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import { BigNumber, intervalUtils } from '@0x/utils';
import { RBTree } from 'bintrees';
import * as _ from 'lodash';
import { OrderWatcherError } from '../types';
import { utils } from '../utils/utils';
const DEFAULT_EXPIRATION_MARGIN_MS = 0;
const DEFAULT_ORDER_EXPIRATION_CHECKING_INTERVAL_MS = 50;
/**
* This class includes the functionality to detect expired orders.
* It stores them in a min heap by expiration time and checks for expired ones every `orderExpirationCheckingIntervalMs`
*/
export class ExpirationWatcher {
private readonly _orderHashByExpirationRBTree: RBTree<string>;
private readonly _expiration: { [orderHash: string]: BigNumber } = {};
private readonly _orderExpirationCheckingIntervalMs: number;
private readonly _expirationMarginMs: number;
private _orderExpirationCheckingIntervalIdIfExists?: NodeJS.Timer;
constructor(expirationMarginIfExistsMs?: number, orderExpirationCheckingIntervalIfExistsMs?: number) {
this._orderExpirationCheckingIntervalMs =
orderExpirationCheckingIntervalIfExistsMs || DEFAULT_ORDER_EXPIRATION_CHECKING_INTERVAL_MS;
this._expirationMarginMs = expirationMarginIfExistsMs || DEFAULT_EXPIRATION_MARGIN_MS;
this._orderExpirationCheckingIntervalMs =
expirationMarginIfExistsMs || DEFAULT_ORDER_EXPIRATION_CHECKING_INTERVAL_MS;
const comparator = (lhsOrderHash: string, rhsOrderHash: string) => {
const lhsExpiration = this._expiration[lhsOrderHash].toNumber();
const rhsExpiration = this._expiration[rhsOrderHash].toNumber();
if (lhsExpiration !== rhsExpiration) {
return lhsExpiration - rhsExpiration;
} else {
// HACK: If two orders have identical expirations, the order in which they are emitted by the
// ExpirationWatcher does not matter, so we emit them in alphabetical order by orderHash.
return lhsOrderHash.localeCompare(rhsOrderHash);
}
};
this._orderHashByExpirationRBTree = new RBTree(comparator);
}
public subscribe(callback: (orderHash: string) => void): void {
if (!_.isUndefined(this._orderExpirationCheckingIntervalIdIfExists)) {
throw new Error(OrderWatcherError.SubscriptionAlreadyPresent);
}
this._orderExpirationCheckingIntervalIdIfExists = intervalUtils.setInterval(
this._pruneExpiredOrders.bind(this, callback),
this._orderExpirationCheckingIntervalMs,
_.noop.bind(_), // _pruneExpiredOrders never throws
);
}
public unsubscribe(): void {
if (_.isUndefined(this._orderExpirationCheckingIntervalIdIfExists)) {
throw new Error(OrderWatcherError.SubscriptionNotFound);
}
intervalUtils.clearInterval(this._orderExpirationCheckingIntervalIdIfExists);
delete this._orderExpirationCheckingIntervalIdIfExists;
}
public addOrder(orderHash: string, expirationUnixTimestampMs: BigNumber): void {
this._expiration[orderHash] = expirationUnixTimestampMs;
this._orderHashByExpirationRBTree.insert(orderHash);
}
public removeOrder(orderHash: string): void {
if (_.isUndefined(this._expiration[orderHash])) {
return; // noop since order already removed
}
this._orderHashByExpirationRBTree.remove(orderHash);
delete this._expiration[orderHash];
}
private _pruneExpiredOrders(callback: (orderHash: string) => void): void {
const currentUnixTimestampMs = utils.getCurrentUnixTimestampMs();
while (true) {
const hasNoTrackedOrders = this._orderHashByExpirationRBTree.size === 0;
if (hasNoTrackedOrders) {
break;
}
const nextOrderHashToExpire = this._orderHashByExpirationRBTree.min();
const hasNoExpiredOrders = this._expiration[nextOrderHashToExpire].greaterThan(
currentUnixTimestampMs.plus(this._expirationMarginMs),
);
const isSubscriptionActive = _.isUndefined(this._orderExpirationCheckingIntervalIdIfExists);
if (hasNoExpiredOrders || isSubscriptionActive) {
break;
}
const orderHash = this._orderHashByExpirationRBTree.min();
this._orderHashByExpirationRBTree.remove(orderHash);
delete this._expiration[orderHash];
callback(orderHash);
}
}
}
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