api support to update target subscriptions directly

docs/user_guide/api/targets.md

@@ -193,4 +193,43 @@ Returns an empty body if successful.
             "Error Text"
         ]
     }
-    ```
+    ```
+
+## `PATCH /api/v1/targets/{id}/subscriptions`
+
+Updates existing subscriptions for the target ID
+
+Returns an empty body if successful.
+
+=== "Request"
+    ```bash
+    curl --request PATCH gnmic-api-address:port/api/v1/targets/192.168.1.131:57400/subscriptions -d '{"subscriptions": ["sub1", "sub2"]}'
+    ```
+=== "200 OK"
+    ```json
+    ```
+=== "404 Not found"
+    ```json
+    {
+        "errors": [
+            "target $target not found"
+        ]
+    }
+    ```
+=== "400 Bad Request"
+    ```json
+    {
+        "errors": [
+            "subscriptions not found",
+            "subscription $subscription does not exist"
+        ]
+    }
+    ```
+=== "500 Internal Server Error"
+    ```json
+    {
+        "errors": [
+            "Error Text"
+        ]
+    }
+    ```

pkg/app/api.go

@@ -113,6 +113,43 @@ func (a *App) handleConfigTargetsPost(w http.ResponseWriter, r *http.Request) {
 	a.AddTargetConfig(tc)
 }
 
+func (a *App) handleConfigTargetsSubscriptions(w http.ResponseWriter, r *http.Request) {
+	vars := mux.Vars(r)
+	id := vars["id"]
+	if !a.targetConfigExists(id) {
+		w.WriteHeader(http.StatusNotFound)
+		json.NewEncoder(w).Encode(APIErrors{Errors: []string{fmt.Sprintf("target %q not found", id)}})
+		return
+	}
+	body, err := io.ReadAll(r.Body)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		json.NewEncoder(w).Encode(APIErrors{Errors: []string{err.Error()}})
+		return
+	}
+	defer r.Body.Close()
+
+	var data map[string][]string
+	err = json.Unmarshal(body, &data)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		json.NewEncoder(w).Encode(APIErrors{Errors: []string{err.Error()}})
+		return
+	}
+	subs, ok := data["subscriptions"]
+	if !ok {
+		w.WriteHeader(http.StatusBadRequest)
+		json.NewEncoder(w).Encode(APIErrors{Errors: []string{"subscriptions not found"}})
+		return
+	}
+	err = a.UpdateTargetSubscription(a.ctx, id, subs)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		json.NewEncoder(w).Encode(APIErrors{Errors: []string{err.Error()}})
+		return
+	}
+}
+
 func (a *App) handleConfigTargetsDelete(w http.ResponseWriter, r *http.Request) {
 	vars := mux.Vars(r)
 	id := vars["id"]

pkg/app/routes.go

@@ -36,6 +36,7 @@ func (a *App) configRoutes(r *mux.Router) {
 	r.HandleFunc("/config/targets/{id}", a.handleConfigTargetsGet).Methods(http.MethodGet)
 	r.HandleFunc("/config/targets", a.handleConfigTargetsPost).Methods(http.MethodPost)
 	r.HandleFunc("/config/targets/{id}", a.handleConfigTargetsDelete).Methods(http.MethodDelete)
+	r.HandleFunc("/config/targets/{id}/subscriptions", a.handleConfigTargetsSubscriptions).Methods(http.MethodPatch)
 	// config/subscriptions
 	r.HandleFunc("/config/subscriptions", a.handleConfigSubscriptions).Methods(http.MethodGet)
 	// config/outputs

pkg/app/target.go

@@ -43,7 +43,6 @@ func (a *App) initTarget(tc *types.TargetConfig) (*target.Target, error) {
 		return t, nil
 	}
 	return t, nil
-
 }
 
 func (a *App) stopTarget(ctx context.Context, name string) error {
@@ -96,6 +95,26 @@ func (a *App) DeleteTarget(ctx context.Context, name string) error {
 	return nil
 }
 
+// UpdateTargetConfig updates the subscriptions for an existing target
+func (a *App) UpdateTargetSubscription(ctx context.Context, name string, subs []string) error {
+	a.configLock.Lock()
+	for _, subName := range subs {
+		if _, ok := a.Config.Subscriptions[subName]; !ok {
+			return fmt.Errorf("subscription %q does not exist", subName)
+		}
+	}
+	targetConfig := a.Config.Targets[name]
+	targetConfig.Subscriptions = subs
+	a.configLock.Unlock()
+
+	if err := a.stopTarget(ctx, name); err != nil {
+		return err
+	}
+
+	go a.TargetSubscribeStream(ctx, targetConfig)
+	return nil
+}
+
 // AddTargetConfig adds a *TargetConfig to the configuration map
 func (a *App) AddTargetConfig(tc *types.TargetConfig) {
 	a.Logger.Printf("adding target %s", tc)