import { useEffect, useRef } from 'react';

// Shared is-mounted guard for async callbacks (#578). A monotonic `seqRef` drops a STALE response
// (an older request resolving after a newer one) but says nothing about whether the component is
// still there: a fetch that resolves after unmount still matches the latest seq and still calls
// setState. Read `ref.current` in every async callback alongside the seq check.
//
// The flag is (re-)armed inside the effect rather than only at `useRef` init so a StrictMode
// double-invoke — mount, unmount, remount on the same instance — leaves it true.
export function useIsMountedRef(): { readonly current: boolean } {
  const ref = useRef(true);

  useEffect(() => {
    ref.current = true;
    return () => {
      ref.current = false;
    };
  }, []);

  return ref;
}