// Bounded rate state and explicit client identity.
//
// Two separate defects are covered here:
//   1. The limiter's map must be hard-bounded. Only evicting *expired* entries
//      means 20k+ unexpired keys grow state without limit.
//   2. Behind a reverse proxy, req.socket.remoteAddress is the proxy's loopback
//      address, so every user shares one quota. The policy must be explicit:
//      either trust a configured loopback proxy's forwarded client address, or
//      state truthfully that the limit is global — never silently trust a
//      spoofable header from an untrusted peer.
import test from 'node:test';
import assert from 'node:assert/strict';

import { createRateLimiter } from '../src/rate-limiter.js';
import { resolveClientIdentity } from '../src/client-identity.js';

test('rate state is hard-bounded under a flood of unexpired distinct keys', () => {
  const limiter = createRateLimiter({ windowMs: 60_000, maxRequests: 10, maxKeys: 1024 });
  const now = Date.now();
  for (let i = 0; i < 20_000; i += 1) {
    limiter.take(`key-${i}`, now); // all within the same, unexpired window
  }
  const size = limiter.size();
  assert.ok(size <= 1024,
    `limiter retained ${size} unexpired keys; state must be hard-bounded, not merely expiry-swept`);
});

test('a flood of distinct keys never lets a repeat offender escape its own limit', () => {
  const limiter = createRateLimiter({ windowMs: 60_000, maxRequests: 3, maxKeys: 64 });
  const now = Date.now();
  // The offender opens its window first.
  for (let i = 0; i < 3; i += 1) assert.equal(limiter.take('offender', now).allowed, true);
  assert.equal(limiter.take('offender', now).allowed, false, 'offender must be blocked');
  // Now flood far past the cap to try to evict the offender's counter.
  for (let i = 0; i < 5_000; i += 1) limiter.take(`flood-${i}`, now);
  const afterFlood = limiter.take('offender', now);
  assert.equal(afterFlood.allowed, false,
    'eviction must not reset an active offender: that would make the limit bypassable by flooding');
});

test('eviction prefers expired entries before evicting live ones', () => {
  const limiter = createRateLimiter({ windowMs: 1_000, maxRequests: 5, maxKeys: 8 });
  const t0 = 1_000_000;
  for (let i = 0; i < 8; i += 1) limiter.take(`old-${i}`, t0);
  // Well after those windows expired, new keys must reuse the reclaimed space.
  for (let i = 0; i < 8; i += 1) limiter.take(`new-${i}`, t0 + 5_000);
  assert.ok(limiter.size() <= 8);
  assert.equal(limiter.take('new-0', t0 + 5_000).allowed, true);
});

test('the fixed-window boundary cannot be used to double the burst', () => {
  const limiter = createRateLimiter({ windowMs: 60_000, maxRequests: 10 });
  const t0 = 1_000_000;
  let allowed = 0;
  // Open the window, then spend the whole budget at the very end of it.
  if (limiter.take('same', t0).allowed) allowed += 1;
  for (let i = 0; i < 9; i += 1) if (limiter.take('same', t0 + 59_999).allowed) allowed += 1;
  assert.equal(allowed, 10, 'the nominal budget must be usable');
  // Immediately across the boundary a naive fixed window grants a fresh budget,
  // allowing 2x the nominal rate within milliseconds of real time.
  let acrossBoundary = 0;
  for (let i = 0; i < 10; i += 1) if (limiter.take('same', t0 + 60_000).allowed) acrossBoundary += 1;
  assert.ok(acrossBoundary < 10,
    `boundary straddle allowed a full extra budget (${acrossBoundary}), doubling the effective rate`);
  const total = allowed + acrossBoundary;
  assert.ok(total <= 14,
    `${total} requests accepted across a ~1ms boundary straddle against a 10-per-60s budget`);
});

test('sustained load stays near the nominal rate rather than bursting to 2x each boundary', () => {
  const limiter = createRateLimiter({ windowMs: 1_000, maxRequests: 5 });
  let accepted = 0;
  // Ten seconds of continuous pressure at 50 requests/second.
  for (let ms = 0; ms < 10_000; ms += 20) {
    if (limiter.take('steady', 500_000 + ms).allowed) accepted += 1;
  }
  // 10s at 5/s is 50; allow a small margin but not a 2x boundary doubling.
  assert.ok(accepted <= 60, `sustained acceptance ${accepted} exceeded the nominal 5/s budget envelope`);
  assert.ok(accepted >= 40, `sustained acceptance ${accepted} is unusably far below the nominal budget`);
});

test('client identity behind an untrusted peer never trusts forwarded headers', () => {
  const identity = resolveClientIdentity({
    remoteAddress: '203.0.113.7',
    headers: { 'x-forwarded-for': '198.51.100.9', 'x-real-ip': '198.51.100.10' },
    trustedProxies: [],
  });
  assert.equal(identity.key, '203.0.113.7', 'the peer address is the only trustworthy identity here');
  assert.equal(identity.scope, 'peer');
  assert.equal(identity.trustedProxy, false);
});

test('a configured trusted loopback proxy contributes the forwarded client address', () => {
  const identity = resolveClientIdentity({
    remoteAddress: '127.0.0.1',
    headers: { 'x-forwarded-for': '198.51.100.9, 10.0.0.5' },
    trustedProxies: ['127.0.0.1'],
  });
  assert.equal(identity.key, '198.51.100.9', 'the left-most forwarded address is the client');
  assert.equal(identity.scope, 'forwarded');
  assert.equal(identity.trustedProxy, true);
});

test('a trusted proxy that forwards nothing usable degrades to a truthful global policy', () => {
  const identity = resolveClientIdentity({
    remoteAddress: '127.0.0.1',
    headers: {},
    trustedProxies: ['127.0.0.1'],
  });
  assert.equal(identity.scope, 'global',
    'without a usable forwarded address the quota is shared; the policy must say so');
  assert.equal(identity.key, 'global');
});

test('forwarded addresses are validated, not echoed', () => {
  for (const spoof of ['not-an-ip', '', '   ', '999.999.999.999', '<script>', '127.0.0.1; rm -rf /']) {
    const identity = resolveClientIdentity({
      remoteAddress: '127.0.0.1',
      headers: { 'x-forwarded-for': spoof },
      trustedProxies: ['127.0.0.1'],
    });
    assert.equal(identity.scope, 'global', `must not accept ${JSON.stringify(spoof)} as an identity`);
    assert.equal(identity.key, 'global');
  }
});

test('identity keys never contain payload data and stay short', () => {
  const identity = resolveClientIdentity({
    remoteAddress: '2001:db8::1',
    headers: {},
    trustedProxies: [],
  });
  assert.ok(identity.key.length <= 64);
  assert.doesNotMatch(identity.key, /[A-Za-z0-9+/]{40,}/);
});