import {intervalUtils} from '@0xproject/utils'; import {BigNumber} from 'bignumber.js'; import {RBTree} from 'bintrees'; import * as _ from 'lodash'; import {ZeroExError} 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 orderHashByExpirationRBTree: RBTree; private expiration: {[orderHash: string]: BigNumber} = {}; private orderExpirationCheckingIntervalMs: number; private expirationMarginMs: number; private orderExpirationCheckingIntervalIdIfExists?: NodeJS.Timer; constructor(expirationMarginIfExistsMs?: number, orderExpirationCheckingIntervalIfExistsMs?: number) { this.expirationMarginMs = expirationMarginIfExistsMs || DEFAULT_EXPIRATION_MARGIN_MS; this.orderExpirationCheckingIntervalMs = expirationMarginIfExistsMs || DEFAULT_ORDER_EXPIRATION_CHECKING_INTERVAL_MS; const scoreFunction = (orderHash: string) => this.expiration[orderHash].toNumber(); const comparator = (lhs: string, rhs: string) => scoreFunction(lhs) - scoreFunction(rhs); this.orderHashByExpirationRBTree = new RBTree(comparator); } public subscribe(callback: (orderHash: string) => void): void { if (!_.isUndefined(this.orderExpirationCheckingIntervalIdIfExists)) { throw new Error(ZeroExError.SubscriptionAlreadyPresent); } this.orderExpirationCheckingIntervalIdIfExists = intervalUtils.setAsyncExcludingInterval( this.pruneExpiredOrders.bind(this, callback), this.orderExpirationCheckingIntervalMs, ); } public unsubscribe(): void { if (_.isUndefined(this.orderExpirationCheckingIntervalIdIfExists)) { throw new Error(ZeroExError.SubscriptionNotFound); } intervalUtils.clearAsyncExcludingInterval(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 { this.orderHashByExpirationRBTree.remove(orderHash); delete this.expiration[orderHash]; } private pruneExpiredOrders(callback: (orderHash: string) => void): void { const currentUnixTimestampMs = utils.getCurrentUnixTimestampMs(); while (true) { const hasTrakedOrders = this.orderHashByExpirationRBTree.size === 0; if (hasTrakedOrders) { 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); } } }