Lambda code to send email

handler.js

const { readFile } = require('fs').promises;
const mjml = require('mjml');
const i18n = require('i18n');
const htmlToText = require('html-to-text');
const assert = require('assert');
const mustache = require('mustache');
const AWS = require('aws-sdk');

i18n.configure({
  directory: `${process.cwd()}/locales`,
  defaultLocale: 'en',
});

exports.handler = async (event) => {
  const promises = event.Records.map(async (record) => {
    const body = JSON.parse(record.body);
    const mail = await render(body);
    return send(mail, body);
  });
  return Promise.all(promises);
};

const render = async (data) => {
  assert.ok(/^[a-z0-9_-]+$/i.test(data.template));
  const buf = await readFile(`${process.cwd()}/templates/${data.template}.mjml`);
  const content = buf.toString();
  const { html: mjmlToHtml, errors } = mjml(content, {
    filePath: `${process.cwd()}/templates`,
    minify: true,
  });
  assert.ok(errors.length === 0, JSON.stringify(errors));

  const html = mustache.render(mjmlToHtml, {
    ...data,
    t() {
      return (phrase, fn) => fn(
        i18n.__({ phrase, locale: data.locale }, data),
      );
    },
  });
  const subject = html.replace(/\n/g, '').match(/<title>(.+)<\/title>/).pop().trim();

  return {
    html,
    subject,
    text: htmlToText.fromString(html, { ignoreImage: true }),
  };
};

const send = async ({html, text, subject}, data) => {
  const params = {
    Destination: {
      ToAddresses: [`${data.userName} <${data.userEmail}>`],
    },
    Message: {
      Body: {
        Html: { Charset: 'UTF-8', Data: html },
        Text: { Charset: 'UTF-8', Data: text },
      },
      Subject: { Charset: 'UTF-8', Data: subject },
    },
    Source: `Schibsted <${process.env.SENDER_EMAIL}>`,
    ConfigurationSetName: process.env.SES_CONFIG_SET,
    Tags: [
      { Name: 'template', Value: data.template },
      { Name: 'locale', Value: data.locale },
      { Name: 'userId', Value: data.userId },
    ],
  };
  return new AWS.SES({ apiVersion: '2010-12-01' }).sendEmail(params).promise();
};