EditBufferCache.php

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<?php

namespace Drupal\paragraphs_editor\EditBuffer;

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\KeyValueStore\KeyValueExpirableFactoryInterface;
use Drupal\Core\Session\AccountInterface;

/**
 * Stores edit buffers in a persistent cache.
 */
class EditBufferCache implements EditBufferCacheInterface {

  /**
   * The back end storage mechanism for storing edit buffers.
   *
   * @var \Drupal\Core\KeyValueStore\KeyValueStoreExpirableInterface
   */
  protected $storage;

  /**
   * The expiration time to set on cached buffers.
   *
   * @var int
   */
  protected $expiry;

  /**
   * The current user.
   *
   * @var \Drupal\Core\Session\AccountInterface
   */
  protected $user;

  /**
   * A list of buffer ids to be deleted from cache.
   *
   * @var array
   */
  protected $deleteQueue = [];

  /**
   * Creates an edit buffer cache object.
   *
   * @param \Drupal\Core\KeyValueStore\KeyValueExpirableFactoryInterface $keyvalue_factory
   *   The key value factory service for creating a persistent cache.
   * @param int $expiry
   *   The amount of time to allow buffers to live without being automatically
   *   destroyed.
   * @param \Drupal\Core\Session\AccountInterface $user
   *   The current user.
   */
  public function __construct(KeyValueExpirableFactoryInterface $keyvalue_factory, $expiry, AccountInterface $user) {
    $this->storage = $keyvalue_factory->get('paragraphs_editor.edit_buffer');
    $this->expiry = $expiry;
    $this->user = $user;
  }

  /**
   * {@inheritdoc}
   */
  public function get($context_string) {

    // If there is an existing buffer that doesn't have the correct context or
    // the buffer was created by a different user, we don't allow the caller to
    // access it.
    $buffer = $this->storage->get($context_string);
    if ($buffer) {
      if ($buffer->getContextString() != $context_string || $buffer->getUser() != $this->user->id()) {
        $buffer = NULL;
      }
    }

    // If we couldn't find a "good" buffer, we create a new one.
    if (!$buffer) {
      $buffer = new EditBuffer($context_string, $this->user->id());
    }

    // Tell the buffer about the cache so it can perform CRUD operations.
    $buffer->setCache($this);

    return $buffer;
  }

  /**
   * {@inheritdoc}
   */
  public function delete($context_string) {
    $buffer = $this->get($context_string);
    foreach ($buffer->getChildBufferTags() as $child_cache_key) {
      $this->delete($child_cache_key);
    }
    $this->storage->delete($context_string);
  }

  /**
   * {@inheritdoc}
   */
  public function save(EditBufferInterface $buffer) {
    $this->storage->setWithExpire($buffer->getContextString(), $buffer, $this->expiry);

    $parent_cache_key = $buffer->getParentBufferTag();
    if ($parent_cache_key) {
      $parent_buffer = $this->get($parent_cache_key);
      $parent_buffer->addChildBufferTag($buffer->getContextString());
      $this->save($parent_buffer);
    }
  }

  /**
   * {@inheritdoc}
   */
  public function processDeletionQueue(EntityInterface $entity) {
    $key = $this->deletionQueueKey($entity);
    if (!empty($this->deleteQueue[$key])) {
      foreach ($this->deleteQueue[$key] as $id) {
        $this->delete($id);
      }
    }
  }

  /**
   * {@inheritdoc}
   */
  public function queueDeletion(EntityInterface $entity, EditBufferInterface $buffer) {
    $this->deleteQueue[$this->deletionQueueKey($entity)][] = $buffer->getContextString();
  }

  /**
   * Helper function for generating a queue tag for an entity.
   *
   * @param \Drupal\Core\Entity\EntityInterface $entity
   *   The entity to create the tg for.
   *
   * @return string
   *   The created tag.
   */
  protected function deletionQueueKey(EntityInterface $entity) {
    return $entity->getEntityTypeId() . ':' . $entity->uuid();
  }

}