reactive/AsyncRx.NET/System.Reactive.Async/System/Reactive/Linq/Operators/Any.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information. 

using System.Threading.Tasks;

namespace System.Reactive.Linq
{
    partial class AsyncObservable
    {
        public static IAsyncObservable<bool> Any<TSource>(this IAsyncObservable<TSource> source)
        {
            if (source == null)
                throw new ArgumentNullException(nameof(source));

            return Create<bool>(observer => source.SubscribeAsync(AsyncObserver.Any<TSource>(observer)));
        }

        public static IAsyncObservable<bool> Any<TSource>(this IAsyncObservable<TSource> source, Func<TSource, bool> predicate)
        {
            if (source == null)
                throw new ArgumentNullException(nameof(source));
            if (predicate == null)
                throw new ArgumentNullException(nameof(predicate));

            return Create<bool>(observer => source.SubscribeAsync(AsyncObserver.Any(observer, predicate)));
        }

        public static IAsyncObservable<bool> Any<TSource>(this IAsyncObservable<TSource> source, Func<TSource, Task<bool>> predicate)
        {
            if (source == null)
                throw new ArgumentNullException(nameof(source));
            if (predicate == null)
                throw new ArgumentNullException(nameof(predicate));

            return Create<bool>(observer => source.SubscribeAsync(AsyncObserver.Any(observer, predicate)));
        }
    }

    partial class AsyncObserver
    {
        public static IAsyncObserver<TSource> Any<TSource>(IAsyncObserver<bool> observer)
        {
            if (observer == null)
                throw new ArgumentNullException(nameof(observer));

            return Create<TSource>(
                async x =>
                {
                    await observer.OnNextAsync(true).ConfigureAwait(false);
                    await observer.OnCompletedAsync().ConfigureAwait(false);
                },
                observer.OnErrorAsync,
                async () =>
                {
                    await observer.OnNextAsync(false).ConfigureAwait(false);
                    await observer.OnCompletedAsync().ConfigureAwait(false);
                }
            );
        }

        public static IAsyncObserver<TSource> Any<TSource>(IAsyncObserver<bool> observer, Func<TSource, bool> predicate)
        {
            if (observer == null)
                throw new ArgumentNullException(nameof(observer));
            if (predicate == null)
                throw new ArgumentNullException(nameof(predicate));

            return Any<TSource>(observer, x => Task.FromResult(predicate(x)));
        }

        public static IAsyncObserver<TSource> Any<TSource>(IAsyncObserver<bool> observer, Func<TSource, Task<bool>> predicate)
        {
            if (observer == null)
                throw new ArgumentNullException(nameof(observer));
            if (predicate == null)
                throw new ArgumentNullException(nameof(predicate));

            return Create<TSource>(
                async x =>
                {
                    var b = default(bool);

                    try
                    {
                        b = await predicate(x).ConfigureAwait(false);
                    }
                    catch (Exception ex)
                    {
                        await observer.OnErrorAsync(ex).ConfigureAwait(false);
                        return;
                    }

                    if (b)
                    {
                        await observer.OnNextAsync(true).ConfigureAwait(false);
                        await observer.OnCompletedAsync().ConfigureAwait(false);
                    }
                },
                observer.OnErrorAsync,
                async () =>
                {
                    await observer.OnNextAsync(false).ConfigureAwait(false);
                    await observer.OnCompletedAsync().ConfigureAwait(false);
                }
            );
        }
    }
}