/**
 * @file kernel/qss/Derivative.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_DERIVATIVE
#define QSS_DERIVATIVE

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

namespace artis::qss {

template<typename Time, typename Dyn, typename Parameters = common::NoParameters>
class Derivative : public artis::pdevs::Dynamics<Time, Dyn, Parameters> {
public:
  struct input {
    enum values {
      RESET = 0, IN
    };
  };

  struct output {
    enum values {
      OUT = 0
    };
  };

  struct var {
    enum values {
      VALUE
    };
  };

  typedef Derivative<Time, Dyn, Parameters> type;

  Derivative(const std::string &name, const artis::pdevs::Context<Time, Dyn, Parameters> &context)
    :
    artis::pdevs::Dynamics<Time, Dyn, Parameters>(name, context),
    _external_number(0), _internal_number(0) {
    DECLARE_STATES(int,
                   ((state::PHASE, &type::_phase)));
    DECLARE_STATES(unsigned int,
                   ((state::INPUT_NUMBER, &type::_input_number)));
    DECLARE_STATES(double,
                   ((state::OUTPUT_VALUE, &type::_output_value),
                     (state::LAST_OUTPUT, &type::_last_output)));

    this->input_ports({{input::RESET, "reset"},
                       {input::IN,    "in"}});
    this->output_port({output::OUT, "out"});
    this->observable({var::VALUE, "value"});
  }

  virtual ~Derivative() {}

  int external(const std::string &name, double Dyn::* var) {
    ++_external_number;
    this->state_(state::LAST_OUTPUT + _external_number + 1, name, var);
    this->input_port({input::IN + _external_number, name});
    return input::IN + _external_number;
  }

  void internal(const std::string &name, double Dyn::* var) {
    assert(_internal_number == 0);

    ++_internal_number;
    this->state_(state::LAST_OUTPUT + 1, name, var);
  }

  virtual double compute() const = 0;

  virtual void dconf(const 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 */) {
    if (_phase == phase::RESPONSE) {
      _last_output = _output_value;
    }
    _phase = phase::WAIT;
  }

  virtual void dext(const typename Time::type &t, typename Time::type e,
                    const common::event::Bag<Time> &bag) {
    std::for_each(bag.begin(), bag.end(),
                  [this, t, e](const common::event::ExternalEvent<Time> &event) {
                    if (event.on_port(input::RESET)) {
                      _input_number = 0;
                      _phase = phase::INIT;
                    } else {
                      IntegratorData data;

                      event.data()(data);
                      this->get((event.port_index() - 1) + state::LAST_OUTPUT + 1).put(
                        dynamic_cast<Dyn *>(this), data.value);
                      switch (_phase) {
                        case phase::INIT: {
                          ++_input_number;
                          if (_input_number == this->state_number() - (state::LAST_OUTPUT + 1)) {
                            _output_value = compute();
                            _phase = phase::RESPONSE;
                          }
                          break;
                        }
                        case phase::WAIT:
                        case phase::RESPONSE: {
                          double value = compute();

                          if (value != _last_output) {
                            _output_value = value;
                            _phase = phase::RESPONSE;
                          } else {
                            _phase = phase::WAIT;
                          }
                        }
                      }
                    }
                  });
  }

  virtual void start(const typename Time::type & /* time */) {
    _input_number = 0;
    _phase = phase::INIT;
  }

  virtual typename Time::type ta(const typename Time::type & /* time */) {
    switch (_phase) {
      case phase::INIT:
        return Time::infinity;
      case phase::WAIT:
        return Time::infinity;
      case phase::RESPONSE:
        return 0;
    }
    return Time::infinity;
  }

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

    switch (_phase) {
      case phase::INIT:
        break;
      case phase::WAIT:
        break;
      case phase::RESPONSE: {
        const DerivativeData data = {_output_value};

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

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

private:
  struct phase {
    enum values {
      INIT = 0, WAIT, RESPONSE
    };
  };

  struct state {
    enum values {
      PHASE = 0, INPUT_NUMBER, OUTPUT_VALUE, LAST_OUTPUT
    };
  };

  unsigned int _external_number;
  unsigned int _internal_number;

  // state
  int _phase;
  unsigned int _input_number;
  double _output_value;
  double _last_output;
};

}

#endif