tomas-chudjak/facebook-share-thumbnails-nuxt-spa-aws-cloudfront.js

## facebook-share-thumbnails-nuxt-spa-aws-cloudfront.js
'use strict';

import { createRequire } from 'module';
const require = createRequire(import.meta.url);
const https = require('https');

export const handler = async(event, context, callback) => {

  let content = "";
  let userAgent = false;

  const request = event.Records[0].cf.request;
  const headers = request.headers;
  if(headers){
    userAgent = request.headers['user-agent'];
  }

  // NOTE: Identify the facebook share request by user-agent header
  // I added few more, but 'facebookexternalhit' is the most important one
  let prerender = /Facebot|FacebookBot|facebookexternalhit|twitterbot/i.test(userAgent[0].value);

  if(prerender){
    let path = request.uri;
    let options = {
      // NOTE: link to your API endpoint
      hostname: "<api-endpoint>",
      path: path,
      headers: {
        "Content-Type": "application/json",
      }
    }

    const initialResponse = await new Promise((resolve, reject) => {
      const req = https.get(options, function(res) {
        res.on('data', chunk => {
          content += chunk;
        });
        res.on('end', () => {
          resolve({
            statusCode: 200,
            body: content.toString()
          });
        });
      });

      req.on('error', (e) => {
        reject({
          statusCode: 400,
          body: e
        });
      });
    });

    // Our API returns the meta data in JSON format so we need to parse it
    let data = JSON.parse(initialResponse.body);

    // NOTE: We need to get the full url of the page we are sharing
    let ogUrl = `https://${headers['host'][0]['value']}${request.uri}`

    // NOTE: We need to generate the HTML code with the meta data
    // Our meta keys fetched from API are:
    // metaTitle - title of the page
    // metaDescription - description of the page
    // metaImageUrl - image of the page
    // if any of these are different, don't forget to change them in the code below (f.e. og:locale)
    // The fb:app_id is the id of your facebook app
    let htmlContent = `
<\!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>${data.metaTitle}</title>
    <meta property="fb:app_id" content="<your-fb-app-id>">
    <meta property="og:title" content="${data.metaTitle}" />
    <meta property="og:description" content="${data.metaDescription}" />
    <meta property="og:image" content="${data.metaImageUrl}" />
    <meta property="og:url" content="${ogUrl}" />
    <meta property="og:type" content="website" />
    <meta property="og:locale" content="sk_SK" />
  </head>
  <body>

  </body>
</html>
`;

    const response = {
      status: '200',
      statusDescription: 'OK',
      headers: {
        "content-type": [{
          "key": "Content-Type",
          "value": "text/html; charset=utf-8"
        }],
        "cache-control": [{
          "key": "Cache-Control",
          "value": "max-age=100"
        }]
      },
      body: htmlContent,
    };

    callback(null, response);

  } else {
    callback(null, request);
  }
};
	'use strict';

	import { createRequire } from 'module';
	const require = createRequire(import.meta.url);
	const https = require('https');

	export const handler = async(event, context, callback) => {

	let content = "";
	let userAgent = false;

	const request = event.Records[0].cf.request;
	const headers = request.headers;
	if(headers){
	userAgent = request.headers['user-agent'];
	}

	// NOTE: Identify the facebook share request by user-agent header
	// I added few more, but 'facebookexternalhit' is the most important one
	let prerender = /Facebot\|FacebookBot\|facebookexternalhit\|twitterbot/i.test(userAgent[0].value);

	if(prerender){
	let path = request.uri;
	let options = {
	// NOTE: link to your API endpoint
	hostname: "<api-endpoint>",
	path: path,
	headers: {
	"Content-Type": "application/json",
	}
	}

	const initialResponse = await new Promise((resolve, reject) => {
	const req = https.get(options, function(res) {
	res.on('data', chunk => {
	content += chunk;
	});
	res.on('end', () => {
	resolve({
	statusCode: 200,
	body: content.toString()
	});
	});
	});

	req.on('error', (e) => {
	reject({
	statusCode: 400,
	body: e
	});
	});
	});

	// Our API returns the meta data in JSON format so we need to parse it
	let data = JSON.parse(initialResponse.body);

	// NOTE: We need to get the full url of the page we are sharing
	let ogUrl = `https://${headers['host'][0]['value']}${request.uri}`

	// NOTE: We need to generate the HTML code with the meta data
	// Our meta keys fetched from API are:
	// metaTitle - title of the page
	// metaDescription - description of the page
	// metaImageUrl - image of the page
	// if any of these are different, don't forget to change them in the code below (f.e. og:locale)
	// The fb:app_id is the id of your facebook app
	let htmlContent = `
	<\!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="utf-8">
	<title>${data.metaTitle}</title>
	<meta property="fb:app_id" content="<your-fb-app-id>">
	<meta property="og:title" content="${data.metaTitle}" />
	<meta property="og:description" content="${data.metaDescription}" />
	<meta property="og:image" content="${data.metaImageUrl}" />
	<meta property="og:url" content="${ogUrl}" />
	<meta property="og:type" content="website" />
	<meta property="og:locale" content="sk_SK" />
	</head>
	<body>

	</body>
	</html>
	`;

	const response = {
	status: '200',
	statusDescription: 'OK',
	headers: {
	"content-type": [{
	"key": "Content-Type",
	"value": "text/html; charset=utf-8"
	}],
	"cache-control": [{
	"key": "Cache-Control",
	"value": "max-age=100"
	}]
	},
	body: htmlContent,
	};

	callback(null, response);

	} else {
	callback(null, request);
	}
	};