($l10n, $dtendDt),
+				$this->getDateTimeString($l10n, $dtendDt)
+			]);
+
+		return $localeStart
+			. ' - '
+			. $localeEnd
+			. ' (' . $startTimezone . ')';
+	}
+
+	/**
+	 * @param DateTime $dtStart
+	 * @param DateTime $dtEnd
+	 * @return bool
+	 */
+	private function isDayEqual(DateTime $dtStart,
+								DateTime $dtEnd):bool {
+		return $dtStart->format('Y-m-d') === $dtEnd->format('Y-m-d');
+	}
+
+	/**
+	 * @param IL10N $l10n
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getWeekDayName(IL10N $l10n, DateTime $dt):string {
+		return $l10n->l('weekdayName', $dt, ['width' => 'abbreviated']);
+	}
+
+	/**
+	 * @param IL10N $l10n
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getDateString(IL10N $l10n, DateTime $dt):string {
+		return $l10n->l('date', $dt, ['width' => 'medium']);
+	}
+
+	/**
+	 * @param IL10N $l10n
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getDateTimeString(IL10N $l10n, DateTime $dt):string {
+		return $l10n->l('datetime', $dt, ['width' => 'medium|short']);
+	}
+
+	/**
+	 * @param IL10N $l10n
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getTimeString(IL10N $l10n, DateTime $dt):string {
+		return $l10n->l('time', $dt, ['width' => 'short']);
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @param IL10N $l10n
+	 * @return string
+	 */
+	private function getTitleFromVEvent(VEvent $vevent, IL10N $l10n):string {
+		if (isset($vevent->SUMMARY)) {
+			return (string)$vevent->SUMMARY;
+		}
+
+		return $l10n->t('Untitled event');
+	}
 }
diff --git a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/ProviderNotAvailableException.php b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/ProviderNotAvailableException.php
index bf736db8a34..bfa6db95852 100644
--- a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/ProviderNotAvailableException.php
+++ b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/ProviderNotAvailableException.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 /**
  * @copyright Copyright (c) 2018 Thomas Citharel <tcit@tcit.fr>
  *
@@ -20,7 +21,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
 namespace OCA\DAV\CalDAV\Reminder\NotificationProvider;
 
 class ProviderNotAvailableException extends \Exception {
diff --git a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/PushProvider.php b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/PushProvider.php
index f04b8e4c45a..2e580fd78a3 100644
--- a/apps/dav/lib/CalDAV/Reminder/NotificationProvider/PushProvider.php
+++ b/apps/dav/lib/CalDAV/Reminder/NotificationProvider/PushProvider.php
@@ -1,8 +1,11 @@
 <?php
+declare(strict_types=1);
 /**
- * @copyright Copyright (c) 2018 Thomas Citharel <tcit@tcit.fr>
+ * @copyright Copyright (c) 2019, Thomas Citharel
+ * @copyright Copyright (c) 2019, Georg Ehrke
  *
  * @author Thomas Citharel <tcit@tcit.fr>
+ * @author Georg Ehrke <oc.list@georgehrke.com>
  *
  * @license GNU AGPL version 3 or any later version
  *
@@ -20,11 +23,9 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-
 namespace OCA\DAV\CalDAV\Reminder\NotificationProvider;
 
 use OCA\DAV\AppInfo\Application;
-use OCA\DAV\CalDAV\Reminder\AbstractNotificationProvider;
 use OCP\IConfig;
 use OCP\ILogger;
 use OCP\IURLGenerator;
@@ -32,22 +33,24 @@ use OCP\L10N\IFactory as L10NFactory;
 use OCP\Notification\IManager;
 use OCP\IUser;
 use OCP\Notification\INotification;
-use Sabre\VObject\Component\VCalendar;
 use OCP\AppFramework\Utility\ITimeFactory;
+use Sabre\VObject\Component\VEvent;
+use Sabre\VObject\Property;
 
-class PushProvider extends AbstractNotificationProvider {
+/**
+ * Class PushProvider
+ *
+ * @package OCA\DAV\CalDAV\Reminder\NotificationProvider
+ */
+class PushProvider extends AbstractProvider {
 
 	/** @var string */
 	public const NOTIFICATION_TYPE = 'DISPLAY';
 
-    /**
-     * @var IManager
-     */
+    /** @var IManager */
 	private $manager;
 
-	/**
-	 * @var ITimeFactory
-	 */
+	/** @var ITimeFactory */
 	private $timeFactory;
 
 	/**
@@ -58,42 +61,75 @@ class PushProvider extends AbstractNotificationProvider {
 	 * @param IUrlGenerator $urlGenerator
 	 * @param ITimeFactory $timeFactory
 	 */
-	public function __construct(IConfig $config, IManager $manager, ILogger $logger,
+	public function __construct(IConfig $config,
+								IManager $manager,
+								ILogger $logger,
 								L10NFactory $l10nFactory,
-								IURLGenerator $urlGenerator, ITimeFactory $timeFactory) {
+								IURLGenerator $urlGenerator,
+								ITimeFactory $timeFactory) {
 		parent::__construct($logger, $l10nFactory, $urlGenerator, $config);
 		$this->manager = $manager;
 		$this->timeFactory = $timeFactory;
     }
 
 	/**
-	 * Send notification
+	 * Send push notification to all users.
 	 *
-	 * @param VCalendar $vcalendar
+	 * @param VEvent $vevent
 	 * @param string $calendarDisplayName
-	 * @param IUser $user
-	 * @return void
+	 * @param IUser[] $users
 	 * @throws \Exception
 	 */
-    public function send(VCalendar $vcalendar, string $calendarDisplayName, IUser $user):void {
-		$lang = $this->config->getUserValue($user->getUID(), 'core', 'lang', $this->l10nFactory->findLanguage());
-		$this->l10n = $this->l10nFactory->get('dav', $lang);
+    public function send(VEvent $vevent,
+						 string $calendarDisplayName=null,
+						 array $users=[]):void {
+		$eventDetails = $this->extractEventDetails($vevent);
+		$eventDetails['calendar_displayname'] = $calendarDisplayName;
 
-		$event = $this->extractEventDetails($vcalendar);
-		/** @var INotification $notification */
-		$notification = $this->manager->createNotification();
-		$notification->setApp(Application::APP_ID)
-			->setUser($user->getUID())
-			->setDateTime($this->timeFactory->getDateTime())
-			->setObject(Application::APP_ID, $event['uid']) // $type and $id
-			->setSubject('calendar_reminder', ['title' => $event['title'], 'start' => $event['start']->getTimestamp()]) // $subject and $parameters
-			->setMessage('calendar_reminder', [
-				'when' => $event['when'],
-				'description' => $event['description'],
-				'location' => $event['location'],
-				'calendar' => $calendarDisplayName
-			])
-		;
-		$this->manager->notify($notification);
+    	foreach($users as $user) {
+			/** @var INotification $notification */
+			$notification = $this->manager->createNotification();
+			$notification->setApp(Application::APP_ID)
+				->setUser($user->getUID())
+				->setDateTime($this->timeFactory->getDateTime())
+				->setObject(Application::APP_ID, (string) $vevent->UID)
+				->setSubject('calendar_reminder', [
+					'title' => $eventDetails['title'],
+					'start_atom' => $eventDetails['start_atom']
+				])
+				->setMessage('calendar_reminder', $eventDetails);
+
+			$this->manager->notify($notification);
+		}
     }
+
+	/**
+	 * @var VEvent $vevent
+	 * @return array
+	 * @throws \Exception
+	 */
+	protected function extractEventDetails(VEvent $vevent):array {
+		/** @var Property\ICalendar\DateTime $start */
+		$start = $vevent->DTSTART;
+		$end = $this->getDTEndFromEvent($vevent);
+
+		return [
+			'title' => isset($vevent->SUMMARY)
+				? ((string) $vevent->SUMMARY)
+				: null,
+			'description' => isset($vevent->DESCRIPTION)
+				? ((string) $vevent->DESCRIPTION)
+				: null,
+			'location' => isset($vevent->LOCATION)
+				? ((string) $vevent->LOCATION)
+				: null,
+			'all_day' => $start instanceof Property\ICalendar\Date,
+			'start_atom' => $start->getDateTime()->format(\DateTime::ATOM),
+			'start_is_floating' => $start->isFloating(),
+			'start_timezone' => $start->getDateTime()->getTimezone()->getName(),
+			'end_atom' => $end->getDateTime()->format(\DateTime::ATOM),
+			'end_is_floating' => $end->isFloating(),
+			'end_timezone' => $end->getDateTime()->getTimezone()->getName(),
+		];
+	}
 }
diff --git a/apps/dav/lib/CalDAV/Reminder/NotificationProviderManager.php b/apps/dav/lib/CalDAV/Reminder/NotificationProviderManager.php
index 0a2579aedfb..3d54970562d 100644
--- a/apps/dav/lib/CalDAV/Reminder/NotificationProviderManager.php
+++ b/apps/dav/lib/CalDAV/Reminder/NotificationProviderManager.php
@@ -1,6 +1,11 @@
 <?php
+declare(strict_types=1);
 /**
+ * @copyright Copyright (c) 2019, Thomas Citharel
+ * @copyright Copyright (c) 2019, Georg Ehrke
+ *
  * @author Thomas Citharel <tcit@tcit.fr>
+ * @author Georg Ehrke <oc.list@georgehrke.com>
  *
  * @license AGPL-3.0
  *
@@ -19,36 +24,55 @@
  */
 namespace OCA\DAV\CalDAV\Reminder;
 
-use OCA\DAV\CalDAV\Reminder\NotificationProvider\ProviderNotAvailableException;
-
+/**
+ * Class NotificationProviderManager
+ *
+ * @package OCA\DAV\CalDAV\Reminder
+ */
 class NotificationProviderManager {
 
-    /** @var array */
+    /** @var INotificationProvider[] */
     private $providers = [];
+
+	/**
+	 * Checks whether a provider for a given ACTION exists
+	 *
+	 * @param string $type
+	 * @return bool
+	 */
+	public function hasProvider(string $type):bool {
+		return (\in_array($type, ReminderService::REMINDER_TYPES, true)
+			&& isset($this->providers[$type]));
+	}
+
     /**
-     * @var string $type
-     * @return AbstractNotificationProvider
-     * @throws ProviderNotAvailableException
+	 * Get provider for a given ACTION
+	 *
+     * @param string $type
+     * @return INotificationProvider
+     * @throws NotificationProvider\ProviderNotAvailableException
      * @throws NotificationTypeDoesNotExistException
      */
-    public function getProvider(string $type):AbstractNotificationProvider {
+    public function getProvider(string $type):INotificationProvider {
         if (in_array($type, ReminderService::REMINDER_TYPES, true)) {
             if (isset($this->providers[$type])) {
                 return $this->providers[$type];
             }
-            throw new ProviderNotAvailableException($type);
+            throw new NotificationProvider\ProviderNotAvailableException($type);
         }
         throw new NotificationTypeDoesNotExistException($type);
     }
 
 	/**
+	 * Registers a new provider
+	 *
 	 * @param string $providerClassName
 	 * @throws \OCP\AppFramework\QueryException
 	 */
     public function registerProvider(string $providerClassName):void {
 		$provider = \OC::$server->query($providerClassName);
 
-		if (!$provider instanceof AbstractNotificationProvider) {
+		if (!$provider instanceof INotificationProvider) {
 			throw new \InvalidArgumentException('Invalid notification provider registered');
 		}
 
diff --git a/apps/dav/lib/CalDAV/Reminder/NotificationTypeDoesNotExistException.php b/apps/dav/lib/CalDAV/Reminder/NotificationTypeDoesNotExistException.php
index ae4ec3bd3b7..c060089785a 100644
--- a/apps/dav/lib/CalDAV/Reminder/NotificationTypeDoesNotExistException.php
+++ b/apps/dav/lib/CalDAV/Reminder/NotificationTypeDoesNotExistException.php
@@ -1,6 +1,7 @@
 <?php
+declare(strict_types=1);
 /**
- * @copyright Copyright (c) 2018 Thomas Citharel <tcit@tcit.fr>
+ * @copyright Copyright (c) 2019, Thomas Citharel
  *
  * @author Thomas Citharel <tcit@tcit.fr>
  *
diff --git a/apps/dav/lib/CalDAV/Reminder/Notifier.php b/apps/dav/lib/CalDAV/Reminder/Notifier.php
index 3718d5b29a6..4bad9841787 100644
--- a/apps/dav/lib/CalDAV/Reminder/Notifier.php
+++ b/apps/dav/lib/CalDAV/Reminder/Notifier.php
@@ -1,8 +1,11 @@
 <?php
+declare(strict_types=1);
 /**
- * @copyright Copyright (c) 2019 Thomas Citharel <tcit@tcit.fr>
+ * @copyright Copyright (c) 2019, Thomas Citharel
+ * @copyright Copyright (c) 2019, Georg Ehrke
  *
  * @author Thomas Citharel <tcit@tcit.fr>
+ * @author Georg Ehrke <oc.list@georgehrke.com>
  *
  * @license AGPL-3.0
  *
@@ -22,37 +25,47 @@
 
 namespace OCA\DAV\CalDAV\Reminder;
 
+use DateTime;
 use OCA\DAV\AppInfo\Application;
+use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\IL10N;
 use OCP\L10N\IFactory;
 use OCP\Notification\INotification;
 use OCP\Notification\INotifier;
 use OCP\IURLGenerator;
 
+/**
+ * Class Notifier
+ *
+ * @package OCA\DAV\CalDAV\Reminder
+ */
 class Notifier implements INotifier {
 
-	/** @var array */
-	public static $units = [
-        'y' => 'year',
-        'm' => 'month',
-        'd' => 'day',
-        'h' => 'hour',
-        'i' => 'minute',
-        's' => 'second',
-    ];
-
 	/** @var IFactory */
-	protected $factory;
+	private $l10nFactory;
 
 	/** @var IURLGenerator */
-	protected $urlGenerator;
+	private $urlGenerator;
 
 	/** @var IL10N */
-	protected $l;
+	private $l10n;
+
+	/** @var ITimeFactory */
+	private $timeFactory;
 
-	public function __construct(IFactory $factory, IURLGenerator $urlGenerator) {
-		$this->factory = $factory;
+	/**
+	 * Notifier constructor.
+	 *
+	 * @param IFactory $factory
+	 * @param IURLGenerator $urlGenerator
+	 * @param ITimeFactory $timeFactory
+	 */
+	public function __construct(IFactory $factory,
+								IURLGenerator $urlGenerator,
+								ITimeFactory $timeFactory) {
+		$this->l10nFactory = $factory;
 		$this->urlGenerator = $urlGenerator;
+		$this->timeFactory = $timeFactory;
 	}
 
 	/**
@@ -62,7 +75,7 @@ class Notifier implements INotifier {
 	 * @since 17.0.0
 	 */
 	public function getID():string {
-		return 'dav';
+		return Application::APP_ID;
 	}
 
 	/**
@@ -72,89 +85,236 @@ class Notifier implements INotifier {
 	 * @since 17.0.0
 	 */
 	public function getName():string {
-		return $this->factory->get('dav')->t('Calendar');
+		if ($this->l10n) {
+			return $this->l10n->t('Calendar');
+		}
+
+		return $this->l10nFactory->get('dav')->t('Calendar');
 	}
 
 	/**
+	 * Prepare sending the notification
+	 *
 	 * @param INotification $notification
 	 * @param string $languageCode The code of the language that should be used to prepare the notification
 	 * @return INotification
 	 * @throws \Exception
 	 */
-	public function prepare(INotification $notification, string $languageCode):INotification {
+	public function prepare(INotification $notification,
+							string $languageCode):INotification {
 		if ($notification->getApp() !== Application::APP_ID) {
 			throw new \InvalidArgumentException('Notification not from this app');
 		}
 
 		// Read the language from the notification
-		$this->l = $this->factory->get('dav', $languageCode);
+		$this->l10n = $this->l10nFactory->get('dav', $languageCode);
 
-		if ($notification->getSubject() === 'calendar_reminder') {
-			$subjectParameters = $notification->getSubjectParameters();
-			$notification->setParsedSubject($this->processEventTitle($subjectParameters));
+		// Handle notifier subjects
+		switch($notification->getSubject()) {
+			case 'calendar_reminder':
+				return $this->prepareReminderNotification($notification);
+
+			default:
+				throw new \InvalidArgumentException('Unknown subject');
 
-			$messageParameters = $notification->getMessageParameters();
-			$notification->setParsedMessage($this->processEventDescription($messageParameters));
-			$notification->setIcon($this->urlGenerator->getAbsoluteURL($this->urlGenerator->imagePath('core', 'places/calendar.svg')));
-			return $notification;
 		}
-		// Unknown subject => Unknown notification => throw
-		throw new \InvalidArgumentException('Unknown subject');
 	}
 
 	/**
-	 * @param array $event
-	 * @return string
-	 * @throws \Exception
+	 * @param INotification $notification
+	 * @return INotification
 	 */
-	private function processEventTitle(array $event):string {
-		$event_datetime = new \DateTime();
-		$event_datetime->setTimestamp($event['start']);
-		$now = new \DateTime();
-
-		$diff = $event_datetime->diff($now);
-
-		foreach (self::$units as $attribute => $unit) {
-            $count = $diff->$attribute;
-            if (0 !== $count) {
-                return $this->getPluralizedTitle($count, $diff->invert, $unit, $event['title']);
-            }
-        }
-        return '';
+	private function prepareReminderNotification(INotification $notification):INotification {
+		$imagePath = $this->urlGenerator->imagePath('core', 'places/calendar.svg');
+		$iconUrl = $this->urlGenerator->getAbsoluteURL($imagePath);
+		$notification->setIcon($iconUrl);
+
+		$this->prepareNotificationSubject($notification);
+		$this->prepareNotificationMessage($notification);
+
+		return $notification;
 	}
 
 	/**
+	 * Sets the notification subject based on the parameters set in PushProvider
 	 *
-	 * @param int $count
-	 * @param int $invert
-	 * @param string $unit
-	 * @param string $title
-	 * @return string
+	 * @param INotification $notification
 	 */
-	private function getPluralizedTitle(int $count, int $invert, string $unit, string $title):string {
-		if ($invert) {
-			return $this->l->n('%s (in one %s)', '%s (in %n %ss)', $count, [$title, $unit]);
+	private function prepareNotificationSubject(INotification $notification): void {
+		$parameters = $notification->getSubjectParameters();
+
+		$startTime = \DateTime::createFromFormat(\DateTimeInterface::ATOM, $parameters['start_atom']);
+		$now = $this->timeFactory->getDateTime();
+		$title = $this->getTitleFromParameters($parameters);
+
+		$diff = $startTime->diff($now);
+		if ($diff === false) {
+			return;
+		}
+
+		$components = [];
+		if ($diff->y) {
+			$components[] = $this->l10n->n('%n year', '%n years', $diff->y);
+		}
+		if ($diff->m) {
+			$components[] = $this->l10n->n('%n month', '%n months', $diff->m);
+		}
+		if ($diff->d) {
+			$components[] = $this->l10n->n('%n day', '%n days', $diff->d);
+		}
+		if ($diff->h) {
+			$components[] = $this->l10n->n('%n hour', '%n hours', $diff->h);
+		}
+		if ($diff->i) {
+			$components[] = $this->l10n->n('%n minute', '%n minutes', $diff->i);
+		}
+
+		// Limiting to the first three components to prevent
+		// the string from getting too long
+		$firstThreeComponents = array_slice($components, 0, 2);
+		$diffLabel = implode(', ', $firstThreeComponents);
+
+		if ($diff->invert) {
+			$title = $this->l10n->t('%s (in %s)', [$title, $diffLabel]);
+		} else {
+			$title = $this->l10n->t('%s (%s ago)', [$title, $diffLabel]);
 		}
-		// This should probably not show up
-		return $this->l->n('%s (one %s ago)', '%s (%n %ss ago)', $count, [$title, $unit]);
+
+		$notification->setParsedSubject($title);
 	}
 
 	/**
-	 * @param array $event
-	 * @return string
+	 * Sets the notification message based on the parameters set in PushProvider
+	 *
+	 * @param INotification $notification
 	 */
-	private function processEventDescription(array $event):string {
+	private function prepareNotificationMessage(INotification $notification): void {
+		$parameters = $notification->getMessageParameters();
+
 		$description = [
-			$this->l->t('Calendar: %s', $event['calendar']),
-			$this->l->t('Date: %s', $event['when']),
+			$this->l10n->t('Calendar: %s', $parameters['calendar_displayname']),
+			$this->l10n->t('Date: %s', $this->generateDateString($parameters)),
 		];
+		if ($parameters['description']) {
+			$description[] = $this->l10n->t('Description: %s', $parameters['description']);
+		}
+		if ($parameters['location']) {
+			$description[] = $this->l10n->t('Where: %s', $parameters['location']);
+		}
+
+		$message = implode("\r\n", $description);
+		$notification->setParsedMessage($message);
+	}
+
+	/**
+	 * @param array $parameters
+	 * @return string
+	 */
+	private function getTitleFromParameters(array $parameters):string {
+		return $parameters['title'] ?? $this->l10n->t('Untitled event');
+	}
 
-		if ($event['description']) {
-			$description[] = $this->l->t('Description: %s', $event['description']);
+	/**
+	 * @param array $parameters
+	 * @return string
+	 * @throws \Exception
+	 */
+	private function generateDateString(array $parameters):string {
+		$startDateTime = DateTime::createFromFormat(DATE_ATOM, $parameters['start_atom']);
+		$endDateTime = DateTime::createFromFormat(DATE_ATOM, $parameters['end_atom']);
+		$isAllDay = $parameters['all_day'];
+		$diff = $startDateTime->diff($endDateTime);
+
+		if ($isAllDay) {
+			// One day event
+			if ($diff->days === 1) {
+				return $this->getDateString($startDateTime);
+			}
+
+			return implode(' - ', [
+				$this->getDateString($startDateTime),
+				$this->getDateString($endDateTime),
+			]);
 		}
-		if ($event['location']) {
-			$description[] = $this->l->t('Where: %s', $event['location']);
+
+		$startTimezone = $endTimezone = null;
+		if (!$parameters['start_is_floating']) {
+			$startTimezone = $parameters['start_timezone'];
+			$endTimezone = $parameters['end_timezone'];
 		}
-		return implode('<br>', $description);
+
+		$localeStart = implode(', ', [
+			$this->getWeekDayName($startDateTime),
+			$this->getDateTimeString($startDateTime)
+		]);
+
+		// always show full date with timezone if timezones are different
+		if ($startTimezone !== $endTimezone) {
+			$localeEnd = implode(', ', [
+				$this->getWeekDayName($endDateTime),
+				$this->getDateTimeString($endDateTime)
+			]);
+
+			return $localeStart
+				. ' (' . $startTimezone . ') '
+				. ' - '
+				. $localeEnd
+				. ' (' . $endTimezone . ')';
+		}
+
+		// Show only the time if the day is the same
+		$localeEnd = $this->isDayEqual($startDateTime, $endDateTime)
+			? $this->getTimeString($endDateTime)
+			: implode(', ', [
+				$this->getWeekDayName($endDateTime),
+				$this->getDateTimeString($endDateTime)
+			]);
+
+		return $localeStart
+			. ' - '
+			. $localeEnd
+			. ' (' . $startTimezone . ')';
+	}
+
+	/**
+	 * @param DateTime $dtStart
+	 * @param DateTime $dtEnd
+	 * @return bool
+	 */
+	private function isDayEqual(DateTime $dtStart,
+								DateTime $dtEnd):bool {
+		return $dtStart->format('Y-m-d') === $dtEnd->format('Y-m-d');
+	}
+
+	/**
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getWeekDayName(DateTime $dt):string {
+		return $this->l10n->l('weekdayName', $dt, ['width' => 'abbreviated']);
+	}
+
+	/**
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getDateString(DateTime $dt):string {
+		return $this->l10n->l('date', $dt, ['width' => 'medium']);
+	}
+
+	/**
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getDateTimeString(DateTime $dt):string {
+		return $this->l10n->l('datetime', $dt, ['width' => 'medium|short']);
+	}
+
+	/**
+	 * @param DateTime $dt
+	 * @return string
+	 */
+	private function getTimeString(DateTime $dt):string {
+		return $this->l10n->l('time', $dt, ['width' => 'short']);
 	}
 }
diff --git a/apps/dav/lib/CalDAV/Reminder/ReminderService.php b/apps/dav/lib/CalDAV/Reminder/ReminderService.php
index ce6c846061e..ad428eef745 100644
--- a/apps/dav/lib/CalDAV/Reminder/ReminderService.php
+++ b/apps/dav/lib/CalDAV/Reminder/ReminderService.php
@@ -1,6 +1,11 @@
 <?php
+declare(strict_types=1);
 /**
+ * @copyright Copyright (c) 2019, Thomas Citharel
+ * @copyright Copyright (c) 2019, Georg Ehrke
+ *
  * @author Thomas Citharel <tcit@tcit.fr>
+ * @author Georg Ehrke <oc.list@georgehrke.com>
  *
  * @license AGPL-3.0
  *
@@ -19,14 +24,19 @@
  */
 namespace OCA\DAV\CalDAV\Reminder;
 
-use OC\User\NoUserException;
+use DateTimeImmutable;
+use OCA\DAV\CalDAV\CalDavBackend;
+use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\IGroup;
 use OCP\IGroupManager;
+use OCP\IUser;
 use OCP\IUserManager;
-use OCP\IUserSession;
 use Sabre\VObject;
 use Sabre\VObject\Component\VAlarm;
-use Sabre\VObject\Reader;
+use Sabre\VObject\Component\VEvent;
+use Sabre\VObject\ParseException;
+use Sabre\VObject\Recur\EventIterator;
+use Sabre\VObject\Recur\NoInstancesException;
 
 class ReminderService {
 
@@ -42,144 +52,710 @@ class ReminderService {
 	/** @var IGroupManager */
 	private $groupManager;
 
-	/** @var IUserSession */
-	private $userSession;
+	/** @var CalDavBackend */
+	private $caldavBackend;
+
+	/** @var ITimeFactory */
+	private $timeFactory;
 
 	public const REMINDER_TYPE_EMAIL = 'EMAIL';
 	public const REMINDER_TYPE_DISPLAY = 'DISPLAY';
 	public const REMINDER_TYPE_AUDIO = 'AUDIO';
 
+	/**
+	 * @var String[]
+	 *
+	 * Official RFC5545 reminder types
+	 */
 	public const REMINDER_TYPES = [
 		self::REMINDER_TYPE_EMAIL,
 		self::REMINDER_TYPE_DISPLAY,
 		self::REMINDER_TYPE_AUDIO
 	];
 
+	/**
+	 * ReminderService constructor.
+	 *
+	 * @param Backend $backend
+	 * @param NotificationProviderManager $notificationProviderManager
+	 * @param IUserManager $userManager
+	 * @param IGroupManager $groupManager
+	 * @param CalDavBackend $caldavBackend
+	 * @param ITimeFactory $timeFactory
+	 */
     public function __construct(Backend $backend,
                                 NotificationProviderManager $notificationProviderManager,
 								IUserManager $userManager,
 								IGroupManager $groupManager,
-								IUserSession $userSession) {
+								CalDavBackend $caldavBackend,
+								ITimeFactory $timeFactory) {
         $this->backend = $backend;
         $this->notificationProviderManager = $notificationProviderManager;
 		$this->userManager = $userManager;
 		$this->groupManager = $groupManager;
-		$this->userSession = $userSession;
+		$this->caldavBackend = $caldavBackend;
+		$this->timeFactory = $timeFactory;
     }
 
 	/**
 	 * Process reminders to activate
 	 *
-	 * @throws NoUserException
 	 * @throws NotificationProvider\ProviderNotAvailableException
 	 * @throws NotificationTypeDoesNotExistException
 	 */
     public function processReminders():void {
         $reminders = $this->backend->getRemindersToProcess();
 
-		foreach ($reminders as $reminder) {
-			$calendarData = Reader::read($reminder['calendardata']);
+        foreach($reminders as $reminder) {
+        	$vcalendar = $this->parseCalendarData($reminder['calendardata']);
+        	if (!$vcalendar) {
+				$this->backend->removeReminder($reminder['id']);
+				continue;
+			}
+
+			$vevent = $this->getVEventByRecurrenceId($vcalendar, $reminder['recurrence_id'], $reminder['is_recurrence_exception']);
+			if (!$vevent) {
+				$this->backend->removeReminder($reminder['id']);
+				continue;
+			}
 
-			$user = $this->userManager->get($reminder['uid']);
+			if ($this->wasEventCancelled($vevent)) {
+				$this->deleteOrProcessNext($reminder, $vevent);
+				continue;
+			}
+
+			if (!$this->notificationProviderManager->hasProvider($reminder['type'])) {
+				$this->deleteOrProcessNext($reminder, $vevent);
+				continue;
+			}
 
-            if ($user === null) {
-				throw new NoUserException('User not found for calendar');
+			$users = $this->getAllUsersWithWriteAccessToCalendar($reminder['calendar_id']);
+			$user = $this->getUserFromPrincipalURI($reminder['principaluri']);
+			if ($user) {
+				$users[] = $user;
 			}
 
 			$notificationProvider = $this->notificationProviderManager->getProvider($reminder['type']);
-			$notificationProvider->send($calendarData, $reminder['displayname'], $user);
-			$this->backend->removeReminder($reminder['id']);
+			$notificationProvider->send($vevent, $reminder['displayname'], $users);
+
+			$this->deleteOrProcessNext($reminder, $vevent);
 		}
     }
 
 	/**
-	 * Saves reminders when a calendar object with some alarms was created/updated/deleted
-	 *
 	 * @param string $action
-	 * @param array $calendarData
-	 * @param array $shares
 	 * @param array $objectData
-	 * @return void
 	 * @throws VObject\InvalidDataException
-	 * @throws NoUserException
 	 */
-	public function onTouchCalendarObject(string $action, array $calendarData, array $shares, array $objectData):void {
-		if (!isset($calendarData['principaluri'])) {
+	public function onTouchCalendarObject(string $action,
+										  array $objectData):void {
+		// We only support VEvents for now
+		if (strcasecmp($objectData['component'], 'vevent') !== 0) {
 			return;
 		}
 
-		// Always remove existing reminders for this event
-		$this->backend->cleanRemindersForEvent($objectData['calendarid'], $objectData['uri']);
+		switch($action) {
+			case '\OCA\DAV\CalDAV\CalDavBackend::createCalendarObject':
+				$this->onCalendarObjectCreate($objectData);
+				break;
+
+			case '\OCA\DAV\CalDAV\CalDavBackend::updateCalendarObject':
+				$this->onCalendarObjectEdit($objectData);
+				break;
 
-		/**
-		 * If we are deleting the event, no need to go further
-		 */
-		if ($action === '\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject') {
+			case '\OCA\DAV\CalDAV\CalDavBackend::deleteCalendarObject':
+				$this->onCalendarObjectDelete($objectData);
+				break;
+
+			default:
+				break;
+		}
+	}
+
+	/**
+	 * @param array $objectData
+	 */
+    private function onCalendarObjectCreate(array $objectData):void {
+		/** @var VObject\Component\VCalendar $vcalendar */
+		$vcalendar = $this->parseCalendarData($objectData['calendardata']);
+		if (!$vcalendar) {
 			return;
 		}
 
-		$user = $this->userSession->getUser();
+		$vevents = $this->getAllVEventsFromVCalendar($vcalendar);
+		if (count($vevents) === 0) {
+			return;
+		}
 
-		if ($user === null) {
-			throw new NoUserException('No user in session');
+		$uid = (string) $vevents[0]->UID;
+		$recurrenceExceptions = $this->getRecurrenceExceptionFromListOfVEvents($vevents);
+		$masterItem = $this->getMasterItemFromListOfVEvents($vevents);
+		$now = $this->timeFactory->getDateTime();
+		$isRecurring = $masterItem ? $this->isRecurring($masterItem) : false;
+
+		foreach($recurrenceExceptions as $recurrenceException) {
+			$eventHash = $this->getEventHash($recurrenceException);
+
+			foreach($recurrenceException->VALARM as $valarm) {
+				/** @var VAlarm $valarm */
+				$alarmHash = $this->getAlarmHash($valarm);
+				$triggerTime = $valarm->getEffectiveTriggerTime();
+				$diff = $now->diff($triggerTime);
+				if ($diff->invert === 1) {
+					continue;
+				}
+
+				$alarms = $this->getRemindersForVAlarm($valarm, $objectData,
+					$eventHash, $alarmHash, true, true);
+				$this->writeRemindersToDatabase($alarms);
+			}
 		}
 
-		$users = $this->getUsersForShares($shares);
+		if ($masterItem) {
+			$processedAlarms = [];
+			$masterAlarms = [];
+			$masterHash = $this->getEventHash($masterItem);
+
+			foreach($masterItem->VALARM as $valarm) {
+				$masterAlarms[] = $this->getAlarmHash($valarm);
+			}
 
-		$users[] = $user->getUID();
+			try {
+				$iterator = new EventIterator($vevents, $uid);
+			} catch (NoInstancesException $e) {
+				// This event is recurring, but it doesn't have a single
+				// instance. We are skipping this event from the output
+				// entirely.
+				return;
+			}
+
+			while($iterator->valid() && count($processedAlarms) < count($masterAlarms)) {
+				$event = $iterator->getEventObject();
+
+				// Recurrence-exceptions are handled separately, so just ignore them here
+				if (\in_array($event, $recurrenceExceptions, true)) {
+					$iterator->next();
+					continue;
+				}
+
+				foreach($event->VALARM as $valarm) {
+					/** @var VAlarm $valarm */
+					$alarmHash = $this->getAlarmHash($valarm);
+					if (\in_array($alarmHash, $processedAlarms, true)) {
+						continue;
+					}
 
-		$vobject = VObject\Reader::read($objectData['calendardata']);
+					if (!\in_array((string) $valarm->ACTION, self::REMINDER_TYPES, true)) {
+						// Action allows x-name, we don't insert reminders
+						// into the database if they are not standard
+						$processedAlarms[] = $alarmHash;
+						continue;
+					}
 
-		foreach ($vobject->VEVENT->VALARM as $alarm) {
-			if ($alarm instanceof VAlarm) {
-				$type = strtoupper($alarm->ACTION->getValue());
-				if (in_array($type, self::REMINDER_TYPES, true)) {
-					$time = $alarm->getEffectiveTriggerTime();
+					$triggerTime = $valarm->getEffectiveTriggerTime();
 
-					foreach ($users as $uid) {
-						$this->backend->insertReminder(
-							$uid,
-							$objectData['calendarid'],
-							$objectData['uri'],
-							$type,
-							$time->getTimestamp(),
-							$vobject->VEVENT->DTSTART->getDateTime()->getTimestamp());
+					// If effective trigger time is in the past
+					// just skip and generate for next event
+					$diff = $now->diff($triggerTime);
+					if ($diff->invert === 1) {
+						// If an absolute alarm is in the past,
+						// just add it to processedAlarms, so
+						// we don't extend till eternity
+						if (!$this->isAlarmRelative($valarm)) {
+							$processedAlarms[] = $alarmHash;
+						}
 
+						continue;
 					}
+
+					$alarms = $this->getRemindersForVAlarm($valarm, $objectData, $masterHash, $alarmHash, $isRecurring, false);
+					$this->writeRemindersToDatabase($alarms);
+					$processedAlarms[] = $alarmHash;
 				}
+
+				$iterator->next();
 			}
 		}
 	}
 
+	/**
+	 * @param array $objectData
+	 */
+	private function onCalendarObjectEdit(array $objectData):void {
+		// TODO - this can be vastly improved
+		//  - get cached reminders
+		//  - ...
+
+		$this->onCalendarObjectDelete($objectData);
+		$this->onCalendarObjectCreate($objectData);
+	}
 
 	/**
-	 * Get all users that have access to a given calendar
-	 *
-	 * @param array $shares
-	 * @return string[]
+	 * @param array $objectData
 	 */
-	private function getUsersForShares(array $shares):array {
-		$users = $groups = [];
+	private function onCalendarObjectDelete(array $objectData):void {
+		$this->backend->cleanRemindersForEvent((int) $objectData['id']);
+	}
+
+	/**
+	 * @param VAlarm $valarm
+	 * @param array $objectData
+	 * @param string|null $eventHash
+	 * @param string|null $alarmHash
+	 * @param bool $isRecurring
+	 * @param bool $isRecurrenceException
+	 * @return array
+	 */
+	private function getRemindersForVAlarm(VAlarm $valarm,
+										   array $objectData,
+										   string $eventHash=null,
+										   string $alarmHash=null,
+										   bool $isRecurring=false,
+										   bool $isRecurrenceException=false):array {
+		if ($eventHash === null) {
+			$eventHash = $this->getEventHash($valarm->parent);
+		}
+		if ($alarmHash === null) {
+			$alarmHash = $this->getAlarmHash($valarm);
+		}
+
+		$recurrenceId = $this->getEffectiveRecurrenceIdOfVEvent($valarm->parent);
+		$isRelative = $this->isAlarmRelative($valarm);
+		/** @var DateTimeImmutable $notificationDate */
+		$notificationDate = $valarm->getEffectiveTriggerTime();
+		$clonedNotificationDate = new \DateTime('now', $notificationDate->getTimezone());
+		$clonedNotificationDate->setTimestamp($notificationDate->getTimestamp());
+
+		$alarms = [];
+
+		$alarms[] = [
+			'calendar_id' => $objectData['calendarid'],
+			'object_id' => $objectData['id'],
+			'uid' => (string) $valarm->parent->UID,
+			'is_recurring' => $isRecurring,
+			'recurrence_id' => $recurrenceId,
+			'is_recurrence_exception' => $isRecurrenceException,
+			'event_hash' => $eventHash,
+			'alarm_hash' => $alarmHash,
+			'type' => (string) $valarm->ACTION,
+			'is_relative' => $isRelative,
+			'notification_date' => $notificationDate->getTimestamp(),
+			'is_repeat_based' => false,
+		];
+
+		$repeat = $valarm->REPEAT ? (int) $valarm->REPEAT : 0;
+		for($i = 0; $i < $repeat; $i++) {
+			if ($valarm->DURATION === null) {
+				continue;
+			}
+
+			$clonedNotificationDate->add($valarm->DURATION->getDateInterval());
+			$alarms[] = [
+				'calendar_id' => $objectData['calendarid'],
+				'object_id' => $objectData['id'],
+				'uid' => (string) $valarm->parent->UID,
+				'is_recurring' => $isRecurring,
+				'recurrence_id' => $recurrenceId,
+				'is_recurrence_exception' => $isRecurrenceException,
+				'event_hash' => $eventHash,
+				'alarm_hash' => $alarmHash,
+				'type' => (string) $valarm->ACTION,
+				'is_relative' => $isRelative,
+				'notification_date' => $clonedNotificationDate->getTimestamp(),
+				'is_repeat_based' => true,
+			];
+		}
+
+		return $alarms;
+	}
+
+	/**
+	 * @param array $reminders
+	 */
+	private function writeRemindersToDatabase(array $reminders): void {
+		foreach($reminders as $reminder) {
+			$this->backend->insertReminder(
+				(int) $reminder['calendar_id'],
+				(int) $reminder['object_id'],
+				$reminder['uid'],
+				$reminder['is_recurring'],
+				(int) $reminder['recurrence_id'],
+				$reminder['is_recurrence_exception'],
+				$reminder['event_hash'],
+				$reminder['alarm_hash'],
+				$reminder['type'],
+				$reminder['is_relative'],
+				(int) $reminder['notification_date'],
+				$reminder['is_repeat_based']
+			);
+		}
+	}
+
+	/**
+	 * @param array $reminder
+	 * @param VEvent $vevent
+	 */
+	private function deleteOrProcessNext(array $reminder,
+										 VObject\Component\VEvent $vevent):void {
+		if ($reminder['is_repeat_based'] ||
+			!$reminder['is_recurring'] ||
+			!$reminder['is_relative'] ||
+			$reminder['is_recurrence_exception']) {
+
+			$this->backend->removeReminder($reminder['id']);
+			return;
+		}
+
+		$vevents = $this->getAllVEventsFromVCalendar($vevent->parent);
+		$recurrenceExceptions = $this->getRecurrenceExceptionFromListOfVEvents($vevents);
+		$now = $this->timeFactory->getDateTime();
+
+		try {
+			$iterator = new EventIterator($vevents, $reminder['uid']);
+		} catch (NoInstancesException $e) {
+			// This event is recurring, but it doesn't have a single
+			// instance. We are skipping this event from the output
+			// entirely.
+			return;
+		}
+
+		while($iterator->valid()) {
+			$event = $iterator->getEventObject();
+
+			// Recurrence-exceptions are handled separately, so just ignore them here
+			if (\in_array($event, $recurrenceExceptions, true)) {
+				$iterator->next();
+				continue;
+			}
+
+			$recurrenceId = $this->getEffectiveRecurrenceIdOfVEvent($event);
+			if ($reminder['recurrence_id'] >= $recurrenceId) {
+				$iterator->next();
+				continue;
+			}
+
+			foreach($event->VALARM as $valarm) {
+				/** @var VAlarm $valarm */
+				$alarmHash = $this->getAlarmHash($valarm);
+				if ($alarmHash !== $reminder['alarm_hash']) {
+					continue;
+				}
+
+				$triggerTime = $valarm->getEffectiveTriggerTime();
+
+				// If effective trigger time is in the past
+				// just skip and generate for next event
+				$diff = $now->diff($triggerTime);
+				if ($diff->invert === 1) {
+					continue;
+				}
+
+				$this->backend->removeReminder($reminder['id']);
+				$alarms = $this->getRemindersForVAlarm($valarm, [
+					'calendarid' => $reminder['calendar_id'],
+					'id' => $reminder['object_id'],
+				], $reminder['event_hash'], $alarmHash, true, false);
+				$this->writeRemindersToDatabase($alarms);
+
+				// Abort generating reminders after creating one successfully
+				return;
+			}
+
+			$iterator->next();
+		}
+
+		$this->backend->removeReminder($reminder['id']);
+	}
+
+	/**
+	 * @param int $calendarId
+	 * @return IUser[]
+	 */
+	private function getAllUsersWithWriteAccessToCalendar(int $calendarId):array {
+		$shares = $this->caldavBackend->getShares($calendarId);
+
+		$users = [];
+		$userIds = [];
+		$groups = [];
 		foreach ($shares as $share) {
+			// Only consider writable shares
+			if ($share['readOnly']) {
+				continue;
+			}
+
 			$principal = explode('/', $share['{http://owncloud.org/ns}principal']);
 			if ($principal[1] === 'users') {
-				$users[] = $principal[2];
+				$user = $this->userManager->get($principal[2]);
+				if ($user) {
+					$users[] = $user;
+					$userIds[] = $principal[2];
+				}
 			} else if ($principal[1] === 'groups') {
 				$groups[] = $principal[2];
 			}
 		}
 
-		if (!empty($groups)) {
-			foreach ($groups as $gid) {
-				$group = $this->groupManager->get($gid);
-				if ($group instanceof IGroup) {
-					foreach ($group->getUsers() as $user) {
-						$users[] = $user->getUID();
+		foreach ($groups as $gid) {
+			$group = $this->groupManager->get($gid);
+			if ($group instanceof IGroup) {
+				foreach ($group->getUsers() as $user) {
+					if (!\in_array($user->getUID(), $userIds, true)) {
+						$users[] = $user;
+						$userIds[] = $user->getUID();
 					}
 				}
 			}
 		}
 
-		return array_unique($users);
+		return $users;
+	}
+
+	/**
+	 * Gets a hash of the event.
+	 * If the hash changes, we have to update all relative alarms.
+	 *
+	 * @param VEvent $vevent
+	 * @return string
+	 */
+	private function getEventHash(VEvent $vevent):string {
+		$properties = [
+			(string) $vevent->DTSTART->serialize(),
+		];
+
+		if ($vevent->DTEND) {
+			$properties[] = (string) $vevent->DTEND->serialize();
+		}
+		if ($vevent->DURATION) {
+			$properties[] = (string) $vevent->DURATION->serialize();
+		}
+		if ($vevent->{'RECURRENCE-ID'}) {
+			$properties[] = (string) $vevent->{'RECURRENCE-ID'}->serialize();
+		}
+		if ($vevent->RRULE) {
+			$properties[] = (string) $vevent->RRULE->serialize();
+		}
+		if ($vevent->EXDATE) {
+			$properties[] = (string) $vevent->EXDATE->serialize();
+		}
+		if ($vevent->RDATE) {
+			$properties[] = (string) $vevent->RDATE->serialize();
+		}
+
+		return md5(implode('::', $properties));
+	}
+
+	/**
+	 * Gets a hash of the alarm.
+	 * If the hash changes, we have to update oc_dav_reminders.
+	 *
+	 * @param VAlarm $valarm
+	 * @return string
+	 */
+	private function getAlarmHash(VAlarm $valarm):string {
+		$properties = [
+			(string) $valarm->ACTION->serialize(),
+			(string) $valarm->TRIGGER->serialize(),
+		];
+
+		if ($valarm->DURATION) {
+			$properties[] = (string) $valarm->DURATION->serialize();
+		}
+		if ($valarm->REPEAT) {
+			$properties[] = (string) $valarm->REPEAT->serialize();
+		}
+
+		return md5(implode('::', $properties));
+	}
+
+	/**
+	 * @param VObject\Component\VCalendar $vcalendar
+	 * @param int $recurrenceId
+	 * @param bool $isRecurrenceException
+	 * @return VEvent|null
+	 */
+	private function getVEventByRecurrenceId(VObject\Component\VCalendar $vcalendar,
+											 int $recurrenceId,
+											 bool $isRecurrenceException):?VEvent {
+		$vevents = $this->getAllVEventsFromVCalendar($vcalendar);
+		if (count($vevents) === 0) {
+			return null;
+		}
+
+		$uid = (string) $vevents[0]->UID;
+		$recurrenceExceptions = $this->getRecurrenceExceptionFromListOfVEvents($vevents);
+		$masterItem = $this->getMasterItemFromListOfVEvents($vevents);
+
+		// Handle recurrence-exceptions first, because recurrence-expansion is expensive
+		if ($isRecurrenceException) {
+			foreach($recurrenceExceptions as $recurrenceException) {
+				if ($this->getEffectiveRecurrenceIdOfVEvent($recurrenceException) === $recurrenceId) {
+					return $recurrenceException;
+				}
+			}
+
+			return null;
+		}
+
+		if ($masterItem) {
+			try {
+				$iterator = new EventIterator($vevents, $uid);
+			} catch (NoInstancesException $e) {
+				// This event is recurring, but it doesn't have a single
+				// instance. We are skipping this event from the output
+				// entirely.
+				return null;
+			}
+
+			while ($iterator->valid()) {
+				$event = $iterator->getEventObject();
+
+				// Recurrence-exceptions are handled separately, so just ignore them here
+				if (\in_array($event, $recurrenceExceptions, true)) {
+					$iterator->next();
+					continue;
+				}
+
+				if ($this->getEffectiveRecurrenceIdOfVEvent($event) === $recurrenceId) {
+					return $event;
+				}
+
+				$iterator->next();
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return string
+	 */
+	private function getStatusOfEvent(VEvent $vevent):string {
+		if ($vevent->STATUS) {
+			return (string) $vevent->STATUS;
+		}
+
+		// Doesn't say so in the standard,
+		// but we consider events without a status
+		// to be confirmed
+		return 'CONFIRMED';
+	}
+
+	/**
+	 * @param VObject\Component\VEvent $vevent
+	 * @return bool
+	 */
+	private function wasEventCancelled(VObject\Component\VEvent $vevent):bool {
+		return $this->getStatusOfEvent($vevent) === 'CANCELLED';
+	}
+
+	/**
+	 * @param string $calendarData
+	 * @return VObject\Component\VCalendar|null
+	 */
+	private function parseCalendarData(string $calendarData):?VObject\Component\VCalendar {
+		try {
+			return VObject\Reader::read($calendarData,
+				VObject\Reader::OPTION_FORGIVING);
+		} catch(ParseException $ex) {
+			return null;
+		}
+	}
+
+	/**
+	 * @param string $principalUri
+	 * @return IUser|null
+	 */
+	private function getUserFromPrincipalURI(string $principalUri):?IUser {
+		if (!$principalUri) {
+			return null;
+		}
+
+		if (strcasecmp($principalUri, 'principals/users/') !== 0) {
+			return null;
+		}
+
+		$userId = substr($principalUri, 17);
+		return $this->userManager->get($userId);
+	}
+
+	/**
+	 * @param VObject\Component\VCalendar $vcalendar
+	 * @return VObject\Component\VEvent[]
+	 */
+	private function getAllVEventsFromVCalendar(VObject\Component\VCalendar $vcalendar):array {
+		$vevents = [];
+
+		foreach($vcalendar->children() as $child) {
+			if (!($child instanceof VObject\Component)) {
+				continue;
+			}
+
+			if ($child->name !== 'VEVENT') {
+				continue;
+			}
+
+			$vevents[] = $child;
+		}
+
+		return $vevents;
+	}
+
+	/**
+	 * @param array $vevents
+	 * @return VObject\Component\VEvent[]
+	 */
+	private function getRecurrenceExceptionFromListOfVEvents(array $vevents):array {
+		return array_values(array_filter($vevents, function(VEvent $vevent) {
+			return $vevent->{'RECURRENCE-ID'} !== null;
+		}));
+	}
+
+	/**
+	 * @param array $vevents
+	 * @return VEvent|null
+	 */
+	private function getMasterItemFromListOfVEvents(array $vevents):?VEvent {
+		$elements = array_values(array_filter($vevents, function(VEvent $vevent) {
+			return $vevent->{'RECURRENCE-ID'} === null;
+		}));
+
+		if (count($elements) === 0) {
+			return null;
+		}
+		if (count($elements) > 1) {
+			throw new \TypeError('Multiple master objects');
+		}
+
+		return $elements[0];
+	}
+
+	/**
+	 * @param VAlarm $valarm
+	 * @return bool
+	 */
+	private function isAlarmRelative(VAlarm $valarm):bool {
+		$trigger = $valarm->TRIGGER;
+		return $trigger instanceof VObject\Property\ICalendar\Duration;
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return int
+	 */
+	private function getEffectiveRecurrenceIdOfVEvent(VEvent $vevent):int {
+		if (isset($vevent->{'RECURRENCE-ID'})) {
+			return $vevent->{'RECURRENCE-ID'}->getDateTime()->getTimestamp();
+		}
+
+		return $vevent->DTSTART->getDateTime()->getTimestamp();
+	}
+
+	/**
+	 * @param VEvent $vevent
+	 * @return bool
+	 */
+	private function isRecurring(VEvent $vevent):bool {
+		return isset($vevent->RRULE) || isset($vevent->RDATE);
 	}
 }
diff --git a/apps/dav/lib/Command/SendEventReminders.php b/apps/dav/lib/Command/SendEventReminders.php
index 02d8a287269..93477cb0f72 100644
--- a/apps/dav/lib/Command/SendEventReminders.php
+++ b/apps/dav/lib/Command/SendEventReminders.php
@@ -27,6 +27,11 @@ use Symfony\Component\Console\Command\Command;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
+/**
+ * Class SendEventReminders
+ *
+ * @package OCA\DAV\Command
+ */
 class SendEventReminders extends Command {
 
 	/** @var ReminderService */
@@ -35,10 +40,13 @@ class SendEventReminders extends Command {
 	/** @var IConfig */
 	protected $config;
 
-	public function __construct(string $name = null,
-								ReminderService $reminderService,
+	/**
+	 * @param ReminderService $reminderService
+	 * @param IConfig $config
+	 */
+	public function __construct(ReminderService $reminderService,
 								IConfig $config) {
-		parent::__construct($name);
+		parent::__construct();
 		$this->reminderService = $reminderService;
 		$this->config = $config;
 	}
diff --git a/apps/dav/lib/Migration/Version1004Date20170825134824.php b/apps/dav/lib/Migration/Version1004Date20170825134824.php
index 26855c2e23e..f3165a0fe3d 100644
--- a/apps/dav/lib/Migration/Version1004Date20170825134824.php
+++ b/apps/dav/lib/Migration/Version1004Date20170825134824.php
@@ -324,8 +324,7 @@ class Version1004Date20170825134824 extends SimpleMigrationStep {
 				'length' => 1,
 			]);
 			$table->addColumn('stripattachments', 'smallint', [
-				'notnull' => false,
-				'length' => 1,
+
 			]);
 			$table->addColumn('lastmodified', 'integer', [
 				'notnull' => false,
diff --git a/apps/dav/lib/Migration/Version1007Date20181005133326.php b/apps/dav/lib/Migration/Version1007Date20181005133326.php
deleted file mode 100644
index 1e4cce950ac..00000000000
--- a/apps/dav/lib/Migration/Version1007Date20181005133326.php
+++ /dev/null
@@ -1,82 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace OCA\DAV\Migration;
-
-use Closure;
-use OCP\DB\ISchemaWrapper;
-use OCP\Migration\SimpleMigrationStep;
-use OCP\Migration\IOutput;
-use Doctrine\DBAL\Types\Type;
-
-/**
- * Auto-generated migration step: Please modify to your needs!
- */
-class Version1007Date20181005133326 extends SimpleMigrationStep {
-
-	/**
-	 * @param IOutput $output
-	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
-	 * @param array $options
-	 */
-	public function preSchemaChange(IOutput $output, Closure $schemaClosure, array $options) {
-	}
-
-	/**
-	 * @param IOutput $output
-	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
-	 * @param array $options
-	 * @return null|ISchemaWrapper
-	 */
-	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options) {
-		/** @var ISchemaWrapper $schema */
-		$schema = $schemaClosure();
-
-		if (!$schema->hasTable('calendar_reminders')) {
-			$table = $schema->createTable('calendar_reminders');
-
-			$table->addColumn('id', Type::BIGINT, [
-				'autoincrement' => true,
-				'notnull' => true,
-				'length' => 11,
-				'unsigned' => true,
-			]);
-			$table->addColumn('uid', Type::STRING, [
-				'notnull' => true,
-				'length' => 255,
-			]);
-			$table->addColumn('calendarid', Type::BIGINT, [
-				'notnull' => false,
-				'length' => 11,
-			]);
-			$table->addColumn('objecturi', Type::STRING, [
-				'notnull' => true,
-				'length' => 255,
-			]);
-			$table->addColumn('type', Type::STRING, [
-				'notnull' => true,
-				'length' => 255,
-			]);
-			$table->addColumn('notificationdate', Type::DATETIME, [
-				'notnull' => false,
-			]);
-			$table->addColumn('eventstartdate', Type::DATETIME, [
-				'notnull' => false,
-			]);
-
-			$table->setPrimaryKey(['id']);
-			$table->addIndex(['calendarid'], 'calendar_reminder_calendars');
-
-			return $schema;
-		}
-	}
-
-	/**
-	 * @param IOutput $output
-	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
-	 * @param array $options
-	 */
-	public function postSchemaChange(IOutput $output, Closure $schemaClosure, array $options) {
-	}
-}
diff --git a/apps/dav/lib/Migration/Version1012Date20190808122342.php b/apps/dav/lib/Migration/Version1012Date20190808122342.php
new file mode 100644
index 00000000000..4aa768e705d
--- /dev/null
+++ b/apps/dav/lib/Migration/Version1012Date20190808122342.php
@@ -0,0 +1,116 @@
+<?php
+declare(strict_types=1);
+/**
+ * @copyright 2019, Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @author Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+namespace OCA\DAV\Migration;
+
+use Doctrine\DBAL\Types\Type;
+use OCP\DB\ISchemaWrapper;
+use OCP\Migration\SimpleMigrationStep;
+use OCP\Migration\IOutput;
+
+/**
+ * Auto-generated migration step: Please modify to your needs!
+ */
+class Version1012Date20190808122342 extends SimpleMigrationStep {
+
+	/**
+	 * @param IOutput $output
+	 * @param \Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 * @since 13.0.0
+	 */
+	public function changeSchema(IOutput $output,
+								 \Closure $schemaClosure,
+								 array $options):?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+		if (!$schema->hasTable('calendar_reminders')) {
+			$table = $schema->createTable('calendar_reminders');
+
+			$table->addColumn('id', Type::BIGINT, [
+				'autoincrement' => true,
+				'notnull' => true,
+				'length' => 11,
+				'unsigned' => true,
+			]);
+			$table->addColumn('calendar_id', Type::BIGINT, [
+				'notnull' => true,
+				'length' => 11,
+			]);
+			$table->addColumn('object_id', Type::BIGINT, [
+				'notnull' => true,
+				'length' => 11,
+			]);
+			$table->addColumn('is_recurring', Type::SMALLINT, [
+				'notnull' => true,
+				'length' => 1,
+			]);
+			$table->addColumn('uid', Type::STRING, [
+				'notnull' => true,
+				'length' => 255,
+			]);
+			$table->addColumn('recurrence_id', Type::BIGINT, [
+				'notnull' => false,
+				'length' => 11,
+				'unsigned' => true,
+			]);
+			$table->addColumn('is_recurrence_exception', Type::SMALLINT, [
+				'notnull' => true,
+				'length' => 1,
+			]);
+			$table->addColumn('event_hash', Type::STRING, [
+				'notnull' => true,
+				'length' => 255,
+			]);
+			$table->addColumn('alarm_hash', Type::STRING, [
+				'notnull' => true,
+				'length' => 255,
+			]);
+			$table->addColumn('type', Type::STRING, [
+				'notnull' => true,
+				'length' => 255,
+			]);
+			$table->addColumn('is_relative', Type::SMALLINT, [
+				'notnull' => true,
+				'length' => 1,
+			]);
+			$table->addColumn('notification_date', Type::BIGINT, [
+				'notnull' => true,
+				'length' => 11,
+				'unsigned' => true,
+			]);
+			$table->addColumn('is_repeat_based', Type::SMALLINT, [
+				'notnull' => true,
+				'length' => 1,
+			]);
+
+			$table->setPrimaryKey(['id']);
+			$table->addIndex(['object_id'], 'calendar_reminder_objid');
+			$table->addIndex(['uid', 'recurrence_id'], 'calendar_reminder_uidrec');
+
+			return $schema;
+		}
+	}
+}