const CH = 'smart-auth';
const LS_KEY = 'smart_logout_ping';

/** 当前标签页主动登出时通知其它标签 */
export function broadcastLogout(): void {
  if (typeof window === 'undefined') {
    return;
  }
  try {
    if (typeof BroadcastChannel !== 'undefined') {
      const bc = new BroadcastChannel(CH);
      bc.postMessage({ type: 'logout', t: Date.now() });
      bc.close();
    }
  } catch {
    /* ignore */
  }
  try {
    localStorage.setItem(LS_KEY, String(Date.now()));
  } catch {
    /* ignore */
  }
}

export type LogoutListener = () => void;

/** 其它标签登出时回调（需在客户端挂载一次） */
export function subscribeRemoteLogout(onLogout: LogoutListener): () => void {
  if (typeof window === 'undefined') {
    return () => {};
  }

  let bc: BroadcastChannel | null = null;
  try {
    if (typeof BroadcastChannel !== 'undefined') {
      bc = new BroadcastChannel(CH);
      bc.onmessage = (ev: MessageEvent<{ type?: string }>) => {
        if (ev.data?.type === 'logout') {
          onLogout();
        }
      };
    }
  } catch {
    bc = null;
  }

  const onStorage = (e: StorageEvent) => {
    if (e.key === LS_KEY && e.newValue) {
      onLogout();
    }
  };
  window.addEventListener('storage', onStorage);

  return () => {
    window.removeEventListener('storage', onStorage);
    bc?.close();
  };
}