/** UTC ISO-8601 time helpers. See PLAN.md §3.3. */

/** Current time as a UTC ISO-8601 string with Z suffix. */
export function nowIso(): string {
  return new Date().toISOString();
}

/** Parse an ISO timestamp to a Date, throwing on invalid input. */
export function parseIso(value: string): Date {
  const d = new Date(value);
  if (Number.isNaN(d.getTime())) {
    throw new Error(`Invalid ISO timestamp: ${value}`);
  }
  return d;
}

/** Format a Date as a UTC ISO-8601 string. */
export function toIso(d: Date): string {
  return d.toISOString();
}

/** Compact HH:MM label (UTC) for the autosave indicator. */
export function clockLabel(d: Date = new Date()): string {
  return d.toISOString().slice(11, 16);
}