60 lines
1.5 KiB
TypeScript
60 lines
1.5 KiB
TypeScript
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/**
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* In-memory sliding-window rate limiter.
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* Tracks request counts per IP per minute bucket.
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* Auto-evicts expired entries to prevent memory leaks.
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*/
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interface RateLimitEntry {
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count: number;
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expiresAt: number;
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}
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const store = new Map<string, RateLimitEntry>();
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// Evict expired entries periodically (every 60s)
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let lastCleanup = Date.now();
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const CLEANUP_INTERVAL = 60_000;
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function cleanup() {
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const now = Date.now();
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if (now - lastCleanup < CLEANUP_INTERVAL) return;
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lastCleanup = now;
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for (const [key, entry] of store) {
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if (now > entry.expiresAt) store.delete(key);
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}
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}
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/**
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* Check if a request should be allowed.
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* @param ip - Client IP address
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* @param maxRpm - Maximum requests per minute
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* @returns { success, remaining, resetAt (epoch ms) }
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*/
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export function checkRateLimit(
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ip: string,
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maxRpm: number,
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): { success: boolean; remaining: number; resetAt: number } {
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cleanup();
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const now = Date.now();
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const windowMs = 60_000;
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const key = `rl:${ip}`;
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const entry = store.get(key);
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// New window or expired
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if (!entry || now > entry.expiresAt) {
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const resetAt = now + windowMs;
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store.set(key, { count: 1, expiresAt: resetAt });
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return { success: true, remaining: maxRpm - 1, resetAt };
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}
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// Within window
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entry.count++;
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if (entry.count > maxRpm) {
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return { success: false, remaining: 0, resetAt: entry.expiresAt };
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}
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return { success: true, remaining: maxRpm - entry.count, resetAt: entry.expiresAt };
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}
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