#pragma once

#if !defined(MIJIN_UTIL_TRAITS_HPP_INCLUDED)
#define MIJIN_UTIL_TRAITS_HPP_INCLUDED 1

#include <tuple>

namespace mijin
{

//
// public defines
//

//
// public constants
//

//
// public types
//

struct Type_; // use as typevar
struct Any_; // use as placeholder in templates

template<typename T>
struct always_false
{
    static constexpr bool value = false;
};

template<typename T>
inline constexpr bool always_false_v = always_false<T>::value;

template<auto V>
struct always_false_val
{
    static constexpr bool value = false;
};

template<auto V>
inline constexpr bool always_false_val_v = always_false_val<V>::value;

template<template<typename> typename TFilter, typename... TArgs>
struct TypeFilter;

template<template<typename> typename TFilter>
struct TypeFilter<TFilter>
{
    using type_t = std::tuple<>;
};

template<template<typename> typename TFilter, typename TFirst, typename... TArgs>
struct TypeFilter<TFilter, TFirst, TArgs...>
{
    static consteval auto makeTypeHelper()
    {
        using base_t = typename TypeFilter<TFilter, TArgs...>::type_t;

        // note: not using decltype, as the compiler might think it is being evaluated
        if constexpr (!TFilter<TFirst>::value) {
            return static_cast<base_t*>(nullptr);
        }
        else {
            auto wrapper = []<typename... TArgsInner>(std::tuple<TArgsInner...>*)
            {
                return static_cast<std::tuple<TFirst, TArgsInner...>*>(nullptr);
            };
            return wrapper(static_cast<base_t*>(nullptr));
        }
    }

    using type_t = std::remove_pointer_t<decltype(makeTypeHelper())>;
};

template<template<typename> typename TFilter, typename... TArgs>
auto typeFilterHelper(std::tuple<TArgs...>*)
{
    return static_cast<typename TypeFilter<TFilter, TArgs...>::type_t*>(nullptr);
}

template<template<typename> typename TFilter, typename TTuple>
using filter_types_t = std::remove_pointer_t<decltype(typeFilterHelper<TFilter>(static_cast<TTuple*>(nullptr)))>;

template<template<typename> typename TPredicate, typename... TArgs>
auto mapTypesHelper(std::tuple<TArgs...>)
{
    return static_cast<std::tuple<TPredicate<TArgs>...>*>(nullptr);
}

template<template<typename> typename TPredicate, typename TTuple>
using map_types_t = std::remove_pointer_t<decltype(mapTypesHelper<TPredicate>(std::declval<TTuple>()))>;

template<template<typename> typename TPredicate, template<typename> typename TTemplate>
struct map_template {
    template<typename T>
    using type_t = TTemplate<TPredicate<T>>;
};

template<template<typename...> typename TTemplate, typename TType>
struct is_template_instance : std::false_type {};

template<template<typename...> typename TTemplate, typename... TArgs>
struct is_template_instance<TTemplate, TTemplate<TArgs...>> : std::true_type {};

template<template<typename...> typename TTemplate, typename TType>
constexpr bool is_template_instance_v = is_template_instance<TTemplate, TType>::value;

namespace impl
{
template<template<typename...> typename TTemplate, typename... TArgsTTmpl>
struct tmpl_param_comparator
{
    template<typename TTmpl, typename TInstance>
    static constexpr bool compare_single = std::is_same_v<TTmpl, TInstance> or std::is_same_v<TTmpl, Any_>;

    template<typename T>
    struct matches : std::false_type {};

    // original (which MSVC didn't like for some reason :/)
    // template<typename... TArgsInstance>
    // struct matches<TTemplate<TArgsInstance...>> : std::bool_constant<(compare_single<TArgsTTmpl, TArgsInstance> && ...)> {};

    template<template<typename...> typename TOtherTemplate, typename... TArgsInstance> requires(is_template_instance_v<TTemplate, TOtherTemplate<TArgsInstance...>>)
    struct matches<TOtherTemplate<TArgsInstance...>> : std::bool_constant<(compare_single<TArgsTTmpl, TArgsInstance> && ...)> {};

    template<typename T>
    using matches_t = matches<T>;
};
}

template<typename TTemplate, typename TType>
struct match_template_type : std::false_type {};

template<template<typename...> typename TTemplate, typename TType, typename... TArgs>
struct match_template_type<TTemplate<TArgs...>, TType> : impl::tmpl_param_comparator<TTemplate, TArgs...>::template matches_t<TType> {};

template<typename TTemplate, typename TType>
constexpr bool match_template_type_v = match_template_type<TTemplate, TType>::value;

// similar to std::is_same, but allows placeholders
//   - is_type_or_impl<some_tmpl<Type_>, some_type> resolves to some_tmpl<some_type>
//   - is_type_or_impl<some_tmpl<Any_, int>, some_type> checks if some_type is an instance of some_tmpl with int as 2nd parameter
template<typename TMatch, typename TConcrete>
struct type_matches
{
    using type = std::is_same<TMatch, TConcrete>;
};

template<template<typename> typename TTmplMatch, typename TConcrete>
struct type_matches<TTmplMatch<Type_>, TConcrete>
{
    using type = TTmplMatch<TConcrete>;
};

template<template<typename...> typename TTmplMatch, typename TConcrete, typename... TArgs>
struct type_matches<TTmplMatch<TArgs...>, TConcrete>
{
    using type = match_template_type<TTmplMatch<TArgs...>, TConcrete>;
};

template<typename TMatch, typename TConcrete>
using type_matches_t = type_matches<TMatch, TConcrete>::type;

template<typename TMatch, typename TConcrete>
inline constexpr bool type_matches_v = type_matches_t<TMatch, TConcrete>::value;

template<typename TConcrete, typename... TMatches>
struct is_any_type : std::disjunction<std::is_same<TConcrete, TMatches>...> {};

template<typename TConcrete, typename... TMatches>
static constexpr bool is_any_type_v = is_any_type<TConcrete, TMatches...>::value;

template<typename TConcrete, typename... TMatches>
struct match_any_type : std::disjunction<type_matches_t<TMatches, TConcrete>...> {};

template<typename TConcrete, typename... TMatches>
static constexpr bool match_any_type_v = match_any_type<TConcrete, TMatches...>::value;

template<typename T, typename... Types>
concept union_type = match_any_type_v<T, Types...>;

template<typename TElement, typename TCollection>
struct is_type_member;

template<typename TElement, template<typename...> typename TCollection, typename... Ts>
struct is_type_member<TElement, TCollection<Ts...>>
  : std::bool_constant<(... || std::is_same<TElement, Ts>{})>
{};

template<typename TElement, typename TCollection>
constexpr bool is_type_member_v = is_type_member<TElement, TCollection>::value;

template<typename T, typename TObject>
struct is_member_object_pointer_of : std::false_type {};

template<typename TMember, typename TObject>
struct is_member_object_pointer_of<TMember (TObject::*), TObject> : std::true_type {};

template<typename T, typename TObject>
inline constexpr bool is_member_object_pointer_of_v = is_member_object_pointer_of<T, TObject>::value;

template<typename T, typename TObject>
concept member_object_pointer_of = is_member_object_pointer_of_v<T, TObject>;

template<typename TFrom, typename TTo>
using copy_const_t = std::conditional_t<std::is_const_v<TFrom>, std::add_const_t<TTo>, std::remove_const_t<TTo>>;

template<typename TFrom, typename TTo>
using copy_volatile_t = std::conditional_t<std::is_volatile_v<TFrom>, std::add_volatile_t<TTo>, std::remove_volatile_t<TTo>>;

template<typename TFrom, typename TTo>
using copy_cv_t = copy_const_t<TFrom, copy_volatile_t<TFrom, TTo>>;

template<typename TActual, typename TDelay>
using delay_type_t = TActual;


template<std::size_t I, typename TArg, typename... TArgs>
struct TypeAtHelper
{
    using type_t = typename TypeAtHelper<I-1, TArgs...>::type_t;
};

template<typename TArg, typename... TArgs>
struct TypeAtHelper<0, TArg, TArgs...>
{
    using type_t = TArg;
};
template<std::size_t I, typename... TArgs>
using type_at_t = TypeAtHelper<I, TArgs...>::type_t;

template<typename TDefault, template<typename...> typename TOper, typename... TArgs>
struct detect_or
{
    using type = TDefault;
    static constexpr bool detected = false;
};

template<typename TDefault, template<typename...> typename TOper, typename... TArgs>
    requires requires { typename TOper<TArgs...>; }
struct detect_or<TDefault, TOper, TArgs...>
{
    using type = TOper<TArgs...>;
    static constexpr bool detected = true;
};
template<typename TDefault, template<typename...> typename TOper, typename... TArgs>
using detect_or_t = detect_or<TDefault, TOper, TArgs...>::type;

struct empty_type {};

template<typename T, bool enable>
struct optional_base
{
    using type = T;
};

template<typename T>
struct optional_base<T, false>
{
    using type = empty_type;
};

template<typename T, bool enable>
using optional_base_t = optional_base<T, enable>::type;

//
// public functions
//

template<typename THelper, typename TType>
decltype(auto) delayEvaluation(TType&& value)
{
    return static_cast<TType&&>(value);
}

#define MIJIN_STATIC_TESTS 1
#if MIJIN_STATIC_TESTS
namespace test
{
template<typename T, typename U>
struct MyTemplate {};

static_assert(match_template_type_v<MyTemplate<Any_, int>, MyTemplate<int, int>>);
static_assert(match_template_type_v<MyTemplate<Any_, Any_>, MyTemplate<int, int>>);
static_assert(type_matches_v<MyTemplate<Any_, int>, MyTemplate<int, int>>);
static_assert(type_matches_v<MyTemplate<Any_, Any_>, MyTemplate<int, int>>);
static_assert(!type_matches_v<MyTemplate<double, int>, MyTemplate<int, int>>);
static_assert(type_matches_v<MyTemplate<Any_, Any_>, MyTemplate<int, double>>);
static_assert(type_matches_v<std::is_pointer<Type_>, void*>);

static_assert(union_type<int, int>);
static_assert(!union_type<int>);
static_assert(!union_type<int, double>);
static_assert(union_type<MyTemplate<int, int>, MyTemplate<int, int>>);
static_assert(union_type<MyTemplate<int, int>, MyTemplate<Any_, int>>);
static_assert(union_type<MyTemplate<int, int>, MyTemplate<Any_, Any_>>);
static_assert(union_type<MyTemplate<int, int>, MyTemplate<double, double>, MyTemplate<Any_, Any_>>);
static_assert(!union_type<int*, int>);
static_assert(union_type<int*, std::is_pointer<Type_>>);
static_assert(!union_type<int, std::is_pointer<Type_>>);
}
#endif

} // namespace mijin

#endif // !defined(MIJIN_UTIL_TRAITS_HPP_INCLUDED)