class TestProcessor

class TestProcessor extends AggregatorPluginSettingsBase implements ProcessorInterface, ContainerFactoryPluginInterface {
    use ConfigFormBaseTrait;
    
    /**
     * Contains the configuration object factory.
     *
     * @var \Drupal\Core\Config\ConfigFactoryInterface
     */
    protected $configFactory;
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('config.factory'));
    }
    
    /**
     * Constructs a TestProcessor object.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config
     *   The configuration factory object.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, ConfigFactoryInterface $config) {
        $this->configFactory = $config;
        parent::__construct($configuration + $this->getConfiguration(), $plugin_id, $plugin_definition);
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getEditableConfigNames() {
        return [
            'aggregator_test.settings',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
        $processors = $this->config('aggregator.settings')
            ->get('processors');
        $info = $this->getPluginDefinition();
        $form['processors'][$info['id']] = [
            '#type' => 'details',
            '#title' => t('Test processor settings'),
            '#description' => $info['description'],
            '#open' => in_array($info['id'], $processors),
        ];
        // Add some dummy settings to verify settingsForm is called.
        $form['processors'][$info['id']]['dummy_length'] = [
            '#title' => t('Dummy length setting'),
            '#type' => 'number',
            '#min' => 1,
            '#max' => 1000,
            '#default_value' => $this->configuration['items']['dummy_length'],
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
        $this->configuration['items']['dummy_length'] = $form_state->getValue('dummy_length');
        $this->setConfiguration($this->configuration);
    }
    
    /**
     * {@inheritdoc}
     */
    public function process(FeedInterface $feed) {
        foreach ($feed->items as &$item) {
            // Prepend our test string.
            $item['title'] = 'testProcessor' . $item['title'];
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function delete(FeedInterface $feed) {
        // Append a random number, just to change the feed description.
        $feed->description->value .= rand(0, 10);
    }
    
    /**
     * {@inheritdoc}
     */
    public function postProcess(FeedInterface $feed) {
        // Double the refresh rate.
        $feed->refresh->value *= 2;
        $feed->save();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getConfiguration() {
        return $this->configFactory
            ->get('aggregator_test.settings')
            ->get();
    }
    
    /**
     * {@inheritdoc}
     */
    public function setConfiguration(array $configuration) {
        $config = $this->config('aggregator_test.settings');
        foreach ($configuration as $key => $value) {
            $config->set($key, $value);
        }
        $config->save();
    }

}