index.js

// Imports
// Packages
const { Webhook, MessageBuilder } = require('discord-webhook-node');
const express = require('express');
const crypto = require('crypto');

// Local files
const config = require('./config');

// Init
const app = express();
app.listen(3000);
app.use(express.json());

const hook = new Webhook(config.discordWebhookUrl);
hook.setUsername('Vercel');
hook.setAvatar('https://i.imgur.com/teXXn5w.png');

// Based on: https://docs.github.com/en/developers/webhooks-and-events/securing-your-webhooks and https://gist.github.com/stigok/57d075c1cf2a609cb758898c0b202428
function verifySignatureMiddleware(req, res, next) {
  const payload = JSON.stringify(req.body);
  if (!payload) return next();

  const sig = req.get('X-Hub-Signature-256') || '';
  const hmac = crypto.createHmac('sha256', config.githubSecret);
  const digest = Buffer.from(`sha256=${hmac.update(payload).digest('hex')}`, 'utf8');
  const checksum = Buffer.from(sig, 'utf8');
  req.body.verified = (digest.length === checksum.length
    ? crypto.timingSafeEqual(digest, checksum)
    : false);
  return next();
}

function sendEmbed(status, color) {
  const embed = new MessageBuilder()
    .setTitle(status.description)
    .setURL(status.target_url)
    .setColor(color)
    .setDescription(`Environment: ${status.environment}`)
    .setFooter(`Deployment ID: ${status.target_url.substring(`https://${config.vercelPrefix}-`.length, `https://${config.vercelPrefix}-`.length + 9)}`)
    .setTimestamp(status.created_at ? new Date(status.created_at) : new Date());
  hook.send(embed);
}

// eslint-disable-next-line consistent-return
app.post('/webhook', verifySignatureMiddleware, (req, res) => {
  if (!req.body.verified) {
    return res.status(403).json({
      code: 'invalid_signature',
      error: "signature didn't match",
    });
  }

  if (req.body.zen) return res.status(200).send('OK');

  if (!req.body.deployment_status) return res.status('400').json({ code: 'bad_request', error: 'not a valid body' });

  const { deployment_status: status } = req.body;
  if (!status.state || !status.target_url || !status.description || !status.environment) return res.status('400').json({ code: 'bad_request', error: 'not a valid body' });

  if (status.state === 'pending') {
    sendEmbed(status, '#faf032');
    res.status(200).send('OK');
  } else if (status.state === 'success') {
    sendEmbed(status, '#32fc40');
    res.status(200).send('OK');
  } else if (status.state === 'failure' || status.state === 'error') {
    sendEmbed(status, '#ff352e');
    res.status(200).send('OK');
  } else return res.status('400').json({ code: 'bad_request', error: 'not a valid body' });
});