Host Wildcard Subdomain in One S3 Bucket https://blackbing.medium.com/host-wildcard-subdomain-in-one-s3-bucket-with-lambda-edge-979c7cb282dc

Host-Wildcard-Subdomain-in-One-S3-Bucket-origin-response.js

'use strict';

const http = require('http');

exports.handler = (event, context, callback) => {
  const request = event.Records[0].cf.request;
  const response = event.Records[0].cf.response;
  
  if (response.status == 404) {
    const domainHash = request.headers['x-domain-hash'] && request.headers['x-domain-hash'][0].value;
    if (domainHash) {
      const host = request.headers['host'][0].value;
      const url = `http://${host}/${domainHash}/index.html`;
      console.log(url);
      
      downloadContent(url, function(body, error) {
        if (error) {
          console.log(error)
          callback(null, response);
        } else {
          const newResponse = {
            status: 200,
            statusDescription: 'OK',
            headers: response.headers,
            body
          };
          newResponse.headers['content-type'] = [{
            key: 'Content-Type',
            value: 'text/html'
          }];
          callback(null, newResponse);
        }
      })
    }
    
  } else {
    callback(null, response);
  }
};