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

import dns from 'dns'
import { send, sendError } from '../../../util/http'
import { NowRequest, NowResponse } 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: NowRequest,
  res: NowResponse
): 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) {
    if (err.code === 'ENODATA' || err.code === 'ENOTFOUND') {
      return send(res, { availability: true })
    }
    sendError(res, err)
  }
}