#pragma once

/*                          MOUNT CONTROL COMPONENTS LIBRARY                            */


/*                          IMPLEMENTATION OF TELEMETRY CLASS                           */


#include <condition_variable>
#include <future>
#include <mutex>
#include <thread>

#include "mcc_defaults.h"

namespace mcc
{

static constexpr double mcc_sideral_to_UT1_ratio = 1.002737909350795;  // sideral/UT1


enum MccTelemetryErrorCode : int {
    ERROR_OK,
    ERROR_NULLPTR,
    ERROR_COORD_TRANSFORM,
    ERROR_PCM_COMP,
    ERROR_HARDWARE_GETPOS,
    ERROR_UPDATE_STOPPED,
    ERROR_DATA_TIMEOUT
};

}  // namespace mcc

namespace std
{

template <>
class is_error_code_enum<mcc::MccTelemetryErrorCode> : public true_type
{
};

}  // namespace std


namespace mcc
{

/*  error category definition  */

// error category
struct MccTelemetryCategory : public std::error_category {
    MccTelemetryCategory() : std::error_category() {}

    const char* name() const noexcept
    {
        return "ALTITUDE-LIMIT-PZ";
    }

    std::string message(int ec) const
    {
        MccTelemetryErrorCode err = static_cast<MccTelemetryErrorCode>(ec);

        switch (err) {
            case MccTelemetryErrorCode::ERROR_OK:
                return "OK";
            case MccTelemetryErrorCode::ERROR_NULLPTR:
                return "nullptr input argument";
            case MccTelemetryErrorCode::ERROR_COORD_TRANSFORM:
                return "coordinate transformation error";
            case MccTelemetryErrorCode::ERROR_PCM_COMP:
                return "PCM computation error";
            case MccTelemetryErrorCode::ERROR_HARDWARE_GETPOS:
                return "cannot get hardware position";
            case MccTelemetryErrorCode::ERROR_UPDATE_STOPPED:
                return "telemetry update was stopped";
            case MccTelemetryErrorCode::ERROR_DATA_TIMEOUT:
                return "a timeout occured while waiting for new data";
            default:
                return "UNKNOWN";
        }
    }

    static const MccTelemetryCategory& get()
    {
        static const MccTelemetryCategory constInst;
        return constInst;
    }
};


inline std::error_code make_error_code(MccTelemetryErrorCode ec)
{
    return std::error_code(static_cast<int>(ec), MccTelemetryCategory::get());
}


/*  TELEMETRY UPDATE POLICY  */

enum class MccTelemetryUpdatePolicy : int { TEMETRY_UPDATE_INNER, TEMETRY_UPDATE_EXTERNAL };


template <MccTelemetryUpdatePolicy UPDATE_POLICY = MccTelemetryUpdatePolicy::TEMETRY_UPDATE_INNER>
class MccTelemetry : public mcc_telemetry_interface_t<std::error_code>
{
public:
    static constexpr MccTelemetryUpdatePolicy updatePolicy = UPDATE_POLICY;

    typedef std::error_code error_t;


    MccTelemetry(mcc_ccte_c auto* ccte, mcc_PCM_c auto* pcm, mcc_hardware_c auto* hardware)
        : _updated(false), _data(), _updateMutex(new std::mutex), _updateCondVar(new std::condition_variable)
    {
        _data.target.pair_kind = MccCoordPairKind::COORDS_KIND_RADEC_ICRS;

        using ccte_t = std::remove_cvref_t<decltype(*ccte)>;
        using pcm_t = std::remove_cvref_t<decltype(*pcm)>;
        using hardware_t = std::remove_cvref_t<decltype(*hardware)>;


        _updateTargetFunc = [ccte, pcm, this](bool only_hw, std::stop_token stop_token) -> error_t {
            if (!only_hw) {
                //
                // compute apparent coordinates
                // ICRS coordinates of the taget must be already set
                //
                _data.target.time_point =
                    std::chrono::time_point_cast<typename decltype(_data.target.time_point)::duration>(
                        _data.time_point);

                _data.target.pair_kind = MccCoordPairKind::COORDS_KIND_RADEC_ICRS;
                _data.target.X = _data.target.RA_ICRS;
                _data.target.Y = _data.target.DEC_ICRS;

                // update apparent cordinates
                auto ccte_err = ccte->transformCoordinates(_data.target, &_data.target);
                if (ccte_err) {
                    return mcc_deduce_error<error_t>(ccte_err, MccTelemetryErrorCode::ERROR_COORD_TRANSFORM);
                }
            }

            if (stop_token.stop_requested()) {
                return MccTelemetryErrorCode::ERROR_UPDATE_STOPPED;
            }


            // compute hardware coordinates
            // WARNING: It is assumed here that PCM corrections have small (arcseconds-arcminutes) values
            //          since ususaly there is no reverse transformation for "hardware-to-apparent" relation!
            typename pcm_t::error_t pcm_err;

            struct {
                double dx, dy;
            } pcm_res;


            MccCelestialPoint pt;
            pt.time_point =
                std::chrono::time_point_cast<typename decltype(pt.time_point)::duration>(_data.target.time_point);

            if constexpr (mccIsEquatorialMount(pcm_t::mountType)) {
                pt.pair_kind = MccCoordPairKind::COORDS_KIND_HADEC_APP;
                pt.X = _data.target.HA;
                pt.Y = _data.target.DEC_APP;
                pcm_err = pcm->compute(std::move(pt), &pcm_res);
                if (!pcm_err) {
                    _data.target.X = _data.target.HA - pcm_res.dx;
                    _data.target.Y = _data.target.DEC_APP - pcm_res.dy;
                }
            } else if constexpr (mccIsAltAzMount(pcm_t::mountType)) {
                pt.pair_kind = MccCoordPairKind::COORDS_KIND_AZALT;
                pt.X = _data.target.AZ;
                pt.Y = _data.target.ALT;
                pcm_err = pcm->compute(std::move(pt), &pcm_res);
                if (!pcm_err) {
                    _data.target.X = _data.target.AZ - pcm_res.dx;
                    _data.target.Y = _data.target.ALT - pcm_res.dy;
                }
            } else {
                static_assert(false, "UNKNOWN MOUNT TYPE!");
            }

            if (pcm_err) {
                return mcc_deduce_error<error_t>(pcm_err, MccTelemetryErrorCode::ERROR_PCM_COMP);
            }


            return MccTelemetryErrorCode::ERROR_OK;
        };

        _updateFunc = [ccte, pcm, hardware, this](std::stop_token stop_token) {
            // first, update mount quantities
            typename hardware_t::axes_pos_t hw_pos;
            auto hw_err = hardware->getPos(&hw_pos);
            if (hw_err) {
                return mcc_deduce_error(hw_err, MccTelemetryErrorCode::ERROR_HARDWARE_GETPOS);
            }

            if (stop_token.stop_requested()) {
                return MccTelemetryErrorCode::ERROR_UPDATE_STOPPED;
            }

            double eo;

            _data.time_point =
                std::chrono::time_point_cast<typename decltype(_data.time_point)::duration>(hw_pos.time_point);

            auto ccte_err = ccte->timepointToJulday(_data.time_point, &_data.JD);
            if (!ccte_err) {
                if (stop_token.stop_requested()) {
                    return MccTelemetryErrorCode::ERROR_UPDATE_STOPPED;
                }

                ccte_err = ccte->juldayToAppSideral(_data.JD, &_data.LST, true);
                if (!ccte_err) {
                    if (stop_token.stop_requested()) {
                        return MccTelemetryErrorCode::ERROR_UPDATE_STOPPED;
                    }

                    ccte_err = ccte->equationOrigins(_data.JD, &eo);
                }
            }

            if (ccte_err) {
                return mcc_deduce_error(ccte_err, MccTelemetryErrorCode::ERROR_COORD_TRANSFORM);
            }

            if (stop_token.stop_requested()) {
                return MccTelemetryErrorCode::ERROR_UPDATE_STOPPED;
            }

            _data.speedX = (double)hw_pos.speedX;
            _data.speedY = (double)hw_pos.speedY;

            struct {
                double dx, dy;
            } pcm_res;

            auto pcm_err = pcm->computePCM(_data, &pcm_res);
            if (pcm_err) {
                return mcc_deduce_error(pcm_err, MccTelemetryErrorCode::ERROR_PCM_COMP);
            }

            _data.pcmX = pcm_res.dx;
            _data.pcmY = pcm_res.dy;

            if (stop_token.stop_requested()) {
                return MccTelemetryErrorCode::ERROR_UPDATE_STOPPED;
            }

            MccCelestialPoint pt{.pair_kind = MccCoordPairKind::COORDS_KIND_AZALT, .time_point = _data.time_point};

            if constexpr (mccIsEquatorialMount(pcm_t::mountType)) {
                _data.HA = (double)hw_pos.X + pcm_res.dx;
                _data.DEC_APP = (double)hw_pos.Y + pcm_res.dy;
                _data.RA_APP = (double)_data.LST - (double)_data.HA + eo;

                _data.X = _data.HA;
                _data.Y = _data.DEC_APP;

                _data.pair_kind = MccCoordPairKind::COORDS_KIND_HADEC_APP;

                ccte_err = ccte->transformCoordinates(_data, &pt);
                if (!ccte_err) {
                    _data.AZ = pt.X;
                    _data.ALT = pt.Y;
                    _data.ZD = std::numbers::pi / 2.0 - _data.ALT;
                }
            } else if constexpr (mccIsAltAzMount(pcm_t::mountType)) {
                _data.AZ = (double)hw_pos.X + pcm_res.dx;
                _data.ALT = (double)hw_pos.Y + pcm_res.dy;
                _data.ZD = std::numbers::pi / 2.0 - _data.ALT;

                _data.X = _data.AZ;
                _data.Y = _data.ALT;

                _data.pair_kind = MccCoordPairKind::COORDS_KIND_AZALT;

                pt.pair_kind = MccCoordPairKind::COORDS_KIND_HADEC_APP;
                ccte_err = ccte->transformCoordinates(_data, &pt);
                if (!ccte) {
                    _data.HA = pt.X;
                    _data.DEC_APP = pt.Y;
                    _data.RA_APP = (double)_data.LST - (double)_data.HA + eo;
                }

            } else {
                static_assert(false, "UNKNOWN MOUNT TYPE!");
            }

            if (!ccte_err) {
                if (stop_token.stop_requested()) {
                    return MccTelemetryErrorCode::ERROR_UPDATE_STOPPED;
                }

                _data.pair_kind = MccCoordPairKind::COORDS_KIND_AZZD;
                _data.X = _data.AZ;
                _data.Y = _data.ZD;

                ccte_err = ccte->refractionCorrection(_data, &_data.refCorr);
                if (!ccte_err) {
                    // restore hardware encoders coordinates
                    _data.X = (double)hw_pos.X;
                    _data.Y = (double)hw_pos.Y;

                    // update target (assuming target ICRS coordinates are already set)

                    auto ret = _updateTargetFunc(false, stop_token);
                    if (ret) {
                        return ret;
                    }
                }
            }

            if (ccte_err) {
                return mcc_deduce_error(ccte_err, MccTelemetryErrorCode::ERROR_COORD_TRANSFORM);
            }

            if constexpr (mccIsEquatorialMount(pcm_t::mountType)) {
                _data.pair_kind = MccCoordPairKind::COORDS_KIND_HADEC_APP;
            } else if constexpr (mccIsAltAzMount(pcm_t::mountType)) {
                _data.pair_kind = MccCoordPairKind::COORDS_KIND_AZALT;
            } else {
                static_assert(false, "UNKNOWN MOUNT TYPE!");
            }


            _updated = true;

            return MccTelemetryErrorCode::ERROR_OK;
        };


        _setTargetFunc = [ccte, this](MccCelestialPoint const& pt) {
            // in the case of apparent input coordinates
            // one must ensure the same time points

            _data.target.pair_kind = MccCoordPairKind::COORDS_KIND_RADEC_ICRS;
            _data.target.time_point =
                std::chrono::time_point_cast<typename decltype(_data.target.time_point)::duration>(pt.time_point);

            auto ret = ccte->transformCoordinates(pt, &_data.target);

            if (!ret) {
                if (pt.pair_kind == MccCoordPairKind::COORDS_KIND_RADEC_ICRS) {
                    _data.target.RA_ICRS = _data.target.X;
                    _data.target.DEC_ICRS = _data.target.Y;

                    // update apparent coordinates
                    ret = _updateTargetFunc(false, {});
                } else {  // apparent coordinates were computed above
                    // compute ICRS coordinates
                    MccCelestialPoint cpt{.pair_kind = MccCoordPairKind::COORDS_KIND_RADEC_ICRS};
                    ret = ccte->transformCoordinates(pt, &cpt);

                    _data.target.RA_ICRS = cpt.X;
                    _data.target.DEC_ICRS = cpt.Y;

                    // compute only hardware coordinates
                    ret = _updateTargetFunc(true, {});
                }
            }

            return mcc_deduce_error<error_t>(ret, MccTelemetryErrorCode::ERROR_COORD_TRANSFORM);
        };
    }


    virtual ~MccTelemetry() = default;

    template <traits::mcc_time_duration_c DT>
    DT telemetryDataUpdateInterval() const
    {
        return std::chrono::duration_cast<DT>(_currentUpdateInterval);
    }

    std::chrono::milliseconds telemetryDataUpdateInterval() const
    {
        return telemetryDataUpdateInterval<std::chrono::milliseconds>();
    }

    error_t updateTelemetryData(traits::mcc_time_duration_c auto const& period)
    {
        // using d_t = typename std::remove_cvref_t<decltype(period)>::rep;

        // bool is_zero;

        // if (std::floating_point<d_t>) {
        //     is_zero = utils::isEqual(period.count(), d_t::zero());
        // } else {
        //     is_zero = period.count() == d_t::zero();
        // }

        // if (is_zero) {  // just update once
        //     return _updateFunc();
        // } else {
        //     // try to update once
        //     auto ret = _updateFunc();
        //     if (ret) {
        //         return ret;
        //     }

        //     _lastUpdateError = MccTelemetryErrorCode::ERROR_OK;

        //     _timerThread = [period, this](std::stop_token st) {
        //         while (!st.stop_requested()) {
        //             {
        //                 std::lock_guard thread_lock{*_updateMutex};

        //                 _lastUpdateError = _updateFunc();
        //                 _updateCondVar->notify_all();
        //                 if (_lastUpdateError) {
        //                     return;
        //                 }
        //             }

        //             std::this_thread::sleep_for(period);
        //         }
        //     };

        //     _timerThread.detach();

        //     return MccTelemetryErrorCode::ERROR_OK;
        // }

        std::lock_guard thread_lock{*_updateMutex};

        std::stop_source stop_source;

        std::future<error_t> update_ft = std::async(std::launch::async, _updateFunc, stop_source.get_token());
        auto status = update_ft.wait_for(period);

        if (status != std::future_status::ready) {
            auto ok = stop_source.stop_requested();
            return MccTelemetryErrorCode::ERROR_DATA_TIMEOUT;
        }

        _updateCondVar->notify_all();

        return update_ft.get();
    }

    // block the thread and wait for data to be ready (external synchronization)
    error_t waitForTelemetryData(mcc_telemetry_data_c auto* tdata, traits::mcc_time_duration_c auto const& timeout)
    {
        if (tdata == nullptr) {
            return MccTelemetryErrorCode::ERROR_NULLPTR;
        }

        std::unique_lock ulock(*_updateMutex);

        auto res = _updateCondVar->wait_for(ulock, timeout, [this]() { return _updated; });
        if (res == std::cv_status::timeout) {
            return MccTelemetryErrorCode::ERROR_DATA_TIMEOUT;
        }

        std::lock_guard thread_lock{*_updateMutex};

        if (!_lastUpdateError) {
            mcc_copy_telemetry_data(_data, tdata);
        }

        return _lastUpdateError;
    }

    // update and get data as soon as possible
    error_t telemetryData(mcc_telemetry_data_c auto* tdata)
    {
        if (tdata == nullptr) {
            return MccTelemetryErrorCode::ERROR_NULLPTR;
        }

        std::lock_guard thread_lock{*_updateMutex};

        // error_t ret = _updateFunc();

        // if (!ret) {
        //     mcc_copy_telemetry_data(_data, tdata);
        // }

        // return ret;

        mcc_copy_telemetry_data(_data, tdata);

        return MccTelemetryErrorCode::ERROR_OK;
    }


    error_t setPointingTarget(mcc_celestial_point_c auto pt)
    {
        std::lock_guard lock{*_updateMutex};

        return _setTargetFunc(pt);
    }


protected:
    std::atomic_bool _updated;
    MccTelemetryData _data;

    std::chrono::nanoseconds _currentUpdateInterval{std::chrono::milliseconds(100)};

    std ::function<error_t(bool, std::stop_token)> _updateTargetFunc{};
    std::function<error_t(std::stop_token)> _updateFunc{};
    std::function<error_t()> _setTargetFunc{};

    std::unique_ptr<std::mutex> _updateMutex;
    std::unique_ptr<std::condition_variable> _updateCondVar;

    error_t _lastUpdateError{MccTelemetryErrorCode::ERROR_OK};
    std::jthread _timerThread;
};

}  // namespace mcc