/**
 * Working-days date math for the Quotes dashboard.
 *
 * "Working days" = weekdays only. Saturdays and Sundays are skipped.
 * Public holidays are intentionally NOT subtracted — the team can layer
 * that on later if it becomes a problem; for the current "show me the
 * aged quotes" indicator, weekday-only is the right baseline.
 *
 * All comparisons are done in the browser's local time. Quotes have
 * `created` timestamps in ISO UTC; we convert to local-day boundaries
 * before counting so "3 working days old" means "3 weekdays since the
 * day this row was created, in the user's timezone".
 */

/** Strip a Date down to its local-day midnight. */
function startOfLocalDay(d: Date): Date {
  return new Date(d.getFullYear(), d.getMonth(), d.getDate());
}

/**
 * Number of working days (Mon–Fri) between `then` and `now`, exclusive
 * of both endpoints' days. So a quote created today returns 0; a quote
 * created yesterday on a weekday returns 1; a quote created Friday
 * morning checked Monday morning returns 1 (Sat/Sun skipped).
 *
 * Returns 0 when `then` is in the future or on the same day as `now`.
 */
export function workingDaysBetween(then: Date | string, now: Date = new Date()): number {
  const thenDate = typeof then === "string" ? new Date(then) : then;
  if (Number.isNaN(thenDate.getTime())) return 0;

  const startThen = startOfLocalDay(thenDate);
  const startNow = startOfLocalDay(now);
  if (startNow <= startThen) return 0;

  let count = 0;
  const cursor = new Date(startThen);
  cursor.setDate(cursor.getDate() + 1); // start counting the day AFTER creation
  while (cursor <= startNow) {
    const dow = cursor.getDay(); // 0 = Sunday, 6 = Saturday
    if (dow !== 0 && dow !== 6) count++;
    cursor.setDate(cursor.getDate() + 1);
  }
  return count;
}

/**
 * True iff `then` is older than `days` working days before `now`.
 * Convenience wrapper around `workingDaysBetween` for the age warning.
 */
export function isOlderThanWorkingDays(
  then: Date | string,
  days: number,
  now: Date = new Date()
): boolean {
  return workingDaysBetween(then, now) >= days;
}