/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  Convert latitude/longitude <=> OS National Grid Reference points (c) Chris Veness 2002-2009   */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

/* VJKL/WBC Some comments removed to save download time, this work is very much copyright Chris Veness still
	and used under the LGPL license. */
	
function LatLongToOSGrid(p) {
  var lat = p.lat.toRad(), lon = p.lon.toRad();
  
  var a = 6377563.396, b = 6356256.910;         
  var F0 = 0.9996012717;                        
  var lat0 = (49).toRad(), lon0 = (-2).toRad();  
  var N0 = -100000, E0 = 400000;               
  var e2 = 1 - (b*b)/(a*a);                     
  var n = (a-b)/(a+b), n2 = n*n, n3 = n*n*n;

  var cosLat = Math.cos(lat), sinLat = Math.sin(lat);
  var nu = a*F0/Math.sqrt(1-e2*sinLat*sinLat);              
  var rho = a*F0*(1-e2)/Math.pow(1-e2*sinLat*sinLat, 1.5);
  var eta2 = nu/rho-1;

  var Ma = (1 + n + (5/4)*n2 + (5/4)*n3) * (lat-lat0);
  var Mb = (3*n + 3*n*n + (21/8)*n3) * Math.sin(lat-lat0) * Math.cos(lat+lat0);
  var Mc = ((15/8)*n2 + (15/8)*n3) * Math.sin(2*(lat-lat0)) * Math.cos(2*(lat+lat0));
  var Md = (35/24)*n3 * Math.sin(3*(lat-lat0)) * Math.cos(3*(lat+lat0));
  var M = b * F0 * (Ma - Mb + Mc - Md);             

  var cos3lat = cosLat*cosLat*cosLat;
  var cos5lat = cos3lat*cosLat*cosLat;
  var tan2lat = Math.tan(lat)*Math.tan(lat);
  var tan4lat = tan2lat*tan2lat;

  var I = M + N0;
  var II = (nu/2)*sinLat*cosLat;
  var III = (nu/24)*sinLat*cos3lat*(5-tan2lat+9*eta2);
  var IIIA = (nu/720)*sinLat*cos5lat*(61-58*tan2lat+tan4lat);
  var IV = nu*cosLat;
  var V = (nu/6)*cos3lat*(nu/rho-tan2lat);
  var VI = (nu/120) * cos5lat * (5 - 18*tan2lat + tan4lat + 14*eta2 - 58*tan2lat*eta2);

  var dLon = lon-lon0;
  var dLon2 = dLon*dLon, dLon3 = dLon2*dLon, dLon4 = dLon3*dLon, dLon5 = dLon4*dLon, dLon6 = dLon5*dLon;

  var N = I + II*dLon2 + III*dLon4 + IIIA*dLon6;
  var E = E0 + IV*dLon + V*dLon3 + VI*dLon5;

  return gridrefNumToLet(E, N, 8);
}

function gridrefLetToNum(gridref) {
  var l1 = gridref.toUpperCase().charCodeAt(0) - 'A'.charCodeAt(0);
  var l2 = gridref.toUpperCase().charCodeAt(1) - 'A'.charCodeAt(0);

  if (l1 > 7) l1--;
  if (l2 > 7) l2--;

  var e = ((l1-2)%5)*5 + (l2%5);
  var n = (19-Math.floor(l1/5)*5) - Math.floor(l2/5);

  gridref = gridref.slice(2).replace(/ /g,'');

  e += gridref.slice(0, gridref.length/2);
  n += gridref.slice(gridref.length/2);

  switch (gridref.length) {
    case 6: e += '50'; n += '50'; break;
    case 8: e += '5'; n += '5'; break;
  }

  return [e, n];
}

function gridrefNumToLet(e, n, digits) {
  var e100k = Math.floor(e/100000), n100k = Math.floor(n/100000);
  
  if (e100k<0 || e100k>6 || n100k<0 || n100k>12) return '';

  var l1 = (19-n100k) - (19-n100k)%5 + Math.floor((e100k+10)/5);
  var l2 = (19-n100k)*5%25 + e100k%5;

  if (l1 > 7) l1++;
  if (l2 > 7) l2++;
  var letPair = String.fromCharCode(l1+'A'.charCodeAt(0), l2+'A'.charCodeAt(0));

  e = Math.floor((e%100000)/Math.pow(10,5-digits/2));
  n = Math.floor((n%100000)/Math.pow(10,5-digits/2));

  var gridRef = letPair + ' ' + e.padLZ(digits/2) + ' ' + n.padLZ(digits/2);

  return gridRef;
}

Number.prototype.padLZ = function(width) {
  var num = this.toString(), len = num.length;
  for (var i=0; i<width-len; i++) num = '0' + num;
  return num;
}

function LatLon(lat, lon, height) {
  if (arguments.length < 3) height = 0;
  this.lat = lat;
  this.lon = lon;
  this.height = height;
}

String.prototype.parseDeg = function() {
  if (!isNaN(this)) return Number(this);            

  var degLL = this.replace(/^-/,'').replace(/[NSEW]/i,''); 
  var dms = degLL.split(/[^0-9.]+/);                   
  for (var i in dms) if (dms[i]=='') dms.splice(i,1);  
  switch (dms.length) {                              
    case 3:                                          
      var deg = dms[0]/1 + dms[1]/60 + dms[2]/3600; break;
    case 2:                                             
      var deg = dms[0]/1 + dms[1]/60; break;
    case 1:                                             
      if (/[NS]/i.test(this)) degLL = '0' + degLL;     
      var deg = dms[0].slice(0,3)/1 + dms[0].slice(3,5)/60 + dms[0].slice(5)/3600; break;
    default: return NaN;
  }
  if (/^-/.test(this) || /[WS]/i.test(this)) deg = -deg;
  
  return deg;
}

Number.prototype.toRad = function() {
  return this * Math.PI / 180;
}

Number.prototype.toDeg = function() { 
  return this * 180 / Math.PI;
}