'use strict'

const hub_host = 'registry-1.docker.io'
const auth_url = 'https://auth.docker.io'
const workers_url = 'https://你的域名'
//const home_page_url = '远程html链接'

/** @type {RequestInit} */
const PREFLIGHT_INIT = {
    status: 204,
    headers: new Headers({
        'access-control-allow-origin': '*',
        'access-control-allow-methods': 'GET,POST,PUT,PATCH,TRACE,DELETE,HEAD,OPTIONS',
        'access-control-max-age': '1728000',
    }),
}

/**
 * @param {any} body
 * @param {number} status
 * @param {Object<string, string>} headers
 */
function makeRes(body, status = 200, headers = {}) {
    headers['access-control-allow-origin'] = '*'
    return new Response(body, {status, headers})
}


/**
 * @param {string} urlStr
 */
function newUrl(urlStr) {
    try {
        return new URL(urlStr)
    } catch (err) {
        return null
    }
}


addEventListener('fetch', e => {
    const ret = fetchHandler(e)
        .catch(err => makeRes('cfworker error:\n' + err.stack, 502))
    e.respondWith(ret)
})


/**
 * @param {FetchEvent} e
 */
async function fetchHandler(e) {
    const getReqHeader = (key) => e.request.headers.get(key);

    let url = new URL(e.request.url);

    if (url.pathname === '/') {
        // Fetch and return the home page HTML content
        //return fetch(home_page_url);
        return new Response(indexHtml, {
            headers: {
              'Content-Type': 'text/html'
            }
          });
    }

    if (url.pathname === '/token') {
        let token_parameter = {
            headers: {
                'Host': 'auth.docker.io',
                'User-Agent': getReqHeader("User-Agent"),
                'Accept': getReqHeader("Accept"),
                'Accept-Language': getReqHeader("Accept-Language"),
                'Accept-Encoding': getReqHeader("Accept-Encoding"),
                'Connection': 'keep-alive',
                'Cache-Control': 'max-age=0'
            }
        };
        let token_url = auth_url + url.pathname + url.search
        return fetch(new Request(token_url, e.request), token_parameter)
    }

    url.hostname = hub_host;

    let parameter = {
        headers: {
            'Host': hub_host,
            'User-Agent': getReqHeader("User-Agent"),
            'Accept': getReqHeader("Accept"),
            'Accept-Language': getReqHeader("Accept-Language"),
            'Accept-Encoding': getReqHeader("Accept-Encoding"),
            'Connection': 'keep-alive',
            'Cache-Control': 'max-age=0'
        },
        cacheTtl: 3600
    };

    if (e.request.headers.has("Authorization")) {
        parameter.headers.Authorization = getReqHeader("Authorization");
    }

    let original_response = await fetch(new Request(url, e.request), parameter)
    let original_response_clone = original_response.clone();
    let original_text = original_response_clone.body;
    let response_headers = original_response.headers;
    let new_response_headers = new Headers(response_headers);
    let status = original_response.status;

    if (new_response_headers.get("Www-Authenticate")) {
        let auth = new_response_headers.get("Www-Authenticate");
        let re = new RegExp(auth_url, 'g');
        new_response_headers.set("Www-Authenticate", response_headers.get("Www-Authenticate").replace(re, workers_url));
    }

    if (new_response_headers.get("Location")) {
        return httpHandler(e.request, new_response_headers.get("Location"))
    }

    let response = new Response(original_text, {
        status,
        headers: new_response_headers
    })
    return response;

}


/**
 * @param {Request} req
 * @param {string} pathname
 */
function httpHandler(req, pathname) {
    const reqHdrRaw = req.headers

    // preflight
    if (req.method === 'OPTIONS' &&
        reqHdrRaw.has('access-control-request-headers')
    ) {
        return new Response(null, PREFLIGHT_INIT)
    }

    let rawLen = ''

    const reqHdrNew = new Headers(reqHdrRaw)

    const refer = reqHdrNew.get('referer')

    let urlStr = pathname

    const urlObj = newUrl(urlStr)

    /** @type {RequestInit} */
    const reqInit = {
        method: req.method,
        headers: reqHdrNew,
        redirect: 'follow',
        body: req.body
    }
    return proxy(urlObj, reqInit, rawLen, 0)
}


/**
 *
 * @param {URL} urlObj
 * @param {RequestInit} reqInit
 */
async function proxy(urlObj, reqInit, rawLen) {
    const res = await fetch(urlObj.href, reqInit)
    const resHdrOld = res.headers
    const resHdrNew = new Headers(resHdrOld)

    // verify
    if (rawLen) {
        const newLen = resHdrOld.get('content-length') || ''
        const badLen = (rawLen !== newLen)

        if (badLen) {
            return makeRes(res.body, 400, {
                '--error': `bad len: ${newLen}, except: ${rawLen}`,
                'access-control-expose-headers': '--error',
            })
        }
    }
    const status = res.status
    resHdrNew.set('access-control-expose-headers', '*')
    resHdrNew.set('access-control-allow-origin', '*')
    resHdrNew.set('Cache-Control', 'max-age=1500')

    resHdrNew.delete('content-security-policy')
    resHdrNew.delete('content-security-policy-report-only')
    resHdrNew.delete('clear-site-data')

    return new Response(res.body, {
        status,
        headers: resHdrNew
    })
}

const indexHtml = `
<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>在Linux上设置Docker Hub Registry Mirror</title>
  <style>
    body {
      max-width: 800px;
      margin: 0 auto;
      padding: 20px;
      line-height: 1.6;
      color: #333;
      background-color: #f7f7f7;
    }

    h1 {
      color: #0066cc;
      margin-bottom: 30px;
    }

    h2 {
      color: #0066cc;
      margin-top: 40px;
    }

    pre {
      background-color: #fff;
      padding: 15px;
      padding-top: 48px;
      overflow-x: auto;
      border-radius: 8px;
      box-shadow: 0 4px 14px rgba(0, 0, 0, 0.1);
    }

    ol {
      margin-top: 20px;
      padding-left: 20px;
    }

    li {
      margin-bottom: 10px;
    }

    code {
      font-family: Consolas, monospace;
      background-color: #fff;
      padding: 2px 4px;
      border-radius: 3px;
    }

    .container {
      background-color: #fff;
      padding: 30px;
      border-radius: 8px;
      box-shadow: 0 4px 14px rgba(0, 0, 0, 0.1);
    }

    .copy-btn {
      position: absolute;
      top: 10px;
      right: 10px;
      padding: 4px 10px;
      background-color: #0066cc;
      color: #fff;
      border: none;
      border-radius: 4px;
      cursor: pointer;
      font-size: 14px;
      transition: background-color 0.3s;
    }

    .copy-btn:hover {
      background-color: #0052a3af;
    }

    .code-wrapper {
      position: relative;
    }
  </style>
</head>

<body>
  <div class="container">
    <h1>在Linux上设置Docker Hub Registry Mirror</h1>
    <p>为了加速Docker镜像的下载速度,你可以设置Docker Hub的registry mirror</p>

    <h2>设置步骤</h2>
    <ol>
      <li>创建或编辑<code>/etc/docker/daemon.json</code>文件,添加以下内容:</li>
    </ol>
    <div class="code-wrapper">
      <pre>
echo '{"registry-mirrors": ["${workers_url}"]}' | sudo tee /etc/docker/daemon.json > /dev/null</pre>
      <button class="copy-btn" onclick="copyCode(this)">复制</button>
    </div>
    <ol start="2">
      <li>重启Docker服务:</li>
    </ol>
    <div class="code-wrapper">
      <pre>sudo systemctl restart docker</pre>
      <button class="copy-btn" onclick="copyCode(this)">复制</button>
    </div>

    <p>设置完成后,Docker将会从您配置的registry mirror中拉取镜像,加速镜像下载过程。</p>
  </div>

  <script>
    function copyCode(btn) {
      const pre = btn.previousElementSibling;
      const code = pre.innerText;
      navigator.clipboard.writeText(code).then(function () {
        btn.innerText = '已复制';
        setTimeout(function () {
          btn.innerText = '复制';
        }, 2000);
      }, function () {
        alert('复制失败,请手动复制。');
      });
    }
  </script>
</body>

</html>
`