import math


class Location:

    EARTH_RADIUS_METRES = 6.371e6

    def __init__(self, latitude, longitude, altitude):
        self.latitude = latitude
        self.longitude = longitude
        self.altitude = altitude

    @property
    def latitude_radian(self):
        return math.radians(self.latitude)

    @property
    def longitude_radian(self):
        return math.radians(self.longitude)

    @staticmethod
    def haversine(angle_rad):
        # http://mathworld.wolfram.com/Haversine.html
        return math.sin(angle_rad / 2) ** 2

    @staticmethod
    def haversine_inv(hav):
        # return math.atan2(math.sqrt(hav), math.sqrt(1-hav)) * 2
        return math.asin(math.sqrt(hav)) * 2

    @staticmethod
    def haversine_distance_metres(a, b):
        # https://en.wikipedia.org/wiki/Haversine_formula
        hav = Location.haversine(b.latitude_radian - a.latitude_radian) \
            + math.cos(a.latitude_radian) * math.cos(b.latitude_radian) \
                * Location.haversine(b.longitude_radian - a.longitude_radian)
        return Location.haversine_inv(hav) * Location.EARTH_RADIUS_METRES