import { RateLimitInfo } from '../core/types.js';
import { RateLimitError } from './errors.js';
interface RateLimitState {
count: number;
resetAt: Date;
}
export class RateLimiter {
private state: RateLimitState;
private readonly limit: number;
private readonly windowMs: number;
constructor(limit: number = 50, windowMinutes: number = 1) {
this.limit = limit;
this.windowMs = windowMinutes * 60 * 1000;
this.state = {
count: 0,
resetAt: new Date(Date.now() + this.windowMs),
};
}
public async checkLimit(): Promise<void> {
const now = Date.now();
// Reset window if expired
if (now >= this.state.resetAt.getTime()) {
this.state = {
count: 0,
resetAt: new Date(now + this.windowMs),
};
}
// Check if limit exceeded
if (this.state.count >= this.limit) {
const waitTime = Math.ceil((this.state.resetAt.getTime() - now) / 1000);
throw new RateLimitError(
`Rate limit exceeded. Please wait ${waitTime} seconds before retrying.`,
waitTime
);
}
// Increment counter
this.state.count++;
}
public getRateLimitInfo(): RateLimitInfo {
const now = Date.now();
// Reset if window expired
if (now >= this.state.resetAt.getTime()) {
this.state = {
count: 0,
resetAt: new Date(now + this.windowMs),
};
}
return {
limit: this.limit,
remaining: Math.max(0, this.limit - this.state.count),
resetAt: this.state.resetAt,
};
}
public updateFromHeaders(headers: Record<string, any>): void {
// Freshdesk returns rate limit info in headers
const limit = headers['x-ratelimit-total'];
const remaining = headers['x-ratelimit-remaining'];
// const used = headers['x-ratelimit-used-current-request']; // For future use
if (limit && remaining !== undefined) {
this.state.count = this.limit - parseInt(remaining, 10);
}
}
public reset(): void {
this.state = {
count: 0,
resetAt: new Date(Date.now() + this.windowMs),
};
}
public getWaitTime(): number {
const now = Date.now();
if (this.state.count < this.limit) {
return 0;
}
return Math.max(0, this.state.resetAt.getTime() - now);
}
}
