Frontend first draft

frontend/pshared/lib/utils/snackbar.dart

@@ -0,0 +1,31 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+
+
+ScaffoldFeatureController<SnackBar, SnackBarClosedReason> notifyUserX(ScaffoldMessengerState sm, String message, { int delaySeconds = 3 }) 
+{
+  return sm.showSnackBar(
+    SnackBar(
+      content: Text(message),
+      duration: Duration(seconds: delaySeconds),
+    ),
+  );
+}
+
+ScaffoldFeatureController<SnackBar, SnackBarClosedReason> notifyUser(BuildContext context, String message, { int delaySeconds = 3 }) {
+  return notifyUserX(ScaffoldMessenger.of(context), message, delaySeconds: delaySeconds);
+}
+
+Future<ScaffoldFeatureController<SnackBar, SnackBarClosedReason>> postNotifyUser(
+  BuildContext context, String message, {int delaySeconds = 3}) {
+
+  final completer = Completer<ScaffoldFeatureController<SnackBar, SnackBarClosedReason>>();
+
+  WidgetsBinding.instance.addPostFrameCallback((_) {
+    final controller = notifyUser(context, message, delaySeconds: delaySeconds);
+    completer.complete(controller);
+  });
+
+  return completer.future;
+}