public static Task <T> ReceiveAsync <T>(this IMessageBus bus,
ISubscriber subscriber,
string cursor,
CancellationToken cancel,
int maxMessages,
Func <MessageResult, T> map,
Action <MessageResult, T> end) where T : class
{
var tcs = new TaskCompletionSource <T>();
IDisposable subscription = null;
var disposer = new Disposer();
int resultSet = 0;
var result = default(T);
var registration = default(CancellationTokenRegistration);
try
{
registration = cancel.Register(disposer.Dispose);
}
catch (ObjectDisposedException)
{
// Dispose immediately
disposer.Dispose();
}
try
{
subscription = bus.Subscribe(subscriber, cursor, messageResult =>
{
// Mark the flag as set so we only set the result once
if (Interlocked.Exchange(ref resultSet, 1) == 0)
{
result = map(messageResult);
// Dispose of the cancellation token subscription
registration.Dispose();
// Dispose the subscription
disposer.Dispose();
}
if (messageResult.Terminal)
{
Interlocked.CompareExchange(ref result, map(messageResult), null);
// Fire a callback before the result is set
end(messageResult, result);
// Set the result
tcs.TrySetResult(result);
}
return(TaskAsyncHelper.False);
},
maxMessages);
}
catch (Exception ex)
{
tcs.TrySetException(ex);
registration.Dispose();
return(tcs.Task);
}
// Set the disposable
disposer.Set(subscription);
return(tcs.Task);
}