class ResponsiveImageFormatter

class ResponsiveImageFormatter extends ImageFormatterBase {
    
    /**
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $responsiveImageStyleStorage;
    
    /**
     * The image style entity storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $imageStyleStorage;
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * The link generator.
     *
     * @var \Drupal\Core\Utility\LinkGeneratorInterface
     */
    protected $linkGenerator;
    
    /**
     * Constructs a ResponsiveImageFormatter object.
     *
     * @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 array $settings
     *   The formatter settings.
     * @param string $label
     *   The formatter label display setting.
     * @param string $view_mode
     *   The view mode.
     * @param array $third_party_settings
     *   Any third party settings.
     * @param \Drupal\Core\Entity\EntityStorageInterface $responsive_image_style_storage
     *   The responsive image style storage.
     * @param \Drupal\Core\Entity\EntityStorageInterface $image_style_storage
     *   The image style storage.
     * @param \Drupal\Core\Utility\LinkGeneratorInterface $link_generator
     *   The link generator service.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     */
    public function __construct($plugin_id, $plugin_definition, FieldDefinitionInterface $field_definition, array $settings, $label, $view_mode, array $third_party_settings, EntityStorageInterface $responsive_image_style_storage, EntityStorageInterface $image_style_storage, LinkGeneratorInterface $link_generator, AccountInterface $current_user) {
        parent::__construct($plugin_id, $plugin_definition, $field_definition, $settings, $label, $view_mode, $third_party_settings);
        $this->responsiveImageStyleStorage = $responsive_image_style_storage;
        $this->imageStyleStorage = $image_style_storage;
        $this->linkGenerator = $link_generator;
        $this->currentUser = $current_user;
    }
    
    /**
     * {@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('entity_type.manager')
            ->getStorage('responsive_image_style'), $container->get('entity_type.manager')
            ->getStorage('image_style'), $container->get('link_generator'), $container->get('current_user'));
    }
    
    /**
     * {@inheritdoc}
     */
    public static function defaultSettings() {
        return [
            'responsive_image_style' => '',
            'image_link' => '',
            'image_loading' => [
                'attribute' => 'lazy',
            ],
        ] + parent::defaultSettings();
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsForm(array $form, FormStateInterface $form_state) {
        $elements = parent::settingsForm($form, $form_state);
        $responsive_image_options = [];
        $responsive_image_styles = $this->responsiveImageStyleStorage
            ->loadMultiple();
        uasort($responsive_image_styles, '\\Drupal\\responsive_image\\Entity\\ResponsiveImageStyle::sort');
        if ($responsive_image_styles && !empty($responsive_image_styles)) {
            foreach ($responsive_image_styles as $machine_name => $responsive_image_style) {
                if ($responsive_image_style->hasImageStyleMappings()) {
                    $responsive_image_options[$machine_name] = $responsive_image_style->label();
                }
            }
        }
        $elements['responsive_image_style'] = [
            '#title' => $this->t('Responsive image style'),
            '#type' => 'select',
            '#default_value' => $this->getSetting('responsive_image_style') ?: NULL,
            '#required' => TRUE,
            '#options' => $responsive_image_options,
            '#description' => [
                '#markup' => $this->linkGenerator
                    ->generate($this->t('Configure Responsive Image Styles'), new Url('entity.responsive_image_style.collection')),
                '#access' => $this->currentUser
                    ->hasPermission('administer responsive image styles'),
            ],
        ];
        $image_loading = $this->getSetting('image_loading');
        $elements['image_loading'] = [
            '#type' => 'details',
            '#title' => $this->t('Image loading'),
            '#weight' => 10,
            '#description' => $this->t('Lazy render images with native image loading attribute (<em>loading="lazy"</em>). This improves performance by allowing browsers to lazily load images. See <a href="@url">Lazy loading</a>.', [
                '@url' => 'https://developer.mozilla.org/en-US/docs/Web/Performance/Lazy_loading#images_and_iframes',
            ]),
        ];
        $loading_attribute_options = [
            'lazy' => $this->t('Lazy'),
            'eager' => $this->t('Eager'),
        ];
        $elements['image_loading']['attribute'] = [
            '#title' => $this->t('Lazy loading attribute'),
            '#type' => 'select',
            '#default_value' => $image_loading['attribute'],
            '#options' => $loading_attribute_options,
            '#description' => $this->t('Select the lazy loading attribute for images. <a href=":link">Learn more.</a>', [
                ':link' => 'https://html.spec.whatwg.org/multipage/urls-and-fetching.html#lazy-loading-attributes',
            ]),
        ];
        $link_types = [
            'content' => $this->t('Content'),
            'file' => $this->t('File'),
        ];
        $elements['image_link'] = [
            '#title' => $this->t('Link image to'),
            '#type' => 'select',
            '#default_value' => $this->getSetting('image_link'),
            '#empty_option' => $this->t('Nothing'),
            '#options' => $link_types,
        ];
        return $elements;
    }
    
    /**
     * {@inheritdoc}
     */
    public function settingsSummary() {
        $summary = [];
        $responsive_image_style = $this->responsiveImageStyleStorage
            ->load($this->getSetting('responsive_image_style'));
        if ($responsive_image_style) {
            $summary[] = $this->t('Responsive image style: @responsive_image_style', [
                '@responsive_image_style' => $responsive_image_style->label(),
            ]);
            $link_types = [
                'content' => $this->t('Linked to content'),
                'file' => $this->t('Linked to file'),
            ];
            // Display this setting only if image is linked.
            if (isset($link_types[$this->getSetting('image_link')])) {
                $summary[] = $link_types[$this->getSetting('image_link')];
            }
        }
        else {
            $summary[] = $this->t('Select a responsive image style.');
        }
        $image_loading = $this->getSetting('image_loading');
        $summary[] = $this->t('Loading attribute: @attribute', [
            '@attribute' => $image_loading['attribute'],
        ]);
        return array_merge($summary, parent::settingsSummary());
    }
    
    /**
     * {@inheritdoc}
     */
    public function viewElements(FieldItemListInterface $items, $langcode) {
        $elements = [];
        $files = $this->getEntitiesToView($items, $langcode);
        // Early opt-out if the field is empty.
        if (empty($files)) {
            return $elements;
        }
        $url = NULL;
        // Check if the formatter involves a link.
        if ($this->getSetting('image_link') == 'content') {
            $entity = $items->getEntity();
            if (!$entity->isNew()) {
                $url = $entity->toUrl();
            }
        }
        elseif ($this->getSetting('image_link') == 'file') {
            $link_file = TRUE;
        }
        // Collect cache tags to be added for each item in the field.
        $responsive_image_style = $this->responsiveImageStyleStorage
            ->load($this->getSetting('responsive_image_style'));
        $image_styles_to_load = [];
        $cache_tags = [];
        if ($responsive_image_style) {
            $cache_tags = Cache::mergeTags($cache_tags, $responsive_image_style->getCacheTags());
            $image_styles_to_load = $responsive_image_style->getImageStyleIds();
        }
        $image_styles = $this->imageStyleStorage
            ->loadMultiple($image_styles_to_load);
        foreach ($image_styles as $image_style) {
            $cache_tags = Cache::mergeTags($cache_tags, $image_style->getCacheTags());
        }
        foreach ($files as $delta => $file) {
            assert($file instanceof FileInterface);
            // Link the <picture> element to the original file.
            if (isset($link_file)) {
                $url = $file->createFileUrl();
            }
            // Extract field item attributes for the theme function, and unset them
            // from the $item so that the field template does not re-render them.
            $item = $file->_referringItem;
            $item_attributes = $item->_attributes;
            unset($item->_attributes);
            $image_loading_settings = $this->getSetting('image_loading');
            $item_attributes['loading'] = $image_loading_settings['attribute'];
            $elements[$delta] = [
                '#theme' => 'responsive_image_formatter',
                '#item' => $item,
                '#item_attributes' => $item_attributes,
                '#responsive_image_style_id' => $responsive_image_style ? $responsive_image_style->id() : '',
                '#url' => $url,
                '#cache' => [
                    'tags' => $cache_tags,
                ],
            ];
        }
        return $elements;
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        $dependencies = parent::calculateDependencies();
        $style_id = $this->getSetting('responsive_image_style');
        
        /** @var \Drupal\responsive_image\ResponsiveImageStyleInterface $style */
        if ($style_id && ($style = ResponsiveImageStyle::load($style_id))) {
            // Add the responsive image style as dependency.
            $dependencies[$style->getConfigDependencyKey()][] = $style->getConfigDependencyName();
        }
        return $dependencies;
    }

}