Jan 26, 2023

class BCT_API logger
{
public:
    class writer final
    {
    public:
        DELETE_COPY_MOVE(writer);

        inline writer(const logger& log) NOEXCEPT
          : log_(log)
        {
        }

        inline ~writer() NOEXCEPT
        {
            BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
            log_.notify(error::success, stream_.str());
            BC_POP_WARNING()
        }

        template <typename Type>
        inline std::ostream& operator<<(const Type& message) NOEXCEPT
        {
            BC_PUSH_WARNING(NO_THROW_IN_NOEXCEPT)
            stream_ << message;
            BC_POP_WARNING()

            return stream_;
        }

    private:
        const logger& log_;
        std::ostringstream stream_{};
    };

    typedef std::function<void(const code&, const std::string&)> handler;

    logger() NOEXCEPT;

    writer write() const NOEXCEPT;
    void subscribe(handler&& handler) NOEXCEPT;

    /// Stop the subscriber/pool with a final message posted to subscribers.
    void stop(const std::string& message) NOEXCEPT;
    void stop(const code& ec, const std::string& message) NOEXCEPT;

protected:
    void notify(const code& ec, std::string&& message) const NOEXCEPT;

private:
    threadpool pool_;
    asio::strand strand_;
    subscriber<const code&, const std::string&> subscriber_;

    void do_subscribe(const handler& handler) NOEXCEPT;
    void do_notify(const code& ec, const std::string& message) const NOEXCEPT;
    void do_stop(const code& ec, const std::string& message) NOEXCEPT;
};