/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
/*
    Gpredict: Real-time satellite tracking and orbit prediction program

    Copyright (C)  2001-2007  Alexandru Csete, OZ9AEC.

    Authors: Alexandru Csete <csete@users.sourceforge.net>

    Comments, questions and bugreports should be submitted via
    http://sourceforge.net/projects/groundstation/
    More details can be found at the project home page:

            http://groundstation.sourceforge.net/
 
    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 2 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, visit http://www.fsf.org/
*/
/** \brief Satellite visibility calculations. */
#include <gtk/gtk.h>
#include <glib/gi18n.h>
#include "sgpsdp/sgp4sdp4.h"
#include "gtk-sat-data.h"
#include "sat-vis.h"


static gchar VIS2CHR[SAT_VIS_NUM] = { '-', 'V', 'D', 'E'};

static gchar *VIS2STR[SAT_VIS_NUM] = {
	N_("Unknown"),
	N_("Visible"),
	N_("Daylight"),
	N_("Eclipsed")
};



/** \brief Calculate satellite visibility.
 *  \param sat The satellite structure.
 *  \param qth The QTH
 *  \param jul_utc The time at which the visibility should be calculated.
 *  \return The visiblity code.
 *
 */
sat_vis_t
get_sat_vis (sat_t *sat, qth_t *qth, gdouble jul_utc)
{
	gboolean sat_sun_status;
	gdouble  sun_el;
	gdouble  eclipse_depth;
	sat_vis_t vis = SAT_VIS_NONE;
	vector_t zero_vector = {0,0,0,0};
	geodetic_t obs_geodetic;

	/* Solar ECI position vector  */
	vector_t solar_vector=zero_vector;

	/* Solar observed az and el vector  */
	obs_set_t solar_set;

	/* FIXME: could be passed as parameter */
	obs_geodetic.lon = qth->lon * de2ra;
	obs_geodetic.lat = qth->lat * de2ra;
	obs_geodetic.alt = qth->alt / 1000.0;
	obs_geodetic.theta = 0;


	Calculate_Solar_Position (jul_utc, &solar_vector);
	Calculate_Obs (jul_utc, &solar_vector, &zero_vector, &obs_geodetic, &solar_set);

	if (Sat_Eclipsed (&sat->pos, &solar_vector, &eclipse_depth)) {
		/* satellite is eclipsed */
		sat_sun_status = FALSE;
	}
	else {
		/* satellite in sunlight => may be visible */
		sat_sun_status = TRUE;
	}

	sun_el = Degrees (solar_set.el);

	if (sat_sun_status) {
		if (sun_el <= -12.0 && sat->el >= 0.0)
			vis = SAT_VIS_VISIBLE;
		else
			vis = SAT_VIS_DAYLIGHT;
	}
	else
		vis = SAT_VIS_ECLIPSED;


	return vis;
}



/** \brief Convert visibility to character code. */
gchar
vis_to_chr       (sat_vis_t vis)
{
	return VIS2CHR[vis];
}


/** \brief Convert visibility to character string.
 *  \param vis The visibility code
 *
 * The returned string must be freed when no longer needed.
 */
gchar *
vis_to_str       (sat_vis_t vis)
{
	return g_strdup (VIS2STR[vis]);
}