reflect/any.hpp

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#ifndef NEFORCE_CORE_REFLECT_ANY_HPP__
#define NEFORCE_CORE_REFLECT_ANY_HPP__

 
#include "NeForce/core/memory/unique_ptr.hpp"
#include "NeForce/core/string/string_view.hpp"
NEFORCE_BEGIN_NAMESPACE__
NEFORCE_BEGIN_REFLECT__

 
using type_id = size_t; 
 

template <typename T>
struct type_name {
    static constexpr string_view value = "unknown";
};

template <typename T>
NEFORCE_INLINE17 constexpr string_view type_name_v = type_name<T>::value;

#define __NEFORCE_SPECIALIZE_TYPE_NAME(T)        \
    template <>                                  \
    struct type_name<T> {                        \
        static constexpr string_view value = #T; \
    };
 
NEFORCE_MACRO_RANGE_ARITHMETIC(__NEFORCE_SPECIALIZE_TYPE_NAME)
#undef __NEFORCE_SPECIALIZE_TYPE_NAME

class meta_any {
private:
    struct concepts {
        virtual ~concepts() = default;
        virtual unique_ptr<concepts> clone() const = 0;
        virtual reflect::type_id type_id() const noexcept = 0;
    };
 
    template <typename T>
    struct model final : concepts {
        T value_;
 
        explicit model(T value) :
        value_(_NEFORCE move(value)) {}
 
        unique_ptr<concepts> clone() const override { return _NEFORCE make_unique<model<T>>(value_); }
 
        reflect::type_id type_id() const noexcept override { return type_name_v<T>.to_hash(); }
    };
 
    unique_ptr<concepts> storage_{nullptr}; 
 
public:
    meta_any() noexcept = default;

    template <typename T, typename = enable_if_t<!is_same_v<decay_t<T>, meta_any>>>
    explicit meta_any(T&& value) :
    storage_(_NEFORCE make_unique<model<decay_t<T>>>(_NEFORCE forward<T>(value))) {}
 
    meta_any(meta_any&&) noexcept = default;
    meta_any& operator=(meta_any&&) noexcept = default;

    meta_any(const meta_any& other) {
        if (other.storage_) {
            storage_ = other.storage_->clone();
        }
    }

    meta_any& operator=(const meta_any& other) {
        if (addressof(other) == this) {
            return *this;
        }
 
        if (other.storage_) {
            storage_ = other.storage_->clone();
        } else {
            storage_.reset();
        }
 
        return *this;
    }

    NEFORCE_NODISCARD reflect::type_id type_id() const noexcept { return storage_ ? storage_->type_id() : 0; }

    NEFORCE_NODISCARD bool has_value() const noexcept { return !!storage_; }

    explicit operator bool() const noexcept { return has_value(); }

    template <typename T>
    NEFORCE_NODISCARD T* cast() noexcept {
        if (!storage_) {
            return nullptr;
        }
        if (storage_->type_id() != type_name_v<T>.to_hash()) {
            return nullptr;
        }
        auto* md = dynamic_cast<model<T>*>(storage_.get());
        return md ? &md->value_ : nullptr;
    }

    template <typename T>
    NEFORCE_NODISCARD const T* cast() const noexcept {
        if (!storage_) {
            return nullptr;
        }
        if (storage_->type_id() != type_name_v<T>.to_hash()) {
            return nullptr;
        }
        auto* md = dynamic_cast<model<T>*>(storage_.get());
        return md ? &md->value_ : nullptr;
    }

    template <typename T>
    NEFORCE_NODISCARD T& get() {
        if (auto* ptr = cast<T>()) {
            return *ptr;
        }
        NEFORCE_THROW_EXCEPTION(typecast_exception("Not a valid type"));
        unreachable();
    }

    template <typename T>
    NEFORCE_NODISCARD const T& get() const {
        if (auto* ptr = cast<T>()) {
            return *ptr;
        }
        NEFORCE_THROW_EXCEPTION(typecast_exception("Not a valid type"));
        unreachable();
    }

    template <typename T>
    NEFORCE_NODISCARD bool can_cast() const noexcept {
        return cast<T>() != nullptr;
    }

    template <typename T>
    NEFORCE_NODISCARD T convert() const {
        if (auto* ptr = cast<T>()) {
            return *ptr;
        }
        NEFORCE_THROW_EXCEPTION(typecast_exception("Not a valid type"));
        unreachable();
    }
};
 // Reflection
 
NEFORCE_END_REFLECT__
NEFORCE_END_NAMESPACE__
#endif // NEFORCE_CORE_REFLECT_ANY_HPP__