class VariableTranslation

class VariableTranslation extends DrupalSqlBase {

  /**
   * The variable names to fetch.
   *
   * @var array
   */
  protected $variables;

  /**
   * {@inheritdoc}
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, StateInterface $state, EntityTypeManagerInterface $entity_type_manager) {
    parent::__construct($configuration, $plugin_id, $plugin_definition, $migration, $state, $entity_type_manager);
    $this->variables = $this->configuration['variables'];
  }

  /**
   * {@inheritdoc}
   */
  protected function initializeIterator() {
    return new \ArrayIterator($this
      ->values());
  }

  /**
   * Return the values of the variables specified in the plugin configuration.
   *
   * @return array
   *   An associative array where the keys are the variables specified in the
   *   plugin configuration and the values are the values found in the source.
   *   A key/value pair is added for the language code. Only those values are
   *   returned that are actually in the database.
   */
  protected function values() {
    $values = [];
    $result = $this
      ->prepareQuery()
      ->execute()
      ->FetchAllAssoc('language');
    foreach ($result as $i18n_variable) {
      $values[]['language'] = $i18n_variable->language;
    }
    $result = $this
      ->prepareQuery()
      ->execute()
      ->FetchAll();
    foreach ($result as $i18n_variable) {
      foreach ($values as $key => $value) {
        if ($values[$key]['language'] === $i18n_variable->language) {
          $values[$key][$i18n_variable->name] = unserialize($i18n_variable->value);
          break;
        }
      }
    }
    return $values;
  }

  /**
   * {@inheritdoc}
   */
  protected function doCount() {
    return $this
      ->initializeIterator()
      ->count();
  }

  /**
   * {@inheritdoc}
   */
  public function fields() {
    return array_combine($this->variables, $this->variables);
  }

  /**
   * {@inheritdoc}
   */
  public function query() {
    return $this
      ->getDatabase()
      ->select('i18n_variable', 'v')
      ->fields('v')
      ->condition('name', (array) $this->configuration['variables'], 'IN');
  }

  /**
   * {@inheritdoc}
   */
  public function getIds() {
    $ids['language']['type'] = 'string';
    return $ids;
  }

  /**
   * {@inheritdoc}
   */
  public function checkRequirements() {
    if (!$this
      ->getDatabase()
      ->schema()
      ->tableExists('i18n_variable')) {
      throw new RequirementsException("Source database table 'i18n_variable' does not exist");
    }
    parent::checkRequirements();
  }

}