// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Buffers;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Intrinsics;
using System.Runtime.Intrinsics.X86;
using BenchmarkDotNet.Attributes;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;

// ReSharper disable InconsistentNaming
namespace SixLabors.ImageSharp.Benchmarks.Bulk;

[Config(typeof(Config.ShortCore31))]
public abstract class FromVector4<TPixel>
    where TPixel : unmanaged, IPixel<TPixel>
{
    protected IMemoryOwner<Vector4> source;

    protected IMemoryOwner<TPixel> destination;

    protected Configuration Configuration => Configuration.Default;

    // [Params(64, 2048)]
    [Params(64, 256, 2048)]
    public int Count { get; set; }

    [GlobalSetup]
    public void Setup()
    {
        this.destination = this.Configuration.MemoryAllocator.Allocate<TPixel>(this.Count);
        this.source = this.Configuration.MemoryAllocator.Allocate<Vector4>(this.Count);
    }

    [GlobalCleanup]
    public void Cleanup()
    {
        this.destination.Dispose();
        this.source.Dispose();
    }

    // [Benchmark]
    public void PerElement()
    {
        ref Vector4 s = ref MemoryMarshal.GetReference(this.source.GetSpan());
        ref TPixel d = ref MemoryMarshal.GetReference(this.destination.GetSpan());
        for (nuint i = 0; i < (uint)this.Count; i++)
        {
            Unsafe.Add(ref d, i).FromVector4(Unsafe.Add(ref s, i));
        }
    }

    [Benchmark(Baseline = true)]
    public void PixelOperations_Base()
    {
        new PixelOperations<TPixel>().FromVector4Destructive(this.Configuration, this.source.GetSpan(), this.destination.GetSpan());
    }

    [Benchmark]
    public void PixelOperations_Specialized()
    {
        PixelOperations<TPixel>.Instance.FromVector4Destructive(this.Configuration, this.source.GetSpan(), this.destination.GetSpan());
    }
}

public class FromVector4Rgba32 : FromVector4<Rgba32>
{
    [Benchmark]
    public void FallbackIntrinsics128()
    {
        Span<float> sBytes = MemoryMarshal.Cast<Vector4, float>(this.source.GetSpan());
        Span<byte> dFloats = MemoryMarshal.Cast<Rgba32, byte>(this.destination.GetSpan());

        SimdUtils.FallbackIntrinsics128.NormalizedFloatToByteSaturate(sBytes, dFloats);
    }

    [Benchmark]
    public void ExtendedIntrinsic()
    {
        Span<float> sBytes = MemoryMarshal.Cast<Vector4, float>(this.source.GetSpan());
        Span<byte> dFloats = MemoryMarshal.Cast<Rgba32, byte>(this.destination.GetSpan());

        SimdUtils.ExtendedIntrinsics.NormalizedFloatToByteSaturate(sBytes, dFloats);
    }

    [Benchmark]
    public void UseHwIntrinsics()
    {
        Span<float> sBytes = MemoryMarshal.Cast<Vector4, float>(this.source.GetSpan());
        Span<byte> dFloats = MemoryMarshal.Cast<Rgba32, byte>(this.destination.GetSpan());

        SimdUtils.HwIntrinsics.NormalizedFloatToByteSaturate(sBytes, dFloats);
    }

    private static ReadOnlySpan<byte> PermuteMaskDeinterleave8x32 => new byte[] { 0, 0, 0, 0, 4, 0, 0, 0, 1, 0, 0, 0, 5, 0, 0, 0, 2, 0, 0, 0, 6, 0, 0, 0, 3, 0, 0, 0, 7, 0, 0, 0 };

    [Benchmark]
    public void UseAvx2_Grouped()
    {
        Span<float> src = MemoryMarshal.Cast<Vector4, float>(this.source.GetSpan());
        Span<byte> dest = MemoryMarshal.Cast<Rgba32, byte>(this.destination.GetSpan());

        nuint n = (uint)dest.Length / (uint)Vector<byte>.Count;

        ref Vector256<float> sourceBase = ref Unsafe.As<float, Vector256<float>>(ref MemoryMarshal.GetReference(src));
        ref Vector256<byte> destBase = ref Unsafe.As<byte, Vector256<byte>>(ref MemoryMarshal.GetReference(dest));

        ref byte maskBase = ref MemoryMarshal.GetReference(PermuteMaskDeinterleave8x32);
        Vector256<int> mask = Unsafe.As<byte, Vector256<int>>(ref maskBase);

        var maxBytes = Vector256.Create(255f);

        for (nuint i = 0; i < n; i++)
        {
            ref Vector256<float> s = ref Unsafe.Add(ref sourceBase, i * 4);

            Vector256<float> f0 = s;
            Vector256<float> f1 = Unsafe.Add(ref s, 1);
            Vector256<float> f2 = Unsafe.Add(ref s, 2);
            Vector256<float> f3 = Unsafe.Add(ref s, 3);

            f0 = Avx.Multiply(maxBytes, f0);
            f1 = Avx.Multiply(maxBytes, f1);
            f2 = Avx.Multiply(maxBytes, f2);
            f3 = Avx.Multiply(maxBytes, f3);

            Vector256<int> w0 = Avx.ConvertToVector256Int32(f0);
            Vector256<int> w1 = Avx.ConvertToVector256Int32(f1);
            Vector256<int> w2 = Avx.ConvertToVector256Int32(f2);
            Vector256<int> w3 = Avx.ConvertToVector256Int32(f3);

            Vector256<short> u0 = Avx2.PackSignedSaturate(w0, w1);
            Vector256<short> u1 = Avx2.PackSignedSaturate(w2, w3);
            Vector256<byte> b = Avx2.PackUnsignedSaturate(u0, u1);
            b = Avx2.PermuteVar8x32(b.AsInt32(), mask).AsByte();

            Unsafe.Add(ref destBase, i) = b;
        }
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static Vector256<int> ConvertToInt32(Vector256<float> vf, Vector256<float> scale)
    {
        vf = Avx.Multiply(scale, vf);
        return Avx.ConvertToVector256Int32(vf);
    }

    // *** RESULTS 2020 March: ***
    // Intel Core i7-8650U CPU 1.90GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
    // .NET Core SDK=3.1.200-preview-014971
    //   Job-IUZXZT : .NET Core 3.1.2 (CoreCLR 4.700.20.6602, CoreFX 4.700.20.6702), X64 RyuJIT
    //
    // |                      Method | Count |       Mean |       Error |    StdDev | Ratio | RatioSD | Gen 0 | Gen 1 | Gen 2 | Allocated |
    // |---------------------------- |------ |-----------:|------------:|----------:|------:|--------:|------:|------:|------:|----------:|
    // |       FallbackIntrinsics128 |  1024 | 2,952.6 ns | 1,680.77 ns |  92.13 ns |  3.32 |    0.16 |     - |     - |     - |         - |
    // |          BasicIntrinsics256 |  1024 | 1,664.5 ns |   928.11 ns |  50.87 ns |  1.87 |    0.09 |     - |     - |     - |         - |
    // |           ExtendedIntrinsic |  1024 |   890.6 ns |   375.48 ns |  20.58 ns |  1.00 |    0.00 |     - |     - |     - |         - |
    // |                     UseAvx2 |  1024 |   299.0 ns |    30.47 ns |   1.67 ns |  0.34 |    0.01 |     - |     - |     - |         - |
    // |             UseAvx2_Grouped |  1024 |   318.1 ns |    48.19 ns |   2.64 ns |  0.36 |    0.01 |     - |     - |     - |         - |
    // |        PixelOperations_Base |  1024 | 8,136.9 ns | 1,834.82 ns | 100.57 ns |  9.14 |    0.26 |     - |     - |     - |      24 B |
    // | PixelOperations_Specialized |  1024 |   951.1 ns |   123.93 ns |   6.79 ns |  1.07 |    0.03 |     - |     - |     - |         - |
}