improve the flag editor warning viewmodel (#3532)

* improve the flag editor warning viewmodel

- no longer creates a new viewmodel every page reload
- fixes an oversight

* stop countdown on unload

* move the viewmodel to a variable

makes everything look cleaner

* remove initialload check

Bloxstrap/UI/Elements/Settings/Pages/FastFlagEditorWarningPage.xaml

@@ -10,6 +10,7 @@
       d:DesignHeight="450" d:DesignWidth="800"
       Scrollable="True"
       Loaded="Page_Loaded"
+      Unloaded="Page_Unloaded"
       Title="FastFlagEditorWarningPage">
 
     <StackPanel VerticalAlignment="Center">

Bloxstrap/UI/Elements/Settings/Pages/FastFlagEditorWarningPage.xaml.cs

@@ -8,25 +8,24 @@ namespace Bloxstrap.UI.Elements.Settings.Pages
     /// </summary>
     public partial class FastFlagEditorWarningPage
     {
-        private bool _initialLoad = false;
+        private FastFlagEditorWarningViewModel _viewModel;
 
         public FastFlagEditorWarningPage()
         {
-            DataContext = new FastFlagEditorWarningViewModel(this);
+            _viewModel = new FastFlagEditorWarningViewModel(this);
+            DataContext = _viewModel;
+
             InitializeComponent();
         }
 
         private void Page_Loaded(object sender, RoutedEventArgs e)
         {
-            // refresh datacontext on page load to reset timer
-
-            if (!_initialLoad)
-            {
-                _initialLoad = true;
-                return;
-            }
+            _viewModel.StartCountdown();
+        }
 
-            DataContext = new FastFlagEditorWarningViewModel(this);
+        private void Page_Unloaded(object sender, RoutedEventArgs e)
+        {
+            _viewModel.StopCountdown();
         }
     }
 }

Bloxstrap/UI/ViewModels/Settings/FastFlagEditorWarningViewModel.cs

@@ -13,6 +13,8 @@ internal class FastFlagEditorWarningViewModel : NotifyPropertyChangedViewModel
     {
         private Page _page;
 
+        private CancellationTokenSource? _cancellationTokenSource;
+
         public string ContinueButtonText { get; set; } = "";
 
         public bool CanContinue { get; set; } = false;
@@ -24,34 +26,57 @@ internal class FastFlagEditorWarningViewModel : NotifyPropertyChangedViewModel
         public FastFlagEditorWarningViewModel(Page page)
         {
             _page = page;
-            DoCountdown();
         }
 
-        private async void DoCountdown()
+        public void StopCountdown()
+        {
+            _cancellationTokenSource?.Cancel();
+            _cancellationTokenSource = null;
+        }
+
+        public void StartCountdown()
+        {
+            StopCountdown();
+
+            _cancellationTokenSource = new CancellationTokenSource();
+            DoCountdown(_cancellationTokenSource.Token);
+        }
+
+        private async void DoCountdown(CancellationToken token)
         {
+            CanContinue = false;
+            OnPropertyChanged(nameof(CanContinue));
+
             for (int i = 10; i > 0; i--)
             {
                 ContinueButtonText = $"({i}) {Strings.Menu_FastFlagEditor_Warning_Continue}";
                 OnPropertyChanged(nameof(ContinueButtonText));
 
-                await Task.Delay(1000);
+                try
+                {
+                    await Task.Delay(1000, token);
+                }
+                catch (TaskCanceledException)
+                {
+                    return;
+                }
             }
 
             ContinueButtonText = Strings.Menu_FastFlagEditor_Warning_Continue;
             OnPropertyChanged(nameof(ContinueButtonText));
 
             CanContinue = true;
             OnPropertyChanged(nameof(CanContinue));
-
-            App.State.Prop.ShowFFlagEditorWarning = false;
-            App.State.Save();
         }
 
         private void Continue()
         {
             if (!CanContinue)
                 return;
 
+            App.State.Prop.ShowFFlagEditorWarning = false;
+            App.State.Save(); // should we be force saving here?
+
             if (Window.GetWindow(_page) is INavigationWindow window)
                 window.Navigate(typeof(FastFlagEditorPage));
         }