/*
 * Copyright (C) 2020  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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.
 *
 * Antkeeper source code 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 Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef ANTKEEPER_SOLAR_SYSTEM_HPP
#define ANTKEEPER_SOLAR_SYSTEM_HPP

#include "entity-system.hpp"
#include "utility/fundamental-types.hpp"

/**
 * 
 */
class solar_system:
	public entity_system
{
public:
	solar_system(entt::registry& registry);
	
	/**
	 * Scales then adds the timestep `dt` to the current Julian date, then recalculates the positions of celestial bodies.
	 */
	virtual void update(double t, double dt);
	
	/**
	 * Sets the current Julian date.
	 *
	 * @param jd Julian date.
	 */
	void set_julian_date(double jd);
	
	/**
	 * Sets the factor by which the timestep `dt` will be scaled before being added to the current Julian date.
	 *
	 * @param scale Factor by which to scale the timestep.
	 */
	void set_time_scale(double scale);
	
	/**
	 * Sets the latitude, longitude, and altitude of the observer.
	 *
	 * @param latitude Observer latitude, in radians.
	 * @param longitude Observer longitude, in radians.
	 * @param altitude Observer altitude, in meters.
	 */
	void set_observer_location(double latitude, double longitude, double altitude);
	
private:
	double julian_date;
	double time_scale;
	double latitude;
	double longitude;
	double altitude;
	
	double lmst;
	double ecl;
	double3x3 ecliptic_to_horizontal;
	
	double3 sun_position;
	double3 sunlight_direction;
	
	double3 moon_position;
	double3 moonlight_direction;
};

#endif // ANTKEEPER_SOLAR_SYSTEM_HPP