#include "grains.h"

#include <limits>
#include <stdexcept>


namespace grains {

using namespace std;


namespace {
    
static const index_t number_of_squares = 64;

template <typename T>
struct total_as_max
{
    static inline T total()
    {
        return numeric_limits<T>::max();
    }
};

template <typename T>
struct total_by_shift
{
    static inline T total()
    {
        return T(1) << number_of_squares - 1;
    }
};

static_assert(number_of_squares <= numeric_limits<ulong_t>::digits,
              "grains::ulong_t is too small for grains::total");

typedef conditional<number_of_squares == numeric_limits<ulong_t>::digits,
                    total_as_max<ulong_t>,
                    total_by_shift<ulong_t>>::type total_policy_t;
}


ulong_t square(index_t index)
{
    if (index < 1 || index > number_of_squares)
        throw domain_error("invalid square number");

    return ulong_t(1) << (index - 1);
}

ulong_t total()
{
    return total_policy_t::total();
}

}