Stabilize Go Live cross-tab session sync

Author: KSemenenko

src/PrompterOne.Shared/AppShell/Services/GoLiveSessionService.CrossTab.cs

@@ -2,8 +2,15 @@ namespace PrompterOne.Shared.Services;
 
 internal sealed partial class GoLiveSessionService
 {
+    private static readonly TimeSpan[] StateRequestCatchUpDelays =
+    [
+        TimeSpan.FromMilliseconds(250),
+        TimeSpan.FromMilliseconds(750)
+    ];
+
     private readonly SemaphoreSlim _crossTabStartGate = new(1, 1);
 
+    private CancellationTokenSource? _stateRequestCatchUpCancellationTokenSource;
     private bool _crossTabReady;
     private bool _disposed;
     private bool _stateRequestPublished;
@@ -22,6 +29,21 @@ public async Task StartCrossTabSyncAsync(CancellationToken cancellationToken = d
     }
 
     public async Task RequestCrossTabStateAsync(CancellationToken cancellationToken = default)
+    {
+        await PublishCrossTabStateRequestAsync(cancellationToken);
+        ScheduleCrossTabStateCatchUpRequests();
+    }
+
+    public async Task RequestCrossTabStateCatchUpAsync(CancellationToken cancellationToken = default)
+    {
+        foreach (var delay in StateRequestCatchUpDelays)
+        {
+            await Task.Delay(delay, cancellationToken);
+            await PublishCrossTabStateRequestAsync(cancellationToken);
+        }
+    }
+
+    private async Task PublishCrossTabStateRequestAsync(CancellationToken cancellationToken = default)
     {
         await EnsureCrossTabReadyAsync(cancellationToken);
         await _crossTabMessageBus.PublishAsync(
@@ -38,10 +60,38 @@ public void Dispose()
         }
 
         _disposed = true;
+        _stateRequestCatchUpCancellationTokenSource?.Cancel();
+        _stateRequestCatchUpCancellationTokenSource?.Dispose();
+        _stateRequestCatchUpCancellationTokenSource = null;
         _crossTabMessageBus.MessageReceived -= HandleCrossTabMessageAsync;
         _crossTabStartGate.Dispose();
     }
 
+    private void ScheduleCrossTabStateCatchUpRequests()
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        _stateRequestCatchUpCancellationTokenSource?.Cancel();
+        _stateRequestCatchUpCancellationTokenSource?.Dispose();
+        _stateRequestCatchUpCancellationTokenSource = new CancellationTokenSource();
+
+        _ = RequestCrossTabStateCatchUpInBackgroundAsync(_stateRequestCatchUpCancellationTokenSource.Token);
+    }
+
+    private async Task RequestCrossTabStateCatchUpInBackgroundAsync(CancellationToken cancellationToken)
+    {
+        try
+        {
+            await RequestCrossTabStateCatchUpAsync(cancellationToken);
+        }
+        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
+        {
+        }
+    }
+
     private async Task EnsureCrossTabReadyAsync(CancellationToken cancellationToken)
     {
         if (_crossTabReady)

tests/PrompterOne.Web.Tests/GoLive/GoLiveCrossTabTests.cs

@@ -91,6 +91,27 @@ public async Task GoLiveSessionService_RequestCrossTabStateAsync_PublishesRepeat
         Assert.Equal(2, requestMessages.Count);
     }
 
+    [Test]
+    public async Task GoLiveSessionService_RequestCrossTabStateCatchUpAsync_RepeatsStateRequests()
+    {
+        var harness = TestHarnessFactory.Create(this);
+        var service = Services.GetRequiredService<GoLiveSessionService>();
+
+        var publishCountBeforeCatchUp = harness.JsRuntime.InvocationRecords.Count(record =>
+            string.Equals(record.Identifier, CrossTabInteropMethodNames.Publish, StringComparison.Ordinal));
+
+        await service.RequestCrossTabStateCatchUpAsync();
+
+        var catchUpRequests = harness.JsRuntime.InvocationRecords
+            .Skip(publishCountBeforeCatchUp)
+            .Where(record => string.Equals(record.Identifier, CrossTabInteropMethodNames.Publish, StringComparison.Ordinal))
+            .Select(record => Assert.IsType<CrossTabMessageEnvelope>(record.Arguments[1]))
+            .Where(message => string.Equals(message.MessageType, CrossTabMessageTypes.GoLiveSessionRequested, StringComparison.Ordinal))
+            .ToList();
+
+        Assert.Equal(2, catchUpRequests.Count);
+    }
+
     [Test]
     public async Task MainLayout_UpdatesGoLiveIndicator_WhenAnotherTabChangesGoLiveSessionState()
     {