/***
    Copyright (C) 2022 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: ZSTDCompressor.hpp
    Date: 2022-2-15
    Author: Reece
***/
#pragma once

#include "zstd.h"

namespace Aurora::Compression
{
    struct ZSTDDeflate : BaseStream
    {
        CompressInfo meta;

        ZSTDDeflate(const CompressInfo &meta) : meta(meta), BaseStream(meta.uInternalStreamSize)
        {}

        ~ZSTDDeflate()
        {
            if (auto cctx = AuExchange(this->cctx_, {}))
            {
                ZSTD_freeCCtx(cctx);
            }
        }

        bool Init(const AuSPtr<IO::IStreamReader> &pReader) override
        {
            AuUInt uRet;

            if (!this->IsValid())
            {
                SysPushErrorMem();
                return false;
            }

            this->pReader_ = pReader;
            this->cctx_ = ZSTD_createCCtx();

            if (!this->cctx_)
            {
                SysPushErrorGen("Couldn't create compressor");
            }

            uRet = ZSTD_CCtx_setParameter(this->cctx_, ZSTD_c_compressionLevel, meta.uCompressionLevel);
            if (ZSTD_isError(uRet))
            {
                SysPushErrorGen("Invalid compression level");
                return false;
            }

            uRet = ZSTD_CCtx_setParameter(this->cctx_, ZSTD_c_checksumFlag, 1);
            if (ZSTD_isError(uRet))
            {
                SysPushErrorGen("Invalid option");
                return false;
            }

            uRet = ZSTD_CCtx_setParameter(this->cctx_, ZSTD_c_nbWorkers, AuMax(meta.uThreads, AuUInt8(1u)));
            if (ZSTD_isError(uRet))
            {
                SysPushErrorGen();
                return false;
            }

            this->pIterator_ = this->din_;
            this->uAvailableIn_ = 0;
            SetArray(this->din_);
            return true;
        }

        AuStreamReadWrittenPair_t Ingest_s(AuUInt32 input) override
        {
            AuUInt32 uLength = AuUInt32(ZSTD_DStreamInSize());
            AuUInt32 uOutFrameLength = AuUInt32(ZSTD_DStreamOutSize());
            AuUInt32 done {}, read {};

            if (!this->pReader_)
            {
                return {};
            }

            while (read < input)
            {
                read += IngestForInPointer<char, AuUInt32>(this->pReader_, this->pIterator_, this->uAvailableIn_, input - read);

                if (!this->uAvailableIn_)
                {
                    Flush();
                    return {read, done};
                }

                this->input_ = ZSTD_inBuffer {this->pIterator_, this->uAvailableIn_, 0};

                size_t uRet {};

                bool bLastFrame = input - read == 0;
                
                while ((this->input_.pos != this->input_.size) ||
                       (/*bLastFrame && uRet*/ false))
                {
                    ZSTD_outBuffer output = { this->dout_, uOutFrameLength, 0 };
                    ZSTD_EndDirective mode = ZSTD_e_continue;// bLastFrame ? ZSTD_e_flush : ZSTD_e_continue;

                    uRet = ZSTD_compressStream2(this->cctx_, &output, &this->input_, mode);
                    if (ZSTD_isError(uRet))
                    {
                        SysPushErrorIO("Compression error: {}", ZSTD_getErrorName(uRet));
                        this->uAvailableIn_ -= AuUInt32(output.pos);
                        this->pReader_.reset();
                        return AuMakePair(read, 0);
                    }

                    this->bLastFrameHasNotFinished_ = bLastFrame && uRet;

                    if (!output.pos)
                    {
                        continue;
                    }

                    done += AuUInt32(output.pos);

                    if (!Write(reinterpret_cast<const AuUInt8 *>(this->dout_),
                        AuUInt32(output.pos)))
                    {
                        SysPushErrorIO("Compression Out of Overhead");
                        this->pReader_.reset();
                        return AuMakePair(read, 0);
                    }
                }

                this->pIterator_ += this->input_.pos;
                this->uAvailableIn_ -= AuUInt32(this->input_.pos);
            }

            return {read, done};
        }

        bool Flush() override
        {
            AuUInt32 uLength = AuUInt32(ZSTD_DStreamInSize());
            AuUInt32 uOutFrameLength = AuUInt32(ZSTD_DStreamOutSize());

            this->input_ = ZSTD_inBuffer { this->pIterator_, this->uAvailableIn_, 0 };

            AuUInt uRet {};
            while ((this->input_.pos < this->input_.size) ||
                   (this->bLastFrameHasNotFinished_) ||
                   (uRet))
            {
                ZSTD_outBuffer output = { this->dout_, uOutFrameLength, 0 };

                this->bLastFrameHasNotFinished_ = false;

                uRet = ZSTD_compressStream2(this->cctx_, &output, &this->input_, ZSTD_e_flush);
                if (ZSTD_isError(uRet))
                {
                    SysPushErrorIO("Compression error: {}", ZSTD_getErrorName(uRet));
                    this->uAvailableIn_ -= AuUInt32(output.pos);
                    return {};
                }

                if (!output.pos)
                {
                    continue;
                }

                if (!Write(reinterpret_cast<const AuUInt8 *>(this->dout_),
                    AuUInt32(output.pos)))
                {
                    SysPushErrorIO("Compression Out of Overhead");
                    this->pReader_.reset();
                    return false;
                }
            }

            this->pIterator_ += this->input_.pos;
            this->uAvailableIn_ -= this->input_.pos;
            return true;// RunFlush(ZSTD_e_continue);
        }

        bool Finish() override
        {
            AuUInt32 uOutFrameLength = AuUInt32(ZSTD_DStreamOutSize());
            ZSTD_outBuffer output = { this->dout_, uOutFrameLength, 0 };

            Flush();

            size_t uRet;
            do
            {
                uRet = ZSTD_endStream(this->cctx_, &output);
                if (ZSTD_isError(uRet))
                {
                    SysPushErrorIO("Compression error: {}", ZSTD_getErrorName(uRet));
                    return {};
                }

                if (!Write(reinterpret_cast<const AuUInt8 *>(this->dout_),
                    AuUInt32(output.pos)))
                {
                    SysPushErrorIO("Compression Out of Overhead");
                    return false;
                }
            }
            while (uRet);

            return true;
        }

    private:

        AuSPtr<IO::IStreamReader> pReader_;
        ZSTD_CCtx *cctx_ {};
        char din_[ZSTD_BLOCKSIZE_MAX];
        char dout_[ZSTD_COMPRESSBOUND(ZSTD_BLOCKSIZE_MAX) + 3 +/*ZSTD_BLOCKHEADERSIZE*/ + 4 /*32bit hash*/];
        char *pIterator_ {};
        AuUInt32 uAvailableIn_ {};
        ZSTD_inBuffer input_ {};
        bool bLastFrameHasNotFinished_ {};
    };
}