import { DurableObject } from 'cloudflare:workers';
import type { Env } from '../env.js';
interface RateLimitState {
count: number;
windowStart: number;
}
/**
* RateLimiter Durable Object
*
* Implements distributed rate limiting using sliding window algorithm.
* Each client gets their own Durable Object instance for rate tracking.
*/
export class RateLimiter extends DurableObject<Env> {
private state: RateLimitState = { count: 0, windowStart: 0 };
constructor(ctx: DurableObjectState, env: Env) {
super(ctx, env);
}
/**
* Check if request should be rate limited
*/
async checkLimit(limit: number, windowMs: number): Promise<{ allowed: boolean; remaining: number; resetAt: number }> {
const now = Date.now();
// Reset window if expired
if (now - this.state.windowStart >= windowMs) {
this.state = { count: 0, windowStart: now };
}
// Check if under limit
if (this.state.count < limit) {
this.state.count++;
await this.ctx.storage.put('state', this.state);
return {
allowed: true,
remaining: limit - this.state.count,
resetAt: this.state.windowStart + windowMs,
};
}
return {
allowed: false,
remaining: 0,
resetAt: this.state.windowStart + windowMs,
};
}
/**
* Handle incoming requests
*/
async fetch(request: Request): Promise<Response> {
const url = new URL(request.url);
const limit = parseInt(url.searchParams.get('limit') || '60', 10);
const windowMs = parseInt(url.searchParams.get('window') || '60000', 10);
const result = await this.checkLimit(limit, windowMs);
return new Response(JSON.stringify(result), {
status: result.allowed ? 200 : 429,
headers: {
'Content-Type': 'application/json',
'X-RateLimit-Remaining': String(result.remaining),
'X-RateLimit-Reset': String(result.resetAt),
},
});
}
}
