Import source: backend/src/middleware/rateLimit

Import the existing local project snapshot. This commit organizes existing files; it does not represent newly developed functionality.

backend/src/middleware/rateLimit.ts

@@ -0,0 +1,38 @@
+import type { RequestHandler } from 'express';
+import { HttpError } from './errorHandler.js';
+
+const log = new Map<string, number[]>();
+
+// Prune entries older than 1 hour every 10 minutes
+setInterval(() => {
+  const cutoff = Date.now() - 3_600_000;
+  for (const [ip, ts] of log) {
+    const fresh = ts.filter((t) => t > cutoff);
+    if (fresh.length === 0) log.delete(ip);
+    else log.set(ip, fresh);
+  }
+}, 600_000).unref();
+
+/**
+ * Sliding-window rate limiter — in-memory, per IP.
+ * maxRequests allowed within windowMs milliseconds.
+ */
+export function rateLimit(maxRequests: number, windowMs: number): RequestHandler {
+  return (req, res, next) => {
+    const ip = req.ip ?? req.socket.remoteAddress ?? 'unknown';
+    const now = Date.now();
+    const windowStart = now - windowMs;
+
+    const timestamps = (log.get(ip) ?? []).filter((t) => t > windowStart);
+
+    if (timestamps.length >= maxRequests) {
+      const retryAfterSecs = Math.ceil((timestamps[0] - windowStart) / 1000);
+      res.setHeader('Retry-After', String(retryAfterSecs));
+      return next(new HttpError(429, 'RATE_LIMITED', `Too many requests — retry after ${retryAfterSecs}s`));
+    }
+
+    timestamps.push(now);
+    log.set(ip, timestamps);
+    next();
+  };
+}