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import { BigNumber } from '@0x/utils';
// TODO: merge development and move to constants
const ENDPOINT_URL = 'https://ethgasstation.info/json/ethgasAPI.json';
const DEFAULT_GAS_PRICE_WEI = new BigNumber(20000000000);
interface GasStationResult {
average: number;
fastestWait: number;
fastWait: number;
fast: number;
safeLowWait: number;
blockNum: number;
avgWait: number;
block_time: number;
speed: number;
fastest: number;
safeLow: number;
}
const fetchFastAmountInWei = async () => {
const res = await fetch(ENDPOINT_URL);
const gasInfo = (await res.json()) as GasStationResult;
const gasPriceInGwei = new BigNumber(gasInfo.fast / 10);
return gasPriceInGwei.mul(1000000000);
};
export class GasPriceEstimator {
private _lastFetched?: BigNumber;
public async getFastAmountInWeiAsync(): Promise<BigNumber> {
let fetchedAmount: BigNumber | undefined;
try {
fetchedAmount = await fetchFastAmountInWei();
} catch {
fetchedAmount = undefined;
}
if (fetchedAmount) {
this._lastFetched = fetchedAmount;
}
return fetchedAmount || this._lastFetched || DEFAULT_GAS_PRICE_WEI;
}
}
export const gasPriceEstimator = new GasPriceEstimator();
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