#pragma once
#include <type_traits>
#include <concepts>
#include <tuple>
#include "compat/assert.hpp"

namespace floormat::Pack {
template<std::unsigned_integral T, uint8_t N> struct Bits_;
} // namespace floormat::Pack

namespace floormat::detail_Pack {

using namespace floormat::Pack;
template<std::unsigned_integral T, size_t Sum, typename... Xs> struct check_size_overflow;

template<std::unsigned_integral T, std::unsigned_integral U, size_t Sum, uint8_t N, typename... Xs>
struct check_size_overflow<T, Sum, Bits_<U, N>, Xs...>
{
    static_assert(std::is_same_v<T, U>);
    static constexpr auto acc = Sum + size_t{N};
    using next_check = check_size_overflow<T, acc, Xs...>;
    static constexpr auto size = next_check::size;
    static constexpr bool result = next_check::result;
};

template<std::unsigned_integral T, size_t Sum>
struct check_size_overflow<T, Sum>
{
    static constexpr size_t size = Sum;
    static constexpr bool result = Sum <= sizeof(T)*8;
};

template<std::unsigned_integral T, size_t CAPACITY>
struct Storage
{
    static_assert(CAPACITY <= sizeof(T)*8);

    using Type = T;
    static constexpr size_t Capacity = CAPACITY;
    T value;

    template<size_t N>
    constexpr T get() const
    {
        static_assert(N > 0);
        static_assert(N <= sizeof(T)*8);
        static_assert(N <= Capacity);
        return T(value & (T(1) << N) - T(1));
    }

    template<size_t N>
    constexpr T advance() const
    {
        static_assert(N <= sizeof(T)*8);
        static_assert(N <= Capacity);
        return T(value >> N);
    }

    constexpr bool operator==(const Storage&) const noexcept = default;
    [[nodiscard]] constexpr inline bool check_zero() const { return value == T(0); }

    template<size_t N> using next = Storage<T, Capacity - N>;
};

template<std::unsigned_integral T>
struct Storage<T, 0>
{
    using Type = T;
    static constexpr size_t Capacity = 0;
    T value;

    template<size_t N> [[maybe_unused]] constexpr T get() const = delete;
    template<size_t N> [[maybe_unused]] constexpr T advance() const = delete;
    constexpr bool operator==(const Storage&) const noexcept = default;
    [[nodiscard]] constexpr inline bool check_zero() const { return true; }

    template<size_t N> struct next
    {
        static_assert(N == 0, "reading past the end");
        static_assert(N != 0, "reading past the end");
    };
};

template<std::unsigned_integral T, size_t N>
struct make_tuple_type_
{
    template<size_t> using index_to_type = T;
    template<typename> struct aux;
    template<size_t... Is> struct aux<std::index_sequence<Is...>>
    {
        static_assert(sizeof...(Is) > 0);
        using type = std::tuple<index_to_type<Is>...>;
    };
    using Seq = typename aux<std::make_index_sequence<N>>::type;
};
template<std::unsigned_integral T, size_t N> using make_tuple_type = typename make_tuple_type_<T, N>::Seq;

template<typename T, typename Place, size_t Left>
static void assign_to_tuple(Place&, Storage<T, Left> st, std::index_sequence<>)
{
    fm_assert(st.check_zero());
}

template<typename T, typename Place, size_t Left, size_t Size, size_t... Sizes>
static void assign_to_tuple(Place& p, Storage<T, Left> st, std::index_sequence<Size, Sizes...>)
{
    using std::get;
    get<Size>(p) = st.template get<Size>(st);
    assign_to_tuple(p, st.template advance<Size>(), std::index_sequence<Sizes...>{});
}

} // namespace floormat::detail_Pack

namespace floormat::Pack {

template<std::unsigned_integral T, uint8_t N>
struct Bits_ final
{
    static_assert(std::is_fundamental_v<T>);
    static_assert(N > 0);
    static_assert(N < sizeof(T)*8);

    using type = T;
    static constexpr auto bits = N;
};

} // namespace floormat::Pack