abstract class DrupalSqlBase

abstract class DrupalSqlBase extends SqlBase implements DependentPluginInterface {
  use DependencyTrait;

  /**
   * The contents of the system table.
   *
   * @var array
   */
  protected $systemData;

  /**
   * If the source provider is missing.
   *
   * @var bool
   */
  protected $requirements = TRUE;

  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;

  /**
   * {@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);
    $this->entityTypeManager = $entity_type_manager;
  }

  /**
   * Retrieves all system data information from the source Drupal database.
   *
   * @return array
   *   List of system table information keyed by type and name.
   */
  public function getSystemData() {
    if (!isset($this->systemData)) {
      $this->systemData = [];
      try {
        $results = $this
          ->select('system', 's')
          ->fields('s')
          ->execute();
        foreach ($results as $result) {
          $this->systemData[$result['type']][$result['name']] = $result;
        }
      } catch (\Exception $e) {

        // The table might not exist for example in tests.
      }
    }
    return $this->systemData;
  }

  /**
   * {@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('state'), $container
      ->get('entity_type.manager'));
  }

  /**
   * {@inheritdoc}
   */
  public function checkRequirements() {
    parent::checkRequirements();
    if ($this->pluginDefinition['requirements_met'] === TRUE) {
      if ($source_module = $this
        ->getSourceModule()) {
        if ($this
          ->moduleExists($source_module)) {
          if (isset($this->pluginDefinition['minimum_version'])) {
            $minimum_version = (int) $this->pluginDefinition['minimum_version'];
            $installed_version = (int) $this
              ->getModuleSchemaVersion($source_module);
            if ($minimum_version > $installed_version) {
              throw new RequirementsException('Required minimum version ' . $this->pluginDefinition['minimum_version'], [
                'minimum_version' => $this->pluginDefinition['minimum_version'],
              ]);
            }
          }
        }
        else {
          throw new RequirementsException('The module ' . $source_module . ' is not enabled in the source site.', [
            'source_module' => $source_module,
          ]);
        }
      }
    }
  }

  /**
   * Retrieves a module schema_version from the source Drupal database.
   *
   * @param string $module
   *   Name of module.
   *
   * @return mixed
   *   The current module schema version on the origin system table or FALSE if
   *   not found.
   */
  protected function getModuleSchemaVersion($module) {
    $system_data = $this
      ->getSystemData();
    return $system_data['module'][$module]['schema_version'] ?? FALSE;
  }

  /**
   * Checks if a given module is enabled in the source Drupal database.
   *
   * @param string $module
   *   Name of module to check.
   *
   * @return bool
   *   TRUE if module is enabled on the origin system, FALSE if not.
   */
  protected function moduleExists($module) {
    $system_data = $this
      ->getSystemData();
    return !empty($system_data['module'][$module]['status']);
  }

  /**
   * Reads a variable from a source Drupal database.
   *
   * @param $name
   *   Name of the variable.
   * @param $default
   *   The default value.
   *
   * @return mixed
   */
  protected function variableGet($name, $default) {
    try {
      $result = $this
        ->select('variable', 'v')
        ->fields('v', [
        'value',
      ])
        ->condition('name', $name)
        ->execute()
        ->fetchField();
    } catch (\Exception $e) {
      $result = FALSE;
    }
    return $result !== FALSE ? unserialize($result) : $default;
  }

  /**
   * {@inheritdoc}
   */
  public function calculateDependencies() {

    // Generic handling for Drupal source plugin constants.
    if (isset($this->configuration['constants']['entity_type'])) {
      $this
        ->addDependency('module', $this->entityTypeManager
        ->getDefinition($this->configuration['constants']['entity_type'])
        ->getProvider());
    }
    if (isset($this->configuration['constants']['module'])) {
      $this
        ->addDependency('module', $this->configuration['constants']['module']);
    }
    return $this->dependencies;
  }

}