@RestController
@RequestMapping("/api/users")
@CrossOrigin(origins = "http://localhost:3000")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping
    public ResponseEntity<List<User>> getAllUsers() {
        List<User> users = userService.findAll();
        return ResponseEntity.ok(users);
    }

    @GetMapping("/{id}")
    public ResponseEntity<User> getUserById(@PathVariable Long id) {
        Optional<User> user = userService.findById(id);
        return user.map(ResponseEntity::ok)
                  .orElse(ResponseEntity.notFound().build());
    }

    @PostMapping
    public ResponseEntity<User> createUser(@Valid @RequestBody User user) {
        User savedUser = userService.save(user);
        return ResponseEntity.status(HttpStatus.CREATED).body(savedUser);
    }
}

@Service
@Transactional
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public List<User> findAll() {
        return userRepository.findAll();
    }

    public Optional<User> findById(Long id) {
        return userRepository.findById(id);
    }

    public User save(User user) {
        user.setCreatedAt(LocalDateTime.now());
        return userRepository.save(user);
    }

    public void deleteById(Long id) {
        userRepository.deleteById(id);
    }

    public List<User> findByEmail(String email) {
        return userRepository.findByEmailContainingIgnoreCase(email);
    }
}

@ControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(UserNotFoundException.class)
    public ResponseEntity<ErrorResponse> handleUserNotFound(UserNotFoundException ex) {
        ErrorResponse error = new ErrorResponse(
            HttpStatus.NOT_FOUND.value(),
            ex.getMessage(),
            System.currentTimeMillis()
        );
        return ResponseEntity.status(HttpStatus.NOT_FOUND).body(error);
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ErrorResponse> handleValidationErrors(MethodArgumentNotValidException ex) {
        ErrorResponse error = new ErrorResponse(
            HttpStatus.BAD_REQUEST.value(),
            "Validation failed",
            System.currentTimeMillis()
        );
        return ResponseEntity.badRequest().body(error);
    }
}