[locationinfo] Work around HisInOne returning incomplete iCal files

While the HisInOne help text says:

Die Permalinks zu Raumbelegungsplänen und Veranstaltungen enthalten den
Semesterbezug (currentTimeId oder periodId). Bei Bedarf entfernen Sie
diese Einschränkung inklusive "&" vorne und aller Zeichen dahinter.

This is evidently not true. Requesting the iCal URL without the periodId
leaves out random courses/events/lectures, and event requesting with the
current periodId might not give you the full results as displayed by the
web interface. Add crude brute-force approach that will request multiple
periodIds and merge all the lectures found.

3 files changed, 81 insertions, 13 deletions

diff --git a/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php b/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php
index 9128288d..92113f76 100644
--- a/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php
+++ b/modules-available/locationinfo/inc/coursebackend/coursebackend_hisinone.inc.php
@@ -58,13 +58,76 @@ class CourseBackend_HisInOne extends ICalCourseBackend
 		// Unfortunately HisInOne returns an internal server error if you pass an invalid roomId.
 		// So we just try a bunch and see if anything works. Even if this fails, using
 		// the backend should work, given the URL is actually correct.
-		foreach ([60, 100, 5, 10, 50, 110, 200, 210, 250, 300, 333, 500, 1000, 2000] as $roomId) {
-			if ($this->downloadIcal($roomId, 60) !== null)
+		foreach ([60, 100, 5, 10, 11, 12, 13, 14, 15, 50, 110, 200, 210, 250, 300, 333, 500, 1000, 2000] as $roomId) {
+			// Use parent as we don't care about the periodId shenanigans
+			if (parent::downloadIcal((string)$roomId, time() + 60) !== null)
 				return true;
 		}
 		return false;
 	}
 
+	protected function downloadIcal(string $roomId, ?int $deadline, ?string $appendToUrl = null, ?bool $limitRange = true): ?array
+	{
+		$events = parent::downloadIcal($roomId, $deadline, null, false);
+		if (empty($events))
+			return $events;
+		$periodIds = [];
+		$finalEvents = [];
+		$dtStart = strtotime('-7 days');
+		$dtEnd = strtotime('+7 days');
+		foreach ($events as $event) {
+			if (isset($event->url) && preg_match('/[&?]periodId=([0-9]+)(&|$)/', $event->url, $out)) {
+				// Collect periodIds from URLs to find more lectures. While the HisInOne help says that the periodId
+				// parameter can simply be removed, in practice that means some lectures that take place even on the
+				// current day or week might not be returned in the resulting ical file, unless you pass the proper
+				// current periodId. Since there is no API or similar that reliably returns the current periodId,
+				// we just collect all the periodIds we find in the original ical file, and re-query with each of
+				// those appended to the URL, and merge the final result.
+				// Also, some courses seem to be assigned to past semesters, i.e. as of writing we have July 2025,
+				// but there is a lecture that won't be returned in the iCal data unless we make a request for
+				// the periodId corresponding to summer term 2024 (!)
+				$periodId = (int)$out[1];
+				for ($i = min($periodId - 3, 1); $i <= $periodId + 3; $i++) {
+					$periodIds[$i] = $i;
+				}
+			}
+			if (strtotime($event->dtstart) > $dtEnd || strtotime($event->dtend) < $dtStart)
+				continue;
+			$finalEvents[$this->hash($event)] = $event;
+		}
+		// Now re-query with all the periodIds we found
+		$dupCheck = [];
+		while (($periodId = array_pop($periodIds)) !== null) {
+			if (isset($dupCheck[$periodId]))
+				continue;
+			if ($deadline !== null && $deadline - time() <= 1)
+				break;
+			$dupCheck[$periodId] = true;
+			$events = parent::downloadIcal($roomId, $deadline, '&periodId=' . $periodId);
+			if (empty($events))
+				continue;
+			foreach ($events as $event) {
+				$finalEvents[$this->hash($event)] = $event;
+				// Collect more periodIds
+				if (isset($event->url) && preg_match('/[&?]periodId=([0-9]+)(&|$)/', $event->url, $out)) {
+					$periodId = (int)$out[1];
+					for ($i = min($periodId - 3, 1); $i <= $periodId + 3; $i++) {
+						$periodIds[$i] = $i;
+					}
+				}
+			}
+			if (count($dupCheck) > 5)
+				break;
+		}
+		$this->addError("Queried periodIds for $roomId:" . implode(',', array_keys($dupCheck)), false);
+		return array_values($finalEvents);
+	}
+
+	private function hash(ICalEvent $event): string
+	{
+		return md5($event->dtstart . $event->dtend . ($event->uid ?? $event->summary));
+	}
+
 	public function getCacheTime(): int
 	{
 		return 30 * 60;
diff --git a/modules-available/locationinfo/inc/coursebackend/coursebackend_ical.inc.php b/modules-available/locationinfo/inc/coursebackend/coursebackend_ical.inc.php
index 37d9d9d8..dbe53326 100644
--- a/modules-available/locationinfo/inc/coursebackend/coursebackend_ical.inc.php
+++ b/modules-available/locationinfo/inc/coursebackend/coursebackend_ical.inc.php
@@ -15,7 +15,7 @@ class CourseBackend_ICal extends ICalCourseBackend
 
 		$this->init($data['baseUrl'], $data['verifyCert'], $data['verifyHostname'], $data['authMethod'],
 			$data['user'], $data['pass']);
-		$this->testId = $data['testId'];
+		$this->testId = (string)$data['testId'];
 
 		return true;
 	}
@@ -39,7 +39,7 @@ class CourseBackend_ICal extends ICalCourseBackend
 			return false;
 		if (empty($this->testId))
 			return true;
-		return ($this->downloadIcal($this->testId, 60) !== null);
+		return ($this->downloadIcal($this->testId, time() + 60) !== null);
 	}
 
 	public function getCacheTime(): int
diff --git a/modules-available/locationinfo/inc/icalcoursebackend.inc.php b/modules-available/locationinfo/inc/icalcoursebackend.inc.php
index 6d9bbeef..de7ddb00 100644
--- a/modules-available/locationinfo/inc/icalcoursebackend.inc.php
+++ b/modules-available/locationinfo/inc/icalcoursebackend.inc.php
@@ -34,17 +34,21 @@ abstract class ICalCourseBackend extends CourseBackend
 	}
 
 	/**
-	 * @param string $roomId room id
-	 * @param callable $errorFunc
-	 * @return ICalEvent[]|null all events for this room in the range -7 days to +7 days, or NULL on error
+	 * Downloads iCal data for a specified room ID with optional deadline and URL appendage.
+	 *
+	 * @param string $roomId The ID of the room for which iCal data is to be downloaded.
+	 * @param ?int $deadline Optional deadline timestamp for the download operation.
+	 * @param ?string $appendToUrl Optional appendage to the URL used for the download.
+	 *
+	 * @return ?ICalEvent[] An array of iCal events if successful, or null on failure.
 	 */
-	protected function downloadIcal(string $roomId, int $timeout): ?array
+	protected function downloadIcal(string $roomId, ?int $deadline, ?string $appendToUrl = null, ?bool $limitRange = true): ?array
 	{
 		if (!$this->isOK())
 			return null;
 
 		try {
-			$ical = new ICalParser(['filterDaysBefore' => 7, 'filterDaysAfter' => 7]);
+			$ical = new ICalParser($limitRange ? ['filterDaysBefore' => 7, 'filterDaysAfter' => 7] : []);
 		} catch (Exception $e) {
 			$this->addError('Error instantiating ICalParser: ' . $e->getMessage(), true);
 			return null;
@@ -54,6 +58,8 @@ abstract class ICalCourseBackend extends CourseBackend
 			$this->curlHandle = curl_init();
 		}
 
+		$timeout = ($deadline ?? PHP_INT_MAX) - time();
+
 		$options = [
 			CURLOPT_WRITEFUNCTION => function ($ch, $data) use ($ical) {
 				$ical->feedData($data);
@@ -62,7 +68,7 @@ abstract class ICalCourseBackend extends CourseBackend
 			CURLOPT_FOLLOWLOCATION => true,
 			CURLOPT_SSL_VERIFYHOST => $this->verifyHostname ? 2 : 0,
 			CURLOPT_SSL_VERIFYPEER => $this->verifyCert ? 1 : 0,
-			CURLOPT_URL => str_replace('%ID%', $roomId, $this->location),
+			CURLOPT_URL => str_replace('%ID%', $roomId, $this->location . ($appendToUrl ?? '')),
 			CURLOPT_TIMEOUT => min(60, $timeout),
 			CURLOPT_CONNECTTIMEOUT => 4,
 		];
@@ -97,10 +103,9 @@ abstract class ICalCourseBackend extends CourseBackend
 		}
 		$tTables = [];
 		foreach ($requestedRoomIds as $roomId) {
-			$timeout = ($deadline ?? PHP_INT_MAX) - time();
-			if ($timeout <= 1)
+			if ($deadline !== null && $deadline - time() <= 1)
 				break;
-			$data = $this->downloadIcal($roomId, $timeout);
+			$data = $this->downloadIcal($roomId, $deadline);
 			if ($data === null) {
 				$this->addError("Downloading ical for $roomId failed", false);
 				continue;