class CommentStorage

class CommentStorage extends SqlContentEntityStorage implements CommentStorageInterface {
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * Constructs a CommentStorage object.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_info
     *   An array of entity info for the entity type.
     * @param \Drupal\Core\Database\Connection $database
     *   The database connection to be used.
     * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
     *   The entity field manager.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache
     *   Cache backend instance to use.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     * @param \Drupal\Core\Cache\MemoryCache\MemoryCacheInterface $memory_cache
     *   The memory cache.
     * @param \Drupal\Core\Entity\EntityTypeBundleInfoInterface $entity_type_bundle_info
     *   The entity type bundle info.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(EntityTypeInterface $entity_info, Connection $database, EntityFieldManagerInterface $entity_field_manager, AccountInterface $current_user, CacheBackendInterface $cache, LanguageManagerInterface $language_manager, MemoryCacheInterface $memory_cache, EntityTypeBundleInfoInterface $entity_type_bundle_info = NULL, EntityTypeManagerInterface $entity_type_manager = NULL) {
        parent::__construct($entity_info, $database, $entity_field_manager, $cache, $language_manager, $memory_cache, $entity_type_bundle_info, $entity_type_manager);
        $this->currentUser = $current_user;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_info) {
        return new static($entity_info, $container->get('database'), $container->get('entity_field.manager'), $container->get('current_user'), $container->get('cache.entity'), $container->get('language_manager'), $container->get('entity.memory_cache'), $container->get('entity_type.bundle.info'), $container->get('entity_type.manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getMaxThread(CommentInterface $comment) {
        $query = $this->database
            ->select($this->getDataTable(), 'c')
            ->condition('entity_id', $comment->getCommentedEntityId())
            ->condition('field_name', $comment->getFieldName())
            ->condition('entity_type', $comment->getCommentedEntityTypeId())
            ->condition('default_langcode', 1);
        $query->addExpression('MAX(thread)', 'thread');
        return $query->execute()
            ->fetchField();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getMaxThreadPerThread(CommentInterface $comment) {
        $query = $this->database
            ->select($this->getDataTable(), 'c')
            ->condition('entity_id', $comment->getCommentedEntityId())
            ->condition('field_name', $comment->getFieldName())
            ->condition('entity_type', $comment->getCommentedEntityTypeId())
            ->condition('thread', $comment->getParentComment()
            ->getThread() . '.%', 'LIKE')
            ->condition('default_langcode', 1);
        $query->addExpression('MAX(thread)', 'thread');
        return $query->execute()
            ->fetchField();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDisplayOrdinal(CommentInterface $comment, $comment_mode, $divisor = 1) {
        // Count how many comments (c1) are before $comment (c2) in display order.
        // This is the 0-based display ordinal.
        $data_table = $this->getDataTable();
        $query = $this->database
            ->select($data_table, 'c1');
        $query->innerJoin($data_table, 'c2', 'c2.entity_id = c1.entity_id AND c2.entity_type = c1.entity_type AND c2.field_name = c1.field_name');
        $query->addExpression('COUNT(*)', 'count');
        $query->condition('c2.cid', $comment->id());
        if (!$this->currentUser
            ->hasPermission('administer comments')) {
            $query->condition('c1.status', CommentInterface::PUBLISHED);
        }
        if ($comment_mode == CommentManagerInterface::COMMENT_MODE_FLAT) {
            // For rendering flat comments, cid is used for ordering comments due to
            // unpredictable behavior with timestamp, so we make the same assumption
            // here.
            $query->condition('c1.cid', $comment->id(), '<');
        }
        else {
            // For threaded comments, the c.thread column is used for ordering. We can
            // use the sorting code for comparison, but must remove the trailing
            // slash.
            $query->where('SUBSTRING(c1.thread, 1, (LENGTH(c1.thread) - 1)) < SUBSTRING(c2.thread, 1, (LENGTH(c2.thread) - 1))');
        }
        $query->condition('c1.default_langcode', 1);
        $query->condition('c2.default_langcode', 1);
        $ordinal = $query->execute()
            ->fetchField();
        return $divisor > 1 ? floor($ordinal / $divisor) : $ordinal;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getNewCommentPageNumber($total_comments, $new_comments, FieldableEntityInterface $entity, $field_name) {
        $field = $entity->getFieldDefinition($field_name);
        $comments_per_page = $field->getSetting('per_page');
        $data_table = $this->getDataTable();
        if ($total_comments <= $comments_per_page) {
            // Only one page of comments.
            $count = 0;
        }
        elseif ($field->getSetting('default_mode') == CommentManagerInterface::COMMENT_MODE_FLAT) {
            // Flat comments.
            $count = $total_comments - $new_comments;
        }
        else {
            // Threaded comments.
            // 1. Find all the threads with a new comment.
            $unread_threads_query = $this->database
                ->select($data_table, 'comment')
                ->fields('comment', [
                'thread',
            ])
                ->condition('entity_id', $entity->id())
                ->condition('entity_type', $entity->getEntityTypeId())
                ->condition('field_name', $field_name)
                ->condition('status', CommentInterface::PUBLISHED)
                ->condition('default_langcode', 1)
                ->orderBy('created', 'DESC')
                ->orderBy('cid', 'DESC')
                ->range(0, $new_comments);
            // 2. Find the first thread.
            $first_thread_query = $this->database
                ->select($unread_threads_query, 'thread');
            $first_thread_query->addExpression('SUBSTRING(thread, 1, (LENGTH(thread) - 1))', 'torder');
            $first_thread = $first_thread_query->fields('thread', [
                'thread',
            ])
                ->orderBy('torder')
                ->range(0, 1)
                ->execute()
                ->fetchField();
            // Remove the final '/'.
            $first_thread = substr($first_thread, 0, -1);
            // Find the number of the first comment of the first unread thread.
            $count = $this->database
                ->query('SELECT COUNT(*) FROM {' . $data_table . '} WHERE entity_id = :entity_id
                        AND entity_type = :entity_type
                        AND field_name = :field_name
                        AND status = :status
                        AND SUBSTRING(thread, 1, (LENGTH(thread) - 1)) < :thread
                        AND default_langcode = 1', [
                ':status' => CommentInterface::PUBLISHED,
                ':entity_id' => $entity->id(),
                ':field_name' => $field_name,
                ':entity_type' => $entity->getEntityTypeId(),
                ':thread' => $first_thread,
            ])
                ->fetchField();
        }
        return $comments_per_page > 0 ? (int) ($count / $comments_per_page) : 0;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getChildCids(array $comments) {
        return $this->database
            ->select($this->getDataTable(), 'c')
            ->fields('c', [
            'cid',
        ])
            ->condition('pid', array_keys($comments), 'IN')
            ->condition('default_langcode', 1)
            ->execute()
            ->fetchCol();
    }
    
    /**
     * {@inheritdoc}
     *
     * To display threaded comments in the correct order we keep a 'thread' field
     * and order by that value. This field keeps this data in
     * a way which is easy to update and convenient to use.
     *
     * A "thread" value starts at "1". If we add a child (A) to this comment,
     * we assign it a "thread" = "1.1". A child of (A) will have "1.1.1". Next
     * brother of (A) will get "1.2". Next brother of the parent of (A) will get
     * "2" and so on.
     *
     * First of all note that the thread field stores the depth of the comment:
     * depth 0 will be "X", depth 1 "X.X", depth 2 "X.X.X", etc.
     *
     * Now to get the ordering right, consider this example:
     *
     * 1
     * 1.1
     * 1.1.1
     * 1.2
     * 2
     *
     * If we "ORDER BY thread ASC" we get the above result, and this is the
     * natural order sorted by time. However, if we "ORDER BY thread DESC"
     * we get:
     *
     * 2
     * 1.2
     * 1.1.1
     * 1.1
     * 1
     *
     * Clearly, this is not a natural way to see a thread, and users will get
     * confused. The natural order to show a thread by time desc would be:
     *
     * 2
     * 1
     * 1.2
     * 1.1
     * 1.1.1
     *
     * which is what we already did before the standard pager patch. To achieve
     * this we simply add a "/" at the end of each "thread" value. This way, the
     * thread fields will look like this:
     *
     * 1/
     * 1.1/
     * 1.1.1/
     * 1.2/
     * 2/
     *
     * we add "/" since this char is, in ASCII, higher than every number, so if
     * now we "ORDER BY thread DESC" we get the correct order. However this would
     * spoil the reverse ordering, "ORDER BY thread ASC" -- here, we do not need
     * to consider the trailing "/" so we use a substring only.
     */
    public function loadThread(EntityInterface $entity, $field_name, $mode, $comments_per_page = 0, $pager_id = 0) {
        $data_table = $this->getDataTable();
        $query = $this->database
            ->select($data_table, 'c');
        $query->addField('c', 'cid');
        $query->condition('c.entity_id', $entity->id())
            ->condition('c.entity_type', $entity->getEntityTypeId())
            ->condition('c.field_name', $field_name)
            ->condition('c.default_langcode', 1)
            ->addTag('entity_access')
            ->addTag('comment_filter')
            ->addMetaData('base_table', 'comment')
            ->addMetaData('entity', $entity)
            ->addMetaData('field_name', $field_name);
        if ($comments_per_page) {
            $query = $query->extend('Drupal\\Core\\Database\\Query\\PagerSelectExtender')
                ->limit($comments_per_page);
            if ($pager_id) {
                $query->element($pager_id);
            }
            $count_query = $this->database
                ->select($data_table, 'c');
            $count_query->addExpression('COUNT(*)');
            $count_query->condition('c.entity_id', $entity->id())
                ->condition('c.entity_type', $entity->getEntityTypeId())
                ->condition('c.field_name', $field_name)
                ->condition('c.default_langcode', 1)
                ->addTag('entity_access')
                ->addTag('comment_filter')
                ->addMetaData('base_table', 'comment')
                ->addMetaData('entity', $entity)
                ->addMetaData('field_name', $field_name);
            $query->setCountQuery($count_query);
        }
        if (!$this->currentUser
            ->hasPermission('administer comments')) {
            $query->condition('c.status', CommentInterface::PUBLISHED);
            if ($comments_per_page) {
                $count_query->condition('c.status', CommentInterface::PUBLISHED);
            }
        }
        if ($mode == CommentManagerInterface::COMMENT_MODE_FLAT) {
            $query->orderBy('c.cid', 'ASC');
        }
        else {
            // See comment above. Analysis reveals that this doesn't cost too
            // much. It scales much much better than having the whole comment
            // structure.
            $query->addExpression('SUBSTRING(c.thread, 1, (LENGTH(c.thread) - 1))', 'torder');
            $query->orderBy('torder', 'ASC');
        }
        $cids = $query->execute()
            ->fetchCol();
        $comments = [];
        if ($cids) {
            $comments = $this->loadMultiple($cids);
        }
        return $comments;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getUnapprovedCount() {
        return $this->database
            ->select($this->getDataTable(), 'c')
            ->condition('status', CommentInterface::NOT_PUBLISHED, '=')
            ->condition('default_langcode', 1)
            ->countQuery()
            ->execute()
            ->fetchField();
    }

}