使用Cloudflare自建github代理

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'use strict'
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/**
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 * static files (404.html, sw.js, conf.js)
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 */
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const ASSET_URL = 'https://github.com/'
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// 前缀，如果自定义路由为example.com/gh/*，将PREFIX改为 '/gh/'，注意，少一个杠都会错！
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const PREFIX = '/'
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const Config = {
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    jsdelivr: 0,
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    cnpmjs: 0
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}
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/** @type {RequestInit} */
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const PREFLIGHT_INIT = {
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    status: 204,
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    headers: new Headers({
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        'access-control-allow-origin': '*',
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        'access-control-allow-methods': 'GET,POST,PUT,PATCH,TRACE,DELETE,HEAD,OPTIONS',
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        'access-control-max-age': '1728000',
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    }),
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}
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const exp1 = /^(?:https?:\/\/)?github\.com\/.+?\/.+?\/(?:releases|archive)\/.*$/i
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const exp2 = /^(?:https?:\/\/)?github\.com\/.+?\/.+?\/(?:blob|raw)\/.*$/i
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const exp3 = /^(?:https?:\/\/)?github\.com\/.+?\/.+?\/(?:info|git-).*$/i
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const exp4 = /^(?:https?:\/\/)?raw\.(?:githubusercontent|github)\.com\/.+?\/.+?\/.+?\/.+$/i
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const exp5 = /^(?:https?:\/\/)?gist\.(?:githubusercontent|github)\.com\/.+?\/.+?\/.+$/i
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/**
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 * @param {any} body
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 * @param {number} status
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 * @param {Object<string, string>} headers
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 */
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function makeRes(body, status = 200, headers = {}) {
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    headers['access-control-allow-origin'] = '*'
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    return new Response(body, {status, headers})
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}
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/**
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 * @param {string} urlStr
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 */
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function newUrl(urlStr) {
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    try {
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        return new URL(urlStr)
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    } catch (err) {
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        return null
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    }
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}
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addEventListener('fetch', e => {
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    const ret = fetchHandler(e)
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        .catch(err => makeRes('cfworker error:\n' + err.stack, 502))
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    e.respondWith(ret)
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})
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function checkUrl(u) {
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    for (let i of [exp1, exp2, exp3, exp4, exp5, ]) {
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        if (u.search(i) === 0) {
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            return true
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        }
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    }
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    return false
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}
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/**
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 * @param {FetchEvent} e
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 */
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async function fetchHandler(e) {
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    const req = e.request
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    const urlStr = req.url
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    const urlObj = new URL(urlStr)
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    let path = urlObj.searchParams.get('q')
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    if (path) {
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        return Response.redirect('https://' + urlObj.host + PREFIX + path, 301)
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    }
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    // cfworker 会把路径中的 `//` 合并成 `/`
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    path = urlObj.href.substr(urlObj.origin.length + PREFIX.length).replace(/^https?:\/+/, 'https://')
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    if (path.search(exp1) === 0 || path.search(exp5) === 0 || !Config.cnpmjs && (path.search(exp3) === 0 || path.search(exp4) === 0)) {
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        return httpHandler(req, path)
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    } else if (path.search(exp2) === 0) {
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        if (Config.jsdelivr) {
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            const newUrl = path.replace('/blob/', '@').replace(/^(?:https?:\/\/)?github\.com/, 'https://cdn.jsdelivr.net/gh')
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            return Response.redirect(newUrl, 302)
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        } else {
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            path = path.replace('/blob/', '/raw/')
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            return httpHandler(req, path)
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        }
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    } else if (path.search(exp3) === 0) {
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        const newUrl = path.replace(/^(?:https?:\/\/)?github\.com/, 'https://github.com.cnpmjs.org')
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        return Response.redirect(newUrl, 302)
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    } else if (path.search(exp4) === 0) {
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        const newUrl = path.replace(/(?<=com\/.+?\/.+?)\/(.+?\/)/, '@$1').replace(/^(?:https?:\/\/)?raw\.(?:githubusercontent|github)\.com/, 'https://cdn.jsdelivr.net/gh')
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        return Response.redirect(newUrl, 302)
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    } else {
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        return fetch(ASSET_URL + path)
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    }
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}
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/**
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 * @param {Request} req
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 * @param {string} pathname
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 */
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function httpHandler(req, pathname) {
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    const reqHdrRaw = req.headers
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    // preflight
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    if (req.method === 'OPTIONS' &&
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        reqHdrRaw.has('access-control-request-headers')
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    ) {
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        return new Response(null, PREFLIGHT_INIT)
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    }
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    const reqHdrNew = new Headers(reqHdrRaw)
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    let urlStr = pathname
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    if (urlStr.startsWith('github')) {
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        urlStr = 'https://' + urlStr
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    }
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    const urlObj = newUrl(urlStr)
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    /** @type {RequestInit} */
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    const reqInit = {
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        method: req.method,
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        headers: reqHdrNew,
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        redirect: 'manual',
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        body: req.body
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    }
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    return proxy(urlObj, reqInit)
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}
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/**
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 *
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 * @param {URL} urlObj
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 * @param {RequestInit} reqInit
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 */
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async function proxy(urlObj, reqInit) {
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    const res = await fetch(urlObj.href, reqInit)
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    const resHdrOld = res.headers
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    const resHdrNew = new Headers(resHdrOld)
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    const status = res.status
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    if (resHdrNew.has('location')) {
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        let _location = resHdrNew.get('location')
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        if (checkUrl(_location))
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            resHdrNew.set('location', PREFIX + _location)
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        else {
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            reqInit.redirect = 'follow'
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            return proxy(newUrl(_location), reqInit)
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        }
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    }
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    resHdrNew.set('access-control-expose-headers', '*')
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    resHdrNew.set('access-control-allow-origin', '*')
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    resHdrNew.delete('content-security-policy')
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    resHdrNew.delete('content-security-policy-report-only')
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    resHdrNew.delete('clear-site-data')
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    return new Response(res.body, {
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        status,
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        headers: resHdrNew,
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    })
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}