export function haversineDistance(lat1: number, lon1: number, lat2: number, lon2: number): number {
  const R = 6371e3; // Earth radius in meters
  const φ1 = (lat1 * Math.PI) / 180;
  const φ2 = (lat2 * Math.PI) / 180;
  const Δφ = ((lat2 - lat1) * Math.PI) / 180;
  const Δλ = ((lon2 - lon1) * Math.PI) / 180;

  const a =
    Math.sin(Δφ / 2) * Math.sin(Δφ / 2) +
    Math.cos(φ1) * Math.cos(φ2) * Math.sin(Δλ / 2) * Math.sin(Δλ / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

  return R * c; // Distance in meters
}

export async function reverseGeocode(lat: number, lon: number): Promise<string | undefined> {
  try {
    const response = await fetch(
      `https://nominatim.openstreetmap.org/reverse?format=json&lat=${lat}&lon=${lon}&zoom=14&addressdetails=1`,
      {
        headers: {
          'Accept-Language': 'en,fi'
        }
      }
    );
    if (!response.ok) return undefined;
    const data = await response.json();
    return data.display_name || data.name || undefined;
  } catch (error) {
    console.error('Geocoding failed:', error);
    return undefined;
  }
}