#ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUE_HPP
#define SPROUT_FUNCTIONAL_HASH_HASH_VALUE_HPP

#include <cstddef>
#include <limits>
#include <type_traits>
#include <sprout/config.hpp>
#include <sprout/functional/hash/hash_fwd.hpp>

namespace sprout {
	namespace hash_detail {
		template <typename T>
		struct is_basic_number
			: public std::integral_constant<
				bool,
				std::is_integral<T>::value
					&& (sizeof(T) <= sizeof(std::size_t))
			>
		{};
		template <typename T>
		struct is_long_number
			: public std::integral_constant<
				bool,
				std::is_integral<T>::value
					&& (sizeof(T) > sizeof(std::size_t))
					&& std::is_signed<T>::value
			>
		{};
		template <typename T>
		struct is_ulong_number
			: public std::integral_constant<
				bool,
				std::is_integral<T>::value
					&& (sizeof(T) > sizeof(std::size_t))
					&& std::is_unsigned<T>::value
			>
		{};

		template<typename T>
		inline SPROUT_CONSTEXPR std::size_t
		hash_value_signed_2(T val, int length, std::size_t seed, T positive, std::size_t i) {
			return i > 0
				? hash_value_signed_2(
					val,
					length,
					seed ^ static_cast<std::size_t>((positive >> i) + (seed << 6) + (seed >> 2)),
					positive,
					i - std::numeric_limits<std::size_t>::digits
					)
				: seed ^ static_cast<std::size_t>(val + (seed << 6) + (seed >> 2))
				;
		}
		template<typename T>
		inline SPROUT_CONSTEXPR std::size_t
		hash_value_signed_1(T val, int length, std::size_t seed, T positive) {
			return hash_value_signed_2(val, length, seed, positive, length * std::numeric_limits<std::size_t>::digits);
		}
		template<typename T>
		inline SPROUT_CONSTEXPR std::size_t
		hash_value_signed(T val) {
			return sprout::hash_detail::hash_value_signed_1(
				val,
				(std::numeric_limits<T>::digits - 1) / std::numeric_limits<std::size_t>::digits,
				0,
				val < 0 ? -1 - val : val
				);
		}

		template<typename T>
		inline SPROUT_CONSTEXPR std::size_t
		hash_value_unsigned_2(T val, int length, std::size_t seed, std::size_t i) {
			return i > 0
				? hash_value_unsigned_2(
					val,
					length,
					seed ^ static_cast<std::size_t>((val >> i) + (seed << 6) + (seed >> 2)),
					i - std::numeric_limits<std::size_t>::digits
					)
				: seed ^ static_cast<std::size_t>(val + (seed << 6) + (seed >> 2))
				;
		}
		template<typename T>
		inline SPROUT_CONSTEXPR std::size_t
		hash_value_unsigned_1(T val, int length, std::size_t seed) {
			return hash_value_unsigned_2(val, length, seed, length * std::numeric_limits<std::size_t>::digits);
		}
		template<typename T>
		inline SPROUT_CONSTEXPR std::size_t
		hash_value_unsigned(T val) {
			return sprout::hash_detail::hash_value_unsigned_1(
				val,
				(std::numeric_limits<T>::digits - 1) / std::numeric_limits<std::size_t>::digits,
				0
				);
		}

		inline std::size_t
		hash_value_pointer_1(std::size_t x) {
			return x + (x >> 3);
		}
		template<typename T>
		std::size_t
		hash_value_pointer(T const* v) {
			return sprout::hash_detail::hash_value_pointer_1(static_cast<std::size_t>(reinterpret_cast<std::ptrdiff_t>(v)));
		}
	}	// namespace hash_detail

	//
	// hash_value
	//
	template<typename T>
	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_basic_number<T>::value, std::size_t>::type
	hash_value(T v) {
		return static_cast<std::size_t>(v);
	}
	template<typename T>
	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_long_number<T>::value, std::size_t>::type
	hash_value(T v) {
		return sprout::hash_detail::hash_value_signed(v);
	}
	template<typename T>
	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_ulong_number<T>::value, std::size_t>::type
	hash_value(T v) {
		return sprout::hash_detail::hash_value_unsigned(v);
	}
	template<typename T>
	inline SPROUT_CONSTEXPR typename std::enable_if<std::is_enum<T>::value, std::size_t>::type
	hash_value(T v) {
		return sprout::hash_value(static_cast<typename std::underlying_type<T>::type>(v));
	}
	template<typename T>
	inline SPROUT_CONSTEXPR typename std::enable_if<std::is_pointer<typename std::remove_reference<T>::type>::value, std::size_t>::type
	hash_value(T&& v) {
		return sprout::hash_detail::hash_value_pointer(v);
	}
	template<typename T, std::size_t N>
	inline SPROUT_CONSTEXPR std::size_t
	hash_value(T const (&v)[N]) {
		return sprout::hash_range(v);
	}
}	// namespace sprout

#include <sprout/functional/hash/hash_range.hpp>

#endif	// #ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUE_HPP