restrict adoption pets

backend/src/main/java/com/petshop/backend/controller/DropdownController.java

@@ -52,7 +52,7 @@ public class DropdownController {
     @PreAuthorize("hasAnyRole('STAFF', 'ADMIN')")
     public ResponseEntity<List<DropdownOption>> getAdoptionPets() {
         return ResponseEntity.ok(
-                petRepository.findAllByPetStatusIgnoreCaseOrderByPetNameAsc("Available").stream()
+                petRepository.findAdoptablePetsOrderByPetNameAsc().stream()
                         .map(p -> new DropdownOption(p.getPetId(), p.getPetName()))
                         .collect(Collectors.toList())
         );

backend/src/main/java/com/petshop/backend/repository/PetRepository.java

@@ -15,6 +15,14 @@ import java.util.Optional;
 public interface PetRepository extends JpaRepository<Pet, Long> {
 
     List<Pet> findAllByPetStatusIgnoreCaseOrderByPetNameAsc(String petStatus);
+    @Query("SELECT p FROM Pet p " +
+           "WHERE LOWER(p.petStatus) = 'available' " +
+           "AND NOT EXISTS (" +
+           "    SELECT 1 FROM Adoption a " +
+           "    WHERE a.pet = p AND LOWER(a.adoptionStatus) = 'completed'" +
+           ") " +
+           "ORDER BY p.petName ASC")
+    List<Pet> findAdoptablePetsOrderByPetNameAsc();
     List<Pet> findAllByOwner_IdOrderByPetNameAsc(Long ownerId);
     Optional<Pet> findByIdAndOwner_Id(Long id, Long ownerId);
 

backend/src/main/java/com/petshop/backend/service/AdoptionService.java

@@ -80,7 +80,7 @@ public class AdoptionService {
                         .orElseThrow(() -> new ResourceNotFoundException("Store not found with id: " + request.getSourceStoreId()))
                 : null;
         String adoptionStatus = normalizeAdoptionStatus(request.getAdoptionStatus());
-        validatePetAvailability(pet, null);
+        validatePetAvailability(pet, null, null);
 
         Adoption adoption = new Adoption();
         adoption.setPet(pet);
@@ -111,7 +111,8 @@ public class AdoptionService {
                         .orElseThrow(() -> new ResourceNotFoundException("Store not found with id: " + request.getSourceStoreId()))
                 : null;
         String adoptionStatus = normalizeAdoptionStatus(request.getAdoptionStatus());
-        validatePetAvailability(pet, adoption.getAdoptionId());
+        Long currentPetId = adoption.getPet() != null ? adoption.getPet().getPetId() : null;
+        validatePetAvailability(pet, adoption.getAdoptionId(), currentPetId);
 
         adoption.setPet(pet);
         adoption.setCustomer(customer);
@@ -201,7 +202,8 @@ public class AdoptionService {
         throw new IllegalArgumentException("Adoption status must be Pending, Completed, or Cancelled");
     }
 
-    private void validatePetAvailability(Pet pet, Long adoptionId) {
+    private void validatePetAvailability(Pet pet, Long adoptionId, Long currentPetId) {
+        boolean samePetAsCurrentAdoption = currentPetId != null && currentPetId.equals(pet.getPetId());
         boolean adoptedElsewhere = adoptionId == null
                 ? adoptionRepository.existsByPet_IdAndAdoptionStatusIgnoreCase(pet.getPetId(), ADOPTION_STATUS_COMPLETED)
                 : adoptionRepository.existsByPet_IdAndAdoptionStatusIgnoreCaseAndAdoptionIdNot(pet.getPetId(), ADOPTION_STATUS_COMPLETED, adoptionId);
@@ -209,7 +211,7 @@ public class AdoptionService {
             throw new IllegalArgumentException("Selected pet has already been adopted");
         }
 
-        if (!PET_STATUS_AVAILABLE.equalsIgnoreCase(pet.getPetStatus()) && adoptionId == null) {
+        if (!samePetAsCurrentAdoption && !PET_STATUS_AVAILABLE.equalsIgnoreCase(pet.getPetStatus())) {
             throw new IllegalArgumentException("Selected pet is not available for adoption");
         }
     }

desktop/src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/AdoptionDialogController.java

@@ -74,6 +74,7 @@ public class AdoptionDialogController {
                 Platform.runLater(() -> {
                     if (pets != null) {
                         ObservableList<DropdownOption> petsObs = FXCollections.observableArrayList(pets);
+                        ensureSelectedPetOption(petsObs);
                         cbPet.setItems(petsObs);
                         applySelectedPet();
                     }
@@ -318,4 +319,17 @@ public class AdoptionDialogController {
         }
         return null;
     }
+
+    private void ensureSelectedPetOption(ObservableList<DropdownOption> options) {
+        if (selectedAdoption == null || selectedAdoption.getPetId() <= 0 || options == null) {
+            return;
+        }
+        DropdownOption existing = findOptionById(options, (long) selectedAdoption.getPetId());
+        if (existing == null) {
+            DropdownOption option = new DropdownOption();
+            option.setId((long) selectedAdoption.getPetId());
+            option.setLabel(selectedAdoption.getPetName());
+            options.add(0, option);
+        }
+    }
 }