#include "NVMeBasicContext.hpp"

#include <endian.h>
#include <sys/ioctl.h>
#include <unistd.h>

#include <FileHandle.hpp>
#include <boost/asio/read.hpp>
#include <boost/asio/streambuf.hpp>
#include <boost/asio/write.hpp>

#include <cassert>
#include <cerrno>
#include <cinttypes>
#include <cstdio>
#include <cstring>
#include <system_error>
#include <thread>

extern "C"
{
#include <i2c/smbus.h>
#include <linux/i2c-dev.h>
}

/*
 * NVMe-MI Basic Management Command
 *
 * https://nvmexpress.org/wp-content/uploads/NVMe_Management_-_Technical_Note_on_Basic_Management_Command.pdf
 */

static std::shared_ptr<std::array<uint8_t, 6>>
    encodeBasicQuery(int bus, uint8_t device, uint8_t offset)
{
    if (bus < 0)
    {
        throw std::domain_error("Invalid bus argument");
    }

    /* bus + address + command */
    uint32_t busle = htole32(static_cast<uint32_t>(bus));
    auto command =
        std::make_shared<std::array<uint8_t, sizeof(busle) + 1 + 1>>();
    memcpy(command->data(), &busle, sizeof(busle));
    (*command)[sizeof(busle) + 0] = device;
    (*command)[sizeof(busle) + 1] = offset;

    return command;
}

static void decodeBasicQuery(const std::array<uint8_t, 6>& req, int& bus,
                             uint8_t& device, uint8_t& offset)
{
    uint32_t busle = 0;

    memcpy(&busle, req.data(), sizeof(busle));
    bus = le32toh(busle);
    device = req[sizeof(busle) + 0];
    offset = req[sizeof(busle) + 1];
}

static ssize_t execBasicQuery(int bus, uint8_t addr, uint8_t cmd,
                              std::vector<uint8_t>& resp)
{
    int32_t size = 0;
    std::filesystem::path devpath = "/dev/i2c-" + std::to_string(bus);
    FileHandle fileHandle(devpath);

    /* Select the target device */
    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-vararg)
    if (::ioctl(fileHandle.handle(), I2C_SLAVE, addr) == -1)
    {
        std::cerr << "Failed to configure device address 0x" << std::hex
                  << (int)addr << " for bus " << std::dec << bus << ": "
                  << strerror(errno) << "\n";

        return -errno;
    }

    resp.reserve(UINT8_MAX + 1);

    /* Issue the NVMe MI basic command */
    size = i2c_smbus_read_block_data(fileHandle.handle(), cmd, resp.data());
    if (size < 0)
    {
        std::cerr << "Failed to read block data from device 0x" << std::hex
                  << (int)addr << " on bus " << std::dec << bus << ": "
                  << strerror(errno) << "\n";
        return size;
    }
    if (size > UINT8_MAX + 1)
    {
        std::cerr << "Unexpected message length from device 0x" << std::hex
                  << (int)addr << " on bus " << std::dec << bus << ": " << size
                  << " (" << UINT8_MAX << ")\n";
        return -EBADMSG;
    }

    return size;
}

static ssize_t processBasicQueryStream(FileHandle& in, FileHandle& out)
{
    std::vector<uint8_t> resp{};
    ssize_t rc = 0;

    while (true)
    {
        uint8_t device = 0;
        uint8_t offset = 0;
        uint8_t len = 0;
        int bus = 0;

        /* bus + address + command */
        std::array<uint8_t, sizeof(uint32_t) + 1 + 1> req{};

        /* Read the command parameters */
        ssize_t rc = ::read(in.handle(), req.data(), req.size());
        if (rc != static_cast<ssize_t>(req.size()))
        {
            std::cerr << "Failed to read request from in descriptor "
                      << strerror(errno) << "\n";
            if (rc)
            {
                return -errno;
            }
            return -EIO;
        }

        decodeBasicQuery(req, bus, device, offset);

        /* Execute the query */
        rc = execBasicQuery(bus, device, offset, resp);

        /* Bounds check the response */
        if (rc < 0)
        {
            len = 0;
        }
        else if (rc > UINT8_MAX)
        {
            assert(rc == UINT8_MAX + 1);

            /* YOLO: Lop off the PEC */
            len = UINT8_MAX;
        }
        else
        {
            len = rc;
        }

        /* Write out the response length */
        rc = ::write(out.handle(), &len, sizeof(len));
        if (rc != sizeof(len))
        {
            std::cerr << "Failed to write block (" << std::dec << len
                      << ") length to out descriptor: "
                      << strerror(static_cast<int>(-rc)) << "\n";
            if (rc)
            {
                return -errno;
            }
            return -EIO;
        }

        /* Write out the response data */
        std::vector<uint8_t>::iterator cursor = resp.begin();
        while (cursor != resp.end())
        {
            size_t lenRemaining = std::distance(cursor, resp.end());
            ssize_t egress = ::write(out.handle(), &(*cursor), lenRemaining);
            if (egress == -1)
            {
                std::cerr << "Failed to write block data of length " << std::dec
                          << lenRemaining << " to out pipe: " << strerror(errno)
                          << "\n";
                if (rc)
                {
                    return -errno;
                }
                return -EIO;
            }

            cursor += egress;
        }
    }

    return rc;
}

/* Throws std::error_code on failure */
/* FIXME: Probably shouldn't do fallible stuff in a constructor */
NVMeBasicContext::NVMeBasicContext(boost::asio::io_service& io, int rootBus) :
    NVMeContext::NVMeContext(io, rootBus), io(io), reqStream(io), respStream(io)
{
    std::array<int, 2> responsePipe{};
    std::array<int, 2> requestPipe{};

    /* Set up inter-thread communication */
    if (::pipe(requestPipe.data()) == -1)
    {
        std::cerr << "Failed to create request pipe: " << strerror(errno)
                  << "\n";
        throw std::error_code(errno, std::system_category());
    }

    if (::pipe(responsePipe.data()) == -1)
    {
        std::cerr << "Failed to create response pipe: " << strerror(errno)
                  << "\n";

        if (::close(requestPipe[0]) == -1)
        {
            std::cerr << "Failed to close write fd of request pipe: "
                      << strerror(errno) << "\n";
        }

        if (::close(requestPipe[1]) == -1)
        {
            std::cerr << "Failed to close read fd of request pipe: "
                      << strerror(errno) << "\n";
        }

        throw std::error_code(errno, std::system_category());
    }

    reqStream.assign(requestPipe[1]);
    FileHandle streamIn(requestPipe[0]);
    FileHandle streamOut(responsePipe[1]);
    respStream.assign(responsePipe[0]);

    std::thread thread([streamIn{std::move(streamIn)},
                        streamOut{std::move(streamOut)}]() mutable {
        ssize_t rc = 0;

        if ((rc = processBasicQueryStream(streamIn, streamOut)) < 0)
        {
            std::cerr << "Failure while processing query stream: "
                      << strerror(static_cast<int>(-rc)) << "\n";
        }

        std::cerr << "Terminating basic query thread\n";
    });
    thread.detach();
}

void NVMeBasicContext::readAndProcessNVMeSensor(
    std::list<std::shared_ptr<NVMeSensor>>::iterator iter)
{
    if (iter == sensors.end())
    {
        this->pollNVMeDevices();
        return;
    }

    std::shared_ptr<NVMeSensor> sensor = *iter++;

    if (!sensor->readingStateGood())
    {
        sensor->markAvailable(false);
        sensor->updateValue(std::numeric_limits<double>::quiet_NaN());
        readAndProcessNVMeSensor(iter);
        return;
    }

    /* Potentially defer sampling the sensor sensor if it is in error */
    if (!sensor->sample())
    {
        readAndProcessNVMeSensor(iter);
        return;
    }

    auto command = encodeBasicQuery(sensor->bus, 0x6a, 0x00);

    /* Issue the request */
    boost::asio::async_write(
        reqStream, boost::asio::buffer(command->data(), command->size()),
        [command](boost::system::error_code ec, std::size_t) {
            if (ec)
            {
                std::cerr << "Got error writing basic query: " << ec << "\n";
            }
        });

    auto response = std::make_shared<boost::asio::streambuf>();
    response->prepare(1);

    /* Gather the response and dispatch for parsing */
    boost::asio::async_read(
        respStream, *response,
        [response](const boost::system::error_code& ec, std::size_t n) {
            if (ec)
            {
                std::cerr << "Got error completing basic query: " << ec << "\n";
                return static_cast<std::size_t>(0);
            }

            if (n == 0)
            {
                return static_cast<std::size_t>(1);
            }

            std::istream is(response.get());
            size_t len = static_cast<std::size_t>(is.peek());

            if (n > len + 1)
            {
                std::cerr << "Query stream has become unsynchronised: "
                          << "n: " << n << ", "
                          << "len: " << len << "\n";
                return static_cast<std::size_t>(0);
            }

            if (n == len + 1)
            {
                return static_cast<std::size_t>(0);
            }

            if (n > 1)
            {
                return len + 1 - n;
            }

            response->prepare(len);
            return len;
        },
        [self{shared_from_this()}, iter, sensor, response](
            const boost::system::error_code& ec, std::size_t length) mutable {
            if (ec)
            {
                std::cerr << "Got error reading basic query: " << ec << "\n";
                return;
            }

            if (length == 0)
            {
                std::cerr << "Invalid message length: " << length << "\n";
                return;
            }

            /* Deserialise the response */
            response->consume(1); /* Drop the length byte */
            std::istream is(response.get());
            std::vector<char> data(response->size());
            is.read(data.data(), response->size());

            /* Update the sensor */
            self->processResponse(sensor, data.data(), data.size());

            /* Enqueue processing of the next sensor */
            self->readAndProcessNVMeSensor(iter);
        });
}

void NVMeBasicContext::pollNVMeDevices()
{
    auto scan = sensors.begin();

    scanTimer.expires_from_now(boost::posix_time::seconds(1));
    scanTimer.async_wait([self{shared_from_this()},
                          scan](const boost::system::error_code errorCode) {
        if (errorCode == boost::asio::error::operation_aborted)
        {
            return;
        }

        if (errorCode)
        {
            std::cerr << errorCode.message() << "\n";
            return;
        }

        self->readAndProcessNVMeSensor(scan);
    });
}

static double getTemperatureReading(int8_t reading)
{
    if (reading == static_cast<int8_t>(0x80) ||
        reading == static_cast<int8_t>(0x81))
    {
        // 0x80 = No temperature data or temperature data is more the 5 s
        // old 0x81 = Temperature sensor failure
        return std::numeric_limits<double>::quiet_NaN();
    }

    return reading;
}

void NVMeBasicContext::processResponse(std::shared_ptr<NVMeSensor>& sensor,
                                       void* msg, size_t len)
{
    if (msg == nullptr || len < 6)
    {
        sensor->incrementError();
        return;
    }

    uint8_t* messageData = static_cast<uint8_t*>(msg);
    double value = getTemperatureReading(messageData[2]);
    if (!std::isfinite(value))
    {
        sensor->incrementError();
        return;
    }

    sensor->updateValue(value);
}