fix: resync room selections with travel data before step 2

src/Service/BookingConfigurator.php

@@ -15,6 +15,7 @@ use App\Form\Model\BookingDto;
 use App\Form\Model\ParticipantDto;
 use App\Form\Model\RoomSelectionDto;
 use App\Form\Service\ServiceAgeEvaluator;
+use App\Model\RoomSelectionAdjustment;
 use Symfony\Component\DependencyInjection\Attribute\Autowire;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
@@ -91,6 +92,54 @@ class BookingConfigurator
         return $bookingCreateDto;
     }
 
+    /**
+     * Brings the room selections back in line with the rooms the travel currently offers.
+     *
+     * Room selections are built once when the booking session starts, while the Travel is re-fetched
+     * from BusPro on every request. A room that sells out or leaves a bookable status in between drops
+     * out of getAvailableRooms() and leaves a selection behind that points at a room that no longer
+     * exists; one that only loses part of its contingent leaves a quantity nothing else re-checks
+     * before the booking is submitted; and one that becomes bookable again has no selection at all.
+     * Rebuilding the selections from the current rooms, with the chosen quantities carried over and
+     * capped at what is left, keeps both sides in step.
+     *
+     * @return list<RoomSelectionAdjustment> The selections that had to give up quantity, in selection order
+     */
+    public function reconcileRoomSelections(BookingDto $bookingDto): array
+    {
+        $availableRooms = $bookingDto->travel->getAvailableRooms();
+
+        $adjustments = [];
+        $quantitiesByRoomId = [];
+
+        foreach ($bookingDto->roomSelections as $roomSelection) {
+            if (null === $roomSelection->id) {
+                continue;
+            }
+
+            $requestedQuantity = $roomSelection->quantity ?? 0;
+            $bookableQuantity = min($requestedQuantity, $availableRooms[$roomSelection->id]->available ?? 0);
+
+            $quantitiesByRoomId[$roomSelection->id] = $bookableQuantity;
+
+            if (0 < $requestedQuantity && $bookableQuantity < $requestedQuantity) {
+                $adjustments[] = new RoomSelectionAdjustment(
+                    $roomSelection->id,
+                    $roomSelection->label,
+                    $requestedQuantity,
+                    $bookableQuantity
+                );
+            }
+        }
+
+        $bookingDto->roomSelections = array_map(
+            fn (Room $room) => $this->createRoomSelection($room, $quantitiesByRoomId),
+            $availableRooms
+        );
+
+        return $adjustments;
+    }
+
     /**
      * Creates a room selection DTO from room data and quantities.
      *