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

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

#include "zstd.h"

namespace Aurora::Compression
{
    struct ZSTDInflate : public BaseStream
    {
        DecompressInfo meta;

        ZSTDInflate(const DecompressInfo &meta) : meta(meta), BaseStream(meta.internalStreamSize)
        {}

        ~ZSTDInflate()
        {
            if (auto dctx = AuExchange(dctx_, {}))
            {
                ZSTD_freeDCtx(dctx);
            }
        }

        bool Init(const AuSPtr<IO::IStreamReader> &reader)
        {
            size_t ret;
            this->reader_ = reader;
            this->dctx_ = ZSTD_createDCtx();

            if (!this->dctx_)
            {
                SysPushErrorGen("Couldn't create decompressor");
                return false;
            }

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

            this->curPtr_ = this->din_;
            this->availIn_ = 0;
            SetArray(this->din_);
            return true;
        }

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

            while (read < input)
            {
                read += IngestForInPointer<char, AuUInt32>(this->reader_, this->curPtr_, this->availIn_, input - read);

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

                this->input_ = ZSTD_inBuffer {this->curPtr_, this->availIn_, 0};

                while (this->input_.pos < this->input_.size)
                {
                    ZSTD_outBuffer output = {this->dout_, outFrameLength, 0};

                    auto ret = ZSTD_decompressStream(this->dctx_, &output, &this->input_);
                    if (ZSTD_isError(ret))
                    {
                        SysPushErrorIO("Compression error: {}", ZSTD_getErrorName(ret));
                        this->availIn_ -= output.pos;
                        return AuMakePair(read, 0);
                    }

                    done += output.pos;

                    if (!Write(reinterpret_cast<const AuUInt8 *>(output.dst),
                               output.pos))
                    {
                        return AuMakePair(read, 0);
                    }
                }

                this->availIn_ -= this->input_.pos;
            }

            return {read, done};
        }

    private:

        AuSPtr<IO::IStreamReader> reader_;
        ZSTD_DCtx *dctx_;
        char din_[ZSTD_BLOCKSIZE_MAX + 3 /*ZSTD_BLOCKHEADERSIZE*/];
        char dout_[ZSTD_BLOCKSIZE_MAX];
        char *curPtr_;
        AuUInt32 availIn_;
        ZSTD_inBuffer input_;
    };
}