private async Task <IEventStream> SubscribeInternalAsync(
IEventDescription eventDescription)
{
await _semaphore.WaitAsync().ConfigureAwait(false);
try
{
if (!_streams.TryGetValue(eventDescription,
out List <InMemoryEventStream> subscribers))
{
subscribers = new List <InMemoryEventStream>();
_streams[eventDescription] = subscribers;
}
var eventMessage = new EventMessage(eventDescription);
var stream = new InMemoryEventStream();
stream.Completed += (s, e) => Unsubscribe(eventMessage, stream);
subscribers.Add(stream);
return(stream);
}
finally
{
_semaphore.Release();
}
}
public async Task <IEventStream> SubscribeAsync(
IEventDescription eventReference)
{
if (eventReference == null)
{
throw new ArgumentNullException(nameof(eventReference));
}
await _semaphore.WaitAsync();
try
{
if (!_streams.TryGetValue(eventReference, out var subscribers))
{
subscribers = new List <InMemoryEventStream>();
_streams[eventReference] = subscribers;
}
var eventMessage = new EventMessage(eventReference);
var stream = new InMemoryEventStream(eventMessage);
stream.Completed += (s, e) => Unsubscribe(eventMessage, stream);
subscribers.Add(stream);
return(stream);
}
finally
{
_semaphore.Release();
}
}
private void Unsubscribe(
IEventMessage message,
InMemoryEventStream stream)
{
_semaphore.Wait();
try
{
if (_streams.TryGetValue(message.Event, out List <InMemoryEventStream> subscribers))
{
subscribers.Remove(stream);
}
}
finally
{
_semaphore.Release();
}
}