add CloseConfirmationDialog

src/KeyKeeper/Views/CloseConfirmationDialog.axaml

@@ -1,12 +1,28 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+<Window xmlns="https://github.com/avaloniaui"
+        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        x:Class="KeyKeeper.Views.CloseConfirmationDialog"
+        Width="420"
+        Height="170"
+        CanResize="False"
+        WindowStartupLocation="CenterOwner"
+        Title="Confirm close"
+        Background="White">
+    <Grid Margin="16" RowDefinitions="*,Auto">
+        <TextBlock Text="Save changes before closing the storage?"
+                   TextWrapping="Wrap"
+                   FontSize="16"/>
 
-namespace KeyKeeper.Views
-{
-    class CloseConfirmationDialog
-    {
-    }
-}
+        <StackPanel Grid.Row="1"
+                    Orientation="Horizontal"
+                    HorizontalAlignment="Right"
+                    Spacing="8"
+                    Margin="0,16,0,0">
+            <Button Content="Save"
+                    Click="Save_Click" />
+            <Button Content="Do not save"
+                    Click="Discard_Click" />
+            <Button Content="Cancel"
+                    Click="Cancel_Click" />
+        </StackPanel>
+    </Grid>
+</Window>

src/KeyKeeper/Views/CloseConfirmationDialog.axaml.cs

@@ -1,12 +1,52 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using Avalonia.Controls;
+using Avalonia.Interactivity;
 
-namespace KeyKeeper.Views
+namespace KeyKeeper.Views;
+
+public enum CloseConfirmationResult
 {
-    internal class CloseConfirmationDialog
-    {
-    }
+    Save,
+    Discard,
+    Cancel,
 }
+
+public partial class CloseConfirmationDialog : Window
+{
+    private bool closingWithResult;
+
+    public CloseConfirmationDialog()
+    {
+        InitializeComponent();
+    }
+
+    protected override void OnClosing(WindowClosingEventArgs e)
+    {
+        if (!closingWithResult)
+        {
+            e.Cancel = true;
+            closingWithResult = true;
+            Close(CloseConfirmationResult.Cancel);
+            return;
+        }
+
+        base.OnClosing(e);
+    }
+
+    private void Save_Click(object? sender, RoutedEventArgs e)
+    {
+        closingWithResult = true;
+        Close(CloseConfirmationResult.Save);
+    }
+
+    private void Discard_Click(object? sender, RoutedEventArgs e)
+    {
+        closingWithResult = true;
+        Close(CloseConfirmationResult.Discard);
+    }
+
+    private void Cancel_Click(object? sender, RoutedEventArgs e)
+    {
+        closingWithResult = true;
+        Close(CloseConfirmationResult.Cancel);
+    }
+}