// Static host for Learning Lab Express. Proxies /api to the learning-lab engine
// so the browser stays same-origin (no CORS setup needed on the engine).
import http from 'node:http';
import { readFile } from 'node:fs/promises';
import { extname, join, normalize } from 'node:path';
import { fileURLToPath } from 'node:url';

const ROOT = fileURLToPath(new URL('.', import.meta.url));
const PORT = Number(process.env.PORT || 3000);
const ENGINE = new URL(process.env.ENGINE_URL || 'http://localhost:8000');
const TYPES = { '.html': 'text/html; charset=utf-8', '.js': 'text/javascript; charset=utf-8', '.css': 'text/css', '.svg': 'image/svg+xml' };

function proxy(req, res) {
  const upstream = http.request({
    host: ENGINE.hostname, port: ENGINE.port, path: req.url, method: req.method,
    headers: { ...req.headers, host: ENGINE.host },
  }, up => { res.writeHead(up.statusCode, up.headers); up.pipe(res); });
  upstream.on('error', () => {
    res.writeHead(502, { 'content-type': 'application/json' });
    res.end(JSON.stringify({ detail: `Engine learning-lab tidak dapat dihubungi di ${ENGINE.origin}` }));
  });
  req.pipe(upstream);
}

// Clerk publishable keys are public; default to the engine's own dev key so both share one Clerk instance.
async function clerkKey() {
  if (process.env.CLERK_PUBLISHABLE_KEY) return process.env.CLERK_PUBLISHABLE_KEY;
  try {
    const env = await readFile(join(ROOT, '../../learning-lab/backend/.env'), 'utf8');
    return env.match(/^VITE_CLERK_PUBLISHABLE_KEY=["']?([^"'\s]+)/m)?.[1] || '';
  } catch { return ''; }
}

async function serve(req, res) {
  const path = new URL(req.url, 'http://x').pathname;
  if (path === '/config.js') {
    res.writeHead(200, { 'content-type': TYPES['.js'] });
    return res.end(`window.LLE_CONFIG=${JSON.stringify({ clerkKey: await clerkKey() })};`);
  }
  const name = path === '/' ? 'index.html' : normalize(path).replace(/^([/\\])+/, '');
  if (name.startsWith('..')) { res.writeHead(403); return res.end(); }
  try {
    const body = await readFile(join(ROOT, name));
    res.writeHead(200, { 'content-type': TYPES[extname(name)] || 'application/octet-stream' });
    res.end(body);
  } catch {
    res.writeHead(404); res.end('Not found');
  }
}

http.createServer((req, res) => (req.url.startsWith('/api/') ? proxy(req, res) : serve(req, res)))
  .listen(PORT, () => console.log(`Learning Lab Express: http://localhost:${PORT}  →  engine ${ENGINE.origin}`));