class LibraryItemController

class LibraryItemController extends ControllerBase implements ContainerInjectionInterface {

  /**
   * The date formatter service.
   *
   * @var \Drupal\Core\Datetime\DateFormatterInterface
   */
  protected $dateFormatter;

  /**
   * The entity type manager.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;

  /**
   * The renderer service.
   *
   * @var \Drupal\Core\Render\Renderer
   */
  protected $renderer;

  /**
   * LibraryItemController constructor.
   *
   * @param \Drupal\Core\Datetime\DateFormatterInterface $date_formatter
   *   The date formatter service.
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager service.
   * @param \Drupal\Core\Render\Renderer $renderer
   *   The renderer service.
   */
  public function __construct(DateFormatterInterface $date_formatter, EntityTypeManagerInterface $entity_type_manager, Renderer $renderer) {
    $this->dateFormatter = $date_formatter;
    $this->entityTypeManager = $entity_type_manager;
    $this->renderer = $renderer;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container
      ->get('date.formatter'), $container
      ->get('entity_type.manager'), $container
      ->get('renderer'));
  }

  /**
   * Generates an overview table of older revisions of a library item.
   *
   * @param \Drupal\paragraphs_library\Entity\LibraryItem $paragraphs_library_item
   *   A library item object.
   *
   * @return array
   *   An array as expected by drupal_render()
   */
  public function revisionOverview(LibraryItem $paragraphs_library_item) {
    $label = $paragraphs_library_item
      ->get('label')->value;
    $build['#title'] = $this
      ->t('Revisions for %label', [
      '%label' => $label,
    ]);
    $header = [
      $this
        ->t('Revision'),
      $this
        ->t('Operations'),
    ];
    $rows = [];
    $default_revision = $paragraphs_library_item
      ->getRevisionId();
    $storage = $this->entityTypeManager
      ->getStorage('paragraphs_library_item');
    foreach ($this
      ->getRevisionIds($paragraphs_library_item) as $revision_id) {
      $revision = $storage
        ->loadRevision($revision_id);
      $date = $this->dateFormatter
        ->format($revision
        ->get('revision_created')->value, 'short');
      $row = [];
      $username = [
        '#theme' => 'username',
        '#account' => $revision
          ->getRevisionUser(),
      ];
      $column = [
        'data' => [
          '#type' => 'inline_template',
          '#template' => '{% trans %}{{ date }}: {{ label }} by {{ author }}{% endtrans %}{% if message %}<p class="revision-log">{{ message }}</p>{% endif %}',
          '#context' => [
            'date' => $revision
              ->toLink($date, $revision
              ->isDefaultRevision() ? 'canonical' : 'revision')
              ->toString(),
            'label' => $revision
              ->label(),
            'author' => $this->renderer
              ->renderPlain($username),
            'message' => [
              '#markup' => $revision
                ->get('revision_log')->value,
              '#allowed_tags' => Xss::getHtmlTagList(),
            ],
          ],
        ],
      ];
      $row[] = $column;
      if ($revision_id == $default_revision) {
        $row[] = [
          'data' => [
            '#prefix' => '<em>',
            '#markup' => $this
              ->t('Current revision'),
            '#suffix' => '</em>',
          ],
        ];
        $rows[] = [
          'data' => $row,
          'class' => [
            'revision-current',
          ],
        ];
      }
      else {
        $links = [
          'revert' => [
            'title' => $revision_id < $paragraphs_library_item
              ->getRevisionId() ? $this
              ->t('Revert') : $this
              ->t('Set as current revision'),
            'url' => $revision
              ->toUrl('revision-revert'),
          ],
          'delete' => [
            'title' => $this
              ->t('Delete'),
            'url' => $revision
              ->toUrl('revision-delete'),
          ],
        ];
        $row[] = [
          'data' => [
            '#type' => 'operations',
            '#links' => $links,
          ],
        ];
        $rows[] = $row;
      }
    }
    $build['paragraphs_library_item_revisions_table'] = [
      '#theme' => 'table',
      '#header' => $header,
      '#rows' => $rows,
    ];
    $build['pager'] = [
      '#type' => 'pager',
    ];
    return $build;
  }

  /**
   * Page title callback for library item revision.
   *
   * @param int $paragraphs_library_item_revision
   *   The library item revision ID.
   *
   * @return string
   *   The page title.
   */
  public function revisionPageTitle($paragraphs_library_item_revision) {
    $library_item = $this->entityTypeManager
      ->getStorage('paragraphs_library_item')
      ->loadRevision($paragraphs_library_item_revision);
    return $this
      ->t('Revision of %title from %date', [
      '%title' => $library_item
        ->label(),
      '%date' => $this->dateFormatter
        ->format($library_item
        ->getChangedTime()),
    ]);
  }

  /**
   *  Display a library item revision.
   *
   * @param int $paragraphs_library_item_revision
   *   The library item revision ID.
   *
   * @return array
   *   An array suitable for drupal_render().
   */
  public function revisionShow($paragraphs_library_item_revision) {
    $library_item = $this->entityTypeManager
      ->getStorage('paragraphs_library_item')
      ->loadRevision($paragraphs_library_item_revision);
    $view = $this->entityTypeManager
      ->getViewBuilder('paragraphs_library_item')
      ->view($library_item);
    return $view;
  }

  /**
   * Gets a list of library item revision IDs for a specific library item.
   *
   * @param \Drupal\paragraphs_library\LibraryItemInterface $library_item
   *   Library item entity.
   *
   * @return int[]
   *   Library item revision IDs (in descending order)
   */
  protected function getRevisionIds(LibraryItemInterface $library_item) {
    $result = $this->entityTypeManager
      ->getStorage('paragraphs_library_item')
      ->getQuery()
      ->allRevisions()
      ->condition('id', $library_item
      ->id())
      ->accessCheck(TRUE)
      ->sort($library_item
      ->getEntityType()
      ->getKey('revision'), 'DESC')
      ->pager(50)
      ->execute();
    return array_keys($result);
  }

}