SubsManager for React Native Meteor

SubsManager.js

import Meteor from 'react-native-meteor'
import _ from 'lodash'
import Trackr from 'trackr'
import EJSON from 'ejson'

const SubsManager = function (options) {
  const self = this
  self.options = options || {}
  // maxiumum number of subscriptions are cached
  self.options.cacheLimit = self.options.cacheLimit || 10
  // maximum time, subscription stay in the cache
  self.options.expireIn = self.options.expireIn || 5

  self._cacheMap = {}
  self._cacheList = []
  self._ready = false
  self.dep = new Trackr.Dependency()

  self.computation = self._registerComputation()
}

SubsManager.prototype.subscribe = function () {
  const self = this
  const args = _.toArray(arguments)
  this._addSub(args)

  return {
    ready() {
      self.dep.depend()
      return self._ready
    },
  }
}

SubsManager.prototype._addSub = function (args) {
  const self = this
  const hash = EJSON.stringify(args)
  // const subName = args[0]
  // const paramsKey = EJSON.stringify(args.slice(1))

  if (!self._cacheMap[hash]) {
    const sub = {
      args,
      hash,
    }

    this._handleError(sub)

    self._cacheMap[hash] = sub
    self._cacheList.push(sub)

    self._ready = false

    // to notify the global ready()
    self._notifyChanged()

    // no need to interfere with the current computation
    self._reRunSubs()
  }

  // add the current sub to the top of the list
  const sub = self._cacheMap[hash]
  sub.updated = (new Date()).getTime()

  const index = _.indexOf(self._cacheList, sub)
  self._cacheList.splice(index, 1)
  self._cacheList.push(sub)
}

SubsManager.prototype._reRunSubs = function () {
  const self = this

  if (Trackr.currentComputation)
    Trackr.afterFlush(() => self.computation.invalidate())
  else
    self.computation.invalidate()
}

SubsManager.prototype._notifyChanged = function () {
  const self = this

  if (Trackr.currentComputation)
    setTimeout(() => self.dep.changed(), 0)
  else
    self.dep.changed()
}

SubsManager.prototype._applyCacheLimit = function () {
  const self = this
  const overflow = self._cacheList.length - self.options.cacheLimit
  if (overflow > 0) {
    const removedSubs = self._cacheList.splice(0, overflow)
    _.each(removedSubs, sub => {
      delete self._cacheMap[sub.hash]
    })
  }
}

SubsManager.prototype._applyExpirations = function () {
  const self = this
  const newCacheList = []

  const expirationTime = (new Date()).getTime() - (self.options.expireIn * 60 * 1000)
  _.each(self._cacheList, sub => {
    if (sub.updated >= expirationTime)
      newCacheList.push(sub)
    else
      delete self._cacheMap[sub.hash]
  })

  self._cacheList = newCacheList
}

SubsManager.prototype._registerComputation = function () {
  const self = this
  const computation = Trackr.autorun(() => {
    self._applyExpirations()
    self._applyCacheLimit()

    let ready = true
    _.each(self._cacheList, sub => {
      sub.ready = Meteor.subscribe.apply(Meteor, sub.args).ready()
      ready = ready && sub.ready
    })

    if (ready) {
      self._ready = true
      self._notifyChanged()
    }
  })

  return computation
}

SubsManager.prototype._createIdentifier = args => {
  const tmpArgs = _.map(args, value => {
    if (typeof value === 'string')
      return `"${value}"`

    return value
  })

  return tmpArgs.join(', ')
}

SubsManager.prototype._handleError = function (sub) {
  const args = sub.args
  const lastElement = _.last(args)
  sub.identifier = this._createIdentifier(args)

  function errorHandlingLogic(err) {
    console.log('Error invoking SubsManager.subscribe(%s): ', sub.identifier, err.reason)
    // expire this sub right away.
    // Then expiration machanism will take care of the sub removal
    sub.updated = new Date(1)
  }

  if (!lastElement) {
    args.push({ onError: errorHandlingLogic })
  } else if (typeof lastElement === 'function') {
    args.pop()
    args.push({ onReady: lastElement, onError: errorHandlingLogic })
  } else if (typeof lastElement.onError === 'function') {
    const originalOnError = lastElement.onError
    lastElement.onError = function (err) {
      errorHandlingLogic(err)
      originalOnError(err)
    }
  } else if (typeof lastElement.onReady === 'function') {
    lastElement.onError = errorHandlingLogic
  } else {
    args.push({ onError: errorHandlingLogic })
  }
}

SubsManager.prototype.reset = function () {
  const self = this
  const oldComputation = self.computation
  self.computation = self._registerComputation()

  // invalidate the new compuation and it will fire new subscriptions
  self.computation.invalidate()

  // after above invalidation completed, fire stop the old computation
  // which then send unsub messages
  // mergeBox will correct send changed data and there'll be no flicker
  Trackr.afterFlush(() => oldComputation.stop())
}

SubsManager.prototype.clear = function () {
  this._cacheList = []
  this._cacheMap = {}
  this._reRunSubs()
}

SubsManager.prototype.ready = function () {
  this.dep.depend()

  // if there are no items in the cacheList we are not ready yet.
  if (this._cacheList.length === 0)
    return false

  return this._ready
}

export default SubsManager

any update to this?