#pragma once
#include <cstdint> // (u)int*_t

#if defined(__GLIBC__)
#  include <endian.h>
#  if __BYTE_ORDER == __LITTLE_ENDIAN
#    define OX_BIG_ENDIAN false
#    define OX_LITTLE_ENDIAN true
#  elif __BYTE_ORDER == __BIG_ENDIAN
#    define OX_BIG_ENDIAN true
#    define OX_LITTLE_ENDIAN false
#  else
#    error Whatever your endianness is... Onyx does not like it.
#  endif
#elif defined(_BIG_ENDIAN)
#  define OX_BIG_ENDIAN true
#  define OX_LITTLE_ENDIAN false
#elif defined(_LITTLE_ENDIAN)
#  define OX_BIG_ENDIAN false
#  define OX_LITTLE_ENDIAN true
#elif defined(__sparc)     || defined(__sparc__) || defined(_POWER) \
   || defined(__powerpc__) || defined(__ppc__)   || defined(__hpux) \
   || defined(_MIPSEB)     || defined(_POWER)    || defined(__s390__)
#  define OX_BIG_ENDIAN true
#  define OX_LITTLE_ENDIAN false
#elif defined(__i386__) || defined(__alpha__) || defined(__ia64) \
   || defined(__ia64__) || defined(_M_IX86)   || defined(_M_IA64) \
   || defined(_M_ALPHA) || defined(__amd64)   || defined(__amd64__) \
   || defined(_M_AMD64) || defined(__x86_64)  || defined(__x86_64__) \
   || defined(_M_X64)
#  define OX_BIG_ENDIAN false
#  define OX_LITTLE_ENDIAN true
#else
#  error "Onyx could not detect your machine's endianness."
#endif

namespace onyx { namespace util {
  /// \brief Test whether the current machine runs in big-endian mode.
  /// \note In big-endian mode the most significant byte is stored at
  /// the lowest address, so the number \c 0x04030201UL is laid out as
  /// \c 0x04, \c 0x03, \c 0x02, \c 0x01 in memory.
  constexpr bool IsBigEndian = OX_BIG_ENDIAN;
  /// \brief Test whether the current machine runs in little-endian mode.
  /// \note In little-endian mode the most significant byte is stored at
  /// the highest address, so the number \c 0x04030201UL is laid out as
  /// \c 0x01, \c 0x02, \c 0x03, \c 0x04 in memory.
  constexpr bool IsLittleEndian = OX_LITTLE_ENDIAN;
  /// \brief Does nothing.
  /// \param x A 1-byte integer value.
  /// \return The very same value.
  /// \note Try not to need to do this.
  inline uint8_t byte_swap(uint8_t x) noexcept {return x;}
  /// \brief Swaps the integer's bytes.
  /// \param x A 2-byte integer value.
  /// \return The byte-swapped value.
  /// \note Try not to need to do this.
  inline uint16_t byte_swap(uint16_t x) noexcept {return __builtin_bswap16(x);}
  /// \brief Swaps the integer's bytes.
  /// \param x A 4-byte integer value.
  /// \return The byte-swapped value.
  /// \note Try not to need to do this.
  inline uint32_t byte_swap(uint32_t x) noexcept {return __builtin_bswap32(x);}
  /// \brief Swaps the integer's bytes.
  /// \param x A 8-byte integer value.
  /// \return The byte-swapped value.
  /// \note Try not to need to do this.
  inline uint64_t byte_swap(uint64_t x) noexcept {return __builtin_bswap64(x);}
}} // namespace onyx::util