ADC/common/adc_value_holder.h

#pragma once

/*

    ABSTRACT DEVICE COMPONENTS LIBRARY

*/


#include <any>
#include <concepts>
#include <functional>
#include <map>
#include <ranges>
#include <system_error>
#include <typeindex>

#include "adc_traits.h"

namespace adc
{

// error codes
enum class AdcValueHolderErrorCode : int {
    ERROR_OK,
    ERROR_NO_CONV_FUNC,
    ERROR_INTERNAL_TYPE_MISMATCH,
    ERROR_VALUE_IS_NOT_VALID
};

}  // namespace adc


namespace std
{

template <>
class is_error_code_enum<adc::AdcValueHolderErrorCode> : public true_type
{
};

}  // namespace std


namespace adc
{



// error category
struct AdcValueHolderErrorCategory : public std::error_category {
    AdcValueHolderErrorCategory() : std::error_category() {}

    const char* name() const noexcept { return "DEVA_DEVICE_ATTRIBUTE"; }

    std::string message(int ec) const
    {
        AdcValueHolderErrorCode err = static_cast<AdcValueHolderErrorCode>(ec);

        switch (err) {
            case AdcValueHolderErrorCode::ERROR_OK:
                return "OK";
            case AdcValueHolderErrorCode::ERROR_NO_CONV_FUNC:
                return "conversion function is not defined";
            case AdcValueHolderErrorCode::ERROR_INTERNAL_TYPE_MISMATCH:
                return "try to setup default conversion function for invalid type (internal type mismatch)";
            case AdcValueHolderErrorCode::ERROR_VALUE_IS_NOT_VALID:
                return "user value is not valid";
            default:
                return "UNKNOWN";
        }
    }

    static const AdcValueHolderErrorCategory& get()
    {
        static const AdcValueHolderErrorCategory constInst;
        return constInst;
    }
};


inline std::error_code make_error_code(AdcValueHolderErrorCode ec)
{
    return std::error_code(static_cast<int>(ec), AdcValueHolderErrorCategory::get());
}



/*

                            GENERAL-PURPOSE VALUE HOLDER CLASS WITH OPTIONAL VALIDATOR

*/


class AdcValueHolder
{
protected:
    template <typename T>
    using arg_t = typename traits::adc_func_traits<T>::ret_t;

    std::function<void(std::any&)> _getterWrapper;
    std::function<void(const std::any&)> _setterWrapper;

    std::map<std::type_index, std::function<void(std::any&)>> _convertToInternal;
    std::map<std::type_index, std::function<void(std::any&)>> _convertFromInternal;

    std::type_index _internalTypeIndex;

    void init(std::invocable<> auto&& getter,
              std::invocable<const arg_t<decltype(getter)>&> auto&& setter,
              std::predicate<const arg_t<decltype(getter)>&> auto&& validator)
    {
        using value_t = arg_t<decltype(getter)>;

        static_assert(std::is_same_v<value_t, void>, "THE getter MUST NOT RETURN void TYPE!!!");

        using g_t = decltype(getter);
        _getterWrapper = [wrapper = traits::adc_pf_wrapper(std::forward<g_t>(getter))](std::any& val) {
            auto& getter = std::get<0>(wrapper);
            val = getter();
        };


        using vld_t = decltype(validator);
        using s_t = decltype(setter);

        if constexpr (std::is_same_v<vld_t, decltype(AdcValueHolderDummyValidator)>) {  // no validation
            _setterWrapper = [wrapper = traits::adc_pf_wrapper(std::forward<s_t>(setter)), this](const std::any& val) {
                auto& setter = std::get<0>(wrapper);

                setter(std::any_cast<value_t>(val));
            };
        } else {
            _setterWrapper = [wrapper =
                                  traits::adc_pf_wrapper(std::forward<s_t>(setter), std::forward<vld_t>(validator)),
                              this](const std::any& val) {
                auto& setter = std::get<0>(wrapper);
                auto& validator = std::get<1>(wrapper);

                auto v = std::any_cast<value_t>(val);

                if (validator(v)) {
                    setter(v);
                } else {
                    throw std::system_error(AdcValueHolderErrorCode::ERROR_VALUE_IS_NOT_VALID);
                }
            };
        }


        // By default no conversion will be made if user value of internal type is given.
        // But such a conversion may be defined explicitly by calling addConvertFunc method
        _convertFromInternal[_internalTypeIndex] = [](auto) {};
        _convertToInternal[_internalTypeIndex] = [](auto) {};
    }

public:
    // default trivial types (just arithmetic ones)
    constexpr static std::tuple<char, short, int, long, long long, float, double> _defaultTrivialConvTypes{};

    // always-true validator
    constexpr static auto AdcValueHolderDummyValidator = [](const auto&) { return true; };

    /*  CONSTRUCTORS AND DESTRUCTOR  */

    AdcValueHolder(
        std::invocable<> auto&& getter,
        std::invocable<const arg_t<decltype(getter)>&> auto&& setter,
        std::predicate<const arg_t<decltype(getter)>&> auto&& validator = AdcValueHolder::AdcValueHolderDummyValidator)
        : _internalTypeIndex(std::type_index(typeid(arg_t<decltype(getter)>)))
    {
        init(std::forward<decltype(getter)>(getter), std::forward<decltype(setter)>(setter),
             std::forward<decltype(validator)>(validator));
    }


    template <typename... Ts>
    AdcValueHolder(
        std::invocable<> auto&& getter,
        std::invocable<const arg_t<decltype(getter)>&> auto&& setter,
        const std::tuple<Ts...>& trivialConvTypes,
        std::predicate<const arg_t<decltype(getter)>&> auto&& validator = AdcValueHolder::AdcValueHolderDummyValidator)
        : AdcValueHolder(std::forward<decltype(getter)>(getter),
                         std::forward<decltype(setter)>(setter),
                         std::forward<decltype(validator)>(validator))
    {
        // setup trivially-defined conversion function
        AdcValueHolder::setupTrivialConvertFunc<arg_t<decltype(getter)>, std::tuple<Ts...>>(this);
    }


    AdcValueHolder(const AdcValueHolder&) = default;
    AdcValueHolder(AdcValueHolder&&) = default;

    virtual ~AdcValueHolder() = default;


    /*  PUBLIC METHODS  */


    std::type_index valueTypeIndex() const { return _internalTypeIndex; }


    std::vector<std::type_index> convTypeIndices()
    {
        auto kv = std::views::keys(_convertFromInternal);
        return {kv.begin(), kv.end()};
    }


    AdcValueHolder& resetValueHolder(
        std::invocable<> auto&& getter,
        std::invocable<const arg_t<decltype(getter)>&> auto&& setter,
        std::predicate<const arg_t<decltype(getter)>&> auto&& validator = AdcValueHolderDummyValidator)
    {
        _convertFromInternal.clear();
        _convertToInternal.clear();

        init(std::forward<decltype(getter)>(getter), std::forward<decltype(setter)>(setter),
             std::forward<decltype(validator)>(validator));

        return *this;
    }


    template <typename... Ts>
    AdcValueHolder& resetValueHolder(
        std::invocable<> auto&& getter,
        std::invocable<const arg_t<decltype(getter)>&> auto&& setter,
        const std::tuple<Ts...>& trivialConvTypes,
        std::predicate<const arg_t<decltype(getter)>&> auto&& validator = AdcValueHolderDummyValidator)
    {
        resetValueHolder(std::forward<decltype(getter)>(getter), std::forward<decltype(setter)>(setter),
                         std::forward<decltype(validator)>(validator));

        // setup trivially-defined conversion function
        AdcValueHolder::setupTrivialConvertFunc<arg_t<decltype(getter)>, std::tuple<Ts...>>(this);

        return *this;
    }


    template <typename UT>
    AdcValueHolder& addConvertFunc(std::invocable<std::any&> auto&& func_to_internal,
                                   std::invocable<std::any&> auto&& func_from_internal)
    {
        static_assert(std::is_same_v<UT, void>, "void IS NOT VALID TYPE!!!");

        auto t_index = std::type_index(typeid(UT));

        _convertToInternal[t_index] = std::forward<decltype(func_to_internal)>(func_to_internal);
        _convertFromInternal[t_index] = std::forward<decltype(func_from_internal)>(func_from_internal);

        return *this;
    }


    template <typename UT = void>
    AdcValueHolder& delConvertFunc()
    {
        if constexpr (std::is_same_v<UT, void>) {  // delete all conversion functions
            _convertFromInternal.clear();
            _convertToInternal.clear();

            // restore conversion functions for internal type
            _convertFromInternal[_internalTypeIndex] = [](auto) {};
            _convertToInternal[_internalTypeIndex] = [](auto) {};
        } else {
            auto t_index = std::type_index(typeid(UT));

            _convertFromInternal.erase(t_index);
            _convertToInternal.erase(t_index);
        }

        return *this;
    }


    template <typename UT>
    operator UT()
    {
        std::any val;

        auto t_index = std::type_index(typeid(UT));
        auto it = _convertFromInternal.find(t_index);

        if (it == _convertFromInternal.end()) {
            throw std::system_error(AdcValueHolderErrorCode::ERROR_NO_CONV_FUNC);
        }

        _getterWrapper(val);
        it->second(val);  // call conversion function

        return std::any_cast<UT>(val);
    }

    template <typename UT>
    AdcValueHolder& operator=(const UT& value)
    {
        std::any val = std::make_any<UT>(value);

        auto t_index = std::type_index(typeid(UT));
        auto it = _convertToInternal.find(t_index);

        if (it == _convertToInternal.end()) {
            throw std::system_error(AdcValueHolderErrorCode::ERROR_NO_CONV_FUNC);
        }

        it->second(val);  // call conversion function

        _setterWrapper(val);

        return *this;
    }


    AdcValueHolder& operator=(AdcValueHolder&& other) = default;
    AdcValueHolder& operator=(const AdcValueHolder& other) = default;


protected:
    /*  STATIC HELPER METHODS   */

    template <typename VT, size_t I, typename TupleT>
    static void setupTrivialConvertFuncImpl(AdcValueHolder* holder)
    {
        if constexpr (I < std::tuple_size_v<TupleT>) {
            using elem_t = std::tuple_element_t<I, TupleT>;

            if constexpr (!std::is_same_v<VT, elem_t>) {
                auto t_index = std::type_index(typeid(elem_t));

                holder->_convertToInternal[t_index] = [](std::any& val) {
                    val = std::make_any<VT>(std::any_cast<elem_t>(val));
                };

                holder->_convertFromInternal[t_index] = [](std::any& val) {
                    val = std::make_any<elem_t>(std::any_cast<VT>(val));
                };
            }

            AdcValueHolder::setupTrivialConvertFuncImpl<VT, I + 1, TupleT>(holder);
        }
    }

    template <typename VT, typename TupleT>
    static void setupTrivialConvertFunc(AdcValueHolder* holder)
    {
        setupTrivialConvertFuncImpl<VT, 0, TupleT>(holder);
    }
};



}  // namespace adc