fix: handle duplicate user email errors properly

backend/internal/api/handlers/core_handlers.go

@@ -2,6 +2,7 @@ package handlers
 
 import (
 	"encoding/json"
+	"errors"
 	"net"
 	"net/http"
 	"strconv"
@@ -353,7 +354,14 @@ func (h *CoreHandlers) CreateUser(w http.ResponseWriter, r *http.Request) {
 
 	resp, err := h.createUserUC.Execute(ctx, req, tenantID)
 	if err != nil {
-		http.Error(w, err.Error(), http.StatusInternalServerError)
+		statusCode := http.StatusInternalServerError
+		switch {
+		case errors.Is(err, user.ErrInvalidEmail):
+			statusCode = http.StatusBadRequest
+		case errors.Is(err, user.ErrEmailAlreadyExists):
+			statusCode = http.StatusConflict
+		}
+		http.Error(w, err.Error(), statusCode)
 		return
 	}
 

backend/internal/api/handlers/core_handlers_test.go

@@ -78,7 +78,7 @@ func TestRegisterCandidateHandler_Success(t *testing.T) {
 }
 
 func TestRegisterCandidateHandler_InvalidPayload(t *testing.T) {
-	coreHandlers := createTestCoreHandlers(t, nil, nil)
+	coreHandlers := createTestCoreHandlers(t, nil, nil, nil)
 
 	body := bytes.NewBufferString("{invalid json}")
 	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/register", body)
@@ -93,7 +93,7 @@ func TestRegisterCandidateHandler_InvalidPayload(t *testing.T) {
 }
 
 func TestRegisterCandidateHandler_MissingFields(t *testing.T) {
-	coreHandlers := createTestCoreHandlers(t, nil, nil)
+	coreHandlers := createTestCoreHandlers(t, nil, nil, nil)
 
 	testCases := []struct {
 		name     string
@@ -139,7 +139,7 @@ func TestRegisterCandidateHandler_MissingFields(t *testing.T) {
 }
 
 func TestLoginHandler_InvalidPayload(t *testing.T) {
-	coreHandlers := createTestCoreHandlers(t, nil, nil)
+	coreHandlers := createTestCoreHandlers(t, nil, nil, nil)
 
 	body := bytes.NewBufferString("{invalid}")
 	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/login", body)
@@ -171,7 +171,7 @@ func TestLoginHandler_Success(t *testing.T) {
 	// Real UseCase with Mocks
 	loginUC := auth.NewLoginUseCase(mockRepo, mockAuth)
 
-	coreHandlers := createTestCoreHandlers(t, nil, loginUC)
+	coreHandlers := createTestCoreHandlers(t, nil, loginUC, nil)
 
 	// Request
 	payload := dto.LoginRequest{Email: "john@example.com", Password: "123456"}
@@ -208,8 +208,63 @@ func TestLoginHandler_Success(t *testing.T) {
 	}
 }
 
+func TestCreateUserHandler_DuplicateEmailReturnsConflict(t *testing.T) {
+	mockRepo := &mockUserRepo{
+		findByEmailFunc: func(email string) (*entity.User, error) {
+			existing := entity.NewUser("existing-id", "tenant-1", "Existing User", email)
+			return existing, nil
+		},
+	}
+	mockAuth := &mockAuthService{}
+	createUserUC := user.NewCreateUserUseCase(mockRepo, mockAuth)
+	coreHandlers := createTestCoreHandlers(t, nil, nil, createUserUC)
+
+	payload := dto.CreateUserRequest{
+		Name:     "Duplicate User",
+		Email:    "duplicate@example.com",
+		Password: "123456",
+		Roles:    []string{"admin"},
+	}
+	body, _ := json.Marshal(payload)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/users", bytes.NewBuffer(body))
+	req.Header.Set("Content-Type", "application/json")
+	req = req.WithContext(context.WithValue(req.Context(), middleware.ContextRoles, []string{"superadmin"}))
+	rec := httptest.NewRecorder()
+
+	coreHandlers.CreateUser(rec, req)
+
+	if rec.Code != http.StatusConflict {
+		t.Errorf("Expected status %d, got %d. Body: %s", http.StatusConflict, rec.Code, rec.Body.String())
+	}
+}
+
+func TestCreateUserHandler_InvalidEmailReturnsBadRequest(t *testing.T) {
+	mockRepo := &mockUserRepo{}
+	mockAuth := &mockAuthService{}
+	createUserUC := user.NewCreateUserUseCase(mockRepo, mockAuth)
+	coreHandlers := createTestCoreHandlers(t, nil, nil, createUserUC)
+
+	payload := dto.CreateUserRequest{
+		Name:     "Invalid User",
+		Email:    "invalid-email",
+		Password: "123456",
+		Roles:    []string{"admin"},
+	}
+	body, _ := json.Marshal(payload)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/users", bytes.NewBuffer(body))
+	req.Header.Set("Content-Type", "application/json")
+	req = req.WithContext(context.WithValue(req.Context(), middleware.ContextRoles, []string{"superadmin"}))
+	rec := httptest.NewRecorder()
+
+	coreHandlers.CreateUser(rec, req)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Errorf("Expected status %d, got %d. Body: %s", http.StatusBadRequest, rec.Code, rec.Body.String())
+	}
+}
+
 // createTestCoreHandlers creates handlers with mocks and optional DB
-func createTestCoreHandlers(t *testing.T, db *sql.DB, loginUC *auth.LoginUseCase) *handlers.CoreHandlers {
+func createTestCoreHandlers(t *testing.T, db *sql.DB, loginUC *auth.LoginUseCase, createUserUC *user.CreateUserUseCase) *handlers.CoreHandlers {
 	t.Helper()
 
 	// Init services if DB provided
@@ -231,7 +286,7 @@ func createTestCoreHandlers(t *testing.T, db *sql.DB, loginUC *auth.LoginUseCase
 		loginUC,
 		(*auth.RegisterCandidateUseCase)(nil),
 		(*tenant.CreateCompanyUseCase)(nil),
-		(*user.CreateUserUseCase)(nil),
+		createUserUC,
 		(*user.ListUsersUseCase)(nil),
 		(*user.DeleteUserUseCase)(nil),
 		(*user.UpdateUserUseCase)(nil),
@@ -256,7 +311,7 @@ func TestCoreHandlers_ListNotifications(t *testing.T) {
 	defer db.Close()
 
 	// Setup Handlers with DB
-	handlers := createTestCoreHandlers(t, db, nil)
+	handlers := createTestCoreHandlers(t, db, nil, nil)
 
 	// User ID
 	userID := "user-123"
@@ -300,7 +355,7 @@ func TestCoreHandlers_Tickets(t *testing.T) {
 		}
 		defer db.Close()
 
-		handlers := createTestCoreHandlers(t, db, nil)
+		handlers := createTestCoreHandlers(t, db, nil, nil)
 
 		// Mock Insert: user_id, subject, priority
 		mock.ExpectQuery(regexp.QuoteMeta(`INSERT INTO tickets`)).
@@ -333,7 +388,7 @@ func TestCoreHandlers_Tickets(t *testing.T) {
 		}
 		defer db.Close()
 
-		handlers := createTestCoreHandlers(t, db, nil)
+		handlers := createTestCoreHandlers(t, db, nil, nil)
 
 		// Mock Select
 		mock.ExpectQuery(regexp.QuoteMeta(`SELECT id, user_id, subject, status, priority, created_at, updated_at FROM tickets`)).

backend/internal/core/usecases/user/create_user.go

@@ -11,6 +11,11 @@ import (
 	"github.com/rede5/gohorsejobs/backend/internal/utils"
 )
 
+var (
+	ErrInvalidEmail       = errors.New("email inválido")
+	ErrEmailAlreadyExists = errors.New("email já cadastrado")
+)
+
 // isValidEmail validates email format
 func isValidEmail(email string) bool {
 	emailRegex := regexp.MustCompile(`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`)
@@ -30,31 +35,24 @@ func NewCreateUserUseCase(uRepo ports.UserRepository, auth ports.AuthService) *C
 }
 
 func (uc *CreateUserUseCase) Execute(ctx context.Context, input dto.CreateUserRequest, currentTenantID string) (*dto.UserResponse, error) {
-	// 0. Sanitize inputs
 	sanitizer := utils.DefaultSanitizer()
 	input.Name = sanitizer.SanitizeName(input.Name)
 	input.Email = sanitizer.SanitizeEmail(input.Email)
 
-	// Validate email format
 	if input.Email == "" || !isValidEmail(input.Email) {
-		return nil, errors.New("email inválido")
+		return nil, ErrInvalidEmail
 	}
 
-	// 1. Validate Email Uniqueness (within tenant? or global?)
-	// Usually email is unique global or per tenant. Let's assume unique.
 	exists, _ := uc.userRepo.FindByEmail(ctx, input.Email)
 	if exists != nil {
-		return nil, errors.New("email já cadastrado")
+		return nil, ErrEmailAlreadyExists
 	}
 
-	// 2. Hash Password
 	hashed, err := uc.authService.HashPassword(input.Password)
 	if err != nil {
 		return nil, err
 	}
 
-	// 3. Create Entity
-	// Note: We enforce currentTenantID unless it's empty (SuperAdmin context) and input provides one.
 	tenantID := currentTenantID
 	if tenantID == "" && input.TenantID != nil {
 		tenantID = *input.TenantID
@@ -67,7 +65,6 @@ func (uc *CreateUserUseCase) Execute(ctx context.Context, input dto.CreateUserRe
 		user.Status = *input.Status
 	}
 
-	// Assign roles
 	for _, r := range input.Roles {
 		user.AssignRole(entity.Role{Name: r})
 	}
@@ -77,7 +74,6 @@ func (uc *CreateUserUseCase) Execute(ctx context.Context, input dto.CreateUserRe
 		return nil, err
 	}
 
-	// 4. Return DTO
 	roles := make([]string, len(saved.Roles))
 	for i, r := range saved.Roles {
 		roles[i] = r.Name

frontend/src/app/dashboard/users/page.tsx

@@ -130,7 +130,10 @@ export default function AdminUsersPage() {
             loadUsers(1)
         } catch (error) {
             console.error("[USER_FLOW] Error creating user:", error)
-            toast.error(t('admin.users.messages.create_error'))
+            const message = error instanceof Error && error.message
+                ? error.message
+                : t('admin.users.messages.create_error')
+            toast.error(message)
         } finally {
             setCreating(false)
         }

frontend/src/lib/__tests__/api.test.ts

@@ -211,16 +211,32 @@ describe('API Client', () => {
             ; (global.fetch as jest.Mock).mockResolvedValueOnce({
                 ok: false,
                 status: 401,
+                headers: { get: jest.fn().mockReturnValue('application/json') },
                 json: async () => ({ message: 'Unauthorized' }),
             })
 
             await expect(usersApi.list({ page: 1, limit: 10 })).rejects.toThrow('Unauthorized')
         })
 
+        it('should throw plain text error body when API does not return JSON', async () => {
+            ; (global.fetch as jest.Mock).mockResolvedValueOnce({
+                ok: false,
+                status: 409,
+                headers: { get: jest.fn().mockReturnValue('text/plain; charset=utf-8') },
+                text: async () => 'email já cadastrado',
+                json: async () => {
+                    throw new Error('Should not parse JSON for plain text responses')
+                },
+            })
+
+            await expect(usersApi.create({})).rejects.toThrow('email já cadastrado')
+        })
+
         it('should throw generic error when no message', async () => {
             ; (global.fetch as jest.Mock).mockResolvedValueOnce({
                 ok: false,
                 status: 500,
+                headers: { get: jest.fn().mockReturnValue('application/json') },
                 json: async () => ({}),
             })
 

frontend/src/lib/api.ts

@@ -15,6 +15,24 @@ function logCrudAction(action: string, entity: string, details?: any) {
     }
 }
 
+async function getErrorMessage(response: Response): Promise<string> {
+    const contentType = response.headers.get("content-type") || "";
+
+    if (contentType.includes("application/json")) {
+        const errorData = await response.json().catch(() => ({}));
+        if (typeof errorData?.message === "string" && errorData.message.trim()) {
+            return errorData.message;
+        }
+    } else {
+        const errorText = await response.text().catch(() => "");
+        if (errorText.trim()) {
+            return errorText;
+        }
+    }
+
+    return `Request failed with status ${response.status}`;
+}
+
 /**
  * Generic API Request Wrapper
  */
@@ -51,8 +69,7 @@ async function apiRequest<T>(endpoint: string, options: RequestInit = {}): Promi
             throw error;
         }
         
-        const errorData = await response.json().catch(() => ({}));
+        throw new Error(await getErrorMessage(response));
-        throw new Error(errorData.message || `Request failed with status ${response.status}`);
     }
 
     if (response.status === 204) {
@@ -840,8 +857,7 @@ async function backofficeRequest<T>(endpoint: string, options: RequestInit = {})
             (error as any).silent = true;
             throw error;
         }
-        const errorData = await response.json().catch(() => ({}));
+        throw new Error(await getErrorMessage(response));
-        throw new Error(errorData.message || `Request failed with status ${response.status}`);
     }
 
     if (response.status === 204) {