/*
 * @Author: wkh
 * @Date: 2021-11-03 22:38:05
 * @LastEditTime: 2021-11-05 14:55:25
 * @LastEditors: wkh
 * @Description: 
 * @FilePath: /GP/Typelist/TypeList.hpp
 * 
 */

#pragma once
#include <iostream>
#include <tuple>
namespace TypeList
{
    template<typename... Args>
    class TypeList{};


    
    template<typename List>
    class Front{};
    
    template<typename Head,typename ...Tail>
    class Front<TypeList<Head,Tail...>>
    {
    public:
        using type = Head;
    };

    template<typename T>
    using front = typename Front<T>::type;


    template<typename List>
    class Tail{};
    
    template<typename... Head,typename T>
    class Tail<TypeList<Head...,T>>
    {
    public:
       using type = T;
    };

    template<typename List>
    using tail = typename Tail<List>::type;
    


    template<typename T>
    class PopFront;

    template<typename Head,typename ...Tail>
    class PopFront<TypeList<Head,Tail...>>
    {
    public:
        using type = TypeList<Tail...>;
    };

    template<typename List>
    using pop_front = typename PopFront<List>::type;



    template<typename T,typename NewType>
    class PushFrontT;

    template<typename ...Types,typename NewType>
    class PushFrontT<TypeList<Types...>,NewType>
    {
    public:
          using type = TypeList<NewType,Types...>;
    };

    template<typename List,typename NewType>
    using push_front = typename PushFrontT<List,NewType>::type;



    template<typename T,typename NewType>
    class PushBack;

    template<typename ...Types,typename NewType>
    class PushBack<TypeList<Types...>,NewType>
    {
    public:
          using type = TypeList<Types...,NewType>;
    };

    template<typename List,typename NewType>
    using push_back = typename PushBack<List,NewType>::type;
    

    template<typename List,std::size_t N>
    class NthType : public NthType<pop_front<List>,N - 1>
    {};

    template<typename List>
    class NthType<List,0> : public Front<List>
    {};

    template<typename List,std::size_t N>
    using NType = typename NthType<List,N>::type;

    template<typename ...Args>
    std::tuple<Args...> Tuple(TypeList<Args...>)
    {
        return std::tuple<Args...>();
    }   
}