refactor(cors): deduplicate origin validation and header logic without behavior change

internal/middleware/cors.go

@@ -26,12 +26,7 @@ func NewCORSConfig() *CORSConfig {
 	}
 
 	switch env {
-	case "production":
-		if origins := os.Getenv("CORS_ALLOWED_ORIGINS"); origins == "" {
-			config.AllowedOrigins = []string{}
-		}
-		config.AllowCredentials = true
-	case "staging":
+	case "production", "staging":
 		if origins := os.Getenv("CORS_ALLOWED_ORIGINS"); origins == "" {
 			config.AllowedOrigins = []string{}
 		}
@@ -53,82 +48,66 @@ func NewCORSConfig() *CORSConfig {
 	return config
 }
 
+func checkOrigin(origin string, allowedOrigins []string) (allowed bool, hasWildcard bool) {
+	for _, allowedOrigin := range allowedOrigins {
+		if allowedOrigin == "*" {
+			hasWildcard = true
+			allowed = true
+			break
+		}
+		if allowedOrigin == origin {
+			allowed = true
+			break
+		}
+	}
+	return
+}
+
+func setCORSHeaders(w http.ResponseWriter, origin string, hasWildcard bool, config *CORSConfig) {
+	if hasWildcard && !config.AllowCredentials {
+		w.Header().Set("Access-Control-Allow-Origin", "*")
+	} else {
+		w.Header().Set("Access-Control-Allow-Origin", origin)
+	}
+
+	if config.AllowCredentials && !hasWildcard {
+		w.Header().Set("Access-Control-Allow-Credentials", "true")
+	}
+}
+
 func CORSWithConfig(config *CORSConfig) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			origin := r.Header.Get("Origin")
 
-			if r.Method == "OPTIONS" {
-				if origin != "" {
-					allowed := false
-					hasWildcard := false
-					for _, allowedOrigin := range config.AllowedOrigins {
-						if allowedOrigin == "*" {
-							hasWildcard = true
-							allowed = true
-							break
-						}
-						if allowedOrigin == origin {
-							allowed = true
-							break
-						}
-					}
-
-					if !allowed {
-						http.Error(w, "Origin not allowed", http.StatusForbidden)
-						return
-					}
-
-					if hasWildcard && !config.AllowCredentials {
-						w.Header().Set("Access-Control-Allow-Origin", "*")
-					} else {
-						w.Header().Set("Access-Control-Allow-Origin", origin)
-					}
-
-					w.Header().Set("Access-Control-Allow-Methods", strings.Join(config.AllowedMethods, ", "))
-					w.Header().Set("Access-Control-Allow-Headers", strings.Join(config.AllowedHeaders, ", "))
-					w.Header().Set("Access-Control-Max-Age", fmt.Sprintf("%d", config.MaxAge))
-
-					if config.AllowCredentials && !hasWildcard {
-						w.Header().Set("Access-Control-Allow-Credentials", "true")
-					}
+			if origin == "" {
+				if r.Method == "OPTIONS" {
+					w.WriteHeader(http.StatusOK)
+					return
 				}
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			allowed, hasWildcard := checkOrigin(origin, config.AllowedOrigins)
+
+			if !allowed {
+				http.Error(w, "Origin not allowed", http.StatusForbidden)
+				return
+			}
+
+			if r.Method == "OPTIONS" {
+				setCORSHeaders(w, origin, hasWildcard, config)
+
+				w.Header().Set("Access-Control-Allow-Methods", strings.Join(config.AllowedMethods, ", "))
+				w.Header().Set("Access-Control-Allow-Headers", strings.Join(config.AllowedHeaders, ", "))
+				w.Header().Set("Access-Control-Max-Age", fmt.Sprintf("%d", config.MaxAge))
 
 				w.WriteHeader(http.StatusOK)
 				return
 			}
 
-			if origin != "" {
-				allowed := false
-				hasWildcard := false
-				for _, allowedOrigin := range config.AllowedOrigins {
-					if allowedOrigin == "*" {
-						hasWildcard = true
-						allowed = true
-						break
-					}
-					if allowedOrigin == origin {
-						allowed = true
-						break
-					}
-				}
-
-				if !allowed {
-					http.Error(w, "Origin not allowed", http.StatusForbidden)
-					return
-				}
-
-				if hasWildcard && !config.AllowCredentials {
-					w.Header().Set("Access-Control-Allow-Origin", "*")
-				} else {
-					w.Header().Set("Access-Control-Allow-Origin", origin)
-				}
-
-				if config.AllowCredentials && !hasWildcard {
-					w.Header().Set("Access-Control-Allow-Credentials", "true")
-				}
-			}
-
+			setCORSHeaders(w, origin, hasWildcard, config)
 			next.ServeHTTP(w, r)
 		})
 	}