export function toDateStr(d: Date): string {
  const y = d.getFullYear();
  const m = String(d.getMonth() + 1).padStart(2, '0');
  const day = String(d.getDate()).padStart(2, '0');
  return `${y}-${m}-${day}`;
}

function parse(dateStr: string): Date {
  const [y, m, d] = dateStr.split('-').map(Number);
  return new Date(y, m - 1, d);
}

export function getWeekRange(dateStr: string): { start: string; end: string } {
  const d = parse(dateStr);
  const day = (d.getDay() + 6) % 7; // Mon=0 .. Sun=6
  const monday = new Date(d);
  monday.setDate(d.getDate() - day);
  const sunday = new Date(monday);
  sunday.setDate(monday.getDate() + 6);
  return { start: toDateStr(monday), end: toDateStr(sunday) };
}

export function getMonthRange(dateStr: string): { start: string; end: string } {
  const d = parse(dateStr);
  const start = new Date(d.getFullYear(), d.getMonth(), 1);
  const end = new Date(d.getFullYear(), d.getMonth() + 1, 0);
  return { start: toDateStr(start), end: toDateStr(end) };
}

export function eachDayInRange(start: string, end: string): string[] {
  const out: string[] = [];
  const cur = parse(start);
  const last = parse(end);
  while (cur <= last) {
    out.push(toDateStr(cur));
    cur.setDate(cur.getDate() + 1);
  }
  return out;
}