const mqtt = require('mqtt')
const { MongoClient } = require('mongodb')
const _ = require('lodash')
const dbClient = new MongoClient("mongodb://admin:03112546@mqtt.timovolkmann.de:27017/Smart_Garden", { useUnifiedTopology: true })

export default async function startMqttObserver() {
  console.log("setup connections...")
  // setup mongodb
  dbClient.connect(err => {
    if (err) {console.log("mongodb connection error")} else {console.log("mongodb connected.")}
    const db = dbClient.db("Smart_Garden")
    const sensorData = db.collection('sensorData');
    console.log("collection retrieved.")
    // setup mqtt client
    let mqttClient = mqtt.connect('mqtt://mqtt.timovolkmann.de')
    mqttClient.on('connect', onMqttConnect(mqttClient))
    mqttClient.on('message', messageCallback(sensorData))
  })
}  

function messageCallback(collection) {
  return function (topic, message) {
    let topicElements = topic.split('/');
    const type = topicElements.pop();
    const id = topicElements.pop();

    var date = new Date;

    let doc = {
      device_id: id,
      timestamp: date,
    }
    try {
      doc = _.merge(doc, JSON.parse(message));
    } catch {

    }
    if (type === 'data') {
      console.log(doc);
      collection.insertOne(doc)
    }
  }
}

function onMqttConnect(mqttClient) {
  return function () {
    mqttClient.subscribe('smartgarden/updates/#', function (err) {
      if (err) console.log(err);
      console.log("Sucessfully subscribed...");
    })
  }
}