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