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    //
    // Copyright(c) 2018 Gabi Melman.
    // Distributed under the MIT License (http://opensource.org/licenses/MIT)
    //
    
    #pragma once
    
    //
    // Async logging using global thread pool
    // All loggers created here share same global thread pool.
    // Each log message is pushed to a queue along withe a shared pointer to the
    // logger.
    // If a logger deleted while having pending messages in the queue, it's actual
    // destruction will defer
    // until all its messages are processed by the thread pool.
    // This is because each message in the queue holds a shared_ptr to the
    // originating logger.
    
    #include "spdlog/async_logger.h"
    #include "spdlog/details/registry.h"
    #include "spdlog/details/thread_pool.h"
    
    #include <memory>
    #include <mutex>
    
    namespace spdlog {
    
    namespace details {
    static const size_t default_async_q_size = 8192;
    }
    
    // async logger factory - creates async loggers backed with thread pool.
    // if a global thread pool doesn't already exist, create it with default queue
    // size of 8192 items and single thread.
    template<async_overflow_policy OverflowPolicy = async_overflow_policy::block>
    struct async_factory_impl
    {
        template<typename Sink, typename... SinkArgs>
        static std::shared_ptr<async_logger> create(const std::string &logger_name, SinkArgs &&... args)
        {
            auto &registry_inst = details::registry::instance();
    
            // create global thread pool if not already exists..
            std::lock_guard<std::recursive_mutex>(registry_inst.tp_mutex());
            auto tp = registry_inst.get_tp();
            if (tp == nullptr)
            {
                tp = std::make_shared<details::thread_pool>(details::default_async_q_size, 1);
                registry_inst.set_tp(tp);
            }
    
            auto sink = std::make_shared<Sink>(std::forward<SinkArgs>(args)...);
            auto new_logger = std::make_shared<async_logger>(logger_name, std::move(sink), std::move(tp), OverflowPolicy);
            registry_inst.register_and_init(new_logger);
            return new_logger;
        }
    };
    
    using async_factory = async_factory_impl<async_overflow_policy::block>;
    using async_factory_nonblock = async_factory_impl<async_overflow_policy::overrun_oldest>;
    
    template<typename Sink, typename... SinkArgs>
    inline std::shared_ptr<spdlog::logger> create_async(const std::string &logger_name, SinkArgs &&... sink_args)
    {
        return async_factory::create<Sink>(logger_name, std::forward<SinkArgs>(sink_args)...);
    }
    
    template<typename Sink, typename... SinkArgs>
    inline std::shared_ptr<spdlog::logger> create_async_nb(const std::string &logger_name, SinkArgs &&... sink_args)
    {
        return async_factory_nonblock::create<Sink>(logger_name, std::forward<SinkArgs>(sink_args)...);
    }
    
    // set global thread pool.
    inline void init_thread_pool(size_t q_size, size_t thread_count)
    {
        auto tp = std::make_shared<details::thread_pool>(q_size, thread_count);
        details::registry::instance().set_tp(std::move(tp));
    }
    
    // get the global thread pool.
    inline std::shared_ptr<spdlog::details::thread_pool> thread_pool()
    {
        return details::registry::instance().get_tp();
    }
    } // namespace spdlog