@Component
public class ProductHandler {

  @Autowired
  private ProductService productService;

  static Mono<ServerResponse> notFound = ServerResponse.notFound().build();
  private final Validator validator = new ProductValidator();

  public Mono<ServerResponse> getAllProducts(ServerRequest serverRequest) {
    return ServerResponse.ok()
       .contentType(MediaType.APPLICATION_JSON)
       .body(productService.getAllProducts(), Product.class);
  }

  public Mono<ServerResponse> getProduct(ServerRequest serverRequest) {
    String id = serverRequest.pathVariable("id");
    return productService.getProduct(id)
       .flatMap(p -> ServerResponse.ok()
           .contentType(MediaType.APPLICATION_JSON)
           .body(Mono.just(p), Product.class))
       .switchIfEmpty(ServerResponse.status(HttpStatus.NOT_FOUND)
           .contentType(MediaType.APPLICATION_JSON)
           .body(Mono.just(new ErrorResponse(404, "Product not found")), ErrorResponse.class));
  }

  public Mono<ServerResponse> createProduct(ServerRequest serverRequest) {
    Mono<Product> productToSave = serverRequest.bodyToMono(Product.class)
      .doOnNext(this::validate);

    return productToSave.flatMap(product ->
       ServerResponse.status(HttpStatus.CREATED)
         .contentType(MediaType.APPLICATION_JSON)
         .body(productService.save(product), Product.class));
  }

  private void validate(Product product) {
    Errors errors = new BeanPropertyBindingResult(product, "product");
    validator.validate(product, errors);
    if (errors.hasErrors()) {
      throw new ResponseStatusException(HttpStatus.BAD_REQUEST,
         errors.getAllErrors().toString());
    }
  }

  public Mono<ServerResponse> deleteProduct(ServerRequest serverRequest) {
    String id = serverRequest.pathVariable("id");
    return productService.deleteProduct(id)
      .flatMap(product -> ServerResponse.noContent().build());
  }

  public Mono<ServerResponse> updateProduct(ServerRequest serverRequest) {
    return productService.update(serverRequest.bodyToMono(Product.class)).flatMap(product ->
       ServerResponse.ok()
         .contentType(MediaType.APPLICATION_JSON)
         .body(fromObject(product)))
         .switchIfEmpty(notFound);
  }
}