export function configuration(env) {
  const raw = env.PORT ?? '3000';
  if (!/^[0-9]+$/.test(raw)) throw new Error('Invalid port');
  const port = Number(raw);
  if (!Number.isInteger(port) || port < 1024 || port > 65535)
    throw new Error('Invalid port');
  const mode = env.NODE_ENV ?? 'development';
  if (!['development', 'test', 'production'].includes(mode))
    throw new Error('Invalid mode');
  return { port, mode };
}
console.log(JSON.stringify(configuration({ PORT: '3100', NODE_ENV: 'test' })));
try {
  configuration({ PORT: '3100oops' });
} catch (error) {
  console.log(error.message);
}