/**
 * In-memory sliding window rate limiter.
 * Single-instance, single-user container — no need for Redis.
 */

interface RateLimitEntry {
  timestamps: number[];
}

const store = new Map<string, RateLimitEntry>();

const WINDOW_MS = 60 * 1000; // 1 minute
const MAX_REQUESTS = 10;

export function checkRateLimit(
  key: string,
  options: { windowMs?: number; maxRequests?: number } = {}
): { allowed: boolean; retryAfterMs: number } {
  const now = Date.now();
  const windowMs = options.windowMs ?? WINDOW_MS;
  const maxRequests = options.maxRequests ?? MAX_REQUESTS;
  const entry = store.get(key) ?? { timestamps: [] };

  // Remove timestamps outside the window
  entry.timestamps = entry.timestamps.filter((t) => now - t < windowMs);

  if (entry.timestamps.length >= maxRequests) {
    const oldestInWindow = entry.timestamps[0];
    const retryAfterMs = windowMs - (now - oldestInWindow);
    return { allowed: false, retryAfterMs };
  }

  entry.timestamps.push(now);
  store.set(key, entry);
  return { allowed: true, retryAfterMs: 0 };
}