reactive/AsyncRx.NET/System.Reactive.Async.Linq/System/Reactive/Linq/GroupedAsyncObservable.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT License.
// See the LICENSE file in the project root for more information. 

using System.Reactive.Disposables;
using System.Reactive.Subjects;
using System.Threading.Tasks;

namespace System.Reactive.Linq
{
    internal sealed class GroupedAsyncObservable<TKey, TElement> : AsyncObservableBase<TElement>, IGroupedAsyncObservable<TKey, TElement>
    {
        private readonly IAsyncSubject<TElement> _subject;
        private readonly RefCountAsyncDisposable _disposable;

        public GroupedAsyncObservable(TKey key, IAsyncSubject<TElement> subject, RefCountAsyncDisposable disposable)
        {
            Key = key;
            _subject = subject;
            _disposable = disposable;
        }

        public TKey Key { get; }

        protected override async ValueTask<IAsyncDisposable> SubscribeAsyncCore(IAsyncObserver<TElement> observer)
        {
            if (_disposable != null)
            {
                var d = await _disposable.GetDisposableAsync().ConfigureAwait(false);
                var s = await _subject.SubscribeAsync(observer).ConfigureAwait(false);
                return StableCompositeAsyncDisposable.Create(d, s);
            }

            return await _subject.SubscribeAsync(observer).ConfigureAwait(false);
        }
    }
}