"use client"

import { useEffect } from "react"

/**
 * Adds a beforeunload warning when the form has unsaved changes.
 * Pass `isDirty` — set to true as soon as any field changes.
 */
export function useWarnUnsaved(isDirty: boolean) {
  useEffect(() => {
    if (!isDirty) return
    function handler(e: BeforeUnloadEvent) {
      e.preventDefault()
    }
    window.addEventListener("beforeunload", handler)
    return () => window.removeEventListener("beforeunload", handler)
  }, [isDirty])
}