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

using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using BenchmarkDotNet.Attributes;

using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;

namespace SixLabors.ImageSharp.Benchmarks.Bulk;

[Config(typeof(Config.ShortCore31))]
public class ToVector4_Rgba32 : ToVector4<Rgba32>
{
    [Benchmark]
    public void FallbackIntrinsics128()
    {
        Span<byte> sBytes = MemoryMarshal.Cast<Rgba32, byte>(this.source.GetSpan());
        Span<float> dFloats = MemoryMarshal.Cast<Vector4, float>(this.destination.GetSpan());

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

    [Benchmark]
    public void PixelOperations_Base()
        => new PixelOperations<Rgba32>().ToVector4(
            this.Configuration,
            this.source.GetSpan(),
            this.destination.GetSpan());

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

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

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

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

    // [Benchmark]
    public void ExtendedIntrinsics_BulkConvertByteToNormalizedFloat_2Loops()
    {
        Span<byte> sBytes = MemoryMarshal.Cast<Rgba32, byte>(this.source.GetSpan());
        Span<float> dFloats = MemoryMarshal.Cast<Vector4, float>(this.destination.GetSpan());

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

        ref Vector<byte> sourceBase = ref Unsafe.As<byte, Vector<byte>>(ref MemoryMarshal.GetReference((ReadOnlySpan<byte>)sBytes));
        ref Vector<float> destBase = ref Unsafe.As<float, Vector<float>>(ref MemoryMarshal.GetReference(dFloats));
        ref Vector<uint> destBaseU = ref Unsafe.As<Vector<float>, Vector<uint>>(ref destBase);

        for (nuint i = 0; i < n; i++)
        {
            Vector<byte> b = Unsafe.Add(ref sourceBase, i);

            Vector.Widen(b, out Vector<ushort> s0, out Vector<ushort> s1);
            Vector.Widen(s0, out Vector<uint> w0, out Vector<uint> w1);
            Vector.Widen(s1, out Vector<uint> w2, out Vector<uint> w3);

            ref Vector<uint> d = ref Unsafe.Add(ref destBaseU, i * 4);
            d = w0;
            Unsafe.Add(ref d, 1) = w1;
            Unsafe.Add(ref d, 2) = w2;
            Unsafe.Add(ref d, 3) = w3;
        }

        n = (uint)(dFloats.Length / Vector<float>.Count);
        var scale = new Vector<float>(1f / 255f);

        for (nuint i = 0; i < n; i++)
        {
            ref Vector<float> dRef = ref Unsafe.Add(ref destBase, i);

            var du = Vector.AsVectorInt32(dRef);
            var v = Vector.ConvertToSingle(du);
            v *= scale;

            dRef = v;
        }
    }

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

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

        ref Vector<byte> sourceBase = ref Unsafe.As<byte, Vector<byte>>(ref MemoryMarshal.GetReference((ReadOnlySpan<byte>)sBytes));
        ref Vector<float> destBase = ref Unsafe.As<float, Vector<float>>(ref MemoryMarshal.GetReference(dFloats));
        var scale = new Vector<float>(1f / 255f);

        for (nuint i = 0; i < n; i++)
        {
            Vector<byte> b = Unsafe.Add(ref sourceBase, i);

            Vector.Widen(b, out Vector<ushort> s0, out Vector<ushort> s1);
            Vector.Widen(s0, out Vector<uint> w0, out Vector<uint> w1);
            Vector.Widen(s1, out Vector<uint> w2, out Vector<uint> w3);

            Vector<float> f0 = ConvertToNormalizedSingle(w0, scale);
            Vector<float> f1 = ConvertToNormalizedSingle(w1, scale);
            Vector<float> f2 = ConvertToNormalizedSingle(w2, scale);
            Vector<float> f3 = ConvertToNormalizedSingle(w3, scale);

            ref Vector<float> d = ref Unsafe.Add(ref destBase, i * 4);
            d = f0;
            Unsafe.Add(ref d, 1) = f1;
            Unsafe.Add(ref d, 2) = f2;
            Unsafe.Add(ref d, 3) = f3;
        }
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static Vector<float> ConvertToNormalizedSingle(Vector<uint> u, Vector<float> scale)
    {
        var vi = Vector.AsVectorInt32(u);
        var v = Vector.ConvertToSingle(vi);
        v *= scale;
        return v;
    }

    /*RESULTS (2018 October):

                          Method | Runtime | Count |        Mean |        Error |      StdDev | Scaled | ScaledSD |  Gen 0 | Allocated |
    ---------------------------- |-------- |------ |------------:|-------------:|------------:|-------:|---------:|-------:|----------:|
           FallbackIntrinsics128 |     Clr |    64 |   287.62 ns |     6.026 ns |   0.3405 ns |   1.19 |     0.00 |      - |       0 B |
              BasicIntrinsics256 |     Clr |    64 |   240.83 ns |    10.585 ns |   0.5981 ns |   1.00 |     0.00 |      - |       0 B |
              ExtendedIntrinsics |     Clr |    64 |   168.28 ns |    11.478 ns |   0.6485 ns |   0.70 |     0.00 |      - |       0 B |
            PixelOperations_Base |     Clr |    64 |   334.08 ns |    38.048 ns |   2.1498 ns |   1.39 |     0.01 | 0.0072 |      24 B |
     PixelOperations_Specialized |     Clr |    64 |   255.41 ns |    10.939 ns |   0.6181 ns |   1.06 |     0.00 |      - |       0 B | <--- ceremonial overhead has been minimized!
                                 |         |       |             |              |             |        |          |        |           |
           FallbackIntrinsics128 |    Core |    64 |   183.29 ns |     8.931 ns |   0.5046 ns |   1.32 |     0.00 |      - |       0 B |
              BasicIntrinsics256 |    Core |    64 |   139.18 ns |     7.633 ns |   0.4313 ns |   1.00 |     0.00 |      - |       0 B |
              ExtendedIntrinsics |    Core |    64 |    66.29 ns |    16.366 ns |   0.9247 ns |   0.48 |     0.01 |      - |       0 B |
            PixelOperations_Base |    Core |    64 |   257.75 ns |    16.959 ns |   0.9582 ns |   1.85 |     0.01 | 0.0072 |      24 B |
     PixelOperations_Specialized |    Core |    64 |    90.14 ns |     9.955 ns |   0.5625 ns |   0.65 |     0.00 |      - |       0 B |
                                 |         |       |             |              |             |        |          |        |           |
           FallbackIntrinsics128 |     Clr |  2048 | 5,011.84 ns |   347.991 ns |  19.6621 ns |   1.22 |     0.01 |      - |       0 B |
              BasicIntrinsics256 |     Clr |  2048 | 4,119.35 ns |   720.153 ns |  40.6900 ns |   1.00 |     0.00 |      - |       0 B |
              ExtendedIntrinsics |     Clr |  2048 | 1,195.29 ns |   164.389 ns |   9.2883 ns |!! 0.29 |     0.00 |      - |       0 B | <--- ExtendedIntrinsics rock!
            PixelOperations_Base |     Clr |  2048 | 6,820.58 ns |   823.433 ns |  46.5255 ns |   1.66 |     0.02 |      - |      24 B |
     PixelOperations_Specialized |     Clr |  2048 | 4,203.53 ns |   176.714 ns |   9.9847 ns |   1.02 |     0.01 |      - |       0 B | <--- can't yet detect whether ExtendedIntrinsics are available :(
                                 |         |       |             |              |             |        |          |        |           |
           FallbackIntrinsics128 |    Core |  2048 | 5,017.89 ns | 4,021.533 ns | 227.2241 ns |   1.24 |     0.05 |      - |       0 B |
              BasicIntrinsics256 |    Core |  2048 | 4,046.51 ns | 1,150.390 ns |  64.9992 ns |   1.00 |     0.00 |      - |       0 B |
              ExtendedIntrinsics |    Core |  2048 | 1,130.59 ns |   832.588 ns |  47.0427 ns |!! 0.28 |     0.01 |      - |       0 B | <--- ExtendedIntrinsics rock!
            PixelOperations_Base |    Core |  2048 | 6,752.68 ns |   272.820 ns |  15.4148 ns |   1.67 |     0.02 |      - |      24 B |
     PixelOperations_Specialized |    Core |  2048 | 1,126.13 ns |    79.192 ns |   4.4745 ns |!! 0.28 |     0.00 |      - |       0 B | <--- ExtendedIntrinsics rock!
     */
}