const SONAR_DURATION = 5;

function fmod (x, y) {

	//  discuss at: https://locutus.io/php/fmod/
	// original by: Onno Marsman (https://twitter.com/onnomarsman)
	//    input by: Brett Zamir (https://brett-zamir.me)
	// bugfixed by: Kevin van Zonneveld (https://kvz.io)
	//   example 1: fmod(5.7, 1.3)
	//   returns 1: 0.5
	let tmp
	let tmp2
	let p = 0
	let pY = 0
	let l = 0.0
	let l2 = 0.0

	tmp = x.toExponential().match(/^.\.?(.*)e(.+)$/)
	p = parseInt(tmp[2], 10) - (tmp[1] + '').length

	tmp = y.toExponential().match(/^.\.?(.*)e(.+)$/)
	pY = parseInt(tmp[2], 10) - (tmp[1] + '').length

	if (pY > p) {
		p = pY
	}

	tmp2 = (x % y)

	if (p < -100 || p > 20) {

		// toFixed will give an out of bound error so we fix it like this:
		l = Math.round(Math.log(tmp2) / Math.log(10))
		l2 = Math.pow(10, l)

		return (tmp2 / l2).toFixed(l - p) * l2

	} else {

		return parseFloat(tmp2.toFixed(-p))
	}
}

function computeLatDistanceInKm (dest, orig) {

	// Approximation française
	return ((dest - orig) * 111);
}

function computeLonDistanceInKm (dest, orig) {

	// Approximation française
	return ((dest - orig) * 79);
}

function computeDelay (latDistanceKm, lonDistanceKm, sonarDuration) {

	placeDirection = Math.atan(latDistanceKm / lonDistanceKm);
	placeWay = lonDistanceKm < 0 ? -1 : 1;
	placeAngle = placeDirection * placeWay;

	unsignedAngle = placeAngle + (2 * Math.PI);

	animOrigAngle = 3 * Math.PI / 2;
	animAngle_verbose = animOrigAngle + unsignedAngle;
	animAngle_bounded = fmod(animAngle_verbose, (2 * Math.PI));

	circleRatio = animAngle_bounded / (2 * Math.PI);
	delay = circleRatio * sonarDuration;

	return delay;
}

var places = document.getElementsByClassName('place');
var map = document.getElementById('map');
var origLat = map.getAttribute('data-orig-lat');
var origLon = map.getAttribute('data-orig-lon');

for (place of places) {

	var placeLat = place.getAttribute("data-place-lat");
	var placeLon = place.getAttribute("data-place-lon");

	if ( (placeLat == origLat) && (placeLon == origLon) ) {

		place.style.animationName = "none";
		place.style.opacity = "1";

	} else {
		
		var latDistanceKm = computeLatDistanceInKm(placeLat, origLat);
		var lonDistanceKm = computeLonDistanceInKm(placeLon, origLon);

		var delay = computeDelay(latDistanceKm, lonDistanceKm, SONAR_DURATION);

		place.style.animationDelay = delay + 's';
	}
}