import { useEffect, useRef } from 'react';

/**
 * Re-run a page's data fetch whenever the Reco copilot finishes a write-tool
 * turn. The copilot panel dispatches a global ``copilot:data-changed`` window
 * event after actions such as a catalog content check, a scan, or a generation,
 * and WordPress has no route loaders to revalidate, so each page listens for the
 * event and re-fetches its own primary data.
 *
 * The latest ``onChange`` is kept in a ref so the listener is registered once
 * and callers never have to memoize their callback to avoid re-subscribing.
 *
 * @param onChange {() => void} Called every time ``copilot:data-changed`` fires.
 * @return {void}
 */
export function useCopilotDataChanged(onChange: () => void): void {
  const onChangeRef = useRef<() => void>(onChange);
  onChangeRef.current = onChange;

  useEffect(() => {
    const handleDataChanged = (): void => {
      onChangeRef.current();
    };
    window.addEventListener('copilot:data-changed', handleDataChanged);

    return () => {
      window.removeEventListener('copilot:data-changed', handleDataChanged);
    };
  }, []);
}