/*
 * \file galileo_utc_model.h
 * \brief  Interface of a Galileo UTC MODEL storage
 * \author Javier Arribas, 2013. jarribas(at)cttc.es
 *
 * -------------------------------------------------------------------------
 *
 * Copyright (C) 2010-2013  (see AUTHORS file for a list of contributors)
 *
 * GNSS-SDR is a software defined Global Navigation
 *          Satellite Systems receiver
 *
 * This file is part of GNSS-SDR.
 *
 * GNSS-SDR 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.
 *
 * GNSS-SDR 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 GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
 *
 * -------------------------------------------------------------------------
 */

#include "galileo_utc_model.h"

Galileo_Utc_Model::Galileo_Utc_Model()
{
    //valid = false;
    /*Word type 6: GST-UTC conversion parameters*/
    A0_6 = 0;
    A1_6 = 0;
    Delta_tLS_6 = 0;
    t0t_6 = 0;
    WNot_6 = 0;
    WN_LSF_6 = 0;
    DN_6 = 0;
    Delta_tLSF_6 = 0;
    flag_utc_model = false;
}

double Galileo_Utc_Model::GST_to_UTC_time(double t_e, int WN)
{
    double t_Utc;
    double t_Utc_daytime;
    double Delta_t_Utc=0;
    // Determine if the effectivity time of the leap second event is in the past
    int  weeksToLeapSecondEvent = WN_LSF_6 - (WN % 256);

    if ((weeksToLeapSecondEvent) >= 0) // is not in the past
    {
    	//Detect if the effectivity time and user's time is within six hours  = 6 * 60 *60 = 21600 s
    	int secondOfLeapSecondEvent = DN_6 * 24 * 60 * 60;
    	if  (abs(t_e - secondOfLeapSecondEvent) > 21600)
    	{
    		/* 5.1.7a
    		 * Whenever the leap second adjusted time indicated by the WN_LSF and the DN values
    		 * is not in the past (relative to the user's present time), and the user's
    		 * present time does not fall in the time span which starts at six hours prior
    		 * to the effective time and ends at six hours after the effective time,
    		 * the GST/Utc relationship is given by
    		 */
    		//std::cout<<"GST->UTC case a"<<std::endl;
    		Delta_t_Utc =  Delta_tLS_6 + A0_6 + A1_6 * (t_e - t0t_6 + 604800 * (double)((WN % 256) - WNot_6));
    		t_Utc_daytime = fmod(t_e - Delta_t_Utc, 86400);
    	}
    	else
    	{
    		/* 5.1.7b
    		 * Whenever the user's current time falls within the time span of six hours
    		 * prior to the leap second adjustment to six hours after the adjustment time, ,
    		 * the effective time is computed according to the following equations:
    		 */
    		//std::cout<<"GST->UTC case b"<<std::endl;
    		Delta_t_Utc =  Delta_tLS_6 + A0_6 + A1_6 * (t_e - t0t_6 + 604800 * (double)((WN % 256) - WNot_6));
    		double W = fmod(t_e - Delta_t_Utc - 43200, 86400) + 43200;
    		t_Utc_daytime = fmod(W, 86400 + Delta_tLSF_6 - Delta_tLS_6);
    		//implement something to handle a leap second event!
    	}
    }
    else // the effectivity time is in the past
    {
    	/* 5.1.7c
    	 * Whenever the leap second adjustment time, as indicated by the WN_LSF and DN values,
    	 * is in the past (relative to the user’s current time) and the user’s present time does not
    	 * fall in the time span which starts six hours prior to the leap second adjustment time and
    	 * ends six hours after the adjustment time, the effective time is computed according to
    	 * the following equation:
    	 */
    	//std::cout<<"GST->UTC case c"<<std::endl;
    	Delta_t_Utc = Delta_tLSF_6 + A0_6 + A1_6 * (t_e - t0t_6 + 604800 * (double)((WN % 256) - WNot_6));
    	t_Utc_daytime = fmod(t_e - Delta_t_Utc, 86400);
    }

    double secondsOfWeekBeforeToday = 43200 * floor(t_e / 43200);
    t_Utc = secondsOfWeekBeforeToday + t_Utc_daytime;
    return t_Utc;
}