text: const express = require('express');
  const path = require('path');
  const helmet = require('helmet');
  const morgan = require('morgan');
  
  const serialport = require('serialport');
  
  const { FORGE_CLIENT_ID, FORGE_CLIENT_SECRET, FORGE_MODEL_URN, MONGODB_URL } = process.env;
  if (!FORGE_CLIENT_ID || !FORGE_CLIENT_SECRET || !FORGE_MODEL_URN || !MONGODB_URL) {
    console.warn('Provide all the following env. variables to run this application:');
    console.warn('FORGE_CLIENT_ID, FORGE_CLIENT_SECRET, FORGE_MODEL_URN, MONGODB_URL');
    return;
  }
  
  const db = require('./model/db');
  const app = express();
  
  app.use(
    helmet.contentSecurityPolicy({
      directives: {
        defaultSrc: ["*", "data:", "blob:", "'unsafe-inline'"]
      },
    })
  );
  app.set('view engine', 'pug');
  app.use(morgan('combined'));
  app.use(express.json());
  app.use(express.urlencoded({ extended: false }));
  app.use(express.static(path.join(__dirname, 'public')));
  
  app.use('/', require('./routes/index'));
  app.use('/api/auth', require('./routes/auth'));
  app.use('/api/monitor', require('./routes/monitor'));
  
  const port = process.env.PORT || 3000;
  db.connect()
    .then(() => app.listen(port, () => console.log(`Server listening on port ${port}`)))
    .catch((err) => console.error(err));