feat: add presence-gated session leases (#7)

Closes #7

tests/FinalFactory.Rendezvous.Tests/Server/UdpMediatorServiceTests.cs

@@ -1,5 +1,10 @@
 using System.Net;
+using FinalFactory.Rendezvous.Contracts;
+using FinalFactory.Rendezvous.Server.Sessions;
+using FinalFactory.Rendezvous.Server.State;
 using FinalFactory.Rendezvous.Server.Transport;
+using FinalFactory.Rendezvous.Tests.Sessions;
+using FinalFactory.Rendezvous.Tests.State;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 
@@ -7,6 +12,39 @@ namespace FinalFactory.Rendezvous.Tests.Server;
 
 public sealed class UdpMediatorServiceTests
 {
+    [Fact]
+    public void AuthenticatedHostDatagramGatesVisibilityUsingObservedGameplaySocket()
+    {
+        using SessionLeaseFixture fixture = new();
+        RegisterSessionResponse registration = fixture.Register();
+        using UdpMediatorService service = new(
+            Options.Create(new UdpMediatorOptions { ListenAddress = "127.0.0.1", Port = 0 }),
+            NullLogger<UdpMediatorService>.Instance,
+            fixture.Store,
+            fixture.Capabilities);
+        PresenceDatagram presence = new()
+        {
+            MessageType = UdpPresenceMessageType.HostPresence,
+            MediationHandle = registration.HostPresenceHandle,
+            AddressFamily = AddressFamilyKind.Ipv4,
+            LocalAddress = "192.168.1.50",
+            LocalPort = 40_000,
+            Capability = registration.HostPresenceCapability,
+        };
+        IPEndPoint observedGameplaySocket = new(IPAddress.Parse("203.0.113.77"), 51_234);
+        presence.Capability = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA";
+        Assert.Equal(
+            UdpPresenceProcessingResult.HostPresenceRejected,
+            service.ProcessDatagram(RendezvousUdpCodec.Encode(presence), observedGameplaySocket));
+        Assert.Empty(fixture.Browse());
+
+        presence.Capability = registration.HostPresenceCapability;
+        Assert.Equal(
+            UdpPresenceProcessingResult.HostPresenceAccepted,
+            service.ProcessDatagram(RendezvousUdpCodec.Encode(presence), observedGameplaySocket));
+        Assert.Equal(registration.ListingId, Assert.Single(fixture.Browse()).Definition.ListingId);
+    }
+
     [Fact]
     public async Task ServiceBindsAnEphemeralUdpPortAndStopsCleanly()
     {
@@ -16,9 +54,14 @@ public sealed class UdpMediatorServiceTests
             ListenAddress = IPAddress.Loopback.ToString(),
             Port = 0,
         };
+        ManualRendezvousClock clock = new();
+        InMemoryEphemeralRendezvousStore store = new(new EphemeralStoreOptions(), clock, clock);
+        using EphemeralCapabilityIssuer capabilities = new();
         using UdpMediatorService service = new(
             Options.Create(options),
-            NullLogger<UdpMediatorService>.Instance);
+            NullLogger<UdpMediatorService>.Instance,
+            store,
+            capabilities);
 
         await service.StartAsync(timeout.Token);