// Small shared coercers for DTO fields that arrive as strings from JSON.
// Distinguishing "field absent" (undefined -> leave unchanged) from
// "field cleared" (null/"" -> set null) matters for PATCH semantics.

export function toDate(v?: string | null): Date | null | undefined {
  if (v === undefined) return undefined;
  if (v === "" || v === null) return null;
  const d = new Date(v);
  return isNaN(d.getTime()) ? undefined : d;
}