pdfer/pages/api/document/[id].ts

import { promises } from 'fs'
import { NextApiRequest, NextApiResponse } from 'next'

import { getPdfPath } from '../../../lib/utils'

const handler = async (req: NextApiRequest, res: NextApiResponse) => {
  const { method } = req

  switch (req.method) {
    case 'GET':
      try {
        const {
          query: { id: idArg },
        } = req

        const id = Array.isArray(idArg) ? idArg[0] : idArg

        const fileContent = await promises.readFile(getPdfPath(id))
        res.setHeader('Content-Type', 'application/pdf')
        res.status(200).send(fileContent)
      } catch (error) {
        console.error(error)
        res.status(404).json({ statusCode: 404, message: 'Method Not Allowed' })
      }
      break
    default:
      res.setHeader('Allow', ['GET'])
      res.status(405).end(`Method ${method} Not Allowed`)
  }
}

export default handler