geode/loader/include/Geode/modify/Traits.hpp

#pragma once
#include <Geode/meta/common.hpp>
#include <type_traits>

namespace geode::modifier {
    template <class FunctionType>
    struct MemberFunc {
        template <class Class>
        using with = FunctionType Class::*;
    };

    template <class FunctionType>
    struct ConstMemberFunc {
        template <class Class>
        using with = FunctionType Class::*;
    };

    // why
    template <class Return, class... Parameters>
    struct ConstMemberFunc<Return(Parameters...)> {
        using FunctionType = Return(Parameters...) const;
        template <class Class>
        using with = FunctionType Class::*;
    };

    template <class FunctionType>
    struct StaticFunc {
        using type = FunctionType*;
    };

    using ::geode::core::meta::always_false;

    /**
     * The ~unevaluated~ function that gets the appropriate
     * version of a function type from its return, parameters, and classes.
     *
     * nvm its no more unevaluated
     */
    template <class FunctionType, class Class>
    constexpr auto substitute(typename MemberFunc<FunctionType>::template with<Class> function) {
        return function;
    }

    template <class FunctionType, class Class>
    constexpr auto substitute(typename ConstMemberFunc<FunctionType>::template with<Class> function
    ) {
        return function;
    }

    template <class FunctionType>
    constexpr auto substitute(typename StaticFunc<FunctionType>::type function) {
        return function;
    }

    /**
     * An UUID system that generates an unique comparable
     * value for every instance. Internally used for comparing member
     * function pointers.
     */
    template <auto a>
    struct function_uuid {
    private:
        constexpr static void function() {}

    public:
        constexpr static inline void (*value)() = &function_uuid::function;
    };
}