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import * as Web3 from 'web3';
import * as _ from 'lodash';
import {Web3Wrapper} from '../web3_wrapper';
import {BlockParamLiteral, EventCallback, MempoolEventCallback} from '../types';
import {AbiDecoder} from '../utils/abi_decoder';
import {intervalUtils} from '../utils/interval_utils';
const DEFAULT_MEMPOOL_POLLING_INTERVAL = 200;
export class EventWatcher {
private _web3Wrapper: Web3Wrapper;
private _pollingIntervalMs: number;
private _intervalId: NodeJS.Timer;
private _lastMempoolEvents: Web3.LogEntry[] = [];
private _callback?: MempoolEventCallback;
constructor(web3Wrapper: Web3Wrapper, pollingIntervalMs: undefined|number) {
this._web3Wrapper = web3Wrapper;
this._pollingIntervalMs = _.isUndefined(pollingIntervalMs) ?
DEFAULT_MEMPOOL_POLLING_INTERVAL :
pollingIntervalMs;
}
public subscribe(callback: MempoolEventCallback): void {
this._callback = callback;
this._intervalId = intervalUtils.setAsyncExcludingInterval(
this._pollForMempoolEventsAsync.bind(this), this._pollingIntervalMs);
}
public unsubscribe(): void {
delete this._callback;
this._lastMempoolEvents = [];
intervalUtils.clearAsyncExcludingInterval(this._intervalId);
}
private async _pollForMempoolEventsAsync(): Promise<void> {
const pendingEvents = await this._getMempoolEventsAsync();
if (pendingEvents.length === 0) {
// HACK: Sometimes when node rebuilds the pending block we get back the empty result.
// We don't want to emit a lot of removal events and bring them back after a couple of miliseconds,
// that's why we just ignore those cases.
return;
}
const removedEvents = _.differenceBy(this._lastMempoolEvents, pendingEvents, JSON.stringify);
const newEvents = _.differenceBy(pendingEvents, this._lastMempoolEvents, JSON.stringify);
let isRemoved = true;
this._emitDifferences(removedEvents, isRemoved);
isRemoved = false;
this._emitDifferences(newEvents, isRemoved);
this._lastMempoolEvents = pendingEvents;
}
private async _getMempoolEventsAsync(): Promise<Web3.LogEntry[]> {
const mempoolFilter = {
fromBlock: BlockParamLiteral.Pending,
toBlock: BlockParamLiteral.Pending,
};
const pendingEvents = await this._web3Wrapper.getLogsAsync(mempoolFilter);
return pendingEvents;
}
private _emitDifferences(logs: Web3.LogEntry[], isRemoved: boolean): void {
_.forEach(logs, log => {
const logEvent = {
removed: isRemoved,
...log,
};
if (!_.isUndefined(this._callback)) {
this._callback(logEvent);
}
});
}
}
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