Use write interceptor from faas-provider

We now have two write interceptors, with one moved into
faas-provider. This commit makes the gateway use the new
external package and deletes its own.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alex@openfaas.com>

gateway/handlers/notifier_handler.go

@@ -6,50 +6,21 @@ package handlers
 import (
 	"net/http"
 	"time"
+
+	"github.com/openfaas/faas-provider/httputil"
 )
 
 // MakeNotifierWrapper wraps a http.HandlerFunc in an interceptor to pass to HTTPNotifier
 func MakeNotifierWrapper(next http.HandlerFunc, notifiers []HTTPNotifier) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		then := time.Now()
-
-		writer := newWriteInterceptor(w)
-		next(&writer, r)
-
 		url := r.URL.String()
+
+		writer := httputil.NewHttpWriteInterceptor(w)
+		next(writer, r)
+
 		for _, notifier := range notifiers {
 			notifier.Notify(r.Method, url, url, writer.Status(), "completed", time.Since(then))
 		}
 	}
 }
-
-func newWriteInterceptor(w http.ResponseWriter) writeInterceptor {
-	return writeInterceptor{
-		w: w,
-	}
-}
-
-type writeInterceptor struct {
-	CapturedStatusCode int
-	w                  http.ResponseWriter
-}
-
-func (c *writeInterceptor) Status() int {
-	if c.CapturedStatusCode == 0 {
-		return http.StatusOK
-	}
-	return c.CapturedStatusCode
-}
-
-func (c *writeInterceptor) Header() http.Header {
-	return c.w.Header()
-}
-
-func (c *writeInterceptor) Write(data []byte) (int, error) {
-	return c.w.Write(data)
-}
-
-func (c *writeInterceptor) WriteHeader(code int) {
-	c.CapturedStatusCode = code
-	c.w.WriteHeader(code)
-}