'use client';

import {useEffect} from 'react';
import {getHistoryTransition} from './editor-behavior';

const historyIndexKey = '__wafEditorIndex';

export function UnsavedChanges({dirty}: {dirty: boolean}) {
  useEffect(() => {
    if (!dirty) return;
    const initialState = history.state && typeof history.state === 'object' ? history.state : {};
    let currentIndex = Number.isInteger(initialState[historyIndexKey]) ? initialState[historyIndexKey] as number : 0;
    const currentUrl = window.location.pathname + window.location.search + window.location.hash;
    history.replaceState({...initialState, [historyIndexKey]: currentIndex}, '');
    const originalPushState = history.pushState.bind(history);
    const originalReplaceState = history.replaceState.bind(history);
    history.pushState = (data, unused, url) => { currentIndex++; originalPushState({...data, [historyIndexKey]: currentIndex}, unused, url); };
    history.replaceState = (data, unused, url) => originalReplaceState({...data, [historyIndexKey]: currentIndex}, unused, url);
    let restoring = false;
    const handler = (event: BeforeUnloadEvent) => { if (dirty) event.preventDefault(); };
    const clickHandler = (event: MouseEvent) => {
      if (!dirty || event.defaultPrevented || event.button !== 0 || event.metaKey || event.ctrlKey || event.shiftKey || event.altKey) return;
      const link = (event.target as Element | null)?.closest('a[href]') as HTMLAnchorElement | null;
      if (!link || link.target === '_blank' || new URL(link.href, window.location.href).origin !== window.location.origin) return;
      if (!window.confirm('存在未保存的更改，确定离开吗？')) event.preventDefault();
    };
    const popstateHandler = (event: PopStateEvent) => {
      const hasTargetIndex = Number.isInteger(event.state?.[historyIndexKey]);
      const targetIndex = hasTargetIndex ? event.state[historyIndexKey] as number : currentIndex;
      if (restoring) { restoring = false; currentIndex = targetIndex; return; }
      if (window.confirm('存在未保存的更改，确定离开吗？')) { currentIndex = targetIndex; return; }
      if (!hasTargetIndex) { originalPushState({...initialState, [historyIndexKey]: currentIndex}, '', currentUrl); return; }
      restoring = true;
      history.go(getHistoryTransition(currentIndex, targetIndex).restoreDelta);
    };
    window.addEventListener('beforeunload', handler);
    document.addEventListener('click', clickHandler, true);
    window.addEventListener('popstate', popstateHandler);
    return () => { history.pushState = originalPushState; history.replaceState = originalReplaceState; window.removeEventListener('beforeunload', handler); document.removeEventListener('click', clickHandler, true); window.removeEventListener('popstate', popstateHandler); };
  }, [dirty]);
  return null;
}