//  Fisher-Yates shuffle
function shuffle (array) {
	var i = 0,
	    j = 0,
	    temp = null;

	for (i = array.length - 1; i > 0; i -= 1) {
		j = Math.floor(Math.random() * (i + 1));
		temp = array[i];
		array[i] = array[j];
		array[j] = temp;
	}
	
	return array;
}

function getRandom(min, max) {
  return Math.random() * (max - min) + min;
}


function getNextHighestIndex(arr, value) {
    var i = arr.length;
    while (arr[--i] > value);
    return ++i; 
}


function getUrlParameter(e) {
	return decodeURI((new RegExp(e + "=(.+?)(&|$)").exec(location.search) || [, null])[1])
}


		
// convert celsius to farenheight
function C2F(c){
	return Math.round( c * 9 / 5 + 32 );
}


// meters per second to mph
function mps2mph(meters) {
	return Math.round(  parseFloat(meters) * 2.23694 );
}
	

// array swap
Array.prototype.swap = function(a,b){ var tmp=this[a];this[a]=this[b];this[b]=tmp;};

	
function degToCompass(deg){
    val = Math.round((deg/22.5)+.5);
    arr=["N","NE","E","SE","S","SW","W","NW"];
    return arr[(val % 8)];
}
	


function distance(lat1, lon1, lat2, lon2) {
	var radlat1 = Math.PI * lat1/180,
		radlat2 = Math.PI * lat2/180,
		theta = lon1-lon2,
		radtheta = Math.PI * theta/180,
		dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
	dist = Math.acos(dist);
	dist = dist * 180/Math.PI;
	dist = dist * 60 * 1.1515;
	return dist;
}


function dewPoint(tem, r){
    tem = -1.0*(tem-32)*5/9	;
    es = 6.112*Math.exp(-1.0*17.67*tem/(243.5 - tem));
    ed = r/100.0*es;
    eln = Math.log(ed/6.112);
    td = -243.5*eln/(eln - 17.67 );
    return Math.round( (td*9/5)+32 );	
}

function heatIndex(T, R) { // T = temp, R = relative humidity
	var T2 = T*T, R2= R*R,
		c1 = -42.379, c2 = 2.04901523, c3 = 10.14333127,
		c4 = -0.22475541, c5 = -6.83783*Math.pow(10,-3), c6 = -5.481717*Math.pow(10,-2),
		c7 = 1.22874*Math.pow(10,-3), c8 = 8.5282*Math.pow(10,-4), c9 = -1.99*Math.pow(10,-6);
		
	return Math.round(c1 + c2*T + c3 *R + c4*T*R + c5*T2 + c6*R2 + c7*T2*R + c8*T*R2 + c9*T2*R2);
}


// maps current condition code to icon
function getCCicon(ccCode){
	return "images/icons/" + ( "0" +  {0:1,1:1,2:1,3:1,4:1,5:2,6:38,7:3,8:4,9:5,10:6,11:7,12:7,13:9,14:10,15:39,16:12,17:13,18:13,19:17,20:15,21:16,22:14,23:18,24:18,25:42,26:20,27:21,28:22,29:23,30:24,31:25,32:26,33:27,34:28,35:38,36:41,37:31,38:31,39:31,40:30,41:12,42:9,43:12,44:24,45:1,46:10,47:1,3200:19}[ccCode]
	).slice(-2) + ".png";
}



// https://date-fns.org/docs/Getting-Started