// Resume rewind (per-user server setting): how many seconds before the
// saved position the audiobook/podcast player starts. Applied on
// open-resume AND again on every genuine unpause — each event rewinds
// once from where playback currently sits, never stacked. Pure math;
// the Alpine component owns when to call it (the play-event suppress
// flag keeps restore-autoplay and track switches from double-firing).

// applyResumeRewind maps a position back by the rewind amount, clamped
// to the start of the book.
export function applyResumeRewind(positionSeconds: number, rewindSeconds: number): number {
  if (!Number.isFinite(positionSeconds)) return 0;
  if (!Number.isFinite(rewindSeconds) || rewindSeconds <= 0) return Math.max(0, positionSeconds);
  return Math.max(0, positionSeconds - rewindSeconds);
}

// normalizeResumeRewind gates the server payload value to the setting's
// allow-list (0/5/10) — anything else means off.
export function normalizeResumeRewind(value: unknown): number {
  const n = Number(value);
  return n === 5 || n === 10 ? n : 0;
}