// This function verifies the token to prevent generating images with random
// parameters (`id`).
// Check pages/encrypted/[id].tsx for more info.

import { ImageResponse } from '@vercel/og'
import { NextRequest } from 'next/server'

export const config = {
  runtime: 'experimental-edge',
}

const key = crypto.subtle.importKey(
  'raw',
  new TextEncoder().encode('my_secret'),
  { name: 'HMAC', hash: { name: 'SHA-256' } },
  false,
  ['sign']
)

function toHex(arrayBuffer) {
  return Array.prototype.map
    .call(new Uint8Array(arrayBuffer), (n) => n.toString(16).padStart(2, '0'))
    .join('')
}

export default async function handler(req: NextRequest) {
  const { searchParams } = req.nextUrl

  const id = searchParams.get('id')
  const token = searchParams.get('token')

  const verifyToken = toHex(
    await crypto.subtle.sign(
      'HMAC',
      await key,
      new TextEncoder().encode(JSON.stringify({ id }))
    )
  )

  if (token !== verifyToken) {
    return new Response('Invalid token.', { status: 401 })
  }

  return new ImageResponse(
    (
      <div
        style={{
          display: 'flex',
          fontSize: 40,
          color: 'black',
          background: 'white',
          width: '100%',
          height: '100%',
          padding: '50px 200px',
          textAlign: 'center',
          justifyContent: 'center',
          alignContent: 'center',
        }}
      >
        <h1>Card generated, id={id}.</h1>
      </div>
    ),
    {
      width: 1200,
      height: 630,
    }
  )
}