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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
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