feat: add rate limiter for API calls

src/utils/rate-limit.ts

@@ -0,0 +1,76 @@
+export interface RateLimitConfig {
+	maxRequests: number;
+	windowMs: number;
+}
+
+export class RateLimiter {
+	private timestamps: number[] = [];
+	private config: RateLimitConfig;
+
+	constructor(config: Partial<RateLimitConfig> = {}) {
+		this.config = {
+			maxRequests: config.maxRequests ?? 10,
+			windowMs: config.windowMs ?? 60000,
+		};
+	}
+
+	tryAcquire(): boolean {
+		const now = Date.now();
+		this.timestamps = this.timestamps.filter((t) => now - t < this.config.windowMs);
+
+		if (this.timestamps.length < this.config.maxRequests) {
+			this.timestamps.push(now);
+			return true;
+		}
+		return false;
+	}
+
+	remainingRequests(): number {
+		const now = Date.now();
+		const active = this.timestamps.filter((t) => now - t < this.config.windowMs);
+		return this.config.maxRequests - active.length;
+	}
+
+	async waitForSlot(): Promise<void> {
+		while (!this.tryAcquire()) {
+			const oldest = this.timestamps[0]!;
+			const waitMs = this.config.windowMs - (Date.now() - oldest);
+			await new Promise((resolve) => setTimeout(resolve, waitMs));
+		}
+	}
+
+	reset(windowMs?: number) {
+		this.timestamps = [];
+		if (windowMs) {
+			this.config.windowMs = windowMs;
+		}
+	}
+}
+
+export function parseRateLimit(header: string): RateLimitConfig | null {
+	const parts = header.split(",");
+	let maxRequests: number | null = null;
+	let windowMs: number | null = null;
+
+	for (const part of parts) {
+		const eqIdx = part.indexOf("=");
+		if (eqIdx === -1) continue;
+		const key = part.substring(0, eqIdx).trim();
+		const val = part.substring(eqIdx + 1);
+		switch (key) {
+			case "limit": {
+				const parsed = parseInt(val, 10);
+				if (!Number.isNaN(parsed)) maxRequests = parsed;
+				break;
+			}
+			case "window": {
+				const parsed = parseInt(val, 10);
+				if (!Number.isNaN(parsed)) windowMs = parsed * 1000;
+				break;
+			}
+		}
+	}
+
+	if (maxRequests !== null && windowMs !== null) return { maxRequests, windowMs };
+	return null;
+}