guid.hpp

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#pragma once

#include <array>
#include <cstdint>
#include <format>
#include <sstream>
#include <string>

#include "Mountain/core.hpp"


namespace Mountain
{
    class MOUNTAIN_API Guid final
    {
        static constexpr size_t Data4Size = 8;

    public:
        constexpr Guid() = default;

        static constexpr Guid Empty() { return Guid(); }

        static Guid New();

        static Guid FromString(const char_t* str);

        [[nodiscard]]
        uint32_t GetData1() const;

        [[nodiscard]]
        uint16_t GetData2() const;

        [[nodiscard]]
        uint16_t GetData3() const;

        [[nodiscard]]
        const std::array<uint8_t, Data4Size>& GetData4() const;

        [[nodiscard]]
        bool_t operator==(const Guid& other) const;

        [[nodiscard]]
        bool_t operator!=(const Guid& other) const;

        explicit operator std::string() const;

    private:
        uint32_t m_Data1 = 0;
        uint16_t m_Data2 = 0;
        uint16_t m_Data3 = 0;
        std::array<uint8_t, Data4Size> m_Data4 = {};

        friend struct std::hash<Guid>;
    };
}

template <>
struct std::hash<Mountain::Guid>
{
    static constexpr size_t RandomValue = 0x9E3779B9;
    
    size_t operator()(const Mountain::Guid& guid) const noexcept
    {
        size_t result = 0;
        result ^= std::hash<decltype(guid.m_Data1)>()(guid.m_Data1) + RandomValue;
        result ^= std::hash<decltype(guid.m_Data2)>()(guid.m_Data2) + RandomValue + (result << 6) + (result >> 2);
        result ^= std::hash<decltype(guid.m_Data3)>()(guid.m_Data3) + RandomValue + (result << 6) + (result >> 2);

        for (size_t i = 0; i < Mountain::Guid::Data4Size; i++)
        {
            result ^= std::hash<std::remove_cvref_t<decltype(guid.m_Data4[i])>>()(guid.m_Data4[i]) + RandomValue + (result << 6) + (result >> 2);
        }

        return result;
    }
};

template <>
struct std::formatter<Mountain::Guid>
{
    template <class ParseContext>
    constexpr typename ParseContext::iterator parse(ParseContext& ctx)
    {
        auto it = ctx.begin();
        if (it == ctx.end())
            return it;
 
        if (*it != '}')
            throw std::format_error("Invalid format args for Mountain::Guid");
 
        return it;
    }

    // ReSharper disable once CppMemberFunctionMayBeStatic
    template <class FormatContext>
    typename FormatContext::iterator format(const Mountain::Guid& guid, FormatContext& ctx) const
    {
        std::ostringstream out;

        out << static_cast<std::string>(guid);
        
        return std::ranges::copy(std::move(out).str(), ctx.out()).out;
    }
};