namae/api/services/dns/[query].ts

import dns from 'dns';
import { send, sendError } from '../../../util/http';
import { VercelRequest, VercelResponse } from '@vercel/node';

function resolvePromise(hostname: string): Promise<string[]> {
  return new Promise((resolve, reject) => {
    dns.resolve4(hostname, function (err, addresses) {
      if (err) return reject(err);
      resolve(addresses);
    });
  });
}

export default async function handler(
  req: VercelRequest,
  res: VercelResponse
): Promise<void> {
  const { query } = req.query;

  if (!query || typeof query !== 'string') {
    return sendError(res, new Error('No query given'));
  }

  try {
    const response = await resolvePromise(query);
    const availability = response && response.length > 0 ? false : true;
    send(res, { availability });
  } catch (err: any) {
    if (err.code === 'ENODATA' || err.code === 'ENOTFOUND') {
      return send(res, { availability: true });
    }
    sendError(res, err);
  }
}