import {
  addMonths,
  getDate,
  getYear,
  getMonth,
  format,
} from "date-fns";
import { de } from "date-fns/locale";

/**
 * Der Notdienst-Plan wird immer für den nächsten Monat erstellt.
 * Nach dem 26. des aktuellen Monats ist der Plan gesperrt.
 */
const LOCK_DAY = 26;

export function getTargetMonthData(now = new Date()) {
  const currentDay = getDate(now);
  const nextMonthDate = addMonths(now, 1);
  const targetYear = getYear(nextMonthDate);
  const targetMonth = getMonth(nextMonthDate) + 1; // 1-12

  // Sperre aktiv, sobald der aktuelle Tag (im aktuellen Monat) > LOCK_DAY ist.
  const isLocked = currentDay > LOCK_DAY;

  return {
    targetYear,
    targetMonth,
    isLocked,
    monthName: format(nextMonthDate, "MMMM yyyy", { locale: de }),
  };
}

export function getWorkingDaysOfMonth(year: number, month: number) {
  const start = new Date(Date.UTC(year, month - 1, 1));
  const end = new Date(Date.UTC(year, month, 0)); // last day of month

  const days: Date[] = [];
  const current = new Date(start);
  while (current <= end) {
    const dayOfWeek = current.getUTCDay(); // 0 is Sunday, 6 is Saturday
    if (dayOfWeek !== 0 && dayOfWeek !== 6) {
      days.push(new Date(current));
    }
    current.setUTCDate(current.getUTCDate() + 1);
  }
  return days;
}

export function formatDateKey(date: Date) {
  return format(date, "yyyy-MM-dd");
}

export function formatUtcDateKey(date: Date) {
  const yyyy = date.getUTCFullYear();
  const mm = String(date.getUTCMonth() + 1).padStart(2, "0");
  const dd = String(date.getUTCDate()).padStart(2, "0");
  return `${yyyy}-${mm}-${dd}`;
}