feat: prefer discounted transportation services

addresses #869axbjbz

src/BusProNet/Model/Travel.php

@@ -48,7 +48,7 @@ class Travel
 
     /**
      * Travel booking status from BusProNet API.
-     * Possible values: 'Frei', 'Anfrage', 'Buchungsstop'
+     * Possible values: 'Frei', 'Anfrage', 'Buchungsstop'.
      */
     #[Groups(['api:single'])]
     public ?string $status = null;
@@ -153,8 +153,12 @@ class Travel
      * Filters transportation services based on travel direction and optionally
      * by availability. Services are sorted by subtype.
      *
+     * Note: PKW/CAR filtering based on booking context is NOT applied here.
+     * That filtering happens dynamically in ParticipantFieldOptionsProvider using
+     * per-booking availability calculations from ServiceAvailabilityCalculator.
+     *
      * @param string $direction       The travel direction to filter by
-     * @param bool   $filterAvailable Whether to include only available services
+     * @param bool   $filterAvailable Whether to include only available services (API availability)
      *
      * @return array<int, Service> The filtered and sorted transportation services
      */

src/Form/Service/ParticipantFieldOptionsProvider.php

@@ -349,7 +349,11 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
         // Outbound Transportation
         $this->fieldOptionProviders['transportationOutbound'] = fn (BookingDto $bookingDto, int $participantIndex, array $options = []) => [
             'label' => 'Hinfahrt',
-            'choices' => $bookingDto->travel->getTransportationServicesByDirection(DirectionMapper::OUTBOUND_TRAVEL),
+            'choices' => $this->filterTransportationChoices(
+                $bookingDto->travel->getTransportationServicesByDirection(DirectionMapper::OUTBOUND_TRAVEL),
+                $bookingDto,
+                $participantIndex
+            ),
             'choice_label' => fn (Service $service) => $this->formatTransportationServiceLabel($service),
             'choice_value' => 'id',
             'expanded' => true,
@@ -767,4 +771,81 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
             $travelPrice
         );
     }
+
+    /**
+     * Filters transportation choices to show only one PKW option based on per-booking availability.
+     *
+     * When both discounted and regular self-organized (PKW/CAR) options exist:
+     * - If discounted option has remaining availability within this booking, show only discounted
+     * - If discounted option is sold out within this booking, show only regular
+     * - This creates dynamic fallback: as participants select/deselect, availability updates in real-time
+     *
+     * Business logic: Prefer showing discounted options while they have availability, but automatically
+     * fall back to regular options when discounts are exhausted. This allows participants who initially
+     * got the discount to change their mind (e.g., select bus instead), making the discount available
+     * for others in the same booking session.
+     *
+     * @param array      $services         Transportation services from Travel model
+     * @param BookingDto $bookingDto       Current booking DTO with participant selections
+     * @param int        $participantIndex Current participant being processed
+     *
+     * @return array Filtered transportation choices with smart PKW option selection
+     */
+    private function filterTransportationChoices(array $services, BookingDto $bookingDto, int $participantIndex): array
+    {
+        // Only apply filtering in create mode
+        if (BookingDto::MODE_CREATE !== $bookingDto->getMode()) {
+            return $services;
+        }
+
+        // Separate PKW/CAR from other services (BUS, etc.)
+        $pkwServices = [];
+        $otherServices = [];
+
+        foreach ($services as $service) {
+            if (in_array($service->subType, ['PKW', 'CAR'], true)) {
+                $pkwServices[] = $service;
+            } else {
+                $otherServices[] = $service;
+            }
+        }
+
+        // If only one or no PKW service, no filtering needed
+        if (count($pkwServices) <= 1) {
+            return [...$otherServices, ...$pkwServices];
+        }
+
+        // Find discounted (negative price) and regular (zero/positive price) PKW options
+        $discountedPkw = null;
+        $regularPkw = null;
+
+        foreach ($pkwServices as $pkw) {
+            if (null !== $pkw->price && $pkw->price < 0) {
+                $discountedPkw = $pkw;
+            } else {
+                $regularPkw = $pkw;
+            }
+        }
+
+        // If we have both discounted and regular options, apply smart filtering
+        if (null !== $discountedPkw && null !== $regularPkw) {
+            // Check if discounted option is unavailable for this participant (per-booking availability)
+            $discountedIsUnavailable = $this->serviceAvailabilityCalculator->isServiceUnavailable(
+                $discountedPkw->id,
+                $bookingDto,
+                $participantIndex
+            );
+
+            if ($discountedIsUnavailable) {
+                // Discounted is sold out within this booking, show only regular
+                return [...$otherServices, $regularPkw];
+            } else {
+                // Discounted has availability, show only discounted (hide regular)
+                return [...$otherServices, $discountedPkw];
+            }
+        }
+
+        // Fallback: return all services if we don't have the expected discount/regular pair
+        return [...$otherServices, ...$pkwServices];
+    }
 }