fix: resync room selections with travel data before step 2

src/Controller/Booking/Create/Step2Controller.php

@@ -13,6 +13,7 @@ use App\Form\BookingCreateStep2Type;
 use App\Form\Model\BookingDto;
 use App\Form\Model\ParticipantDto;
 use App\Form\Model\RoomSelectionDto;
+use App\Model\RoomSelectionAdjustment;
 use App\Service\BookingConfigurator;
 use App\Service\BookingCreateContextFactory;
 use App\Service\BookingSessionManager;
@@ -66,6 +67,12 @@ class Step2Controller extends AbstractBookingCreateController
         // Enrich with fresh availability data
         $this->travelDataService->enrichWithFreshAvailabilities($bookingCreateDto->travel);
 
+        // Resync the room selections with the refreshed travel before any participant count is derived
+        // from them, and send the customer back to step 1 when a room they picked is gone.
+        if (null !== $redirect = $this->guardAgainstUnavailableRoomSelection($request, $bookingCreateDto)) {
+            return $redirect;
+        }
+
         // Ensure correct number of participants first, then prepopulate the applicant if needed.
         if (null !== $redirect = $this->guardAgainstEmptyParticipantList($bookingCreateDto)) {
             return $redirect;
@@ -120,6 +127,79 @@ class Step2Controller extends AbstractBookingCreateController
         return $this->render('booking/create/step_2.html.twig', $templateData);
     }
 
+    /**
+     * Sends the customer back to step 1 when the refreshed travel data no longer covers their rooms.
+     *
+     * Deriving the participant count from a room that has disappeared would silently fall back to a
+     * capacity of one and render too few participants, and a quantity the contingent no longer covers
+     * reaches the BusPro submit unchecked, because no later step re-reads room availability. The
+     * selections are resynced and saved before every exit, so step 1 and the neighbouring guard both
+     * see a collection that matches the rooms the template renders: leaving a stale entry behind would
+     * fail step 1's own validation on a field it never shows.
+     */
+    private function guardAgainstUnavailableRoomSelection(Request $request, BookingDto $bookingCreateDto): ?RedirectResponse
+    {
+        $adjustments = $this->bookingService->reconcileRoomSelections($bookingCreateDto);
+
+        $this->bookingSessionService->saveBookingDto($request, $bookingCreateDto, BookingDto::MODE_CREATE);
+
+        if ([] === $bookingCreateDto->travel->getAvailableRooms()) {
+            $this->handleApiError(
+                $this->logger,
+                'Travel has no bookable rooms left while a booking is in progress.',
+                $this->createRoomContext($bookingCreateDto, $adjustments),
+                'Für diese Reise sind leider keine Zimmer mehr verfügbar.'
+            );
+
+            return $this->redirectToRoute('app_booking_create_error');
+        }
+
+        if ([] === $adjustments) {
+            return null;
+        }
+
+        $hasDroppedRoom = false;
+        foreach ($adjustments as $adjustment) {
+            $hasDroppedRoom = $hasDroppedRoom || $adjustment->isDropped();
+        }
+
+        $this->handleApiError(
+            $this->logger,
+            'Room selection exceeds what the current travel data still offers.',
+            $this->createRoomContext($bookingCreateDto, $adjustments),
+            true === $hasDroppedRoom
+                ? 'Dein gewähltes Zimmer ist leider nicht mehr verfügbar. Bitte wähle dein Zimmer erneut.'
+                : 'Für dein gewähltes Zimmer sind nicht mehr genügend Plätze verfügbar. Wir haben deine Auswahl angepasst, bitte überprüfe sie.'
+        );
+
+        return $this->redirectToRoute('app_booking_create_step_1');
+    }
+
+    /**
+     * @param list<RoomSelectionAdjustment> $adjustments
+     *
+     * @return array<string, mixed>
+     */
+    private function createRoomContext(BookingDto $bookingCreateDto, array $adjustments): array
+    {
+        $rooms = [];
+        foreach ($adjustments as $adjustment) {
+            $rooms[] = [
+                'roomId' => $adjustment->roomId,
+                'label' => $adjustment->label,
+                'requestedQuantity' => $adjustment->requestedQuantity,
+                'bookableQuantity' => $adjustment->bookableQuantity,
+            ];
+        }
+
+        return [
+            'travelId' => $bookingCreateDto->travel->id,
+            'travelCode' => $bookingCreateDto->travel->code,
+            'hotelId' => $bookingCreateDto->hotelId,
+            'rooms' => $rooms,
+        ];
+    }
+
     /**
      * Rejects a room selection that resolves to no participants at all.
      *
@@ -190,7 +270,14 @@ class Step2Controller extends AbstractBookingCreateController
         $rooms = $travelData->getAvailableRooms();
 
         foreach ($roomSelections as $roomSelection) {
-            $room = $rooms[$roomSelection->id];
+            $room = $rooms[$roomSelection->id] ?? null;
+
+            if (null === $room) {
+                // Unreachable from index(), which reconciles the selections first. Kept so a future
+                // caller cannot silently fall back to a capacity of one and book too few people.
+                continue;
+            }
+
             $participantsCount += ($room->minPax ?? 1) * $roomSelection->quantity;
         }
 

src/Model/RoomSelectionAdjustment.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Model;
+
+/**
+ * A room selection the current travel data no longer supports in full.
+ *
+ * A room that disappeared altogether is the same case with nothing left to book, so it is reported
+ * as an adjustment down to zero rather than as a second kind of result.
+ */
+final readonly class RoomSelectionAdjustment
+{
+    public function __construct(
+        public int $roomId,
+        public ?string $label,
+        public int $requestedQuantity,
+        public int $bookableQuantity,
+    ) {
+    }
+
+    /**
+     * Whether the room is gone entirely rather than merely reduced.
+     */
+    public function isDropped(): bool
+    {
+        return 0 === $this->bookableQuantity;
+    }
+}

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.
      *