web/src/lib/geo.ts

export function haversineMiles(a: [number, number], b: [number, number]) {
  const toRad = (x: number) => (x * Math.PI) / 180;
  const R = 3958.7613; // Earth radius in miles
  const dLat = toRad(b[0] - a[0]);
  const dLon = toRad(b[1] - a[1]);
  const lat1 = toRad(a[0]);
  const lat2 = toRad(b[0]);
  const sinDLat = Math.sin(dLat / 2);
  const sinDLon = Math.sin(dLon / 2);
  const h =
    sinDLat * sinDLat + Math.cos(lat1) * Math.cos(lat2) * sinDLon * sinDLon;
  const c = 2 * Math.atan2(Math.sqrt(h), Math.sqrt(1 - h));
  return R * c;
}

export function timeAgo(iso: string, now: Date = new Date()) {
  const t = new Date(iso);
  const s = Math.max(0, Math.floor((now.getTime() - t.getTime()) / 1000));
  if (s < 60) return `${s}s ago`;
  const m = Math.floor(s / 60);
  if (m < 60) return `${m}m ago`;
  const h = Math.floor(m / 60);
  if (h < 24) return `${h}h ago`;
  const d = Math.floor(h / 24);
  return `${d}d ago`;
}