From 63cd339f5e51b9240b8a76d551a6a6dafb71d276 Mon Sep 17 00:00:00 2001
From: Alexander Khodyrev <a@akho.name>
Date: Sat, 28 Sep 2024 13:14:15 +0300
Subject: [PATCH] switch to Go 1.22-style routing

---
 birdtown-visit-counter.go | 80 +++++++++++++++++++--------------------
 1 file changed, 39 insertions(+), 41 deletions(-)

diff --git a/birdtown-visit-counter.go b/birdtown-visit-counter.go
index e9308a1..9da7010 100644
--- a/birdtown-visit-counter.go
+++ b/birdtown-visit-counter.go
@@ -46,50 +46,47 @@ func (s *visitsStore) visit(ending string) int {
 	return newVisits
 }
 
-type visitsHandler struct {
-	store *visitsStore
-}
-
-func (h *visitsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+func commonHeaders(w http.ResponseWriter) {
 	// CORS: this is expected to be called from a different domain,
 	// hoops require jumping
 	w.Header().Set("Access-Control-Allow-Origin", "*")
 	w.Header().Set("Access-Control-Max-Age", "86400")
 	w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS")
 	w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization")
-
-	w.Header().Set("content-type", "application/json")
-
-	if r.Method == http.MethodPost {
-		var s string
-		if err := json.NewDecoder(r.Body).Decode(&s); err != nil {
-			w.WriteHeader(http.StatusInternalServerError)
-			w.Write([]byte("cannot parse data"))
-			return
-		}
-		w.WriteHeader(http.StatusOK)
-		w.Write(([]byte)(strconv.Itoa(h.store.visit(s))))
-		return
-	}
-	if r.Method == http.MethodGet {
-		h.store.Lock()
-		jsonBytes, err := json.Marshal(h.store.m)
-		h.store.Unlock()
-		if err != nil {
-			w.WriteHeader(http.StatusInternalServerError)
-			w.Write([]byte("cannot serialize"))
-			return
-		}
-		w.WriteHeader(http.StatusOK)
-		w.Write(jsonBytes)
-		return
-	}
-	if r.Method == http.MethodOptions {
-		w.WriteHeader(http.StatusOK)
-		return
-	}
 	w.Header().Set("Allow", "POST, GET, OPTIONS")
-	w.WriteHeader(http.StatusMethodNotAllowed)
+}
+
+func (store *visitsStore) handleOptions(w http.ResponseWriter, r *http.Request) {
+	commonHeaders(w)
+	w.WriteHeader(http.StatusOK)
+}
+
+func (store *visitsStore) handlePost(w http.ResponseWriter, r *http.Request) {
+	commonHeaders(w)
+	w.Header().Set("content-type", "application/json")
+	var s string
+	if err := json.NewDecoder(r.Body).Decode(&s); err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("cannot parse data"))
+		return
+	}
+	w.WriteHeader(http.StatusOK)
+	w.Write(([]byte)(strconv.Itoa(store.visit(s))))
+}
+
+func (store *visitsStore) handleGet(w http.ResponseWriter, r *http.Request) {
+	commonHeaders(w)
+	w.Header().Set("content-type", "application/json")
+	store.Lock()
+	jsonBytes, err := json.Marshal(store.m)
+	store.Unlock()
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("cannot serialize"))
+		return
+	}
+	w.WriteHeader(http.StatusOK)
+	w.Write(jsonBytes)
 }
 
 func main() {
@@ -104,11 +101,12 @@ func main() {
 	} else {
 		log.Println("initial file", *initialFile, "could not be read, defaulting to empty data")
 	}
-
 	store := visitsStore{m: initialVisits, RWMutex: &sync.RWMutex{}}
-	visitsH := &visitsHandler{store: &store}
-	http.Handle("/", visitsH)
 
-	log.Println("Starting web server...")
+	http.HandleFunc("GET /", store.handleGet)
+	http.HandleFunc("POST /", store.handlePost)
+	http.HandleFunc("OPTIONS /", store.handleOptions)
+
+	log.Println("Starting web server at ", *addr, "...")
 	http.ListenAndServe(*addr, nil)
 }