import { createReadStream, existsSync, statSync } from 'node:fs';
import { createServer } from 'node:http';
import { extname, join, resolve, sep } from 'node:path';
import { fileURLToPath } from 'node:url';

const root = resolve(fileURLToPath(new URL('./dist', import.meta.url)));
const port = Number(process.env.PORT) || 3000;
const host = process.env.HOST || '0.0.0.0';

const MIME = {
  '.css': 'text/css; charset=utf-8',
  '.html': 'text/html; charset=utf-8',
  '.ico': 'image/x-icon',
  '.js': 'text/javascript; charset=utf-8',
  '.json': 'application/json; charset=utf-8',
  '.map': 'application/json; charset=utf-8',
  '.png': 'image/png',
  '.svg': 'image/svg+xml',
  '.txt': 'text/plain; charset=utf-8',
  '.webp': 'image/webp',
  '.woff': 'font/woff',
  '.woff2': 'font/woff2',
};

function fileUnderRoot(urlPath) {
  const decoded = decodeURIComponent((urlPath ?? '/').split('?')[0] || '/');
  const relative = decoded.replace(/^\/+/, '').replaceAll('/', sep);
  const resolved = resolve(root, relative);
  const prefix = root.endsWith(sep) ? root : root + sep;
  if (resolved !== root && !resolved.startsWith(prefix)) return null;
  return resolved;
}

function send(res, status, body, type = 'text/plain; charset=utf-8') {
  res.writeHead(status, { 'Content-Type': type, 'Cache-Control': 'no-cache' });
  res.end(body);
}

const server = createServer((req, res) => {
  if (req.method === 'GET' && (req.url === '/healthz' || req.url?.startsWith('/healthz?'))) {
    send(res, 200, 'ok');
    return;
  }

  if (req.method !== 'GET' && req.method !== 'HEAD') {
    send(res, 405, 'Method not allowed');
    return;
  }

  const candidate = fileUnderRoot(req.url ?? '/');
  if (!candidate) {
    send(res, 400, 'Bad request');
    return;
  }

  let file = candidate;
  if (!existsSync(file) || statSync(file).isDirectory()) {
    file = join(root, 'index.html');
  }
  if (!existsSync(file)) {
    send(res, 500, 'dist/ missing — run npm run build before start');
    return;
  }

  const type = MIME[extname(file).toLowerCase()] ?? 'application/octet-stream';
  res.writeHead(200, { 'Content-Type': type });
  if (req.method === 'HEAD') {
    res.end();
    return;
  }
  createReadStream(file).pipe(res);
});

if (!existsSync(join(root, 'index.html'))) {
  console.error('dist/index.html missing — run npm run build before start');
  process.exit(1);
}

server.listen(port, host, () => {
  console.log(`LexAI website listening on http://${host}:${port}`);
});