Use adapter pattern for handlers

adapters.go

@@ -0,0 +1,15 @@
+package main
+
+import "net/http"
+
+// Adapter is an HTTP middleware
+type Adapter func(http.Handler) http.Handler
+
+// Adapt applies adapters to an HTTP handler function
+func Adapt(h http.Handler, adapters ...Adapter) http.Handler {
+	for i := len(adapters) - 1; i >= 0; i-- {
+		h = adapters[i](h)
+	}
+
+	return h
+}

api.go

@@ -19,7 +19,8 @@ type CopyObjectInfo struct {
 }
 
 // CreateBucketHandler creates a new bucket
-func (s *Server) CreateBucketHandler(w http.ResponseWriter, r *http.Request) {
+func (s *Server) CreateBucketHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		var bucket minio.BucketInfo
 
 		err := json.NewDecoder(r.Body).Decode(&bucket)
@@ -42,10 +43,12 @@ func (s *Server) CreateBucketHandler(w http.ResponseWriter, r *http.Request) {
 			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
+	})
 }
 
 // CreateObjectHandler allows to upload a new object
-func (s *Server) CreateObjectHandler(w http.ResponseWriter, r *http.Request) {
+func (s *Server) CreateObjectHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		vars := mux.Vars(r)
 
 		if r.Header.Get("Content-Type") == "application/json" {
@@ -95,10 +98,12 @@ func (s *Server) CreateObjectHandler(w http.ResponseWriter, r *http.Request) {
 
 			w.WriteHeader(http.StatusCreated)
 		}
+	})
 }
 
 // DeleteBucketHandler deletes a bucket
-func (s *Server) DeleteBucketHandler(w http.ResponseWriter, r *http.Request) {
+func (s *Server) DeleteBucketHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		vars := mux.Vars(r)
 
 		err := s.s3.RemoveBucket(vars["bucketName"])
@@ -108,10 +113,12 @@ func (s *Server) DeleteBucketHandler(w http.ResponseWriter, r *http.Request) {
 		}
 
 		w.WriteHeader(http.StatusNoContent)
+	})
 }
 
 // DeleteObjectHandler deletes an object
-func (s *Server) DeleteObjectHandler(w http.ResponseWriter, r *http.Request) {
+func (s *Server) DeleteObjectHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		vars := mux.Vars(r)
 
 		err := s.s3.RemoveObject(vars["bucketName"], vars["objectName"])
@@ -121,10 +128,12 @@ func (s *Server) DeleteObjectHandler(w http.ResponseWriter, r *http.Request) {
 		}
 
 		w.WriteHeader(http.StatusOK)
+	})
 }
 
 // GetObjectHandler downloads an object to the client
-func (s *Server) GetObjectHandler(w http.ResponseWriter, r *http.Request) {
+func (s *Server) GetObjectHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		vars := mux.Vars(r)
 		objectName := vars["objectName"]
 
@@ -142,4 +151,5 @@ func (s *Server) GetObjectHandler(w http.ResponseWriter, r *http.Request) {
 			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
+	})
 }

logger.go

@@ -7,9 +7,9 @@ import (
 )
 
 // Logger logs HTTP requests
-func Logger() Middleware {
+func Logger() Adapter {
-	return func(next http.HandlerFunc) http.HandlerFunc {
+	return func(next http.Handler) http.Handler {
-		return func(w http.ResponseWriter, r *http.Request) {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			start := time.Now()
 
 			defer func() {
@@ -21,7 +21,7 @@ func Logger() Middleware {
 				)
 			}()
 
-			next(w, r)
+			next.ServeHTTP(w, r)
-		}
+		})
 	}
 }

main.go

@@ -29,15 +29,15 @@ func main() {
 	router.
 		Methods("GET").
 		Path("/").
-		HandlerFunc(Chain(IndexHandler, Logger()))
+		Handler(Adapt(IndexHandler(), Logger()))
 	router.
 		Methods("GET").
 		Path("/buckets").
-		HandlerFunc(Chain(s.BucketsPageHandler, Logger()))
+		Handler(Adapt(s.BucketsPageHandler(), Logger()))
 	router.
 		Methods("GET").
 		Path("/buckets/{bucketName}").
-		HandlerFunc(Chain(s.BucketPageHandler, Logger()))
+		Handler(Adapt(s.BucketPageHandler(), Logger()))
 
 	api := router.PathPrefix("/api").Subrouter()
 
@@ -45,23 +45,23 @@ func main() {
 	buckets.
 		Methods("POST").
 		Path("").
-		HandlerFunc(Chain(s.CreateBucketHandler, Logger()))
+		Handler(Adapt(s.CreateBucketHandler(), Logger()))
 	buckets.
 		Methods("DELETE").
 		Path("/{bucketName}").
-		HandlerFunc(Chain(s.DeleteBucketHandler, Logger()))
+		Handler(Adapt(s.DeleteBucketHandler(), Logger()))
 	buckets.
 		Methods("POST").
 		Path("/{bucketName}/objects").
-		HandlerFunc(Chain(s.CreateObjectHandler, Logger()))
+		Handler(Adapt(s.CreateObjectHandler(), Logger()))
 	buckets.
 		Methods("GET").
 		Path("/{bucketName}/objects/{objectName}").
-		HandlerFunc(Chain(s.GetObjectHandler, Logger()))
+		Handler(Adapt(s.GetObjectHandler(), Logger()))
 	buckets.
 		Methods("DELETE").
 		Path("/{bucketName}/objects/{objectName}").
-		HandlerFunc(Chain(s.DeleteObjectHandler, Logger()))
+		Handler(Adapt(s.DeleteObjectHandler(), Logger()))
 
 	log.Fatal(http.ListenAndServe(":"+port, router))
 }

middleware.go

@@ -1,14 +0,0 @@
-package main
-
-import "net/http"
-
-// Middleware is an HTTP middleware
-type Middleware func(http.HandlerFunc) http.HandlerFunc
-
-// Chain applies middleware to an HTTP handler function
-func Chain(f http.HandlerFunc, middlewares ...Middleware) http.HandlerFunc {
-	for i := len(middlewares) - 1; i >= 0; i-- {
-		f = middlewares[i](f)
-	}
-	return f
-}

pages.go

@@ -22,7 +22,8 @@ type ObjectWithIcon struct {
 }
 
 // BucketPageHandler shows the details page of a bucket
-func (s *Server) BucketPageHandler(w http.ResponseWriter, r *http.Request) {
+func (s *Server) BucketPageHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		bucketName := mux.Vars(r)["bucketName"]
 		var objects []ObjectWithIcon
 
@@ -57,10 +58,12 @@ func (s *Server) BucketPageHandler(w http.ResponseWriter, r *http.Request) {
 			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
+	})
 }
 
 // BucketsPageHandler shows all buckets
-func (s *Server) BucketsPageHandler(w http.ResponseWriter, r *http.Request) {
+func (s *Server) BucketsPageHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		lp := path.Join("templates", "layout.html")
 		ip := path.Join("templates", "index.html")
 
@@ -81,11 +84,14 @@ func (s *Server) BucketsPageHandler(w http.ResponseWriter, r *http.Request) {
 			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
+	})
 }
 
 // IndexHandler forwards to "/buckets"
-func IndexHandler(w http.ResponseWriter, r *http.Request) {
+func IndexHandler() http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/buckets", http.StatusPermanentRedirect)
+	})
 }
 
 // icon returns an icon for a file type