#pragma once


/*  MOUNT CONTROL COMPONENTS LIBRARY  */

/*  FINITE-STATE MACHINE IMPLEMENTATION  */


#include <limits>
#include <tuple>
#include <type_traits>
#include <utility>

namespace mcc
{

namespace traits
{

template <typename T>
concept std_pair_c = requires(T t) {
    []<typename T1, typename T2>(std::type_identity<std::pair<T1, T2>>) {

    }(std::type_identity<std::remove_cvref_t<T>>());
};


}  // namespace traits


namespace fsm
{

/*  A TYPE TO HOLD COMPILE-TIME SEQUENCE OF std::pair  */
template <traits::std_pair_c... pairs>
struct pair_holder_t;

template <traits::std_pair_c head, traits::std_pair_c... tail>
struct pair_holder_t<head, tail...> {
    // using self_t = pair_holder_t<head, tail...>;
    // using self_data_t = std::tuple<head, tail...>;
    typedef pair_holder_t<head, tail...> self_t;
    typedef std::tuple<head, tail...> sequence_t;
};

template <>
struct pair_holder_t<> {
    // using self_data_t = std::tuple<>;
    typedef std::tuple<> sequence_t;
    constexpr static bool valid = true;
};

}  // namespace fsm


namespace traits
{
template <typename T>
concept pair_holder_c = requires {
    []<mcc::traits::std_pair_c... Ts>(std::type_identity<fsm::pair_holder_t<Ts...>>) {
        //
    }(std::type_identity<std::remove_cvref_t<T>>());
};

}  // namespace traits


namespace fsm
{

/*  A CLASS TO FIND TYPE OF pair.second ELEMENT BY ITS pair.first one IN PAIR-SEQUENCE  */

template <typename FirstT, traits::pair_holder_c PHLDT>
struct pair_holder_find_t;

template <typename FirstT, typename CurrentFirstT, typename SecondT, mcc::traits::std_pair_c... tail>
struct pair_holder_find_t<FirstT, pair_holder_t<std::pair<CurrentFirstT, SecondT>, tail...>>
    : pair_holder_find_t<FirstT, pair_holder_t<tail...>> {
};

template <typename FirstT>
struct pair_holder_find_t<FirstT, pair_holder_t<>> {
    typedef std::nullptr_t result_t;
};

template <typename FirstT, typename SecondT, mcc::traits::std_pair_c... tail>
struct pair_holder_find_t<FirstT, pair_holder_t<std::pair<FirstT, SecondT>, tail...>> {
    typedef SecondT result_t;
};



/*  A CLASS TO GET ALL pair.first TYPES IN PAIR-SEQUENCE  */

template <traits::pair_holder_c PHLDT>
struct pair_holder_first_t;

template <typename FirstT, typename SecondT, mcc::traits::std_pair_c... tail>
struct pair_holder_first_t<pair_holder_t<std::pair<FirstT, SecondT>, tail...>> {
    typedef decltype(std::tuple_cat(
        std::declval<std::tuple<FirstT>>(),
        std::declval<typename pair_holder_first_t<pair_holder_t<tail...>>::first_t>())) first_t;
};


template <>
struct pair_holder_first_t<pair_holder_t<>> {
    typedef std::tuple<> first_t;
};


/*  A CLASS TO GET ALL pair.second TYPES IN PAIR-SEQUENCE  */

template <traits::pair_holder_c PHLDT>
struct pair_holder_second_t;

template <typename FirstT, typename SecondT, mcc::traits::std_pair_c... tail>
struct pair_holder_second_t<pair_holder_t<std::pair<FirstT, SecondT>, tail...>> {
    typedef decltype(std::tuple_cat(
        std::declval<std::tuple<SecondT>>(),
        std::declval<typename pair_holder_second_t<pair_holder_t<tail...>>::second_t>())) second_t;
};


template <>
struct pair_holder_second_t<pair_holder_t<>> {
    typedef std::tuple<> second_t;
};



/*  A TYPE TO IMPLEMENT TUPLE OF UNIQUE TYPES  */

template <typename... TYPEs>
class unique_tuple_t
{
    template <typename IT, typename UniqTupleT>
    struct in_tuple : in_tuple<IT, typename UniqTupleT::tuple_t> {
    };

    template <typename IT, typename... Ts>
    struct in_tuple<IT, std::tuple<Ts...>> : std::disjunction<std::is_same<IT, Ts>...> {
    };

    // insert
    template <typename IT, typename UniqTupleT, bool = in_tuple<IT, UniqTupleT>::value>
    struct insert;

    template <typename IT, typename... Ts>
    struct insert<IT, std::tuple<Ts...>, false> {
        typedef std::tuple<IT, Ts...> tuple_t;
        typedef std::tuple<> non_unique_t;
    };

    template <typename IT, typename... Ts>
    struct insert<IT, std::tuple<Ts...>, true> {
        typedef std::tuple<Ts...> tuple_t;
        typedef std::tuple<IT> non_unique_t;
    };


    // merge
    template <typename ITupleT, typename OTupleT>
    struct merge;

    template <typename MT, typename... MTs, typename... OTs>
    struct merge<std::tuple<MT, MTs...>, std::tuple<OTs...>> {
        typedef merge<std::tuple<MTs...>, std::tuple<OTs...>> tail_t;
        typedef insert<MT, typename tail_t::tuple_t> curr_tuple_t;

        typedef typename curr_tuple_t::tuple_t tuple_t;
        typedef decltype(std::tuple_cat(std::declval<typename curr_tuple_t::non_unique_t>(),
                                        std::declval<typename tail_t::non_unique_t>())) non_unique_t;
    };

    template <typename... MTs>
    struct merge<std::tuple<>, std::tuple<MTs...>> {
        typedef std::tuple<MTs...> tuple_t;
        typedef std::tuple<> non_unique_t;
    };

public:
    typedef typename merge<std::tuple<TYPEs...>, std::tuple<>>::tuple_t tuple_t;
    typedef typename merge<std::tuple<TYPEs...>, std::tuple<>>::non_unique_t non_unique_t;
};

}  // namespace fsm


namespace traits
{

template <typename T>
concept unique_tuple_c = requires {
    []<typename... Ts>(std::type_identity<fsm::unique_tuple_t<Ts...>>) {}(std::type_identity<std::remove_cvref_t<T>>());
};

}  // namespace traits


namespace fsm
{

// GET INDEX OF GIVEN TYPE IN UNIQUE TUPLE
namespace details
{

// template <typename T, mcc::traits::unique_tuple_c UT, std::size_t I = 0>
template <typename T, typename TupleT, std::size_t I = 0>
struct unique_tuple_type_index_helper_t;


template <typename T, typename HeadT, typename... TailT, std::size_t I>
struct unique_tuple_type_index_helper_t<T, std::tuple<HeadT, TailT...>, I> {
    constexpr static std::size_t index = unique_tuple_type_index_helper_t<T, std::tuple<TailT...>, I + 1>::index;
};


template <typename T, typename... TailT, std::size_t I>
struct unique_tuple_type_index_helper_t<T, std::tuple<T, TailT...>, I> {
    constexpr static std::size_t index = I;
};

template <typename T, std::size_t I>
struct unique_tuple_type_index_helper_t<T, std::tuple<>, I> {
    constexpr static std::size_t index = std::numeric_limits<std::size_t>::max();
    static_assert(false, "INVALID INPUT TYPE!");
};

}  // namespace details


template <typename T, mcc::traits::unique_tuple_c UT>
struct unique_tuple_type_index_t : details::unique_tuple_type_index_helper_t<T, typename UT::tuple_t, 0> {
};

template <typename T, mcc::traits::unique_tuple_c UT>
constexpr static std::size_t unique_tuple_type_index_v = unique_tuple_type_index_t<T, typename UT::tuple_t>::index;

}  // namespace fsm


}  // namespace mcc