import { afterEach, describe, expect, test, vi } from 'vitest';
import { createSlidingWindowLimiter, clientIp } from '@/lib/qa/rate-limit';

describe('createSlidingWindowLimiter', () => {
  test('allows up to max requests per window, then blocks with retryAfterMs', () => {
    const limiter = createSlidingWindowLimiter({ windowMs: 1000, max: 2 });
    const now = 1_000_000;

    expect(limiter.check('ip-1', now).allowed).toBe(true);
    expect(limiter.check('ip-1', now + 10).allowed).toBe(true);
    expect(limiter.check('ip-1', now + 20)).toMatchObject({ allowed: false, remaining: 0 });

    // Different key is independent.
    expect(limiter.check('ip-2', now + 30).allowed).toBe(true);

    // Oldest hit leaves the window → allowed again.
    expect(limiter.check('ip-1', now + 1001).allowed).toBe(true);
  });

  test('reports retryAfterMs based on the oldest hit', () => {
    const limiter = createSlidingWindowLimiter({ windowMs: 1000, max: 1 });
    const now = 5_000_000;
    limiter.check('ip', now);
    const decision = limiter.check('ip', now + 400);
    expect(decision.allowed).toBe(false);
    expect(decision.retryAfterMs).toBe(600);
  });

  test('clear drops all state', () => {
    const limiter = createSlidingWindowLimiter({ windowMs: 1000, max: 1 });
    limiter.check('ip');
    limiter.clear();
    expect(limiter.check('ip').allowed).toBe(true);
  });

  test('uses one shared overflow bucket instead of growing beyond maxKeys', () => {
    const limiter = createSlidingWindowLimiter({ windowMs: 60_000, max: 2, maxKeys: 3 });
    const now = 1_000_000;

    expect(limiter.check('ip-1', now).allowed).toBe(true);
    expect(limiter.check('ip-2', now).allowed).toBe(true);
    expect(limiter.check('ip-3', now).allowed).toBe(true);
    expect(limiter.check('ip-4', now + 1).allowed).toBe(true);
    expect(limiter.check('ip-5', now + 2).allowed).toBe(false);
    expect(limiter.size()).toBe(3);
  });
});

describe('clientIp', () => {
  const headers = new Headers();
  const request = { headers, ip: undefined };

  afterEach(() => {
    vi.unstubAllEnvs();
    headers.delete('x-forwarded-for');
    headers.delete('x-real-ip');
  });

  test('uses x-forwarded-for first hop only behind an explicitly trusted proxy', () => {
    vi.stubEnv('LEARNER_RATE_LIMIT_TRUST_PROXY_HEADERS', 'true');
    headers.set('x-forwarded-for', '203.0.113.9, 10.0.0.1');
    expect(clientIp(request)).toBe('203.0.113.9');
  });

  test('ignores spoofable forwarding headers by default', () => {
    headers.set('x-forwarded-for', '203.0.113.9');
    headers.set('x-real-ip', '198.51.100.7');
    expect(clientIp({ headers, ip: '127.0.0.1' })).toBe('127.0.0.1');
    expect(clientIp({ headers, ip: undefined })).toBe('unknown');
  });

  test('falls back from trusted x-real-ip to request ip then unknown', () => {
    vi.stubEnv('LEARNER_RATE_LIMIT_TRUST_PROXY_HEADERS', 'true');
    headers.set('x-real-ip', '198.51.100.7');
    expect(clientIp(request)).toBe('198.51.100.7');
    headers.delete('x-real-ip');
    expect(clientIp({ headers, ip: '127.0.0.1' })).toBe('127.0.0.1');
    expect(clientIp({ headers, ip: undefined })).toBe('unknown');
  });
});