/** Parse "m:ss" or "h:mm:ss" string to total seconds. Returns 0 on failure. */
export function parseDuration(duration?: string): number {
  if (!duration) return 0;
  const parts = duration.split(":").map(Number);
  if (parts.some(isNaN)) return 0;
  if (parts.length === 3) return parts[0] * 3600 + parts[1] * 60 + parts[2];
  if (parts.length === 2) return parts[0] * 60 + parts[1];
  return parts[0] || 0;
}

/** Convert seconds to ISO 8601 duration string: "PT3M42S" */
export function toISO8601Duration(seconds: number): string {
  if (seconds <= 0) return "";
  const h = Math.floor(seconds / 3600);
  const m = Math.floor((seconds % 3600) / 60);
  const s = seconds % 60;
  let result = "PT";
  if (h > 0) result += `${h}H`;
  if (m > 0) result += `${m}M`;
  if (s > 0) result += `${s}S`;
  return result;
}