// 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.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

namespace System.Linq
{
    public static partial class AsyncEnumerable
    {
#if INCLUDE_SYSTEM_LINQ_ASYNCENUMERABLE_DUPLICATES
        // https://learn.microsoft.com/en-us/dotnet/api/system.linq.asyncenumerable.anyasync?view=net-9.0-pp#system-linq-asyncenumerable-anyasync-1(system-collections-generic-iasyncenumerable((-0))-system-threading-cancellationtoken)
        /// <summary>
        /// Determines whether an async-enumerable sequence contains any elements.
        /// </summary>
        /// <typeparam name="TSource">The type of the elements in the source sequence.</typeparam>
        /// <param name="source">An async-enumerable sequence to check for non-emptiness.</param>
        /// <param name="cancellationToken">The optional cancellation token to be used for cancelling the sequence at any time.</param>
        /// <returns>An async-enumerable sequence containing a single element determining whether the source sequence contains any elements.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="source"/> is null.</exception>
        /// <remarks>The return type of this operator differs from the corresponding operator on IEnumerable in order to retain asynchronous behavior.</remarks>
        public static ValueTask<bool> AnyAsync<TSource>(this IAsyncEnumerable<TSource> source, CancellationToken cancellationToken = default)
        {
            if (source == null)
                throw Error.ArgumentNull(nameof(source));

            return Core(source, cancellationToken);

            static async ValueTask<bool> Core(IAsyncEnumerable<TSource> source, CancellationToken cancellationToken)
            {
                await using var e = source.GetConfiguredAsyncEnumerator(cancellationToken, false);

                return await e.MoveNextAsync();
            }
        }

        // https://learn.microsoft.com/en-us/dotnet/api/system.linq.asyncenumerable.anyasync?view=net-9.0-pp#system-linq-asyncenumerable-anyasync-1(system-collections-generic-iasyncenumerable((-0))-system-func((-0-system-boolean))-system-threading-cancellationtoken)

        /// <summary>
        /// Determines whether any element of an async-enumerable sequence satisfies a condition.
        /// </summary>
        /// <typeparam name="TSource">The type of the elements in the source sequence.</typeparam>
        /// <param name="source">An async-enumerable sequence whose elements to apply the predicate to.</param>
        /// <param name="predicate">A function to test each element for a condition.</param>
        /// <param name="cancellationToken">The optional cancellation token to be used for cancelling the sequence at any time.</param>
        /// <returns>An async-enumerable sequence containing a single element determining whether any elements in the source sequence pass the test in the specified predicate.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="source"/> or <paramref name="predicate"/> is null.</exception>
        /// <remarks>The return type of this operator differs from the corresponding operator on IEnumerable in order to retain asynchronous behavior.</remarks>
        public static ValueTask<bool> AnyAsync<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken = default)
        {
            if (source == null)
                throw Error.ArgumentNull(nameof(source));
            if (predicate == null)
                throw Error.ArgumentNull(nameof(predicate));

            return Core(source, predicate, cancellationToken);

            static async ValueTask<bool> Core(IAsyncEnumerable<TSource> source, Func<TSource, bool> predicate, CancellationToken cancellationToken)
            {
                await foreach (var item in source.WithCancellation(cancellationToken).ConfigureAwait(false))
                {
                    if (predicate(item))
                    {
                        return true;
                    }
                }

                return false;
            }
        }
#endif // INCLUDE_SYSTEM_LINQ_ASYNCENUMERABLE_DUPLICATES

        /// <summary>
        /// Determines whether any element in an async-enumerable sequence satisfies a condition.
        /// </summary>
        /// <typeparam name="TSource">The type of element in the sequence.</typeparam>
        /// <param name="source">An async-enumerable sequence whose elements to apply the predicate to.</param>
        /// <param name="predicate">An asynchronous predicate to apply to each element of the source sequence.</param>
        /// <param name="cancellationToken">An optional cancellation token to be used for cancelling the sequence at any time.</param>
        /// <returns>A ValueTask containing a value indicating whether any elements in the source sequence pass the test in the specified predicate.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="source"/> or <paramref name="predicate"/> is <see langword="null"/>.</exception>
        /// <remarks>The return type of this operator differs from the corresponding operator on IEnumerable in order to retain asynchronous behavior.</remarks>
        [GenerateAsyncOverload]
        [Obsolete("Use AnyAsync. IAsyncEnumerable LINQ is now in System.Linq.AsyncEnumerable, and the AnyAwaitAsync functionality now exists as overloads of AnyAsync.")]
        private static ValueTask<bool> AnyAwaitAsyncCore<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<bool>> predicate, CancellationToken cancellationToken = default)
        {
            if (source == null)
                throw Error.ArgumentNull(nameof(source));
            if (predicate == null)
                throw Error.ArgumentNull(nameof(predicate));

            return Core(source, predicate, cancellationToken);

            static async ValueTask<bool> Core(IAsyncEnumerable<TSource> source, Func<TSource, ValueTask<bool>> predicate, CancellationToken cancellationToken)
            {
                await foreach (var item in source.WithCancellation(cancellationToken).ConfigureAwait(false))
                {
                    if (await predicate(item).ConfigureAwait(false))
                    {
                        return true;
                    }
                }

                return false;
            }
        }

#if !NO_DEEP_CANCELLATION
        [GenerateAsyncOverload]
        [Obsolete("Use AnyAsync. IAsyncEnumerable LINQ is now in System.Linq.AsyncEnumerable, and the AnyAwaitWithCancellationAsync functionality now exists as overloads of AnyAsync.")]
        internal static ValueTask<bool> AnyAwaitWithCancellationAsyncCore<TSource>(this IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<bool>> predicate, CancellationToken cancellationToken = default)
        {
            if (source == null)
                throw Error.ArgumentNull(nameof(source));
            if (predicate == null)
                throw Error.ArgumentNull(nameof(predicate));

            return Core(source, predicate, cancellationToken);

            static async ValueTask<bool> Core(IAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, ValueTask<bool>> predicate, CancellationToken cancellationToken)
            {
                await foreach (var item in source.WithCancellation(cancellationToken).ConfigureAwait(false))
                {
                    if (await predicate(item, cancellationToken).ConfigureAwait(false))
                    {
                        return true;
                    }
                }

                return false;
            }
        }
#endif
    }
}