using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;

namespace Ryujinx.Graphics.Texture.Astc
{
    // https://github.com/GammaUNC/FasTC/blob/master/ASTCEncoder/src/Decompressor.cpp
    public static class AstcDecoder
    {
        struct TexelWeightParams
        {
            public int  Width;
            public int  Height;
            public bool DualPlane;
            public int  MaxWeight;
            public bool Error;
            public bool VoidExtentLdr;
            public bool VoidExtentHdr;

            public int GetPackedBitSize()
            {
                // How many indices do we have?
                int indices = Height * Width;

                if (DualPlane)
                {
                    indices *= 2;
                }

                IntegerEncoded intEncoded = IntegerEncoded.CreateEncoding(MaxWeight);

                return intEncoded.GetBitLength(indices);
            }

            public int GetNumWeightValues()
            {
                int ret = Width * Height;

                if (DualPlane)
                {
                    ret *= 2;
                }

                return ret;
            }
        }

        public static bool TryDecodeToRgba8(
            Span<byte>     data,
            int            blockWidth,
            int            blockHeight,
            int            blockDepth,
            int            width,
            int            height,
            int            depth,
            int            levels,
            out Span<byte> decoded)
        {
            bool success = true;

            using (MemoryStream inputStream = new MemoryStream(data.ToArray()))
            {
                BinaryReader binReader = new BinaryReader(inputStream);

                if (blockWidth > 12 || blockHeight > 12)
                {
                    throw new AstcDecoderException("Invalid block size.");
                }

                if (blockDepth != 1 || depth != 1)
                {
                    // TODO: Support 3D textures.
                    throw new NotImplementedException("3D compressed textures are not unsupported.");
                }

                using (MemoryStream outputStream = new MemoryStream())
                {
                    int blockIndex = 0;

                    int mipOffset = 0;

                    for (int l = 0; l < levels; l++)
                    {
                        for (int j = 0; j < height; j += blockHeight)
                        for (int i = 0; i < width;  i += blockWidth)
                        {
                            int[] decompressedData = new int[144];

                            try
                            {
                                DecompressBlock(binReader.ReadBytes(0x10), decompressedData, blockWidth, blockHeight);
                            }
                            catch (Exception)
                            {
                                success = false;
                            }

                            int decompressedWidth  = Math.Min(blockWidth,  width  - i);
                            int decompressedHeight = Math.Min(blockHeight, height - j);

                            int baseOffset = mipOffset + (j * width + i) * 4;

                            for (int jj = 0; jj < decompressedHeight; jj++)
                            {
                                outputStream.Seek(baseOffset + jj * width * 4, SeekOrigin.Begin);

                                byte[] outputBuffer = new byte[decompressedData.Length * sizeof(int)];

                                Buffer.BlockCopy(decompressedData, 0, outputBuffer, 0, outputBuffer.Length);

                                outputStream.Write(outputBuffer, jj * blockWidth * 4, decompressedWidth * 4);
                            }

                            blockIndex++;
                        }

                        mipOffset += width * height * 4;

                        width  = Math.Max(1, width  >> 1);
                        height = Math.Max(1, height >> 1);
                    }

                    decoded = outputStream.ToArray();
                }
            }

            return success;
        }

        public static bool DecompressBlock(
            byte[] inputBuffer,
            int[]  outputBuffer,
            int    blockWidth,
            int    blockHeight)
        {
            BitArrayStream    bitStream   = new BitArrayStream(new BitArray(inputBuffer));
            TexelWeightParams texelParams = DecodeBlockInfo(bitStream);

            if (texelParams.Error)
            {
                throw new AstcDecoderException("Invalid block mode.");
            }

            if (texelParams.VoidExtentLdr)
            {
                FillVoidExtentLdr(bitStream, outputBuffer, blockWidth, blockHeight);

                return true;
            }

            if (texelParams.VoidExtentHdr)
            {
                throw new AstcDecoderException("HDR void extent blocks are not supported.");
            }

            if (texelParams.Width > blockWidth)
            {
                throw new AstcDecoderException("Texel weight grid width should be smaller than block width.");
            }

            if (texelParams.Height > blockHeight)
            {
                throw new AstcDecoderException("Texel weight grid height should be smaller than block height.");
            }

            // Read num partitions
            int numberPartitions = bitStream.ReadBits(2) + 1;
            Debug.Assert(numberPartitions <= 4);

            if (numberPartitions == 4 && texelParams.DualPlane)
            {
                throw new AstcDecoderException("Dual plane mode is incompatible with four partition blocks.");
            }

            // Based on the number of partitions, read the color endpoint mode for
            // each partition.

            // Determine partitions, partition index, and color endpoint modes
            int    planeIndices      = -1;
            int    partitionIndex;
            uint[] colorEndpointMode = { 0, 0, 0, 0 };

            BitArrayStream colorEndpointStream = new BitArrayStream(new BitArray(16 * 8));

            // Read extra config data...
            uint baseColorEndpointMode = 0;

            if (numberPartitions == 1)
            {
                colorEndpointMode[0] = (uint)bitStream.ReadBits(4);
                partitionIndex       = 0;
            }
            else
            {
                partitionIndex        = bitStream.ReadBits(10);
                baseColorEndpointMode = (uint)bitStream.ReadBits(6);
            }

            uint baseMode = (baseColorEndpointMode & 3);

            // Remaining bits are color endpoint data...
            int numberWeightBits = texelParams.GetPackedBitSize();
            int remainingBits    = 128 - numberWeightBits - bitStream.Position;

            // Consider extra bits prior to texel data...
            uint extraColorEndpointModeBits = 0;

            if (baseMode != 0)
            {
                switch (numberPartitions)
                {
                    case 2:  extraColorEndpointModeBits += 2; break;
                    case 3:  extraColorEndpointModeBits += 5; break;
                    case 4:  extraColorEndpointModeBits += 8; break;
                    default: Debug.Assert(false); break;
                }
            }

            remainingBits -= (int)extraColorEndpointModeBits;

            // Do we have a dual plane situation?
            int planeSelectorBits = 0;

            if (texelParams.DualPlane)
            {
                planeSelectorBits = 2;
            }

            remainingBits -= planeSelectorBits;

            // Read color data...
            int colorDataBits = remainingBits;

            while (remainingBits > 0)
            {
                int numberBits = Math.Min(remainingBits, 8);
                int bits = bitStream.ReadBits(numberBits);
                colorEndpointStream.WriteBits(bits, numberBits);
                remainingBits -= 8;
            }

            // Read the plane selection bits
            planeIndices = bitStream.ReadBits(planeSelectorBits);

            // Read the rest of the CEM
            if (baseMode != 0)
            {
                uint extraColorEndpointMode = (uint)bitStream.ReadBits((int)extraColorEndpointModeBits);
                uint tempColorEndpointMode  = (extraColorEndpointMode << 6) | baseColorEndpointMode;
                tempColorEndpointMode     >>= 2;

                bool[] c = new bool[4];

                for (int i = 0; i < numberPartitions; i++)
                {
                    c[i] = (tempColorEndpointMode & 1) != 0;
                    tempColorEndpointMode >>= 1;
                }

                byte[] m = new byte[4];

                for (int i = 0; i < numberPartitions; i++)
                {
                    m[i] = (byte)(tempColorEndpointMode & 3);
                    tempColorEndpointMode >>= 2;
                    Debug.Assert(m[i] <= 3);
                }

                for (int i = 0; i < numberPartitions; i++)
                {
                    colorEndpointMode[i] = baseMode;
                    if (!(c[i])) colorEndpointMode[i] -= 1;
                    colorEndpointMode[i] <<= 2;
                    colorEndpointMode[i] |= m[i];
                }
            }
            else if (numberPartitions > 1)
            {
                uint tempColorEndpointMode = baseColorEndpointMode >> 2;

                for (uint i = 0; i < numberPartitions; i++)
                {
                    colorEndpointMode[i] = tempColorEndpointMode;
                }
            }

            // Make sure everything up till here is sane.
            for (int i = 0; i < numberPartitions; i++)
            {
                Debug.Assert(colorEndpointMode[i] < 16);
            }
            Debug.Assert(bitStream.Position + texelParams.GetPackedBitSize() == 128);

            // Decode both color data and texel weight data
            int[] colorValues = new int[32]; // Four values * two endpoints * four maximum partitions
            DecodeColorValues(colorValues, colorEndpointStream.ToByteArray(), colorEndpointMode, numberPartitions, colorDataBits);

            AstcPixel[][] endPoints = new AstcPixel[4][];
            endPoints[0] = new AstcPixel[2];
            endPoints[1] = new AstcPixel[2];
            endPoints[2] = new AstcPixel[2];
            endPoints[3] = new AstcPixel[2];

            int colorValuesPosition = 0;

            for (int i = 0; i < numberPartitions; i++)
            {
                ComputeEndpoints(endPoints[i], colorValues, colorEndpointMode[i], ref colorValuesPosition);
            }

            // Read the texel weight data.
            byte[] texelWeightData = (byte[])inputBuffer.Clone();

            // Reverse everything
            for (int i = 0; i < 8; i++)
            {
                byte a = ReverseByte(texelWeightData[i]);
                byte b = ReverseByte(texelWeightData[15 - i]);

                texelWeightData[i]      = b;
                texelWeightData[15 - i] = a;
            }

            // Make sure that higher non-texel bits are set to zero
            int clearByteStart                   = (texelParams.GetPackedBitSize() >> 3) + 1;
            texelWeightData[clearByteStart - 1] &= (byte)((1 << (texelParams.GetPackedBitSize() % 8)) - 1);

            int cLen = 16 - clearByteStart;
            for (int i = clearByteStart; i < clearByteStart + cLen; i++) texelWeightData[i] = 0;

            List<IntegerEncoded> texelWeightValues = new List<IntegerEncoded>();
            BitArrayStream weightBitStream         = new BitArrayStream(new BitArray(texelWeightData));

            IntegerEncoded.DecodeIntegerSequence(texelWeightValues, weightBitStream, texelParams.MaxWeight, texelParams.GetNumWeightValues());

            // Blocks can be at most 12x12, so we can have as many as 144 weights
            int[][] weights = new int[2][];
            weights[0] = new int[144];
            weights[1] = new int[144];

            UnquantizeTexelWeights(weights, texelWeightValues, texelParams, blockWidth, blockHeight);

            // Now that we have endpoints and weights, we can interpolate and generate
            // the proper decoding...
            for (int j = 0; j < blockHeight; j++)
            {
                for (int i = 0; i < blockWidth; i++)
                {
                    int partition = Select2dPartition(partitionIndex, i, j, numberPartitions, ((blockHeight * blockWidth) < 32));
                    Debug.Assert(partition < numberPartitions);

                    AstcPixel pixel = new AstcPixel(0, 0, 0, 0);
                    for (int component = 0; component < 4; component++)
                    {
                        int component0 = endPoints[partition][0].GetComponent(component);
                        component0     = BitArrayStream.Replicate(component0, 8, 16);
                        int component1 = endPoints[partition][1].GetComponent(component);
                        component1     = BitArrayStream.Replicate(component1, 8, 16);

                        int plane = 0;

                        if (texelParams.DualPlane && (((planeIndices + 1) & 3) == component))
                        {
                            plane = 1;
                        }

                        int weight = weights[plane][j * blockWidth + i];
                        int finalComponent = (component0 * (64 - weight) + component1 * weight + 32) / 64;

                        if (finalComponent == 65535)
                        {
                            pixel.SetComponent(component, 255);
                        }
                        else
                        {
                            double finalComponentFloat = finalComponent;
                            pixel.SetComponent(component, (int)(255.0 * (finalComponentFloat / 65536.0) + 0.5));
                        }
                    }

                    outputBuffer[j * blockWidth + i] = pixel.Pack();
                }
            }

            return true;
        }

        private static int Select2dPartition(int seed, int x, int y, int partitionCount, bool isSmallBlock)
        {
            return SelectPartition(seed, x, y, 0, partitionCount, isSmallBlock);
        }

        private static int SelectPartition(int seed, int x, int y, int z, int partitionCount, bool isSmallBlock)
        {
            if (partitionCount == 1)
            {
                return 0;
            }

            if (isSmallBlock)
            {
                x <<= 1;
                y <<= 1;
                z <<= 1;
            }

            seed += (partitionCount - 1) * 1024;

            int  rightNum = Hash52((uint)seed);
            byte seed01   = (byte)(rightNum & 0xF);
            byte seed02   = (byte)((rightNum >> 4) & 0xF);
            byte seed03   = (byte)((rightNum >> 8) & 0xF);
            byte seed04   = (byte)((rightNum >> 12) & 0xF);
            byte seed05   = (byte)((rightNum >> 16) & 0xF);
            byte seed06   = (byte)((rightNum >> 20) & 0xF);
            byte seed07   = (byte)((rightNum >> 24) & 0xF);
            byte seed08   = (byte)((rightNum >> 28) & 0xF);
            byte seed09   = (byte)((rightNum >> 18) & 0xF);
            byte seed10   = (byte)((rightNum >> 22) & 0xF);
            byte seed11   = (byte)((rightNum >> 26) & 0xF);
            byte seed12   = (byte)(((rightNum >> 30) | (rightNum << 2)) & 0xF);

            seed01 *= seed01; seed02 *= seed02;
            seed03 *= seed03; seed04 *= seed04;
            seed05 *= seed05; seed06 *= seed06;
            seed07 *= seed07; seed08 *= seed08;
            seed09 *= seed09; seed10 *= seed10;
            seed11 *= seed11; seed12 *= seed12;

            int seedHash1, seedHash2, seedHash3;

            if ((seed & 1) != 0)
            {
                seedHash1 = (seed & 2) != 0 ? 4 : 5;
                seedHash2 = (partitionCount == 3) ? 6 : 5;
            }
            else
            {
                seedHash1 = (partitionCount == 3) ? 6 : 5;
                seedHash2 = (seed & 2) != 0 ? 4 : 5;
            }

            seedHash3 = (seed & 0x10) != 0 ? seedHash1 : seedHash2;

            seed01 >>= seedHash1; seed02 >>= seedHash2; seed03 >>= seedHash1; seed04 >>= seedHash2;
            seed05 >>= seedHash1; seed06 >>= seedHash2; seed07 >>= seedHash1; seed08 >>= seedHash2;
            seed09 >>= seedHash3; seed10 >>= seedHash3; seed11 >>= seedHash3; seed12 >>= seedHash3;

            int a = seed01 * x + seed02 * y + seed11 * z + (rightNum >> 14);
            int b = seed03 * x + seed04 * y + seed12 * z + (rightNum >> 10);
            int c = seed05 * x + seed06 * y + seed09 * z + (rightNum >> 6);
            int d = seed07 * x + seed08 * y + seed10 * z + (rightNum >> 2);

            a &= 0x3F; b &= 0x3F; c &= 0x3F; d &= 0x3F;

            if (partitionCount < 4) d = 0;
            if (partitionCount < 3) c = 0;

            if (a >= b && a >= c && a >= d) return 0;
            else if (b >= c && b >= d) return 1;
            else if (c >= d) return 2;
            return 3;
        }

        static int Hash52(uint val)
        {
            val ^= val >> 15; val -= val << 17; val += val << 7; val += val << 4;
            val ^= val >> 5;  val += val << 16; val ^= val >> 7; val ^= val >> 3;
            val ^= val << 6;  val ^= val >> 17;

            return (int)val;
        }

        static void UnquantizeTexelWeights(
            int[][]              outputBuffer,
            List<IntegerEncoded> weights,
            TexelWeightParams    texelParams,
            int                  blockWidth,
            int                  blockHeight)
        {
            int weightIndices   = 0;
            int[][] unquantized = new int[2][];
            unquantized[0]      = new int[144];
            unquantized[1]      = new int[144];

            for (int i = 0; i < weights.Count; i++)
            {
                unquantized[0][weightIndices] = UnquantizeTexelWeight(weights[i]);

                if (texelParams.DualPlane)
                {
                    i++;
                    unquantized[1][weightIndices] = UnquantizeTexelWeight(weights[i]);

                    if (i == weights.Count)
                    {
                        break;
                    }
                }

                if (++weightIndices >= (texelParams.Width * texelParams.Height)) break;
            }

            // Do infill if necessary (Section C.2.18) ...
            int ds = (1024 + (blockWidth / 2)) / (blockWidth - 1);
            int dt = (1024 + (blockHeight / 2)) / (blockHeight - 1);

            int planeScale = texelParams.DualPlane ? 2 : 1;

            for (int plane = 0; plane < planeScale; plane++)
            {
                for (int t = 0; t < blockHeight; t++)
                {
                    for (int s = 0; s < blockWidth; s++)
                    {
                        int cs = ds * s;
                        int ct = dt * t;

                        int gs = (cs * (texelParams.Width - 1) + 32) >> 6;
                        int gt = (ct * (texelParams.Height - 1) + 32) >> 6;

                        int js = gs >> 4;
                        int fs = gs & 0xF;

                        int jt = gt >> 4;
                        int ft = gt & 0x0F;

                        int w11 = (fs * ft + 8) >> 4;
                        int w10 = ft - w11;
                        int w01 = fs - w11;
                        int w00 = 16 - fs - ft + w11;

                        int v0 = js + jt * texelParams.Width;

                        int p00 = 0;
                        int p01 = 0;
                        int p10 = 0;
                        int p11 = 0;

                        if (v0 < (texelParams.Width * texelParams.Height))
                        {
                            p00 = unquantized[plane][v0];
                        }

                        if (v0 + 1 < (texelParams.Width * texelParams.Height))
                        {
                            p01 = unquantized[plane][v0 + 1];
                        }

                        if (v0 + texelParams.Width < (texelParams.Width * texelParams.Height))
                        {
                            p10 = unquantized[plane][v0 + texelParams.Width];
                        }

                        if (v0 + texelParams.Width + 1 < (texelParams.Width * texelParams.Height))
                        {
                            p11 = unquantized[plane][v0 + texelParams.Width + 1];
                        }

                        outputBuffer[plane][t * blockWidth + s] = (p00 * w00 + p01 * w01 + p10 * w10 + p11 * w11 + 8) >> 4;
                    }
                }
            }
        }

        static int UnquantizeTexelWeight(IntegerEncoded intEncoded)
        {
            int bitValue  = intEncoded.BitValue;
            int bitLength = intEncoded.NumberBits;

            int a = BitArrayStream.Replicate(bitValue & 1, 1, 7);
            int b = 0, c = 0, d = 0;

            int result = 0;

            switch (intEncoded.GetEncoding())
            {
                case IntegerEncoded.EIntegerEncoding.JustBits:
                    result = BitArrayStream.Replicate(bitValue, bitLength, 6);
                    break;

                case IntegerEncoded.EIntegerEncoding.Trit:
                {
                    d = intEncoded.TritValue;
                    Debug.Assert(d < 3);

                    switch (bitLength)
                    {
                        case 0:
                        {
                            int[] results = { 0, 32, 63 };
                            result = results[d];

                            break;
                        }

                        case 1:
                        {
                            c = 50;
                            break;
                        }

                        case 2:
                        {
                            c = 23;
                            int b2 = (bitValue >> 1) & 1;
                            b = (b2 << 6) | (b2 << 2) | b2;

                            break;
                        }

                        case 3:
                        {
                            c = 11;
                            int cb = (bitValue >> 1) & 3;
                            b = (cb << 5) | cb;

                            break;
                        }

                        default:
                            throw new AstcDecoderException("Invalid trit encoding for texel weight.");
                    }

                    break;
                }

                case IntegerEncoded.EIntegerEncoding.Quint:
                {
                    d = intEncoded.QuintValue;
                    Debug.Assert(d < 5);

                    switch (bitLength)
                    {
                        case 0:
                        {
                            int[] results = { 0, 16, 32, 47, 63 };
                            result = results[d];

                            break;
                        }

                        case 1:
                        {
                            c = 28;

                            break;
                        }

                        case 2:
                        {
                            c = 13;
                            int b2 = (bitValue >> 1) & 1;
                            b = (b2 << 6) | (b2 << 1);

                            break;
                        }

                        default:
                            throw new AstcDecoderException("Invalid quint encoding for texel weight.");
                    }

                    break;
                }
            }

            if (intEncoded.GetEncoding() != IntegerEncoded.EIntegerEncoding.JustBits && bitLength > 0)
            {
                // Decode the value...
                result  = d * c + b;
                result ^= a;
                result  = (a & 0x20) | (result >> 2);
            }

            Debug.Assert(result < 64);

            // Change from [0,63] to [0,64]
            if (result > 32)
            {
                result += 1;
            }

            return result;
        }

        static byte ReverseByte(byte b)
        {
            // Taken from http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith64Bits
            return (byte)((((b) * 0x80200802L) & 0x0884422110L) * 0x0101010101L >> 32);
        }

        static uint[] ReadUintColorValues(int number, int[] colorValues, ref int colorValuesPosition)
        {
            uint[] ret = new uint[number];

            for (int i = 0; i < number; i++)
            {
                ret[i] = (uint)colorValues[colorValuesPosition++];
            }

            return ret;
        }

        static int[] ReadIntColorValues(int number, int[] colorValues, ref int colorValuesPosition)
        {
            int[] ret = new int[number];

            for (int i = 0; i < number; i++)
            {
                ret[i] = colorValues[colorValuesPosition++];
            }

            return ret;
        }

        static void ComputeEndpoints(
            AstcPixel[] endPoints,
            int[]       colorValues,
            uint        colorEndpointMode,
            ref int     colorValuesPosition)
        {
            switch (colorEndpointMode)
            {
                case 0:
                {
                    uint[] val = ReadUintColorValues(2, colorValues, ref colorValuesPosition);

                    endPoints[0] = new AstcPixel(0xFF, (short)val[0], (short)val[0], (short)val[0]);
                    endPoints[1] = new AstcPixel(0xFF, (short)val[1], (short)val[1], (short)val[1]);

                    break;
                }


                case 1:
                {
                    uint[] val = ReadUintColorValues(2, colorValues, ref colorValuesPosition);
                    int l0     = (int)((val[0] >> 2) | (val[1] & 0xC0));
                    int l1     = (int)Math.Max(l0 + (val[1] & 0x3F), 0xFFU);

                    endPoints[0] = new AstcPixel(0xFF, (short)l0, (short)l0, (short)l0);
                    endPoints[1] = new AstcPixel(0xFF, (short)l1, (short)l1, (short)l1);

                    break;
                }

                case 4:
                {
                    uint[] val = ReadUintColorValues(4, colorValues, ref colorValuesPosition);

                    endPoints[0] = new AstcPixel((short)val[2], (short)val[0], (short)val[0], (short)val[0]);
                    endPoints[1] = new AstcPixel((short)val[3], (short)val[1], (short)val[1], (short)val[1]);

                    break;
                }

                case 5:
                {
                    int[] val = ReadIntColorValues(4, colorValues, ref colorValuesPosition);

                    BitArrayStream.BitTransferSigned(ref val[1], ref val[0]);
                    BitArrayStream.BitTransferSigned(ref val[3], ref val[2]);

                    endPoints[0] = new AstcPixel((short)val[2], (short)val[0], (short)val[0], (short)val[0]);
                    endPoints[1] = new AstcPixel((short)(val[2] + val[3]), (short)(val[0] + val[1]), (short)(val[0] + val[1]), (short)(val[0] + val[1]));

                    endPoints[0].ClampByte();
                    endPoints[1].ClampByte();

                    break;
                }

                case 6:
                {
                    uint[] val = ReadUintColorValues(4, colorValues, ref colorValuesPosition);

                    endPoints[0] = new AstcPixel(0xFF, (short)(val[0] * val[3] >> 8), (short)(val[1] * val[3] >> 8), (short)(val[2] * val[3] >> 8));
                    endPoints[1] = new AstcPixel(0xFF, (short)val[0], (short)val[1], (short)val[2]);

                    break;
                }

                case 8:
                {
                    uint[] val = ReadUintColorValues(6, colorValues, ref colorValuesPosition);

                    if (val[1] + val[3] + val[5] >= val[0] + val[2] + val[4])
                    {
                        endPoints[0] = new AstcPixel(0xFF, (short)val[0], (short)val[2], (short)val[4]);
                        endPoints[1] = new AstcPixel(0xFF, (short)val[1], (short)val[3], (short)val[5]);
                    }
                    else
                    {
                        endPoints[0] = AstcPixel.BlueContract(0xFF, (short)val[1], (short)val[3], (short)val[5]);
                        endPoints[1] = AstcPixel.BlueContract(0xFF, (short)val[0], (short)val[2], (short)val[4]);
                    }

                    break;
                }

                case 9:
                {
                    int[] val = ReadIntColorValues(6, colorValues, ref colorValuesPosition);

                    BitArrayStream.BitTransferSigned(ref val[1], ref val[0]);
                    BitArrayStream.BitTransferSigned(ref val[3], ref val[2]);
                    BitArrayStream.BitTransferSigned(ref val[5], ref val[4]);

                    if (val[1] + val[3] + val[5] >= 0)
                    {
                        endPoints[0] = new AstcPixel(0xFF, (short)val[0], (short)val[2], (short)val[4]);
                        endPoints[1] = new AstcPixel(0xFF, (short)(val[0] + val[1]), (short)(val[2] + val[3]), (short)(val[4] + val[5]));
                    }
                    else
                    {
                        endPoints[0] = AstcPixel.BlueContract(0xFF, val[0] + val[1], val[2] + val[3], val[4] + val[5]);
                        endPoints[1] = AstcPixel.BlueContract(0xFF, val[0], val[2], val[4]);
                    }

                    endPoints[0].ClampByte();
                    endPoints[1].ClampByte();

                    break;
                }

                case 10:
                {
                    uint[] val = ReadUintColorValues(6, colorValues, ref colorValuesPosition);

                    endPoints[0] = new AstcPixel((short)val[4], (short)(val[0] * val[3] >> 8), (short)(val[1] * val[3] >> 8), (short)(val[2] * val[3] >> 8));
                    endPoints[1] = new AstcPixel((short)val[5], (short)val[0], (short)val[1], (short)val[2]);

                    break;
                }

                case 12:
                {
                    uint[] val = ReadUintColorValues(8, colorValues, ref colorValuesPosition);

                    if (val[1] + val[3] + val[5] >= val[0] + val[2] + val[4])
                    {
                        endPoints[0] = new AstcPixel((short)val[6], (short)val[0], (short)val[2], (short)val[4]);
                        endPoints[1] = new AstcPixel((short)val[7], (short)val[1], (short)val[3], (short)val[5]);
                    }
                    else
                    {
                        endPoints[0] = AstcPixel.BlueContract((short)val[7], (short)val[1], (short)val[3], (short)val[5]);
                        endPoints[1] = AstcPixel.BlueContract((short)val[6], (short)val[0], (short)val[2], (short)val[4]);
                    }

                    break;
                }

                case 13:
                {
                    int[] val = ReadIntColorValues(8, colorValues, ref colorValuesPosition);

                    BitArrayStream.BitTransferSigned(ref val[1], ref val[0]);
                    BitArrayStream.BitTransferSigned(ref val[3], ref val[2]);
                    BitArrayStream.BitTransferSigned(ref val[5], ref val[4]);
                    BitArrayStream.BitTransferSigned(ref val[7], ref val[6]);

                    if (val[1] + val[3] + val[5] >= 0)
                    {
                        endPoints[0] = new AstcPixel((short)val[6], (short)val[0], (short)val[2], (short)val[4]);
                        endPoints[1] = new AstcPixel((short)(val[7] + val[6]), (short)(val[0] + val[1]), (short)(val[2] + val[3]), (short)(val[4] + val[5]));
                    }
                    else
                    {
                        endPoints[0] = AstcPixel.BlueContract(val[6] + val[7], val[0] + val[1], val[2] + val[3], val[4] + val[5]);
                        endPoints[1] = AstcPixel.BlueContract(val[6], val[0], val[2], val[4]);
                    }

                    endPoints[0].ClampByte();
                    endPoints[1].ClampByte();

                    break;
                }

                default:
                    throw new AstcDecoderException("Unsupported color endpoint mode (is it HDR?)");
            }
        }

        static void DecodeColorValues(
            int[]  outputValues,
            byte[] inputData,
            uint[] modes,
            int    numberPartitions,
            int    numberBitsForColorData)
        {
            // First figure out how many color values we have
            int numberValues = 0;

            for (int i = 0; i < numberPartitions; i++)
            {
                numberValues += (int)((modes[i] >> 2) + 1) << 1;
            }

            // Then based on the number of values and the remaining number of bits,
            // figure out the max value for each of them...
            int range = 256;

            while (--range > 0)
            {
                IntegerEncoded intEncoded = IntegerEncoded.CreateEncoding(range);
                int bitLength             = intEncoded.GetBitLength(numberValues);

                if (bitLength <= numberBitsForColorData)
                {
                    // Find the smallest possible range that matches the given encoding
                    while (--range > 0)
                    {
                        IntegerEncoded newIntEncoded = IntegerEncoded.CreateEncoding(range);
                        if (!newIntEncoded.MatchesEncoding(intEncoded))
                        {
                            break;
                        }
                    }

                    // Return to last matching range.
                    range++;
                    break;
                }
            }

            // We now have enough to decode our integer sequence.
            List<IntegerEncoded> integerEncodedSequence = new List<IntegerEncoded>();
            BitArrayStream colorBitStream               = new BitArrayStream(new BitArray(inputData));

            IntegerEncoded.DecodeIntegerSequence(integerEncodedSequence, colorBitStream, range, numberValues);

            // Once we have the decoded values, we need to dequantize them to the 0-255 range
            // This procedure is outlined in ASTC spec C.2.13
            int outputIndices = 0;

            foreach (IntegerEncoded intEncoded in integerEncodedSequence)
            {
                int bitLength = intEncoded.NumberBits;
                int bitValue  = intEncoded.BitValue;

                Debug.Assert(bitLength >= 1);

                int a = 0, b = 0, c = 0, d = 0;
                // A is just the lsb replicated 9 times.
                a = BitArrayStream.Replicate(bitValue & 1, 1, 9);

                switch (intEncoded.GetEncoding())
                {
                    case IntegerEncoded.EIntegerEncoding.JustBits:
                    {
                        outputValues[outputIndices++] = BitArrayStream.Replicate(bitValue, bitLength, 8);

                        break;
                    }

                    case IntegerEncoded.EIntegerEncoding.Trit:
                    {
                        d = intEncoded.TritValue;

                        switch (bitLength)
                        {
                            case 1:
                            {
                                c = 204;

                                break;
                            }

                            case 2:
                            {
                                c = 93;
                                // B = b000b0bb0
                                int b2 = (bitValue >> 1) & 1;
                                b = (b2 << 8) | (b2 << 4) | (b2 << 2) | (b2 << 1);

                                break;
                            }

                            case 3:
                            {
                                c = 44;
                                // B = cb000cbcb
                                int cb = (bitValue >> 1) & 3;
                                b = (cb << 7) | (cb << 2) | cb;

                                break;
                            }


                            case 4:
                            {
                                c = 22;
                                // B = dcb000dcb
                                int dcb = (bitValue >> 1) & 7;
                                b = (dcb << 6) | dcb;

                                break;
                            }

                            case 5:
                            {
                                c = 11;
                                // B = edcb000ed
                                int edcb = (bitValue >> 1) & 0xF;
                                b = (edcb << 5) | (edcb >> 2);

                                break;
                            }

                            case 6:
                            {
                                c = 5;
                                // B = fedcb000f
                                int fedcb = (bitValue >> 1) & 0x1F;
                                b = (fedcb << 4) | (fedcb >> 4);

                                break;
                            }

                            default:
                                throw new AstcDecoderException("Unsupported trit encoding for color values.");
                        }

                        break;
                    }

                    case IntegerEncoded.EIntegerEncoding.Quint:
                    {
                        d = intEncoded.QuintValue;

                        switch (bitLength)
                        {
                            case 1:
                            {
                                c = 113;

                                break;
                            }

                            case 2:
                            {
                                c = 54;
                                // B = b0000bb00
                                int b2 = (bitValue >> 1) & 1;
                                b = (b2 << 8) | (b2 << 3) | (b2 << 2);

                                break;
                            }

                            case 3:
                            {
                                c = 26;
                                // B = cb0000cbc
                                int cb = (bitValue >> 1) & 3;
                                b = (cb << 7) | (cb << 1) | (cb >> 1);

                                break;
                            }

                            case 4:
                            {
                                c = 13;
                                // B = dcb0000dc
                                int dcb = (bitValue >> 1) & 7;
                                b = (dcb << 6) | (dcb >> 1);

                                break;
                            }

                            case 5:
                            {
                                c = 6;
                                // B = edcb0000e
                                int edcb = (bitValue >> 1) & 0xF;
                                b = (edcb << 5) | (edcb >> 3);

                                break;
                            }

                            default:
                                throw new AstcDecoderException("Unsupported quint encoding for color values.");
                        }
                        break;
                    }
                }

                if (intEncoded.GetEncoding() != IntegerEncoded.EIntegerEncoding.JustBits)
                {
                    int T = d * c + b;
                    T    ^= a;
                    T     = (a & 0x80) | (T >> 2);

                    outputValues[outputIndices++] = T;
                }
            }

            // Make sure that each of our values is in the proper range...
            for (int i = 0; i < numberValues; i++)
            {
                Debug.Assert(outputValues[i] <= 255);
            }
        }

        static void FillVoidExtentLdr(BitArrayStream bitStream, int[] outputBuffer, int blockWidth, int blockHeight)
        {
            // Don't actually care about the void extent, just read the bits...
            for (int i = 0; i < 4; ++i)
            {
                bitStream.ReadBits(13);
            }

            // Decode the RGBA components and renormalize them to the range [0, 255]
            ushort r = (ushort)bitStream.ReadBits(16);
            ushort g = (ushort)bitStream.ReadBits(16);
            ushort b = (ushort)bitStream.ReadBits(16);
            ushort a = (ushort)bitStream.ReadBits(16);

            int rgba = (r >> 8) | (g & 0xFF00) | ((b) & 0xFF00) << 8 | ((a) & 0xFF00) << 16;

            for (int j = 0; j < blockHeight; j++)
            {
                for (int i = 0; i < blockWidth; i++)
                {
                    outputBuffer[j * blockWidth + i] = rgba;
                }
            }
        }

        static TexelWeightParams DecodeBlockInfo(BitArrayStream bitStream)
        {
            TexelWeightParams texelParams = new TexelWeightParams();

            // Read the entire block mode all at once
            ushort modeBits = (ushort)bitStream.ReadBits(11);

            // Does this match the void extent block mode?
            if ((modeBits & 0x01FF) == 0x1FC)
            {
                if ((modeBits & 0x200) != 0)
                {
                    texelParams.VoidExtentHdr = true;
                }
                else
                {
                    texelParams.VoidExtentLdr = true;
                }

                // Next two bits must be one.
                if ((modeBits & 0x400) == 0 || bitStream.ReadBits(1) == 0)
                {
                    texelParams.Error = true;
                }

                return texelParams;
            }

            // First check if the last four bits are zero
            if ((modeBits & 0xF) == 0)
            {
                texelParams.Error = true;
                return texelParams;
            }

            // If the last two bits are zero, then if bits
            // [6-8] are all ones, this is also reserved.
            if ((modeBits & 0x3) == 0 && (modeBits & 0x1C0) == 0x1C0)
            {
                texelParams.Error = true;

                return texelParams;
            }

            // Otherwise, there is no error... Figure out the layout
            // of the block mode. Layout is determined by a number
            // between 0 and 9 corresponding to table C.2.8 of the
            // ASTC spec.
            int layout = 0;

            if ((modeBits & 0x1) != 0 || (modeBits & 0x2) != 0)
            {
                // layout is in [0-4]
                if ((modeBits & 0x8) != 0)
                {
                    // layout is in [2-4]
                    if ((modeBits & 0x4) != 0)
                    {
                        // layout is in [3-4]
                        if ((modeBits & 0x100) != 0)
                        {
                            layout = 4;
                        }
                        else
                        {
                            layout = 3;
                        }
                    }
                    else
                    {
                        layout = 2;
                    }
                }
                else
                {
                    // layout is in [0-1]
                    if ((modeBits & 0x4) != 0)
                    {
                        layout = 1;
                    }
                    else
                    {
                        layout = 0;
                    }
                }
            }
            else
            {
                // layout is in [5-9]
                if ((modeBits & 0x100) != 0)
                {
                    // layout is in [7-9]
                    if ((modeBits & 0x80) != 0)
                    {
                        // layout is in [7-8]
                        Debug.Assert((modeBits & 0x40) == 0);

                        if ((modeBits & 0x20) != 0)
                        {
                            layout = 8;
                        }
                        else
                        {
                            layout = 7;
                        }
                    }
                    else
                    {
                        layout = 9;
                    }
                }
                else
                {
                    // layout is in [5-6]
                    if ((modeBits & 0x80) != 0)
                    {
                        layout = 6;
                    }
                    else
                    {
                        layout = 5;
                    }
                }
            }

            Debug.Assert(layout < 10);

            // Determine R
            int r = (modeBits >> 4) & 1;
            if (layout < 5)
            {
                r |= (modeBits & 0x3) << 1;
            }
            else
            {
                r |= (modeBits & 0xC) >> 1;
            }

            Debug.Assert(2 <= r && r <= 7);

            // Determine width & height
            switch (layout)
            {
                case 0:
                {
                    int a = (modeBits >> 5) & 0x3;
                    int b = (modeBits >> 7) & 0x3;

                    texelParams.Width  = b + 4;
                    texelParams.Height = a + 2;

                    break;
                }

                case 1:
                {
                    int a = (modeBits >> 5) & 0x3;
                    int b = (modeBits >> 7) & 0x3;

                    texelParams.Width  = b + 8;
                    texelParams.Height = a + 2;

                    break;
                }

                case 2:
                {
                    int a = (modeBits >> 5) & 0x3;
                    int b = (modeBits >> 7) & 0x3;

                    texelParams.Width  = a + 2;
                    texelParams.Height = b + 8;

                    break;
                }

                case 3:
                {
                    int a = (modeBits >> 5) & 0x3;
                    int b = (modeBits >> 7) & 0x1;

                    texelParams.Width  = a + 2;
                    texelParams.Height = b + 6;

                    break;
                }

                case 4:
                {
                    int a = (modeBits >> 5) & 0x3;
                    int b = (modeBits >> 7) & 0x1;

                    texelParams.Width  = b + 2;
                    texelParams.Height = a + 2;

                    break;
                }

                case 5:
                {
                    int a = (modeBits >> 5) & 0x3;

                    texelParams.Width  = 12;
                    texelParams.Height = a + 2;

                    break;
                }

                case 6:
                {
                    int a = (modeBits >> 5) & 0x3;

                    texelParams.Width  = a + 2;
                    texelParams.Height = 12;

                    break;
                }

                case 7:
                {
                    texelParams.Width  = 6;
                    texelParams.Height = 10;

                    break;
                }

                case 8:
                {
                    texelParams.Width  = 10;
                    texelParams.Height = 6;
                    break;
                }

                case 9:
                {
                    int a = (modeBits >> 5) & 0x3;
                    int b = (modeBits >> 9) & 0x3;

                    texelParams.Width  = a + 6;
                    texelParams.Height = b + 6;

                    break;
                }

                default:
                    // Don't know this layout...
                    texelParams.Error = true;
                    break;
            }

            // Determine whether or not we're using dual planes
            // and/or high precision layouts.
            bool d = ((layout != 9) && ((modeBits & 0x400) != 0));
            bool h = (layout != 9) && ((modeBits & 0x200) != 0);

            if (h)
            {
                int[] maxWeights = { 9, 11, 15, 19, 23, 31 };
                texelParams.MaxWeight = maxWeights[r - 2];
            }
            else
            {
                int[] maxWeights = { 1, 2, 3, 4, 5, 7 };
                texelParams.MaxWeight = maxWeights[r - 2];
            }

            texelParams.DualPlane = d;

            return texelParams;
        }
    }
}