Complex origin-pull URL rewriting

async function handleEvent(event) {
  try {
    const request = event.request;
    const url = new URL(request.url);
    let pathname = url.pathname;

    // 使用正则表达式进行路径替换，将 /a 或 /a/xxx 替换为 /path-a 或 /path-a/xxx
    if (pathname.startsWith('/a')) {
      const aPathRegex = /^\/a(\/.*)?$/;
      pathname = pathname.replace(aPathRegex, '/path-a$1');
    }

    // 路径大小写转换，直接将整个路径转换为小写
    if (pathname.startsWith('/b')) {
      pathname = pathname.toLowerCase();
    }

    url.pathname = pathname;

    // 创建新的请求
    const newRequest = new Request(url.toString(), {
      method: request.method,
      headers: request.headers,
      body: request.body,
      redirect: 'manual'
    });

    const response = await fetch(newRequest);
    return event.respondWith(response);
  } catch (err) {
    console.log(err);
  }
}

addEventListener('fetch', event => {
  handleEvent(event);
});