import { MET_API_RATE_LIMIT_PER_SECOND } from '../constants.js';
class RateLimiter {
private requestsThisSecond: number = 0;
private lastRequestTime: number = Date.now();
private maxRequestsPerSecond: number;
private pending: Promise<void> = Promise.resolve();
constructor(maxRequestsPerSecond: number = MET_API_RATE_LIMIT_PER_SECOND) {
this.maxRequestsPerSecond = maxRequestsPerSecond;
}
async fetch(url: string, options?: RequestInit): Promise<Response> {
await this.acquireSlot();
return fetch(url, options);
}
private acquireSlot(): Promise<void> {
// Chain each caller onto the previous one so the counter
// check-and-increment is serialized across async boundaries.
this.pending = this.pending.then(() => this.waitIfNeeded());
return this.pending;
}
private async waitIfNeeded(): Promise<void> {
const now = Date.now();
// Reset counter if we're in a new second
if (now - this.lastRequestTime >= 1000) {
this.requestsThisSecond = 0;
this.lastRequestTime = now;
}
// If we've hit our limit, wait until the next second
if (this.requestsThisSecond >= this.maxRequestsPerSecond) {
// Note: Rate limiting is intentionally silent. Logging to stderr would leak
// implementation details to users in stdio mode.
const timeToWait = 1000 - (now - this.lastRequestTime);
if (timeToWait > 0) {
await new Promise(resolve => setTimeout(resolve, timeToWait));
}
// Reset after waiting
this.requestsThisSecond = 0;
this.lastRequestTime = Date.now();
}
// Increment counter
this.requestsThisSecond++;
}
}
// Create and export a singleton instance for Met Museum API
export const metMuseumRateLimiter = new RateLimiter();
