class NodeCounter

class NodeCounter extends DestinationBase implements ContainerFactoryPluginInterface {
  
  /**
   * The database connection.
   *
   * @var \Drupal\Core\Database\Connection
   */
  protected $connection;
  
  /**
   * Constructs a node counter plugin.
   *
   * @param array $configuration
   *   Plugin configuration.
   * @param string $plugin_id
   *   The plugin ID.
   * @param mixed $plugin_definition
   *   The plugin definition.
   * @param \Drupal\migrate\Plugin\MigrationInterface $migration
   *   The current migration.
   * @param \Drupal\Core\Database\Connection $connection
   *   The database connection.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, Connection $connection) {
    parent::__construct($configuration, $plugin_id, $plugin_definition, $migration);
    $this->connection = $connection;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
    return new static($configuration, $plugin_id, $plugin_definition, $migration, $container->get('database'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function getIds() {
    return [
      'nid' => [
        'type' => 'integer',
      ],
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function fields() {
    return [
      'nid' => $this->t('The ID of the node to which these statistics apply.'),
      'totalcount' => $this->t('The total number of times the node has been viewed.'),
      'daycount' => $this->t('The total number of times the node has been viewed today.'),
      'timestamp' => $this->t('The most recent time the node has been viewed.'),
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function import(Row $row, array $old_destination_id_values = []) {
    $nid = $row->getDestinationProperty('nid');
    $daycount = $row->getDestinationProperty('daycount');
    $totalcount = $row->getDestinationProperty('totalcount');
    $timestamp = $row->getDestinationProperty('timestamp');
    $this->connection
      ->merge('node_counter')
      ->key('nid', $nid)
      ->fields([
      'daycount' => $daycount,
      'totalcount' => $totalcount,
      'timestamp' => $timestamp,
    ])
      ->expression('daycount', '[daycount] + :daycount', [
      ':daycount' => $daycount,
    ])
      ->expression('totalcount', '[totalcount] + :totalcount', [
      ':totalcount' => $totalcount,
    ])
      ->expression('timestamp', 'CASE WHEN [timestamp] > :timestamp1 THEN [timestamp] ELSE :timestamp2 END', [
      ':timestamp1' => $timestamp,
      ':timestamp2' => $timestamp,
    ])
      ->execute();
    return [
      $row->getDestinationProperty('nid'),
    ];
  }

}