server.js

require('dotenv').config();

const debug = require('debug')('green-thumb:server');
const app = require('./app');

const PORT = parseInt(process.env.PORT, 10);

app.use((req, res, next) => {
  res.status(404);
  res.render('not-found');
});

app.use((err, req, res, next) => {
  // always log the error
  console.error('ERROR', req.method, req.path, err);

  // only render if the error ocurred before sending the response
  if (!res.headersSent) {
    res.status(500);
    res.render('error');
  }
});

const terminate = error => {
  if (error) debug(error);
  const exitCode = error && error instanceof Error ? 1 : 0;
  debug('Terminating node app.');
  process.exit(exitCode);
};

process.on('SIGINT', () => terminate());
process.on('SIGTERM', () => terminate());
process.on('uncaughtException', error => {
  debug('There was an uncaught exception.');
  terminate(error);
});
process.on('unhandledRejection', error => {
  debug('There was an unhandled promise rejection.');
  terminate(error);
});

const onError = error => {
  const { syscall, port, code } = error;
  if (syscall === 'listen' && code === 'EADDRINUSE') {
    console.error(`Port ${port} is already in use`);
    process.exit(1);
  } else {
    console.error('There was an unknown error.');
    debug(error);
    throw error;
  }
};

const onListening = server => {
  const { port } = server.address();
  debug(`Node server listening on ${port}`);
  if (process.env.NODE_ENV === 'development')
    debug(`Visit http://localhost:${port} to develop your app`);
};

const initiate = () => {
  app.set('port', PORT);

  const server = app.listen(PORT);
  server.on('error', error => onError(error));
  server.on('listening', () => onListening(server));
};

initiate();