mailer.js

const { send, text } = require('micro')
const post = require('micro-post')
const redirect = require('micro-redirect')
const qs = require('qs');
const mailgun = require('mailgun.js');
const fetch = require('node-fetch');
const cheerio = require('cheerio');

const domain = process.env.MAILGUN_DOMAIN;
const sender = process.env.MAILGUN_SENDER;

var mg = mailgun.client({
  username: 'api',
  key: process.env.MAILGUN_API_KEY,
  public_key: process.env.MAILGUN_API_PUBLIC_KEY,
});

const validateRecipient = async (to, origin) => {
  try {
    if (!to || to === '') {
      return false;
    }
    const result = await fetch(origin);
    const html = await result.text();
    const $ = cheerio.load(html);
    const meta = $('meta[name="emails" i]').first();
    const emails = meta[0].attribs.content.split(',').map(email => email.trim());
    return emails.includes(to);
  } catch (e) {
    return false;
  }
}

const app = async (req, res) => {
  const { referer, origin } = req.headers;
  if (!referer.includes(origin)) {
    return send(res, 403, 'Bye')
  }
  const urlencoded = await text(req);
  const js = qs.parse(urlencoded);
  console.log('js', js);
  const validRecipient = await validateRecipient(js.to, origin);
  if (!validRecipient) {
    return send(res, 400, 'Invalid recipient');
  }
  const validate = await mg.validate.get(js.from);
  console.log('validate', validate);
  if (!validate.is_valid) {
    return send(res, 400, 'Invalid sender');
  }
  const msg = await mg.messages.create(domain, {
    from: "A Website Visitor <" + sender + ">",
    to: [js.to],
    subject: "Hello",
    text: "Testing some Mailgun awesomness!",
    html: "<h1>Testing some Mailgun awesomness!</h1>"
  })
  console.log('msg', msg);
  if (referer) {
    const statusCode = 302;
    return redirect(res, statusCode, referer);
  }
  return send(res, 200, `It's a POST request!`);
}

module.exports = post(app);