feat: move mainwindow to core and add NavigationService

GSS2.UI.Core/MainWindow.axaml

@@ -0,0 +1,13 @@
+<Window
+    x:Class="GSS2.UI.Core.MainWindow"
+    xmlns="https://github.com/avaloniaui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    xmlns:vm="using:GSS2.UI.Core.ViewModels"
+    Title="{Binding Title}"
+    x:DataType="vm:MainWindowViewModel">
+
+    <ContentControl x:Name="MainContent" />
+
+</Window>

GSS2.UI.Core/MainWindow.axaml.cs

@@ -0,0 +1,16 @@
+using Avalonia.Controls;
+
+namespace GSS2.UI.Core;
+
+public partial class MainWindow : Window
+{
+    public MainWindow()
+    {
+        InitializeComponent();
+    }
+
+    public void SetControl(UserControl control)
+    {
+        MainContent.Content = control;
+    }
+}

GSS2.UI.Core/Services/NavigateService.cs

@@ -0,0 +1,59 @@
+
+using Avalonia.Controls;
+using Avalonia.Controls.ApplicationLifetimes;
+
+namespace GSS2.UI.Core.Services;
+
+public class NavigationService
+{
+    private readonly Stack<UserControl> _navigateControls = new Stack<UserControl>();
+    private readonly IApplicationLifetime? _applicationLifetime;
+
+    public NavigationService(IApplicationLifetime? applicationLifetime)
+    {
+        _applicationLifetime = applicationLifetime;
+    }
+
+    public void NavigateTo(UserControl control)
+    {
+        _navigateControls.Push(control);
+
+        switch (_applicationLifetime)
+        {
+            case IClassicDesktopStyleApplicationLifetime desktop
+                when desktop.MainWindow is MainWindow mainWindow:
+
+                mainWindow.SetControl(control);
+                break;
+
+            case ISingleViewApplicationLifetime singleView:
+                singleView.MainView = control;
+                break;
+        }
+    }
+
+    public void NavigateBack()
+    {
+        if (_navigateControls.Count <= 1)
+            return;
+
+        var lastControl = _navigateControls.Pop();
+        var control = _navigateControls.Peek();
+
+        switch (_applicationLifetime)
+        {
+            case IClassicDesktopStyleApplicationLifetime desktop
+                when desktop.MainWindow is MainWindow mainWindow:
+
+                mainWindow.SetControl(control);
+                break;
+
+            case ISingleViewApplicationLifetime singleView:
+                singleView.MainView = control;
+                break;
+        }
+
+        if (lastControl is IDisposable disposable)
+            disposable.Dispose();
+    }
+}