/***
    Copyright (C) 2023 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: FSCompress.cpp
    Date: 2023-1-26
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "FS.hpp"
#include "FS.Generic.hpp"
#include <Source/Time/Time.hpp>

namespace Aurora::IO::FS
{
    static const AuUInt64 kFileCopyBlock = 0xFFFF * 4; // 64KiB
    static auto const kCompressionType = AuCompression::ECompressionType::eZSTD;
    static const AuString kStringSuffix = ".zst";

    static bool CompressEx2(const AuString &path, const AuString &suffix, AuCompression::ECompressionType type, AuInt8 level, bool bCheck)
    {
        static const auto kCompressionReadChunks = kFileCopyBlock;

        if (suffix.empty())
        {
            SysPushErrorInvalidArgPos2();
            return {};
        }

        if (bCheck)
        {
            if (AuEndsWith(path, suffix))
            {
                SysPushErrorIO("File path (\"{}\") ends in {}, yet was requested to be compressed. A user or a developer is probably being stupid.", path, suffix);
                return false;
            }
        }

        auto pFileSrc = OpenReadShared(path, EFileAdvisoryLockLevel::eBlockWrite);
        if (!pFileSrc)
        {
            SysPushErrorIO("Couldn't open compression source path: {}", path);
            return {};
        }

        auto pFileDest = OpenWriteShared(path + suffix, EFileAdvisoryLockLevel::eBlockReadWrite);
        if (!pFileDest)
        {
            SysPushErrorIO("Couldn't open compression destination path: {}{}", path, suffix);
            return {};
        }

        if (pFileDest->GetLength())
        {
            SysPushErrorIO("File ({}) exists", path);
            return {};
        }

        auto qwLength = pFileSrc->GetLength();

        auto pFileStream = AuMakeShared<AuIO::FS::FileReader>(pFileSrc);
        if (!pFileStream)
        {
            SysPushErrorMemory();
            return {};
        }

        auto pDestStream = AuMakeShared<AuIO::FS::FileWriter>(pFileDest);
        if (!pDestStream)
        {
            SysPushErrorMemory();
            return {};
        }

        AuCompression::CompressInfo compress { type };
        compress.uCompressionLevel = level;
        compress.uInternalStreamSize = kCompressionReadChunks * 2;
        auto pCompressor = AuCompression::CompressorUnique(pFileStream, compress);
        if (!pCompressor)
        {
            SysPushErrorMemory("no compressor");
            return {};
        }

        AuUInt64 qwTotalRead {};
        {
            AuByteBuffer tempMemory(kCompressionReadChunks);
            if (!tempMemory)
            {
                SysPushErrorMemory();
                return {};
            }

            for (AuUInt64 i = 0; i < qwLength; i += 0 /*kCompressionReadChunks*/)
            {
                auto [read, written] = pCompressor->Ingest(kCompressionReadChunks);
                i += read;

                if (read == 0)
                {
                    break;
                }

                qwTotalRead += read;

                bool bAnyWritten {};
                while (auto uBytes = pCompressor->Read(tempMemory))
                {
                    tempMemory.writePtr += uBytes;
                    bAnyWritten = true;

                    AuUInt idc {};
                    if (AuIO::WriteAll(pDestStream.get(), { tempMemory, idc }) != AuIO::EStreamError::eErrorNone)
                    {
                        SysPushErrorIO("AuIO::WriteAll failed");
                        return {};
                    }

                    tempMemory.writePtr = tempMemory.base;
                    tempMemory.readPtr = tempMemory.base;
                }

                // zstd u ok?
                // if i remove this, we get no data at all.
                // even if i try to displace this to above `->Finish()` we still get nothing
                // preemptively flushing fixes everything /shrug
                pCompressor->Flush();
            }

            pCompressor->Finish();

            while (auto uBytes = pCompressor->Read(tempMemory))
            {
                tempMemory.writePtr += uBytes;

                AuUInt idc {};
                if (AuIO::WriteAll(pDestStream.get(), { tempMemory, idc }) != AuIO::EStreamError::eErrorNone)
                {
                    SysPushErrorIO("AuIO::WriteAll failed");
                    return {};
                }

                tempMemory.writePtr = tempMemory.base;
                tempMemory.readPtr = tempMemory.base;
            }
        }

        return qwTotalRead == qwLength;
    }

    AUKN_SYM bool CompressEx(const AuString &path, const AuString &suffix, AuCompression::ECompressionType type, AuInt8 level)
    {
        return CompressEx2(path, kStringSuffix, kCompressionType, level, false);
    }

    AUKN_SYM bool Compress(const AuString &path, AuInt8 level)
    {
        return CompressEx2(path, kStringSuffix, kCompressionType, level, true);
    }

    AUKN_SYM bool DecompressEx(const AuString &path, const AuString &suffix, AuCompression::ECompressionType type)
    {
        static const auto kCompressionReadChunks = kFileCopyBlock;

        if (suffix.empty())
        {
            SysPushErrorInvalidArgPos2();
            return {};
        }

        auto pFileSrc = OpenReadShared(path + suffix, EFileAdvisoryLockLevel::eBlockWrite);
        if (!pFileSrc)
        {
            SysPushErrorIO("Couldn't open compression source path: {}{}", path, suffix);
            return {};
        }

        auto pFileDest = OpenWriteShared(path, EFileAdvisoryLockLevel::eBlockReadWrite);
        if (!pFileDest)
        {
            SysPushErrorIO("Couldn't open decompression destination path: {}", path);
            return {};
        }

        if (pFileDest->GetLength())
        {
            SysPushErrorIO("File exists path: {}", path);
            return {};
        }

        auto qwLength = pFileSrc->GetLength();

        auto pFileStream = AuMakeShared<AuIO::FS::FileReader>(pFileSrc);
        if (!pFileStream)
        {
            SysPushErrorMemory();
            return {};
        }

        auto pDestStream = AuMakeShared<AuIO::FS::FileWriter>(pFileDest);
        if (!pDestStream)
        {
            SysPushErrorMemory();
            return {};
        }

        AuCompression::DecompressInfo decompress{ type };
        decompress.uInternalStreamSize = kCompressionReadChunks * 5;
        auto pDecompressor = AuCompression::DecompressorUnique(pFileStream, decompress);
        if (!pDecompressor)
        {
            SysPushErrorMemory("no decompressor");
            return {};
        }

        AuUInt64 qwTotalRead {};
        {
            AuByteBuffer tempMemory(kCompressionReadChunks);
            if (!tempMemory)
            {
                SysPushErrorMemory();
                return {};
            }

            for (AuUInt64 i = 0; i < qwLength; i += 0 /*kCompressionReadChunks*/)
            {
                auto [read, written] = pDecompressor->Ingest(kCompressionReadChunks);
                i += read;

                if (read == 0)
                {
                    break;
                }

                qwTotalRead += read;

                while (auto uBytes = pDecompressor->Read(tempMemory))
                {
                    tempMemory.writePtr += uBytes;

                    AuUInt idc {};
                    if (AuIO::WriteAll(pDestStream.get(), { tempMemory, idc }) != AuIO::EStreamError::eErrorNone)
                    {
                        SysPushErrorIO("AuIO::WriteAll failed");
                        return {};
                    }

                    tempMemory.writePtr = tempMemory.base;
                    tempMemory.readPtr = tempMemory.base;
                }
            }
        }

        return qwTotalRead == qwLength;
    }

    AUKN_SYM bool Decompress(const AuString &path)
    {
        return DecompressEx(path, kStringSuffix, kCompressionType);
    }
}