// Utility functions

// Copyright Ole Nielsen 2002-2004, Peter Hayes 1999-2001


function datestring(obs) {
// datestring provides a locale independent format
  var datestr = "";  datestr += obs.year;
  datestr += ((obs.month < 10) ? ":0" : ":") + obs.month;
  datestr += ((obs.day < 10) ? ":0" : ":") + obs.day;
  return datestr;
}		// end datestring()


function datestring2(year,month,day) {
  var datestr = "";  datestr += year;
  datestr += ((month < 10) ? ":0" : ":") + month;
  datestr += ((day < 10) ? ":0" : ":") + day;
  return datestr;
}		// end datestring2()


function adjustTime(obs,amount) {
// update date and time, amount is in minutes (may be negative)
// added 2004
    month_length[1] = leapyear(obs.year) ? 29 : 28;
	if (amount<0) {
		amount = Math.abs(amount);
		obs.minutes -= amount%60; amount = Math.floor(amount/60.0);
		obs.hours -= amount%24; amount = Math.floor(amount/24.0);
		obs.day -= amount;
		if (obs.minutes < 0) {
			obs.minutes += 60;
			obs.hours -= 1;
		}
		if (obs.hours < 0) {
			obs.hours += 24;
			obs.day -= 1;
		}
		while (obs.day < 1) {
			obs.day += month_length[obs.month-2+(obs.month==1?12:0)];
			obs.month -= 1; 
			if (obs.month == 0) {
				obs.year -= 1;
				obs.month = 12;
				month_length[1] = (leapyear(obs.year) ? 29 : 28);
			}
		}
	}
	else {
		obs.minutes+=amount%60; amount=Math.floor(amount/60.0);
		obs.hours+=amount%24; amount=Math.floor(amount/24.0);
		obs.day+=amount;
		if (obs.minutes > 59) {
			obs.minutes -= 60;
			obs.hours += 1;
		}
		if (obs.hours > 23) {
			obs.hours -= 24;
			obs.day += 1;
		}
		while (obs.day > month_length[obs.month-1]) {
			obs.day -= month_length[obs.month-1];
			obs.month += 1; 
			if (obs.month == 13) {
				obs.year += 1;
				obs.month = 1;
				month_length[1] = (leapyear(obs.year) ? 29 : 28);
			}
		}
	}
}		// end adjustTime()


function hmsstring(t) {
// the caller must add a leading + if required.
  var hours = Math.abs(t);
  var minutes = 60.0*(hours-Math.floor(hours));
  hours=Math.floor(hours);
  var seconds = Math.round(60.0*(minutes-Math.floor(minutes)));
  minutes=Math.floor(minutes);
  if (seconds >= 60) { minutes+=1; seconds-=60; }
  if (minutes >= 60) { hour+=1; minutes-=60; }
  if (hours >= 24) { hours-=24; }
  var hmsstr=(t < 0) ? "-" : "";
  hmsstr=((hours < 10) ? "0" : "" )+hours;
  hmsstr+=((minutes < 10) ? ":0" : ":" )+minutes;
  hmsstr+=((seconds < 10) ? ":0" : ":" )+seconds;
  return hmsstr;
}		// end hmsstring()


function hmstring(t,plus) {
// hmstring converts hours to a string (+/-)hours:minutes, used for relative time (TZ)
  var hours = Math.abs(t);
  var minutes = Math.round(60.0*(hours-Math.floor(hours)));
  hours=Math.floor(hours);
  if (minutes >= 60) { hours+=1; minutes-=60; }	// minutes could be 60 due to rounding
  if (hours >= 24) { hours-=24; }
  var hmstr = (t < 0) ? "-" : (plus?"+":"");
  hmstr += ((hours < 10) ? "0" : "" )+hours;
  hmstr += ((minutes < 10) ? ":0" : ":" )+minutes;
  return hmstr;
}		// end hmstring()


function hmstring2(hours,minutes,seconds) {
// hmstring2 returns time as a string HH:MM (added 2004.01.02), seconds needed for rounding
	if (seconds>=30) minutes++;
	if (minutes>=60) {hours++; minutes=0;}
	var timestr = ((hours < 10) ? "0" : "") + hours;	
	timestr += ((minutes < 10) ? ":0" : ":") + minutes;
	return timestr;
}		// end hmstring2()


function dmsstring(d) {
// dmsstring converts lat/long angle to unsigned string d:m:s
  var deg = Math.abs(d);
  var minutes = 60.0*(deg-Math.floor(deg));
  deg=Math.floor(deg);
  var seconds = Math.round(60.0*(minutes-Math.floor(minutes)));
  minutes=Math.floor(minutes);
  if (seconds >= 60) { minutes+=1; seconds-=60; }
  if (minutes >= 60) { deg+=1; minutes-=60; }
  hmsstr=((deg < 10) ? "0" : "" )+deg;
  hmsstr+=((minutes < 10) ? ":0" : ":" )+minutes;
  hmsstr+=((seconds < 10) ? ":0" : ":" )+seconds;
  return hmsstr;
}		// end dmsstring()


function dmstring(d) {
// dmstring converts lat/long angle to unsigned string d:m
  var deg = Math.abs(d);
  var minutes = 60.0*(deg-Math.floor(deg));
  deg=Math.floor(deg);
  var seconds = Math.round(60.0*(minutes-Math.floor(minutes)));
  minutes=Math.floor(minutes);
  if (seconds >= 30) { minutes+=1; }
  if (minutes >= 60) { deg+=1; minutes-=60; }
  hmstr=((deg < 10) ? "0" : "" )+deg;
	hmstr+=((minutes < 10) ? ":0" : ":" )+minutes;
  return hmstr;
} // end dmstring()


function anglestring(a,circle,arcmin) {
	// Return angle as degrees:minutes. 'circle' is true for range between 0 and 360 
	// and false for -90 to +90, if 'arcmin' use deg and arcmin symbols
  var ar=Math.round(a*60)/60;
  var deg=Math.abs(ar);
  var min=Math.round(60.0*(deg-Math.floor(deg)));
  if (min >= 60) { deg+=1; min=0; }
  var anglestr="";
  if (!circle) anglestr+=(ar < 0 ? "-" : "+");
  if (circle) anglestr+=((Math.floor(deg) < 100) ? "0" : "" );
  anglestr+=((Math.floor(deg) < 10) ? "0" : "" )+Math.floor(deg);
  if (arcmin) anglestr+=((min < 10) ? "&deg;0" : "&deg;")+(min)+"' ";
	else anglestr+=((min < 10) ? ":0" : ":" )+(min);
  return anglestr;
} // end anglestring()


function fixnum(n,l,d) {
	// convert float n to right adjusted string of length l with d digits after decimal point.
	// the sign always requires one character, allow for that in l!
	var m = 1;
	for (var i=0; i<d; i++) m*=10;
	var n1 = Math.round(Math.abs(n)*m);
	var nint = Math.floor(n1/m);
	var nfract = (n1 - m*nint) + ""; // force conversion to string
	while (nfract.length < d) nfract = "0" + nfract;
	var str = (n<0 ? "-" : " ") + nint;
	if (d > 0) str = str + "." + nfract;
	while (str.length<l) str = " " + str;
	return str;
} // end fixnum()


function fixstr(str,l) {
	// returns left-adjusted string of length l, pad with spaces or truncate as necessary
	if (str.length > l) return str.substring(0,l); 
	while (str.length < l) {
		str += " ";
	}
	return str;
}		// end fixstr()


function parsecol(str) {
	// parsecol converts deg:min:sec or hr:min:sec to a number
  var col1=str.indexOf(":");
  var col2=str.lastIndexOf(":");
  if (col1 < 0) return parseInt(str);
  if (str.substring(0,1) == "-") {
    var res=parseInt(str.substring(1,col1),10);
  } else {
    var res=parseInt(str.substring(0,col1),10);
  }
  if (col2 > col1) {
    res+=(parseInt(str.substring(col1+1,col2),10)/60.0) +
         (parseInt(str.substring(col2+1,str.length),10)/3600.0);
  } else {
    res+=(parseInt(str.substring(col1+1,str.length),10)/60.0);
  }
  if (str.substring(0,1) == "-") {
    return -res;
  } else {
    return res;
  }
}	// end parsecol()


function interpol(n,y1,y2,y3) {
	// interpolate y (Meeus 3.3)
	var a = y2-y1;
	var b = y3-y2;
	var c = b-a;
	return y2+(n/2)*(a+b+n*c);
}


function nzero(y1,y2,y3) {
	// Calculate value of interpolation factor for which y=zero. n0 should be within [-1:1] 
	// Meeus formula (3.7)	
	var a = y2-y1; var b = y3-y2; var c = b-a;
	var n0 = 0;
	do {
		dn0 = -(2*y2 + n0*(a+b+c*n0)) / (a+b+2*c*n0);
		n0 += dn0;
	} while (Math.abs(dn0) > 0.0001);
	return n0;
}		// end nzero()


function nextrem(y1,y2,y3) {
	// Calculate value of interpolation factor for which y reaches extremum (-1<n<1);
	var a = y2-y1; var b = y3-y2; var c = b-a;
	var nm = -(a+b)/(2*c);	// (3.5)
	return nm;
}		// end nextrem();


function isort(arr) {
// Sort 2D array in ascending order on first column of each element using insertion sort 
	for (var c=0; c<arr.length-1; c++) {	
		var tmp = arr[c+1]; var a = c;
		while (a>=0 && arr[a][0]>tmp[0]) {
			arr[a+1] = arr[a];
			a--;
		}
		arr[a+1] = tmp;
	}
}	// end isort()