/** Local-date helpers for daily strips (no UTC drift). */

export function isoDate(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}`;
}

/** Last `n` calendar days ending at `end`, oldest first. */
export function lastNDays(end: Date, n: number): string[] {
  const days: string[] = [];
  for (let i = n - 1; i >= 0; i -= 1) {
    const d = new Date(end.getFullYear(), end.getMonth(), end.getDate() - i);
    days.push(isoDate(d));
  }
  return days;
}

/**
 * Local Monday–Sunday calendar week containing `anchor`.
 * Week points on Home use this window (not a rolling 7 ending today).
 */
export function mondaySundayWeek(anchor: Date = new Date()): string[] {
  const local = new Date(anchor.getFullYear(), anchor.getMonth(), anchor.getDate());
  const day = local.getDay(); // 0 Sun … 6 Sat
  const mondayOffset = day === 0 ? -6 : 1 - day;
  const monday = new Date(local.getFullYear(), local.getMonth(), local.getDate() + mondayOffset);
  return lastNDays(new Date(monday.getFullYear(), monday.getMonth(), monday.getDate() + 6), 7);
}

export function entryLocalDate(ts: string): string {
  return isoDate(new Date(ts));
}