id.hpp

/*
    KTech, Kaup's C++ 2D terminal game engine library.
    Copyright (C) 2023-2025 Ethan Kaufman (AKA Kaup)
 
    This file is part of KTech.
 
    KTech is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    any later version.
 
    KTech is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
    along with KTech. If not, see <https://www.gnu.org/licenses/>.
*/
 
#pragma once
 
#define KTECH_DEFINITION
#include "../ktech.hpp"
#undef KTECH_DEFINITION
 
#include <cstddef>
 
template<typename T>
struct KTech::ID
{
    explicit constexpr ID()
        : m_uuid(0) {};
 
    constexpr auto operator==(ID id) const -> bool
    {
        return id.m_uuid == m_uuid;
    }
 
private:
    mutable size_t m_i = 0; // Local cached index
    uint64_t m_uuid; // Universally unique identifier
 
    explicit constexpr ID(uint64_t uuid)
        : m_uuid(uuid) {}
 
    // Generate a unique `ID`; can only be used by world structures.
    static auto Unique() -> ID
    {
        static uint64_t uuid = 0;
        uuid++;
        return ID(uuid);
    }
 
    friend T; // Allow only world structures to call `Unique()`.
    friend class CachingRegistry<T>;
};