namespace Bts.DataStream;

using BCG;

using Spark.Core.Disposables;

using System;
using System.Reactive.Linq;

public static class DataStreamExtensions {
   public static ViewStream AsViewStream(this IObservable<DataPacket> source) =>
      source as ViewStream ?? new ObservableViewStream(source);

   public static IObservable<DataPacket> AsObservable(this ViewStream source) {
      return source as IObservable<DataPacket> ?? Observable.Create<DataPacket>(Subscribe);

      IDisposable Subscribe(IObserver<DataPacket> observer) {
         source.onChange += OnChange;
         return Disposable.Create(() => source.onChange -= OnChange);

         void OnChange(object? newValue) =>
            observer.OnNext(newValue as DataPacket ?? throw new ArgumentException(
               $"Expected DataPacket, got {newValue?.GetType()}", nameof(newValue)));
      }
   }
}