// go code
type TestUser struct {
	Name             string  `validate:"required|minLen:2|maxLen:100" filter:"trim|lower"`
	Email            string  `validate:"required|email" filter:"lower"`
	OptionalString   *string `validate:"required|minLen:2|maxLen:100" filter:"trimPtr|lowerPtr"`
	TestOptionalUUID *uuid.UUID // **Problem LINE**
}

func TestValidateStruct(t *testing.T) {
	t.Parallel()
	validation.RegisterValidationFilters()
	user := TestUser{
		Name:           "  John Doe  ",
		Email:          "JOHNDOE@EXAMPLE.COM",
		OptionalString: pointer.Ref("    Optional String   "),
	}

	err := validation.ValidateStruct(&user)

	// Check if there's an error and it's as expected
	if err != nil {
		t.Errorf("Validation failed: %v", err)
	}

	// Check if the filters were applied correctly
	if user.Name != "john doe" || user.Email != "johndoe@example.com" {
		t.Errorf("Filters not applied correctly. Got Name: %s, Email: %s", user.Name, user.Email)
	}

	if pointer.Deref(user.OptionalString) != "optional string" {
		t.Errorf("Filters not applied correctly. Got OptionalString: %s", *user.OptionalString)
	}
}

func trimPointerString(val interface{}) interface{} {
	if strPtr, ok := val.(*string); ok && strPtr != nil {
		trimmed := strings.TrimSpace(*strPtr)
		return &trimmed
	}
	return val
}

func lowerPointerString(val interface{}) interface{} {
	if strPtr, ok := val.(*string); ok && strPtr != nil {
		lowered := strings.ToLower(*strPtr)
		return &lowered
	}
	return val
}

func RegisterValidationFilters() {
	validate.AddFilter("trimPtr", trimPointerString)
	validate.AddFilter("lowerPtr", lowerPointerString)
}

func ValidateStruct[T any](input *T) error {
	if input == nil {
		return nil
	}
	v := validate.Struct(input)
	if v.Validate() {
		return nil
	} else {
		return errorx.New(v.Errors.Error())
	}
}