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 // SPDX-License-Identifier: MIT
 // Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
  
 #pragma once
  
 #include "ck/utility/integral_constant.hpp"
 #include "ck/utility/sequence.hpp"
 #include "ck/utility/type.hpp"
 #include "ck/utility/enable_if.hpp"
  
 namespace ck {
  
 namespace detail {
  
 template <index_t>
 struct TupleElementKey
 {
     __host__ __device__ constexpr TupleElementKey() = default;
 };
  
 template <typename Key, typename Data>
 struct TupleElementKeyData
 {
     using DataType = Data;
  
 #if 0 // workaround compiler complaint about implicitly-deleted default constructor
     __host__ __device__ constexpr TupleElementKeyData() = default;
 #else
     __host__ __device__ constexpr TupleElementKeyData() : mData{} {}
 #endif
  
     template <typename T,
               typename enable_if<!is_same<remove_cvref_t<T>, TupleElementKeyData>::value,
                                  bool>::type = false>
     __host__ __device__ constexpr TupleElementKeyData(T&& v) : mData(ck::forward<T>(v))
     {
     }
  
     DataType mData;
 };
  
 // for read access of tuple element
 template <typename Key, typename Data>
 __host__ __device__ constexpr const Data&
 get_tuple_element_data_reference(const TupleElementKeyData<Key, Data>& x)
 {
     return static_cast<const Data&>(x.mData);
 }
  
 // for write access of tuple element
 template <typename Key, typename Data>
 __host__ __device__ constexpr Data&
 get_tuple_element_data_reference(TupleElementKeyData<Key, Data>& x)
 {
     return x.mData;
 }
  
 // TODO: not sure the use of reference is correct
 template <typename Key, typename Data>
 __host__ __device__ constexpr Data&&
 get_tuple_element_data_reference(TupleElementKeyData<Key, Data>&& x)
 {
     return static_cast<Data&&>(x.mData);
 }
  
 // for infering type of tuple element
 template <typename Key, typename Data>
 __host__ __device__ constexpr Data get_tuple_element_data(const TupleElementKeyData<Key, Data>& x)
 {
     return ck::forward(x.mData);
 }
  
 template <typename Indices, typename... Xs>
 struct TupleImpl;
  
 template <index_t... Is, typename... Xs>
 struct TupleImpl<Sequence<Is...>, Xs...> : TupleElementKeyData<TupleElementKey<Is>, Xs>...
 {
     __host__ __device__ constexpr TupleImpl() = default;
  
     template <typename Y,
               typename enable_if<sizeof...(Is) == 1 && sizeof...(Xs) == 1 &&
                                      !is_same<remove_cvref_t<Y>, TupleImpl>::value,
                                  bool>::type = false>
     __host__ __device__ constexpr TupleImpl(Y&& y)
         : TupleElementKeyData<TupleElementKey<Is>, Xs>(ck::forward<Y>(y))...
     {
     }
  
     template <typename... Ys, typename enable_if<sizeof...(Ys) >= 2, bool>::type = false>
     __host__ __device__ constexpr TupleImpl(Ys&&... ys)
         : TupleElementKeyData<TupleElementKey<Is>, Xs>(ck::forward<Ys>(ys))...
     {
         static_assert(sizeof...(Is) == sizeof...(Xs) && sizeof...(Is) == sizeof...(Ys),
                       "wrong! inconsistent size");
     }
  
     __host__ __device__ static constexpr index_t Size() { return sizeof...(Xs); }
  
     template <index_t I>
     __host__ __device__ constexpr const auto& GetElementDataByKey(TupleElementKey<I>) const
     {
         return get_tuple_element_data_reference<TupleElementKey<I>>(*this);
     }
  
     template <index_t I>
     __host__ __device__ constexpr auto& GetElementDataByKey(TupleElementKey<I>)
     {
         return get_tuple_element_data_reference<TupleElementKey<I>>(*this);
     }
 };
  
 } // namespace detail
  
 template <typename... Xs>
 struct Tuple : detail::TupleImpl<typename arithmetic_sequence_gen<0, sizeof...(Xs), 1>::type, Xs...>
 {
     using base =
         detail::TupleImpl<typename arithmetic_sequence_gen<0, sizeof...(Xs), 1>::type, Xs...>;
  
     __host__ __device__ constexpr Tuple() = default;
  
     template <typename Y,
               typename enable_if<sizeof...(Xs) == 1 && !is_same<remove_cvref_t<Y>, Tuple>::value,
                                  bool>::type = false>
     __host__ __device__ constexpr Tuple(Y&& y) : base(ck::forward<Y>(y))
     {
     }
  
     template <typename... Ys,
               typename enable_if<sizeof...(Ys) == sizeof...(Xs) && sizeof...(Ys) >= 2, bool>::type =
                   false>
     __host__ __device__ constexpr Tuple(Ys&&... ys) : base(ck::forward<Ys>(ys)...)
     {
     }
  
     __host__ __device__ static constexpr index_t Size() { return sizeof...(Xs); }
  
     // read access
     template <index_t I>
     __host__ __device__ constexpr const auto& At(Number<I>) const
     {
         static_assert(I < base::Size(), "wrong! out of range");
         return base::GetElementDataByKey(detail::TupleElementKey<I>{});
     }
  
     // write access
     template <index_t I>
     __host__ __device__ constexpr auto& At(Number<I>)
     {
         static_assert(I < base::Size(), "wrong! out of range");
         return base::GetElementDataByKey(detail::TupleElementKey<I>{});
     }
  
     // read access
     template <index_t I>
     __host__ __device__ constexpr const auto& operator[](Number<I> i) const
     {
         return At(i);
     }
  
     // write access
     template <index_t I>
     __host__ __device__ constexpr auto& operator()(Number<I> i)
     {
         return At(i);
     }
  
     template <typename T>
     __host__ __device__ constexpr auto operator=(const T& a)
     {
         static_assert(T::Size() == Size(), "wrong! size not the same");
  
         static_for<0, Size(), 1>{}([&](auto i) { operator()(i) = a[i]; });
  
         return *this;
     }
  
     __host__ __device__ static constexpr bool IsStaticBuffer() { return true; }
  
     __host__ __device__ static constexpr bool IsTuple() { return true; }
 };
  
 template <>
 struct Tuple<>
 {
     __host__ __device__ constexpr Tuple() = default;
  
     __host__ __device__ static constexpr index_t Size() { return 0; }
  
     template <typename T>
     __host__ __device__ constexpr auto operator=(const T&)
     {
         return *this;
     }
  
     __host__ __device__ static constexpr bool IsStaticBuffer() { return true; }
 };
  
 template <index_t I, typename TTuple>
 struct tuple_element
 {
     // type should keep the cv/ref qualifier of original tuple element
     using type = decltype(detail::get_tuple_element_data<detail::TupleElementKey<I>>(TTuple{}));
 };
  
 template <index_t I, typename TTuple>
 using tuple_element_t = typename tuple_element<I, TTuple>::type;
  
 template <typename... Xs>
 __host__ __device__ constexpr auto make_tuple(Xs&&... xs)
 {
     return Tuple<remove_cvref_t<Xs>...>(ck::forward<Xs>(xs)...);
 }
  
 // https://en.cppreference.com/w/cpp/utility/tuple/tie
 template <typename... Args>
 constexpr Tuple<Args&...> tie(Args&... args) noexcept
 {
     return {args...};
 }
  
 } // namespace ck