export type ShiftKey = 'manha' | 'tarde' | 'noite';

export const SHIFTS: Record<ShiftKey, { startHour: number; endHour: number }> = {
  manha: { startHour: 6, endHour: 14 },
  tarde: { startHour: 14, endHour: 22 },
  noite: { startHour: 22, endHour: 6 },
};

/** Given a shift and a day (Date at local midnight), returns [from, to). */
export function shiftWindow(shift: ShiftKey, day: Date): { from: Date; to: Date } {
  const s = SHIFTS[shift];
  const from = new Date(day);
  from.setHours(s.startHour, 0, 0, 0);
  const to = new Date(day);
  if (s.endHour <= s.startHour) to.setDate(to.getDate() + 1); // noite crosses midnight
  to.setHours(s.endHour, 0, 0, 0);
  return { from, to };
}

/** "Hoje" = start of local day up to now. `now` injected for testability. */
export function todayWindow(now: Date): { from: Date; to: Date } {
  const from = new Date(now);
  from.setHours(0, 0, 0, 0);
  return { from, to: now };
}