class Block

class Block extends ConfigEntityBase implements BlockInterface, EntityWithPluginCollectionInterface {

  /**
   * The ID of the block.
   *
   * @var string
   */
  protected $id;

  /**
   * The plugin instance settings.
   *
   * @var array
   */
  protected $settings = [];

  /**
   * The region this block is placed in.
   *
   * @var string
   */
  protected $region;

  /**
   * The block weight.
   *
   * @var int
   */
  protected $weight;

  /**
   * The plugin instance ID.
   *
   * @var string
   */
  protected $plugin;

  /**
   * The visibility settings for this block.
   *
   * @var array
   */
  protected $visibility = [];

  /**
   * The plugin collection that holds the block plugin for this entity.
   *
   * @var \Drupal\block\BlockPluginCollection
   */
  protected $pluginCollection;

  /**
   * The available contexts for this block and its visibility conditions.
   *
   * @var array
   */
  protected $contexts = [];

  /**
   * The visibility collection.
   *
   * @var \Drupal\Core\Condition\ConditionPluginCollection
   */
  protected $visibilityCollection;

  /**
   * The condition plugin manager.
   *
   * @var \Drupal\Core\Executable\ExecutableManagerInterface
   */
  protected $conditionPluginManager;

  /**
   * The theme that includes the block plugin for this entity.
   *
   * @var string
   */
  protected $theme;

  /**
   * {@inheritdoc}
   */
  public function getPlugin() {
    return $this
      ->getPluginCollection()
      ->get($this->plugin);
  }

  /**
   * Encapsulates the creation of the block's LazyPluginCollection.
   *
   * @return \Drupal\Component\Plugin\LazyPluginCollection
   *   The block's plugin collection.
   */
  protected function getPluginCollection() {
    if (!$this->pluginCollection) {
      $this->pluginCollection = new BlockPluginCollection(\Drupal::service('plugin.manager.block'), $this->plugin, $this
        ->get('settings'), $this
        ->id());
    }
    return $this->pluginCollection;
  }

  /**
   * {@inheritdoc}
   */
  public function getPluginCollections() {
    return [
      'settings' => $this
        ->getPluginCollection(),
      'visibility' => $this
        ->getVisibilityConditions(),
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function getPluginId() {
    return $this->plugin;
  }

  /**
   * {@inheritdoc}
   */
  public function getRegion() {
    return $this->region;
  }

  /**
   * {@inheritdoc}
   */
  public function getTheme() {
    return $this->theme;
  }

  /**
   * {@inheritdoc}
   */
  public function getWeight() {
    return $this->weight;
  }

  /**
   * {@inheritdoc}
   */
  public function label() {
    $settings = $this
      ->get('settings');
    if ($settings['label']) {
      return $settings['label'];
    }
    else {
      $definition = $this
        ->getPlugin()
        ->getPluginDefinition();
      return $definition['admin_label'];
    }
  }

  /**
   * Sorts active blocks by weight; sorts inactive blocks by name.
   */
  public static function sort(ConfigEntityInterface $a, ConfigEntityInterface $b) {

    // Separate enabled from disabled.
    $status = (int) $b
      ->status() - (int) $a
      ->status();
    if ($status !== 0) {
      return $status;
    }

    // Sort by weight.
    $weight = $a
      ->getWeight() - $b
      ->getWeight();
    if ($weight) {
      return $weight;
    }

    // Sort by label.
    return strcmp($a
      ->label(), $b
      ->label());
  }

  /**
   * {@inheritdoc}
   */
  public function calculateDependencies() {
    parent::calculateDependencies();
    $this
      ->addDependency('theme', $this->theme);
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
    parent::postSave($storage, $update);

    // Entity::postSave() calls Entity::invalidateTagsOnSave(), which only
    // handles the regular cases. The Block entity has one special case: a
    // newly created block may *also* appear on any page in the current theme,
    // so we must invalidate the associated block's cache tag (which includes
    // the theme cache tag).
    if (!$update) {
      Cache::invalidateTags($this
        ->getCacheTagsToInvalidate());
    }
  }

  /**
   * {@inheritdoc}
   */
  public function getVisibility() {
    return $this
      ->getVisibilityConditions()
      ->getConfiguration();
  }

  /**
   * {@inheritdoc}
   */
  public function setVisibilityConfig($instance_id, array $configuration) {
    $conditions = $this
      ->getVisibilityConditions();
    if (!$conditions
      ->has($instance_id)) {
      $configuration['id'] = $instance_id;
      $conditions
        ->addInstanceId($instance_id, $configuration);
    }
    else {
      $conditions
        ->setInstanceConfiguration($instance_id, $configuration);
    }
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function getVisibilityConditions() {
    if (!isset($this->visibilityCollection)) {
      $this->visibilityCollection = new ConditionPluginCollection($this
        ->conditionPluginManager(), $this
        ->get('visibility'));
    }
    return $this->visibilityCollection;
  }

  /**
   * {@inheritdoc}
   */
  public function getVisibilityCondition($instance_id) {
    return $this
      ->getVisibilityConditions()
      ->get($instance_id);
  }

  /**
   * Gets the condition plugin manager.
   *
   * @return \Drupal\Core\Executable\ExecutableManagerInterface
   *   The condition plugin manager.
   */
  protected function conditionPluginManager() {
    if (!isset($this->conditionPluginManager)) {
      $this->conditionPluginManager = \Drupal::service('plugin.manager.condition');
    }
    return $this->conditionPluginManager;
  }

  /**
   * {@inheritdoc}
   */
  public function setRegion($region) {
    $this->region = $region;
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function setWeight($weight) {
    $this->weight = $weight;
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function createDuplicateBlock($new_id = NULL, $new_theme = NULL) {
    $duplicate = parent::createDuplicate();
    if (!empty($new_id)) {
      $duplicate->id = $new_id;
    }
    if (!empty($new_theme)) {
      $duplicate->theme = $new_theme;
    }
    return $duplicate;
  }

  /**
   * {@inheritdoc}
   */
  public function preSave(EntityStorageInterface $storage) {
    parent::preSave($storage);

    // Ensure the region is valid to mirror the behavior of block_rebuild().
    // This is done primarily for backwards compatibility support of
    // \Drupal\block\BlockInterface::BLOCK_REGION_NONE.
    $regions = system_region_list($this->theme);
    if (!isset($regions[$this->region]) && $this
      ->status()) {
      $this
        ->setRegion(system_default_region($this->theme))
        ->disable();
    }
  }

}