namespace Graph{

    public struct Utils
    {
        public static float DistanceBetweenNodes(Node n1, Node n2)
        {
            return DistanceBetweenCoordinates(n1.lat, n1.lon, n2.lat, n2.lon);
        }

        public static float DistanceBetweenCoordinates(float lat1, float lon1, float lat2, float lon2)
        {
            const int earthRadius = 6371000;
            double differenceLat = DegreesToRadians(lat2 - lat1);
            double differenceLon = DegreesToRadians(lon2 - lon1);

            double lat1Rads = DegreesToRadians(lat1);
            double lat2Rads = DegreesToRadians(lat2);

            double a = Math.Sin(differenceLat / 2) * Math.Sin(differenceLat / 2) + Math.Sin(differenceLon / 2) * Math.Sin(differenceLon / 2) * Math.Cos(lat1Rads) * Math.Cos(lat2Rads);
            double c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));

            return Convert.ToSingle(earthRadius * c);
        }

        private static double DegreesToRadians(double deg)
        {
            return deg * Math.PI / 180.0;
        }

        private static double RadiansToDegrees(double rad)
        {
            return rad * 180.0 / Math.PI;
        }
    }
}