class EventSubscriber

class EventSubscriber implements EventSubscriberInterface {
    
    /**
     * The key value store.
     *
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * Constructs the event subscriber.
     *
     * @param \Drupal\Core\State\StateInterface $state
     *   The key value store.
     */
    public function __construct(StateInterface $state) {
        $this->state = $state;
    }
    
    /**
     * Validates the configuration to be imported.
     *
     * @param \Drupal\Core\Config\ConfigImporterEvent $event
     *   The Event to process.
     *
     * @throws \Drupal\Core\Config\ConfigNameException
     */
    public function onConfigImporterValidate(ConfigImporterEvent $event) {
        if ($this->state
            ->get('config_import_test.config_import_validate_fail', FALSE)) {
            // Log more than one error to test multiple validation errors.
            $event->getConfigImporter()
                ->logError('Config import validate error 1.');
            $event->getConfigImporter()
                ->logError('Config import validate error 2.');
        }
    }
    
    /**
     * Handles the missing content event.
     *
     * @param \Drupal\Core\Config\Importer\MissingContentEvent $event
     *   The missing content event.
     */
    public function onConfigImporterMissingContentOne(MissingContentEvent $event) {
        if ($this->state
            ->get('config_import_test.config_import_missing_content', FALSE) && $this->state
            ->get('config_import_test.config_import_missing_content_one', FALSE) === FALSE) {
            $missing = $event->getMissingContent();
            $uuid = key($missing);
            $this->state
                ->set('config_import_test.config_import_missing_content_one', key($missing));
            $event->resolveMissingContent($uuid);
            // Stopping propagation ensures that onConfigImporterMissingContentTwo
            // will be fired on the next batch step.
            $event->stopPropagation();
        }
    }
    
    /**
     * Handles the missing content event.
     *
     * @param \Drupal\Core\Config\Importer\MissingContentEvent $event
     *   The missing content event.
     */
    public function onConfigImporterMissingContentTwo(MissingContentEvent $event) {
        if ($this->state
            ->get('config_import_test.config_import_missing_content', FALSE) && $this->state
            ->get('config_import_test.config_import_missing_content_two', FALSE) === FALSE) {
            $missing = $event->getMissingContent();
            $uuid = key($missing);
            $this->state
                ->set('config_import_test.config_import_missing_content_two', key($missing));
            $event->resolveMissingContent($uuid);
        }
    }
    
    /**
     * Reacts to a config save and records information in state for testing.
     *
     * @param \Drupal\Core\Config\ConfigCrudEvent $event
     *   The event.
     */
    public function onConfigSave(ConfigCrudEvent $event) {
        $config = $event->getConfig();
        if ($config->getName() == 'automated_cron.settings') {
            $values = $this->state
                ->get('ConfigImportUITest.automated_cron.settings.interval', []);
            $values[] = $config->get('interval');
            $this->state
                ->set('ConfigImportUITest.automated_cron.settings.interval', $values);
        }
        if ($config->getName() == 'core.extension') {
            $installed = $this->state
                ->get('ConfigImportUITest.core.extension.modules_installed', []);
            $uninstalled = $this->state
                ->get('ConfigImportUITest.core.extension.modules_uninstalled', []);
            $original = $config->getOriginal('module');
            $data = $config->get('module');
            $install = array_diff_key($data, $original);
            if (!empty($install)) {
                $installed[] = key($install);
            }
            $uninstall = array_diff_key($original, $data);
            if (!empty($uninstall)) {
                $uninstalled[] = key($uninstall);
            }
            $this->state
                ->set('ConfigImportUITest.core.extension.modules_installed', $installed);
            $this->state
                ->set('ConfigImportUITest.core.extension.modules_uninstalled', $uninstalled);
        }
    }
    
    /**
     * Reacts to a config delete and records information in state for testing.
     *
     * @param \Drupal\Core\Config\ConfigCrudEvent $event
     *   The event.
     */
    public function onConfigDelete(ConfigCrudEvent $event) {
        $config = $event->getConfig();
        if ($config->getName() == 'automated_cron.settings') {
            $value = $this->state
                ->get('ConfigImportUITest.automated_cron.settings.delete', 0);
            $this->state
                ->set('ConfigImportUITest.automated_cron.settings.delete', $value + 1);
        }
    }
    
    /**
     * Registers the methods in this class that should be listeners.
     *
     * @return array
     *   An array of event listener definitions.
     */
    public static function getSubscribedEvents() : array {
        $events[ConfigEvents::SAVE][] = [
            'onConfigSave',
            40,
        ];
        $events[ConfigEvents::DELETE][] = [
            'onConfigDelete',
            40,
        ];
        $events[ConfigEvents::IMPORT_VALIDATE] = [
            'onConfigImporterValidate',
        ];
        $events[ConfigEvents::IMPORT_MISSING_CONTENT] = [
            [
                'onConfigImporterMissingContentOne',
            ],
            [
                'onConfigImporterMissingContentTwo',
                -100,
            ],
        ];
        return $events;
    }

}