#include <mesytec-mvlc/mesytec-mvlc.h>
#include <nng/nng.h>

using namespace mesytec;
using namespace mesytec::mvlc;

// Follows the framing structure inside the buffer until an incomplete frame
// which doesn't fit into the buffer is detected. The incomplete data is moved
// over to the tempBuffer so that the readBuffer ends with a complete frame.
//
// The input buffer must start with a frame header (skip_count will be called
// with the first word of the input buffer on the first iteration).
//
// The SkipCountFunc must return the number of words to skip to get to the next
// frame header or 0 if there is not enough data left in the input iterator to
// determine the frames size.
// Signature of SkipCountFunc:  u32 skip_count(const basic_string_view<const u8> &view);
// Returns the number of trailing bytes copied from msgBuf into tmpBuf.
template<typename SkipCountFunc>
inline size_t fixup_buffer(
    const u8 *msgBuf, size_t msgUsed,
    std::vector<u8> &tmpBuf,
    SkipCountFunc skip_count)
{
    auto view = basic_string_view<const u8>(msgBuf, msgUsed);

    while (!view.empty())
    {
        if (view.size() >= sizeof(u32))
        {
            u32 wordsToSkip = skip_count(view);

            //cout << "wordsToSkip=" << wordsToSkip << ", view.size()=" << view.size() << ", in words:" << view.size() / sizeof(u32));

            if (wordsToSkip == 0 || wordsToSkip > view.size() / sizeof(u32))
            {
                tmpBuf.reserve(tmpBuf.size() + view.size());
                std::copy(std::begin(view), std::end(view), std::back_inserter(tmpBuf));
                return view.size();
            }

            // Skip over the SystemEvent frame or the ETH packet data.
            view.remove_prefix(wordsToSkip * sizeof(u32));
        }
    }

    return 0u;
}

inline size_t fixup_buffer_mvlc_usb(const u8 *buf, size_t bufUsed, std::vector<u8> &tmpBuf)
{
    auto skip_func = [] (const basic_string_view<const u8> &view) -> u32
    {
        if (view.size() < sizeof(u32))
            return 0u;

        u32 header = *reinterpret_cast<const u32 *>(view.data());
        return 1u + extract_frame_info(header).len;
    };

    return fixup_buffer(buf, bufUsed, tmpBuf, skip_func);
}

inline size_t fixup_buffer_mvlc_eth(const u8 *buf, size_t bufUsed, std::vector<u8> &tmpBuf)
{
    auto skip_func = [](const basic_string_view<const u8> &view) -> u32
    {
        if (view.size() < sizeof(u32))
            return 0u;

        // Either a SystemEvent header or the first of the two ETH packet headers
        u32 header = *reinterpret_cast<const u32 *>(view.data());

        if (get_frame_type(header) == frame_headers::SystemEvent)
            return 1u + extract_frame_info(header).len;

        if (view.size() >= 2 * sizeof(u32))
        {
            u32 header1 = *reinterpret_cast<const u32 *>(view.data() + sizeof(u32));
            eth::PayloadHeaderInfo ethHdrs{ header, header1 };
            return eth::HeaderWords + ethHdrs.dataWordCount();
        }

        // Not enough data to get the 2nd ETH header word.
        return 0u;
    };

    return fixup_buffer(buf, bufUsed, tmpBuf, skip_func);
}

enum class BufferType: u32
{
    MVLC_USB,
    MVLC_ETH,
};

#pragma pack(push, 1)
struct BufferMessageHeader
{
    u32 bufferType;
    u32 bufferNumber;
};

#pragma pack(pop)

size_t fixup_listfile_buffer_message(const BufferType &bufferType, nng_msg *msg, size_t msgUsed, std::vector<u8> &tmpBuf)
{
    size_t bytesMoved = 0u;
    const u8 *msgBufferData = reinterpret_cast<const u8 *>(nng_msg_body(msg)) + sizeof(BufferMessageHeader);
    const auto msgBufferSize = msgUsed - sizeof(BufferMessageHeader);

    if (bufferType == BufferType::MVLC_USB)
        bytesMoved = fixup_buffer_mvlc_usb(msgBufferData, msgBufferSize, tmpBuf);
    else
        bytesMoved = fixup_buffer_mvlc_eth(msgBufferData, msgBufferSize, tmpBuf);

    nng_msg_chop(msg, msgUsed - bytesMoved);
    return msgUsed - bytesMoved;
}

void listfile_reader_produer(
    nng_socket socket,
    mvlc::listfile::ReadHandle &input)
{
    try
    {
        auto preamble = mvlc::listfile::read_preamble(input);
        auto bufferType = BufferType::MVLC_USB;
        if (preamble.magic == mvlc::listfile::get_filemagic_eth())
            bufferType = BufferType::MVLC_ETH;
        u32 bufferNumber = 0u;
        std::vector<u8> previousData;

        while (true)
        {
            nng_msg *msg = {};
            if (int res = nng_msg_alloc(&msg, util::Megabytes(1)))
            {
                spdlog::error("nng_msg_alloc: {}", nng_strerror(res));
                return;
            }

            BufferMessageHeader msgHeader = {};
            msgHeader.bufferType = static_cast<u32>(bufferType);
            msgHeader.bufferNumber = bufferNumber;
            nng_msg_append(msg, &msgHeader, sizeof(msgHeader));
            size_t msgUsed = sizeof(msgHeader);

            std::copy(std::begin(previousData), std::end(previousData),
                reinterpret_cast<u8 *>(nng_msg_body(msg)) + msgUsed);
            msgUsed += previousData.size();
            previousData.clear();

            size_t bytesRead = input.read(
                reinterpret_cast<u8 *>(nng_msg_body(msg)) + msgUsed,
                nng_msg_len(msg) - msgUsed);
            msgUsed += bytesRead;
            msgUsed = fixup_listfile_buffer_message(bufferType, msg, msgUsed, previousData);
            assert(msgUsed == nng_msg_len(msg));

            if (bytesRead == 0 && nng_msg_len(msg) == sizeof(BufferMessageHeader))
            {
                nng_msg_free(msg);
                return;
            }
            else if (auto res = nng_sendmsg(socket, msg, 0))
            {
                // TODO: how to handle blocking here? need some way to ensure
                // nng_sendmsg() returns
                // -> maybe: timeout and loop with check if the producer should quit
                spdlog::error("nng_sendmsg: {}", nng_strerror(res));
                nng_msg_free(msg);
                return;
            }
        }
    }
    catch(const std::exception& e)
    {
        spdlog::error(e.what());
        return;
    }
}

int main(int argc, char *argv[])
{
    if (argc < 2)
        return 1;

    try
    {
        listfile::ZipReader zipReader;
        zipReader.openArchive(argv[1]);
        auto readHandle = zipReader.openEntry(zipReader.firstListfileEntryName());
    }
    catch(const std::exception& e)
    {
        spdlog::error("exception in main(): {}", e.what());
        return 1;
    }

    return 0;
}