zenin-limiter/dist/index.d.ts

Universal rate & throttle limiter middleware for Express, Fastify, and custom handlers

import { Request, Response, NextFunction } from 'express';
import { FastifyRequest, FastifyReply } from 'fastify';
import { CanActivate, ExecutionContext } from '@nestjs/common';

interface LimiterConfig {
    /**
     * Key generator system for rate limiting.
     * - keyType: 'ip' | 'user-agent' | 'header:X-API-KEY' | 'path' | 'custom'
     * - headerName: Used if keyType is a header
     * - customKeyGenerator: Custom function for key extraction
     */
    keyType?: "ip" | "user-agent" | "header:X-API-KEY" | "path" | "custom";
    headerName?: string;
    customKeyGenerator?: (req: any) => string;
    /**
     * Maximum number of allowed actions (requests) within the defined time window.
     * Can be a number or a function that returns a number based on request context.
     * Default: 100
     */
    limit?: number | ((req: any) => number);
    /**
     * Duration of the rate limit window in seconds.
     * Default: 60
     * Example: `60` means "limit X requests per 60 seconds".
     */
    windowInSeconds?: number;
    /**
     * Rate limiting strategy to use.
     * - 'fixed': Simple fixed window (default)
     * - 'sliding': Accurate sliding window
     * - 'tokenBucket': Smooth burst control
     */
    strategy?: "fixed" | "sliding" | "tokenBucket";
    /**
     * Event hooks for monitoring and debugging.
     */
    onLimitReached?: (key: string, req?: any) => void;
    onReset?: (key: string) => void;
    onPass?: (key: string, req?: any) => void;
    onError?: (error: Error) => void;
    /**
     * Enable debug logging for all rate limiting decisions.
     */
    debug?: boolean;
    /**
     * Dry run mode - simulate rate limiting without actually blocking requests.
     */
    dryRun?: boolean;
    /**
     * Silent mode - log decisions but don't block requests.
     */
    silent?: boolean;
    /**
     * Configuration for rate limiter.
     * This includes settings for memory store, cleanup intervals, and more.
     * If not provided, defaults will be used.
     *
     *  Max number of keys (default: 1,000,000)
     * Calls between cleanups (default: 1000)
     * Enable per-key metrics (default: false)
     * Max keys to clean per batch (default: 1000)
     */
    limiterConfig?: RateLimiterConfig;
}
type RateLimiterConfig = {
    maxStoreSize?: number;
    cleanupInterval?: number;
    enablePerKeyStats?: boolean;
    maxBatchCleanup?: number;
};
interface RateLimitStrategy {
    isAllowed(key: string, req?: any): boolean | Promise<boolean>;
    getState?(key: string): RateLimitState | Promise<RateLimitState>;
    reset?(key: string): void | Promise<void>;
}
type RateLimitState = {
    remaining: number;
    resetAt: number;
    limit: number;
};

/**
 * Express middleware for rate limiting.
 */
declare function expressLimiter(config: Partial<LimiterConfig>): (req: Request, res: Response, next: NextFunction) => Promise<Response<any, Record<string, any>>>;

declare function fastifyLimiter(config: Partial<LimiterConfig>): (req: FastifyRequest, reply: FastifyReply) => Promise<void>;

declare function RateLimit(config: LimiterConfig): (target: any, propertyKey: string, descriptor: PropertyDescriptor) => PropertyDescriptor;
declare class NestLimiterGuard implements CanActivate {
    private readonly config;
    private limiter;
    private keyFn;
    constructor(config: Partial<LimiterConfig>);
    canActivate(context: ExecutionContext): Promise<boolean>;
}
declare class RateLimitModule {
}

declare function universalLimiter(config: Partial<LimiterConfig>): (req: any, res: any, next: () => void) => Promise<any>;

/**
 * Resets the rate limit for a specific key.
 * @param key The key to reset
 * @throws Error if key is invalid
 */
declare function resetKey(key: string): Promise<void>;
/**
 * Resets all rate limit state.
 */
declare function resetAll(): Promise<void>;
/**
 * Returns current rate limit metrics.
 * @param key Optional key for per-key stats
 * @returns Object containing hits and rejections (global or per-key)
 */
declare function getMetrics(key?: string): Promise<{
    hits: number;
    rejections: number;
}>;
/**
 * Checks if a key is allowed based on rate limit.
 * Uses a min-heap for expirations, LRU for memory capping, and Promise-based locking.
 * Handles millions of users with hybrid cleanup (on-demand + periodic).
 * @param key Unique identifier for rate limiting
 * @param limit Maximum requests allowed in window
 * @param windowInSeconds Time window in seconds
 * @param config Optional configuration (maxStoreSize, cleanupInterval, enablePerKeyStats, maxBatchCleanup)
 * @param now Optional time source for testing (defaults to Date.now)
 * @returns True if allowed, false if rate limit exceeded
 * @throws Error if inputs are invalid
 */
declare function isAllowedMemory(key: string, limit: number, windowInSeconds: number, config?: RateLimiterConfig, now?: () => number): Promise<boolean>;

declare class FixedWindowStrategy implements RateLimitStrategy {
    private config;
    private maxEntries;
    private gcStarted;
    private getLimitFn?;
    constructor(config: any);
    private getLimit;
    private startGC;
    stopGC(): void;
    isAllowed(key: string, req?: any): Promise<boolean>;
    reset(key: string): Promise<void>;
    getState(key: string): Promise<RateLimitState>;
    static resetAll(): Promise<void>;
}

interface RateLimiterStats {
    totalRequests: number;
    hits: number;
    rejections: number;
    activeKeys: number;
    memoryUsage?: number;
}
declare class RateLimiter {
    private strategy;
    private config;
    private stats;
    constructor(config: Partial<LimiterConfig>, strategy?: RateLimitStrategy);
    private createStrategy;
    private getLimit;
    private callHook;
    private logDebug;
    isAllowed(key: string, req?: any): Promise<boolean>;
    reset(key: string): Promise<void>;
    getState(key: string): Promise<any>;
    getStats(): RateLimiterStats;
    private getActiveKeysCount;
}

declare class SlidingWindowStrategy implements RateLimitStrategy {
    private limit;
    private windowMs;
    private config;
    private maxEntries;
    private gcStarted;
    private getLimitFn?;
    constructor(config: any);
    private startGC;
    stopGC(): void;
    private getLimit;
    isAllowed(key: string, req?: any): Promise<boolean>;
    getState(key: string, req?: any): Promise<RateLimitState>;
    reset(key: string): Promise<void>;
    static resetAll(): Promise<void>;
}

declare class TokenBucketStrategy implements RateLimitStrategy {
    private capacity;
    private refillRate;
    private config;
    private maxEntries;
    private gcStarted;
    private getLimitFn?;
    constructor(config: any);
    private startGC;
    stopGC(): void;
    private getLimit;
    isAllowed(key: string, req?: any): Promise<boolean>;
    getState(key: string, req?: any): Promise<RateLimitState>;
    reset(key: string): Promise<void>;
    static resetAll(): Promise<void>;
}

declare function applyDefaults(config: Partial<LimiterConfig>): LimiterConfig;

interface ValidationError {
    field: string;
    message: string;
}
declare function validateConfig(config: LimiterConfig): ValidationError[];
declare function throwIfInvalid(config: LimiterConfig): void;

export { FixedWindowStrategy, type LimiterConfig, NestLimiterGuard, RateLimit, RateLimitModule, type RateLimitState, type RateLimitStrategy, RateLimiter, type RateLimiterConfig, type RateLimiterStats, SlidingWindowStrategy, TokenBucketStrategy, applyDefaults, expressLimiter, fastifyLimiter, getMetrics, isAllowedMemory, resetAll, resetKey, throwIfInvalid, universalLimiter, validateConfig };