// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.

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

using SixLabors.ImageSharp.PixelFormats;

// ReSharper disable InconsistentNaming
namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion
{
    public class PixelConversion_ConvertFromVector4
    {
        [StructLayout(LayoutKind.Sequential)]
        private struct TestRgbaVector : ITestPixel<TestRgbaVector>
        {
            private Vector4 v;

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void FromVector4(Vector4 p)
            {
                this.v = p;
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void FromVector4(ref Vector4 p)
            {
                this.v = p;
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public Vector4 ToVector4() => this.v;

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void CopyToVector4(ref Vector4 dest)
            {
                dest = this.v;
            }

            public void FromRgba32(Rgba32 source) => throw new System.NotImplementedException();

            public void FromRgba32(ref Rgba32 source) => throw new System.NotImplementedException();

            public void FromBytes(byte r, byte g, byte b, byte a) => throw new System.NotImplementedException();

            public Rgba32 ToRgba32() => throw new System.NotImplementedException();

            public void CopyToRgba32(ref Rgba32 dest) => throw new System.NotImplementedException();
        }

        private struct ConversionRunner<T>
            where T : struct, ITestPixel<T>
        {
            private T[] dest;

            private Vector4[] source;

            public ConversionRunner(int count)
            {
                this.dest = new T[count];
                this.source = new Vector4[count];
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void RunByRefConversion()
            {
                int count = this.dest.Length;

                ref T destBaseRef = ref this.dest[0];
                ref Vector4 sourceBaseRef = ref this.source[0];

                for (int i = 0; i < count; i++)
                {
                    Unsafe.Add(ref destBaseRef, i).FromVector4(ref Unsafe.Add(ref sourceBaseRef, i));
                }
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void RunByValConversion()
            {
                int count = this.dest.Length;

                ref T destBaseRef = ref this.dest[0];
                ref Vector4 sourceBaseRef = ref this.source[0];

                for (int i = 0; i < count; i++)
                {
                    Unsafe.Add(ref destBaseRef, i).FromVector4(Unsafe.Add(ref sourceBaseRef, i));
                }
            }
        }

        private ConversionRunner<TestArgb> nonVectorRunner;

        private ConversionRunner<TestRgbaVector> vectorRunner;

        [Params(32)]
        public int Count { get; set; }

        [GlobalSetup]
        public void Setup()
        {
            this.nonVectorRunner = new ConversionRunner<TestArgb>(this.Count);
            this.vectorRunner = new ConversionRunner<TestRgbaVector>(this.Count);
        }

        [Benchmark(Baseline = true)]
        public void VectorByRef()
        {
            this.vectorRunner.RunByRefConversion();
        }

        [Benchmark]
        public void VectorByVal()
        {
            this.vectorRunner.RunByValConversion();
        }

        [Benchmark]
        public void NonVectorByRef()
        {
            this.nonVectorRunner.RunByRefConversion();
        }

        [Benchmark]
        public void NonVectorByVal()
        {
            this.nonVectorRunner.RunByValConversion();
        }
    }

    /*
     * Results:
     *          Method | Count |       Mean |    StdDev | Scaled | Scaled-StdDev |
     * --------------- |------ |----------- |---------- |------- |-------------- |
     *     VectorByRef |    32 | 23.6678 ns | 0.1141 ns |   1.00 |          0.00 |
     *     VectorByVal |    32 | 24.5347 ns | 0.0771 ns |   1.04 |          0.01 |
     *  NonVectorByRef |    32 | 59.0187 ns | 0.2114 ns |   2.49 |          0.01 |
     *  NonVectorByVal |    32 | 58.7529 ns | 0.2545 ns |   2.48 |          0.02 |
     *
     *  !!! Conclusion !!!
     *  We do not need by-ref version of ConvertFromVector4() stuff
     */
}