nuxt-app/server/service/auth/lib/rate-limit.ts

// In-memory rate limiter keyed by IP
const loginAttempts = new Map<
  string,
  { count: number; resetAt: number }
>();

const WINDOW_MS = 60_000;       // 1 minute window
const MAX_ATTEMPTS = 5;         // max 5 attempts per window
const LOCKOUT_MS = 15 * 60_000; // 15 minute lockout

function cleanupExpired(now: number): void {
  for (const [ip, entry] of loginAttempts.entries()) {
    if (now > entry.resetAt) {
      loginAttempts.delete(ip);
    }
  }
}

export function checkRateLimit(ip: string): {
  allowed: boolean;
  retryAfterMs: number;
} {
  const now = Date.now();
  cleanupExpired(now);
  const entry = loginAttempts.get(ip);

  if (!entry || now > entry.resetAt) {
    loginAttempts.set(ip, { count: 1, resetAt: now + WINDOW_MS });
    return { allowed: true, retryAfterMs: 0 };
  }

  if (entry.count >= MAX_ATTEMPTS) {
    return {
      allowed: false,
      retryAfterMs: entry.resetAt - now,
    };
  }

  entry.count++;
  return { allowed: true, retryAfterMs: 0 };
}

export function clearRateLimit(ip: string): void {
  loginAttempts.delete(ip);
}