class ItemsImporter

class ItemsImporter implements ItemsImporterInterface {
  
  /**
   * The aggregator fetcher manager.
   *
   * @var \Drupal\aggregator\Plugin\AggregatorPluginManager
   */
  protected $fetcherManager;
  
  /**
   * The aggregator processor manager.
   *
   * @var \Drupal\aggregator\Plugin\AggregatorPluginManager
   */
  protected $processorManager;
  
  /**
   * The aggregator parser manager.
   *
   * @var \Drupal\aggregator\Plugin\AggregatorPluginManager
   */
  protected $parserManager;
  
  /**
   * The aggregator.settings config object.
   *
   * @var \Drupal\Core\Config\Config
   */
  protected $config;
  
  /**
   * A logger instance.
   *
   * @var \Psr\Log\LoggerInterface
   */
  protected $logger;
  
  /**
   * Constructs an Importer object.
   *
   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
   *   The factory for configuration objects.
   * @param \Drupal\aggregator\Plugin\AggregatorPluginManager $fetcher_manager
   *   The aggregator fetcher plugin manager.
   * @param \Drupal\aggregator\Plugin\AggregatorPluginManager $parser_manager
   *   The aggregator parser plugin manager.
   * @param \Drupal\aggregator\Plugin\AggregatorPluginManager $processor_manager
   *   The aggregator processor plugin manager.
   * @param \Psr\Log\LoggerInterface $logger
   *   A logger instance.
   */
  public function __construct(ConfigFactoryInterface $config_factory, AggregatorPluginManager $fetcher_manager, AggregatorPluginManager $parser_manager, AggregatorPluginManager $processor_manager, LoggerInterface $logger) {
    $this->fetcherManager = $fetcher_manager;
    $this->processorManager = $processor_manager;
    $this->parserManager = $parser_manager;
    $this->config = $config_factory->get('aggregator.settings');
    $this->logger = $logger;
  }
  
  /**
   * {@inheritdoc}
   */
  public function delete(FeedInterface $feed) {
    foreach ($this->processorManager
      ->getDefinitions() as $id => $definition) {
      $this->processorManager
        ->createInstance($id)
        ->delete($feed);
    }
  }
  
  /**
   * {@inheritdoc}
   */
  public function refresh(FeedInterface $feed) {
    // Store feed URL to track changes.
    $feed_url = $feed->getUrl();
    // Fetch the feed.
    try {
      $success = $this->fetcherManager
        ->createInstance($this->config
        ->get('fetcher'))
        ->fetch($feed);
    } catch (PluginException $e) {
      $success = FALSE;
      watchdog_exception('aggregator', $e);
    }
    // Store instances in an array so we don't have to instantiate new objects.
    $processor_instances = [];
    foreach ($this->config
      ->get('processors') as $processor) {
      try {
        $processor_instances[$processor] = $this->processorManager
          ->createInstance($processor);
      } catch (PluginException $e) {
        watchdog_exception('aggregator', $e);
      }
    }
    // We store the hash of feed data in the database. When refreshing a
    // feed we compare stored hash and new hash calculated from downloaded
    // data. If both are equal we say that feed is not updated.
    $hash = $success ? hash('sha256', $feed->source_string) : '';
    $has_new_content = $success && $feed->getHash() != $hash;
    if ($has_new_content) {
      // Parse the feed.
      try {
        if ($this->parserManager
          ->createInstance($this->config
          ->get('parser'))
          ->parse($feed)) {
          if (!$feed->getWebsiteUrl()) {
            $feed->setWebsiteUrl($feed->getUrl());
          }
          $feed->setHash($hash);
          // Update feed with parsed data.
          $feed->save();
          // Log if feed URL has changed.
          if ($feed->getUrl() != $feed_url) {
            $this->logger
              ->notice('Updated URL for feed %title to %url.', [
              '%title' => $feed->label(),
              '%url' => $feed->getUrl(),
            ]);
          }
          $this->logger
            ->notice('There is new syndicated content from %site.', [
            '%site' => $feed->label(),
          ]);
          // If there are items on the feed, let enabled processors process them.
          if (!empty($feed->items)) {
            foreach ($processor_instances as $instance) {
              $instance->process($feed);
            }
          }
        }
      } catch (PluginException $e) {
        watchdog_exception('aggregator', $e);
      }
    }
    // Processing is done, call postProcess on enabled processors.
    foreach ($processor_instances as $instance) {
      $instance->postProcess($feed);
    }
    return $has_new_content;
  }

}