/**
 * App health endpoint test — locks in the [E00-S02-T03] `GET /health`
 * endpoint for the workspace server.
 *
 * Acceptance criteria covered (each test fails without the committed state):
 *   - "app health endpoint succeeds" → the committed
 *     `apps/server/src/index.ts` creates an HTTP server (`node:http`
 *     `createServer`), listens on the application port (default 3000,
 *     `PORT`-overridable) and answers `GET /health` with HTTP 200. The
 *     "HTTP smoke test" boots the committed server source (Node type
 *     stripping, no build step) on an ephemeral port and makes a real
 *     `GET /health` request, asserting a 2xx response.
 *   - "the endpoint reports a healthy application" → the `/health` response
 *     body is JSON reporting a healthy application (`{"status":"ok"}`),
 *     asserted statically against the committed source and by the smoke test.
 *
 * Run: `node --test tests/health-endpoint.test.mjs`
 * (node:test — built into Node >= 18; no dependencies, lockfile untouched.)
 */

import test from 'node:test';
import assert from 'node:assert/strict';
import { readFileSync } from 'node:fs';
import { spawn } from 'node:child_process';
import { once } from 'node:events';
import { createServer as createNetServer } from 'node:net';
import path from 'node:path';
import { fileURLToPath } from 'node:url';

const REPO_ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '..');

const read = (relPath) => readFileSync(path.join(REPO_ROOT, relPath), 'utf8');

/** The committed server entrypoint under test. */
const SERVER_SRC = 'apps/server/src/index.ts';

const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

// ---------------------------------------------------------------------------
// Static assertions on the committed server entrypoint
// ---------------------------------------------------------------------------

/**
 * Asserts the committed server entrypoint answers `GET /health` with HTTP 200
 * and reports a healthy application. Fails fast on a missing/placeholder
 * entrypoint; the mutation probes below prove the assertions are non-vacuous.
 */
function assertHealthEndpointSource(src) {
  assert.match(
    src,
    /createServer\(/,
    'the server entrypoint must create an HTTP server (node:http createServer)',
  );
  assert.match(
    src,
    /'\/health'/,
    "the server entrypoint must route the health endpoint (GET /health)",
  );
  assert.match(
    src,
    /sendJson\(res, 200/,
    'the health route must answer with HTTP 200 (app health endpoint succeeds)',
  );
  assert.match(
    src,
    /status:\s*'ok'/,
    "the health payload must report a healthy application ({\"status\":\"ok\"})",
  );
  assert.match(
    src,
    /server\.listen\(/,
    'the server entrypoint must start listening (server.listen)',
  );
  assert.match(
    src,
    /3000/,
    'the server must default to the application port 3000 (Dockerfile EXPOSE / compose :3000)',
  );
}

// ---------------------------------------------------------------------------
// Boot helpers for the HTTP smoke test (Node type stripping, no build step)
// ---------------------------------------------------------------------------

/**
 * How the current Node executes TypeScript sources: `default` (>= 23.6, type
 * stripping on by default), `strip-types-flag` (>= 22.6 via
 * `--experimental-strip-types`) or `null` (cannot run .ts at all). The
 * workspace pins engines.node to 24.x, where type stripping is stable.
 */
function tsExecMode() {
  const [major, minor] = process.versions.node.split('.').map(Number);
  if (major > 23 || (major === 23 && minor >= 6)) return 'default';
  if (major === 22 && minor >= 6) return 'strip-types-flag';
  return null;
}

/** Reserves an ephemeral TCP port, then releases it for the child to bind. */
function reservePort() {
  return new Promise((resolve, reject) => {
    const probe = createNetServer();
    probe.once('error', reject);
    probe.listen(0, '127.0.0.1', () => {
      const address = probe.address();
      const port = typeof address === 'object' && address !== null ? address.port : 0;
      probe.close(() => resolve(port));
    });
  });
}

/**
 * Boots the committed server source on `port`. Returns `{ child, stderr }`;
 * the child writes its stderr into the `stderr()` closure for diagnostics.
 */
function bootServer(port) {
  const args =
    tsExecMode() === 'strip-types-flag'
      ? ['--experimental-strip-types', SERVER_SRC]
      : [SERVER_SRC];
  const child = spawn(process.execPath, args, {
    cwd: REPO_ROOT,
    env: { ...process.env, PORT: String(port) },
    stdio: ['ignore', 'ignore', 'pipe'],
  });
  let stderr = '';
  child.stderr.on('data', (chunk) => {
    stderr += String(chunk);
  });
  return { child, stderr: () => stderr };
}

/**
 * Polls `GET /health` until it answers or the child exits / the deadline
 * passes (poll with timeout — no flaky sleeps).
 */
async function waitForHealth(port, child, stderr) {
  const deadline = Date.now() + 10_000;
  let lastError = '';
  while (Date.now() < deadline) {
    if (child.exitCode !== null) {
      throw new Error(
        `the server exited before answering GET /health (code ${child.exitCode}): ${stderr().trim()}`,
      );
    }
    try {
      return await fetch(`http://127.0.0.1:${port}/health`, {
        signal: AbortSignal.timeout(1_000),
      });
    } catch (err) {
      lastError = err instanceof Error ? err.message : String(err);
      await delay(100);
    }
  }
  throw new Error(
    `GET /health did not answer within 10s (last error: ${lastError}; server stderr: ${stderr().trim()})`,
  );
}

// ---------------------------------------------------------------------------
// Criterion tests
// ---------------------------------------------------------------------------

test('the app health endpoint succeeds (committed entrypoint answers GET /health with HTTP 200)', () => {
  assertHealthEndpointSource(read(SERVER_SRC));
});

test('the endpoint reports a healthy application (committed health payload is {"status":"ok"})', () => {
  const src = read(SERVER_SRC);
  assert.match(
    src,
    /status:\s*'ok'/,
    "the health payload must report a healthy application ({\"status\":\"ok\"})",
  );
});

test('an HTTP smoke test against the booted server succeeds for GET /health (200 + healthy body)', async (t) => {
  if (!tsExecMode()) {
    t.skip(
      `Node ${process.versions.node} cannot execute TypeScript sources; the workspace pins engines.node to 24.x (type stripping is stable there)`,
    );
    return;
  }
  const port = await reservePort();
  const { child, stderr } = bootServer(port);
  try {
    const response = await waitForHealth(port, child, stderr);
    assert.equal(
      response.status,
      200,
      `GET /health must succeed with HTTP 200 (got ${response.status})`,
    );
    const body = await response.json();
    assert.equal(
      body.status,
      'ok',
      'the health endpoint must report a healthy application ({"status":"ok"})',
    );
  } finally {
    child.kill('SIGTERM');
    await Promise.race([once(child, 'exit'), delay(2_000)]);
    if (child.exitCode === null && child.signalCode === null) child.kill('SIGKILL');
  }
});

// ---------------------------------------------------------------------------
// Non-vacuous probes — the assertions above really do fail on violations
// ---------------------------------------------------------------------------

test('removing the /health route makes the health-endpoint criterion fail (mutation probe)', () => {
  const src = read(SERVER_SRC);
  const withoutRoute = src.replace(/'\/health'/, "'/nope'");
  assert.notEqual(withoutRoute, src, 'the mutation must actually replace the /health route');
  assert.throws(() => assertHealthEndpointSource(withoutRoute), /\/health/);
});

test('removing the HTTP 200 makes the health-endpoint criterion fail (mutation probe)', () => {
  const src = read(SERVER_SRC);
  const without200 = src.replace(/sendJson\(res, 200/, 'sendJson(res, 500');
  assert.notEqual(without200, src, 'the mutation must actually change the health status code');
  assert.throws(() => assertHealthEndpointSource(without200), /HTTP 200/);
});

test('removing the healthy report makes the healthy-report criterion fail (mutation probe)', () => {
  const src = read(SERVER_SRC);
  const withoutOk = src.replace(/status:\s*'ok'/, "status: 'nope'");
  assert.notEqual(withoutOk, src, 'the mutation must actually change the health payload');
  assert.throws(() => assertHealthEndpointSource(withoutOk), /healthy application/);
});

test('a placeholder entrypoint (no server at all) fails the health-endpoint criterion (mutation probe)', () => {
  assert.throws(() => assertHealthEndpointSource('export {};\n'), /createServer/);
});