/**
 * Minimal in-memory fixed-window rate limiter for a single Node process
 * (this app always runs as one process - see server.ts). Good enough to
 * blunt abuse of the email-verification resend endpoint without adding an
 * external store; resets on deploy/restart, which is an acceptable
 * trade-off for this use case.
 */
const buckets = new Map<string, { count: number; resetAt: number }>();

// Opportunistic cleanup so long-running processes don't accumulate an
// unbounded number of stale keys (one per distinct IP/email ever seen).
const MAX_TRACKED_KEYS = 5000;

function sweepExpired(now: number) {
  for (const [key, bucket] of buckets) {
    if (bucket.resetAt <= now) buckets.delete(key);
  }
}

export function checkRateLimit(key: string, opts: { max: number; windowMs: number }): boolean {
  const now = Date.now();
  if (buckets.size >= MAX_TRACKED_KEYS) sweepExpired(now);

  const bucket = buckets.get(key);
  if (!bucket || bucket.resetAt <= now) {
    if (!bucket && buckets.size >= MAX_TRACKED_KEYS) return false;
    buckets.set(key, { count: 1, resetAt: now + opts.windowMs });
    return true;
  }
  if (bucket.count >= opts.max) return false;
  bucket.count += 1;
  return true;
}

export function getClientIp(request: { headers: Headers }): string {
  // Deployment is always behind exactly one trusted reverse proxy (see
  // DEPLOYMENT.md - Nginx Proxy Manager; the app port isn't published
  // directly to the host). nginx's default `$proxy_add_x_forwarded_for`
  // *appends* the real client IP to any X-Forwarded-For it already
  // received rather than replacing it, so a directly-connecting client
  // could prepend arbitrary spoofed entries of their own. Only the
  // right-most (last) entry - the one the trusted proxy itself appended -
  // is trustworthy; taking the first entry would let a client bypass this
  // rate limit entirely by sending a fake X-Forwarded-For header.
  const forwarded = request.headers.get("x-forwarded-for");
  if (forwarded) {
    const parts = forwarded.split(",");
    return parts[parts.length - 1]!.trim();
  }
  return "unknown";
}