Subscription.cs

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using System;
using System.Threading;
using System.Threading.Tasks;
 
using HotChocolate;
using HotChocolate.Authorization;
using HotChocolate.Execution;
using HotChocolate.Subscriptions;
using HotChocolate.Types;
 
using Tgstation.Server.Host.GraphQL.Subscriptions;
using Tgstation.Server.Host.Security;
 
namespace Tgstation.Server.Host.GraphQL
{
    [Authorize(ApplyPolicy.Validation)] // See https://github.com/ChilliCream/graphql-platform/issues/6259
    [GraphQLDescription(GraphQLDescription)]
    public sealed class Subscription
    {
        public const string GraphQLDescription = "Root Subscription type. Note that subscriptions are performed over Server Sent events.";
 
        public static string SessionInvalidatedTopic(IAuthenticationContext authenticationContext)
        {
            ArgumentNullException.ThrowIfNull(authenticationContext);
            return $"SessionInvalidated.{authenticationContext.SessionId}";
        }
 
        public ValueTask<ISourceStream<SessionInvalidationReason>> SessionInvalidatedStream(
            [Service] HotChocolate.Subscriptions.ITopicEventReceiver receiver, // Intentionally not using our override here, topic callers are built to explicitly handle cases of server shutdown
            [Service] ISessionInvalidationTracker invalidationTracker,
            [Service] IAuthenticationContext authenticationContext,
            CancellationToken cancellationToken)
        {
            ArgumentNullException.ThrowIfNull(receiver);
            ArgumentNullException.ThrowIfNull(invalidationTracker);
 
            var subscription = receiver.SubscribeAsync<SessionInvalidationReason>(SessionInvalidatedTopic(authenticationContext), cancellationToken);
            invalidationTracker.TrackSession(authenticationContext);
            return subscription;
        }
 
        [Subscribe(With = nameof(SessionInvalidatedStream))]
        public SessionInvalidationReason SessionInvalidated([EventMessage] SessionInvalidationReason sessionInvalidationReason)
            => sessionInvalidationReason;
    }
}