function uint8ArrayToHex(arr) {
  return Array.prototype.map.call(arr, (x) => (('0' + x.toString(16)).slice(-2))).join('');
}

// sha256 签名摘要
async function sha256(message) {
  const msgBuffer = new TextEncoder().encode(message);
  const hashBuffer = await crypto.subtle.digest('SHA-256', msgBuffer);

  return uint8ArrayToHex(new Uint8Array(hashBuffer));
}

async function fetchContent(event, cacheKey) {
  const cache = caches.default;

  // 缓存没有命中，回源并使用缓存
  const response = await fetch(event.request);

  // 在响应头添加 Cahe-Control，设置缓存时长
  response.headers.set('Cache-Control', 's-maxage=10');
  event.waitUntil(cache.put(cacheKey, response.clone()));

  // 未命中缓存，设置响应头标识
  response.headers.append('x-edgefunctions-cache', 'miss');

  return response;
}

async function handleRequest(event) {
  const request = event.request;
  const body = await request.clone().text();

  // // 根据 request body 计算 hash
  const hash = await sha256(body);

  // request body 计算的 hash 值作为 cacheKey 的一部分
  const cacheKey = `${request.url}${hash}`;

  const cache = caches.default;

  try {
    // 获取关联的缓存 Response
    let response = await cache.match(cacheKey);

    if (!response) {
        return fetchContent(event, cacheKey);
    }

    // 命中缓存，设置响应头标识
    response.headers.append('x-edgefunctions-cache', 'hit');

    return response;
  } catch (error) {
    await cache.delete(cacheKey);
    // 缓存过期或不存在，重新获取远程资源
    return fetchContent(event, cacheKey);
  }

  return response;
}

addEventListener('fetch', (event) => {
  try {
    const request = event.request;
    // 处理 POST 请求
    if (request.method.toUpperCase() === 'POST') {
      return event.respondWith(handleRequest(event));
    }
    // 非post 请求
    return event.respondWith(fetch(request));
  } catch (e) {
    return event.respondWith(new Response('Error thrown ' + e.message));
  }
});