uci-mqtt/src/client.js

import { connect } from 'async-mqtt'
import merge from 'lodash.merge'
import btc from 'better-try-catch'
import union from 'lodash.union'
import xor from 'lodash.xor'
import logger from '@uci-utils/logger'
import isPlainObject from 'is-plain-object'

let log = {}

/**
 * MQTT - Client - An mqtt client that supports UCI packets
 * it extends the {@link https://github.com/mqttjs/async-mqtt| async version this mqtt client } albiet in a clunky way with a private extend method because it was not written as an extendable class
 * @extends MQTT.js
 */
class MQTTClient {
  /**
   * constructor - Description
   *
   * @param {object} [opts={}] Description
   *
   */
  constructor(opts = {}) {
    this.id = opts.id || opts.name || 'mqtt:' + new Date().getTime()
    log = logger({
      file: 'src/client.js',
      class: 'Client',
      name: 'mqtt',
      id: this.id
    })
    this.url = opts.url || ''
    // subscription topics can be string of commna delimited or array of strings see object see mqtt.js docs
    this.topics = Array.isArray(opts.topics)
      ? opts.topics
      : opts.topics
        ? opts.topics.split(',')
        : [this.id]
    this.opts = opts.connect || {} // see options for new mqtt.Client
    // self bindings
    this.connect = this.connect.bind(this)
    this.push = this.send
  }

  /**
   * connect - Description
   *
   * @returns {type} Description
   */
  async connect() {
    return new Promise((resolve, reject) => {
      let mqtt = connect(
        this.url,
        this.opts
      )
      this._extend(mqtt, 'subscribe,unsubscribe') // merge mqtt client into class extend with given functions
      let timeout = this.opts.connectTimeout || 5000
      setTimeout(() => {
        reject({msg:'ending mqtt connection attempt, no broker', url:this.url, opts:this.opts})
      }, timeout)

      this.once('connect', () => {
        this._log()
        this._listen()

        this.on('reconnect', () => {
          log.info('mqtt client reconnected to broker')
          this.subscribe(this.topics)
        })

        this.on('error', err => {
          log.fatal({ err: err }, 'connection error to broker')
        })

        this.subscribe(this.topics)
        log.info(
          { options: this._client.options },
          `mqtt client connected to broker at ${
            this._client.options.hostname
          }:${this._client.options.port}`
        )
        resolve(
          `mqtt client connected to broker at ${
            this._client.options.hostname
          }:${this._client.options.port}`
        )
      })
    }) //end promise
  }

  async subscribe(topic, options = {}) {
    if (options.pub) {
      if (typeof topic === 'string') topic = topic.split(',')
      this.topics = union(this.topics, topic)
    }
    log.info(`subscription for topic ${topic} added`)
    this._subscribe(topic, options)
  }

  async unsubscribe(topic, options = {}) {
    if (!options.pub) {
      if (typeof topic === 'string') topic = topic.split(',')
      this.topics = xor(this.topics, topic)
    }
    this._unsubscribe(topic)
  }

  async send(packet, topics, options) {
    if (!this.hasOwnProperty('publish')) {
      log.warn({url:this.url, opts:this.opts, msg:'connect method never called, initialization needed, aborting send'})
      return
    }
    if (typeof topics !== 'string' && !Array.isArray(topics)) {
      options = topics
      topics = this.topics
    } else {
      if (typeof topics === 'string') topics = topics.split(',')
    }
    let payload = {}
    if (typeof packet !== 'string') {
      payload = this._serialize(packet)
      if (!payload)
        payload = this._serialize({ err: 'could not serialze packet' })
      topics = [packet.cmd] || topics // if payload has a cmd use that as topic
    } else payload = this._serialize({ data: packet })
    let pubs = []
    topics.forEach(async topic => {
      log.info(`sending ${payload} to topic ${topic} with options ${options}`)
      pubs.push(this.publish(topic, payload, options))
    })
    return await Promise.all(pubs)
  }

  registerPacketProcessor(func) {
    this._packetProcess = func
  }

  _serialize(json) {
    let [err, payload] = btc(JSON.stringify)(json)
    if (err) {
      log.warn(`error unable to stringify json:${json}`)
      return null
    }
    return payload
  }

  _listen() {
    log.info(
      `listening for incoming packets from broker on topics ${this.topics}`
    )
    this.on('message', messageProcess.bind(this))

    async function messageProcess(topic, payload) {
      log.info('incoming message on topic', topic)
      let packet = this._handlePayload(payload)
      if (packet) packet.cmd = packet.cmd || topic
      // payload had no command that use topic as cmd
      else packet = { cmd: topic }
      let res = (await this._packetProcess(packet, topic)) || {}
      this.send(res)
    }
  }

  _handlePayload(payload) {
    let [err, packet] = btc(JSON.parse)(payload.toString())
    if (err) {
      log.info('payload not json returning as prop data:<payload>')
    }
    if (!isPlainObject(packet)) packet = { data: payload.toString() }
    return packet
  }

  // default packet process just a simple console logger.  ignores any cmd: prop
  _packetProcess(packet, topic) {
    console.log('=========================')
    console.log(
      'default consumer processor\npacket from broker on topic:',
      topic
    )
    console.dir(packet)
    console.log(packet.status)
    console.log('========================')
  }

  async _log() {
    log = logger({
      file: 'src/client.js',
      class: 'Client',
      package: '@uci/mqtt',
      id: this.id
    })

    this.on('close', () => {
      log.info('connection to broker was closed')
    })

    this.on('offline', () => {
      log.info('this client has gone offline from broker')
    })

    this.on('packetsend', packet => {
      log.info({ packet: packet }, 'outgoing packet to mqtt broker')
    })

    this.on('packetreceive', packet => {
      log.info({ packet: packet }, 'incoming packet from mqtt broker')
    })
  }

  _extend(obj, funcs) {
    let temp = {}
    funcs = funcs.split(',')
    funcs.forEach(func => {
      temp[func] = this[func]
    })
    merge(this, obj)
    funcs.forEach(func => {
      this['_' + func] = this[func]
      this[func] = temp[func]
    })
  }
} // end mqtt client class

export default MQTTClient