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#pragma once

#include <climits>
#include <functional>
#include <type_traits>

#if defined(__GNUC__)
#define OV_likely(x) __builtin_expect(!!(x), 1)
#define OV_unlikely(x) __builtin_expect(!!(x), 0)
#else
#define OV_likely(x) x
#define OV_unlikely(x) x
#endif

// Turn argument to string constant:
// https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html#Stringizing
#ifndef _OV_STR
#define _OV_STR(m_x) #m_x
#define _OV_MKSTR(m_x) _OV_STR(m_x)
#endif

namespace OpenVic::utility {
   [[noreturn]] inline void unreachable() {
      // Uses compiler specific extensions if possible.
      // Even if no extension is used, undefined behavior is still raised by
      // an empty function body and the noreturn attribute.
#ifdef __GNUC__ // GCC, Clang, ICC
      __builtin_unreachable();
#elif defined(_MSC_VER) // MSVC
      __assume(false);
#endif
   }

   template<class T>
   constexpr inline void hash_combine(std::size_t& s, const T& v) {
      std::hash<T> h;
      s ^= h(v) + 0x9e3779b9 + (s << 6) + (s >> 2);
   }

   template<size_t Shift, class T>
   constexpr inline void hash_combine_index(std::size_t& s, const T& v) {
      std::hash<T> h;
      if constexpr (Shift == 0) {
         s = h(v);
      } else {
         s ^= h(v) << Shift;
      }
   }

   template<class T, typename... Args>
   constexpr void perfect_hash(std::size_t& s, T&& v, Args&&... args) {
      static_assert(
         sizeof(T) + (sizeof(Args) + ...) <= sizeof(std::size_t), "Perfect hashes must be able to fit into size_t"
      );
      std::hash<T> h;
      if constexpr (sizeof...(args) == 0) {
         s = h(v);
      } else {
         const std::tuple arg_tuple { args... };
         s = h(v) << (sizeof(T) * CHAR_BIT);
         (
            [&] {
               // If args is not last pointer of args
               if (static_cast<const void*>(&(std::get<sizeof...(args) - 1>(arg_tuple))) !=
                  static_cast<const void*>(&args)) {
                  s <<= sizeof(Args) * CHAR_BIT;
               }
               s |= std::hash<Args> {}(args);
            }(),
            ...
         );
      }
   }

   template<typename T, template<typename...> class Z>
   struct is_specialization_of : std::false_type {};

   template<typename... Args, template<typename...> class Z>
   struct is_specialization_of<Z<Args...>, Z> : std::true_type {};

   template<typename T, template<typename...> class Z>
   inline constexpr bool is_specialization_of_v = is_specialization_of<T, Z>::value;

   inline constexpr auto three_way(auto&& left, auto&& right) {
      // This is Apple's fault again
      #if __cpp_lib_three_way_comparison >= 201907L
      if constexpr (std::three_way_comparable_with<std::decay_t<decltype(left)>, std::decay_t<decltype(right)>>) {
         return left <=> right;
      } else
      #endif
      {
         if (left < right) {
            return std::weak_ordering::less;
         } else if (left > right) {
            return std::weak_ordering::greater;
         } else {
            return std::weak_ordering::equivalent;
         }
      }
   };

}