rateLimiter.ts

/*!
 * Copyright (c) Microsoft Corporation and contributors. All rights reserved.
 * Licensed under the MIT License.
 */

/**
 * A rate limiter to make sure that a client can only request help for one task within a time window.
 *
 * @deprecated This class has no replacement.
 *
 * @privateremarks
 * This class is not used anywhere in the repo. driver-utils already has a similar class that is used by the odsp and
 * routerlicious drivers.
 * @internal
 */
export class RateLimiter {
	private readonly requestMap = new Map<string, number>();

	/**
	 * Creates a rate limiter that keep track of the request it has made
	 *
	 * @param windowMSec - time in millisecond, use to filter out messages
	 * for a clientId if the last request falls within this time window
	 */
	constructor(private readonly windowMSec: number) {}

	/**
	 * Filter out the messages that had already been requested within the time window
	 *
	 * @param clientId - the clientId who want to send the message
	 * @param messages - the message we want to send
	 * @returns the message we approved to send that hasn't been sent recently
	 */
	public filter(clientId: string, messages: string[]): string[] {
		const approvedList: string[] = [];
		const currentTime = Date.now();

		for (const message of messages) {
			const key = `${clientId}/${message}`;
			if (!this.requestMap.has(key)) {
				this.requestMap.set(key, currentTime);
				approvedList.push(message);
				// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
			} else if (this.requestMap.get(key)! + this.windowMSec > currentTime) {
				continue;
			} else {
				this.requestMap.set(key, currentTime);
				approvedList.push(message);
			}
		}

		return approvedList;
	}
}