// 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;
using System.Runtime.CompilerServices;
using System.Threading;
using CommunityToolkit.HighPerformance.Helpers;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using CommunityToolkit.HighPerformance.UnitTests.Buffers.Internals;

namespace CommunityToolkit.HighPerformance.UnitTests.Helpers;

public partial class Test_ParallelHelper
{
    [TestMethod]
    public unsafe void Test_ParallelHelper_ForEach_In()
    {
        foreach (int count in TestForCounts)
        {
            using UnmanagedSpanOwner<int> data = CreateRandomData(count);

            int sum = 0;

            ParallelHelper.ForEach<int, Summer>(data.Memory, new Summer(&sum));

            int expected = 0;

            foreach (int n in data.GetSpan())
            {
                expected += n;
            }

            Assert.AreEqual(expected, sum, $"The sum doesn't match, was {sum} instead of {expected}");
        }
    }

    /// <summary>
    /// A type implementing <see cref="IInAction{T}"/> to sum array elements.
    /// </summary>
    private readonly unsafe struct Summer : IInAction<int>
    {
        private readonly int* ptr;

        public Summer(int* ptr) => this.ptr = ptr;

        /// <inheritdoc/>
        public void Invoke(in int i) => Interlocked.Add(ref Unsafe.AsRef<int>(this.ptr), i);
    }

    /// <summary>
    /// Creates a random <see cref="int"/> array filled with random numbers.
    /// </summary>
    /// <param name="count">The number of array items to create.</param>
    /// <returns>An array of random <see cref="int"/> elements.</returns>
    private static UnmanagedSpanOwner<int> CreateRandomData(int count)
    {
        Random? random = new(count);

        UnmanagedSpanOwner<int> data = new(count);

        foreach (ref int n in data.GetSpan())
        {
            n = random.Next(0, byte.MaxValue);
        }

        return data;
    }
}