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import { BlockParamLiteral, LogEntry } from '@0xproject/types';
import { intervalUtils } from '@0xproject/utils';
import { Web3Wrapper } from '@0xproject/web3-wrapper';
import { Block, BlockAndLogStreamer, Log } from 'ethereumjs-blockstream';
import * as _ from 'lodash';
import { EventWatcherCallback, OrderWatcherError } from '../types';
import { assert } from '../utils/assert';
const DEFAULT_EVENT_POLLING_INTERVAL_MS = 200;
enum LogEventState {
Removed,
Added,
}
/**
* The EventWatcher watches for blockchain events at the specified block confirmation
* depth.
*/
export class EventWatcher {
private _web3Wrapper: Web3Wrapper;
private _blockAndLogStreamerIfExists: BlockAndLogStreamer<Block, Log> | undefined;
private _blockAndLogStreamIntervalIfExists?: NodeJS.Timer;
private _onLogAddedSubscriptionToken: string | undefined;
private _onLogRemovedSubscriptionToken: string | undefined;
private _pollingIntervalMs: number;
private _stateLayer: BlockParamLiteral;
private static _onBlockAndLogStreamerError(callback: EventWatcherCallback, err: Error): void {
// Propogate all Blockstream subscriber errors to
// top-level subscription
callback(err);
}
constructor(
web3Wrapper: Web3Wrapper,
pollingIntervalIfExistsMs: undefined | number,
stateLayer: BlockParamLiteral = BlockParamLiteral.Latest,
) {
this._web3Wrapper = web3Wrapper;
this._stateLayer = stateLayer;
this._pollingIntervalMs = _.isUndefined(pollingIntervalIfExistsMs)
? DEFAULT_EVENT_POLLING_INTERVAL_MS
: pollingIntervalIfExistsMs;
this._blockAndLogStreamerIfExists = undefined;
this._blockAndLogStreamIntervalIfExists = undefined;
this._onLogAddedSubscriptionToken = undefined;
this._onLogRemovedSubscriptionToken = undefined;
}
public subscribe(callback: EventWatcherCallback): void {
assert.isFunction('callback', callback);
if (!_.isUndefined(this._blockAndLogStreamIntervalIfExists)) {
throw new Error(OrderWatcherError.SubscriptionAlreadyPresent);
}
this._startBlockAndLogStream(callback);
}
public unsubscribe(): void {
if (!_.isUndefined(this._blockAndLogStreamIntervalIfExists)) {
intervalUtils.clearAsyncExcludingInterval(this._blockAndLogStreamIntervalIfExists);
delete this._blockAndLogStreamIntervalIfExists;
delete this._blockAndLogStreamerIfExists;
}
}
private _startBlockAndLogStream(callback: EventWatcherCallback): void {
if (!_.isUndefined(this._blockAndLogStreamerIfExists)) {
throw new Error(OrderWatcherError.SubscriptionAlreadyPresent);
}
this._blockAndLogStreamerIfExists = new BlockAndLogStreamer(
this._web3Wrapper.getBlockAsync.bind(this._web3Wrapper),
this._web3Wrapper.getLogsAsync.bind(this._web3Wrapper),
EventWatcher._onBlockAndLogStreamerError.bind(this, callback),
);
const catchAllLogFilter = {};
this._blockAndLogStreamerIfExists.addLogFilter(catchAllLogFilter);
this._blockAndLogStreamIntervalIfExists = intervalUtils.setAsyncExcludingInterval(
this._reconcileBlockAsync.bind(this),
this._pollingIntervalMs,
this._onReconcileBlockError.bind(this, callback),
);
let isRemoved = false;
this._onLogAddedSubscriptionToken = this._blockAndLogStreamerIfExists.subscribeToOnLogAdded(
this._onLogStateChangedAsync.bind(this, callback, isRemoved),
);
isRemoved = true;
this._onLogRemovedSubscriptionToken = this._blockAndLogStreamerIfExists.subscribeToOnLogRemoved(
this._onLogStateChangedAsync.bind(this, callback, isRemoved),
);
}
private _onReconcileBlockError(callback: EventWatcherCallback, err: Error): void {
this.unsubscribe();
callback(err);
}
private async _onLogStateChangedAsync(
callback: EventWatcherCallback,
isRemoved: boolean,
log: LogEntry,
): Promise<void> {
await this._emitDifferencesAsync(log, isRemoved ? LogEventState.Removed : LogEventState.Added, callback);
}
private async _reconcileBlockAsync(): Promise<void> {
const latestBlock = await this._web3Wrapper.getBlockAsync(BlockParamLiteral.Latest);
// We need to coerce to Block type cause Web3.Block includes types for mempool blocks
if (!_.isUndefined(this._blockAndLogStreamerIfExists)) {
// If we clear the interval while fetching the block - this._blockAndLogStreamer will be undefined
await this._blockAndLogStreamerIfExists.reconcileNewBlock((latestBlock as any) as Block);
}
}
private async _emitDifferencesAsync(
log: LogEntry,
logEventState: LogEventState,
callback: EventWatcherCallback,
): Promise<void> {
const logEvent = {
removed: logEventState === LogEventState.Removed,
...log,
};
if (!_.isUndefined(this._blockAndLogStreamIntervalIfExists)) {
callback(null, logEvent);
}
}
}
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