class User

class User extends DrupalSqlBase {
  
  /**
   * {@inheritdoc}
   */
  public function query() {
    return $this->select('users', 'u')
      ->fields('u', array_keys($this->baseFields()))
      ->condition('u.uid', 0, '>');
  }
  
  /**
   * {@inheritdoc}
   */
  public function fields() {
    $fields = $this->baseFields();
    // Add roles field.
    $fields['roles'] = $this->t('Roles');
    return $fields;
  }
  
  /**
   * {@inheritdoc}
   */
  public function prepareRow(Row $row) {
    // User roles.
    $roles = $this->select('users_roles', 'ur')
      ->fields('ur', [
      'rid',
    ])
      ->condition('ur.uid', $row->getSourceProperty('uid'))
      ->execute()
      ->fetchCol();
    $row->setSourceProperty('roles', $roles);
    // We are adding here the Event contributed module column.
    // @see https://api.drupal.org/api/drupal/modules%21user%21user.install/function/user_update_7002/7
    if ($row->hasSourceProperty('timezone_id') && $row->getSourceProperty('timezone_id')) {
      if ($this->getDatabase()
        ->schema()
        ->tableExists('event_timezones')) {
        $event_timezone = $this->select('event_timezones', 'e')
          ->fields('e', [
          'name',
        ])
          ->condition('e.timezone', $row->getSourceProperty('timezone_id'))
          ->execute()
          ->fetchField();
        if ($event_timezone) {
          $row->setSourceProperty('event_timezone', $event_timezone);
        }
      }
    }
    // Unserialize Data.
    $data = $row->getSourceProperty('data');
    if ($data !== NULL) {
      $row->setSourceProperty('data', unserialize($row->getSourceProperty('data')));
    }
    return parent::prepareRow($row);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getIds() {
    return [
      'uid' => [
        'type' => 'integer',
        'alias' => 'u',
      ],
    ];
  }
  
  /**
   * Returns the user base fields to be migrated.
   *
   * @return array
   *   Associative array having field name as key and description as value.
   */
  protected function baseFields() {
    $fields = [
      'uid' => $this->t('User ID'),
      'name' => $this->t('Username'),
      'pass' => $this->t('Password'),
      'mail' => $this->t('Email address'),
      'theme' => $this->t('Theme'),
      'signature' => $this->t('Signature'),
      'signature_format' => $this->t('Signature format'),
      'created' => $this->t('Registered timestamp'),
      'access' => $this->t('Last access timestamp'),
      'login' => $this->t('Last login timestamp'),
      'status' => $this->t('Status'),
      'timezone' => $this->t('Timezone'),
      'language' => $this->t('Language'),
      'picture' => $this->t('Picture'),
      'init' => $this->t('Init'),
      'data' => $this->t('User data'),
    ];
    // Possible field added by Date contributed module.
    // @see https://api.drupal.org/api/drupal/modules%21user%21user.install/function/user_update_7002/7
    if ($this->getDatabase()
      ->schema()
      ->fieldExists('users', 'timezone_name')) {
      $fields['timezone_name'] = $this->t('Timezone (Date)');
    }
    // Possible field added by Event contributed module.
    // @see https://api.drupal.org/api/drupal/modules%21user%21user.install/function/user_update_7002/7
    if ($this->getDatabase()
      ->schema()
      ->fieldExists('users', 'timezone_id')) {
      $fields['timezone_id'] = $this->t('Timezone (Event)');
    }
    return $fields;
  }

}