// Conversions between the compact "YYYYMMDD" date keys used throughout the
// export data (e.g. `DisplaySummary.uploadDate`) and the "YYYY-MM-DD" strings
// that `<input type="date">` expects. Shared by the charts FilterBar and the
// search date filter.

// "20260513" -> "2026-05-13" for <input type="date">. Returns "" for anything
// that isn't a well-formed 8-digit key.
export function ymdToInput(ymd?: string): string {
  if (!ymd || !/^\d{8}$/.test(ymd)) return "";
  return `${ymd.slice(0, 4)}-${ymd.slice(4, 6)}-${ymd.slice(6, 8)}`;
}

// "2026-05-13" -> "20260513". Returns undefined when the input is empty or
// malformed (e.g. a cleared date input).
export function inputToYmd(v: string): string | undefined {
  const m = v.match(/^(\d{4})-(\d{2})-(\d{2})$/);
  return m ? `${m[1]}${m[2]}${m[3]}` : undefined;
}