/**
 * @file SBAS solver
 *
 */

/*
 * Copyright (c) 2020, M.Naruoka (fenrir)
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 * - Neither the name of the naruoka.org nor the names of its contributors
 *   may be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef __SBAS_SOLVER_H__
#define __SBAS_SOLVER_H__

#include "SBAS.h"
#include "GPS_Solver_Base.h"
#include "GPS_Solver.h"

#include <cstddef>

template <class FloatT>
struct SBAS_SinglePositioning_Options : public GPS_Solver_GeneralOptions<FloatT> {
  typedef GPS_Solver_GeneralOptions<FloatT> super_t;

  typename GPS_Solver_Base<FloatT>::options_t::template exclude_prn_t<120, 158> exclude_prn; // SBAS PRN ranges from 120 to 158
  SBAS_SinglePositioning_Options()
      : super_t(), exclude_prn() {
    exclude_prn.set(true); // SBAS ranging is default off.
  }
};

template <class FloatT, class SolverBaseT = GPS_Solver_Base<FloatT> >
class SBAS_SinglePositioning : public SolverBaseT {
  private:
    SBAS_SinglePositioning<FloatT> &operator=(const SBAS_SinglePositioning<FloatT> &);
  public:
    typedef SBAS_SinglePositioning<FloatT> self_t;
    typedef SolverBaseT base_t;

#if defined(__GNUC__) && (__GNUC__ < 5)
#define inheritate_type(x) typedef typename base_t::x x;
#else
#define inheritate_type(x) using typename base_t::x;
#endif

    inheritate_type(float_t);
    inheritate_type(prn_t);

    typedef SBAS_SpaceNode<float_t> space_node_t;
    inheritate_type(gps_time_t);

    inheritate_type(xyz_t);
    inheritate_type(enu_t);

    inheritate_type(pos_t);

    typedef typename base_t::measurement_t measurement_t;
    typedef typename base_t::satellite_t satellite_t;
    typedef typename base_t::range_error_t range_error_t;
    typedef typename base_t::range_corrector_t range_corrector_t;
    typedef typename base_t::range_correction_t range_correction_t;

    inheritate_type(relative_property_t);
#undef inheritate_type

    typedef typename GPS_Solver_Base<float_t>::options_t::template merge_t<
        SBAS_SinglePositioning_Options<float_t>, base_t> options_t;

  protected:
    SBAS_SinglePositioning_Options<float_t> _options;

  public:
    struct satellites_t {
      const void *impl;
      satellite_t (*impl_select)(const void *, const prn_t &, const gps_time_t &);
      inline satellite_t select(const prn_t &prn, const gps_time_t &receiver_time) const {
        return impl_select(impl, prn, receiver_time);
      }
      static satellite_t select_broadcast(
          const void *ptr, const prn_t &prn, const gps_time_t &receiver_time){
        const typename space_node_t::satellites_t &sats(
            reinterpret_cast<const space_node_t *>(ptr)->satellites());
        const typename space_node_t::satellites_t::const_iterator it_sat(sats.find(prn));
        if((it_sat == sats.end()) // has ephemeris?
            || (!it_sat->second.ephemeris().is_valid(receiver_time))){ // valid ephemeris?
          return satellite_t::unavailable();
        }
        struct impl_t {
          static inline const typename space_node_t::Satellite &sat(const void *ptr) {
            return *reinterpret_cast<const typename space_node_t::Satellite *>(ptr);
          }
          static xyz_t position(const void *ptr, const gps_time_t &t, const float_t &pseudo_range) {
            return sat(ptr).ephemeris().constellation(t, pseudo_range, false).position;
          }
          static xyz_t velocity(const void *ptr, const gps_time_t &t, const float_t &pseudo_range) {
            return sat(ptr).ephemeris().constellation(t, pseudo_range, true).velocity;
          }
          static float_t clock_error(const void *ptr, const gps_time_t &t, const float_t &pseudo_range) {
            // Clock correction is taken into account in position()
            return 0;
          }
          static float_t clock_error_dot(const void *ptr, const gps_time_t &t, const float_t &pseudo_range) {
            // Clock rate error is taken in account in velocity()
            return 0;
          }
        };
        satellite_t res = {
            &(it_sat->second),
            impl_t::position, impl_t::velocity,
            impl_t::clock_error, impl_t::clock_error_dot};
        return res;
      }
      satellites_t(const space_node_t &sn)
          : impl(&sn), impl_select(select_broadcast) {}
    } satellites;

    struct ionospheric_sbas_t : public range_corrector_t {
      const space_node_t &space_node;
      ionospheric_sbas_t(const space_node_t &sn) : range_corrector_t(), space_node(sn) {}
      bool is_available(const gps_time_t &t) const {
        return true;
      }
      float_t *calculate(
          const gps_time_t &t, const pos_t &usr_pos, const enu_t &sat_rel_pos,
          float_t &buf) const {

        // placeholder of checking availability and performing correction
        typedef typename space_node_t::available_satellites_t sats_t;
        sats_t sats(space_node.available_satellites(usr_pos.llh.longitude()));

        typename space_node_t::IonosphericGridPoints::PointProperty prop;
        for(typename sats_t::const_iterator it(sats.begin()); it != sats.end(); ++it){
          prop = it->second
              ->ionospheric_grid_points().iono_correction(sat_rel_pos, usr_pos.llh);
          if(prop.is_available()){
            return &(buf = prop.delay);
          }
          break; // TODO The nearest satellite is only checked
        }
        return NULL;
      }
    } ionospheric_sbas;

    struct tropospheric_sbas_t : public range_corrector_t {
      tropospheric_sbas_t() : range_corrector_t() {}
      bool is_available(const gps_time_t &t) const {
        return true;
      }
      float_t *calculate(
          const gps_time_t &t, const pos_t &usr_pos, const enu_t &sat_rel_pos,
          float_t &buf) const {
        return &(buf = space_node_t::tropo_correction(
            t.year(), sat_rel_pos, usr_pos.llh));
      }
    } tropospheric_sbas;

    range_correction_t ionospheric_correction, tropospheric_correction;

    options_t available_options() const {
      return options_t(base_t::available_options(), _options);
    }

    options_t available_options(const options_t &opt_wish) const {
      SBAS_SinglePositioning_Options<float_t> opt(opt_wish);
      return options_t(base_t::available_options(opt_wish), opt);
    }

    options_t update_options(const options_t &opt_wish){
      _options = opt_wish;
      return options_t(base_t::update_options(opt_wish), _options);
    }

    SBAS_SinglePositioning(const space_node_t &sn)
        : base_t(), _options(available_options(options_t())),
        satellites(sn),
        ionospheric_sbas(sn), tropospheric_sbas() {

      // default ionospheric correction: Broadcasted IGP.
      ionospheric_correction.push_front(&ionospheric_sbas);

      // default troposheric correction: SBAS
      tropospheric_correction.push_front(&tropospheric_sbas);
    }

    ~SBAS_SinglePositioning(){}

    /**
     * Select satellite by using PRN and time
     *
     * @param prn satellite number
     * @param receiver_time receiver time
     * @return (satellite_t) If available, satellite.is_available() returning true is returned.
     */
    satellite_t select_satellite(
        const prn_t &prn,
        const gps_time_t &receiver_time) const {
      if(_options.exclude_prn[prn]){return satellite_t::unavailable();}
      return satellites.select(prn, receiver_time);
    }

    /**
     * Calculate relative range and rate information to a satellite
     *
     * @param prn satellite number
     * @param measurement measurement (per satellite) containing pseudo range
     * @param receiver_error (temporal solution of) receiver clock error in meter
     * @param time_arrival time when signal arrive at receiver
     * @param usr_pos (temporal solution of) user position
     * @param usr_vel (temporal solution of) user velocity
     * @return (relative_property_t) relative information
     */
    relative_property_t relative_property(
        const prn_t &prn,
        const typename measurement_t::mapped_type &measurement,
        const float_t &receiver_error,
        const gps_time_t &time_arrival,
        const pos_t &usr_pos,
        const xyz_t &usr_vel) const {

      relative_property_t res = {0};

      float_t range;
      range_error_t range_error;
      if(!this->range(measurement, range, &range_error)){
        return res; // If no range entry, return with weight = 0
      }

      satellite_t sat(select_satellite(prn, time_arrival));
      if(!sat.is_available()){return res;} // If satellite is unavailable, return with weight = 0

      ///< The following procedure is based on Appendix.S with modification

      range -= receiver_error;

      // Clock error correction
      range += ((range_error.unknown_flag & range_error_t::SATELLITE_CLOCK)
          ? (sat.clock_error(time_arrival, range) * GPS_SpaceNode<float_t>::light_speed)
          : range_error.value[range_error_t::SATELLITE_CLOCK]);

      // TODO WAAS long term clock correction (2.1.1.4.11)

      // Calculate satellite position
      xyz_t sat_pos(sat.position(time_arrival, range));
      float_t geometric_range(usr_pos.xyz.dist(sat_pos));

      // Calculate residual with Sagnac correction (A.4.4.11)
      res.range_residual = range
          + space_node_t::sagnac_correction(sat_pos, usr_pos.xyz)
          - geometric_range;

      // Setup design matrix
      res.los_neg[0] = -(sat_pos.x() - usr_pos.xyz.x()) / geometric_range;
      res.los_neg[1] = -(sat_pos.y() - usr_pos.xyz.y()) / geometric_range;
      res.los_neg[2] = -(sat_pos.z() - usr_pos.xyz.z()) / geometric_range;

      enu_t relative_pos(enu_t::relative(sat_pos, usr_pos.xyz));

      // Tropospheric (2.1.4.10.3, A.4.2.4)
      res.range_residual += (range_error.unknown_flag & range_error_t::MASK_TROPOSPHERIC)
          ? tropospheric_correction(time_arrival, usr_pos, relative_pos)
          : range_error.value[range_error_t::TROPOSPHERIC];

      // Ionospheric (2.1.4.10.2, A.4.4.10.4)
      if(range_error.unknown_flag & range_error_t::MASK_IONOSPHERIC){
        res.range_residual += ionospheric_correction(time_arrival, usr_pos, relative_pos);
      }else{
        res.range_residual += range_error.value[range_error_t::IONOSPHERIC];
      }

      // TODO Fast corrections (2.1.1.4.12)

      // TODO Setup weight
      if(std::abs(res.range_residual) > _options.residual_mask){
        // If residual is too big, gently exclude it by decreasing its weight.
        res.weight = 1E-8;
      }else{

        float_t elv(relative_pos.elevation());
        if(elv < _options.elevation_mask){
          res.weight = 0; // exclude it when elevation is less than threshold
        }else{
          // elevation weight based on "GPS実用プログラミング" @see GPS_Solver.h
          res.weight = std::pow(sin(elv)/0.8, 2);
          if(res.weight < 1E-3){res.weight = 1E-3;}
        }
      }

      res.range_corrected = range;

      xyz_t rel_vel(sat.velocity(time_arrival, range) - usr_vel); // Calculate velocity

      res.rate_relative_neg = res.los_neg[0] * rel_vel.x()
          + res.los_neg[1] * rel_vel.y()
          + res.los_neg[2] * rel_vel.z()
          + sat.clock_error_dot(time_arrival, range) * GPS_SpaceNode<float_t>::light_speed;

      return res;
    }
};

#endif /* __SBAS_SOLVER_H__ */