Fix notification activation and calendar bootstrap flow

Wino.Mail.WinUI/Activation/AppNotificationActivationBuffer.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Windows.AppNotifications;
+
+namespace Wino.Mail.WinUI.Activation;
+
+internal sealed record BufferedAppNotificationActivation(string Argument, IReadOnlyDictionary<string, string>? UserInput);
+
+internal sealed class AppNotificationActivationBuffer
+{
+    private readonly ConcurrentQueue<BufferedAppNotificationActivation> _pendingActivations = new();
+    private readonly SemaphoreSlim _pendingSignal = new(0);
+
+    public void Enqueue(AppNotificationActivatedEventArgs args)
+    {
+        var copiedUserInput = args.UserInput == null
+            ? null
+            : new Dictionary<string, string>(args.UserInput, StringComparer.Ordinal);
+
+        _pendingActivations.Enqueue(new BufferedAppNotificationActivation(args.Argument, copiedUserInput));
+        _pendingSignal.Release();
+    }
+
+    public bool TryDequeue(out BufferedAppNotificationActivation activation)
+        => _pendingActivations.TryDequeue(out activation!);
+
+    public async Task<BufferedAppNotificationActivation?> WaitAsync(TimeSpan timeout, CancellationToken cancellationToken = default)
+    {
+        if (!_pendingActivations.IsEmpty && TryDequeue(out var queuedActivation))
+            return queuedActivation;
+
+        if (!await _pendingSignal.WaitAsync(timeout, cancellationToken))
+            return null;
+
+        return TryDequeue(out var activation) ? activation : null;
+    }
+}