<?php
  require_once __DIR__ . '/vendor/autoload.php';
  session_start();
  date_default_timezone_set('America/Los_Angeles');

  $REDIRECT_URI = 'http://localhost:8080';
  $KEY_LOCATION = __DIR__ . '/client_secret.json';
  $TOKEN_FILE   = "token.txt";

  $SCOPES = array(
      Google_Service_Gmail::MAIL_GOOGLE_COM,
      'email',
      'profile'
  );

  $client = new Google_Client();
  $client->setApplicationName("ctrlq.org Application");
  $client->setAuthConfig($KEY_LOCATION);

  // Incremental authorization
  $client->setIncludeGrantedScopes(true);

  // Allow access to Google API when the user is not present.
  $client->setAccessType('offline');
  $client->setRedirectUri($REDIRECT_URI);
  $client->setScopes($SCOPES);

  if (isset($_GET['code']) && !empty($_GET['code'])) {
      try {
          // Exchange the one-time authorization code for an access token
          $accessToken = $client->fetchAccessTokenWithAuthCode($_GET['code']);

          // Save the access token and refresh token in local filesystem
          file_put_contents($TOKEN_FILE, json_encode($accessToken));

          $_SESSION['accessToken'] = $accessToken;
          header('Location: ' . filter_var($REDIRECT_URI, FILTER_SANITIZE_URL));
          exit();
      }
      catch (\Google_Service_Exception $e) {
          print_r($e);
      }
  }

  if (!isset($_SESSION['accessToken'])) {

      $token = @file_get_contents($TOKEN_FILE);

      if ($token == null) {

          // Generate a URL to request access from Google's OAuth 2.0 server:
          $authUrl = $client->createAuthUrl();

          // Redirect the user to Google's OAuth server
          header('Location: ' . filter_var($authUrl, FILTER_SANITIZE_URL));
          exit();

      } else {

          $_SESSION['accessToken'] = json_decode($token, true);

      }
  }

  $client->setAccessToken($_SESSION['accessToken']);

  /* Refresh token when expired */
  if ($client->isAccessTokenExpired()) {
      // the new access token comes with a refresh token as well
      $client->fetchAccessTokenWithRefreshToken($client->getRefreshToken());
      file_put_contents($TOKEN_FILE, json_encode($client->getAccessToken()));
  }

  $gmail = new Google_Service_Gmail($client);

  $opt_param               = array();
  $opt_param['maxResults'] = 10;

  $threads = $gmail->users_threads->listUsersThreads("amit@labnol.org", $opt_param);

  foreach ($threads as $thread) {
      print $thread->getId() . " - " . $thread->getSnippet() . '<br/>';
  }

?>