server/http: Set Content-Type header based on command output

server/http/http.go

@@ -103,6 +103,16 @@ func (i *apiHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	req := cmds.NewRequest(path, opts, nil, nil)
 	res := commands.Root.Call(req)
 
+	// set the Content-Type based on res output
+	if _, ok := res.Value().(io.Reader); ok {
+		// TODO: set based on actual Content-Type of file
+		w.Header().Set("Content-Type", "application/octet-stream")
+	} else {
+		// TODO: get proper MIME type for encoding from multicodec lib
+		enc, _ := req.Option(cmds.EncShort)
+		w.Header().Set("Content-Type", "application/"+enc.(string))
+	}
+
 	// if response contains an error, write an HTTP error status code
 	if e := res.Error(); e != nil {
 		if e.Code == cmds.ErrClient {
@@ -115,6 +125,7 @@ func (i *apiHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	_, err = io.Copy(w, res)
 	if err != nil {
 		w.WriteHeader(http.StatusInternalServerError)
+		w.Header().Set("Content-Type", "text/plain")
 		w.Write([]byte(err.Error()))
 	}
 }