namespace ErsatzTV.Infrastructure;

public static class AsyncEnumerable
{
    /// <summary>
    ///     Creates an <see cref="IAsyncEnumerable{T}" /> which yields no results, similar to
    ///     <see cref="Enumerable.Empty{TResult}" />.
    /// </summary>
    public static IAsyncEnumerable<T> Empty<T>() => EmptyAsyncEnumerator<T>.Instance;

    private class EmptyAsyncEnumerator<T> : IAsyncEnumerator<T>, IAsyncEnumerable<T>
    {
        public static readonly EmptyAsyncEnumerator<T> Instance = new();

        public IAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
        {
            cancellationToken.ThrowIfCancellationRequested();
            return this;
        }

        public T Current => default;
        public ValueTask DisposeAsync() => default;

        public ValueTask<bool> MoveNextAsync() => new(false);
    }
}