add static middleware module

modules/static.go

+/* ----------------------------------------------------------------------
+ *       ______      ___                         __
+ *      / ____/___  /   |  ____  __  ___      __/ /_  ___  ________
+ *     / / __/ __ \/ /| | / __ \/ / / / | /| / / __ \/ _ \/ ___/ _ \
+ *    / /_/ / /_/ / ___ |/ / / / /_/ /| |/ |/ / / / /  __/ /  /  __/
+ *    \____/\____/_/  |_/_/ /_/\__. / |__/|__/_/ /_/\___/_/   \___/
+ *                            /____/
+ *
+ * (C) Copyright 2015 GoAnywhere (http://goanywhere.io).
+ * ----------------------------------------------------------------------
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ * ----------------------------------------------------------------------*/
+package modules
+
+import (
+	"net/http"
+	"path"
+	"strings"
+)
+
+// Static serves as file server for static assets,
+// as convention, the given dir name will be used as the URL prefix.
+func Static(dir string) func(http.Handler) http.Handler {
+	var (
+		fs     = http.Dir(dir)
+		prefix = path.Join("/", dir)
+	)
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			// Accepts http GET | HEAD Only, ignores all requests not started with prefix.
+			if r.Method != "GET" && r.Method != "HEAD" {
+				next.ServeHTTP(w, r)
+				return
+			} else if !strings.HasPrefix(r.URL.Path, prefix) {
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			filename := strings.TrimPrefix(r.URL.Path, prefix)
+			if filename != "" && filename[0] != '/' {
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			file, err := fs.Open(filename)
+			if err != nil {
+				next.ServeHTTP(w, r)
+				return
+			}
+			defer file.Close()
+
+			stat, err := file.Stat()
+			if err != nil {
+				next.ServeHTTP(w, r)
+				return
+			}
+
+			// try to serve index filename
+			if stat.IsDir() {
+				// redirect if missing trailing slash
+				if !strings.HasSuffix(r.URL.Path, "/") {
+					http.Redirect(w, r, r.URL.Path+"/", http.StatusFound)
+					return
+				}
+
+				filename = path.Join(filename, "index.html")
+				file, err = fs.Open(filename)
+				if err != nil {
+					next.ServeHTTP(w, r)
+					return
+				}
+				defer file.Close()
+
+				stat, err = file.Stat()
+				if err != nil || stat.IsDir() {
+					next.ServeHTTP(w, r)
+					return
+				}
+			}
+
+			http.ServeContent(w, r, filename, stat.ModTime(), file)
+		})
+	}
+}