auth.js

const fsPromises = require('fs').promises;
const path = require('path');
const { google } = require('googleapis');
const { authenticate } = require('@google-cloud/local-auth');

const SCOPES = [
  'https://www.googleapis.com/auth/drive.readonly',
  'https://www.googleapis.com/auth/drive.metadata.readonly',
];
const TOKEN_PATH = path.join(process.cwd(), 'token.json');
const CREDENTIALS_PATH = path.join(process.cwd(), 'credentials.json');

async function loadSavedCredentials() {
  try {
    const content = await fsPromises.readFile(TOKEN_PATH);
    const credentials = JSON.parse(content);
    return google.auth.fromJSON(credentials);
  } catch (err) {
    if (err.code !== 'ENOENT') {
      console.error('Error loading saved credentials:', err);
    }
    return null;
  }
}

async function saveCredentials(client) {
  try {
    const content = await fsPromises.readFile(CREDENTIALS_PATH);
    const keys = JSON.parse(content);
    const key = keys.installed || keys.web;
    const payload = JSON.stringify({
      type: 'authorized_user',
      client_id: key.client_id,
      client_secret: key.client_secret,
      refresh_token: client.credentials.refresh_token,
    });
    await fsPromises.writeFile(TOKEN_PATH, payload);
  } catch (err) {
    console.error('Error saving credentials:', err);
  }
}

async function authorize() {
  let client = await loadSavedCredentials();
  if (client) {
    return client;
  }

  client = await authenticate({ scopes: SCOPES, keyfilePath: CREDENTIALS_PATH });

  if (client.credentials) {
    await saveCredentials(client);
  }

  return client;
}

module.exports = { authorize };