@aikidosec/firewall/ratelimiting/RateLimiter.js

Zen by Aikido is an embedded Application Firewall that autonomously protects Node.js apps against common and critical attacks, provides rate limiting, detects malicious traffic (including bots), and more.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.RateLimiter = void 0;
const LRUMap_1 = require("./LRUMap");
/**
 * Sliding window rate limiter implementation
 */
class RateLimiter {
    constructor(maxItems, timeToLiveInMS) {
        this.maxItems = maxItems;
        this.timeToLiveInMS = timeToLiveInMS;
        this.rateLimitedItems = new LRUMap_1.LRUMap(maxItems, timeToLiveInMS);
    }
    isAllowed(key, windowSizeInMS, maxRequests) {
        const currentTime = performance.now();
        const requestTimestamps = this.rateLimitedItems.get(key) || [];
        // Filter out timestamps that are older than windowSizeInMS and already expired
        const filteredTimestamps = requestTimestamps.filter((timestamp) => currentTime - timestamp <= windowSizeInMS);
        // Ensure the number of entries exceeds maxRequests by only 1
        if (filteredTimestamps.length > maxRequests + 1) {
            filteredTimestamps.splice(0, filteredTimestamps.length - (maxRequests + 1));
        }
        // Add current request timestamp to the list
        filteredTimestamps.push(currentTime);
        // Update the list of timestamps for the key
        this.rateLimitedItems.set(key, filteredTimestamps);
        // Check if the number of requests is less or equal to the maxRequests
        return filteredTimestamps.length <= maxRequests;
    }
}
exports.RateLimiter = RateLimiter;