middleware.ts

import { NextResponse } from 'next/server'
import type { NextRequest } from 'next/server'

export async function middleware(request: NextRequest) {
  const userAgent = request.headers.get('user-agent')
  const bots = [
    'googlebot',
    'yahoo! slurp',
    'bingbot',
    'yandex',
    'baiduspider',
    'facebookexternalhit',
    'twitterbot',
    'rogerbot',
    'linkedinbot',
    'embedly',
    'quora link preview',
    'showyoubot',
    'outbrain',
    'pinterest/0.',
    'developers.google.com/+/web/snippet',
    'slackbot',
    'vkshare',
    'w3c_validator',
    'redditbot',
    'applebot',
    'whatsapp',
    'flipboard',
    'tumblr',
    'bitlybot',
    'skypeuripreview',
    'nuzzel',
    'discordbot',
    'google page speed',
    'qwantify',
    'pinterestbot',
    'bitrix link preview',
    'xing-contenttabreceiver',
    'chrome-lighthouse',
    'telegrambot',
    'integration-test' // Integration testing
  ]
  const IGNORE_EXTENSIONS = [
    '.js',
    '.css',
    '.xml',
    '.less',
    '.png',
    '.jpg',
    '.jpeg',
    '.gif',
    '.pdf',
    '.doc',
    '.txt',
    '.ico',
    '.rss',
    '.zip',
    '.mp3',
    '.rar',
    '.exe',
    '.wmv',
    '.doc',
    '.avi',
    '.ppt',
    '.mpg',
    '.mpeg',
    '.tif',
    '.wav',
    '.mov',
    '.psd',
    '.ai',
    '.xls',
    '.mp4',
    '.m4a',
    '.swf',
    '.dat',
    '.dmg',
    '.iso',
    '.flv',
    '.m4v',
    '.torrent',
    '.woff',
    '.ttf',
    '.svg',
    '.webmanifest'
  ]
  const isBot =
    userAgent && bots.some(bot => userAgent.toLowerCase().includes(bot))
  const isPrerender = request.headers.get('X-Prerender')
  const { pathname } = new URL(request.url)
  const extension = pathname.slice(((pathname.lastIndexOf('.') - 1) >>> 0) + 1)
  if (
    isPrerender ||
    !isBot ||
    (extension.length && IGNORE_EXTENSIONS.includes(extension))
  ) {
    return NextResponse.next()
  }
  // Check if request is coming from a bot
  if (isBot) {
    const newURL = `https://service.prerender.io/${request.url}`
    const newHeaders = new Headers(request.headers)
    //Do not forget to add your Prerender token as an environment variable
    newHeaders.set('X-Prerender-Token', process.env.PRERENDER_TOKEN || '')

    const res = await fetch(
      new Request(newURL, {
        headers: newHeaders,
        redirect: 'manual'
      })
    )

    const responseHeaders = new Headers(res.headers)
    responseHeaders.set('X-Redirected-From', request.url)

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

  return NextResponse.next()
}