// Part of BNC, a utility for retrieving decoding and
// converting GNSS data streams from NTRIP broadcasters.
//
// Copyright (C) 2007
// German Federal Agency for Cartography and Geodesy (BKG)
// http://www.bkg.bund.de
// Czech Technical University Prague, Department of Geodesy
// http://www.fsv.cvut.cz
//
// Email: euref-ip@bkg.bund.de
//
// 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, version 2.
//
// 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, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

/* -------------------------------------------------------------------------
 * BKG NTRIP Client
 * -------------------------------------------------------------------------
 *
 * Class:      bncutils
 *
 * Purpose:    Auxiliary Functions
 *
 * Author:     L. Mervart
 *
 * Created:    30-Aug-2006
 *
 * Changes:
 *
 * -----------------------------------------------------------------------*/

#include <iostream>
#include <ctime>
#include <math.h>

#include <QRegExp>
#include <QStringList>
#include <QDateTime>

#include <newmatap.h>

#include "bncutils.h"
#include "bnccore.h"

using namespace std;

struct leapseconds { /* specify the day of leap second */
  int day;        /* this is the day, where 23:59:59 exists 2 times */
  int month;      /* not the next day! */
  int year;
  int taicount;
};
static const int months[13] = {0,31,28,31,30,31,30,31,31,30,31,30,31};
static const struct leapseconds leap[] = {
/*{31, 12, 1971, 10},*/
/*{30, 06, 1972, 11},*/
/*{31, 12, 1972, 12},*/
/*{31, 12, 1973, 13},*/
/*{31, 12, 1974, 14},*/
/*{31, 12, 1975, 15},*/
/*{31, 12, 1976, 16},*/
/*{31, 12, 1977, 17},*/
/*{31, 12, 1978, 18},*/
/*{31, 12, 1979, 19},*/
{30, 06, 1981,20},
{30, 06, 1982,21},
{30, 06, 1983,22},
{30, 06, 1985,23},
{31, 12, 1987,24},
{31, 12, 1989,25},
{31, 12, 1990,26},
{30, 06, 1992,27},
{30, 06, 1993,28},
{30, 06, 1994,29},
{31, 12, 1995,30},
{30, 06, 1997,31},
{31, 12, 1998,32},
{31, 12, 2005,33},
{31, 12, 2008,34},
{30, 06, 2012,35},
{30, 06, 2015,36},
{31, 12, 2016,37},
{0,0,0,0} /* end marker */
};

#define GPSLEAPSTART    19 /* 19 leap seconds existed at 6.1.1980 */

static int longyear(int year, int month) {
  if(!(year % 4) && (!(year % 400) || (year % 100)))
  {
    if(!month || month == 2)
      return 1;
  }
  return 0;
}

int gnumleap(int year, int month, int day) {
  int ls = 0;
  const struct leapseconds *l;

  for(l = leap; l->taicount && year >= l->year; ++l)
  {
    if(year > l->year || month > l->month || (month == l->month && day > l->day))
       ls = l->taicount - GPSLEAPSTART;
  }
  return ls;
}

/* Convert Moscow time into UTC (fixnumleap == 1) or GPS (fixnumleap == 0) */
void updatetime(int *week, int *secOfWeek, int mSecOfWeek, bool fixnumleap) {
  int y,m,d,k,l, nul;
  unsigned int j = *week*(7*24*60*60) + *secOfWeek + 5*24*60*60+3*60*60;
  int glo_daynumber = 0, glo_timeofday;
  for(y = 1980; j >= (unsigned int)(k = (l = (365+longyear(y,0)))*24*60*60)
  + gnumleap(y+1,1,1); ++y)
  {
    j -= k; glo_daynumber += l;
  }
  for(m = 1; j >= (unsigned int)(k = (l = months[m]+longyear(y, m))*24*60*60)
  + gnumleap(y, m+1, 1); ++m)
  {
    j -= k; glo_daynumber += l;
  }
  for(d = 1; j >= 24UL*60UL*60UL + gnumleap(y, m, d+1); ++d)
    j -= 24*60*60;
  glo_daynumber -= 16*365+4-d;
  nul = gnumleap(y, m, d);
  glo_timeofday = j-nul;

  // original version
  // if(mSecOfWeek < 5*60*1000 && glo_timeofday > 23*60*60)
  //   *secOfWeek += 24*60*60;
  // else if(glo_timeofday < 5*60 && mSecOfWeek > 23*60*60*1000)
  //   *secOfWeek -= 24*60*60;

  // new version
  if(mSecOfWeek < 4*60*60*1000 && glo_timeofday > 20*60*60)
    *secOfWeek += 24*60*60;
  else if(glo_timeofday < 4*60*60 && mSecOfWeek > 20*60*60*1000)
    *secOfWeek -= 24*60*60;

  *secOfWeek += mSecOfWeek/1000-glo_timeofday;
  if(fixnumleap)
    *secOfWeek -= nul;
  if(*secOfWeek < 0) {*secOfWeek += 24*60*60*7; --*week; }
  if(*secOfWeek >= 24*60*60*7) {*secOfWeek -= 24*60*60*7; ++*week; }
}

//
////////////////////////////////////////////////////////////////////////////
void expandEnvVar(QString& str) {

  QRegExp rx("(\\$\\{.+\\})");

  if (rx.indexIn(str) != -1) {
    QStringListIterator it(rx.capturedTexts());
    if (it.hasNext()) {
      QString rxStr  = it.next();
      QString envVar = rxStr.mid(2,rxStr.length()-3);
      str.replace(rxStr, qgetenv(envVar.toLatin1()));
    }
  }
}

// Strip White Space
////////////////////////////////////////////////////////////////////////////
void stripWhiteSpace(string& str) {
  if (!str.empty()) {
    string::size_type beg = str.find_first_not_of(" \t\f\n\r\v");
    string::size_type end = str.find_last_not_of(" \t\f\n\r\v");
    if (beg > str.max_size())
      str.erase();
    else
      str = str.substr(beg, end-beg+1);
  }
}

//
////////////////////////////////////////////////////////////////////////////
QDateTime dateAndTimeFromGPSweek(int GPSWeek, double GPSWeeks) {

  static const QDate zeroEpoch(1980, 1, 6);

  QDate date(zeroEpoch);
  QTime time(0,0,0,0);

  int weekDays = int(GPSWeeks) / 86400;
  date = date.addDays( GPSWeek * 7 + weekDays );
  time = time.addMSecs( int( (GPSWeeks - 86400 * weekDays) * 1e3 ) );

  return QDateTime(date,time);
}

//
////////////////////////////////////////////////////////////////////////////
void currentGPSWeeks(int& week, double& sec) {

  QDateTime currDateTimeGPS;

  if ( BNC_CORE->dateAndTimeGPSSet() ) {
    currDateTimeGPS = BNC_CORE->dateAndTimeGPS();
  }
  else {
    currDateTimeGPS = QDateTime::currentDateTime().toUTC();
    QDate hlp       = currDateTimeGPS.date();
    currDateTimeGPS = currDateTimeGPS.addSecs(gnumleap(hlp.year(),
                                                     hlp.month(), hlp.day()));
  }

  QDate currDateGPS = currDateTimeGPS.date();
  QTime currTimeGPS = currDateTimeGPS.time();

  week = int( (double(currDateGPS.toJulianDay()) - 2444244.5) / 7 );

  sec = (currDateGPS.dayOfWeek() % 7) * 24.0 * 3600.0 +
        currTimeGPS.hour()                   * 3600.0 +
        currTimeGPS.minute()                 *   60.0 +
        currTimeGPS.second()                          +
        currTimeGPS.msec()                   / 1000.0;
}

//
////////////////////////////////////////////////////////////////////////////
QDateTime currentDateAndTimeGPS() {
  if ( BNC_CORE->dateAndTimeGPSSet() ) {
    return BNC_CORE->dateAndTimeGPS();
  }
  else {
    int    GPSWeek;
    double GPSWeeks;
    currentGPSWeeks(GPSWeek, GPSWeeks);
    return dateAndTimeFromGPSweek(GPSWeek, GPSWeeks);
  }
}

//
////////////////////////////////////////////////////////////////////////////
bool checkForWrongObsEpoch(bncTime obsEpoch) {
  const double maxDt = 600.0;
  bncTime obsTime = obsEpoch;
  int    week;
  double sec;
  currentGPSWeeks(week, sec);
  bncTime currTime(week, sec);

  if (fabs(currTime - obsTime) > maxDt) {
    return true;
  }
  return false;
}

//
////////////////////////////////////////////////////////////////////////////
bool outDatedBcep(const t_eph *eph, bncTime tt) {
  bncTime   toc = eph->TOC();
  double dt = tt -toc;

  // update interval: 2h, data sets are valid for 4 hours
  if      (eph->system() == t_eph::GPS     && (dt > 14400.0 || dt < -7200.0)) {
    return true;
  }
  // update interval: 3h, data sets are valid for 4 hours
  else if (eph->system() == t_eph::Galileo && (dt > 14400.0 || dt <     0.0)) {
    return true;
  }
  // updated every 30 minutes + 5 min
  else if (eph->system() == t_eph::GLONASS && (dt >  2100.0 || dt < -2100.0)) {
    return true;
  }
  // orbit parameters are valid for 7200 seconds (minimum)
  else if (eph->system() == t_eph::QZSS    && (dt >  7200.0 || dt < -3600.0)) {
    return true;
  }
  // maximum update interval: 300 sec
  else if (eph->system() == t_eph::SBAS    && (dt >   600.0 || dt <  -600.0)) {
    return true;
  }
  // updates 1h + 5 min
  else if (eph->system() == t_eph::BDS     && (dt >  3900.0 || dt <     0.0) ) {
    return true;
  }
  // update interval: up to 24 hours
  else if (eph->system() == t_eph::NavIC   && (fabs(dt > 86400.0))) {
    return true;
  }

  return false;
}

//
////////////////////////////////////////////////////////////////////////////
QByteArray ggaString(const QByteArray& latitude,
                     const QByteArray& longitude,
                     const QByteArray& height,
                     const QString& ggaType) {

  double lat = strtod(latitude,NULL);
  double lon = strtod(longitude,NULL);
  double hei = strtod(height,NULL);
  QString sentences = "GPGGA,";
  if (ggaType.contains("GNGGA")) {
    sentences = "GNGGA,";
  }

  const char* flagN="N";
  const char* flagE="E";
  if (lon >180.) {lon=(lon-360.)*(-1.); flagE="W";}
  if ((lon < 0.) && (lon >= -180.))  {lon=lon*(-1.); flagE="W";}
  if (lon < -180.)  {lon=(lon+360.); flagE="E";}
  if (lat < 0.)  {lat=lat*(-1.); flagN="S";}
  QTime ttime(QDateTime::currentDateTime().toUTC().time());
  int lat_deg = (int)lat;
  double lat_min=(lat-lat_deg)*60.;
  int lon_deg = (int)lon;
  double lon_min=(lon-lon_deg)*60.;
  int hh = 0 , mm = 0;
  double ss = 0.0;
  hh=ttime.hour();
  mm=ttime.minute();
  ss=(double)ttime.second()+0.001*ttime.msec();
  QString gga;
  gga += sentences;
  gga += QString("%1%2%3,").arg((int)hh, 2, 10, QLatin1Char('0')).arg((int)mm, 2, 10, QLatin1Char('0')).arg((int)ss, 2, 10, QLatin1Char('0'));
  gga += QString("%1%2,").arg((int)lat_deg,2, 10, QLatin1Char('0')).arg(lat_min, 7, 'f', 4, QLatin1Char('0'));
  gga += flagN;
  gga += QString(",%1%2,").arg((int)lon_deg,3, 10, QLatin1Char('0')).arg(lon_min, 7, 'f', 4, QLatin1Char('0'));
  gga += flagE + QString(",1,05,1.00");
  gga += QString(",%1,").arg(hei, 2, 'f', 1);
  gga += QString("M,10.000,M,,");

  unsigned char XOR = 0;
  for (int ii = 0; ii < gga.length(); ii++) {
    XOR ^= (unsigned char) gga[ii].toLatin1();
  }
  gga = "$" + gga + QString("*%1").arg(XOR, 2, 16, QLatin1Char('0')) + "\r\n";

  return gga.toLatin1();
}

//
////////////////////////////////////////////////////////////////////////////
void RSW_to_XYZ(const ColumnVector& rr, const ColumnVector& vv,
                const ColumnVector& rsw, ColumnVector& xyz) {

  ColumnVector along  = vv / vv.NormFrobenius();
  ColumnVector cross  = crossproduct(rr, vv); cross /= cross.NormFrobenius();
  ColumnVector radial = crossproduct(along, cross);

  Matrix RR(3,3);
  RR.Column(1) = radial;
  RR.Column(2) = along;
  RR.Column(3) = cross;

  xyz = RR * rsw;
}

// Transformation xyz --> radial, along track, out-of-plane
////////////////////////////////////////////////////////////////////////////
void XYZ_to_RSW(const ColumnVector& rr, const ColumnVector& vv,
                const ColumnVector& xyz, ColumnVector& rsw) {

  ColumnVector along  = vv / vv.NormFrobenius();
  ColumnVector cross  = crossproduct(rr, vv); cross /= cross.NormFrobenius();
  ColumnVector radial = crossproduct(along, cross);

  rsw.ReSize(3);
  rsw(1) = DotProduct(xyz, radial);
  rsw(2) = DotProduct(xyz, along);
  rsw(3) = DotProduct(xyz, cross);
}

// Rectangular Coordinates -> Ellipsoidal Coordinates
////////////////////////////////////////////////////////////////////////////
t_irc xyz2ell(const double* XYZ, double* Ell) {

  const double bell = t_CST::aell*(1.0-1.0/t_CST::fInv) ;
  const double e2   = (t_CST::aell*t_CST::aell-bell*bell)/(t_CST::aell*t_CST::aell) ;
  const double e2c  = (t_CST::aell*t_CST::aell-bell*bell)/(bell*bell) ;

  double nn, ss, zps, hOld, phiOld, theta, sin3, cos3;

  ss    = sqrt(XYZ[0]*XYZ[0]+XYZ[1]*XYZ[1]) ;
  zps   = XYZ[2]/ss ;
  theta = atan( (XYZ[2]*t_CST::aell) / (ss*bell) );
  sin3  = sin(theta) * sin(theta) * sin(theta);
  cos3  = cos(theta) * cos(theta) * cos(theta);

  // Closed formula
  Ell[0] = atan( (XYZ[2] + e2c * bell * sin3) / (ss - e2 * t_CST::aell * cos3) );
  Ell[1] = atan2(XYZ[1],XYZ[0]) ;
  nn = t_CST::aell/sqrt(1.0-e2*sin(Ell[0])*sin(Ell[0])) ;
  Ell[2] = ss / cos(Ell[0]) - nn;

  const int MAXITER = 100;
  for (int ii = 1; ii <= MAXITER; ii++) {
    nn     = t_CST::aell/sqrt(1.0-e2*sin(Ell[0])*sin(Ell[0])) ;
    hOld   = Ell[2] ;
    phiOld = Ell[0] ;
    Ell[2] = ss/cos(Ell[0])-nn ;
    Ell[0] = atan(zps/(1.0-e2*nn/(nn+Ell[2]))) ;
    if ( fabs(phiOld-Ell[0]) <= 1.0e-11 && fabs(hOld-Ell[2]) <= 1.0e-5 ) {
      return success;
    }
  }

  return failure;
}

// Rectangular Coordinates -> North, East, Up Components
////////////////////////////////////////////////////////////////////////////
void xyz2neu(const double* Ell, const double* xyz, double* neu) {

  double sinPhi = sin(Ell[0]);
  double cosPhi = cos(Ell[0]);
  double sinLam = sin(Ell[1]);
  double cosLam = cos(Ell[1]);

  neu[0] = - sinPhi*cosLam * xyz[0]
           - sinPhi*sinLam * xyz[1]
           + cosPhi        * xyz[2];

  neu[1] = - sinLam * xyz[0]
           + cosLam * xyz[1];

  neu[2] = + cosPhi*cosLam * xyz[0]
           + cosPhi*sinLam * xyz[1]
           + sinPhi        * xyz[2];
}

// North, East, Up Components -> Rectangular Coordinates
////////////////////////////////////////////////////////////////////////////
void neu2xyz(const double* Ell, const double* neu, double* xyz) {

  double sinPhi = sin(Ell[0]);
  double cosPhi = cos(Ell[0]);
  double sinLam = sin(Ell[1]);
  double cosLam = cos(Ell[1]);

  xyz[0] = - sinPhi*cosLam * neu[0]
           - sinLam        * neu[1]
           + cosPhi*cosLam * neu[2];

  xyz[1] = - sinPhi*sinLam * neu[0]
           + cosLam        * neu[1]
           + cosPhi*sinLam * neu[2];

  xyz[2] = + cosPhi        * neu[0]
           + sinPhi        * neu[2];
}

// Rectangular Coordinates -> Geocentric Coordinates
////////////////////////////////////////////////////////////////////////////
t_irc xyz2geoc(const double* XYZ, double* Geoc) {

  const double bell = t_CST::aell*(1.0-1.0/t_CST::fInv) ;
  const double e2 = (t_CST::aell*t_CST::aell-bell*bell)/(t_CST::aell*t_CST::aell) ;
  double Ell[3];
  if (xyz2ell(XYZ, Ell) != success) {
    return failure;
  }
  double rho = sqrt(XYZ[0]*XYZ[0]+XYZ[1]*XYZ[1]+XYZ[2]*XYZ[2]);
  double Rn = t_CST::aell/sqrt(1-e2*pow(sin(Ell[0]),2));

  Geoc[0] = atan((1-e2 * Rn/(Rn + Ell[2])) * tan(Ell[0]));
  Geoc[1] = Ell[1];
  Geoc[2] = rho-t_CST::rgeoc;

  return success;
}

//
////////////////////////////////////////////////////////////////////////////
double Frac (double x) {
  return x-floor(x);
}

//
////////////////////////////////////////////////////////////////////////////
double Modulo (double x, double y) {
  return y*Frac(x/y);
}

// Round to nearest integer
////////////////////////////////////////////////////////////////////////////
double nint(double val) {
  return ((val < 0.0) ? -floor(fabs(val)+0.5) : floor(val+0.5));
}

//
////////////////////////////////////////////////////////////////////////////
double factorial(int n) {
  if (n == 0) {
    return 1;
  }
  else {
    return (n * factorial(n - 1));
  }
}

//
////////////////////////////////////////////////////////////////////////////
double associatedLegendreFunction(int n, int m, double t) {
  double sum = 0.0;
  int    r   = (int) floor((n - m) / 2);
  for (int k = 0; k <= r; k++) {
    sum += (pow(-1.0, (double)k) * factorial(2*n - 2*k)
            / (factorial(k) * factorial(n-k) * factorial(n-m-2*k))
            * pow(t, (double)n-m-2*k));
  }
  double fac = pow(2.0,(double) -n) * pow((1 - t*t), (double)m/2);
  return sum *= fac;
}


// Jacobian XYZ --> NEU
////////////////////////////////////////////////////////////////////////////
void jacobiXYZ_NEU(const double* Ell, Matrix& jacobi) {

  Tracer tracer("jacobiXYZ_NEU");

  double sinPhi = sin(Ell[0]);
  double cosPhi = cos(Ell[0]);
  double sinLam = sin(Ell[1]);
  double cosLam = cos(Ell[1]);

  jacobi(1,1) = - sinPhi * cosLam;
  jacobi(1,2) = - sinPhi * sinLam;
  jacobi(1,3) =   cosPhi;

  jacobi(2,1) = - sinLam;
  jacobi(2,2) =   cosLam;
  jacobi(2,3) =   0.0;

  jacobi(3,1) = cosPhi * cosLam;
  jacobi(3,2) = cosPhi * sinLam;
  jacobi(3,3) = sinPhi;
}

// Jacobian Ell --> XYZ
////////////////////////////////////////////////////////////////////////////
void jacobiEll_XYZ(const double* Ell, Matrix& jacobi) {

  Tracer tracer("jacobiEll_XYZ");

  double sinPhi = sin(Ell[0]);
  double cosPhi = cos(Ell[0]);
  double sinLam = sin(Ell[1]);
  double cosLam = cos(Ell[1]);
  double hh     = Ell[2];

  double bell =  t_CST::aell*(1.0-1.0/t_CST::fInv);
  double e2   = (t_CST::aell*t_CST::aell-bell*bell)/(t_CST::aell*t_CST::aell) ;
  double nn   =  t_CST::aell/sqrt(1.0-e2*sinPhi*sinPhi) ;

  jacobi(1,1) = -(nn+hh) * sinPhi * cosLam;
  jacobi(1,2) = -(nn+hh) * cosPhi * sinLam;
  jacobi(1,3) = cosPhi * cosLam;

  jacobi(2,1) = -(nn+hh) * sinPhi * sinLam;
  jacobi(2,2) =  (nn+hh) * cosPhi * cosLam;
  jacobi(2,3) = cosPhi * sinLam;

  jacobi(3,1) = (nn*(1.0-e2)+hh) * cosPhi;
  jacobi(3,2) = 0.0;
  jacobi(3,3) = sinPhi;
}

// Covariance Matrix in NEU
////////////////////////////////////////////////////////////////////////////
void covariXYZ_NEU(const SymmetricMatrix& QQxyz, const double* Ell,
                   SymmetricMatrix& Qneu) {

  Tracer tracer("covariXYZ_NEU");

  Matrix CC(3,3);
  jacobiXYZ_NEU(Ell, CC);
  Qneu << CC * QQxyz * CC.t();
}

// Covariance Matrix in XYZ
////////////////////////////////////////////////////////////////////////////
void covariNEU_XYZ(const SymmetricMatrix& QQneu, const double* Ell,
                   SymmetricMatrix& Qxyz) {

  Tracer tracer("covariNEU_XYZ");

  Matrix CC(3,3);
  jacobiXYZ_NEU(Ell, CC);
  Qxyz << CC.t() * QQneu * CC;
}

// Fourth order Runge-Kutta numerical integrator for ODEs
////////////////////////////////////////////////////////////////////////////
ColumnVector rungeKutta4(
  double xi,              // the initial x-value
  const ColumnVector& yi, // vector of the initial y-values
  double dx,              // the step size for the integration
  double* acc,            // additional acceleration
  ColumnVector (*der)(double x, const ColumnVector& y, double* acc)
                          // A pointer to a function that computes the
                          // derivative of a function at a point (x,y)
                         ) {

  ColumnVector k1 = der(xi       , yi       , acc) * dx;
  ColumnVector k2 = der(xi+dx/2.0, yi+k1/2.0, acc) * dx;
  ColumnVector k3 = der(xi+dx/2.0, yi+k2/2.0, acc) * dx;
  ColumnVector k4 = der(xi+dx    , yi+k3    , acc) * dx;

  ColumnVector yf = yi + k1/6.0 + k2/3.0 + k3/3.0 + k4/6.0;

  return yf;
}
//
////////////////////////////////////////////////////////////////////////////
double djul(long jj, long mm, double tt) {
  long    ii, kk;
  double  djul ;
  if( mm <= 2 ) {
    jj = jj - 1;
    mm = mm + 12;
  }
  ii   = jj/100;
  kk   = 2 - ii + ii/4;
  djul = (365.25*jj - fmod( 365.25*jj, 1.0 )) - 679006.0;
  djul = djul + floor( 30.6001*(mm + 1) ) + tt + kk;
  return djul;
}

//
////////////////////////////////////////////////////////////////////////////
double gpjd(double second, int nweek) {
  double deltat;
  deltat = nweek*7.0 + second/86400.0 ;
  return( 44244.0 + deltat) ;
}

//
////////////////////////////////////////////////////////////////////////////
void jdgp(double tjul, double & second, long & nweek) {
  double      deltat;
  deltat = tjul - 44244.0 ;
  nweek = (long) floor(deltat/7.0);
  second = (deltat - (nweek)*7.0)*86400.0;
}

//
////////////////////////////////////////////////////////////////////////////
void jmt(double djul, long& jj, long& mm, double& dd) {
  long   ih, ih1, ih2 ;
  double t1, t2,  t3, t4;
  t1  = 1.0 + djul - fmod( djul, 1.0 ) + 2400000.0;
  t4  = fmod( djul, 1.0 );
  ih  = long( (t1 - 1867216.25)/36524.25 );
  t2  = t1 + 1 + ih - ih/4;
  t3  = t2 - 1720995.0;
  ih1 = long( (t3 - 122.1)/365.25 );
  t1  = 365.25*ih1 - fmod( 365.25*ih1, 1.0 );
  ih2 = long( (t3 - t1)/30.6001 );
  dd  = t3 - t1 - (int)( 30.6001*ih2 ) + t4;
  mm  = ih2 - 1;
  if ( ih2 > 13 ) mm = ih2 - 13;
  jj  = ih1;
  if ( mm <= 2 ) jj = jj + 1;
}

//
////////////////////////////////////////////////////////////////////////////
void GPSweekFromDateAndTime(const QDateTime& dateTime,
                            int& GPSWeek, double& GPSWeeks) {

  static const QDateTime zeroEpoch(QDate(1980, 1, 6),QTime(),Qt::UTC);

  GPSWeek = zeroEpoch.daysTo(dateTime) / 7;

  int weekDay = dateTime.date().dayOfWeek() + 1;  // Qt: Monday = 1
  if (weekDay > 7) weekDay = 1;

  GPSWeeks = (weekDay - 1) * 86400.0
             - dateTime.time().msecsTo(QTime()) / 1e3;
}

//
////////////////////////////////////////////////////////////////////////////
void GPSweekFromYMDhms(int year, int month, int day, int hour, int min,
                       double sec, int& GPSWeek, double& GPSWeeks) {

  double mjd = djul(year, month, day);

  long GPSWeek_long;
  jdgp(mjd, GPSWeeks, GPSWeek_long);
  GPSWeek = GPSWeek_long;
  GPSWeeks += hour * 3600.0 + min * 60.0 + sec;
}

//
////////////////////////////////////////////////////////////////////////////
void mjdFromDateAndTime(const QDateTime& dateTime, int& mjd, double& dayfrac) {

  static const QDate zeroDate(1858, 11, 17);

  mjd     = zeroDate.daysTo(dateTime.date());

  dayfrac = (dateTime.time().hour() +
             (dateTime.time().minute() +
              (dateTime.time().second() +
               dateTime.time().msec() / 1000.0) / 60.0) / 60.0) / 24.0;
}

//
////////////////////////////////////////////////////////////////////////////
bool findInVector(const vector<QString>& vv, const QString& str) {
  std::vector<QString>::const_iterator it;
  for (it = vv.begin(); it != vv.end(); ++it) {
    if ( (*it) == str) {
      return true;
    }
  }
  return false;
}

//
////////////////////////////////////////////////////////////////////////////
int readInt(const QString& str, int pos, int len, int& value) {
  bool ok;
  value = str.mid(pos, len).toInt(&ok);
  return ok ? 0 : 1;
}

//
////////////////////////////////////////////////////////////////////////////
int readDbl(const QString& str, int pos, int len, double& value) {
  QString hlp = str.mid(pos, len);
  for (int ii = 0; ii < hlp.length(); ii++) {
    if (hlp[ii]=='D' || hlp[ii]=='d' || hlp[ii] == 'E') {
      hlp[ii]='e';
    }
  }
  bool ok;
  value = hlp.toDouble(&ok);
  return ok ? 0 : 1;
}

// Topocentrical Distance and Elevation
////////////////////////////////////////////////////////////////////////////
void topos(double xRec, double yRec, double zRec,
           double xSat, double ySat, double zSat,
           double& rho, double& eleSat, double& azSat) {

  double dx[3];
  dx[0] = xSat-xRec;
  dx[1] = ySat-yRec;
  dx[2] = zSat-zRec;

  rho =  sqrt( dx[0]*dx[0] + dx[1]*dx[1] + dx[2]*dx[2] );

  double xyzRec[3];
  xyzRec[0] = xRec;
  xyzRec[1] = yRec;
  xyzRec[2] = zRec;

  double Ell[3];
  double neu[3];
  xyz2ell(xyzRec, Ell);
  xyz2neu(Ell, dx, neu);

  eleSat = acos( sqrt(neu[0]*neu[0] + neu[1]*neu[1]) / rho );
  if (neu[2] < 0.0) {
    eleSat *= -1.0;
  }

  azSat  = atan2(neu[1], neu[0]);
}

// Degrees -> degrees, minutes, seconds
////////////////////////////////////////////////////////////////////////////
void deg2DMS(double decDeg, int& deg, int& min, double& sec) {
  int sgn = (decDeg < 0.0 ? -1 : 1);
  deg = static_cast<int>(decDeg);
  min =  sgn *  static_cast<int>((decDeg - deg)*60);
  sec =  (sgn* (decDeg - deg) - min/60.0) * 3600.0;
}

//
////////////////////////////////////////////////////////////////////////////
QString fortranFormat(double value, int width, int prec) {
  int    expo = value == 0.0 ? 0 : int(log10(fabs(value)));
  double mant = value == 0.0 ? 0 : value / pow(10.0, double(expo));
  if (fabs(mant) >= 1.0) {
    mant /= 10.0;
    expo += 1;
  }
  if (expo >= 0) {
    return QString("%1e+%2").arg(mant, width-4, 'f', prec).arg(expo,  2, 10, QChar('0'));
  }
  else {
    return QString("%1e-%2").arg(mant, width-4, 'f', prec).arg(-expo, 2, 10, QChar('0'));
  }
}

//
//////////////////////////////////////////////////////////////////////////////
void kalman(const vector<unique_ptr<const RowVector>>& vAA, 
            const vector<double>& vll, const vector<double>& sigma,
            SymmetricMatrix& QQ, ColumnVector& xx) {

  unsigned nPar = xx.Nrows();
  unsigned nObs = vAA.size();

  Matrix         AA(nObs, nPar);
  ColumnVector   ll(nObs);
  DiagonalMatrix PP(nObs);
  for (unsigned iObs = 0; iObs < nObs; ++iObs) {
    ll[iObs]       = vll[iObs];
    PP[iObs]       = 1.0 / (sigma[iObs] * sigma[iObs]);
    const RowVector& row = *vAA[iObs];
    AA.row(iObs+1) = row;
  }
   return kalman(AA, ll, PP, QQ, xx);
}

//
//////////////////////////////////////////////////////////////////////////////
void kalman(const Matrix& AA, const ColumnVector& ll, const DiagonalMatrix& PP,
            SymmetricMatrix& QQ, ColumnVector& xx) {

  Tracer tracer("kalman");

  int nPar = AA.Ncols();
  int nObs = AA.Nrows();
  UpperTriangularMatrix SS = Cholesky(QQ).t();

  Matrix SA = SS*AA.t();
  Matrix SRF(nObs+nPar, nObs+nPar); SRF = 0;
  for (int ii = 1; ii <= nObs; ++ii) {
    SRF(ii,ii) = 1.0 / sqrt(PP(ii,ii));
  }

  SRF.SubMatrix   (nObs+1, nObs+nPar, 1, nObs) = SA;
  SRF.SymSubMatrix(nObs+1, nObs+nPar)          = SS;

  UpperTriangularMatrix UU;
  QRZ(SRF, UU);

  SS = UU.SymSubMatrix(nObs+1, nObs+nPar);
  UpperTriangularMatrix SH_rt = UU.SymSubMatrix(1, nObs);
  Matrix YY  = UU.SubMatrix(1, nObs, nObs+1, nObs+nPar);

  UpperTriangularMatrix SHi = SH_rt.i();

  Matrix KT  = SHi * YY;
  SymmetricMatrix Hi; Hi << SHi * SHi.t();

  xx += KT.t() * (ll - AA * xx);
  QQ << (SS.t() * SS);
}

//
////////////////////////////////////////////////////////////////////////////
double accuracyFromIndex(int index, t_eph::e_system system) {
double accuracy = -1.0;

  if (system == t_eph::GPS ||
      system == t_eph::BDS ||
      system == t_eph::SBAS||
      system == t_eph::QZSS||
      system == t_eph::NavIC) {
    if ((index >= 0) && (index <= 6)) {
      if (index == 3) {
        accuracy =  ceil(10.0 * pow(2.0, (double(index) / 2.0) + 1.0)) / 10.0;
      }
      else {
        accuracy = floor(10.0 * pow(2.0, (double(index) / 2.0) + 1.0)) / 10.0;
      }
    }
    else if ((index > 6) && (index < 15)) {
      accuracy = (10.0 * pow(2.0, (double(index) - 2.0))) / 10.0;

    } // index = 15: absence of accuracy prediction => use SV on your own risk
    else {
      accuracy = 8192.0;
    }
  }
  else if (system == t_eph::Galileo) {
    if ((index >= 0) && (index <= 49)) {
      accuracy = (double(index) / 100.0);
    }
    else if ((index > 49) && (index <= 74)) {
      accuracy = (50.0 + (double(index) - 50.0) * 2.0) / 100.0;
    }
    else if ((index > 74) && (index <= 99)) {
      accuracy = 1.0 + (double(index) - 75.0) * 0.04;
    }
    else if ((index > 99) && (index <= 125)) {
      accuracy = 2.0 + (double(index) - 100.0) * 0.16;
    }
    else {
      accuracy = -1.0;
    }
  }
  return accuracy;
}

//
////////////////////////////////////////////////////////////////////////////
int indexFromAccuracy(double accuracy, t_eph::e_system system) {

  if (system == t_eph::GPS ||
      system == t_eph::BDS ||
      system == t_eph::SBAS ||
      system == t_eph::QZSS ||
      system == t_eph::NavIC) {

    if      (accuracy <= 2.40) {
      return 0;
    }
    else if (accuracy <= 3.40) {
      return 1;
    }
    else if (accuracy <= 4.85) {
      return 2;
    }
    else if (accuracy <= 6.85) {
      return 3;
    }
    else if (accuracy <= 9.65) {
      return 4;
    }
    else if (accuracy <= 13.65) {
      return 5;
    }
    else if (accuracy <= 24.00) {
      return 6;
    }
    else if (accuracy <= 48.00) {
      return 7;
    }
    else if (accuracy <= 96.00) {
      return 8;
    }
    else if (accuracy <= 192.00) {
      return 9;
    }
    else if (accuracy <= 384.00) {
      return 10;
    }
    else if (accuracy <= 768.00) {
      return 11;
    }
    else if (accuracy <= 1536.00) {
      return 12;
    }
    else if (accuracy <= 3072.00) {
      return 13;
    }
    else if (accuracy <= 6144.00) {
      return 14;
    }
    else {
      return 15;
    }
  }

  if (system == t_eph::Galileo) {
    if      (accuracy <= 0.49) {
      return int(ceil(accuracy * 100.0));
    }
    else if (accuracy <= 0.98) {
      return int(50.0 + (((accuracy * 100.0) - 50) / 2.0));
    }
    else if (accuracy <= 2.0) {
      return int(75.0 + ((accuracy - 1.0) / 0.04));
    }
    else if (accuracy <= 6.0) {
      return int(100.0 + ((accuracy - 2.0) / 0.16));
    }
    else {
      return 255;
    }
  }

  return (system == t_eph::Galileo) ? 255 : 15;
}

// Returns fit interval in hours from flag
////////////////////////////////////////////////////////////////////////////
double fitIntervalFromFlag(int flag, double iodc, t_eph::e_system system) {
  double fitInterval = 0.0;

  switch (flag) {
    case 0:
      if      (system == t_eph::GPS) {
        fitInterval = 4.0;
      }
      else if (system == t_eph::QZSS) {
        fitInterval = 2.0;
      }
      break;
    case 1:
      if (system == t_eph::GPS) {
        if      (iodc >= 240 && iodc <= 247) {
          fitInterval =  8.0;
        }
        else if ((iodc >= 248 && iodc <= 255) ||
                 (iodc == 496) ) {
          fitInterval = 14.0;
        }
        else if ((iodc >=  497 && iodc <=  503) ||
                 (iodc >= 2021 && iodc <= 1023) ) {
          fitInterval = 26.0;
        }
        else {
          fitInterval =  6.0;
        }
      }
      break;
  }
  return fitInterval;
}

// Returns CRC24
////////////////////////////////////////////////////////////////////////////
unsigned long CRC24(long size, const unsigned char *buf) {
  unsigned long crc = 0;
  int ii;
  while (size--) {
    crc ^= (*buf++) << (16);
    for(ii = 0; ii < 8; ii++) {
      crc <<= 1;
      if (crc & 0x1000000) {
        crc ^= 0x01864cfb;
      }
    }
  }
  return crc;
}

// Extracts k bits from position pos and returns the extracted value as unsigned int
////////////////////////////////////////////////////////////////////////////
unsigned bitExtracted(unsigned number, unsigned k, unsigned pos) {
  // Right shift 'num' by 'pos' bits
  unsigned shifted = number >> pos;

  // Create a mask with 'k' bits set to 1
  unsigned mask = (1 << k) - 1;

  // Apply the mask to the shifted number
  return shifted & mask;
}

// Convert RTCM3 lock-time indicator to minimum lock time in seconds
////////////////////////////////////////////////////////////////////////////
double lti2sec(int type, int lti) {

  if ( (type>=1001 && type<=1004) ||
       (type>=1009 && type<=1012)    ) { // RTCM3 msg 100[1...4] and 10[09...12]
         if (lti<   0) return  -1;
    else if (lti<  24) return   1*lti;      // [  0   1   23]
    else if (lti<  48) return   2*lti-24;   // [ 24   2   70]
    else if (lti<  72) return   4*lti-120;  // [ 72   4  164]
    else if (lti<  96) return   8*lti-408;  // [168   8  352]
    else if (lti< 120) return  16*lti-1176; // [360  16  728]
    else if (lti< 127) return  32*lti-3096; // [744  32  905]
    else if (lti==127) return  937;
    else               return  -1.0;
  }
  else if (type%10==2 || type%10==3 ||
           type%10==4 || type%10==5) {  // RTCM3 MSM-2/-3/-4/-5
    switch(lti) {
      case( 0) : return      0;
      case( 1) : return     32e-3;
      case( 2) : return     64e-3;
      case( 3) : return    128e-3;
      case( 4) : return    256e-3;
      case( 5) : return    512e-3;
      case( 6) : return   1024e-3;
      case( 7) : return   2048e-3;
      case( 8) : return   4096e-3;
      case( 9) : return   8192e-3;
      case(10) : return  16384e-3;
      case(11) : return  32768e-3;
      case(12) : return  65536e-3;
      case(13) : return 131072e-3;
      case(14) : return 262144e-3;
      case(15) : return 524288e-3;
      default  : return     -1.0;
    };
  }
  else if (type%10==6 || type%10==7) {  // RTCM3 MSM-6 and MSM-7
         if (lti<   0) return (     -1               );
    else if (lti<  64) return (      1*lti           )*1e-3;
    else if (lti<  96) return (      2*lti-64        )*1e-3;
    else if (lti< 128) return (      4*lti-256       )*1e-3;
    else if (lti< 160) return (      8*lti-768       )*1e-3;
    else if (lti< 192) return (     16*lti-2048      )*1e-3;
    else if (lti< 224) return (     32*lti-5120      )*1e-3;
    else if (lti< 256) return (     64*lti-12288     )*1e-3;
    else if (lti< 288) return (    128*lti-28672     )*1e-3;
    else if (lti< 320) return (    256*lti-65536     )*1e-3;
    else if (lti< 352) return (    512*lti-147456    )*1e-3;
    else if (lti< 384) return (   1024*lti-327680    )*1e-3;
    else if (lti< 416) return (   2048*lti-720896    )*1e-3;
    else if (lti< 448) return (   4096*lti-1572864   )*1e-3;
    else if (lti< 480) return (   8192*lti-3407872   )*1e-3;
    else if (lti< 512) return (  16384*lti-7340032   )*1e-3;
    else if (lti< 544) return (  32768*lti-15728640  )*1e-3;
    else if (lti< 576) return (  65536*lti-33554432  )*1e-3;
    else if (lti< 608) return ( 131072*lti-71303168  )*1e-3;
    else if (lti< 640) return ( 262144*lti-150994944 )*1e-3;
    else if (lti< 672) return ( 524288*lti-318767104 )*1e-3;
    else if (lti< 704) return (1048576*lti-671088640 )*1e-3;
    else if (lti==704) return (2097152*lti-1409286144)*1e-3;
    else               return (     -1.0               );
  }
  else {
    return -1.0;
  };
};

// 
////////////////////////////////////////////////////////////////////////////
double sqrtMod(double val) {
  return val > 0.0 ? std::sqrt(val) : 0.0;
}
