Fix RRULE BYDAY with multiple days only returning first day

src/IcalParser.php

@@ -215,19 +215,31 @@ public function parseRecurrences($event): array {
 		// This guard only works on WEEKLY, because the others have no fixed time interval
 		// There may still be a bug with the others
 		if (isset($event['RRULE']['INTERVAL']) && $recurring->getFreq() === "WEEKLY") {
+			$byDay = $recurring->getByDay();
+			$hasMultipleDays = $byDay !== false && is_array($byDay) && count($byDay) > 1;
 			$replacementList = [];
-
-			foreach($recurrenceTimestamps as $timestamp) {
+			
+			foreach ($recurrenceTimestamps as $timestamp) {
 				$tmp = new DateTime('now', $event['DTSTART']->getTimezone());
 				$tmp->setTimestamp($timestamp);
-
+				
 				$dayCount = $event['DTSTART']->diff($tmp)->format('%a');
-
-				if ($dayCount % ($event['RRULE']['INTERVAL'] * 7) == 0) {
-					$replacementList[] = $timestamp;
+
+				if ($hasMultipleDays) {
+					// For multiple days in BYDAY, check if the occurrence is in a valid week
+					// A valid week is one where the week number from DTSTART is divisible by INTERVAL
+					$weekCount = intdiv($dayCount, 7);
+					if ($weekCount % $event['RRULE']['INTERVAL'] == 0) {
+						$replacementList[] = $timestamp;
+					}
+				} else {
+					// For single day in BYDAY, the day must be exactly INTERVAL*7 days from DTSTART
+					if ($dayCount % ($event['RRULE']['INTERVAL'] * 7) == 0) {
+						$replacementList[] = $timestamp;
+					}
 				}
 			}
-
+			
 			$recurrenceTimestamps = $replacementList;
 		}
 

tests/cal/75_weekly_tuesday_thursday.ics

@@ -0,0 +1,19 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Test//Test//EN
+BEGIN:VEVENT
+DESCRIPTION:Test Event
+RRULE:FREQ=WEEKLY;UNTIL=20240430T220000Z;INTERVAL=1;BYDAY=TU,TH;WKST=MO
+UID:test-issue-75
+SUMMARY:Test Event TU,TH
+DTSTART;VALUE=DATE:20240326
+DTEND;VALUE=DATE:20240327
+CLASS:PUBLIC
+PRIORITY:5
+DTSTAMP:20240326T082436Z
+TRANSP:TRANSPARENT
+STATUS:CONFIRMED
+SEQUENCE:0
+LOCATION:
+END:VEVENT
+END:VCALENDAR

tests/events.recurring.phpt

@@ -257,4 +257,40 @@ test('Recurring instances bi-weekly', function () {
 	Assert::equal('31.1.2023 05:00:00', $events[0]['DTSTART']->format('j.n.Y H:i:s'));
 	Assert::equal('14.2.2023 05:00:00', $events[1]['DTSTART']->format('j.n.Y H:i:s'));
 	Assert::equal('28.2.2023 05:00:00', $events[2]['DTSTART']->format('j.n.Y H:i:s'));
+});
+
+test('Weekly recurring with Tuesday and Thursday', function () {
+// https://github.com/OzzyCzech/icalparser/issues/75
+	$cal = new IcalParser();
+
+	$cal->parseFile(__DIR__ . '/cal/75_weekly_tuesday_thursday.ics');
+	$events = $cal->getEvents()->sorted();
+
+// DTSTART;VALUE=DATE:20240326 (Tuesday, March 26, 2024)
+// RRULE:FREQ=WEEKLY;UNTIL=20240430T220000Z;INTERVAL=1;BYDAY=TU,TH;WKST=MO
+// Should return both Tuesdays and Thursdays: 6 Tuesdays + 5 Thursdays = 11 events
+	Assert::equal(11, $events->count());
+
+	// Week 1: Tue Mar 26, Thu Mar 28
+	Assert::equal('26.3.2024 00:00:00', $events[0]['DTSTART']->format('j.n.Y H:i:s'));
+	Assert::equal('28.3.2024 00:00:00', $events[1]['DTSTART']->format('j.n.Y H:i:s'));
+
+	// Week 2: Tue Apr 2, Thu Apr 4
+	Assert::equal('2.4.2024 00:00:00', $events[2]['DTSTART']->format('j.n.Y H:i:s'));
+	Assert::equal('4.4.2024 00:00:00', $events[3]['DTSTART']->format('j.n.Y H:i:s'));
+
+	// Week 3: Tue Apr 9, Thu Apr 11
+	Assert::equal('9.4.2024 00:00:00', $events[4]['DTSTART']->format('j.n.Y H:i:s'));
+	Assert::equal('11.4.2024 00:00:00', $events[5]['DTSTART']->format('j.n.Y H:i:s'));
+
+	// Week 4: Tue Apr 16, Thu Apr 18
+	Assert::equal('16.4.2024 00:00:00', $events[6]['DTSTART']->format('j.n.Y H:i:s'));
+	Assert::equal('18.4.2024 00:00:00', $events[7]['DTSTART']->format('j.n.Y H:i:s'));
+
+	// Week 5: Tue Apr 23, Thu Apr 25
+	Assert::equal('23.4.2024 00:00:00', $events[8]['DTSTART']->format('j.n.Y H:i:s'));
+	Assert::equal('25.4.2024 00:00:00', $events[9]['DTSTART']->format('j.n.Y H:i:s'));
+
+	// Week 6: Tue Apr 30 (last one before UNTIL)
+	Assert::equal('30.4.2024 00:00:00', $events[10]['DTSTART']->format('j.n.Y H:i:s'));
 });