class EntityReferenceAjaxFormatter

class EntityReferenceAjaxFormatter extends EntityReferenceEntityFormatter implements ContainerFactoryPluginInterface {
    
    /**
     * The current route match.
     *
     * @var \Drupal\Core\Routing\CurrentRouteMatch
     */
    protected CurrentRouteMatch $currentRoute;
    
    /**
     * Constructs a EntityReferenceAjaxFormatter instance.
     *
     * @param string $plugin_id
     *   The plugin_id for the formatter.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The definition of the field to which the formatter is associated.
     * @param mixed[] $settings
     *   The formatter settings.
     * @param string $label
     *   The formatter label display setting.
     * @param string $view_mode
     *   The view mode.
     * @param mixed[] $third_party_settings
     *   Any third party settings settings.
     * @param \Drupal\Core\Logger\LoggerChannelFactoryInterface $logger_factory
     *   The logger factory.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Entity\EntityDisplayRepositoryInterface $entity_display_repository
     *   The entity display repository.
     * @param \Drupal\Core\Routing\CurrentRouteMatch $current_route
     *   The current route.
     */
    public function __construct(string $plugin_id, mixed $plugin_definition, FieldDefinitionInterface $field_definition, array $settings, string $label, string $view_mode, array $third_party_settings, LoggerChannelFactoryInterface $logger_factory, EntityTypeManagerInterface $entity_type_manager, EntityDisplayRepositoryInterface $entity_display_repository, CurrentRouteMatch $current_route) {
        $this->currentRoute = $current_route;
        if ($current_route->getRouteName() === 'entity_reference_ajax_formatter.ajax_field') {
            $label = 'hidden';
        }
        parent::__construct($plugin_id, $plugin_definition, $field_definition, $settings, $label, $view_mode, $third_party_settings, $logger_factory, $entity_type_manager, $entity_display_repository);
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsForm(array $form, FormStateInterface $form_state) {
        $elements = parent::settingsForm($form, $form_state);
        $elements['number'] = [
            '#type' => 'number',
            '#title' => $this->t('Number of entities to load'),
            '#step' => 1,
            '#default_value' => $this->getSetting('number'),
            '#required' => TRUE,
        ];
        $elements['sort'] = [
            '#type' => 'select',
            '#title' => $this->t('Sort'),
            '#options' => [
                $this->t('Field Default Order'),
                $this->t('Random'),
                $this->t('Date Modified (ascending)'),
                $this->t('Date Modified (descending)'),
                $this->t('Date Created (ascending)'),
                $this->t('Date Created (descending)'),
            ],
            '#default_value' => $this->getSetting('sort'),
            '#required' => TRUE,
        ];
        $elements['load_more'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Load More'),
            '#default_value' => $this->getSetting('load_more'),
            '#description' => $this->t('Provide load more by AJAX functionality.'),
        ];
        $maxSetting = $this->getSetting('max');
        $elements['max'] = [
            '#type' => 'number',
            '#title' => $this->t('Max'),
            '#description' => $this->t('The maximum to load via load more. Select 0 for unlimited.'),
            '#default_value' => $maxSetting == 0 ? $maxSetting : max($maxSetting, $this->getSetting('number') + 1),
            '#states' => [
                'visible' => [
                    ':input[name$="[load_more]"]' => [
                        'checked' => TRUE,
                    ],
                ],
            ],
            '#element_validate' => [
                [
                    $this,
                    'settingsMaxValidate',
                ],
            ],
        ];
        return $elements;
    }
    
    /**
     * Use element validator to make sure that hex values are in correct format.
     *
     * @param mixed[] $element
     *   The Default colors element.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     */
    public function settingsMaxValidate(array $element, FormStateInterface $form_state) {
        $max = $form_state->getValue($element['#parents']);
        if (intval($max) === 0) {
            return;
        }
        $form = $element['#parents'];
        array_pop($form);
        $values = $form_state->getValue($form);
        if ($values['load_more']) {
            if ($max <= $values['number']) {
                $form_state->setError($element, $this->t('Max must be greater than the initial load number if Load More is enabled. You can set to 0 no limit.'));
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsSummary() {
        $summary = parent::settingsSummary();
        $summary[] = $this->t('Loading %items', [
            '%items' => $this->getSetting('number'),
        ]);
        if ($this->getSetting('sort')) {
            $summary[] = $this->t('Sort: %sort', [
                '%sort' => [
                    $this->t('Field Default Order'),
                    $this->t('Random'),
                    $this->t('Date Modified (ascending)'),
                    $this->t('Date Modified (descending)'),
                    $this->t('Date Created (ascending)'),
                    $this->t('Date Created (descending)'),
                ][$this->getSetting('sort')],
            ]);
        }
        if ($this->getSetting('load_more')) {
            $summary[] = $this->t('Load more button enabled');
            if ($this->getSetting('max')) {
                $summary[] = $this->t('Maximum entities to load: %max', [
                    '%max' => $this->getSetting('max'),
                ]);
            }
        }
        return $summary;
    }
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        $view_mode = $this->getSetting('view_mode');
        $elements = [];
        $parameters = $this->currentRoute
            ->getParameters();
        $start = $parameters->get('start') ? $parameters->get('start') : 0;
        $printed = [];
        if ($parameters->get('printed')) {
            $printed = explode('-', $parameters->get('printed'));
        }
        $count = $this->getSetting('number');
        $max = $this->getSetting('max');
        $id = "ajax-field-{$this->fieldDefinition->getTargetEntityTypeId()}-{$items->getEntity()->id()}-{$this->fieldDefinition->getName()}";
        $entities = $this->getEntitiesToView($items, $langcode);
        switch ($this->getSetting('sort')) {
            case 1:
                shuffle($entities);
                break;
            case 2:
                usort($entities, function (ContentEntityInterface $a, ContentEntityInterface $b) {
                    if (method_exists($a, 'getChangedTime') && method_exists($b, 'getChangedTime')) {
                        return $a->getChangedTime() <=> $b->getChangedTime();
                    }
                    // If entity doesn't have changed time record, return order unchanged.
                    return 0;
                });
                break;
            case 3:
                usort($entities, function (ContentEntityInterface $a, ContentEntityInterface $b) {
                    if (method_exists($a, 'getChangedTime') && method_exists($b, 'getChangedTime')) {
                        return -1 * ($a->getChangedTime() <=> $b->getChangedTime());
                    }
                    // If entity doesn't have changed time record, return order unchanged.
                    return 0;
                });
                rsort($entities);
                break;
            case 4:
                usort($entities, function ($a, $b) {
                    if (method_exists($a, 'getCreatedTime') && method_exists($b, 'getCreatedTime')) {
                        return $a->getCreatedTime() <=> $b->getCreatedTime();
                    }
                    // If entity doesn't have created time record, return order unchanged.
                    return 0;
                });
                break;
            case 5:
                usort($entities, function ($a, $b) {
                    if (method_exists($a, 'getCreatedTime') && method_exists($b, 'getCreatedTime')) {
                        return -1 * ($a->getCreatedTime() <=> $b->getCreatedTime());
                    }
                    // If entity doesn't have created time record, return order unchanged.
                    return 0;
                });
                break;
        }
        foreach ($entities as $delta => $entity) {
            if (count($elements) >= $count) {
                break;
            }
            if ($this->getSetting('sort') === 1) {
                if (in_array($entity->id(), $printed)) {
                    continue;
                }
                $printed[] = $entity->id();
            }
            elseif ($start > $delta) {
                continue;
            }
            if ($max && count($elements) + $start >= $max) {
                break;
            }
            // Due to render caching and delayed calls, the viewElements() method
            // will be called later in the rendering process through a '#pre_render'
            // callback, so we need to generate a counter that takes into account
            // all the relevant information about this field and the referenced
            // entity that is being rendered.
            $recursive_render_id = $items->getFieldDefinition()
                ->getTargetEntityTypeId() . $items->getFieldDefinition()
                ->getTargetBundle() . $items->getName() . $items->getEntity()
                ->id() . $entity->getEntityTypeId() . $entity->id();
            if (isset(static::$recursiveRenderDepth[$recursive_render_id])) {
                static::$recursiveRenderDepth[$recursive_render_id]++;
            }
            else {
                static::$recursiveRenderDepth[$recursive_render_id] = 1;
            }
            // Protect ourselves from recursive rendering.
            if (static::$recursiveRenderDepth[$recursive_render_id] > static::RECURSIVE_RENDER_LIMIT) {
                $this->loggerFactory
                    ->get('entity')
                    ->error('Recursive rendering detected when rendering entity %entity_type: %entity_id, using the %field_name field on the %bundle_name bundle. Aborting rendering.', [
                    '%entity_type' => $entity->getEntityTypeId(),
                    '%entity_id' => $entity->id(),
                    '%field_name' => $items->getName(),
                    '%bundle_name' => $items->getFieldDefinition()
                        ->getTargetBundle(),
                ]);
                return $elements;
            }
            $view_builder = $this->entityTypeManager
                ->getViewBuilder($entity->getEntityTypeId());
            $elements[$delta] = $view_builder->view($entity, $view_mode, $entity->language()
                ->getId());
            // Add a resource attribute to set the mapping property's value to the
            // entity's url. Since we don't know what the markup of the entity will
            // be, we shouldn't rely on it for structured data such as RDFa.
            if (!empty($items[$delta]->_attributes) && !$entity->isNew() && $entity->hasLinkTemplate('canonical')) {
                $items[$delta]->_attributes += [
                    'resource' => $entity->toUrl()
                        ->toString(),
                ];
            }
        }
        $total = $count + $start;
        if ($this->getSetting('load_more') && count($items) > $total && (!$max || $max > $total)) {
            $elements[$delta + 1] = [
                '#type' => 'container',
                '#attributes' => [
                    'class' => [
                        'text-align-center',
                        'ajax-field-entity-ref',
                    ],
                    'id' => $id,
                ],
            ];
            $elements[$delta + 1]['more'] = [
                '#type' => 'link',
                '#title' => t('Load More'),
                '#url' => Url::fromRoute('entity_reference_ajax_formatter.ajax_field', [
                    'entity_type' => $this->fieldDefinition
                        ->getTargetEntityTypeId(),
                    'entity' => $items->getEntity()
                        ->id(),
                    'field_name' => $this->fieldDefinition
                        ->getName(),
                    'view_mode' => $this->viewMode,
                    'language' => $langcode,
                    'start' => $start + count($elements) - 1,
                    'printed' => implode('-', $printed),
                ]),
                '#attributes' => [
                    'class' => [
                        'use-ajax',
                    ],
                ],
            ];
            $elements['#attached']['library'][] = 'core/drupal.ajax';
        }
        return $elements;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($plugin_id, $plugin_definition, $configuration['field_definition'], $configuration['settings'], $configuration['label'], $configuration['view_mode'], $configuration['third_party_settings'], $container->get('logger.factory'), $container->get('entity_type.manager'), $container->get('entity_display.repository'), $container->get('current_route_match'));
    }
    
    /**
     * {@inheritdoc}
     */
    public static function defaultSettings() {
        return [
            'load_more' => FALSE,
            'max' => 0,
            'number' => 6,
            'sort' => 0,
        ] + parent::defaultSettings();
    }

}