geode/loader/include/Geode/hook-core/Hook.hpp

#pragma once

#include "../utils/Result.hpp"
#include "Handler.hpp"

#include <vector>

namespace geode::core {

    // The handle returned from adding a hook. It is used to remove a hook.
    struct HookHandle {
        void* handler;
        void* address;
        void* detour;
        void* trampoline;
    };

    namespace impl {
        // a type alias for convenience and for clear type differentiation inside the source file
        using VectorPointer = std::vector<void*>*;

        GEODE_DLL void addHook(
            void* address, void* detour, VectorPointer* detourVectorAddress, void* generatedHandler,
            void** originalTrampolineAddress, void* generatedTrampoline
        );

        GEODE_DLL void removeHook(HookHandle const& handle);
    }

    namespace hook {
        template <auto Detour, template <class, class...> class Conv, class Ret, class... Args>
        Result<HookHandle> add(Ret (*address)(Args...)) {
            static std::vector<decltype(Detour)>* detourVector;
            static decltype(Detour) originalTrampoline;

            void* generatedHandler = (void*)handler<Conv, detourVector, Ret, Args...>;
            void* generatedTrampoline = (void*)trampoline<Conv, originalTrampoline, Ret, Args...>;

            impl::addHook(
                (void*)address, (void*)Detour, (impl::VectorPointer*)&detourVector,
                (void*)generatedHandler, (void**)&originalTrampoline, (void*)generatedTrampoline
            );

            return Ok<HookHandle>({ (void*)generatedHandler, (void*)address, (void*)Detour,
                                    (void*)generatedTrampoline });
        }

        inline Result<> remove(HookHandle const& handle) {
            impl::removeHook(handle);
            return Ok();
        }
    }
}