DepthGuide/src/core/object_manager.h

#ifndef DEPTHGUIDE_OBJECT_MANAGER_H
#define DEPTHGUIDE_OBJECT_MANAGER_H

#include "core/utility.hpp"

#include <boost/asio/post.hpp>
#include <boost/asio/io_context.hpp>
#include <boost/signals2.hpp>

#include <cassert>
#include <cstdint>
#include <functional>
#include <memory>
#include <optional>
#include <typeindex>
#include <typeinfo>

class object_manager {
public:

    using name_type = uint16_t;
    using io_context = boost::asio::io_context;

    struct create_config {
        io_context *ctx = nullptr;
    };

    explicit object_manager(create_config conf);

    ~object_manager();

    // thread-safe
    template<typename T>
    void save(name_type obj_name, T &&val) {
        using RT = std::remove_cvref_t<T>;
        if (auto ctx = switch_ctx(); ctx != nullptr) [[unlikely]] {
            using boost::asio::post;
            static_assert(std::is_copy_constructible_v<RT>);
            post(*ctx, [=, rt_val = RT(val), this] { save(obj_name, rt_val); });
            return;
        }

        auto pl_ptr = query_placeholder(obj_name, typeid(RT));
        if (pl_ptr == nullptr) [[unlikely]] {
            static_assert(std::is_default_constructible_v<RT>);
            create_placeholder(obj_name, typeid(RT),
                               new RT{}, [](void *ptr) { delete (RT *) ptr; });
            pl_ptr = query_placeholder(obj_name, typeid(RT));
        }
        assert(pl_ptr != nullptr);

        static_assert(std::is_copy_assignable_v<RT>);
        *(RT *) pl_ptr = val;
        notify_signal(obj_name);
    }

    template<typename T>
    T query(name_type obj_name) {
        auto pl_ptr = query_placeholder(obj_name, typeid(T));
        assert(pl_ptr != nullptr);

        static_assert(std::is_copy_constructible_v<T>);
        return *(T *) pl_ptr;
    }

    std::type_index query_type(name_type obj_name) {
        auto info_o = query_info(obj_name);
        assert(info_o.has_value());
        return info_o->type;
    }

    timestamp_type query_save_ts(name_type obj_name) {
        auto info_o = query_info(obj_name);
        assert(info_o.has_value());
        return info_o->last_save_ts;
    }

    using obj_sig_type = boost::signals2::signal<void(name_type)>;

    obj_sig_type *query_signal(name_type obj_name) {
        auto info_o = query_info(obj_name);
        assert(info_o.has_value());
        return info_o->sig;
    }

    struct obj_stats {
        float save_interval = 0.0f; // in ms
        float save_frequency = 0.0f; // in Hz
    };

    obj_stats query_obj_stats(name_type obj_name);

private:

    using del_func_type = void (*)(void *);

    struct obj_info {
        std::type_index type = typeid(void);
        void *pl_ptr = nullptr;
        obj_sig_type *sig = nullptr;
        timestamp_type last_save_ts = 0;
    };

    std::optional<obj_info> query_info(name_type obj_name);

    void *query_placeholder(name_type obj_name, std::type_index obj_type) {
        auto info_o = query_info(obj_name);
        if (!info_o.has_value()) [[unlikely]] return nullptr;
        if (info_o->type != obj_type) return nullptr;
        return info_o->pl_ptr;
    }

    void create_placeholder(name_type obj_name, std::type_index obj_type,
                            void *ptr, del_func_type del_func);

    void notify_signal(name_type obj_name);

    // return target context or nullptr
    io_context *switch_ctx();

    struct impl;
    std::unique_ptr<impl> pimpl;
};

using obj_name_type = object_manager::name_type;

static constexpr obj_name_type invalid_obj_name = -1;

extern object_manager *main_ob;

#define OBJ_QUERY(type, name) \
    main_ob->query<type>(name)

#define OBJ_TYPE(name) \
    main_ob->query_type(name)

#define OBJ_SAVE_TS(name) \
    main_ob->query_save_ts(name)

#define OBJ_STATS(name) \
    main_ob->query_obj_stats(name)

#define OBJ_SAVE(name, val) \
    main_ob->save(name, val)

#define OBJ_SIG(name) \
    main_ob->query_signal(name)

#endif //DEPTHGUIDE_OBJECT_MANAGER_H