Twitch Webhook

server.js

const crypto = require('crypto');
const http = require('http');

const server = http.createServer(async (req, res) => {
  if (req.method === 'GET') {
    return handleSubscriptionVerification(req, res);
  } else if (req.method === 'POST') {
    return await handleEventNotification(req, res);
  }

  res.statusCode = 400;
  res.end();
})

server.on('listening', () => {
  log(`=> Twitch Webhook Server running on ${JSON.stringify(server.address())}`);
});
server.listen(process.env.PORT || 3000);

const handleSubscriptionVerification = (req, res) => {
  const parsed = new URL(req.url, `http://${req.headers.host}`);

  const mode = parsed.searchParams.get('hub.mode');
  const challenge = parsed.searchParams.get('hub.challenge');

  log(`=> Receiving subscription verification, { mode: "${mode}", challenge: "${challenge}" }`);
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end(challenge);
}

const handleEventNotification = async (req, res) => {
  console.log(req.url);
  console.log(req.headers);

  req.setEncoding('utf8');
  let input = '';
  for await (const chunk of req) {
    input += chunk
  }

  const secret = '<secret>';
  const signatureHeader = req.headers['x-hub-signature'] || '';
  const [algorithm, signature] = signatureHeader.split('=');

  if (algorithm !== 'sha256' || !signature) {
    log(`=> Event notification, invalid hub signature!`);
    res.statusCode = 400;
    res.end();
    return;
  }
  
  const digest = crypto.createHmac('sha256', secret)
    .update(input)
    .digest('hex');

  if (signature !== digest) {
    log(`=> Event notification, invalid hub signature or secret!`);
    res.statusCode = 400;
    res.end();
    return;
  }

  inputJSON = JSON.parse(input);
  console.log(inputJSON);

  if (inputJSON && inputJSON.data && inputJSON.data.length) {
    log(`Stream is live, { title: "${inputJSON.data[0].title}" }`);
  } else {
    log('Stream has ended.');
  }

  res.statusCode = 204;
  res.end();
};

const log = (msg) => {
  console.log(new Date(), `=> ${msg}`);
};