feat: multi tenant support

backend/internal/web/handler/handler.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/go-chi/chi/v5"
+	"gorm.io/gorm"
 
 	"github.com/danyel/go-guess/backend/internal/database/repository"
 	"github.com/danyel/go-guess/backend/internal/eventbus"
@@ -24,6 +25,7 @@ import (
 )
 
 type Handler struct {
+	db           *gorm.DB
 	auth         service.IAuthService
 	jobs         service.IJobService
 	questions    service.IQuestionService
@@ -36,6 +38,7 @@ type Handler struct {
 }
 
 func New(
+	db *gorm.DB,
 	auth service.IAuthService,
 	jobs service.IJobService,
 	questions service.IQuestionService,
@@ -47,6 +50,7 @@ func New(
 	frontendURL string,
 ) *Handler {
 	return &Handler{
+		db:   db,
 		auth: auth, jobs: jobs, questions: questions, participants: participants,
 		invitations: invitations, maxUpload: maxUploadMB << 20,
 		users: users, interviews: interviews,
@@ -139,6 +143,10 @@ func (h *Handler) CreateJob(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusCreated, webmapper.JobToWeb(value))
 }
 
+func (h *Handler) Db() *gorm.DB {
+	return h.db
+}
+
 func (h *Handler) UpdateJob(w http.ResponseWriter, r *http.Request) {
 	var request webmodel.JobStatusRequest
 	if err := decodeJSON(r, &request); err != nil {

backend/internal/web/middleware/TenantSchemaMiddleware.go

@@ -0,0 +1,73 @@
+package middleware
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"regexp"
+
+	"gorm.io/gorm"
+)
+
+type contextKey string
+
+const TxKey contextKey = "tenant_db_tx"
+
+// Alphanumeric or underscores only to prevent SQL Injection in schema names
+var safeSchemaRegex = regexp.MustCompile(`^[a-zA-Z0-9_:-]+$`)
+
+// TenantSchemaMiddleware isolates database connections per request using PostgreSQL schemas
+func TenantSchemaMiddleware(db *gorm.DB) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			tenantID := r.Header.Get("X-Tenant-Id")
+			if tenantID == "" {
+				w.Header().Set("Content-Type", "application/json")
+				w.WriteHeader(http.StatusBadRequest)
+				_, _ = w.Write([]byte(`{"error": "Missing X-Tenant-Id header"}`))
+				return
+			}
+
+			// Validate schema name to guarantee safety against SQL injection
+			if !safeSchemaRegex.MatchString(tenantID) {
+				w.Header().Set("Content-Type", "application/json")
+				w.WriteHeader(http.StatusBadRequest)
+				_, _ = w.Write([]byte(`{"error": "Invalid characters in tenant ID"}`))
+				return
+			}
+
+			// Start a fresh transaction scoped exclusively to this HTTP request
+			tx := db.Begin()
+
+			// Set the local search_path for the duration of this transaction block
+			if err := tx.Exec(fmt.Sprintf("SET LOCAL search_path TO %s", tenantID)).Error; err != nil {
+				tx.Rollback()
+				w.Header().Set("Content-Type", "application/json")
+				w.WriteHeader(http.StatusInternalServerError)
+				_, _ = w.Write([]byte(`{"error": "Failed to resolve tenant storage isolation"}`))
+				return
+			}
+
+			// Embed the transaction database instance into the request context
+			ctx := context.WithValue(r.Context(), TxKey, tx)
+
+			// Execute the subsequent request handlers
+			next.ServeHTTP(w, r.WithContext(ctx))
+
+			// Commit or Rollback based on the transaction error status
+			if tx.Error != nil {
+				tx.Rollback()
+			} else {
+				tx.Commit()
+			}
+		})
+	}
+}
+
+// GetDB retrieves the transaction-bound tenant GORM DB instance from context
+func GetDB(ctx context.Context) *gorm.DB {
+	if tx, ok := ctx.Value(TxKey).(*gorm.DB); ok {
+		return tx.WithContext(ctx)
+	}
+	panic("GetDB was invoked outside of TenantSchemaMiddleware")
+}

backend/internal/web/router/router.go

@@ -4,18 +4,21 @@ import (
 	"encoding/json"
 	"net/http"
 	"strings"
-
-	"github.com/go-chi/chi/v5"
-	"github.com/go-chi/chi/v5/middleware"
+	"time"
 
 	"github.com/danyel/go-guess/backend/internal/security"
 	"github.com/danyel/go-guess/backend/internal/web/handler"
+	mw "github.com/danyel/go-guess/backend/internal/web/middleware"
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
 )
 
 func New(h *handler.Handler, tokens security.ITokenManager, frontendURL string) http.Handler {
 	router := chi.NewRouter()
 	router.Use(middleware.RequestID, middleware.RealIP, middleware.Recoverer, middleware.Compress(5))
 	router.Use(cors(frontendURL))
+	router.Use(mw.TenantSchemaMiddleware(h.Db()))
+	router.Use(middleware.Timeout(2 * time.Minute))
 	router.Get("/api/health", h.Health)
 	router.Post("/api/auth/login", h.Login)
 	router.Get("/api/interviews/{token}", h.GetInterview)