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

using SixLabors.ImageSharp.Formats.Heif.Av1.Prediction.Inter;
using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
using SixLabors.ImageSharp.Tests.TestUtilities;

namespace SixLabors.ImageSharp.Tests.Formats.Heif.Av1;

/// <summary>
/// Verifies AV1 compound prediction and blending across every hardware-intrinsic tier.
/// </summary>
[Trait("Format", "Avif")]
public class Av1CompoundInterPredictorTests
{
    /// <summary>
    /// Exercises the native vector width, 256-bit and 128-bit paths, and the complete scalar fallback.
    /// </summary>
    private const HwIntrinsics PredictorConfigurations =
        HwIntrinsics.AllowAll | HwIntrinsics.DisableAVX512F | HwIntrinsics.DisableAVX | HwIntrinsics.DisableHWIntrinsic;

    /// <summary>
    /// Verifies rounded 8-bit averaging, scalar tails, and untouched row padding under every SIMD configuration.
    /// </summary>
    [Fact]
    public void ByteAverageMatchesIndependentOracleAcrossIntrinsicWidths()
        => FeatureTestRunner.RunWithHwIntrinsicsFeature(ValidateByteAverage, PredictorConfigurations);

    /// <summary>
    /// Verifies rounded 10/12-bit averaging, scalar tails, and untouched row padding under every SIMD configuration.
    /// </summary>
    [Fact]
    public void HighBitDepthAverageMatchesIndependentOracleAcrossIntrinsicWidths()
        => FeatureTestRunner.RunWithHwIntrinsicsFeature(ValidateHighBitDepthAverage, PredictorConfigurations);

    /// <summary>
    /// Verifies 8-bit distance and per-sample mask blending across every intrinsic width and scalar tail.
    /// </summary>
    [Fact]
    public void ByteSelectableBlendsMatchIndependentOracleAcrossIntrinsicWidths()
        => FeatureTestRunner.RunWithHwIntrinsicsFeature(ValidateByteSelectableBlends, PredictorConfigurations);

    /// <summary>
    /// Verifies 10/12-bit distance and per-sample mask blending across every intrinsic width and scalar tail.
    /// </summary>
    [Fact]
    public void HighBitDepthSelectableBlendsMatchIndependentOracleAcrossIntrinsicWidths()
        => FeatureTestRunner.RunWithHwIntrinsicsFeature(ValidateHighBitDepthSelectableBlends, PredictorConfigurations);

    /// <summary>
    /// Verifies the four smooth inter-intra modes and their complemented destination orientation.
    /// </summary>
    [Fact]
    public void SmoothInterIntraMasksMatchPinnedWeights()
    {
        ReadOnlySpan<byte> weights = [60, 34, 19, 11, 6, 4, 2, 1];

        foreach (Av1InterIntraMode mode in Enum.GetValues<Av1InterIntraMode>())
        {
            const int width = 8;
            const int height = 4;
            const int stride = 11;
            byte[] mask = new byte[stride * height];
            byte[] inverted = new byte[stride * height];
            mask.AsSpan().Fill(0xA5);
            inverted.AsSpan().Fill(0xA5);

            Av1InterIntraMaskBuilder.FillInterIntraMask(mask, stride, width, height, mode, invert: false);
            Av1InterIntraMaskBuilder.FillInterIntraMask(inverted, stride, width, height, mode, invert: true);

            for (int row = 0; row < height; row++)
            {
                for (int column = 0; column < width; column++)
                {
                    byte expected = mode switch
                    {
                        Av1InterIntraMode.Vertical => weights[row],
                        Av1InterIntraMode.Horizontal => weights[column],
                        Av1InterIntraMode.Smooth => weights[Math.Min(row, column)],
                        _ => 32,
                    };

                    Assert.Equal(expected, mask[(row * stride) + column]);
                    Assert.Equal((byte)(64 - expected), inverted[(row * stride) + column]);
                }

                for (int column = width; column < stride; column++)
                {
                    Assert.Equal(0xA5, mask[(row * stride) + column]);
                    Assert.Equal(0xA5, inverted[(row * stride) + column]);
                }
            }
        }
    }

    /// <summary>
    /// Verifies the pinned horizontal curve at the index exercised by a 32-by-16 inter-intra block.
    /// </summary>
    [Fact]
    public void HorizontalInterIntraMaskMatchesPinnedThirtyTwoWideCurve()
    {
        const int width = 32;
        const int height = 16;
        byte[] mask = new byte[width * height];
        byte[] inverted = new byte[width * height];

        Av1InterIntraMaskBuilder.FillInterIntraMask(mask, width, width, height, Av1InterIntraMode.Horizontal, invert: false);
        Av1InterIntraMaskBuilder.FillInterIntraMask(inverted, width, width, height, Av1InterIntraMode.Horizontal, invert: true);

        Assert.Equal(2, mask[23]);
        Assert.Equal(62, inverted[23]);
    }

    /// <summary>
    /// Verifies both difference-mask orientations at each supported bit depth.
    /// </summary>
    [Fact]
    public void DifferenceWeightedMasksMatchPinnedFormula()
        => FeatureTestRunner.RunWithHwIntrinsicsFeature(ValidateDifferenceWeightedMasks, PredictorConfigurations);

    /// <summary>
    /// Applies the pinned difference-mask formula at every bit depth and intrinsic width.
    /// </summary>
    private static void ValidateDifferenceWeightedMasks()
    {
        ReadOnlySpan<int> widths = [9, 16, 23, 32, 47, 64, 127];

        foreach (int width in widths)
        {
            const int height = 3;
            int firstStride = width + 4;
            int secondStride = width + 2;
            int maskStride = width + 3;
            foreach (int bitDepth in new[] { 8, 10, 12 })
            {
                int sampleMask = (1 << bitDepth) - 1;
                ushort[] first = new ushort[firstStride * height];
                ushort[] second = new ushort[secondStride * height];
                for (int row = 0; row < height; row++)
                {
                    for (int column = 0; column < width; column++)
                    {
                        first[(row * firstStride) + column] = (ushort)(((row * 911) + (column * 521)) & sampleMask);
                        second[(row * secondStride) + column] = (ushort)(((row * 307) + (column * 997) + 31) & sampleMask);
                    }
                }

                foreach (Av1DifferenceWeightedMaskType maskType in Enum.GetValues<Av1DifferenceWeightedMaskType>())
                {
                    byte[] actual = new byte[maskStride * height];
                    actual.AsSpan().Fill(0xA5);

                    if (bitDepth == 8)
                    {
                        byte[] firstByte = Array.ConvertAll(first, value => (byte)value);
                        byte[] secondByte = Array.ConvertAll(second, value => (byte)value);
                        Av1DifferenceWeightedMaskBuilder.FillDifferenceWeightedMask(
                            actual,
                            maskStride,
                            firstByte,
                            firstStride,
                            secondByte,
                            secondStride,
                            width,
                            height,
                            maskType);
                    }
                    else
                    {
                        Av1DifferenceWeightedMaskBuilder.FillDifferenceWeightedMask(
                            actual,
                            maskStride,
                            first,
                            firstStride,
                            second,
                            secondStride,
                            width,
                            height,
                            bitDepth,
                            maskType);
                    }

                    for (int row = 0; row < height; row++)
                    {
                        for (int column = 0; column < width; column++)
                        {
                            int difference = Math.Abs(first[(row * firstStride) + column] - second[(row * secondStride) + column]);
                            int alpha = Math.Min(64, 38 + ((difference >> (bitDepth - 8)) / 16));
                            byte expected = (byte)(maskType == Av1DifferenceWeightedMaskType.Type38Inverse ? 64 - alpha : alpha);

                            Assert.Equal(expected, actual[(row * maskStride) + column]);
                        }

                        for (int column = width; column < maskStride; column++)
                        {
                            Assert.Equal(0xA5, actual[(row * maskStride) + column]);
                        }
                    }
                }
            }
        }
    }

    /// <summary>
    /// Applies independent byte arithmetic to block widths that cross every vector and scalar boundary.
    /// </summary>
    private static void ValidateByteAverage()
    {
        ReadOnlySpan<int> widths = [4, 7, 8, 15, 16, 23, 31, 32, 47, 64, 127, 128];

        foreach (int width in widths)
        {
            const int height = 5;
            int destinationStride = width + 11;
            int secondStride = width + 7;
            byte[] expected = new byte[destinationStride * height];
            byte[] actual = new byte[destinationStride * height];
            byte[] scalar = new byte[destinationStride * height];
            byte[] second = new byte[secondStride * height];

            FillByteInputs(expected, second, destinationStride, secondStride, width, height);
            expected.CopyTo(actual, 0);
            expected.CopyTo(scalar, 0);

            for (int row = 0; row < height; row++)
            {
                for (int column = 0; column < width; column++)
                {
                    int destinationIndex = (row * destinationStride) + column;
                    int secondIndex = (row * secondStride) + column;
                    expected[destinationIndex] = (byte)((expected[destinationIndex] + second[secondIndex] + 1) >> 1);
                }
            }

            Av1CompoundAveragePredictor.Average(actual, destinationStride, second, secondStride, width, height);
            Av1CompoundAveragePredictor.AverageScalar(scalar, destinationStride, second, secondStride, width, height);

            Assert.Equal(expected, actual);
            Assert.Equal(expected, scalar);
        }
    }

    /// <summary>
    /// Applies independent ushort arithmetic at both supported high-bit-depth limits.
    /// </summary>
    private static void ValidateHighBitDepthAverage()
    {
        ReadOnlySpan<int> widths = [4, 7, 8, 15, 16, 23, 31, 32, 47, 64, 127, 128];

        foreach (int bitDepth in new[] { 10, 12 })
        {
            foreach (int width in widths)
            {
                const int height = 5;
                int destinationStride = width + 9;
                int secondStride = width + 5;
                ushort[] expected = new ushort[destinationStride * height];
                ushort[] actual = new ushort[destinationStride * height];
                ushort[] scalar = new ushort[destinationStride * height];
                ushort[] second = new ushort[secondStride * height];

                FillHighBitDepthInputs(expected, second, destinationStride, secondStride, width, height, bitDepth);
                expected.CopyTo(actual, 0);
                expected.CopyTo(scalar, 0);

                for (int row = 0; row < height; row++)
                {
                    for (int column = 0; column < width; column++)
                    {
                        int destinationIndex = (row * destinationStride) + column;
                        int secondIndex = (row * secondStride) + column;
                        expected[destinationIndex] = (ushort)((expected[destinationIndex] + second[secondIndex] + 1) >> 1);
                    }
                }

                Av1CompoundAveragePredictor.Average(actual, destinationStride, second, secondStride, width, height);
                Av1CompoundAveragePredictor.AverageScalar(scalar, destinationStride, second, secondStride, width, height);

                Assert.Equal(expected, actual);
                Assert.Equal(expected, scalar);
            }
        }
    }

    /// <summary>
    /// Applies independent byte arithmetic to every selectable compound blend.
    /// </summary>
    private static void ValidateByteSelectableBlends()
    {
        ReadOnlySpan<int> widths = [4, 7, 8, 15, 16, 23, 31, 32, 47, 64, 127, 128];
        ReadOnlySpan<int> distanceWeights = [9, 7, 11, 5, 12, 4, 13, 3];

        foreach (int width in widths)
        {
            const int height = 5;
            int destinationStride = width + 11;
            int secondStride = width + 7;
            int maskStride = width + 5;
            byte[] first = new byte[destinationStride * height];
            byte[] second = new byte[secondStride * height];
            byte[] mask = new byte[maskStride * height];

            FillByteInputs(first, second, destinationStride, secondStride, width, height);
            FillMask(mask, maskStride, width, height);

            for (int weightIndex = 0; weightIndex < distanceWeights.Length; weightIndex += 2)
            {
                byte[] expected = (byte[])first.Clone();
                byte[] actual = (byte[])first.Clone();
                int firstWeight = distanceWeights[weightIndex];
                int secondWeight = distanceWeights[weightIndex + 1];

                for (int row = 0; row < height; row++)
                {
                    for (int column = 0; column < width; column++)
                    {
                        int destinationIndex = (row * destinationStride) + column;
                        int secondIndex = (row * secondStride) + column;
                        expected[destinationIndex] = (byte)(((expected[destinationIndex] * firstWeight) +
                            (second[secondIndex] * secondWeight) + 8) >> 4);
                    }
                }

                Av1CompoundDistanceWeightedPredictor.DistanceWeighted(
                    actual,
                    destinationStride,
                    second,
                    secondStride,
                    width,
                    height,
                    firstWeight,
                    secondWeight);

                Assert.Equal(expected, actual);
            }

            byte[] maskedExpected = (byte[])first.Clone();
            byte[] maskedActual = (byte[])first.Clone();
            for (int row = 0; row < height; row++)
            {
                for (int column = 0; column < width; column++)
                {
                    int destinationIndex = (row * destinationStride) + column;
                    int secondIndex = (row * secondStride) + column;
                    int alpha = mask[(row * maskStride) + column];
                    maskedExpected[destinationIndex] = (byte)(((alpha * maskedExpected[destinationIndex]) +
                        ((64 - alpha) * second[secondIndex]) + 32) >> 6);
                }
            }

            Av1CompoundMaskBlendPredictor.Blend(
                maskedActual,
                destinationStride,
                second,
                secondStride,
                mask,
                maskStride,
                width,
                height);

            Assert.Equal(maskedExpected, maskedActual);
        }
    }

    /// <summary>
    /// Applies independent high-bit-depth arithmetic to every selectable compound blend.
    /// </summary>
    private static void ValidateHighBitDepthSelectableBlends()
    {
        ReadOnlySpan<int> widths = [4, 7, 8, 15, 16, 23, 31, 32, 47, 64, 127, 128];
        ReadOnlySpan<int> distanceWeights = [9, 7, 11, 5, 12, 4, 13, 3];

        foreach (int bitDepth in new[] { 10, 12 })
        {
            foreach (int width in widths)
            {
                const int height = 5;
                int destinationStride = width + 9;
                int secondStride = width + 5;
                int maskStride = width + 3;
                ushort[] first = new ushort[destinationStride * height];
                ushort[] second = new ushort[secondStride * height];
                byte[] mask = new byte[maskStride * height];

                FillHighBitDepthInputs(first, second, destinationStride, secondStride, width, height, bitDepth);
                FillMask(mask, maskStride, width, height);

                for (int weightIndex = 0; weightIndex < distanceWeights.Length; weightIndex += 2)
                {
                    ushort[] expected = (ushort[])first.Clone();
                    ushort[] actual = (ushort[])first.Clone();
                    int firstWeight = distanceWeights[weightIndex];
                    int secondWeight = distanceWeights[weightIndex + 1];

                    for (int row = 0; row < height; row++)
                    {
                        for (int column = 0; column < width; column++)
                        {
                            int destinationIndex = (row * destinationStride) + column;
                            int secondIndex = (row * secondStride) + column;
                            expected[destinationIndex] = (ushort)(((expected[destinationIndex] * firstWeight) +
                                (second[secondIndex] * secondWeight) + 8) >> 4);
                        }
                    }

                    Av1CompoundDistanceWeightedPredictor.DistanceWeighted(
                        actual,
                        destinationStride,
                        second,
                        secondStride,
                        width,
                        height,
                        firstWeight,
                        secondWeight);

                    Assert.Equal(expected, actual);
                }

                ushort[] maskedExpected = (ushort[])first.Clone();
                ushort[] maskedActual = (ushort[])first.Clone();
                for (int row = 0; row < height; row++)
                {
                    for (int column = 0; column < width; column++)
                    {
                        int destinationIndex = (row * destinationStride) + column;
                        int secondIndex = (row * secondStride) + column;
                        int alpha = mask[(row * maskStride) + column];
                        maskedExpected[destinationIndex] = (ushort)(((alpha * maskedExpected[destinationIndex]) +
                            ((64 - alpha) * second[secondIndex]) + 32) >> 6);
                    }
                }

                Av1CompoundMaskBlendPredictor.Blend(
                    maskedActual,
                    destinationStride,
                    second,
                    secondStride,
                    mask,
                    maskStride,
                    width,
                    height);

                Assert.Equal(maskedExpected, maskedActual);
            }
        }
    }

    /// <summary>
    /// Fills active byte samples while assigning different sentinels to the unused row tails.
    /// </summary>
    private static void FillByteInputs(
        Span<byte> destination,
        Span<byte> second,
        int destinationStride,
        int secondStride,
        int width,
        int height)
    {
        destination.Fill(0xD3);
        second.Fill(0xA7);

        for (int row = 0; row < height; row++)
        {
            for (int column = 0; column < width; column++)
            {
                destination[(row * destinationStride) + column] = (byte)((row * 47) + (column * 29) + 3);
                second[(row * secondStride) + column] = (byte)((row * 31) + (column * 53) + 11);
            }
        }
    }

    /// <summary>
    /// Fills active ushort samples across the requested precision while preserving guarded row tails.
    /// </summary>
    private static void FillHighBitDepthInputs(
        Span<ushort> destination,
        Span<ushort> second,
        int destinationStride,
        int secondStride,
        int width,
        int height,
        int bitDepth)
    {
        destination.Fill(0xDEAD);
        second.Fill(0xBEEF);
        int mask = (1 << bitDepth) - 1;

        for (int row = 0; row < height; row++)
        {
            for (int column = 0; column < width; column++)
            {
                destination[(row * destinationStride) + column] = (ushort)(((row * 947) + (column * 613) + 17) & mask);
                second[(row * secondStride) + column] = (ushort)(((row * 541) + (column * 887) + 23) & mask);
            }
        }
    }

    /// <summary>
    /// Fills active mask samples across the complete AV1 alpha range while guarding every row tail.
    /// </summary>
    private static void FillMask(Span<byte> mask, int maskStride, int width, int height)
    {
        mask.Fill(0xA5);
        for (int row = 0; row < height; row++)
        {
            for (int column = 0; column < width; column++)
            {
                mask[(row * maskStride) + column] = (byte)(((row * 19) + (column * 37)) % 65);
            }
        }
    }
}