/*****************************************************************************
 * Copyright (c) 2014-2026 OpenRCT2 developers
 *
 * For a complete list of all authors, please refer to contributors.md
 * Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
 *
 * OpenRCT2 is licensed under the GNU General Public License version 3.
 *****************************************************************************/

#include "SawyerChunkWriter.h"

#include "../core/IStream.hpp"
#include "../core/Numerics.hpp"
#include "../sawyer_coding/SawyerCoding.h"

namespace OpenRCT2::SawyerCoding
{
    // Maximum buffer size to store compressed data, maximum of 16 MiB
    constexpr size_t MAX_COMPRESSED_CHUNK_SIZE = 16 * 1024 * 1024;

    SawyerChunkWriter::SawyerChunkWriter(IStream* stream)
        : _stream(stream)
    {
    }

    void SawyerChunkWriter::WriteChunk(const SawyerChunk* chunk)
    {
        WriteChunk(chunk->GetData(), chunk->GetLength(), chunk->GetEncoding());
    }

    void SawyerChunkWriter::WriteChunk(const void* src, size_t length, ChunkEncoding encoding)
    {
        ChunkHeader header;
        header.encoding = encoding;
        header.length = static_cast<uint32_t>(length);

        auto data = std::make_unique<uint8_t[]>(MAX_COMPRESSED_CHUNK_SIZE);
        size_t dataLength = WriteChunkBuffer(data.get(), static_cast<const uint8_t*>(src), header);

        _stream->Write(data.get(), dataLength);
    }

    /**
     * Ensure dst_buffer is bigger than src_buffer then resize afterwards
     * returns length of dst_buffer
     */
    static size_t EncodeChunkRLE(const uint8_t* src_buffer, uint8_t* dst_buffer, size_t length)
    {
        const uint8_t* src = src_buffer;
        uint8_t* dst = dst_buffer;
        const uint8_t* end_src = src + length;
        uint8_t count = 0;
        const uint8_t* src_norm_start = src;

        while (src < end_src - 1)
        {
            if ((count && *src == src[1]) || count > 125)
            {
                *dst++ = count - 1;
                std::memcpy(dst, src_norm_start, count);
                dst += count;
                src_norm_start += count;
                count = 0;
            }
            if (*src == src[1])
            {
                for (; (count < 125) && ((src + count) < end_src); count++)
                {
                    if (*src != src[count])
                        break;
                }
                *dst++ = 257 - count;
                *dst++ = *src;
                src += count;
                src_norm_start = src;
                count = 0;
            }
            else
            {
                count++;
                src++;
            }
        }
        if (src == end_src - 1)
            count++;
        if (count)
        {
            *dst++ = count - 1;
            std::memcpy(dst, src_norm_start, count);
            dst += count;
        }
        return dst - dst_buffer;
    }

    void SawyerChunkWriter::WriteChunkTrack(const void* src, size_t length)
    {
        auto data = std::make_unique<uint8_t[]>(MAX_COMPRESSED_CHUNK_SIZE);
        size_t dataLength = EncodeChunkRLE(static_cast<const uint8_t*>(src), data.get(), length);

        uint32_t checksum = 0;
        for (size_t i = 0; i < dataLength; i++)
        {
            uint8_t newByte = ((checksum & 0xFF) + data[i]) & 0xFF;
            checksum = (checksum & 0xFFFFFF00) + newByte;
            checksum = Numerics::rol32(checksum, 3);
        }
        checksum -= 0x1D4C1;

        _stream->Write(data.get(), dataLength);
        _stream->WriteValue<uint32_t>(checksum);
    }
} // namespace OpenRCT2::SawyerCoding
