Netlify Edge Functions: Geolocation example

geolocation.ts

import type { Context } from "netlify:edge";
import {
  Cookie,
  setCookie,
} from "https://deno.land/std@0.78.0/http/cookie.ts";
import { CookieJar } from "https://deno.land/x/cookies/mod.ts";

let bots = [
  // generic
  'bot', // googlebot, bingbot, telegrambot, twitterbot, yandexbot, etc.
  'check',
  'cloud', // cloudflare, cloudinary, etc.
  'crawler',
  'download',
  'monitor', // monitor & monitoring
  'preview', // skypeuripreview, bingpreview, yahoo link preview, etc.
  'scan',
  'spider', // baiduspider, 360spider, screaming frog seo spider, etc.

  // search engines
  'google',
  'qwantify',
  'yahoo',

  // aggregators, messengers and social networks
  'facebookexternalhit',
  'flipboard',
  'tumblr',
  'vkshare',
  'whatsapp',

  // downloaders
  'curl',
  'perl',
  'python',
  'wget',

  // high activity scanners
  'heritrix',
  'ia_archiver',
];
const createRegex = () => new RegExp(`(${bots.join('|')})`, 'i');
let isBotRegex = createRegex();

const isBot = (userAgent: string) => isBotRegex.test(userAgent);
const ERROR_COUNTRY = 'error'
const COUNTRY_COOKIE_NAME = '_geoCountry'
const COUNTRY_OVERRIDE_PARAM = '_country'

const URLS = {
  canada: 'https://canada.com',
  default: 'https://us.com',
}

function getUrlToRedirectTo(countryCode: string, currentUrl?: URL) {
  const region = Deno.env.get('REGION') || 'default' 

  if (countryCode.toUpperCase() === 'CA' && region !== 'canada') {
    return appendPathToAnotherUrl(URLS['canada'], currentUrl)
  }
  
  if (countryCode.toUpperCase() !== 'CA' && region === 'canada') {
    return appendPathToAnotherUrl(URLS['default'], currentUrl)
  }

  return null
}

function appendPathToAnotherUrl(url: string, sourceUrl?: URL) {
  if (!sourceUrl) {
    return url
  }

  const target = new URL(url)
  target.pathname = sourceUrl.pathname
  target.search = sourceUrl.search

  target.searchParams.delete(COUNTRY_OVERRIDE_PARAM)

  return target.toString()
}

export default async (request: Request, context: Context): Promise<Response> => {
  const region = Deno.env.get('REGION') || 'default'
  const url = new URL(request.url);
  const overrideCountry = url.searchParams.get(COUNTRY_OVERRIDE_PARAM)
  let countryCode = overrideCountry || context.geo?.country?.code || ERROR_COUNTRY;
  const countryName = context.geo?.country?.name || "somewhere in the world";
  const userAgent = request.headers.get('user-agent') || ''
  const isABot = isBot(userAgent)
  const countryCodeFromCookie = await context.cookies.get(COUNTRY_COOKIE_NAME);

  context.log({countryCode, overrideCountry, region, isABot })

  // Skip API requests?
  if (url.pathname.includes('/api/')) {
    return context.next()
  }

  if (countryCode === ERROR_COUNTRY) {
    context.log('Failed to resolve country')

    return context.next()
  }

  // Return early for bots
  if (isABot) {
    return context.next()
  }

  // Set country from cookie if we are not overriding
  if (countryCodeFromCookie && !overrideCountry) {
    countryCode = countryCodeFromCookie
  }

  // @todo This causes Type error: Headers are immutable
  // if (countryCodeFromCookie !== countryCode) {
  //   context.log('Setting cookie to: ' + countryCode)
  //     const response = await context.next();

  //     context.cookies.set({
  //       name: COUNTRY_COOKIE_NAME,
  //       value: countryCode,
  //     });

  //   return response;
  // }

  const result = {
    overrideCountry,
    country: countryCode,
  }

  context.log(isABot, region, result)


  const redirectTo = getUrlToRedirectTo(countryCode, url)

  if (!redirectTo) {
    return context.next();
  }

  return Response.redirect(redirectTo, 301)
}