import fetch from 'node:fetch';

const DROPBOX_APP_KEY = process.env.DROPBOX_APP_KEY;
const DROPBOX_APP_SECRET = process.env.DROPBOX_APP_SECRET;
const DROPBOX_REFRESH_TOKEN = process.env.DROPBOX_REFRESH_TOKEN;

async function getAccessToken() {
  const response = await fetch('https://api.dropboxapi.com/oauth2/token', {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body: `grant_type=refresh_token&refresh_token=${DROPBOX_REFRESH_TOKEN}&client_id=${DROPBOX_APP_KEY}&client_secret=${DROPBOX_APP_SECRET}`
  });
  const data = await response.json();
  return data.access_token;
}

export default async function handler(req, res) {
  const accessToken = await getAccessToken();
  
  if (req.method === 'GET' && req.query.info === '1') {
    try {
      const fileInfo = await fetch('https://api.dropboxapi.com/2/files/get_metadata', {
        method: 'POST',
        headers: {
          'Authorization': `Bearer ${accessToken}`,
          'Content-Type': 'application/json'
        },
        body: JSON.stringify({ path: '/Data-Matrix.xlsx' })
      });
      const data = await fileInfo.json();
      return res.json({
        rev: data.rev,
        size: data.size,
        server_modified: data.server_modified
      });
    } catch (err) {
      return res.status(500).json({ error: err.message });
    }
  }

  try {
    const upstream = await fetch('https://content.dropboxapi.com/2/files/download', {
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${accessToken}`,
        'Dropbox-API-Arg': JSON.stringify({ path: '/Data-Matrix.xlsx' })
      }
    });
    
    const buffer = await upstream.arrayBuffer();
    
    res.setHeader('Content-Type', 'application/octet-stream');
    res.setHeader('Cache-Control', 'no-store');
    res.send(Buffer.from(buffer));
  } catch (err) {
    console.error('Dropbox error:', err);
    res.status(500).send('Proxy error: ' + err.message);
  }
}