abstract class LinkBase

abstract class LinkBase extends FieldPluginBase {
  use RedirectDestinationTrait;
  use EntityTranslationRenderTrait;

  /**
   * The access manager service.
   *
   * @var \Drupal\Core\Access\AccessManagerInterface
   */
  protected $accessManager;

  /**
   * Current user object.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $currentUser;

  /**
   * The language manager.
   *
   * @var \Drupal\Core\Language\LanguageManagerInterface
   */
  protected $languageManager;

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

  /**
   * The entity repository.
   *
   * @var \Drupal\Core\Entity\EntityRepositoryInterface
   */
  protected $entityRepository;

  /**
   * Constructs a LinkBase object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param mixed $plugin_definition
   *   The plugin implementation definition.
   * @param \Drupal\Core\Access\AccessManagerInterface $access_manager
   *   The access manager.
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
   *   The entity type manager.
   * @param \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository
   *   The entity repository.
   * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
   *   The language manager.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, AccessManagerInterface $access_manager, EntityTypeManagerInterface $entity_type_manager, EntityRepositoryInterface $entity_repository, LanguageManagerInterface $language_manager) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->accessManager = $access_manager;
    $this->entityTypeManager = $entity_type_manager;
    $this->entityRepository = $entity_repository;
    $this->languageManager = $language_manager;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($configuration, $plugin_id, $plugin_definition, $container
      ->get('access_manager'), $container
      ->get('entity_type.manager'), $container
      ->get('entity.repository'), $container
      ->get('language_manager'));
  }

  /**
   * Gets the current active user.
   *
   * @todo: https://www.drupal.org/node/2105123 put this method in
   *   \Drupal\Core\Plugin\PluginBase instead.
   *
   * @return \Drupal\Core\Session\AccountInterface
   *   The current user.
   */
  protected function currentUser() {
    if (!$this->currentUser) {
      $this->currentUser = \Drupal::currentUser();
    }
    return $this->currentUser;
  }

  /**
   * {@inheritdoc}
   */
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['text'] = [
      'default' => $this
        ->getDefaultLabel(),
    ];
    return $options;
  }

  /**
   * {@inheritdoc}
   */
  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
    $form['text'] = [
      '#type' => 'textfield',
      '#title' => $this
        ->t('Text to display'),
      '#default_value' => $this->options['text'],
    ];
    parent::buildOptionsForm($form, $form_state);

    // The path is set by ::renderLink() so we do not allow to set it.
    $form['alter'] += [
      'path' => [],
      'query' => [],
      'external' => [],
    ];
    $form['alter']['path'] += [
      '#access' => FALSE,
    ];
    $form['alter']['query'] += [
      '#access' => FALSE,
    ];
    $form['alter']['external'] += [
      '#access' => FALSE,
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function usesGroupBy() {
    return FALSE;
  }

  /**
   * {@inheritdoc}
   */
  public function query() {
    if ($this->languageManager
      ->isMultilingual()) {
      $this
        ->getEntityTranslationRenderer()
        ->query($this->query, $this->relationship);
    }
    $this
      ->addAdditionalFields();
  }

  /**
   * {@inheritdoc}
   */
  public function render(ResultRow $row) {
    $access = $this
      ->checkUrlAccess($row);
    if ($access) {
      $build = [
        '#markup' => $access
          ->isAllowed() ? $this
          ->renderLink($row) : '',
      ];
      BubbleableMetadata::createFromObject($access)
        ->applyTo($build);
      return $build;
    }
    return '';
  }

  /**
   * Checks access to the link route.
   *
   * @param \Drupal\views\ResultRow $row
   *   A view result row.
   *
   * @return \Drupal\Core\Access\AccessResultInterface|null
   *   The access result, or NULL if the URI elements of the link doesn't exist.
   */
  protected function checkUrlAccess(ResultRow $row) {
    if ($url = $this
      ->getUrlInfo($row)) {
      return $this->accessManager
        ->checkNamedRoute($url
        ->getRouteName(), $url
        ->getRouteParameters(), $this
        ->currentUser(), TRUE);
    }
  }

  /**
   * Returns the URI elements of the link.
   *
   * @param \Drupal\views\ResultRow $row
   *   A view result row.
   *
   * @return \Drupal\Core\Url|null
   *   The URI elements of the link.
   */
  protected abstract function getUrlInfo(ResultRow $row);

  /**
   * Prepares the link to view an entity.
   *
   * @param \Drupal\views\ResultRow $row
   *   A view result row.
   *
   * @return string
   *   Returns a string for the link text.
   */
  protected function renderLink(ResultRow $row) {
    $this->options['alter']['make_link'] = TRUE;
    $this->options['alter']['url'] = $this
      ->getUrlInfo($row);
    $text = !empty($this->options['text']) ? $this
      ->sanitizeValue($this->options['text']) : $this
      ->getDefaultLabel();
    $this
      ->addLangcode($row);
    return $text;
  }

  /**
   * Adds language information to the options.
   *
   * @param \Drupal\views\ResultRow $row
   *   A view result row.
   */
  protected function addLangcode(ResultRow $row) {
    $entity = $this
      ->getEntity($row);
    if ($entity && $this->languageManager
      ->isMultilingual()) {
      $this->options['alter']['language'] = $this
        ->getEntityTranslationByRelationship($entity, $row)
        ->language();
    }
  }

  /**
   * Returns the default label for this link.
   *
   * @return \Drupal\Core\StringTranslation\TranslatableMarkup
   *   The default link label.
   */
  protected function getDefaultLabel() {
    return $this
      ->t('link');
  }

  /**
   * {@inheritdoc}
   */
  protected function getEntityTypeId() {
    return $this
      ->getEntityType();
  }

  /**
   * {@inheritdoc}
   */
  protected function getEntityTypeManager() {
    return $this->entityTypeManager;
  }

  /**
   * {@inheritdoc}
   */
  protected function getEntityRepository() {
    return $this->entityRepository;
  }

  /**
   * {@inheritdoc}
   */
  protected function getLanguageManager() {
    return $this->languageManager;
  }

  /**
   * {@inheritdoc}
   */
  protected function getView() {
    return $this->view;
  }

}