spark/src/DataStreamSuite/DataStream/ObservableViewStream.cs

namespace Bts.DataStream;

using BCG;

using bts;

using System;

public class ObservableViewStream : ViewStream, IObservable<DataPacket>, IDisposable {
   readonly IObservable<DataPacket> source;
   IDisposable? subscription;

   public ObservableViewStream(IObservable<DataPacket> source) =>
      this.source = source;

   public void Dispose() {
      GC.SuppressFinalize(this);
      if (subscription is not null) {
         subscription.Dispose();
         subscription = null;
      }
   }

   protected override void myOnFirstSubscriber() {
      Log.isnull(subscription);
      subscription = source.Subscribe(myFireEvent);
   }

   protected override void myOnLastSubscriber() {
      Log.notnull(subscription);
      subscription.Dispose();
      subscription = null;
   }

   IDisposable IObservable<DataPacket>.Subscribe(IObserver<DataPacket> observer) =>
      source.Subscribe(observer);
}