// LzmaDecoder.cs

using System;

namespace SevenZip.Compression.LZMA
{
    using RangeCoder;
    using System.Threading;

    public class Decoder : ICoder, ISetDecoderProperties // ,System.IO.Stream
    {
        private class LenDecoder
        {
            private BitDecoder m_Choice = new();
            private BitDecoder m_Choice2 = new();
            private readonly BitTreeDecoder[] m_LowCoder = new BitTreeDecoder[Base.kNumPosStatesMax];
            private readonly BitTreeDecoder[] m_MidCoder = new BitTreeDecoder[Base.kNumPosStatesMax];
            private readonly BitTreeDecoder m_HighCoder = new(Base.kNumHighLenBits);
            private uint m_NumPosStates = 0;

            public void Create(uint numPosStates)
            {
                for (uint posState = m_NumPosStates; posState < numPosStates; posState++)
                {
                    m_LowCoder[posState] = new BitTreeDecoder(Base.kNumLowLenBits);
                    m_MidCoder[posState] = new BitTreeDecoder(Base.kNumMidLenBits);
                }
                m_NumPosStates = numPosStates;
            }

            public void Init()
            {
                m_Choice.Init();
                for (uint posState = 0; posState < m_NumPosStates; posState++)
                {
                    m_LowCoder[posState].Init();
                    m_MidCoder[posState].Init();
                }
                m_Choice2.Init();
                m_HighCoder.Init();
            }

            public uint Decode(RangeCoder.Decoder rangeDecoder, uint posState)
            {
                if (m_Choice.Decode(rangeDecoder) == 0)
                {
                    return m_LowCoder[posState].Decode(rangeDecoder);
                }
                else
                {
                    uint symbol = Base.kNumLowLenSymbols;
                    if (m_Choice2.Decode(rangeDecoder) == 0)
                    {
                        symbol += m_MidCoder[posState].Decode(rangeDecoder);
                    }
                    else
                    {
                        symbol += Base.kNumMidLenSymbols;
                        symbol += m_HighCoder.Decode(rangeDecoder);
                    }
                    return symbol;
                }
            }
        }

        private class LiteralDecoder
        {
            private struct Decoder2
            {
                private BitDecoder[] m_Decoders;
                public void Create() { m_Decoders = new BitDecoder[0x300]; }
                public void Init() { for (int i = 0; i < 0x300; i++)
                    {
                        m_Decoders[i].Init();
                    }
                }

                public byte DecodeNormal(RangeCoder.Decoder rangeDecoder)
                {
                    uint symbol = 1;
                    do
                    {
                        symbol = (symbol << 1) | m_Decoders[symbol].Decode(rangeDecoder);
                    }
                    while (symbol < 0x100);
                    return (byte)symbol;
                }

                public byte DecodeWithMatchByte(RangeCoder.Decoder rangeDecoder, byte matchByte)
                {
                    uint symbol = 1;
                    do
                    {
                        uint matchBit = (uint)(matchByte >> 7) & 1;
                        matchByte <<= 1;
                        uint bit = m_Decoders[((1 + matchBit) << 8) + symbol].Decode(rangeDecoder);
                        symbol = (symbol << 1) | bit;
                        if (matchBit != bit)
                        {
                            while (symbol < 0x100)
                            {
                                symbol = (symbol << 1) | m_Decoders[symbol].Decode(rangeDecoder);
                            }

                            break;
                        }
                    }
                    while (symbol < 0x100);
                    return (byte)symbol;
                }
            }

            private Decoder2[] m_Coders;
            private int m_NumPrevBits;
            private int m_NumPosBits;
            private uint m_PosMask;

            public void Create(int numPosBits, int numPrevBits)
            {
                if (m_Coders != null && m_NumPrevBits == numPrevBits &&
                    m_NumPosBits == numPosBits)
                {
                    return;
                }

                m_NumPosBits = numPosBits;
                m_PosMask = ((uint)1 << numPosBits) - 1;
                m_NumPrevBits = numPrevBits;
                uint numStates = (uint)1 << (m_NumPrevBits + m_NumPosBits);
                m_Coders = new Decoder2[numStates];
                for (uint i = 0; i < numStates; i++)
                {
                    m_Coders[i].Create();
                }
            }

            public void Init()
            {
                uint numStates = (uint)1 << (m_NumPrevBits + m_NumPosBits);
                for (uint i = 0; i < numStates; i++)
                {
                    m_Coders[i].Init();
                }
            }

            private uint GetState(uint pos, byte prevByte)
            { return ((pos & m_PosMask) << m_NumPrevBits) + (uint)(prevByte >> (8 - m_NumPrevBits)); }

            public byte DecodeNormal(RangeCoder.Decoder rangeDecoder, uint pos, byte prevByte)
            { return m_Coders[GetState(pos, prevByte)].DecodeNormal(rangeDecoder); }

            public byte DecodeWithMatchByte(RangeCoder.Decoder rangeDecoder, uint pos, byte prevByte, byte matchByte)
            { return m_Coders[GetState(pos, prevByte)].DecodeWithMatchByte(rangeDecoder, matchByte); }
        };

        private readonly LZ.OutWindow m_OutWindow = new();
        private readonly RangeCoder.Decoder m_RangeDecoder = new();

        private readonly BitDecoder[] m_IsMatchDecoders = new BitDecoder[Base.kNumStates << Base.kNumPosStatesBitsMax];
        private readonly BitDecoder[] m_IsRepDecoders = new BitDecoder[Base.kNumStates];
        private readonly BitDecoder[] m_IsRepG0Decoders = new BitDecoder[Base.kNumStates];
        private readonly BitDecoder[] m_IsRepG1Decoders = new BitDecoder[Base.kNumStates];
        private readonly BitDecoder[] m_IsRepG2Decoders = new BitDecoder[Base.kNumStates];
        private readonly BitDecoder[] m_IsRep0LongDecoders = new BitDecoder[Base.kNumStates << Base.kNumPosStatesBitsMax];

        private readonly BitTreeDecoder[] m_PosSlotDecoder = new BitTreeDecoder[Base.kNumLenToPosStates];
        private readonly BitDecoder[] m_PosDecoders = new BitDecoder[Base.kNumFullDistances - Base.kEndPosModelIndex];

        private readonly BitTreeDecoder m_PosAlignDecoder = new(Base.kNumAlignBits);

        private readonly LenDecoder m_LenDecoder = new();
        private readonly LenDecoder m_RepLenDecoder = new();

        private readonly LiteralDecoder m_LiteralDecoder = new();

        private uint m_DictionarySize;
        private uint m_DictionarySizeCheck;

        private uint m_PosStateMask;

        public Decoder()
        {
            m_DictionarySize = 0xFFFFFFFF;
            for (int i = 0; i < Base.kNumLenToPosStates; i++)
            {
                m_PosSlotDecoder[i] = new BitTreeDecoder(Base.kNumPosSlotBits);
            }
        }

        private void SetDictionarySize(uint dictionarySize)
        {
            if (m_DictionarySize != dictionarySize)
            {
                m_DictionarySize = dictionarySize;
                m_DictionarySizeCheck = Math.Max(m_DictionarySize, 1);
                uint blockSize = Math.Max(m_DictionarySizeCheck, 1 << 12);
                m_OutWindow.Create(blockSize);
            }
        }

        private void SetLiteralProperties(int lp, int lc)
        {
            if (lp > 8)
            {
                throw new InvalidParamException();
            }

            if (lc > 8)
            {
                throw new InvalidParamException();
            }

            m_LiteralDecoder.Create(lp, lc);
        }

        private void SetPosBitsProperties(int pb)
        {
            if (pb > Base.kNumPosStatesBitsMax)
            {
                throw new InvalidParamException();
            }

            uint numPosStates = (uint)1 << pb;
            m_LenDecoder.Create(numPosStates);
            m_RepLenDecoder.Create(numPosStates);
            m_PosStateMask = numPosStates - 1;
        }

        private bool _solid = false;
        private void Init(System.IO.Stream inStream, System.IO.Stream outStream)
        {
            m_RangeDecoder.Init(inStream);
            m_OutWindow.Init(outStream, _solid);

            uint i;
            for (i = 0; i < Base.kNumStates; i++)
            {
                for (uint j = 0; j <= m_PosStateMask; j++)
                {
                    uint index = (i << Base.kNumPosStatesBitsMax) + j;
                    m_IsMatchDecoders[index].Init();
                    m_IsRep0LongDecoders[index].Init();
                }
                m_IsRepDecoders[i].Init();
                m_IsRepG0Decoders[i].Init();
                m_IsRepG1Decoders[i].Init();
                m_IsRepG2Decoders[i].Init();
            }

            m_LiteralDecoder.Init();
            for (i = 0; i < Base.kNumLenToPosStates; i++)
            {
                m_PosSlotDecoder[i].Init();
            }
            // m_PosSpecDecoder.Init();
            for (i = 0; i < Base.kNumFullDistances - Base.kEndPosModelIndex; i++)
            {
                m_PosDecoders[i].Init();
            }

            m_LenDecoder.Init();
            m_RepLenDecoder.Init();
            m_PosAlignDecoder.Init();
        }

        public void Code(System.IO.Stream inStream, System.IO.Stream outStream,
            Int64 inSize, Int64 outSize, ICodeProgress progress, CancellationToken? token = null)
        {
            Init(inStream, outStream);

            Base.State state = new();
            state.Init();
            uint rep0 = 0, rep1 = 0, rep2 = 0, rep3 = 0;

            UInt64 nowPos64 = 0;
            UInt64 outSize64 = (UInt64)outSize;
            if (nowPos64 < outSize64)
            {
                if (m_IsMatchDecoders[state.Index << Base.kNumPosStatesBitsMax].Decode(m_RangeDecoder) != 0)
                {
                    throw new DataErrorException();
                }

                state.UpdateChar();
                byte b = m_LiteralDecoder.DecodeNormal(m_RangeDecoder, 0, 0);
                m_OutWindow.PutByte(b);
                nowPos64++;
            }

            try
            {
                while (nowPos64 < outSize64)
                {
                    token?.ThrowIfCancellationRequested();

                    // UInt64 next = Math.Min(nowPos64 + (1 << 18), outSize64);
                    // while(nowPos64 < next)
                    {
                        uint posState = (uint)nowPos64 & m_PosStateMask;
                        if (m_IsMatchDecoders[(state.Index << Base.kNumPosStatesBitsMax) + posState].Decode(m_RangeDecoder) == 0)
                        {
                            byte b;
                            byte prevByte = m_OutWindow.GetByte(0);
                            b = !state.IsCharState()
                                ? m_LiteralDecoder.DecodeWithMatchByte(m_RangeDecoder,
                                   (uint)nowPos64, prevByte, m_OutWindow.GetByte(rep0))
                                : m_LiteralDecoder.DecodeNormal(m_RangeDecoder, (uint)nowPos64, prevByte);

                            m_OutWindow.PutByte(b);
                            state.UpdateChar();
                            nowPos64++;
                        }
                        else
                        {
                            uint len;
                            if (m_IsRepDecoders[state.Index].Decode(m_RangeDecoder) == 1)
                            {
                                if (m_IsRepG0Decoders[state.Index].Decode(m_RangeDecoder) == 0)
                                {
                                    if (m_IsRep0LongDecoders[(state.Index << Base.kNumPosStatesBitsMax) + posState].Decode(m_RangeDecoder) == 0)
                                    {
                                        state.UpdateShortRep();
                                        m_OutWindow.PutByte(m_OutWindow.GetByte(rep0));
                                        nowPos64++;
                                        continue;
                                    }
                                }
                                else
                                {
                                    UInt32 distance;
                                    if (m_IsRepG1Decoders[state.Index].Decode(m_RangeDecoder) == 0)
                                    {
                                        distance = rep1;
                                    }
                                    else
                                    {
                                        if (m_IsRepG2Decoders[state.Index].Decode(m_RangeDecoder) == 0)
                                        {
                                            distance = rep2;
                                        }
                                        else
                                        {
                                            distance = rep3;
                                            rep3 = rep2;
                                        }
                                        rep2 = rep1;
                                    }
                                    rep1 = rep0;
                                    rep0 = distance;
                                }
                                len = m_RepLenDecoder.Decode(m_RangeDecoder, posState) + Base.kMatchMinLen;
                                state.UpdateRep();
                            }
                            else
                            {
                                rep3 = rep2;
                                rep2 = rep1;
                                rep1 = rep0;
                                len = Base.kMatchMinLen + m_LenDecoder.Decode(m_RangeDecoder, posState);
                                state.UpdateMatch();
                                uint posSlot = m_PosSlotDecoder[Base.GetLenToPosState(len)].Decode(m_RangeDecoder);
                                if (posSlot >= Base.kStartPosModelIndex)
                                {
                                    int numDirectBits = (int)((posSlot >> 1) - 1);
                                    rep0 = ((2 | (posSlot & 1)) << numDirectBits);
                                    if (posSlot < Base.kEndPosModelIndex)
                                    {
                                        rep0 += BitTreeDecoder.ReverseDecode(m_PosDecoders,
                                               rep0 - posSlot - 1, m_RangeDecoder, numDirectBits);
                                    }
                                    else
                                    {
                                        rep0 += (m_RangeDecoder.DecodeDirectBits(
                                            numDirectBits - Base.kNumAlignBits) << Base.kNumAlignBits);
                                        rep0 += m_PosAlignDecoder.ReverseDecode(m_RangeDecoder);
                                    }
                                }
                                else
                                {
                                    rep0 = posSlot;
                                }
                            }
                            if (rep0 >= m_OutWindow.TrainSize + nowPos64 || rep0 >= m_DictionarySizeCheck)
                            {
                                if (rep0 == 0xFFFFFFFF)
                                {
                                    break;
                                }

                                throw new DataErrorException();
                            }
                            m_OutWindow.CopyBlock(rep0, len);
                            nowPos64 += len;
                        }
                    }
                }
            }
            catch (OperationCanceledException)
            {
            }

            m_OutWindow.Flush();
            m_OutWindow.ReleaseStream();
            m_RangeDecoder.ReleaseStream();
        }

        public void SetDecoderProperties(byte[] properties)
        {
            if (properties.Length < 5)
            {
                throw new InvalidParamException();
            }

            int lc = properties[0] % 9;
            int remainder = properties[0] / 9;
            int lp = remainder % 5;
            int pb = remainder / 5;
            if (pb > Base.kNumPosStatesBitsMax)
            {
                throw new InvalidParamException();
            }

            UInt32 dictionarySize = 0;
            for (int i = 0; i < 4; i++)
            {
                dictionarySize += ((UInt32)(properties[1 + i])) << (i * 8);
            }

            SetDictionarySize(dictionarySize);
            SetLiteralProperties(lp, lc);
            SetPosBitsProperties(pb);
        }

        public bool Train(System.IO.Stream stream)
        {
            _solid = true;
            return m_OutWindow.Train(stream);
        }

        /*
		public override bool CanRead { get { return true; }}
		public override bool CanWrite { get { return true; }}
		public override bool CanSeek { get { return true; }}
		public override long Length { get { return 0; }}
		public override long Position
		{
			get { return 0;	}
			set { }
		}
		public override void Flush() { }
		public override int Read(byte[] buffer, int offset, int count) 
		{
			return 0;
		}
		public override void Write(byte[] buffer, int offset, int count)
		{
		}
		public override long Seek(long offset, System.IO.SeekOrigin origin)
		{
			return 0;
		}
		public override void SetLength(long value) {}
		*/
    }
}