addEventListener('fetch', event => {
  event.passThroughOnException();
  event.respondWith(handleRequest(event.request));
});

async function handleRequest(request) {
  const url = new URL(request.url);
  const fileName = url.searchParams.get('fileName');

  const response = await fetch(request);

  // 判断响应状态码和 search 参数
  if (response.status !== 200 || !fileName) {
    return response;
  }

  // 修改 Content-Disposition 响应头
  response.headers.append('Content-Disposition', `attachment; filename="${fileName}"`);
  return response;
}