class CommentStatistics

class CommentStatistics implements CommentStatisticsInterface {
    
    /**
     * The current database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $database;
    
    /**
     * The replica database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $databaseReplica;
    
    /**
     * The current logged in user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The state service.
     *
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * Constructs the CommentStatistics service.
     *
     * @param \Drupal\Core\Database\Connection $database
     *   The active database connection.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current logged in user.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\State\StateInterface $state
     *   The state service.
     * @param \Drupal\Core\Database\Connection|null $database_replica
     *   (Optional) the replica database connection.
     */
    public function __construct(Connection $database, AccountInterface $current_user, EntityTypeManagerInterface $entity_type_manager, StateInterface $state, Connection $database_replica = NULL) {
        $this->database = $database;
        $this->databaseReplica = $database_replica ?: $database;
        $this->currentUser = $current_user;
        $this->entityTypeManager = $entity_type_manager;
        $this->state = $state;
    }
    
    /**
     * {@inheritdoc}
     */
    public function read($entities, $entity_type, $accurate = TRUE) {
        $connection = $accurate ? $this->database : $this->databaseReplica;
        $stats = $connection->select('comment_entity_statistics', 'ces')
            ->fields('ces')
            ->condition('ces.entity_id', array_keys($entities), 'IN')
            ->condition('ces.entity_type', $entity_type)
            ->execute();
        $statistics_records = [];
        while ($entry = $stats->fetchObject()) {
            $statistics_records[] = $entry;
        }
        return $statistics_records;
    }
    
    /**
     * {@inheritdoc}
     */
    public function delete(EntityInterface $entity) {
        $this->database
            ->delete('comment_entity_statistics')
            ->condition('entity_id', $entity->id())
            ->condition('entity_type', $entity->getEntityTypeId())
            ->execute();
    }
    
    /**
     * {@inheritdoc}
     */
    public function create(FieldableEntityInterface $entity, $fields) {
        $query = $this->database
            ->insert('comment_entity_statistics')
            ->fields([
            'entity_id',
            'entity_type',
            'field_name',
            'cid',
            'last_comment_timestamp',
            'last_comment_name',
            'last_comment_uid',
            'comment_count',
        ]);
        foreach ($fields as $field_name => $detail) {
            // Skip fields that entity does not have.
            if (!$entity->hasField($field_name)) {
                continue;
            }
            // Get the user ID from the entity if it's set, or default to the
            // currently logged in user.
            $last_comment_uid = 0;
            if ($entity instanceof EntityOwnerInterface) {
                $last_comment_uid = $entity->getOwnerId();
            }
            if (!isset($last_comment_uid)) {
                // Default to current user when entity does not implement
                // EntityOwnerInterface or author is not set.
                $last_comment_uid = $this->currentUser
                    ->id();
            }
            // Default to REQUEST_TIME when entity does not have a changed property.
            $last_comment_timestamp = REQUEST_TIME;
            // @todo Make comment statistics language aware and add some tests. See
            //   https://www.drupal.org/node/2318875
            if ($entity instanceof EntityChangedInterface) {
                $last_comment_timestamp = $entity->getChangedTimeAcrossTranslations();
            }
            $query->values([
                'entity_id' => $entity->id(),
                'entity_type' => $entity->getEntityTypeId(),
                'field_name' => $field_name,
                'cid' => 0,
                'last_comment_timestamp' => $last_comment_timestamp,
                'last_comment_name' => NULL,
                'last_comment_uid' => $last_comment_uid,
                'comment_count' => 0,
            ]);
        }
        $query->execute();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getMaximumCount($entity_type) {
        return $this->database
            ->query('SELECT MAX([comment_count]) FROM {comment_entity_statistics} WHERE [entity_type] = :entity_type', [
            ':entity_type' => $entity_type,
        ])
            ->fetchField();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getRankingInfo() {
        return [
            'comments' => [
                'title' => t('Number of comments'),
                'join' => [
                    'type' => 'LEFT',
                    'table' => 'comment_entity_statistics',
                    'alias' => 'ces',
                    // Default to comment field as this is the most common use case for
                    // nodes.
'on' => "ces.entity_id = i.sid AND ces.entity_type = 'node' AND ces.field_name = 'comment'",
                ],
                // Inverse law that maps the highest view count on the site to 1 and 0
                // to 0. Note that the ROUND here is necessary for PostgreSQL and SQLite
                // in order to ensure that the :comment_scale argument is treated as
                // a numeric type, because the PostgreSQL PDO driver sometimes puts
                // values in as strings instead of numbers in complex expressions like
                // this.
'score' => '2.0 - 2.0 / (1.0 + ces.comment_count * (ROUND(:comment_scale, 4)))',
                'arguments' => [
                    ':comment_scale' => \Drupal::state()->get('comment.node_comment_statistics_scale', 0),
                ],
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function update(CommentInterface $comment) {
        // Allow bulk updates and inserts to temporarily disable the maintenance of
        // the {comment_entity_statistics} table.
        if (!$this->state
            ->get('comment.maintain_entity_statistics')) {
            return;
        }
        $query = $this->database
            ->select('comment_field_data', 'c');
        $query->addExpression('COUNT([cid])');
        $count = $query->condition('c.entity_id', $comment->getCommentedEntityId())
            ->condition('c.entity_type', $comment->getCommentedEntityTypeId())
            ->condition('c.field_name', $comment->getFieldName())
            ->condition('c.status', CommentInterface::PUBLISHED)
            ->condition('default_langcode', 1)
            ->execute()
            ->fetchField();
        if ($count > 0) {
            // Comments exist.
            $last_reply = $this->database
                ->select('comment_field_data', 'c')
                ->fields('c', [
                'cid',
                'name',
                'changed',
                'uid',
            ])
                ->condition('c.entity_id', $comment->getCommentedEntityId())
                ->condition('c.entity_type', $comment->getCommentedEntityTypeId())
                ->condition('c.field_name', $comment->getFieldName())
                ->condition('c.status', CommentInterface::PUBLISHED)
                ->condition('default_langcode', 1)
                ->orderBy('c.created', 'DESC')
                ->range(0, 1)
                ->execute()
                ->fetchObject();
            // Use merge here because entity could be created before comment field.
            $this->database
                ->merge('comment_entity_statistics')
                ->fields([
                'cid' => $last_reply->cid,
                'comment_count' => $count,
                'last_comment_timestamp' => $last_reply->changed,
                'last_comment_name' => $last_reply->uid ? '' : $last_reply->name,
                'last_comment_uid' => $last_reply->uid,
            ])
                ->keys([
                'entity_id' => $comment->getCommentedEntityId(),
                'entity_type' => $comment->getCommentedEntityTypeId(),
                'field_name' => $comment->getFieldName(),
            ])
                ->execute();
        }
        else {
            // Comments do not exist.
            $entity = $comment->getCommentedEntity();
            // Get the user ID from the entity if it's set, or default to the
            // currently logged in user.
            if ($entity instanceof EntityOwnerInterface) {
                $last_comment_uid = $entity->getOwnerId();
            }
            if (!isset($last_comment_uid)) {
                // Default to current user when entity does not implement
                // EntityOwnerInterface or author is not set.
                $last_comment_uid = $this->currentUser
                    ->id();
            }
            $this->database
                ->update('comment_entity_statistics')
                ->fields([
                'cid' => 0,
                'comment_count' => 0,
                // Use the changed date of the entity if it's set, or default to
                // REQUEST_TIME.
'last_comment_timestamp' => $entity instanceof EntityChangedInterface ? $entity->getChangedTimeAcrossTranslations() : REQUEST_TIME,
                'last_comment_name' => '',
                'last_comment_uid' => $last_comment_uid,
            ])
                ->condition('entity_id', $comment->getCommentedEntityId())
                ->condition('entity_type', $comment->getCommentedEntityTypeId())
                ->condition('field_name', $comment->getFieldName())
                ->execute();
        }
        // Reset the cache of the commented entity so that when the entity is loaded
        // the next time, the statistics will be loaded again.
        $this->entityTypeManager
            ->getStorage($comment->getCommentedEntityTypeId())
            ->resetCache([
            $comment->getCommentedEntityId(),
        ]);
    }

}