events.js

const EventEmitter = require('eventemitter3');
const emitter = new EventEmitter();

function subscribe(req, res) {
  
  res.writeHead(200, {
    'Content-Type': 'text/event-stream',
    'Cache-Control': 'no-cache',
    Connection: 'keep-alive'
  });
  
  // Heartbeat
  res.write('\n');
  const nln = function() {
    res.write('\n');
  };
  const hbt = setInterval(nln, 15000);
  
  const onEvent = function(data) {
    res.write('retry: 500\n');
    res.write(`event: event\n`);
    res.write(`data: ${JSON.stringify(data)}\n\n`);
  };
  
  emitter.on('event', onEvent);
  
  // Clear heartbeat and listener
  req.on('close', function() {
    clearInterval(hbt);
    emitter.removeListener('event', onEvent);
  });
}

function publish(req, res) {
  // Emit events here recieved from Github/Twitter APIs
  emitter.emit('event', req.body);
  res.status(200).send();
}

module.exports = {
  subscribe, // Sending event data to the clients
  publish // Emiting events from streaming servers
};