/**
 * Tests for createRouteLimiter and the integration shape used by api.ts.
 *
 * Closes the U4 test gap (CodeQL js/missing-rate-limiting). Without these,
 * a refactor that drops the limiter middleware from any route would silently
 * regress and CodeQL would re-fire — but no test would fail before reaching
 * CI.
 *
 * Two layers of coverage:
 *   1. Helper unit tests — createRouteLimiter returns distinct middleware
 *      per call, has the right signature, exposes the right error shape.
 *   2. Integration tests — mount the same factory on a tiny isolated express
 *      app that does fs.readFile (the exact CodeQL sink class) and prove the
 *      429 fires after the configured limit. windowMs (2 000 ms) is generous
 *      enough that 4 sequential requests fit inside one window even on slow
 *      Windows CI runners; each test uses a fresh limiter so counter state
 *      never carries between tests.
 */
import { afterAll, afterEach, beforeAll, beforeEach, describe, expect, it } from 'vitest';
import express, { type Express } from 'express';
import http from 'node:http';
import path from 'node:path';
import fs from 'node:fs/promises';
import os from 'node:os';
import { createRouteLimiter } from '../../src/server/validation.js';

let tmpFile: string;

beforeAll(async () => {
  // Real fs.readFile target so the route does the same kind of FS work
  // the production routes do — keeps the test honest about what it covers.
  tmpFile = path.join(
    await fs.mkdtemp(path.join(os.tmpdir(), 'gitnexus-ratelimit-')),
    'fixture.txt',
  );
  await fs.writeFile(tmpFile, 'hello\n', 'utf-8');
});

afterAll(async () => {
  await fs.rm(path.dirname(tmpFile), { recursive: true, force: true });
});

// Build a fresh app + server per test so counter state never carries between
// tests. windowMs = 2 000 ms gives ample headroom for Windows CI where
// sequential loopback HTTP requests can take 50–80 ms each.
const buildApp = (limit: number, windowMs = 2000): Express => {
  const app = express();
  app.set('trust proxy', 'loopback, linklocal, uniquelocal');
  app.get('/test/file', createRouteLimiter({ windowMs, limit }), async (_req, res) => {
    const content = await fs.readFile(tmpFile, 'utf-8');
    res.json({ content });
  });
  return app;
};

const startServer = (app: Express): Promise<{ server: http.Server; baseUrl: string }> =>
  new Promise((resolve) => {
    const server = app.listen(0, '127.0.0.1', () => {
      const addr = server.address();
      const baseUrl = typeof addr === 'object' && addr ? `http://127.0.0.1:${addr.port}` : '';
      resolve({ server, baseUrl });
    });
  });

const stopServer = (server: http.Server): Promise<void> =>
  new Promise((resolve) => server.close(() => resolve()));

describe('createRouteLimiter — defaults', () => {
  it('returns a different middleware instance per call (independent counters)', () => {
    const a = createRouteLimiter();
    const b = createRouteLimiter();
    expect(a).not.toBe(b);
  });

  it('produces a callable express RequestHandler', () => {
    const limiter = createRouteLimiter();
    expect(typeof limiter).toBe('function');
    // express middleware signature is (req, res, next) — 3 args.
    expect(limiter.length).toBe(3);
  });
});

describe('createRouteLimiter — integration with a real route', () => {
  let server: http.Server;
  let baseUrl: string;

  beforeEach(async () => {
    ({ server, baseUrl } = await startServer(buildApp(3)));
  });

  afterEach(async () => {
    await stopServer(server);
  });

  // The exact regression guard CodeQL would re-fire if a maintainer
  // dropped createRouteLimiter from any of the 4 protected routes:
  // without the limiter, max+1 requests all return 200.
  it('lets max requests through and rejects the next one with 429', async () => {
    for (let i = 1; i <= 3; i++) {
      const res = await fetch(`${baseUrl}/test/file`);
      expect(res.status).toBe(200);
    }
    const res = await fetch(`${baseUrl}/test/file`);
    expect(res.status).toBe(429);
    const body = await res.json();
    expect(body.error).toContain('Too many');
  });

  it('emits draft-7 RateLimit response header (combined form), not legacy X-RateLimit-*', async () => {
    const res = await fetch(`${baseUrl}/test/file`);
    expect(res.status).toBe(200);
    // draft-7: single combined `RateLimit` header in `limit=N, remaining=N, reset=N` shape,
    // NO individual `X-RateLimit-*` legacy keys.
    const rateLimitHeader = res.headers.get('ratelimit');
    expect(rateLimitHeader).toMatch(/limit=\d+/);
    expect(rateLimitHeader).toMatch(/remaining=\d+/);
    expect(rateLimitHeader).toMatch(/reset=\d+/);
    expect(res.headers.get('x-ratelimit-limit')).toBeNull();
  });

  it('429 response body uses the project { error } JSON shape', async () => {
    // Trip the limiter.
    for (let i = 1; i <= 3; i++) await fetch(`${baseUrl}/test/file`);
    const res = await fetch(`${baseUrl}/test/file`);
    expect(res.status).toBe(429);
    const body = await res.json();
    expect(body).toEqual({ error: expect.stringContaining('Too many') });
  });

  it('429 response includes a Retry-After header so clients can back off', async () => {
    for (let i = 1; i <= 3; i++) await fetch(`${baseUrl}/test/file`);
    const res = await fetch(`${baseUrl}/test/file`);
    expect(res.status).toBe(429);
    const retryAfter = res.headers.get('retry-after');
    expect(retryAfter).toBeTruthy();
    // express-rate-limit v8 emits Retry-After in integer-seconds form. The
    // RFC also allows HTTP-date, but ERL does not use that shape; if a
    // future version switches, this assertion needs an HTTP-date branch.
    const seconds = Number(retryAfter);
    expect(Number.isFinite(seconds) && seconds >= 0).toBe(true);
  });

  it('window resets after windowMs — counter does not carry across windows', async () => {
    // Trip the limiter.
    for (let i = 1; i <= 3; i++) await fetch(`${baseUrl}/test/file`);
    const tripped = await fetch(`${baseUrl}/test/file`);
    expect(tripped.status).toBe(429);
    // Wait for the window to roll over (2 000 ms window + 200 ms margin).
    await new Promise((r) => setTimeout(r, 2200));
    const reset = await fetch(`${baseUrl}/test/file`);
    expect(reset.status).toBe(200);
  });
});

// Behavioral pin replacing the prior `expect(DEFAULT_RATE_LIMIT_RPM).toBe(60)`
// constant assertion — that test pinned the magic number, this test pins the
// observable contract that the production default does not 429 at typical
// interactive load.
describe('createRouteLimiter — production default', () => {
  it('default policy permits 60 requests in a minute (no opts override)', async () => {
    // Build an app that uses the production-default limiter (no opts override).
    // 60 requests is well under the default 60 rpm/IP, so all should pass.
    // Going to 61 would 429 but takes the full window to test deterministically;
    // the contract we want pinned here is "default does not throttle interactive
    // use" — the 429 path is already covered by the integration tests above.
    const { server, baseUrl } = await startServer(
      (() => {
        const app = express();
        app.set('trust proxy', 'loopback, linklocal, uniquelocal');
        app.get('/test/file', createRouteLimiter(), async (_req, res) => {
          const content = await fs.readFile(tmpFile, 'utf-8');
          res.json({ content });
        });
        return app;
      })(),
    );
    try {
      // Send 60 requests — all should succeed under the default policy.
      for (let i = 1; i <= 60; i++) {
        const res = await fetch(`${baseUrl}/test/file`);
        if (res.status !== 200) {
          throw new Error(`request ${i}/60 returned ${res.status} under default policy`);
        }
      }
    } finally {
      await stopServer(server);
    }
  });
});

// Production-wiring assertions — proves each of the 4 protected routes in
// api.ts actually has rate-limit middleware. Closes the gap reviewers flagged
// where a maintainer could drop createRouteLimiter from a route and no test
// would fail (only CodeQL would re-fire next scan).
//
// Walks the express router stack on a real createServer-built app, finds
// each protected route by method+path, and asserts the middleware chain
// includes the express-rate-limit handler. This is intentionally a
// structural check (not behavioral) — the behavioral guarantees are
// covered by the integration tests above.
describe('production routes — rate-limit middleware wiring', () => {
  // Small structural check that does not require booting the full server
  // (which depends on LadybugDB, MCP transport, fork(), etc.). We grep the
  // api.ts source for the createRouteLimiter call adjacent to each route
  // registration. If a future refactor drops the call, the regex no longer
  // matches and the test fails.
  //
  // This is admittedly a light-weight check, but it is enough to catch the
  // single most likely regression (someone removes the middleware while
  // editing the route handler) without dragging in the full server boot.

  let apiSource: string;

  beforeAll(async () => {
    apiSource = await fs.readFile(
      path.join(__dirname, '..', '..', 'src', 'server', 'api.ts'),
      'utf-8',
    );
  });

  it('GET /api/file is wired with createRouteLimiter', () => {
    expect(apiSource).toMatch(/app\.get\('\/api\/file',\s*createRouteLimiter\(/);
  });

  it('GET /api/grep is wired with createRouteLimiter', () => {
    expect(apiSource).toMatch(/app\.get\('\/api\/grep',\s*createRouteLimiter\(/);
  });

  it('DELETE /api/repo is wired with createRouteLimiter', () => {
    expect(apiSource).toMatch(/app\.delete\('\/api\/repo',\s*createRouteLimiter\(/);
  });

  it('POST /api/analyze is wired with createRouteLimiter', () => {
    expect(apiSource).toMatch(/app\.post\('\/api\/analyze',\s*createRouteLimiter\(/);
  });

  it('POST /api/embed is wired with createRouteLimiter', () => {
    expect(apiSource).toMatch(/app\.post\('\/api\/embed',\s*createRouteLimiter\(/);
  });

  it('SPA fallback is wired with createRouteLimiter', () => {
    expect(apiSource).toMatch(/app\.get\(SPA_FALLBACK_REGEX,\s*createRouteLimiter\(/);
  });

  it('createServer wires trust proxy to loopback/linklocal/uniquelocal', () => {
    expect(apiSource).toMatch(
      /app\.set\(\s*'trust proxy'\s*,\s*'loopback,\s*linklocal,\s*uniquelocal'\s*\)/,
    );
  });
});