controllers/currency.js

  1. const ObservableStore = require('obs-store')
  2. const extend = require('xtend')
  3. const log = require('loglevel')
  5. // every ten minutes
  6. const POLLING_INTERVAL = 600000
  8. class CurrencyController {
  10.   /**
  11.    * Controller responsible for managing data associated with the currently selected currency.
  12.    *
  13.    * @typedef {Object} CurrencyController
  14.    * @param {object} opts Overrides the defaults for the initial state of this.store
  15.    * @property {array} opts.initState  initializes the the state of the CurrencyController. Can contain an
  16.    * currentCurrency, conversionRate and conversionDate properties
  17.    * @property {string} currentCurrency A 2-4 character shorthand that describes a specific currency, currently
  18.    * selected by the user
  19.    * @property {number} conversionRate The conversion rate from ETH to the selected currency.
  20.    * @property {string} conversionDate The date at which the conversion rate was set. Expressed in in milliseconds
  21.    * since midnight of January 1, 1970
  22.    * @property {number} conversionInterval The id of the interval created by the scheduleConversionInterval method.
  23.    * Used to clear an existing interval on subsequent calls of that method.
  24.    *
  25.    */
  26.   constructor (opts = {}) {
  27.     const initState = extend({
  28.       currentCurrency: 'usd',
  29.       conversionRate: 0,
  30.       conversionDate: 'N/A',
  31.     }, opts.initState)
  32.     this.store = new ObservableStore(initState)
  33.   }
  35.   //
  36.   // PUBLIC METHODS
  37.   //
  39.   /**
  40.    * A getter for the currentCurrency property
  41.    *
  42.    * @returns {string} A 2-4 character shorthand that describes a specific currency, currently selected by the user
  43.    *
  44.    */
  45.   getCurrentCurrency () {
  46.     return this.store.getState().currentCurrency
  47.   }
  49.   /**
  50.    * A setter for the currentCurrency property
  51.    *
  52.    * @param {string} currentCurrency The new currency to set as the currentCurrency in the store
  53.    *
  54.    */
  55.   setCurrentCurrency (currentCurrency) {
  56.     this.store.updateState({ currentCurrency })
  57.   }
  59.   /**
  60.    * A getter for the conversionRate property
  61.    *
  62.    * @returns {string} The conversion rate from ETH to the selected currency.
  63.    *
  64.    */
  65.   getConversionRate () {
  66.     return this.store.getState().conversionRate
  67.   }
  69.   /**
  70.    * A setter for the conversionRate property
  71.    *
  72.    * @param {number} conversionRate The new rate to set as the conversionRate in the store
  73.    *
  74.    */
  75.   setConversionRate (conversionRate) {
  76.     this.store.updateState({ conversionRate })
  77.   }
  79.   /**
  80.    * A getter for the conversionDate property
  81.    *
  82.    * @returns {string} The date at which the conversion rate was set. Expressed in milliseconds since midnight of
  83.    * January 1, 1970
  84.    *
  85.    */
  86.   getConversionDate () {
  87.     return this.store.getState().conversionDate
  88.   }
  90.   /**
  91.    * A setter for the conversionDate property
  92.    *
  93.    * @param {number} conversionDate The date, expressed in milliseconds since midnight of January 1, 1970, that the
  94.    * conversionRate was set
  95.    *
  96.    */
  97.   setConversionDate (conversionDate) {
  98.     this.store.updateState({ conversionDate })
  99.   }
  101.   /**
  102.    * Updates the conversionRate and conversionDate properties associated with the currentCurrency. Updated info is
  103.    * fetched from an external API
  104.    *
  105.    */
  106.   async updateConversionRate () {
  107.     let currentCurrency
  108.     try {
  109.       currentCurrency = this.getCurrentCurrency()
  110.       const response = await fetch(`https://api.infura.io/v1/ticker/eth${currentCurrency.toLowerCase()}`)
  111.       const parsedResponse = await response.json()
  112.       this.setConversionRate(Number(parsedResponse.bid))
  113.       this.setConversionDate(Number(parsedResponse.timestamp))
  114.     } catch (err) {
  115.       log.warn(`MetaMask - Failed to query currency conversion:`, currentCurrency, err)
  116.       this.setConversionRate(0)
  117.       this.setConversionDate('N/A')
  118.     }
  119.   }
  121.   /**
  122.    * Creates a new poll, using setInterval, to periodically call updateConversionRate. The id of the interval is
  123.    * stored at the controller's conversionInterval property. If it is called and such an id already exists, the
  124.    * previous interval is clear and a new one is created.
  125.    *
  126.    */
  127.   scheduleConversionInterval () {
  128.     if (this.conversionInterval) {
  129.       clearInterval(this.conversionInterval)
  130.     }
  131.     this.conversionInterval = setInterval(() => {
  132.       this.updateConversionRate()
  133.     }, POLLING_INTERVAL)
  134.   }
  135. }
  137. module.exports = CurrencyController