From 0a4abdb48c925b1c7efe12c5a7cef38c1aa67a53 Mon Sep 17 00:00:00 2001
From: LordMathis <matus@namesny.com>
Date: Tue, 4 Nov 2025 19:04:26 +0100
Subject: [PATCH] Add Vary header

---
 server/internal/handlers/static_handler.go            |  2 ++
 .../handlers/static_handler_integration_test.go       | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/server/internal/handlers/static_handler.go b/server/internal/handlers/static_handler.go
index 0b2ffab..13944ce 100644
--- a/server/internal/handlers/static_handler.go
+++ b/server/internal/handlers/static_handler.go
@@ -108,6 +108,7 @@ func (h *StaticHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		if _, err := os.Stat(brPath); err == nil {
 			w.Header().Set("Content-Encoding", "br")
 			w.Header().Set("Content-Type", getContentType(cleanPath))
+			w.Header().Set("Vary", "Accept-Encoding")
 			http.ServeFile(w, r, brPath)
 			return
 		}
@@ -119,6 +120,7 @@ func (h *StaticHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		if _, err := os.Stat(gzPath); err == nil {
 			w.Header().Set("Content-Encoding", "gzip")
 			w.Header().Set("Content-Type", getContentType(cleanPath))
+			w.Header().Set("Vary", "Accept-Encoding")
 			http.ServeFile(w, r, gzPath)
 			return
 		}
diff --git a/server/internal/handlers/static_handler_integration_test.go b/server/internal/handlers/static_handler_integration_test.go
index 0835cad..38f1584 100644
--- a/server/internal/handlers/static_handler_integration_test.go
+++ b/server/internal/handlers/static_handler_integration_test.go
@@ -56,6 +56,7 @@ func TestStaticHandler_Integration(t *testing.T) {
 		wantType        string
 		wantEncoding    string
 		wantCacheHeader string
+		wantVary        string
 	}{
 		{
 			name:       "serve index.html",
@@ -73,6 +74,7 @@ func TestStaticHandler_Integration(t *testing.T) {
 			wantType:        "text/css",
 			wantEncoding:    "gzip",
 			wantCacheHeader: "public, max-age=31536000",
+			wantVary:        "Accept-Encoding",
 		},
 		{
 			name:            "serve JS with gzip support",
@@ -83,6 +85,7 @@ func TestStaticHandler_Integration(t *testing.T) {
 			wantType:        "application/javascript",
 			wantEncoding:    "gzip",
 			wantCacheHeader: "public, max-age=31536000",
+			wantVary:        "Accept-Encoding",
 		},
 		{
 			name:            "serve CSS without gzip",
@@ -127,6 +130,7 @@ func TestStaticHandler_Integration(t *testing.T) {
 			wantType:        "text/css",
 			wantEncoding:    "br",
 			wantCacheHeader: "public, max-age=31536000",
+			wantVary:        "Accept-Encoding",
 		},
 		{
 			name:            "serve JS with brotli support",
@@ -137,6 +141,7 @@ func TestStaticHandler_Integration(t *testing.T) {
 			wantType:        "application/javascript",
 			wantEncoding:    "br",
 			wantCacheHeader: "public, max-age=31536000",
+			wantVary:        "Accept-Encoding",
 		},
 		{
 			name:            "prefer brotli over gzip when both supported",
@@ -147,6 +152,7 @@ func TestStaticHandler_Integration(t *testing.T) {
 			wantType:        "application/javascript",
 			wantEncoding:    "br",
 			wantCacheHeader: "public, max-age=31536000",
+			wantVary:        "Accept-Encoding",
 		},
 		{
 			name:            "fallback to gzip when brotli not available",
@@ -157,6 +163,7 @@ func TestStaticHandler_Integration(t *testing.T) {
 			wantType:        "application/javascript",
 			wantEncoding:    "br",
 			wantCacheHeader: "public, max-age=31536000",
+			wantVary:        "Accept-Encoding",
 		},
 	}
 
@@ -183,6 +190,10 @@ func TestStaticHandler_Integration(t *testing.T) {
 				if tc.wantCacheHeader != "" {
 					assert.Equal(t, tc.wantCacheHeader, w.Header().Get("Cache-Control"))
 				}
+
+				if tc.wantVary != "" {
+					assert.Equal(t, tc.wantVary, w.Header().Get("Vary"))
+				}
 			}
 		})
 	}