/** The part of a PixiJS `Ticker` the map's lifecycle needs (a fake in tests). */
export interface Startable {
  start(): void;
  stop(): void;
}

/**
 * Runs `ticker` only while the page is visible (Step 10C.9): stops it when the
 * page is hidden and starts it again when it returns. The returned cleanup (for
 * unmounting the Map) stops it and removes the listener.
 */
export function runWhileVisible(ticker: Startable, doc: Document = document): () => void {
  const sync = () => (doc.visibilityState === "hidden" ? ticker.stop() : ticker.start());
  doc.addEventListener("visibilitychange", sync);
  sync();
  return () => {
    doc.removeEventListener("visibilitychange", sync);
    ticker.stop();
  };
}