"use client";

import { useEffect, useRef } from "react";

/**
 * Track the previous value of a prop. Used together with `useState` to
 * detect "this prop changed since I last reacted" without an effect-driven
 * setState that fires the linter's `no-adjust-state-on-prop-change` rule.
 *
 * Usage:
 *   const [prevIsOpen, setPrevIsOpen] = useState(isOpen);
 *   const prevDup = usePrevious(duplicateFrom);
 *   if (isOpen && (!prevIsOpen || prevDup !== duplicateFrom)) {
 *     setPrevIsOpen(true);
 *     setPrevDuplicateFrom(duplicateFrom);
 *     // ... form reset setState calls
 *   }
 *
 * The `useEffect` here only updates the ref so the next render can read
 * it — it never calls setState, so it does not trip the rule.
 */
export function usePrevious<T>(value: T): T | undefined {
  const ref = useRef<T | undefined>(undefined);
  useEffect(() => {
    ref.current = value;
  });
  return ref.current;
}