const ObservableStore = require('obs-store')
const extend = require('xtend')
const log = require('loglevel')
// every ten minutes
const POLLING_INTERVAL = 600000
class CurrencyController {
/**
* Controller responsible for managing data associated with the currently selected currency.
*
* @typedef {Object} CurrencyController
* @param {object} opts Overrides the defaults for the initial state of this.store
* @property {array} opts.initState initializes the the state of the CurrencyController. Can contain an
* currentCurrency, conversionRate and conversionDate properties
* @property {string} currentCurrency A 2-4 character shorthand that describes a specific currency, currently
* selected by the user
* @property {number} conversionRate The conversion rate from ETH to the selected currency.
* @property {string} conversionDate The date at which the conversion rate was set. Expressed in in milliseconds
* since midnight of January 1, 1970
* @property {number} conversionInterval The id of the interval created by the scheduleConversionInterval method.
* Used to clear an existing interval on subsequent calls of that method.
*
*/
constructor (opts = {}) {
const initState = extend({
currentCurrency: 'usd',
conversionRate: 0,
conversionDate: 'N/A',
}, opts.initState)
this.store = new ObservableStore(initState)
}
//
// PUBLIC METHODS
//
/**
* A getter for the currentCurrency property
*
* @returns {string} A 2-4 character shorthand that describes a specific currency, currently selected by the user
*
*/
getCurrentCurrency () {
return this.store.getState().currentCurrency
}
/**
* A setter for the currentCurrency property
*
* @param {string} currentCurrency The new currency to set as the currentCurrency in the store
*
*/
setCurrentCurrency (currentCurrency) {
this.store.updateState({ currentCurrency })
}
/**
* A getter for the conversionRate property
*
* @returns {string} The conversion rate from ETH to the selected currency.
*
*/
getConversionRate () {
return this.store.getState().conversionRate
}
/**
* A setter for the conversionRate property
*
* @param {number} conversionRate The new rate to set as the conversionRate in the store
*
*/
setConversionRate (conversionRate) {
this.store.updateState({ conversionRate })
}
/**
* A getter for the conversionDate property
*
* @returns {string} The date at which the conversion rate was set. Expressed in milliseconds since midnight of
* January 1, 1970
*
*/
getConversionDate () {
return this.store.getState().conversionDate
}
/**
* A setter for the conversionDate property
*
* @param {number} conversionDate The date, expressed in milliseconds since midnight of January 1, 1970, that the
* conversionRate was set
*
*/
setConversionDate (conversionDate) {
this.store.updateState({ conversionDate })
}
/**
* Updates the conversionRate and conversionDate properties associated with the currentCurrency. Updated info is
* fetched from an external API
*
*/
async updateConversionRate () {
let currentCurrency
try {
currentCurrency = this.getCurrentCurrency()
const response = await fetch(`https://api.infura.io/v1/ticker/eth${currentCurrency.toLowerCase()}`)
const parsedResponse = await response.json()
this.setConversionRate(Number(parsedResponse.bid))
this.setConversionDate(Number(parsedResponse.timestamp))
} catch (err) {
log.warn(`MetaMask - Failed to query currency conversion:`, currentCurrency, err)
this.setConversionRate(0)
this.setConversionDate('N/A')
}
}
/**
* Creates a new poll, using setInterval, to periodically call updateConversionRate. The id of the interval is
* stored at the controller's conversionInterval property. If it is called and such an id already exists, the
* previous interval is clear and a new one is created.
*
*/
scheduleConversionInterval () {
if (this.conversionInterval) {
clearInterval(this.conversionInterval)
}
this.conversionInterval = setInterval(() => {
this.updateConversionRate()
}, POLLING_INTERVAL)
}
}
module.exports = CurrencyController
