namae/api/services/existence.ts

import {send, sendError, fetch, NowRequest, NowResponse} from '../util/http';

export default async function handler(req: NowRequest, res: NowResponse) {
  const {query} = req.query;

  if (!query) {
    return sendError(res, new Error('no query given'));
  }

  if (
    !/^[(http(s)?):\/\/(www\.)?a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%_\+.~#?&//=]*)$/.test(
      query,
    )
  ) {
    return sendError(res, new Error('invalid characters'));
  }

  try {
    const response = await fetch(`https://${query}`);
    const availability = response.status === 404;
    send(res, {availability});
  } catch (err) {
    sendError(res, err);
  }
}