bp_messages_remove_user_to_group_message_thread( $group_id,  $user_id )

function bp_messages_remove_user_to_group_message_thread( $group_id, $user_id ) {

	global $wpdb, $bp, $messages_template;

	if ( true === bp_disable_group_messages() && bp_is_active( 'messages' ) ) {

		$group_thread = (int) groups_get_groupmeta( (int) $group_id, 'group_message_thread' );
		$recipients   = BP_Messages_Thread::get_recipients_for_thread( (int) $group_thread );
		$recipients   = wp_list_pluck( $recipients, 'user_id' );

		if ( $group_thread > 0 && in_array( (int) $user_id, $recipients, true ) ) {

			$first_message     = BP_Messages_Thread::get_first_message( $group_thread );
			$message_users_ids = bp_messages_get_meta( $first_message->id, 'message_users_ids', true ); // users list
			$message_users_ids = explode( ',', $message_users_ids );
			if ( ( $key = array_search( $user_id, $message_users_ids ) ) !== false ) {
				unset( $message_users_ids[ $key ] );
			}

			bp_messages_update_meta( $first_message->id, 'message_users_ids', implode( ',', $message_users_ids ) );

			remove_action( 'messages_message_sent', 'messages_notification_new_message', 10 );
			remove_action( 'messages_message_sent', 'bp_messages_message_sent_add_notification', 10 );
			$new_reply = messages_new_message( array(
				'sender_id'  => $user_id,
				'thread_id'  => $group_thread,
				'subject'    => '',
				'content'    => '<p> </p>',
				'date_sent'  => $date_sent = bp_core_current_time(),
				'error_type' => 'wp_error',
			) );
			add_action( 'messages_message_sent', 'messages_notification_new_message', 10 );
			add_action( 'messages_message_sent', 'bp_messages_message_sent_add_notification', 10 );
			if ( ! is_wp_error( $new_reply ) && true === is_int( ( int ) $new_reply ) ) {
				if ( bp_has_message_threads( array( 'include' => $new_reply ) ) ) {
					while ( bp_message_threads() ) {
						bp_message_thread();
						$last_message_id = (int) $messages_template->thread->last_message_id;
						bp_messages_update_meta( $last_message_id, 'group_message_group_left', 'yes' );
						bp_messages_update_meta( $last_message_id, 'group_id', (int) $group_id );
					}
				}
			}
			$wpdb->query( $wpdb->prepare( "DELETE FROM {$bp->messages->table_name_recipients} WHERE user_id = %d AND thread_id = %d", $user_id, (int) $group_thread ) );
		}
	}
}