protected function addCommand($pluginId, $cmdTxt, ChatCommandInterface $command)
    {
        if (isset($this->commands[$cmdTxt])) {
            throw new CommandExistException(
                "$pluginId tries to register command '$cmdTxt' already registered"
            );
        }

        $this->commands[$cmdTxt] = $command;
        $this->commandPlugin[$pluginId][$cmdTxt] = $command;
    }