// A missing/invalid pair must never become a marker at (0, 0).
export function coordinates(latitude, longitude) {
  const number = (value, limit) => {
    if ((typeof value !== 'number' && typeof value !== 'string') || String(value).trim() === '') return undefined;
    const parsed = Number(value);
    return Number.isFinite(parsed) && Math.abs(parsed) <= limit ? parsed : undefined;
  };
  const lat = number(latitude, 90), lon = number(longitude, 180);
  return lat === undefined || lon === undefined ? {} : { latitude: lat, longitude: lon };
}