handle vcalander documents with recurrence with exemptions or edits

when importing ics files from third party services (ex: google), long
running recurrence vcalander objects can contain numerous vevents
relating to past exemptions or edits.

these objects are handled incorrectly, leading to incorrect first and/or
last occurence dates from being inferred. as a result, a number of
imported events are not rendered in the calendar.

this PR makes use of EventIterator's constructor that takes in an array
of VEVENTS to properly handle these complex cases.

Also of note is that other parameter signatures of EventIterator's constructor,
will be deprecated, according to comments in sabre dav EventIterator.php

Signed-off-by: leith abdulla <online-nextcloud@eleith.com>

apps/dav/lib/CalDAV/CalDavBackend.php

@@ -2,6 +2,7 @@
 /**
  * @copyright Copyright (c) 2016, ownCloud, Inc.
  * @copyright Copyright (c) 2018 Georg Ehrke
+ * @copyright Copyright (c) 2020, leith abdulla (<online-nextcloud@eleith.com>)
  *
  * @author Christoph Wurst <christoph@winzerhof-wurst.at>
  * @author dartcafe <github@dartcafe.de>
@@ -2382,26 +2383,40 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	 */
 	public function getDenormalizedData($calendarData) {
 		$vObject = Reader::read($calendarData);
+		$vEvents = [];
 		$componentType = null;
 		$component = null;
 		$firstOccurrence = null;
 		$lastOccurrence = null;
 		$uid = null;
 		$classification = self::CLASSIFICATION_PUBLIC;
+		$hasDTSTART = false;
 		foreach ($vObject->getComponents() as $component) {
-			if ($component->name !== 'VTIMEZONE') {
-				$componentType = $component->name;
-				$uid = (string)$component->UID;
-				break;
+			if ($component->name!=='VTIMEZONE') {
+				// Finding all VEVENTs, and track them
+				if ($component->name === 'VEVENT') {
+					array_push($vEvents, $component);
+					if ($component->DTSTART) {
+						$hasDTSTART = true;
+					}
+				}
+				// Track first component type and uid
+				if ($uid === null) {
+					$componentType = $component->name;
+					$uid = (string)$component->UID;
+				}
 			}
 		}
 		if (!$componentType) {
 			throw new \Sabre\DAV\Exception\BadRequest('Calendar objects must have a VJOURNAL, VEVENT or VTODO component');
 		}
-		if ($componentType === 'VEVENT' && $component->DTSTART) {
-			$firstOccurrence = $component->DTSTART->getDateTime()->getTimeStamp();
+
+		if (count($vEvents) > 0 && $hasDTSTART) {
+			$component = $vEvents[0];
+
 			// Finding the last occurrence is a bit harder
-			if (!isset($component->RRULE)) {
+			if (!isset($component->RRULE) && count($vEvents) === 1) {
+				$firstOccurrence = $component->DTSTART->getDateTime()->getTimeStamp();
 				if (isset($component->DTEND)) {
 					$lastOccurrence = $component->DTEND->getDateTime()->getTimeStamp();
 				} elseif (isset($component->DURATION)) {
@@ -2416,8 +2431,9 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 					$lastOccurrence = $firstOccurrence;
 				}
 			} else {
-				$it = new EventIterator($vObject, (string)$component->UID);
+				$it = new EventIterator($vEvents);
 				$maxDate = new DateTime(self::MAX_DATE);
+				$firstOccurrence = $it->getDtStart()->getTimestamp();
 				if ($it->isInfinite()) {
 					$lastOccurrence = $maxDate->getTimestamp();
 				} else {

apps/dav/tests/unit/CalDAV/CalDavBackendTest.php

@@ -665,6 +665,8 @@ EOS;
 		return [
 			'first occurrence before unix epoch starts' => [0, 'firstOccurence', "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:413F269B-B51B-46B1-AFB6-40055C53A4DC\r\nDTSTAMP:20160309T095056Z\r\nDTSTART;VALUE=DATE:16040222\r\nDTEND;VALUE=DATE:16040223\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:SUMMARY\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"],
 			'no first occurrence because yearly' => [null, 'firstOccurence', "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject 4.1.1//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:413F269B-B51B-46B1-AFB6-40055C53A4DC\r\nDTSTAMP:20160309T095056Z\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:SUMMARY\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"],
+			'last occurrence is max when only last VEVENT in group is weekly' => [(new DateTime(CalDavBackend::MAX_DATE))->getTimestamp(), 'lastOccurence', "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject 4.3.0//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nDTSTART;TZID=America/Los_Angeles:20200812T103000\r\nDTEND;TZID=America/Los_Angeles:20200812T110000\r\nDTSTAMP:20200927T180638Z\r\nUID:asdfasdfasdf@google.com\r\nRECURRENCE-ID;TZID=America/Los_Angeles:20200811T123000\r\nCREATED:20200626T181848Z\r\nLAST-MODIFIED:20200922T192707Z\r\nSUMMARY:Weekly 1:1\r\nTRANSP:OPAQUE\r\nEND:VEVENT\r\nBEGIN:VEVENT\r\nDTSTART;TZID=America/Los_Angeles:20200728T123000\r\nDTEND;TZID=America/Los_Angeles:20200728T130000\r\nEXDATE;TZID=America/Los_Angeles:20200818T123000\r\nRRULE:FREQ=WEEKLY;BYDAY=TU\r\nDTSTAMP:20200927T180638Z\r\nUID:asdfasdfasdf@google.com\r\nCREATED:20200626T181848Z\r\nDESCRIPTION:Setting up recurring time on our calendars\r\nLAST-MODIFIED:20200922T192707Z\r\nSUMMARY:Weekly 1:1\r\nTRANSP:OPAQUE\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"],
+			'first occurrence is found when not first VEVENT in group' => [(new DateTime('2020-09-01T110000', new DateTimeZone("America/Los_Angeles")))->getTimestamp(), 'firstOccurence', "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject 4.3.0//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nDTSTART;TZID=America/Los_Angeles:20201013T110000\r\nDTEND;TZID=America/Los_Angeles:20201013T120000\r\nDTSTAMP:20200927T180638Z\r\nUID:asdf0000@google.com\r\nRECURRENCE-ID;TZID=America/Los_Angeles:20201013T110000\r\nCREATED:20160330T034726Z\r\nLAST-MODIFIED:20200925T042014Z\r\nSTATUS:CONFIRMED\r\nTRANSP:OPAQUE\r\nEND:VEVENT\r\nBEGIN:VEVENT\r\nDTSTART;TZID=America/Los_Angeles:20200901T110000\r\nDTEND;TZID=America/Los_Angeles:20200901T120000\r\nRRULE:FREQ=WEEKLY;BYDAY=TU\r\nEXDATE;TZID=America/Los_Angeles:20200922T110000\r\nEXDATE;TZID=America/Los_Angeles:20200915T110000\r\nEXDATE;TZID=America/Los_Angeles:20200908T110000\r\nDTSTAMP:20200927T180638Z\r\nUID:asdf0000@google.com\r\nCREATED:20160330T034726Z\r\nLAST-MODIFIED:20200915T162810Z\r\nSTATUS:CONFIRMED\r\nTRANSP:OPAQUE\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n"],
 			'CLASS:PRIVATE' => [CalDavBackend::CLASSIFICATION_PRIVATE, 'classification', "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//dmfs.org//mimedir.icalendar//EN\r\nBEGIN:VTIMEZONE\r\nTZID:Europe/Berlin\r\nX-LIC-LOCATION:Europe/Berlin\r\nBEGIN:DAYLIGHT\r\nTZOFFSETFROM:+0100\r\nTZOFFSETTO:+0200\r\nTZNAME:CEST\r\nDTSTART:19700329T020000\r\nRRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU\r\nEND:DAYLIGHT\r\nBEGIN:STANDARD\r\nTZOFFSETFROM:+0200\r\nTZOFFSETTO:+0100\r\nTZNAME:CET\r\nDTSTART:19701025T030000\r\nRRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU\r\nEND:STANDARD\r\nEND:VTIMEZONE\r\nBEGIN:VEVENT\r\nDTSTART;TZID=Europe/Berlin:20160419T130000\r\nSUMMARY:Test\r\nCLASS:PRIVATE\r\nTRANSP:OPAQUE\r\nSTATUS:CONFIRMED\r\nDTEND;TZID=Europe/Berlin:20160419T140000\r\nLAST-MODIFIED:20160419T074202Z\r\nDTSTAMP:20160419T074202Z\r\nCREATED:20160419T074202Z\r\nUID:2e468c48-7860-492e-bc52-92fa0daeeccf.1461051722310\r\nEND:VEVENT\r\nEND:VCALENDAR"],
 			'CLASS:PUBLIC' => [CalDavBackend::CLASSIFICATION_PUBLIC, 'classification', "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//dmfs.org//mimedir.icalendar//EN\r\nBEGIN:VTIMEZONE\r\nTZID:Europe/Berlin\r\nX-LIC-LOCATION:Europe/Berlin\r\nBEGIN:DAYLIGHT\r\nTZOFFSETFROM:+0100\r\nTZOFFSETTO:+0200\r\nTZNAME:CEST\r\nDTSTART:19700329T020000\r\nRRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU\r\nEND:DAYLIGHT\r\nBEGIN:STANDARD\r\nTZOFFSETFROM:+0200\r\nTZOFFSETTO:+0100\r\nTZNAME:CET\r\nDTSTART:19701025T030000\r\nRRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU\r\nEND:STANDARD\r\nEND:VTIMEZONE\r\nBEGIN:VEVENT\r\nDTSTART;TZID=Europe/Berlin:20160419T130000\r\nSUMMARY:Test\r\nCLASS:PUBLIC\r\nTRANSP:OPAQUE\r\nSTATUS:CONFIRMED\r\nDTEND;TZID=Europe/Berlin:20160419T140000\r\nLAST-MODIFIED:20160419T074202Z\r\nDTSTAMP:20160419T074202Z\r\nCREATED:20160419T074202Z\r\nUID:2e468c48-7860-492e-bc52-92fa0daeeccf.1461051722310\r\nEND:VEVENT\r\nEND:VCALENDAR"],
 			'CLASS:CONFIDENTIAL' => [CalDavBackend::CLASSIFICATION_CONFIDENTIAL, 'classification', "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//dmfs.org//mimedir.icalendar//EN\r\nBEGIN:VTIMEZONE\r\nTZID:Europe/Berlin\r\nX-LIC-LOCATION:Europe/Berlin\r\nBEGIN:DAYLIGHT\r\nTZOFFSETFROM:+0100\r\nTZOFFSETTO:+0200\r\nTZNAME:CEST\r\nDTSTART:19700329T020000\r\nRRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU\r\nEND:DAYLIGHT\r\nBEGIN:STANDARD\r\nTZOFFSETFROM:+0200\r\nTZOFFSETTO:+0100\r\nTZNAME:CET\r\nDTSTART:19701025T030000\r\nRRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU\r\nEND:STANDARD\r\nEND:VTIMEZONE\r\nBEGIN:VEVENT\r\nDTSTART;TZID=Europe/Berlin:20160419T130000\r\nSUMMARY:Test\r\nCLASS:CONFIDENTIAL\r\nTRANSP:OPAQUE\r\nSTATUS:CONFIRMED\r\nDTEND;TZID=Europe/Berlin:20160419T140000\r\nLAST-MODIFIED:20160419T074202Z\r\nDTSTAMP:20160419T074202Z\r\nCREATED:20160419T074202Z\r\nUID:2e468c48-7860-492e-bc52-92fa0daeeccf.1461051722310\r\nEND:VEVENT\r\nEND:VCALENDAR"],