class UserData

class UserData implements UserDataInterface {
  
  /**
   * The database connection to use.
   *
   * @var \Drupal\Core\Database\Connection
   */
  protected $connection;
  
  /**
   * Constructs a new user data service.
   *
   * @param \Drupal\Core\Database\Connection $connection
   *   The database connection to use.
   */
  public function __construct(Connection $connection) {
    $this->connection = $connection;
  }
  
  /**
   * {@inheritdoc}
   */
  public function get($module, $uid = NULL, $name = NULL) {
    $query = $this->connection
      ->select('users_data', 'ud')
      ->fields('ud')
      ->condition('module', $module);
    if (isset($uid)) {
      $query->condition('uid', $uid);
    }
    if (isset($name)) {
      $query->condition('name', $name);
    }
    $result = $query->execute();
    // If $module, $uid, and $name were passed, return the value.
    if (isset($name) && isset($uid)) {
      $result = $result->fetchAllAssoc('uid');
      if (isset($result[$uid])) {
        return $result[$uid]->serialized ? unserialize($result[$uid]->value) : $result[$uid]->value;
      }
      return NULL;
    }
    $return = [];
    // If $module and $uid were passed, return data keyed by name.
    if (isset($uid)) {
      foreach ($result as $record) {
        $return[$record->name] = $record->serialized ? unserialize($record->value) : $record->value;
      }
      return $return;
    }
    // If $module and $name were passed, return data keyed by uid.
    if (isset($name)) {
      foreach ($result as $record) {
        $return[$record->uid] = $record->serialized ? unserialize($record->value) : $record->value;
      }
      return $return;
    }
    // If only $module was passed, return data keyed by uid and name.
    foreach ($result as $record) {
      $return[$record->uid][$record->name] = $record->serialized ? unserialize($record->value) : $record->value;
    }
    return $return;
  }
  
  /**
   * {@inheritdoc}
   */
  public function set($module, $uid, $name, $value) {
    $serialized = (int) !is_scalar($value);
    if ($serialized) {
      $value = serialize($value);
    }
    $this->connection
      ->merge('users_data')
      ->keys([
      'uid' => $uid,
      'module' => $module,
      'name' => $name,
    ])
      ->fields([
      'value' => $value,
      'serialized' => $serialized,
    ])
      ->execute();
  }
  
  /**
   * {@inheritdoc}
   */
  public function delete($module = NULL, $uid = NULL, $name = NULL) {
    $query = $this->connection
      ->delete('users_data');
    // Cast scalars to array so we can consistently use an IN condition.
    if (isset($module)) {
      $query->condition('module', (array) $module, 'IN');
    }
    if (isset($uid)) {
      $query->condition('uid', (array) $uid, 'IN');
    }
    if (isset($name)) {
      $query->condition('name', (array) $name, 'IN');
    }
    $query->execute();
  }

}