#pragma once

#if !defined(MIJIN_UTIL_HASH_HPP_INCLUDED)
#define MIJIN_UTIL_HASH_HPP_INCLUDED 1

#include <functional>
#include <tuple>
#include <utility>

namespace mijin
{
template<typename T, typename THasher = std::hash<T>>
inline void hashCombine(std::size_t& seed, const T& value, const THasher& hasher = {})
{
    seed ^= hasher(value) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}
}

template<typename... T>
struct std::hash<std::tuple<T...>>
{
    std::size_t operator()(const std::tuple<T...>& tuple) const noexcept
    {
        return hashImpl(tuple, std::index_sequence_for<T...>());
    }

    template<std::size_t... indices>
    std::size_t hashImpl(const std::tuple<T...>& tuple, std::index_sequence<indices...>) const noexcept
    {
        std::size_t result = 0;
        (mijin::hashCombine(result, std::get<indices>(tuple)), ...);
        return result;
    }
};

#endif // MIJIN_UTIL_HASH_HPP_INCLUDED