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

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

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'));
  }

  if (/[^a-zA-Z0-9_-]/.test(query)) {
    return sendError(res, new Error('Invalid characters'));
  }

  try {
    const response = await fetch(
      `https://${encodeURIComponent(query)}.slack.com`
    );
    const availability = response.status !== 200;
    send(res, { availability });
  } catch (err: any) {
    sendError(res, err);
  }
}