// Geografische Hilfsfunktionen.

(function () {
  const EARTH_RADIUS_KM = 6371;

  function toRad(deg) {
    return (deg * Math.PI) / 180;
  }

  /**
   * Entfernung zwischen zwei Koordinaten in Kilometern (Haversine-Formel).
   * @param {{lat:number,lng:number}} a
   * @param {{lat:number,lng:number}} b
   */
  function haversineDistanceKm(a, b) {
    const dLat = toRad(b.lat - a.lat);
    const dLng = toRad(b.lng - a.lng);
    const lat1 = toRad(a.lat);
    const lat2 = toRad(b.lat);

    const h =
      Math.sin(dLat / 2) ** 2 +
      Math.cos(lat1) * Math.cos(lat2) * Math.sin(dLng / 2) ** 2;
    const c = 2 * Math.atan2(Math.sqrt(h), Math.sqrt(1 - h));

    return EARTH_RADIUS_KM * c;
  }

  function isValidCoordinate(lat, lng) {
    return (
      typeof lat === 'number' &&
      typeof lng === 'number' &&
      Number.isFinite(lat) &&
      Number.isFinite(lng) &&
      lat >= -90 &&
      lat <= 90 &&
      lng >= -180 &&
      lng <= 180
    );
  }

  EventMap.utils.haversineDistanceKm = haversineDistanceKm;
  EventMap.utils.isValidCoordinate = isValidCoordinate;
})();