#ifndef CK_FUNCTIONAL3_HPP
#define CK_FUNCTIONAL3_HPP

#include "composable_kernel/utility/functional.hpp"
#include "composable_kernel/utility/functional2.hpp"
#include "composable_kernel/utility/Sequence.hpp"
#include "composable_kernel/utility/Array.hpp"

namespace ck {

// RemainLengths: Sequence<...>
template <class RemainLengths>
struct static_ford_impl
{
    // F signature: F(Sequence<...> multi_id)
    // CurrentMultiIndex: Sequence<...>
    template <class F, class CurrentMultiIndex>
    __host__ __device__ constexpr void operator()(F f, CurrentMultiIndex) const
    {
        static_assert(RemainLengths::GetSize() > 0, "wrong! should not get here");

        static_for<0, RemainLengths::Front(), 1>{}([=](auto I) {
            static_ford_impl<decltype(RemainLengths::PopFront())>{}(f,
                                                                    CurrentMultiIndex::PushBack(I));
        });
    }
};

template <>
struct static_ford_impl<Sequence<>>
{
    // F signature: F(Sequence<...> multi_id)
    // CurrentMultiIndex: Sequence<...>
    template <class F, class CurrentMultiIndex>
    __host__ __device__ constexpr void operator()(F f, CurrentMultiIndex) const
    {
        f(CurrentMultiIndex{});
    }
};

// Lengths is Sequence<...>
template <class Lengths>
struct static_ford
{
    // F signature: F(Sequence<...> multi_id)
    template <class F>
    __host__ __device__ constexpr void operator()(F f) const
    {
        static_assert(Lengths::GetSize() > 0, "wrong! Lengths is empty");

        static_ford_impl<Lengths>{}(f, Sequence<>{});
    }
};

template <index_t RemainDim>
struct ford_impl
{
    // F signature: F(Array<...> multi_id)
    // CurrentMultiIndex: Array<...>
    // RemainLengths: Sequence<...>
    template <class F, class CurrentMultiIndex, class RemainLengths>
    __host__ __device__ constexpr void
    operator()(F f, CurrentMultiIndex current_multi_id, RemainLengths) const
    {
        static_assert(RemainLengths::GetSize() == RemainDim, "wrong!");
        static_assert(RemainDim > 1, "wrong!");

        constexpr auto next_length = RemainLengths{}.Front();

        for(index_t i = 0; i < next_length; ++i)
        {
            ford_impl<RemainDim - 1>{}(f, current_multi_id.PushBack(i), RemainLengths{}.PopFront());
        }
    }
};

template <>
struct ford_impl<1>
{
    // F signature: F(Array<...> multi_id)
    // CurrentMultiIndex: Array<...>
    // RemainLengths: Sequence<...>
    template <class F, class CurrentMultiIndex, class RemainLengths>
    __host__ __device__ constexpr void
    operator()(F f, CurrentMultiIndex current_multi_id, RemainLengths) const
    {
        static_assert(RemainLengths::GetSize() == 1, "wrong!");

        constexpr index_t last_length = RemainLengths{}.Front();

        for(index_t i = 0; i < last_length; ++i)
        {
            f(current_multi_id.PushBack(i));
        }
    }
};

// Lengths is Sequence<...>
template <class Lengths>
struct ford
{
    // F signature: F(Array<...> multi_id)
    template <class F>
    __host__ __device__ constexpr void operator()(F f) const
    {
        constexpr index_t first_length = Lengths{}.Front();

        for(index_t i = 0; i < first_length; ++i)
        {
            ford_impl<Lengths::GetSize() - 1>{}(f, Array<index_t, 1>{i}, Lengths{}.PopFront());
        }
    }
};

} // namespace ck
#endif