feat: Add UserActivityTracker to monitor user activity

Introduce a new `UserActivityTracker` class in the `SourceGit.Models` namespace to track user activity and determine when to perform auto-fetch operations. Update the `App.axaml.cs` file to initialize the tracker at startup and modify `Repository.cs` to utilize this new functionality, ensuring auto-fetching occurs only during user inactivity.

Author: mpagani

src/App.axaml.cs

@@ -575,6 +575,7 @@ private void TryLaunchAsNormal(IClassicDesktopStyleApplicationLifetime desktop)
 
             _launcher = new ViewModels.Launcher(startupRepo);
             desktop.MainWindow = new Views.Launcher() { DataContext = _launcher };
+            Models.UserActivityTracker.Instance.Initialize();
             desktop.ShutdownMode = ShutdownMode.OnMainWindowClose;
 
 #if !DISABLE_UPDATE_DETECTION

src/Models/UserActivityTracker.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Threading;
+
+namespace SourceGit.Models
+{
+    public class UserActivityTracker
+    {
+        private static readonly Lazy<UserActivityTracker> _instance = new(() => new UserActivityTracker());
+        private bool _isWindowActive = false;
+        private DateTime _lastActivity = DateTime.MinValue;
+        private readonly Lock _lockObject = new();
+        private readonly int _minIdleSecondsBeforeAutoFetch = 15;
+
+        private void OnUserActivity(object sender, EventArgs e) => UpdateLastActivity();
+
+        private void OnWindowActivated(object sender, EventArgs e)
+        {
+            lock (_lockObject)
+            {
+                _isWindowActive = true;
+                _lastActivity = DateTime.Now;
+            }
+        }
+
+        private void OnWindowDeactivated(object sender, EventArgs e)
+        {
+            lock (_lockObject)
+                _isWindowActive = false;
+        }
+
+        public void Initialize()
+        {
+            lock (_lockObject)
+            {
+                _lastActivity = DateTime.Now;
+                _isWindowActive = true;
+            }
+
+            if (App.Current?.ApplicationLifetime is Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime desktop)
+                if (desktop.MainWindow != null)
+                {
+                    desktop.MainWindow.Activated += OnWindowActivated;
+                    desktop.MainWindow.Deactivated += OnWindowDeactivated;
+                    desktop.MainWindow.KeyDown += OnUserActivity;
+                    desktop.MainWindow.PointerPressed += OnUserActivity;
+                    desktop.MainWindow.PointerMoved += OnUserActivity;
+                    desktop.MainWindow.PointerWheelChanged += OnUserActivity;
+                }
+        }
+
+        public bool ShouldPerformAutoFetch(DateTime lastFetchTime, int intervalMinutes)
+        {
+            var now = DateTime.Now;
+
+            if (now < lastFetchTime.AddMinutes(intervalMinutes))
+                return false;
+
+            lock (_lockObject)
+            {
+                if (!_isWindowActive)
+                    return true;
+
+                var timeSinceLastActivity = now - _lastActivity;
+
+                if (timeSinceLastActivity.TotalSeconds >= _minIdleSecondsBeforeAutoFetch)
+                    return true;
+
+                return false;
+            }
+        }
+
+        public void UpdateLastActivity()
+        {
+            lock (_lockObject)
+                _lastActivity = DateTime.Now;
+        }
+
+        public static UserActivityTracker Instance => _instance.Value;
+    }
+}

src/ViewModels/Repository.cs

@@ -3074,9 +3074,7 @@ private async void AutoFetchImpl(object sender)
                 if (File.Exists(lockFile))
                     return;
 
-                var now = DateTime.Now;
-                var desire = _lastFetchTime.AddMinutes(_settings.AutoFetchInterval);
-                if (desire > now)
+                if (!Models.UserActivityTracker.Instance.ShouldPerformAutoFetch(_lastFetchTime, _settings.AutoFetchInterval))
                     return;
 
                 var remotes = new List<string>();