const ObservableStore = require('obs-store') // By default, poll every 3 minutes const DEFAULT_INTERVAL = 180 * 1000 /** * A controller that polls for token exchange * rates based on a user's current token list */ class TokenRatesController { /** * Creates a TokenRatesController * * @param {Object} [config] - Options to configure controller */ constructor ({ interval = DEFAULT_INTERVAL, preferences } = {}) { this.store = new ObservableStore() this.preferences = preferences this.interval = interval } /** * Updates exchange rates for all tokens */ async updateExchangeRates () { if (!this.isActive) { return } const contractExchangeRates = {} for (const i in this._tokens) { const address = this._tokens[i].address contractExchangeRates[address] = await this.fetchExchangeRate(address) } this.store.putState({ contractExchangeRates }) } /** * Fetches a token exchange rate by address * * @param {String} address - Token contract address */ async fetchExchangeRate (address) { try { const response = await fetch(`https://exchanges.balanc3.net/prices?from=${address}&to=ETH&autoConversion=false&summaryOnly=true`) const json = await response.json() return json && json.length ? json[0].averagePrice : 0 } catch (error) { } } /** * @type {Number} - Interval used to poll for exchange rates */ set interval (interval) { this._handle && clearInterval(this._handle) if (!interval) { return } this._handle = setInterval(() => { this.updateExchangeRates() }, interval) } /** * @type {Object} - Preferences controller instance */ set preferences (preferences) { this._preferences && this._preferences.unsubscribe() if (!preferences) { return } this._preferences = preferences this.tokens = preferences.getState().tokens preferences.subscribe(({ tokens = [] }) => { this.tokens = tokens }) } /** * @type {Array} - Array of token objects with contract addresses */ set tokens (tokens) { this._tokens = tokens this.updateExchangeRates() } } module.exports = TokenRatesController