text: const fs = require('fs')
  const path = require('path')
  const LRU = require('lru-cache')
  const express = require('express')
  const favicon = require('serve-favicon')
  const cookieParser = require('cookie-parser');
  const compression = require('compression')
  const microcache = require('route-cache')
  const resolve = file => path.resolve(__dirname, file)
  const { createBundleRenderer } = require('vue-server-renderer')
  
  const isProd = process.env.NODE_ENV === 'production'
  const useMicroCache = process.env.MICRO_CACHE !== 'false'
  const serverInfo =
    `express/${require('express/package.json').version} ` +
    `vue-server-renderer/${require('vue-server-renderer/package.json').version}`
  
  const app = express()
  
  function createRenderer (bundle, options) {
    // https://github.com/vuejs/vue/blob/dev/packages/vue-server-renderer/README.md#why-use-bundlerenderer
    return createBundleRenderer(bundle, Object.assign(options, {
      // for component caching
      cache: LRU({
        max: 1000,
        maxAge: 1000 * 60 * 15
      }),
      // this is only needed when vue-server-renderer is npm-linked
      basedir: resolve('./dist'),
      // recommended for performance
      runInNewContext: false
    }))
  }
  
  let renderer
  let readyPromise
  const templatePath = resolve('./src/index.html')
  if (isProd) {
    // In production: create server renderer using template and built server bundle.
    // The server bundle is generated by vue-ssr-webpack-plugin.
    const template = fs.readFileSync(templatePath, 'utf-8')
    const bundle = require('./dist/vue-ssr-server-bundle.json')
    // The client manifests are optional, but it allows the renderer
    // to automatically infer preload/prefetch links and directly add <script>
    // tags for any async chunks used during render, avoiding waterfall requests.
    const clientManifest = require('./dist/vue-ssr-client-manifest.json')
    renderer = createRenderer(bundle, {
      template,
      clientManifest
    })
  } else {
    // In development: setup the dev server with watch and hot-reload,
    // and create a new renderer on bundle / index template update.
    readyPromise = require('./build/setup-dev-server')(
      app,
      templatePath,
      (bundle, options) => {
        renderer = createRenderer(bundle, options)
      }
    )
  }
  
  const serve = (path, cache) => express.static(resolve(path), {
    maxAge: cache && isProd ? 1000 * 60 * 60 * 24 * 30 : 0
  })
  
  app.use(compression({ threshold: 0 }))
  app.use(cookieParser())
  app.use(favicon('./public/favicon.png'))
  app.use('/dist', serve('./dist', true))
  app.use('/public', serve('./public', true))
  // app.use('/manifest.json', serve('./manifest.json', true))
  // app.use('/service-worker.js', serve('./dist/service-worker.js'))
  
  // since this app has no user-specific content, every page is micro-cacheable.
  // if your app involves user-specific content, you need to implement custom
  // logic to determine whether a request is cacheable based on its url and
  // headers.
  // 1-second microcache.
  // https://www.nginx.com/blog/benefits-of-microcaching-nginx/
  app.use(microcache.cacheSeconds(1, req => useMicroCache && req.originalUrl))
  
  function render (req, res) {
    const s = Date.now()
  
    res.setHeader("Content-Type", "text/html")
    res.setHeader("Server", serverInfo)
  
    const handleError = err => {
      if (err.url) {
        res.redirect(err.url)
      } else if(err.code === 404) {
        res.status(404).send('404 | Page Not Found')
      } else {
        // Render Error Page or Redirect
        res.status(500).send('500 | Internal Server Error')
        console.error(`error during render : ${req.url}`)
        console.error(err.stack)
      }
    }
  
    const context = {
      title: 'Vue SSR', // default title
      url: req.url,
      cookies: req.cookies
    }
    renderer.renderToString(context, (err, html) => {
      if (err) {
        return handleError(err)
      }
      res.send(html)
      if (!isProd) {
        console.log(`whole request: ${Date.now() - s}ms`)
      }
    })
  }
  
  app.get('*', isProd ? render : (req, res) => {
    readyPromise.then(() => render(req, res))
  })
  
  const port = process.env.PORT || 8080
  app.listen(port, () => {
    console.log(`server started at localhost:${port}`)
  })
  