MySQL: extract tlog http API config to function

This small refactoring clearly demonstrates the handlers that are configured for the core tlog spec. The method could be moved in the future, but I suggest leaving it here at first to make sure that any other implementation is exactly the same.

Towards transparency-dev#21.

cmd/example-mysql/main.go

@@ -80,7 +80,41 @@ func main() {
 		klog.Exitf("Failed to create new MySQL storage: %v", err)
 	}
 
-	http.HandleFunc("GET /checkpoint", func(w http.ResponseWriter, r *http.Request) {
+	configureTilesReadApi(http.DefaultServeMux, storage)
+	http.HandleFunc("POST /add", func(w http.ResponseWriter, r *http.Request) {
+		b, err := io.ReadAll(r.Body)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		defer func() {
+			if err := r.Body.Close(); err != nil {
+				klog.Warningf("/add: %v", err)
+			}
+		}()
+		idx, err := storage.Add(r.Context(), tessera.NewEntry(b))
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			_, _ = w.Write([]byte(err.Error()))
+			return
+		}
+		if _, err = w.Write([]byte(fmt.Sprintf("%d", idx))); err != nil {
+			klog.Errorf("/add: %v", err)
+			return
+		}
+	})
+
+	if err := http.ListenAndServe(*listen, http.DefaultServeMux); err != nil {
+		klog.Exitf("ListenAndServe: %v", err)
+	}
+}
+
+// configureTilesReadApi adds the API methods from https://c2sp.org/tlog-tiles to the mux,
+// routing the requests to the mysql storage.
+// This method could be moved into the storage API as it's likely this will be
+// the same for any implementation of a personality based on MySQL.
+func configureTilesReadApi(mux *http.ServeMux, storage *mysql.Storage) {
+	mux.HandleFunc("GET /checkpoint", func(w http.ResponseWriter, r *http.Request) {
 		checkpoint, err := storage.ReadCheckpoint(r.Context())
 		if err != nil {
 			klog.Errorf("/checkpoint: %v", err)
@@ -98,7 +132,7 @@ func main() {
 		}
 	})
 
-	http.HandleFunc("GET /tile/{level}/{index...}", func(w http.ResponseWriter, r *http.Request) {
+	mux.HandleFunc("GET /tile/{level}/{index...}", func(w http.ResponseWriter, r *http.Request) {
 		level, index, width, err := layout.ParseTileLevelIndexWidth(r.PathValue("level"), r.PathValue("index"))
 		if err != nil {
 			w.WriteHeader(http.StatusBadRequest)
@@ -127,7 +161,7 @@ func main() {
 		}
 	})
 
-	http.HandleFunc("GET /tile/entries/{index...}", func(w http.ResponseWriter, r *http.Request) {
+	mux.HandleFunc("GET /tile/entries/{index...}", func(w http.ResponseWriter, r *http.Request) {
 		index, _, err := layout.ParseTileIndexWidth(r.PathValue("index"))
 		if err != nil {
 			w.WriteHeader(http.StatusBadRequest)
@@ -155,33 +189,6 @@ func main() {
 			return
 		}
 	})
-
-	http.HandleFunc("POST /add", func(w http.ResponseWriter, r *http.Request) {
-		b, err := io.ReadAll(r.Body)
-		if err != nil {
-			w.WriteHeader(http.StatusInternalServerError)
-			return
-		}
-		defer func() {
-			if err := r.Body.Close(); err != nil {
-				klog.Warningf("/add: %v", err)
-			}
-		}()
-		idx, err := storage.Add(r.Context(), tessera.NewEntry(b))
-		if err != nil {
-			w.WriteHeader(http.StatusInternalServerError)
-			_, _ = w.Write([]byte(err.Error()))
-			return
-		}
-		if _, err = w.Write([]byte(fmt.Sprintf("%d", idx))); err != nil {
-			klog.Errorf("/add: %v", err)
-			return
-		}
-	})
-
-	if err := http.ListenAndServe(*listen, http.DefaultServeMux); err != nil {
-		klog.Exitf("ListenAndServe: %v", err)
-	}
 }
 
 func initDatabaseSchema(ctx context.Context) {