fallback signature parameter added

pkg/memostream/memoServerHandlerMain.go

@@ -15,6 +15,7 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"net/url"
+	"regexp"
 	"strings"
 )
 
@@ -39,6 +40,8 @@ func proxy(url url.URL, w http.ResponseWriter, req *http.Request) {
 	rp.ServeHTTP(w, req)
 }
 
+var regexpFallback = regexp.MustCompile("^fallback(.+)$")
+
 func (ms *memoServer) mainHandler(w http.ResponseWriter, req *http.Request) {
 	// remove prefix and use whole rest of url as signature
 	vars := mux.Vars(req)
@@ -48,14 +51,30 @@ func (ms *memoServer) mainHandler(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 	action, _ := vars["action"]
-	params, _ := vars["params"]
-	//signature := strings.TrimPrefix(req.URL.Path, ms.urlPrefix)
+	paramstr, _ := vars["paramstr"]
+	params := strings.Split(paramstr, "/")
 
 	// resolve signature
 	me, err := ms.resolver.resolve(signature)
 	if err != nil {
-		ms.DoPanicf(w, http.StatusNotFound, "signature %v not found: %v", signature, err)
-		return
+		// check for fallback parameter only if needed
+		fallback := ""
+		for _, p := range params {
+			if matches := regexpFallback.FindStringSubmatch(p); matches != nil {
+				fallback = matches[1]
+				break
+			}
+		}
+		if fallback != "" {
+			me, err = ms.resolver.resolve(fallback)
+			if err != nil {
+				ms.DoPanicf(w, http.StatusNotFound, "signature %v and fallback %v not found: %v", signature, fallback, err)
+				return
+			}
+		} else {
+			ms.DoPanicf(w, http.StatusNotFound, "signature %v not found: %v", signature, err)
+			return
+		}
 	}
 	if me.Access != Media_Public {
 		if err := CheckRequestJWT(req, ms.jwtSecret, ms.jwtAlg, signature); err != nil {
@@ -69,7 +88,7 @@ func (ms *memoServer) mainHandler(w http.ResponseWriter, req *http.Request) {
 	}
 	if actions, ok := ms.actions[me.Type]; ok {
 		for _, a := range actions {
-			ok, err := a.Do(w, req, me, action, strings.Split(params, "/")...)
+			ok, err := a.Do(w, req, me, action, params...)
 			if err != nil {
 				ms.DoPanicf(w, http.StatusInternalServerError, "Cannot execute action %s on signature %s: %v", action, me.Signature, err)
 				return