export function makeId(prefix) {
  return `${prefix}_${Date.now()}_${Math.random().toString(36).slice(2, 8)}`;
}

export function todayYMD() {
  const now = new Date();
  return `${now.getFullYear()}-${`${now.getMonth() + 1}`.padStart(2, '0')}-${`${now.getDate()}`.padStart(2, '0')}`;
}

export function parseYMD(value) {
  if (!value || !/^\d{4}-\d{2}-\d{2}$/.test(value)) return null;
  const d = new Date(`${value}T00:00:00`);
  return Number.isNaN(d.getTime()) ? null : d;
}

export function findActiveTripId(trips) {
  const today = parseYMD(todayYMD());
  if (!today) return null;
  const active = trips.find((trip) => {
    const start = parseYMD(trip.startDate);
    const end = parseYMD(trip.endDate);
    return !!start && !!end && today >= start && today <= end;
  });
  return active?.id || null;
}

export function findNextTripId(trips) {
  const today = parseYMD(todayYMD());
  if (!today) return null;

  const next = trips
    .map((trip) => ({ id: trip.id, start: parseYMD(trip.startDate) }))
    .filter((trip) => !!trip.start && trip.start >= today)
    .sort((a, b) => a.start - b.start)[0];

  return next?.id || null;
}

export function findBestTripId(trips) {
  const activeTripId = findActiveTripId(trips);
  if (activeTripId) return activeTripId;

  const nextTripId = findNextTripId(trips);
  if (nextTripId) return nextTripId;

  const latestPast = trips
    .map((trip) => ({ id: trip.id, end: parseYMD(trip.endDate), start: parseYMD(trip.startDate) }))
    .filter((trip) => !!trip.end || !!trip.start)
    .sort((a, b) => {
      const aTime = (a.end || a.start).getTime();
      const bTime = (b.end || b.start).getTime();
      return bTime - aTime;
    })[0];

  return latestPast?.id || null;
}