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

using System;
using System.Buffers;
using System.Linq;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using SixLabors.ImageSharp.ColorSpaces.Companding;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Tests.Common;
using SixLabors.ImageSharp.Tests.TestUtilities;
using Xunit;
using Xunit.Abstractions;

namespace SixLabors.ImageSharp.Tests.PixelFormats.PixelOperations
{
    [Trait("Category", "PixelFormats")]
    public partial class PixelOperationsTests
    {
#pragma warning disable SA1313 // Parameter names should begin with lower-case letter
        [Theory]
        [WithBlankImages(1, 1, PixelTypes.All)]
        public void GetGlobalInstance<T>(TestImageProvider<T> _)
            where T : unmanaged, IPixel<T> => Assert.NotNull(PixelOperations<T>.Instance);
    }
#pragma warning restore SA1313 // Parameter names should begin with lower-case letter

    public abstract class PixelOperationsTests<TPixel> : MeasureFixture
        where TPixel : unmanaged, IPixel<TPixel>
    {
        public const string SkipProfilingBenchmarks =
#if true
            "Profiling benchmark - enable manually!";
#else
                null;
#endif

        protected PixelOperationsTests(ITestOutputHelper output)
            : base(output)
        {
        }

        public static TheoryData<int> ArraySizesData =>
            new TheoryData<int>
                {
                    0,
                    1,
                    2,
                    7,
                    16,
                    512,
                    513,
                    514,
                    515,
                    516,
                    517,
                    518,
                    519,
                    520,
                    521,
                    522,
                    523,
                    524,
                    525,
                    526,
                    527,
                    528,
                    1111
                };

        protected Configuration Configuration => Configuration.Default;

        protected virtual PixelOperations<TPixel> Operations { get; } = PixelOperations<TPixel>.Instance;

        protected bool HasUnassociatedAlpha => this.Operations.GetPixelTypeInfo().AlphaRepresentation == PixelAlphaRepresentation.Unassociated;

        internal static TPixel[] CreateExpectedPixelData(Vector4[] source, RefAction<Vector4> vectorModifier = null)
        {
            var expected = new TPixel[source.Length];

            for (int i = 0; i < expected.Length; i++)
            {
                Vector4 v = source[i];
                vectorModifier?.Invoke(ref v);

                expected[i].FromVector4(v);
            }

            return expected;
        }

        internal static TPixel[] CreateScaledExpectedPixelData(Vector4[] source, RefAction<Vector4> vectorModifier = null)
        {
            var expected = new TPixel[source.Length];

            for (int i = 0; i < expected.Length; i++)
            {
                Vector4 v = source[i];
                vectorModifier?.Invoke(ref v);

                expected[i].FromScaledVector4(v);
            }

            return expected;
        }

        [Fact]
        public void PixelTypeInfoHasCorrectBitsPerPixel()
        {
            var bits = this.Operations.GetPixelTypeInfo().BitsPerPixel;
            Assert.Equal(Unsafe.SizeOf<TPixel>() * 8, bits);
        }

        [Fact]
        public void PixelAlphaRepresentation_DefinesPresenceOfAlphaChannel()
        {
            // We use 0 - 255 as we have pixel formats that store
            // the alpha component in less than 8 bits.
            const byte Alpha = byte.MinValue;
            const byte NoAlpha = byte.MaxValue;

            TPixel pixel = default;
            pixel.FromRgba32(new Rgba32(0, 0, 0, Alpha));

            Rgba32 dest = default;
            pixel.ToRgba32(ref dest);

            bool hasAlpha = this.Operations.GetPixelTypeInfo().AlphaRepresentation != PixelAlphaRepresentation.None;

            byte expectedAlpha = hasAlpha ? Alpha : NoAlpha;
            Assert.Equal(expectedAlpha, dest.A);
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromVector4(int count)
        {
            Vector4[] source = CreateVector4TestData(count);
            TPixel[] expected = CreateExpectedPixelData(source);

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromVector4Destructive(this.Configuration, s, d.GetSpan()));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromScaledVector4(int count)
        {
            Vector4[] source = CreateVector4TestData(count);
            TPixel[] expected = CreateScaledExpectedPixelData(source);

            TestOperation(
                source,
                expected,
                (s, d) =>
                    {
                        Span<TPixel> destPixels = d.GetSpan();
                        this.Operations.FromVector4Destructive(this.Configuration, s, destPixels, PixelConversionModifiers.Scale);
                    });
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromCompandedScaledVector4(int count)
        {
            void SourceAction(ref Vector4 v) => SRgbCompanding.Expand(ref v);

            void ExpectedAction(ref Vector4 v) => SRgbCompanding.Compress(ref v);

            Vector4[] source = CreateVector4TestData(count, (ref Vector4 v) => SourceAction(ref v));
            TPixel[] expected = CreateScaledExpectedPixelData(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromVector4Destructive(
                    this.Configuration,
                    s,
                    d.GetSpan(),
                    PixelConversionModifiers.SRgbCompand | PixelConversionModifiers.Scale),
                false);
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromPremultipliedVector4(int count)
        {
            void SourceAction(ref Vector4 v)
            {
                if (this.HasUnassociatedAlpha)
                {
                    Numerics.Premultiply(ref v);
                }
            }

            void ExpectedAction(ref Vector4 v)
            {
                if (this.HasUnassociatedAlpha)
                {
                    Numerics.UnPremultiply(ref v);
                }
            }

            Vector4[] source = CreateVector4TestData(count, (ref Vector4 v) => SourceAction(ref v));
            TPixel[] expected = CreateExpectedPixelData(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) =>
                {
                    PixelConversionModifiers modifiers = this.HasUnassociatedAlpha
                        ? PixelConversionModifiers.Premultiply
                        : PixelConversionModifiers.None;

                    this.Operations.FromVector4Destructive(this.Configuration, s, d.GetSpan(), modifiers);
                });
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromPremultipliedScaledVector4(int count)
        {
            void SourceAction(ref Vector4 v)
            {
                if (this.HasUnassociatedAlpha)
                {
                    Numerics.Premultiply(ref v);
                }
            }

            void ExpectedAction(ref Vector4 v)
            {
                if (this.HasUnassociatedAlpha)
                {
                    Numerics.UnPremultiply(ref v);
                }
            }

            Vector4[] source = CreateVector4TestData(count, (ref Vector4 v) => SourceAction(ref v));
            TPixel[] expected = CreateScaledExpectedPixelData(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) =>
                {
                    PixelConversionModifiers modifiers = this.HasUnassociatedAlpha
                        ? PixelConversionModifiers.Premultiply
                        : PixelConversionModifiers.None;

                    this.Operations.FromVector4Destructive(
                                        this.Configuration,
                                        s,
                                        d.GetSpan(),
                                        modifiers | PixelConversionModifiers.Scale);
                });
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromCompandedPremultipliedScaledVector4(int count)
        {
            void SourceAction(ref Vector4 v)
            {
                SRgbCompanding.Expand(ref v);

                if (this.HasUnassociatedAlpha)
                {
                    Numerics.Premultiply(ref v);
                }
            }

            void ExpectedAction(ref Vector4 v)
            {
                if (this.HasUnassociatedAlpha)
                {
                    Numerics.UnPremultiply(ref v);
                }

                SRgbCompanding.Compress(ref v);
            }

            Vector4[] source = CreateVector4TestData(count, (ref Vector4 v) => SourceAction(ref v));
            TPixel[] expected = CreateScaledExpectedPixelData(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) =>
                {
                    PixelConversionModifiers modifiers = this.HasUnassociatedAlpha
                        ? PixelConversionModifiers.Premultiply
                        : PixelConversionModifiers.None;

                    this.Operations.FromVector4Destructive(
                                        this.Configuration,
                                        s,
                                        d.GetSpan(),
                                        modifiers | PixelConversionModifiers.SRgbCompand | PixelConversionModifiers.Scale);
                },
                false);
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToVector4(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            Vector4[] expected = CreateExpectedVector4Data(source);

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToVector4(this.Configuration, s, d.GetSpan()));
        }

        public static readonly TheoryData<object> Generic_To_Data = new TheoryData<object>
        {
            new TestPixel<Rgba32>(),
            new TestPixel<Bgra32>(),
            new TestPixel<Rgb24>(),
            new TestPixel<L8>(),
            new TestPixel<L16>(),
            new TestPixel<Rgb48>(),
            new TestPixel<Rgba64>()
        };

        [Theory]
        [MemberData(nameof(Generic_To_Data))]
        public void Generic_To<TDestPixel>(TestPixel<TDestPixel> dummy)
            where TDestPixel : unmanaged, IPixel<TDestPixel>
        {
            const int Count = 2134;
            TPixel[] source = CreatePixelTestData(Count);
            var expected = new TDestPixel[Count];

            PixelConverterTests.ReferenceImplementations.To<TPixel, TDestPixel>(this.Configuration, source, expected);

            TestOperation(source, expected, (s, d) => this.Operations.To(this.Configuration, s, d.GetSpan()));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToScaledVector4(int count)
        {
            TPixel[] source = CreateScaledPixelTestData(count);
            Vector4[] expected = CreateExpectedScaledVector4Data(source);

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToVector4(
                    this.Configuration,
                    s,
                    d.GetSpan(),
                    PixelConversionModifiers.Scale));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToCompandedScaledVector4(int count)
        {
            void SourceAction(ref Vector4 v)
            {
            }

            void ExpectedAction(ref Vector4 v) => SRgbCompanding.Expand(ref v);

            TPixel[] source = CreateScaledPixelTestData(count, (ref Vector4 v) => SourceAction(ref v));
            Vector4[] expected = CreateExpectedScaledVector4Data(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToVector4(
                    this.Configuration,
                    s,
                    d.GetSpan(),
                    PixelConversionModifiers.SRgbCompand | PixelConversionModifiers.Scale));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToPremultipliedVector4(int count)
        {
            void SourceAction(ref Vector4 v)
            {
            }

            void ExpectedAction(ref Vector4 v) => Numerics.Premultiply(ref v);

            TPixel[] source = CreatePixelTestData(count, (ref Vector4 v) => SourceAction(ref v));
            Vector4[] expected = CreateExpectedVector4Data(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToVector4(this.Configuration, s, d.GetSpan(), PixelConversionModifiers.Premultiply));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToPremultipliedScaledVector4(int count)
        {
            void SourceAction(ref Vector4 v)
            {
            }

            void ExpectedAction(ref Vector4 v) => Numerics.Premultiply(ref v);

            TPixel[] source = CreateScaledPixelTestData(count, (ref Vector4 v) => SourceAction(ref v));
            Vector4[] expected = CreateExpectedScaledVector4Data(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToVector4(
                    this.Configuration,
                    s,
                    d.GetSpan(),
                    PixelConversionModifiers.Premultiply | PixelConversionModifiers.Scale));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToCompandedPremultipliedScaledVector4(int count)
        {
            void SourceAction(ref Vector4 v)
            {
            }

            void ExpectedAction(ref Vector4 v)
            {
                SRgbCompanding.Expand(ref v);
                Numerics.Premultiply(ref v);
            }

            TPixel[] source = CreateScaledPixelTestData(count, (ref Vector4 v) => SourceAction(ref v));
            Vector4[] expected = CreateExpectedScaledVector4Data(source, (ref Vector4 v) => ExpectedAction(ref v));

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToVector4(
                    this.Configuration,
                    s,
                    d.GetSpan(),
                    PixelConversionModifiers.SRgbCompand | PixelConversionModifiers.Premultiply | PixelConversionModifiers.Scale));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromArgb32Bytes(int count)
        {
            byte[] source = CreateByteTestData(count * 4);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int i4 = i * 4;

                expected[i].FromArgb32(new Argb32(source[i4 + 1], source[i4 + 2], source[i4 + 3], source[i4 + 0]));
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromArgb32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToArgb32Bytes(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * 4];
            var argb = default(Argb32);

            for (int i = 0; i < count; i++)
            {
                int i4 = i * 4;
                argb.FromScaledVector4(source[i].ToScaledVector4());

                expected[i4] = argb.A;
                expected[i4 + 1] = argb.R;
                expected[i4 + 2] = argb.G;
                expected[i4 + 3] = argb.B;
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToArgb32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromBgr24Bytes(int count)
        {
            byte[] source = CreateByteTestData(count * 3);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int i3 = i * 3;

                expected[i].FromBgr24(new Bgr24(source[i3 + 2], source[i3 + 1], source[i3]));
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromBgr24Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToBgr24Bytes(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * 3];
            var bgr = default(Bgr24);

            for (int i = 0; i < count; i++)
            {
                int i3 = i * 3;
                bgr.FromScaledVector4(source[i].ToScaledVector4());
                expected[i3] = bgr.B;
                expected[i3 + 1] = bgr.G;
                expected[i3 + 2] = bgr.R;
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToBgr24Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromBgra32Bytes(int count)
        {
            byte[] source = CreateByteTestData(count * 4);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int i4 = i * 4;

                expected[i].FromBgra32(new Bgra32(source[i4 + 2], source[i4 + 1], source[i4 + 0], source[i4 + 3]));
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromBgra32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToBgra32Bytes(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * 4];
            var bgra = default(Bgra32);

            for (int i = 0; i < count; i++)
            {
                int i4 = i * 4;
                bgra.FromScaledVector4(source[i].ToScaledVector4());
                expected[i4] = bgra.B;
                expected[i4 + 1] = bgra.G;
                expected[i4 + 2] = bgra.R;
                expected[i4 + 3] = bgra.A;
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToBgra32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromBgra5551Bytes(int count)
        {
            int size = Unsafe.SizeOf<Bgra5551>();
            byte[] source = CreateByteTestData(count * size);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int offset = i * size;

                Bgra5551 bgra = MemoryMarshal.Cast<byte, Bgra5551>(source.AsSpan().Slice(offset, size))[0];
                expected[i].FromBgra5551(bgra);
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromBgra5551Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToBgra5551Bytes(int count)
        {
            int size = Unsafe.SizeOf<Bgra5551>();
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * size];
            Bgra5551 bgra = default;

            for (int i = 0; i < count; i++)
            {
                int offset = i * size;
                bgra.FromScaledVector4(source[i].ToScaledVector4());
                OctetBytes bytes = Unsafe.As<Bgra5551, OctetBytes>(ref bgra);
                expected[offset] = bytes[0];
                expected[offset + 1] = bytes[1];
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToBgra5551Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromL8(int count)
        {
            byte[] sourceBytes = CreateByteTestData(count);
            L8[] source = sourceBytes.Select(b => new L8(b)).ToArray();
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                expected[i].FromL8(source[i]);
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromL8(this.Configuration, s, d.GetSpan()));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToL8(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            var expected = new L8[count];

            for (int i = 0; i < count; i++)
            {
                expected[i].FromScaledVector4(source[i].ToScaledVector4());
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToL8(this.Configuration, s, d.GetSpan()));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromL16(int count)
        {
            L16[] source = CreateVector4TestData(count).Select(v =>
            {
                L16 g = default;
                g.FromVector4(v);
                return g;
            }).ToArray();

            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                expected[i].FromL16(source[i]);
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromL16(this.Configuration, s, d.GetSpan()));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToL16(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            var expected = new L16[count];

            for (int i = 0; i < count; i++)
            {
                expected[i].FromScaledVector4(source[i].ToScaledVector4());
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToL16(this.Configuration, s, d.GetSpan()));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromLa16Bytes(int count)
        {
            int size = Unsafe.SizeOf<La16>();
            byte[] source = CreateByteTestData(count * size);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int offset = i * size;

                La16 la = MemoryMarshal.Cast<byte, La16>(source.AsSpan().Slice(offset, size))[0];
                expected[i].FromLa16(la);
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromLa16Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToLa16Bytes(int count)
        {
            int size = Unsafe.SizeOf<La16>();
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * size];
            La16 la = default;

            for (int i = 0; i < count; i++)
            {
                int offset = i * size;
                la.FromScaledVector4(source[i].ToScaledVector4());
                OctetBytes bytes = Unsafe.As<La16, OctetBytes>(ref la);
                expected[offset] = bytes[0];
                expected[offset + 1] = bytes[1];
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToLa16Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromLa32Bytes(int count)
        {
            int size = Unsafe.SizeOf<La32>();
            byte[] source = CreateByteTestData(count * size);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int offset = i * size;

                La32 la = MemoryMarshal.Cast<byte, La32>(source.AsSpan().Slice(offset, size))[0];
                expected[i].FromLa32(la);
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromLa32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToLa32Bytes(int count)
        {
            int size = Unsafe.SizeOf<La32>();
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * size];
            La32 la = default;

            for (int i = 0; i < count; i++)
            {
                int offset = i * size;
                la.FromScaledVector4(source[i].ToScaledVector4());
                OctetBytes bytes = Unsafe.As<La32, OctetBytes>(ref la);
                expected[offset] = bytes[0];
                expected[offset + 1] = bytes[1];
                expected[offset + 2] = bytes[2];
                expected[offset + 3] = bytes[3];
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToLa32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromRgb24Bytes(int count)
        {
            byte[] source = CreateByteTestData(count * 3);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int i3 = i * 3;

                expected[i].FromRgb24(new Rgb24(source[i3 + 0], source[i3 + 1], source[i3 + 2]));
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromRgb24Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToRgb24Bytes(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * 3];
            var rgb = default(Rgb24);

            for (int i = 0; i < count; i++)
            {
                int i3 = i * 3;
                rgb.FromScaledVector4(source[i].ToScaledVector4());
                expected[i3] = rgb.R;
                expected[i3 + 1] = rgb.G;
                expected[i3 + 2] = rgb.B;
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToRgb24Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromRgba32Bytes(int count)
        {
            byte[] source = CreateByteTestData(count * 4);
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int i4 = i * 4;

                expected[i].FromRgba32(new Rgba32(source[i4 + 0], source[i4 + 1], source[i4 + 2], source[i4 + 3]));
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromRgba32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToRgba32Bytes(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * 4];
            var rgba = default(Rgba32);

            for (int i = 0; i < count; i++)
            {
                int i4 = i * 4;
                rgba.FromScaledVector4(source[i].ToScaledVector4());
                expected[i4] = rgba.R;
                expected[i4 + 1] = rgba.G;
                expected[i4 + 2] = rgba.B;
                expected[i4 + 3] = rgba.A;
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToRgba32Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromRgb48Bytes(int count)
        {
            byte[] source = CreateByteTestData(count * 6);
            Span<byte> sourceSpan = source.AsSpan();
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int i6 = i * 6;
                expected[i].FromRgb48(MemoryMarshal.Cast<byte, Rgb48>(sourceSpan.Slice(i6, 6))[0]);
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromRgb48Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToRgb48Bytes(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * 6];
            Rgb48 rgb = default;

            for (int i = 0; i < count; i++)
            {
                int i6 = i * 6;
                rgb.FromScaledVector4(source[i].ToScaledVector4());
                OctetBytes rgb48Bytes = Unsafe.As<Rgb48, OctetBytes>(ref rgb);
                expected[i6] = rgb48Bytes[0];
                expected[i6 + 1] = rgb48Bytes[1];
                expected[i6 + 2] = rgb48Bytes[2];
                expected[i6 + 3] = rgb48Bytes[3];
                expected[i6 + 4] = rgb48Bytes[4];
                expected[i6 + 5] = rgb48Bytes[5];
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToRgb48Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void FromRgba64Bytes(int count)
        {
            byte[] source = CreateByteTestData(count * 8);
            Span<byte> sourceSpan = source.AsSpan();
            var expected = new TPixel[count];

            for (int i = 0; i < count; i++)
            {
                int i8 = i * 8;
                expected[i].FromRgba64(MemoryMarshal.Cast<byte, Rgba64>(sourceSpan.Slice(i8, 8))[0]);
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.FromRgba64Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void ToRgba64Bytes(int count)
        {
            TPixel[] source = CreatePixelTestData(count);
            byte[] expected = new byte[count * 8];
            Rgba64 rgba = default;

            for (int i = 0; i < count; i++)
            {
                int i8 = i * 8;
                rgba.FromScaledVector4(source[i].ToScaledVector4());
                OctetBytes rgba64Bytes = Unsafe.As<Rgba64, OctetBytes>(ref rgba);
                expected[i8] = rgba64Bytes[0];
                expected[i8 + 1] = rgba64Bytes[1];
                expected[i8 + 2] = rgba64Bytes[2];
                expected[i8 + 3] = rgba64Bytes[3];
                expected[i8 + 4] = rgba64Bytes[4];
                expected[i8 + 5] = rgba64Bytes[5];
                expected[i8 + 6] = rgba64Bytes[6];
                expected[i8 + 7] = rgba64Bytes[7];
            }

            TestOperation(
                source,
                expected,
                (s, d) => this.Operations.ToRgba64Bytes(this.Configuration, s, d.GetSpan(), count));
        }

        [Theory]
        [MemberData(nameof(ArraySizesData))]
        public void PackFromRgbPlanes(int count)
            => SimdUtilsTests.TestPackFromRgbPlanes<TPixel>(
                count,
                (r, g, b, actual) => PixelOperations<TPixel>.Instance.PackFromRgbPlanes(this.Configuration, r, g, b, actual));

        public delegate void RefAction<T1>(ref T1 arg1);

        internal static Vector4[] CreateExpectedVector4Data(TPixel[] source, RefAction<Vector4> vectorModifier = null)
        {
            var expected = new Vector4[source.Length];

            for (int i = 0; i < expected.Length; i++)
            {
                var v = source[i].ToVector4();

                vectorModifier?.Invoke(ref v);

                expected[i] = v;
            }

            return expected;
        }

        internal static Vector4[] CreateExpectedScaledVector4Data(TPixel[] source, RefAction<Vector4> vectorModifier = null)
        {
            var expected = new Vector4[source.Length];

            for (int i = 0; i < expected.Length; i++)
            {
                Vector4 v = source[i].ToScaledVector4();

                vectorModifier?.Invoke(ref v);

                expected[i] = v;
            }

            return expected;
        }

        internal static void TestOperation<TSource, TDest>(
            TSource[] source,
            TDest[] expected,
            Action<TSource[], IMemoryOwner<TDest>> action,
            bool preferExactComparison = true)
            where TSource : struct
            where TDest : struct
        {
            using (var buffers = new TestBuffers<TSource, TDest>(source, expected, preferExactComparison))
            {
                action(buffers.SourceBuffer, buffers.ActualDestBuffer);
                buffers.Verify();
            }
        }

        internal static Vector4[] CreateVector4TestData(int length, RefAction<Vector4> vectorModifier = null)
        {
            var result = new Vector4[length];
            var rnd = new Random(42); // Deterministic random values

            for (int i = 0; i < result.Length; i++)
            {
                Vector4 v = GetScaledVector(rnd);
                vectorModifier?.Invoke(ref v);

                result[i] = v;
            }

            return result;
        }

        internal static TPixel[] CreatePixelTestData(int length, RefAction<Vector4> vectorModifier = null)
        {
            var result = new TPixel[length];

            var rnd = new Random(42); // Deterministic random values

            for (int i = 0; i < result.Length; i++)
            {
                Vector4 v = GetScaledVector(rnd);

                vectorModifier?.Invoke(ref v);

                result[i].FromVector4(v);
            }

            return result;
        }

        internal static TPixel[] CreateScaledPixelTestData(int length, RefAction<Vector4> vectorModifier = null)
        {
            var result = new TPixel[length];

            var rnd = new Random(42); // Deterministic random values

            for (int i = 0; i < result.Length; i++)
            {
                Vector4 v = GetScaledVector(rnd);

                vectorModifier?.Invoke(ref v);

                result[i].FromScaledVector4(v);
            }

            return result;
        }

        internal static byte[] CreateByteTestData(int length, int seed = 42)
        {
            byte[] result = new byte[length];
            var rnd = new Random(seed); // Deterministic random values

            for (int i = 0; i < result.Length; i++)
            {
                result[i] = (byte)rnd.Next(255);
            }

            return result;
        }

        internal static Vector4 GetScaledVector(Random rnd)
            => new Vector4((float)rnd.NextDouble(), (float)rnd.NextDouble(), (float)rnd.NextDouble(), (float)rnd.NextDouble());

        [StructLayout(LayoutKind.Sequential)]
        internal unsafe struct OctetBytes
        {
            public fixed byte Data[8];

            public byte this[int idx]
            {
                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                get
                {
                    ref byte self = ref Unsafe.As<OctetBytes, byte>(ref this);
                    return Unsafe.Add(ref self, idx);
                }
            }
        }

        private class TestBuffers<TSource, TDest> : IDisposable
            where TSource : struct
            where TDest : struct
        {
            public TSource[] SourceBuffer { get; }

            public IMemoryOwner<TDest> ActualDestBuffer { get; }

            public TDest[] ExpectedDestBuffer { get; }

            public bool PreferExactComparison { get; }

            public TestBuffers(TSource[] source, TDest[] expectedDest, bool preferExactComparison = true)
            {
                this.SourceBuffer = source;
                this.ExpectedDestBuffer = expectedDest;
                this.ActualDestBuffer = Configuration.Default.MemoryAllocator.Allocate<TDest>(expectedDest.Length);
                this.PreferExactComparison = preferExactComparison;
            }

            public void Dispose() => this.ActualDestBuffer.Dispose();

            public void Verify()
            {
                int count = this.ExpectedDestBuffer.Length;

                if (typeof(TDest) == typeof(Vector4))
                {
                    Span<Vector4> expected = MemoryMarshal.Cast<TDest, Vector4>(this.ExpectedDestBuffer.AsSpan());
                    Span<Vector4> actual = MemoryMarshal.Cast<TDest, Vector4>(this.ActualDestBuffer.GetSpan());
                    var comparer = new ApproximateFloatComparer(TestEnvironment.Is64BitProcess ? 0.0001F : 0.001F);

                    for (int i = 0; i < count; i++)
                    {
                        Assert.Equal(expected[i], actual[i], comparer);
                    }
                }
                else if (!this.PreferExactComparison && typeof(IPixel).IsAssignableFrom(typeof(TDest)) && IsComplexPixel())
                {
                    Span<TDest> expected = this.ExpectedDestBuffer.AsSpan();
                    Span<TDest> actual = this.ActualDestBuffer.GetSpan();
                    var comparer = new ApproximateFloatComparer(TestEnvironment.Is64BitProcess ? 0.0001F : 0.001F);

                    for (int i = 0; i < count; i++)
                    {
                        Assert.Equal((IPixel)expected[i], (IPixel)actual[i], comparer);
                    }
                }
                else
                {
                    Span<TDest> expected = this.ExpectedDestBuffer.AsSpan();
                    Span<TDest> actual = this.ActualDestBuffer.GetSpan();

                    for (int i = 0; i < count; i++)
                    {
                        Assert.Equal(expected[i], actual[i]);
                    }
                }
            }

            // TODO: We really need a PixelTypeInfo.BitsPerComponent property!!
            private static bool IsComplexPixel()
            {
                switch (default(TDest))
                {
                    case HalfSingle _:
                    case HalfVector2 _:
                    case L16 _:
                    case La32 _:
                    case NormalizedShort2 _:
                    case Rg32 _:
                    case Short2 _:
                        return true;

                    default:
                        return Unsafe.SizeOf<TDest>() > sizeof(int);
                }
            }
        }
    }
}