import { Coordinates } from '@mt/common-types';

const EARTH_RADIUS = 6372795; // meters

export function getDistance(a: Coordinates, b: Coordinates): number {
  const { PI, sin, cos, pow, sqrt, atan2 } = Math;

  const aRad = {
    lat: (a.lat * PI) / 180,
    lon: (a.lon * PI) / 180,
  };

  const bRad = {
    lat: (b.lat * PI) / 180,
    lon: (b.lon * PI) / 180,
  };

  const delta = bRad.lon - aRad.lon;

  // вычисления длины большого круга
  const y = sqrt(
    pow(cos(bRad.lat) * sin(delta), 2) +
      pow(cos(aRad.lat) * sin(bRad.lat) - sin(aRad.lat) * cos(bRad.lat) * cos(delta), 2)
  );
  const x = sin(aRad.lat) * sin(bRad.lat) + cos(aRad.lat) * cos(bRad.lat) * cos(delta);

  return +(atan2(y, x) * EARTH_RADIUS).toFixed(2);
}