first node server

gistfile1.js

var async = require('async');

var express = require('express'),
    app = express();

var google = require('googleapis'),
    OAuth2Client = google.auth.OAuth2;

var oauth2Client = new OAuth2Client(CLIENT_ID, CLIENT_SECRET, REDIRECT_URL);

// Authorization uri definition
var authorization_uri = oauth2Client.generateAuthUrl({
  access_type: 'offline', // will return a refresh token
  scope: SCOPE
});

var drive = google.drive('v2');

app.get('/auth', function (req, res) {
  res.redirect(authorization_uri);
});

function listImageMetadata(res) {
  var metadata = [];
  drive.files.list({
    q: "mimeType contains 'image/' or mimeType contains 'video/'",
    auth: oauth2Client
  }, function(err, response) {
    console.log(err);
    async.each(response.items, function(item, callback) {
      drive.files.get({
        fileId: item.id,
        auth: oauth2Client
      }, function(err, response) {
        console.log(response.imageMediaMetadata);
        metadata[metadata.length] = response.imageMediaMetadata;
        console.log(metadata.length);
        callback();
      });
    }, function(err) {
      if (err) {
        console.log(err);
      } else {
        console.log(metadata);
        res.json(metadata);
      }
    });
  });
}

// Callback service parsing the authorization token and asking for the access token
app.get('/oauth2callback', function (req, res) {
  var code = req.query.code;
  console.log(code);
  // request access token
  oauth2Client.getToken(code, function(err, tokens) {
    // set tokens to the client
    oauth2Client.setCredentials(tokens);
    listImageMetadata(res);
  });
});

app.get('/', function (req, res) {
  // TODO: check and load oauth2Client from somewhere. If invalid then /auth.
  res.redirect(authorization_uri);
});

app.listen(8081);

console.log('Express server started on port 8081');