spark/src/DataStreamSuite/DataStream/ObservableViewStream.cs

namespace Bts.DataStream;

using BCG;

using bts;

using Microsoft.Extensions.Logging;

using System;

public class ObservableViewStream : ViewStream, IObservable<IDataPacket>, IDisposable {
   readonly IObservable<IDataPacket> source;
   readonly string? name;
   readonly ILogger? logger;
   IDisposable? subscription;

   public ObservableViewStream(IObservable<IDataPacket> source, string? name = null, ILogger? logger = null) {
      this.source = source;
      this.name = name;
      this.logger = logger;
   }

   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, OnError, OnCompleted);

      void OnError(Exception exception) =>
         logger?.LogError("Error in ObservableViewStream. name: {Name}, error: {Exception}", name, exception);

      void OnCompleted() =>
         logger?.LogInformation("ObservableViewStream completed. name: {Name}", name);
   }

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

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