fix(core): harden direct session tracking

refs #99

ErsatzTV.Core.Tests/Streaming/DirectStreamSessionTrackerTests.cs

@@ -71,4 +71,28 @@ public class DirectStreamSessionTrackerTests
         sessions.Single().ChannelNumber.ShouldBe("2");
         sessions.Single().StreamingMode.ShouldBe(StreamingMode.HttpLiveStreamingDirect);
     }
+
+    [Test]
+    public void Should_Not_Orphan_Session_When_Last_Registration_Is_Removed_During_Register()
+    {
+        DirectStreamSessionTracker tracker = null;
+        IDisposable existingSession = null;
+
+        tracker = new TestDirectStreamSessionTracker(() => existingSession?.Dispose());
+        existingSession = tracker.Register("1", StreamingMode.TransportStream);
+
+        using IDisposable newSession = tracker.Register("1", StreamingMode.HttpLiveStreamingDirect);
+
+        tracker.IsActive("1").ShouldBeTrue();
+        tracker.GetViewerCount("1").ShouldBe(1);
+
+        IReadOnlyCollection<DirectStreamSession> sessions = tracker.GetActiveSessions("1");
+        sessions.Count.ShouldBe(1);
+        sessions.Single().StreamingMode.ShouldBe(StreamingMode.HttpLiveStreamingDirect);
+    }
+
+    private sealed class TestDirectStreamSessionTracker(Action onRegisteringSession) : DirectStreamSessionTracker
+    {
+        protected override void OnRegisteringSession() => onRegisteringSession();
+    }
 }

ErsatzTV.Core/Streaming/DirectStreamSessionTracker.cs

@@ -15,11 +15,17 @@ public class DirectStreamSessionTracker : IDirectStreamSessionTracker
         ConcurrentDictionary<Guid, DirectStreamSession> channelSessions =
             _sessions.GetOrAdd(channelNumber, _ => new ConcurrentDictionary<Guid, DirectStreamSession>());
 
+        OnRegisteringSession();
+
         channelSessions.TryAdd(session.Id, session);
 
         return new Registration(this, session);
     }
 
+    protected virtual void OnRegisteringSession()
+    {
+    }
+
     public bool IsActive(string channelNumber) => GetViewerCount(channelNumber) > 0;
 
     public int GetViewerCount(string channelNumber) =>
@@ -43,10 +49,6 @@ public class DirectStreamSessionTracker : IDirectStreamSessionTracker
         }
 
         channelSessions.TryRemove(session.Id, out _);
-        if (channelSessions.IsEmpty)
-        {
-            _sessions.TryRemove(session.ChannelNumber, out _);
-        }
     }
 
     private sealed class Registration(DirectStreamSessionTracker tracker, DirectStreamSession session) : IDisposable

ErsatzTV.Tests/Controllers/TrackedFileStreamResultTests.cs

@@ -1,10 +1,12 @@
 using ErsatzTV.Controllers;
 using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Interfaces.Streaming;
 using ErsatzTV.Core.Streaming;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.Extensions.DependencyInjection;
+using NSubstitute;
 using NUnit.Framework;
 using Shouldly;
 
@@ -78,9 +80,27 @@ public class TrackedFileStreamResultTests
         tracker.GetViewerCount("1").ShouldBe(0);
     }
 
-    private static ActionContext GetActionContext()
+    [Test]
+    public async Task Should_Not_Track_Session_For_Head_Request()
+    {
+        IDirectStreamSessionTracker tracker = Substitute.For<IDirectStreamSessionTracker>();
+        var stream = new BlockingReadStream();
+        TrackedFileStreamResult result = new(
+            stream,
+            "video/mp2t",
+            tracker,
+            "1",
+            StreamingMode.TransportStream);
+
+        await result.ExecuteResultAsync(GetActionContext(HttpMethods.Head));
+
+        tracker.DidNotReceive().Register(Arg.Any<string>(), Arg.Any<StreamingMode>());
+    }
+
+    private static ActionContext GetActionContext(string method = "GET")
     {
         var httpContext = new DefaultHttpContext();
+        httpContext.Request.Method = method;
         httpContext.RequestServices = new ServiceCollection()
             .AddLogging()
             .AddControllers()

ErsatzTV/Controllers/TrackedFileStreamResult.cs

@@ -1,5 +1,6 @@
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Interfaces.Streaming;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 
 namespace ErsatzTV.Controllers;
@@ -13,6 +14,12 @@ public class TrackedFileStreamResult(
 {
     public override async Task ExecuteResultAsync(ActionContext context)
     {
+        if (HttpMethods.IsHead(context.HttpContext.Request.Method))
+        {
+            await base.ExecuteResultAsync(context);
+            return;
+        }
+
         using IDisposable registration = directStreamSessionTracker.Register(channelNumber, streamingMode);
 
         await base.ExecuteResultAsync(context);