public async Task SubscribeToUserMessages(Func <User, Task> userMessageHandler)
{
await InternalClient.SubscribeAsync(_settings.UserMessagesTopic);
UserMessageHandler = userMessageHandler;
}
/// <inheritdoc/>
/// <exception cref="ArgumentException"></exception>
public IObservable <MqttApplicationMessageReceivedEventArgs> Connect(string topic)
{
if (string.IsNullOrWhiteSpace(topic))
{
throw new ArgumentException($"'{nameof(topic)}' cannot be null or whitespace", nameof(topic));
}
ThrowIfDisposed();
lock (topicSubscriptionCache)
{
// try get exiting observable for topic
if (!topicSubscriptionCache.TryGetValue(topic, out IObservable <MqttApplicationMessageReceivedEventArgs> observable))
{
// create new observable for topic
observable = Observable
.Create <MqttApplicationMessageReceivedEventArgs>(async observer =>
{
// subscribe to topic
try
{
await InternalClient.SubscribeAsync(topic).ConfigureAwait(false);
}
catch (Exception exception)
{
logger.Error(exception, "Error while maintaining subscribe from topic.");
observer.OnError(exception);
return(Disposable.Empty);
}
// filter all received messages
// and subscribe to messages for this topic
var messageSubscription = applicationMessageReceived
.FilterTopic(topic)
.Subscribe(observer);
return(Disposable.Create(async() =>
{
// clean up subscription when no observer subscribed
lock (topicSubscriptionCache)
{
messageSubscription.Dispose();
topicSubscriptionCache.Remove(topic);
}
try
{
await InternalClient.UnsubscribeAsync(topic).ConfigureAwait(false);
}
catch (ObjectDisposedException) { } // if disposed there is nothing to unsubscribe
catch (Exception exception)
{
logger.Error(exception, "Error while maintaining unsubscribe from topic.");
}
}));
})
.Publish() // publish from on source observable
.RefCount(); // count subscriptions and dispose source observable when no subscription
// save observable for topic
lock (topicSubscriptionCache)
topicSubscriptionCache.Add(topic, observable);
}
return(observable);
}
}
