lil refactor

main.go

@@ -15,6 +15,40 @@ import (
 	"time"
 )
 
+var httpc = &http.Client{
+	Timeout: time.Minute,
+	Transport: &http.Transport{
+		DisableKeepAlives: true,
+	},
+}
+
+type Handler struct {
+	tmpl   *template.Template
+	target *url.URL
+}
+
+func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if err := h.serveHTTP(w, r); err != nil {
+		log.Println("!", err)
+		http.Error(w, err.Error(), http.StatusBadRequest)
+	}
+}
+
+func (h Handler) serveHTTP(w http.ResponseWriter, r *http.Request) error {
+	b, err := adapt(r.Body, h.tmpl)
+	if err != nil {
+		return err
+	}
+
+	resp, err := proxy(h.target, r, io.NopCloser(bytes.NewReader(b)))
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	return forward(w, resp)
+}
+
 func main() {
 	fs := flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
 	p := fs.Int("p", 28080, "port")
@@ -34,66 +68,55 @@ func main() {
 		panic(err)
 	}
 
-	c := &http.Client{
-		Timeout: time.Minute,
-		Transport: &http.Transport{
-			DisableKeepAlives: true,
-		},
-	}
-
-	handle := func(w http.ResponseWriter, r *http.Request) error {
-		b, _ := io.ReadAll(io.LimitReader(r.Body, 1024*1024))
-
-		var v interface{}
-		if err := json.Unmarshal(b, &v); err != nil {
-			return err
-		}
-		buff := bytes.NewBuffer(nil)
-		if err := tmpl.Execute(buff, v); err != nil {
-			return err
-		}
-
-		log.Printf("%s => %s => %s", b, buff.Bytes(), u.String())
-
-		req, err := http.NewRequest(r.Method, u.String(), io.NopCloser(buff))
-		if err != nil {
-			return err
-		}
-		req = req.WithContext(r.Context())
-		for k, v := range r.Header {
-			switch strings.ToLower(k) {
-			case "content-length":
-			default:
-				req.Header.Set(k, v[0])
-				for _, v := range v[1:] {
-					req.Header.Add(k, v)
-				}
-			}
-		}
-		resp, err := c.Do(req)
-		if err != nil {
-			return err
-		}
-		defer resp.Body.Close()
-
-		for k, v := range resp.Header {
-			w.Header().Set(k, v[0])
-			for _, v := range v[1:] {
-				w.Header().Add(k, v)
-			}
-		}
-		w.WriteHeader(resp.StatusCode)
-		io.Copy(w, resp.Body)
-
-		return nil
-	}
+	h := Handler{tmpl: tmpl, target: u}
 	log.Println("listening on", *p)
-	if err := http.ListenAndServe(":"+strconv.Itoa(*p), http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if err := handle(w, r); err != nil {
-			log.Println("!", err)
-			http.Error(w, err.Error(), http.StatusBadRequest)
-		}
-	})); err != nil {
+	if err := http.ListenAndServe(":"+strconv.Itoa(*p), h); err != nil {
 		panic(err)
 	}
 }
+
+func adapt(r io.Reader, tmpl *template.Template) ([]byte, error) {
+	b, _ := io.ReadAll(io.LimitReader(r, 1024*1024))
+	var v interface{}
+	buff := bytes.NewBuffer(nil)
+	if err := json.Unmarshal(b, &v); err != nil {
+		return nil, err
+	} else if err := tmpl.Execute(buff, v); err != nil {
+		return nil, err
+	}
+	log.Printf("%s => %s", b, buff.Bytes())
+	return buff.Bytes(), nil
+}
+
+func proxy(u *url.URL, r *http.Request, rc io.ReadCloser) (*http.Response, error) {
+	req, err := http.NewRequest(r.Method, u.String(), rc)
+	if err != nil {
+		return nil, err
+	}
+
+	req = req.WithContext(r.Context())
+	for k, v := range r.Header {
+		switch strings.ToLower(k) {
+		case "content-length":
+		default:
+			req.Header.Set(k, v[0])
+			for _, v := range v[1:] {
+				req.Header.Add(k, v)
+			}
+		}
+	}
+
+	return httpc.Do(req)
+}
+
+func forward(w http.ResponseWriter, resp *http.Response) error {
+	for k, v := range resp.Header {
+		w.Header().Set(k, v[0])
+		for _, v := range v[1:] {
+			w.Header().Add(k, v)
+		}
+	}
+	w.WriteHeader(resp.StatusCode)
+	io.Copy(w, resp.Body)
+	return nil
+}