added error handling for favorites

src/main/java/edu/ntnu/group8/stayfinder/controller/FolderFavoriteController.java

@@ -151,7 +151,7 @@ public class FolderFavoriteController {
    * @param folderId the ID of the folder
    * @param dto the data transfer object containing the hotel details
    * @param userDetails the authenticated user details
-   * @return the created favorite
+   * @return the created favorite or appropriate error response
    */
   @Operation(
     summary = "Add a hotel to favorites in a folder",
@@ -159,19 +159,30 @@ public class FolderFavoriteController {
   )
   @ApiResponses(value = {
     @ApiResponse(responseCode = "200", description = "Hotel added to favorites"),
+    @ApiResponse(responseCode = "400", description = "Hotel already in folder"),
     @ApiResponse(responseCode = "403", description = "Not your folder"),
     @ApiResponse(responseCode = "404", description = "Folder not found")
   })
   @PostMapping("/{folderId}/favorites")
-  public ResponseEntity<FavoriteDTO> addFavorite(
+  public ResponseEntity<?> addFavorite(
     @PathVariable int folderId,
     @RequestBody AddFavoriteDTO dto,
     @AuthenticationPrincipal AccessUserDetails userDetails) {
 
     validateFolderOwnership(folderId, userDetails.getUserId());
     dto.setFolderId(folderId);
-    FavoriteDTO favorite = folderFavoriteService.addFavorite(dto);
-    return ResponseEntity.ok(favorite);
+
+    try {
+      FavoriteDTO favorite = folderFavoriteService.addFavorite(dto);
+      return ResponseEntity.ok(favorite);
+    } catch (IllegalArgumentException ex) {
+      if (ex.getMessage().contains("already in the folder")) {
+        Map<String, String> response = new HashMap<>();
+        response.put("message", ex.getMessage());
+        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(response);
+      }
+      throw ex; // Re-throw other IllegalArgumentExceptions
+    }
   }
 
   /**

src/main/java/edu/ntnu/group8/stayfinder/repository/FavoriteRepository.java

 package edu.ntnu.group8.stayfinder.repository;
 
 import edu.ntnu.group8.stayfinder.entity.Folder;
+import edu.ntnu.group8.stayfinder.entity.Hotel;
 import java.util.List;
 import org.springframework.data.jpa.repository.JpaRepository;
 import edu.ntnu.group8.stayfinder.entity.Favorite;
@@ -29,4 +30,6 @@ public interface FavoriteRepository extends JpaRepository<Favorite, Integer> {
    * @return a list of Favorite entities associated with the given folder
    */
   List<Favorite> findByFolder(Folder folder);
+
+  boolean existsByFolderAndHotel(Folder folder, Hotel hotel);
 }

src/main/java/edu/ntnu/group8/stayfinder/service/FolderFavoriteService.java

@@ -14,6 +14,8 @@ import edu.ntnu.group8.stayfinder.repository.HotelRepository;
 import edu.ntnu.group8.stayfinder.dto.AddFavoriteDTO;
 import edu.ntnu.group8.stayfinder.repository.UserRepository;
 import java.util.stream.Collectors;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
@@ -34,6 +36,7 @@ public class FolderFavoriteService {
   private HotelRepository hotelRepository;
   @Autowired
   private UserRepository userRepository;
+  private Logger logger = LoggerFactory.getLogger(FolderFavoriteService.class);
 
 
   /**
@@ -62,10 +65,23 @@ public class FolderFavoriteService {
    */
   public FavoriteDTO addFavorite(AddFavoriteDTO dto) {
     Folder folder = folderRepository.findById(dto.getFolderId())
-      .orElseThrow(() -> new IllegalArgumentException("Folder not found"));
+      .orElseThrow(() -> {
+        logger.warn("Folder with ID {} not found", dto.getFolderId());
+        return new IllegalArgumentException("Folder not found");
+      });
 
     Hotel hotel = hotelRepository.findById(dto.getHotelId())
-      .orElseThrow(() -> new IllegalArgumentException("Hotel not found"));
+      .orElseThrow(() -> {
+        logger.warn("Hotel with ID {} not found", dto.getHotelId());
+        return new IllegalArgumentException("Hotel not found");
+      });
+
+    // Check if the hotel already exists in the folder
+    boolean hotelExists = favoriteRepository.existsByFolderAndHotel(folder, hotel);
+    if (hotelExists) {
+      logger.warn("Hotel with ID {} is already in folder with ID {}", dto.getHotelId(), dto.getFolderId());
+      throw new IllegalArgumentException("This hotel is already in the folder");
+    }
 
     Favorite favorite = new Favorite();
     favorite.setFolder(folder);