#ifndef CONCAT_HPP_
#define CONCAT_HPP_

#include "symbol.hpp"

namespace detail
{

template< unsigned int N , unsigned int Index , class ...Symbols >
struct get_impl_wrapper;

template< class ...Symbols >
class concat_impl;
template<>
class concat_impl<>
    : public symbol
{
public:
    template< class CharType >
    constexpr concat_impl( const_string< CharType > str , std::size_t begin = 0 )
        : symbol( begin )
    {
    }
};
template< class Head , class ...Tail >
class concat_impl< Head , Tail... >
    : public concat_impl< Tail... >
{
public:
    template< class CharType >
    constexpr concat_impl( const_string< CharType > str , std::size_t begin = 0 )
        : concat_impl< Tail... >( str , Head( str , begin ).end() ) ,
          obj( str , begin )
    {
    }
private:
    template< unsigned int N , unsigned int Index , class ...Symbols >
    friend struct get_impl_wrapper;
    Head obj;
};



template< unsigned int N , unsigned int Index , class ...Symbols >
struct get_impl_wrapper
{
    static_assert( sizeof...( Symbols ) != 0 , "get< N >( concat ) - N too big" );
    static constexpr void get_impl( concat_impl<> )
    {
    }
};
template< unsigned int N , unsigned int Index , class Head , class ...Tail >
struct get_impl_wrapper< N , Index , Head , Tail... >
{
    static constexpr auto get_impl( concat_impl< Head , Tail... > conc ) -> decltype( get_impl_wrapper< N , Index + 1 , Tail... >::get_impl( conc ) )
    {
        return get_impl_wrapper< N , Index + 1 , Tail... >::get_impl( conc );
    }
};
template< unsigned int N , class Head , class ...Symbols >
struct get_impl_wrapper< N , N , Head , Symbols... >
{
    static constexpr Head get_impl( concat_impl< Head , Symbols... > conc )
    {
        return conc.obj;
    }
};

}

template< class ...Symbols >
class concat
    : public detail::concat_impl< Symbols... >
{
public:
    template< class CharType >
    constexpr concat( const_string< CharType > str , std::size_t begin = 0 )
        : detail::concat_impl< Symbols... >( str , begin )
    {
    }
    template< unsigned int N >
    constexpr auto get() -> decltype( detail::get_impl_wrapper< N , 0 , Symbols... >::get_impl( *static_cast< concat< Symbols... >* >( 0 ) ) )
    {
        return detail::get_impl_wrapper< N , 0 , Symbols... >::get_impl( *this );
    }
};
template< unsigned int N , class ...Symbols >
constexpr auto get( concat< Symbols... > conc ) -> decltype( detail::get_impl_wrapper< N , 0 , Symbols... >::get_impl( conc ) )
{
    return detail::get_impl_wrapper< N , 0 , Symbols... >::get_impl( conc );
}


#endif