/* Copyright (C) Teemu Suutari */

#include "SQSHDecompressor.hpp"
#include "InputStream.hpp"
#include "OutputStream.hpp"
#include "HuffmanDecoder.hpp"
#include "common/Common.hpp"


namespace ancient::internal
{

bool SQSHDecompressor::detectHeaderXPK(uint32_t hdr) noexcept
{
	return hdr==FourCC("SQSH");
}

std::shared_ptr<XPKDecompressor> SQSHDecompressor::create(uint32_t hdr,uint32_t recursionLevel,const Buffer &packedData,std::shared_ptr<XPKDecompressor::State> &state,bool verify)
{
	return std::make_shared<SQSHDecompressor>(hdr,recursionLevel,packedData,state,verify);
}

SQSHDecompressor::SQSHDecompressor(uint32_t hdr,uint32_t recursionLevel,const Buffer &packedData,std::shared_ptr<XPKDecompressor::State> &state,bool verify) :
	XPKDecompressor(recursionLevel),
	_packedData(packedData)
{
	if (!detectHeaderXPK(hdr) || packedData.size()<3) throw Decompressor::InvalidFormatError();
	_rawSize=packedData.readBE16(0);
	if (!_rawSize) throw Decompressor::InvalidFormatError();
}

SQSHDecompressor::~SQSHDecompressor()
{
	// nothing needed
}

const std::string &SQSHDecompressor::getSubName() const noexcept
{
	static std::string name="XPK-SQSH: Compressor for sampled sounds";
	return name;
}
	
void SQSHDecompressor::decompressImpl(Buffer &rawData,const Buffer &previousData,bool verify)
{
	if (rawData.size()!=_rawSize) throw Decompressor::DecompressionError();

	ForwardInputStream inputStream(_packedData,2,_packedData.size());
	MSBBitReader<ForwardInputStream> bitReader(inputStream);
	auto readBits=[&](uint32_t count)->uint32_t
	{
		return bitReader.readBits8(count);
	};
	auto readSignedBits=[&](uint8_t bits)->int32_t
	{
		int32_t ret=readBits(bits);
		if (ret&(1<<(bits-1)))
			ret|=~0U<<bits;
		return ret;
	};
	auto readBit=[&]()->uint32_t
	{
		return bitReader.readBits8(1);
	};
	auto readByte=[&]()->uint8_t
	{
		return inputStream.readByte();
	};

	ForwardOutputStream outputStream(rawData,0,_rawSize);

	HuffmanDecoder<uint8_t> modDecoder
	{
		HuffmanCode<uint8_t>{1,0b0001,0},
		HuffmanCode<uint8_t>{2,0b0000,1},
		HuffmanCode<uint8_t>{3,0b0010,2},
		HuffmanCode<uint8_t>{4,0b0110,3},
		HuffmanCode<uint8_t>{4,0b0111,4}
	};

	HuffmanDecoder<uint8_t> lengthDecoder
	{
		HuffmanCode<uint8_t>{1,0b0000,0},
		HuffmanCode<uint8_t>{2,0b0010,1},
		HuffmanCode<uint8_t>{3,0b0110,2},
		HuffmanCode<uint8_t>{4,0b1110,3},
		HuffmanCode<uint8_t>{4,0b1111,4}
	};

	HuffmanDecoder<uint8_t> distanceDecoder
	{
		HuffmanCode<uint8_t>{1,0b01,0},
		HuffmanCode<uint8_t>{2,0b00,1},
		HuffmanCode<uint8_t>{2,0b01,2}
	};

	// first byte is special
	uint8_t currentSample=readByte();
	outputStream.writeByte(currentSample);

	uint32_t accum1=0,accum2=0,prevBits=0;

	while (!outputStream.eof())
	{
		uint8_t bits=0;
		uint32_t count=0;
		bool doRepeat=false;

		if (accum1>=8)
		{
			static const uint8_t bitLengthTable[7][8]={
				{2,3,4,5,6,7,8,0},
				{3,2,4,5,6,7,8,0},
				{4,3,5,2,6,7,8,0},
				{5,4,6,2,3,7,8,0},
				{6,5,7,2,3,4,8,0},
				{7,6,8,2,3,4,5,0},
				{8,7,6,2,3,4,5,0}};

			auto handleCondCase=[&]()
			{
				if (bits==8) {
					if (accum2<20)
					{
						count=1;
					} else {
						count=2;
						accum2+=8;
					}
				} else {
					count=5;
					accum2+=8;
				}
			};

			auto handleTable=[&](uint32_t newBits)
			{
				if (prevBits<2 || !newBits) throw Decompressor::DecompressionError();
				bits=bitLengthTable[prevBits-2][newBits-1];
				if (!bits) throw Decompressor::DecompressionError();
				handleCondCase();
			};

			uint32_t mod=modDecoder.decode(readBit);
			switch (mod)
			{
				case 0:
				if (prevBits==8)
				{
					bits=8;
					handleCondCase();
				} else {
					bits=prevBits;
					count=5;
					accum2+=8;
				}
				break;

				case 1:
				doRepeat=true;
				break;

				case 2:
				handleTable(2);
				break;

				case 3:
				handleTable(3);
				break;

				case 4:
				handleTable(readBits(2)+4);
				break;

				default:
				throw Decompressor::DecompressionError();
			}
		} else {
			if (readBit())
			{
				doRepeat=true;
			} else {
				count=1;
				bits=8;
			}
		}

		if (doRepeat) {
			uint32_t lengthIndex=lengthDecoder.decode(readBit);
			static const uint8_t lengthBits[5]={1,1,1,3,5};
			static const uint32_t lengthAdditions[5]={2,4,6,8,16};
			count=readBits(lengthBits[lengthIndex])+lengthAdditions[lengthIndex];
			if (count>=3)
			{
				if (accum1) accum1--;
				if (count>3 && accum1) accum1--;
			}
			uint32_t distanceIndex=distanceDecoder.decode(readBit);
			static const uint8_t distanceBits[3]={12,8,14};
			static const uint32_t distanceAdditions[3]={0x101,1,0x1101};
			uint32_t distance=readBits(distanceBits[distanceIndex])+distanceAdditions[distanceIndex];
			count=std::min(count,uint32_t(_rawSize-outputStream.getOffset()));
			currentSample=outputStream.copy(distance,count);
		} else {
			count=std::min(count,uint32_t(_rawSize-outputStream.getOffset()));
			for (uint32_t i=0;i<count;i++)
			{
				currentSample-=readSignedBits(bits);
				outputStream.writeByte(currentSample);
			}
			if (accum1!=31) accum1++;
			prevBits=bits;
		}

		accum2-=accum2>>3;
	}
}

}