#19 - Merge timetable reservations

includes/Services/RsvReservationService.php

@@ -27,6 +27,9 @@ class RsvReservationService {
     }
 
     public function create(RsvReservation $reservation) {
+        $reservation->timetable_reservations =
+            $this->merge_adjacent($reservation->timetable_reservations);
+
         // Serialise the availability-check + insert per timetable so two
         // concurrent bookings for the last free slot can't both pass the
         // capacity check and oversell. Locks are taken in a stable order to
@@ -80,6 +83,48 @@ class RsvReservationService {
         return Db::prefix() . 'rsv_booking_' . $timetable_id;
     }
 
+    /**
+     * Collapse runs of touching reservations into single spans, so a sequence
+     * of back-to-back blocks is stored and notified as one booking.
+     *
+     * @param  list<RsvTimetableReservation> $timetable_reservations
+     * @return list<RsvTimetableReservation>
+     */
+    private function merge_adjacent(array $timetable_reservations): array {
+        $by_timetable = [];
+        foreach ($timetable_reservations as $tr) {
+            $by_timetable[$tr->timetable_id][] = $tr;
+        }
+
+        $merged = [];
+        foreach ($by_timetable as $group) {
+            usort($group, fn($a, $b) => $a->start_utc <=> $b->start_utc);
+
+            $current = null;
+            foreach ($group as $tr) {
+                if ($current !== null && $tr->start_utc <= $current->end_utc) {
+                    if ($tr->end_utc > $current->end_utc) {
+                        $current->end_utc = $tr->end_utc;
+                    }
+                    continue;
+                }
+
+                if ($current !== null) {
+                    $merged[] = $current;
+                }
+                $current = new RsvTimetableReservation(
+                    null, $tr->timetable_id, $tr->start_utc, $tr->end_utc
+                );
+            }
+
+            if ($current !== null) {
+                $merged[] = $current;
+            }
+        }
+
+        return $merged;
+    }
+
     /** Delete a reservation and its dependent timetable reservations and confirmations. */
     public function delete(int $id): void {
         $this->repo->delete($id);