BP_REST_Topics_Actions_Endpoint::merge_item( WP_REST_Request $request )

	public function merge_item( $request ) {

		// Define local variable(s).
		$source_topic_id      = 0;
		$destination_topic_id = 0;
		$source_topic         = 0;
		$destination_topic    = 0;
		$subscribers          = array();
		$favoriters           = array();
		$replies              = array();

		// Topic id.
		if ( empty( $request['id'] ) ) {
			return new WP_Error(
				'bp_rest_topic_invalid_id',
				__( 'Invalid topic ID.', 'buddyboss' ),
				array(
					'status' => 404,
				)
			);
		} else {
			$source_topic_id = (int) $request['id'];
		}

		// Source topic not found.
		$source_topic = bbp_get_topic( $source_topic_id );
		if ( empty( $source_topic ) ) {
			return new WP_Error(
				'bp_rest_bbp_merge_topic_source_not_found',
				__( 'The topic you want to merge was not found.', 'buddyboss' ),
				array(
					'status' => 404,
				)
			);
		}

		// Cannot edit source topic.
		if ( ! current_user_can( 'edit_topic', $source_topic->ID ) ) {
			return new WP_Error(
				'bp_rest_bbp_merge_topic_source_permission',
				__( 'Sorry, You do not have permission to edit the source topic.', 'buddyboss' ),
				array(
					'status' => rest_authorization_required_code(),
				)
			);
		}

		/** Destination Topic */
		// Topic id.
		if ( empty( $request['destination_id'] ) ) {
			return new WP_Error(
				'bp_rest_bbp_merge_topic_destination_id',
				__( 'Sorry, Destination discussion ID not found.', 'buddyboss' ),
				array(
					'status' => 404,
				)
			);
		} else {
			$destination_topic_id = (int) $request['destination_id'];
		}

		// Destination topic not found.
		$destination_topic = bbp_get_topic( $destination_topic_id );
		if ( empty( $destination_topic ) ) {
			return new WP_Error(
				'bp_rest_bbp_merge_topic_destination_not_found',
				__( 'Sorry, The discussion you want to merge to was not found.', 'buddyboss' ),
				array(
					'status' => 404,
				)
			);
		}

		// Cannot edit destination topic.
		if ( ! current_user_can( 'edit_topic', $destination_topic->ID ) ) {
			return new WP_Error(
				'bp_rest_bbp_merge_topic_destination_permission',
				__( 'Sorry, You do not have the permissions to edit the destination discussion.', 'buddyboss' ),
				array(
					'status' => rest_authorization_required_code(),
				)
			);
		}

		/** No Errors */
		// Update counts, etc...
		do_action( 'bbp_merge_topic', $destination_topic->ID, $source_topic->ID );

		/** Date Check */
		// Check if the destination topic is older than the source topic.
		if ( strtotime( $source_topic->post_date ) < strtotime( $destination_topic->post_date ) ) {

			// Set destination topic post_date to 1 second before source topic.
			$destination_post_date = gmdate( 'Y-m-d H:i:s', strtotime( $source_topic->post_date ) - 1 );

			// Update destination topic.
			wp_update_post(
				array(
					'ID'            => $destination_topic_id,
					'post_date'     => $destination_post_date,
					'post_date_gmt' => get_gmt_from_date( $destination_post_date ),
				)
			);
		}

		/** Subscriptions */
		// Get subscribers from source topic.
		$subscribers = bbp_get_topic_subscribers( $source_topic->ID );

		// Remove the topic from everybody's subscriptions.
		if ( ! empty( $subscribers ) ) {

			// Loop through each user.
			foreach ( (array) $subscribers as $subscriber ) {

				// Shift the subscriber if told to.
				if ( ! empty( $request['subscribers'] ) && ( true === $request['subscribers'] ) && bbp_is_subscriptions_active() ) {
					bbp_add_user_subscription( $subscriber, $destination_topic->ID );
				}

				// Remove old subscription.
				bbp_remove_user_subscription( $subscriber, $source_topic->ID );
			}
		}

		/** Favorites */
		// Get favoriters from source topic.
		$favoriters = bbp_get_topic_favoriters( $source_topic->ID );

		// Remove the topic from everybody's favorites.
		if ( ! empty( $favoriters ) ) {

			// Loop through each user.
			foreach ( (array) $favoriters as $favoriter ) {

				// Shift the favoriter if told to.
				if ( ! empty( $request['favorites'] ) && true === $request['favorites'] ) {
					bbp_add_user_favorite( $favoriter, $destination_topic->ID );
				}

				// Remove old favorite.
				bbp_remove_user_favorite( $favoriter, $source_topic->ID );
			}
		}

		/** Tags */
		// Get the source topic tags.
		$source_topic_tags = wp_get_post_terms( $source_topic->ID, bbp_get_topic_tag_tax_id(), array( 'fields' => 'names' ) );

		// Tags to possibly merge.
		if ( ! empty( $source_topic_tags ) && ! is_wp_error( $source_topic_tags ) ) {

			// Shift the tags if told to.
			if ( ! empty( $request['tags'] ) && ( true === $request['tags'] ) ) {
				wp_set_post_terms( $destination_topic->ID, $source_topic_tags, bbp_get_topic_tag_tax_id(), true );
			}

			// Delete the tags from the source topic.
			wp_delete_object_term_relationships( $source_topic->ID, bbp_get_topic_tag_tax_id() );
		}

		/** Source Topic */
		// Status.
		bbp_open_topic( $source_topic->ID );

		// Sticky.
		bbp_unstick_topic( $source_topic->ID );

		// Get the replies of the source topic.
		$replies = (array) get_posts(
			array(
				'post_parent'    => $source_topic->ID,
				'post_type'      => bbp_get_reply_post_type(),
				'posts_per_page' => - 1,
				'order'          => 'ASC',
			)
		);

		// Prepend the source topic to its replies array for processing.
		array_unshift( $replies, $source_topic );

		if ( ! empty( $replies ) ) {

			/** Merge Replies */
			// Change the post_parent of each reply to the destination topic id.
			foreach ( $replies as $reply ) {

				// Update the reply.
				wp_update_post(
					array(
						'ID'          => $reply->ID,
						'post_title'  => sprintf(
							/* translators: Topic Title. */
							__( 'Reply To: %s', 'buddyboss' ),
							$destination_topic->post_title
						),
						'post_name'   => false,
						'post_type'   => bbp_get_reply_post_type(),
						'post_parent' => $destination_topic->ID,
						'guid'        => '',
					)
				);

				// Adjust reply meta values.
				bbp_update_reply_topic_id( $reply->ID, $destination_topic->ID );
				bbp_update_reply_forum_id( $reply->ID, bbp_get_topic_forum_id( $destination_topic->ID ) );

				// Adjust reply to values.
				$reply_to = bbp_get_reply_to( $reply->ID );
				if ( empty( $reply_to ) ) {
					bbp_update_reply_to( $reply->ID, $source_topic->ID );
				}

				// Do additional actions per merged reply.
				do_action( 'bbp_merged_topic_reply', $reply->ID, $destination_topic->ID );
			}
		}

		/** Successful Merge */
		// Update topic's last meta data.
		bbp_update_topic_last_reply_id( $destination_topic->ID );
		bbp_update_topic_last_active_id( $destination_topic->ID );
		bbp_update_topic_last_active_time( $destination_topic->ID );

		// Send the post parent of the source topic as it has been shifted.
		// (possibly to a new forum) so we need to update the counts of the.
		// old forum as well as the new one.
		do_action( 'bbp_merged_topic', $destination_topic->ID, $source_topic->ID, $source_topic->post_parent );

		/**
		 * Fires after a list of topic is merged via the REST API.
		 *
		 * @param array           $destination_topic Destination topic.
		 * @param array           $source_topic      Source topic.
		 * @param WP_REST_Request $request           The request sent to the API.
		 *
		 * @since 0.1.0
		 */
		do_action( 'bp_rest_topic_get_item', $destination_topic, $source_topic, $request );

		return $this->get_item(
			array(
				'id'      => $destination_topic->ID,
				'context' => 'view',
			)
		);
	}