/**
 * @file kernel/qss/Integrator.hpp
 * @author The ARTIS Development Team
 * See the AUTHORS or Authors.txt file
 */

/*
 * ARTIS - the multimodeling and simulation environment
 * This file is a part of the ARTIS environment
 *
 * Copyright (C) 2013-2022 ULCO http://www.univ-littoral.fr
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef QSS_INTEGRATOR
#define QSS_INTEGRATOR

#include <artis-star/kernel/pdevs/Dynamics.hpp>
#include <artis-star/kernel/qss/Data.hpp>

namespace artis::qss {

struct IntegratorParameters {
  double x_0;
};

template<typename Time>
class Integrator
  : public artis::pdevs::Dynamics<Time, Integrator<Time>, IntegratorParameters> {
public:
  struct input {
    enum values {
      QUANTA, X_DOT, RESET
    };
  };

  struct output {
    enum values {
      OUT
    };
  };

  struct var {
    enum values {
      VALUE
    };
  };

  Integrator(const std::string &name,
             const artis::pdevs::Context<Time, Integrator<Time>, IntegratorParameters> &context)
    :
    artis::pdevs::Dynamics<Time, Integrator<Time>, IntegratorParameters>(name,
                                                                         context) {
    DECLARE_STATES(int, ((state::PHASE, &Integrator<Time>::_phase)));
    DECLARE_STATES(typename Time::type,
                   ((state::LAST_OUT_DATE, &Integrator<Time>::_last_output_date)));
    DECLARE_STATES(double, ((state::UP_THRESHOLD, &Integrator<Time>::_up_threshold),
      (state::DOWN_THRESHOLD, &Integrator<Time>::_down_threshold),
      (state::LAST_OUT_VALUE, &Integrator<Time>::_last_output_value),
      (state::INIT_VALUE, &Integrator<Time>::_init_value),
      (state::CURRENT_VALUE, &Integrator<Time>::_current_value),
      (state::EXPECTED_VALUE, &Integrator<Time>::_expected_value)));
    DECLARE_STATES(std::vector < double > ,
                   ((state::ARCHIVE_X_DOT, &Integrator<Time>::_archive_x_dot)));
    DECLARE_STATES(std::vector < typename Time::type > ,
                   ((state::ARCHIVE_DATE, &Integrator<Time>::_archive_date)));

    this->input_ports({
                        {input::QUANTA, "quanta"},
                        {input::X_DOT,  "x_dot"},
                        {input::RESET,  "reset"}});
    this->output_port({output::OUT, "out"});
    this->observable({var::VALUE, "value"});

    _init_value = context.parameters().x_0;
  }

  virtual ~Integrator() {}

  virtual void dconf(typename Time::type t, typename Time::type e,
                     const common::event::Bag <Time> &bag) {
    dint(t);
    dext(t, e, bag);
  }

  virtual void dint(const typename Time::type &time) {
    switch (_phase) {
      case phase::RUNNING: {
        double last_derivative_value = _archive_x_dot.back();

        _last_output_value = _expected_value;
        _last_output_date = time;
        _archive_x_dot.clear();
        _archive_date.clear();
        _archive_x_dot.push_back(last_derivative_value);
        _archive_date.push_back(time);
        _current_value = _expected_value;
        _phase = phase::WAIT_FOR_QUANTA;
        break;
      }
      case phase::INIT: {
        _phase = phase::WAIT_FOR_BOTH;
        _last_output_value = _current_value;
        _last_output_date = time;
        break;
      }
      default:
        assert(false);
    }
  }

  virtual void dext(const typename Time::type &t, const typename Time::type &e,
                    const common::event::Bag <Time> &bag) {
    bool reset = false;

    std::for_each(bag.begin(), bag.end(),
                  [this, t, e, &reset](const common::event::ExternalEvent <Time> &event) {
                    if (event.on_port(input::QUANTA)) {
                      QuantifierData data;

                      event.data()(data);
                      _up_threshold = data.up;
                      _down_threshold = data.down;
                      if (_phase == phase::WAIT_FOR_QUANTA) {
                        _phase = phase::RUNNING;
                      }
                      if (_phase == phase::WAIT_FOR_BOTH) {
                        _phase = phase::WAIT_FOR_X_DOT;
                      }
                    } else if (event.on_port(input::X_DOT)) {
                      DerivativeData data;

                      event.data()(data);
                      _archive_x_dot.push_back(data.x_dot);
                      _archive_date.push_back(t);
                      if (_phase == phase::WAIT_FOR_X_DOT) {
                        _phase = phase::RUNNING;
                      }
                      if (_phase == phase::WAIT_FOR_BOTH) {
                        _phase = phase::WAIT_FOR_QUANTA;
                      }
                    } else if (event.on_port(input::RESET)) {
                      IntegratorData data;

                      event.data()(data);
                      _current_value = data.value;
                      reset = true;
                      _archive_x_dot.clear();
                      _archive_date.clear();
                    }
                  });
    if (reset) {
      _phase = phase::INIT;
    } else {
      if (_phase == phase::RUNNING) {
        _current_value = current_value(t);
        _expected_value = expected_value(t);
      }
    }
  }

  virtual void start(const typename Time::type & /* time */) {
    _current_value = _init_value;
    _phase = phase::INIT;
  }

  virtual typename Time::type ta(const typename Time::type & /* time */) {
    double current_derivative;

    switch (_phase) {
      case phase::INIT:
        return 0;
      case phase::RUNNING:

        assert(_archive_date.size() > 0);

        current_derivative = _archive_x_dot.back();
        if (current_derivative == 0) {
          return Time::infinity;
        }
        if (current_derivative > 0) {

          assert(_up_threshold - _current_value >= 0);

          return (_up_threshold - _current_value) / current_derivative;
        } else {

          assert(_down_threshold - _current_value <= 0);

          return (_down_threshold - _current_value) / current_derivative;
        }
      default:
        return Time::infinity;
    }
  }

  virtual common::event::Bag <Time> lambda(const typename Time::type & /* time */) const {
    common::event::Bag <Time> msgs;

    switch (_phase) {
      case phase::RUNNING: {
        const IntegratorData data = {_expected_value};

        msgs.push_back(common::event::ExternalEvent<Time>(output::OUT, data));
        break;
      }
      case phase::INIT: {
        const IntegratorData data = {_current_value};

        msgs.push_back(common::event::ExternalEvent<Time>(output::OUT, data));
        break;
      }
      default:
        break;
    }
    return msgs;
  }

  virtual common::event::Value observe(const typename Time::type & /* t */,
                                unsigned int index) const {
    switch (index) {
      case var::VALUE:
        return (double) (_current_value);
      default:
        return common::event::Value();
    }
  }

private:
  double current_value(const typename Time::type &time) const {
    double val = _last_output_value;

    if (_archive_date.size() > 0) {
      for (size_t i = 0; i < _archive_date.size() - 1; i++) {
        val +=
          (_archive_date[i + 1] - _archive_date[i]) * _archive_x_dot[i];
      }
      val += (time - _archive_date.back()) * _archive_x_dot.back();
    }
    return val;
  }

  double expected_value(const typename Time::type & /* time */) const {
    double current_derivative = _archive_x_dot.back();

    if (current_derivative == 0) {
      return _current_value;
    } else if (current_derivative > 0) {
      return _up_threshold;
    }
    return _down_threshold;
  }

  struct phase {
    enum values {
      INIT,
      WAIT_FOR_QUANTA,
      WAIT_FOR_X_DOT,
      WAIT_FOR_BOTH,
      RUNNING
    };
  };

  struct state {
    enum values {
      PHASE,
      LAST_OUT_DATE,
      UP_THRESHOLD,
      DOWN_THRESHOLD,
      LAST_OUT_VALUE,
      INIT_VALUE,
      CURRENT_VALUE,
      EXPECTED_VALUE,
      ARCHIVE_X_DOT,
      ARCHIVE_DATE
    };
  };

  int _phase;

  typename Time::type _last_output_date;

  double _up_threshold;
  double _down_threshold;

  double _last_output_value;
  double _init_value;
  double _current_value;
  double _expected_value;

  std::vector<double> _archive_x_dot;
  std::vector<typename Time::type> _archive_date;
};

}

#endif