@aikidosec/firewall/ratelimiting/LRUMap.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.LRUMap = void 0;
class LRUMap {
    constructor(max = 1000, ttlInMsecs = 0) {
        if (isNaN(max) || max < 0) {
            throw new Error("Invalid max value");
        }
        if (isNaN(ttlInMsecs) || ttlInMsecs < 0) {
            throw new Error("Invalid ttl value");
        }
        this.first = null;
        this.items = new Map();
        this.last = null;
        this.max = max;
        this.ttl = ttlInMsecs;
    }
    get size() {
        return this.items.size;
    }
    bumpLru(item) {
        if (this.last === item) {
            return; // Item is already the last one, no need to bump
        }
        const last = this.last;
        const next = item.next;
        const prev = item.prev;
        if (this.first === item) {
            this.first = next;
        }
        item.next = null;
        item.prev = last;
        if (last)
            last.next = item;
        if (prev !== null) {
            prev.next = next;
        }
        if (next !== null) {
            next.prev = prev;
        }
        this.last = item;
    }
    clear() {
        this.items = new Map();
        this.first = null;
        this.last = null;
    }
    delete(key) {
        if (this.items.has(key)) {
            const item = this.items.get(key);
            this.items.delete(key);
            if (item.prev !== null) {
                item.prev.next = item.next;
            }
            if (item.next !== null) {
                item.next.prev = item.prev;
            }
            if (this.first === item) {
                this.first = item.next;
            }
            if (this.last === item) {
                this.last = item.prev;
            }
        }
    }
    evict() {
        if (this.size > 0) {
            const item = this.first;
            this.items.delete(item.key);
            if (this.size === 0) {
                this.first = null;
                this.last = null;
            }
            else {
                this.first = item.next;
                if (this.first)
                    this.first.prev = null;
            }
        }
    }
    get(key) {
        if (this.items.has(key)) {
            const item = this.items.get(key);
            // Item has already expired
            if (this.ttl > 0 && item.expiry <= performance.now()) {
                this.delete(key);
                return;
            }
            // Item is still fresh
            this.bumpLru(item);
            return item.value;
        }
    }
    keys() {
        return this.items.keys();
    }
    set(key, value) {
        // Replace existing item
        if (this.items.has(key)) {
            const item = this.items.get(key);
            item.value = value;
            item.expiry = this.ttl > 0 ? performance.now() + this.ttl : this.ttl;
            if (this.last !== item) {
                this.bumpLru(item);
            }
            return;
        }
        // Add new item
        if (this.max > 0 && this.size === this.max) {
            this.evict();
        }
        const item = {
            expiry: this.ttl > 0 ? performance.now() + this.ttl : this.ttl,
            key: key,
            prev: this.last,
            next: null,
            value,
        };
        this.items.set(key, item);
        if (this.size === 1) {
            this.first = item;
        }
        else {
            if (this.last)
                this.last.next = item;
        }
        this.last = item;
    }
}
exports.LRUMap = LRUMap;