class EventSubscriber

class EventSubscriber implements EventSubscriberInterface {
    
    /**
     * Constructs the Event Subscriber object.
     *
     * @param \Drupal\Core\State\StateInterface $state
     *   The state key value store.
     */
    public function __construct(StateInterface $state) {
    }
    
    /**
     * Reacts to config event.
     *
     * @param \Drupal\language\Config\LanguageConfigOverrideCrudEvent $event
     *   The language configuration event.
     * @param string $event_name
     *   The event name.
     */
    public function configEventRecorder(LanguageConfigOverrideCrudEvent $event, string $event_name) : void {
        $override = $event->getLanguageConfigOverride();
        $event_info = [
            'event_name' => $event_name,
            'current_override_data' => $override->get(),
            'original_override_data' => $override->getOriginal(),
        ];
        // Record all events that occur.
        $all_events = $this->state
            ->get('language_events_test.all_events', []);
        $override_name = $override->getName();
        if (!isset($all_events[$event_name][$override_name])) {
            $all_events[$event_name][$override_name] = [];
        }
        $all_events[$event_name][$override_name][] = $event_info;
        $this->state
            ->set('language_events_test.all_events', $all_events);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        $events[LanguageConfigOverrideEvents::SAVE_OVERRIDE][] = [
            'configEventRecorder',
        ];
        $events[LanguageConfigOverrideEvents::DELETE_OVERRIDE][] = [
            'configEventRecorder',
        ];
        return $events;
    }

}