rocket.chat.mqtt/node_modules/aedes/lib/handlers/subscribe.js

It's a MQTT Server, using redis to scale horizontally.

'use strict'

var write = require('../write')
var fastfall = require('fastfall')
var Packet = require('aedes-packet')
var through = require('through2')
var validateTopic = require('./validations').validateTopic
var topicActions = fastfall([
  authorize,
  storeSubscriptions,
  subTopic
])

function SubscribeState (client, packet, finish, granted) {
  this.client = client
  this.packet = packet
  this.finish = finish
  this.granted = granted
}

function handleSubscribe (client, packet, done) {
  var broker = client.broker
  var subs = packet.subscriptions
  var granted = []

  broker._series(
    new SubscribeState(client, packet, done, granted),
    doSubscribe,
    subs,
    completeSubscribe)
}

function doSubscribe (sub, done) {
  // TODO this function should not be needed
  topicActions.call(this, sub, done)
}

function authorize (sub, done) {
  var client = this.client
  var err = validateTopic(sub.topic, 'SUBSCRIBE')
  if (err) {
    return done(err)
  }
  client.broker.authorizeSubscribe(client, sub, done)
}

function blockSys (func) {
  return function deliverSharp (packet, cb) {
    if (packet.topic.indexOf('$SYS') === 0) {
      cb()
    } else {
      func(packet, cb)
    }
  }
}

function Subscription (qos, func) {
  this.qos = qos
  this.func = func
}

function storeSubscriptions (sub, done) {
  var packet = this.packet
  var client = this.client
  var broker = client.broker
  var perst = broker.persistence

  if (sub && packet.subscriptions[0].topic !== sub.topic) {
    // don't call addSubscriptions per topic,
    // TODO change aedes subscribe handle, but this is a fast & dirty fix for now
    return done(null, sub)
  }

  if (packet.restore) {
    return done(null, sub)
  }

  if (client.clean) {
    return done(null, sub)
  }

  perst.addSubscriptions(client, packet.subscriptions, function (err) {
    done(err, sub)
  })
}

function subTopic (sub, done) {
  if (!sub) {
    this.granted.push(128)
    return done()
  }

  var client = this.client
  var broker = client.broker
  var func = nop

  switch (sub.qos) {
    case 2:
    case 1:
      func = client.deliverQoS
      break
    default:
      func = client.deliver0
      break
  }

  if (isWildcardThatMatchesSys(sub.topic)) {
    func = blockSys(func)
  }

  this.granted.push(sub.qos)

  if (!client.subscriptions[sub.topic]) {
    client.subscriptions[sub.topic] = new Subscription(sub.qos, func)
    broker.subscribe(sub.topic, func, done)
  } else if (client.subscriptions[sub.topic].qos !== sub.qos) {
    broker.unsubscribe(sub.topic, client.subscriptions[sub.topic].func)
    client.subscriptions[sub.topic] = new Subscription(sub.qos, func)
    broker.subscribe(sub.topic, func, done)
  } else {
    done()
  }
}

// + is 43
// # is 35
function isWildcardThatMatchesSys (topic) {
  var code = topic.charCodeAt(0)
  return code === 43 || code === 35
}

function completeSubscribe (err) {
  var packet = this.packet
  var client = this.client
  var broker = client.broker
  var granted = this.granted
  var done = this.finish

  if (err) {
    return done(err)
  }

  if (!packet.restore) {
    broker.emit('subscribe', packet.subscriptions, client)
  }

  if (packet.messageId) {
    write(client, new SubAck(packet, granted), done)
  } else {
    done()
  }

  var persistence = broker.persistence
  var topics = []
  for (var i = 0; i < packet.subscriptions.length; i++) {
    topics.push(packet.subscriptions[i].topic)
  }
  var stream = persistence.createRetainedStreamCombi(topics)
  stream.pipe(through.obj(function sendRetained (packet, enc, cb) {
    packet = new Packet(packet)
    // this should not be deduped
    packet.brokerId = null
    client.deliver0(packet, cb)
  }))
}

function SubAck (packet, granted) {
  this.cmd = 'suback'
  this.messageId = packet.messageId
  this.granted = granted
}

function nop () {}

module.exports = handleSubscribe