Give static HTML pages an ETag

1 files changed, 48 insertions, 42 deletions

diff --git a/roseh.moe.go b/roseh.moe.go
index 8654282..23e96ce 100644
--- a/roseh.moe.go
+++ b/roseh.moe.go
@@ -147,6 +147,14 @@ func loadConfig() (*serviceConfiguration, error) {
 	return config, nil
 }
 
+func makeETag(content io.Reader) (string, error) {
+	h := sha256.New()
+	if _, err := io.Copy(h, content); err != nil {
+		return "", err
+	}
+	return `"` + base64.RawURLEncoding.EncodeToString(h.Sum(nil)[:8]) + `"`, nil
+}
+
 var (
 	//go:embed templates/outline.html.template
 	outlineString   string
@@ -165,6 +173,32 @@ func outlinedTemplate(s string) (*template.Template, error) {
 	return t.Lookup("outline"), nil
 }
 
+type staticHandler struct {
+	content, eTag string
+}
+
+func (h *staticHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	w.Header().Set("ETag", h.eTag)
+	http.ServeContent(w, r, "", time.Time{}, strings.NewReader(h.content))
+}
+
+func mustStaticTemplate(tmpl *template.Template) *staticHandler {
+	buf := new(strings.Builder)
+	if err := tmpl.Execute(buf, nil); err != nil {
+		panic(err)
+	}
+	content := buf.String()
+	eTag, err := makeETag(strings.NewReader(content))
+	if err != nil {
+		panic(err)
+	}
+	return &staticHandler{
+		content: buf.String(),
+		eTag:    eTag,
+	}
+}
+
 var (
 	//go:embed templates/404.html.template
 	notFoundString   string
@@ -183,52 +217,28 @@ func notFound(w http.ResponseWriter, r *http.Request) {
 
 var (
 	//go:embed templates/index.html.template
-	indexString   string
-	indexTemplate = template.Must(outlinedTemplate(indexString))
+	indexString  string
+	indexHandler = mustStaticTemplate(template.Must(outlinedTemplate(indexString)))
 )
 
-func index(w http.ResponseWriter, _ *http.Request) {
-	if err := indexTemplate.Execute(w, nil); err != nil {
-		log.Printf("Warning: index: %s", err)
-	}
-}
-
 var (
 	//go:embed templates/games/index.html.template
-	gamesIndexString   string
-	gamesIndexTemplate = template.Must(outlinedTemplate(gamesIndexString))
+	gamesIndexString  string
+	gamesIndexHandler = mustStaticTemplate(template.Must(outlinedTemplate(gamesIndexString)))
 )
 
-func gamesIndex(w http.ResponseWriter, _ *http.Request) {
-	if err := gamesIndexTemplate.Execute(w, nil); err != nil {
-		log.Printf("Waning: gamesIndex: %s", err)
-	}
-}
-
 var (
 	//go:embed templates/games/pong.html.template
-	pongString   string
-	pongTemplate = template.Must(template.New("pong").Parse(pongString))
+	pongString  string
+	pongHandler = mustStaticTemplate(template.Must(template.New("pong").Parse(pongString)))
 )
 
-func pong(w http.ResponseWriter, _ *http.Request) {
-	if err := pongTemplate.Execute(w, nil); err != nil {
-		log.Printf("Warning: pong: %s", err)
-	}
-}
-
 var (
 	//go:embed templates/games/rms.html.template
-	stallmanShooterString   string
-	stallmanShooterTemplate = template.Must(outlinedTemplate(stallmanShooterString))
+	stallmanShooterString  string
+	stallmanShooterHandler = mustStaticTemplate(template.Must(outlinedTemplate(stallmanShooterString)))
 )
 
-func stallmanShooter(w http.ResponseWriter, _ *http.Request) {
-	if err := stallmanShooterTemplate.Execute(w, nil); err != nil {
-		log.Printf("Warning: stallmanShooter: %s", err)
-	}
-}
-
 //go:embed static
 var staticFiles embed.FS
 
@@ -245,11 +255,9 @@ func buildStaticFileHashes() map[string]string {
 			return err
 		}
 		defer f.Close()
-		h := sha256.New()
-		if _, err := io.Copy(h, f); err != nil {
+		if hashMap[path], err = makeETag(f); err != nil {
 			return err
 		}
-		hashMap[path] = `"` + base64.RawURLEncoding.EncodeToString(h.Sum(nil)[:8]) + `"`
 		return nil
 	}); err != nil {
 		panic(fmt.Sprintf("Build static file hash map: %s", err))
@@ -288,9 +296,7 @@ func qrHandler(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, fmt.Sprintf("failed to encode QR code: %s", err), http.StatusInternalServerError)
 		return
 	}
-	w.Header().Set("Content-Type", "image/png")
-	w.Header().Set("Content-Length", strconv.Itoa(len(qr)))
-	w.Write(qr)
+	http.ServeContent(w, r, "qr.png", time.Time{}, bytes.NewReader(qr))
 }
 
 var (
@@ -1059,10 +1065,10 @@ func main() {
 	}()
 
 	mux := http.NewServeMux()
-	mux.HandleFunc("GET /{$}", index)
-	mux.HandleFunc("GET /games/{$}", gamesIndex)
-	mux.HandleFunc("GET /games/pong", pong)
-	mux.HandleFunc("GET /games/rms", stallmanShooter)
+	mux.Handle("GET /{$}", indexHandler)
+	mux.Handle("GET /games/{$}", gamesIndexHandler)
+	mux.Handle("GET /games/pong", pongHandler)
+	mux.Handle("GET /games/rms", stallmanShooterHandler)
 	mux.HandleFunc("GET /qr.png", qrHandler)
 	mux.HandleFunc("GET /wormhole", wormhole)
 	mux.HandleFunc("POST /wormhole", wormholeUpload)