app.js

/* eslint-disable no-use-before-define */
const createError = require('http-errors');
const express = require('express');
const cookieParser = require('cookie-parser');
const logger = require('morgan');
const mqtt = require('mqtt');
const mongoose = require('mongoose');
const actions = require('./src/actions/actions');
const { indexRouter, usersRouter, sensorRoute } = require('./src/routes/index');
const { parseMessage } = require('./src/utils');

const app = express();

const mqttUrl = process.env.CLOUDMQTT_URL || 'mqtt://localhost:1883';
const msgTopic = '#'; // subscribe to *all* topics
const client = mqtt.connect(mqttUrl);
client.on('connect', onConnect);

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());

app.use('/', indexRouter);
app.use('/users', usersRouter);
app.use('/sensor', sensorRoute);

// catch 404 and forward to error handler
app.use((req, res, next) => next(createError(404)));

app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*');
  res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept');
  next();
});

// error handler
app.use((err, req, res) => {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

// Establish MongoDB connection
mongoose.connect(process.env.Mongo_URL, { useNewUrlParser: true, useUnifiedTopology: true });
const mongodb = mongoose.connection;

mongodb.on('error', err => console.error(err));
mongodb.once('open', () => console.log('mongodb: connection established'));

/**
 * Event listener for MQTT "connect" event.
 */
function onConnect() {
  client.publish('broker/connected', 'true');

  client.subscribe(msgTopic, () => {
    client.on('message', async (topic, message) => onMessage(topic, message));
  });
}

// NOTE: topic can contain only strings, "-" and "_"
async function onMessage(topic, message) {
  // simple regex to match either:
  // 1. a string: "topic"
  // 2. string with a slash: "topic/somethingelse"
  if (/([A-Za-z\-_]+$|[A-Za-z\-_]+\/[A-Za-z\-_]+$)/g.test(topic)) {
    const parsed = parseMessage(message);
    let deviceId = -1;
    let data = [];

    if (parsed instanceof Object) {
      deviceId = parsed.from || parsed.device || parsed.deviceId || -1;
      data = [...parsed.data];
    } else {
      data = [parsed];
    }

    await actions.saveSensorData({ data, topic, deviceId });
  }
}

module.exports = app;