// Native runtime - Memory utilities, allocation, and byte-swap operations
// Part of the AC6 Recompilation native foundation

#pragma once

#include <cstdlib>
#include <cstring>
#include <filesystem>
#include <functional>
#include <string>
#include <string_view>
#include <type_traits>

#include <native/assert.h>
#include <native/platform.h>
#include <rex/types.h>

namespace rex {
namespace memory {

// For variable declarations (not return values or `this` pointer).
// Not propagated.
#define REX_RESTRICT_VAR __restrict

// Aliasing-safe bit reinterpretation.
template <typename Dst, typename Src>
void Reinterpret(Dst& REX_RESTRICT_VAR dst, const Src& REX_RESTRICT_VAR src) {
  static_assert(sizeof(Dst) == sizeof(Src));
  static_assert(std::is_trivially_copyable_v<Dst>);
  static_assert(std::is_trivially_copyable_v<Src>);
  std::memcpy(&dst, &src, sizeof(Dst));
}

template <typename Dst, typename Src>
Dst Reinterpret(const Src& REX_RESTRICT_VAR src) {
  Dst dst;
  Reinterpret(dst, src);
  return dst;
}

// Returns the native page size of the system, in bytes.
// This should be ~4KiB.
size_t page_size();

// Returns the allocation granularity of the system, in bytes.
// This is likely 64KiB.
size_t allocation_granularity();

enum class PageAccess {
  kNoAccess = 0,
  kReadOnly = 1 << 0,
  kReadWrite = kReadOnly | 1 << 1,
  kExecuteReadOnly = kReadOnly | 1 << 2,
  kExecuteReadWrite = kReadWrite | 1 << 2,
};

enum class AllocationType {
  kReserve = 1 << 0,
  kCommit = 1 << 1,
  kReserveCommit = kReserve | kCommit,
};

enum class DeallocationType {
  kRelease = 1 << 0,
  kDecommit = 1 << 1,
};

// Whether the host allows the pages to be allocated or mapped with
// PageAccess::kExecuteReadWrite
bool IsWritableExecutableMemorySupported();

// Whether PageAccess::kExecuteReadWrite is a supported and preferred way of
// writing executable memory
bool IsWritableExecutableMemoryPreferred();

// Allocates a block of memory at the given page-aligned base address.
void* AllocFixed(void* base_address, size_t length, AllocationType allocation_type,
                 PageAccess access);

// Deallocates and/or releases the given block of memory.
bool DeallocFixed(void* base_address, size_t length, DeallocationType deallocation_type);

// Sets the access rights for the given block of memory
bool Protect(void* base_address, size_t length, PageAccess access,
             PageAccess* out_old_access = nullptr);

// Queries a region of pages to get the access rights.
bool QueryProtect(void* base_address, size_t& length, PageAccess& access_out);

// Allocates a block of memory for a type with the given alignment.
template <typename T>
inline T* AlignedAlloc(size_t alignment) {
#if REX_PLATFORM_WIN32
  return reinterpret_cast<T*>(_aligned_malloc(sizeof(T), alignment));
#else
  void* ptr = nullptr;
  if (posix_memalign(&ptr, alignment, sizeof(T))) {
    return nullptr;
  }
  return reinterpret_cast<T*>(ptr);
#endif
}

// Frees memory previously allocated with AlignedAlloc.
template <typename T>
void AlignedFree(T* ptr) {
#if REX_PLATFORM_WIN32
  _aligned_free(ptr);
#else
  free(ptr);
#endif
}

// Opaque file mapping handle.
using FileMappingHandle = intptr_t;
constexpr FileMappingHandle kFileMappingHandleInvalid = -1;

FileMappingHandle CreateFileMappingHandle(const std::filesystem::path& path, size_t length,
                                          PageAccess access, bool commit);
void CloseFileMappingHandle(FileMappingHandle handle, const std::filesystem::path& path);
void* MapFileView(FileMappingHandle handle, void* base_address, size_t length, PageAccess access,
                  size_t file_offset);
bool UnmapFileView(FileMappingHandle handle, void* base_address, size_t length);

inline size_t hash_combine(size_t seed) {
  return seed;
}

template <typename T, typename... Ts>
size_t hash_combine(size_t seed, const T& v, const Ts&... vs) {
  std::hash<T> hasher;
  seed ^= hasher(v) + 0x9E3779B9 + (seed << 6) + (seed >> 2);
  return hash_combine(seed, vs...);
}

inline void* low_address(void* address) {
  return reinterpret_cast<void*>(uint64_t(address) & 0xFFFFFFFF);
}

void copy_128_aligned(void* dest, const void* src, size_t count);

void copy_and_swap_16_aligned(void* dest, const void* src, size_t count);
void copy_and_swap_16_unaligned(void* dest, const void* src, size_t count);
void copy_and_swap_32_aligned(void* dest, const void* src, size_t count);
void copy_and_swap_32_unaligned(void* dest, const void* src, size_t count);
void copy_and_swap_64_aligned(void* dest, const void* src, size_t count);
void copy_and_swap_64_unaligned(void* dest, const void* src, size_t count);
void copy_and_swap_16_in_32_aligned(void* dest, const void* src, size_t count);
void copy_and_swap_16_in_32_unaligned(void* dest, const void* src, size_t count);

template <typename T>
void copy_and_swap(T* dest, const T* src, size_t count) {
  bool is_aligned =
      reinterpret_cast<uintptr_t>(dest) % 32 == 0 && reinterpret_cast<uintptr_t>(src) % 32 == 0;
  if (sizeof(T) == 1) {
    std::memcpy(dest, src, count);
  } else if (sizeof(T) == 2) {
    auto ps = reinterpret_cast<const uint16_t*>(src);
    auto pd = reinterpret_cast<uint16_t*>(dest);
    if (is_aligned) {
      copy_and_swap_16_aligned(pd, ps, count);
    } else {
      copy_and_swap_16_unaligned(pd, ps, count);
    }
  } else if (sizeof(T) == 4) {
    auto ps = reinterpret_cast<const uint32_t*>(src);
    auto pd = reinterpret_cast<uint32_t*>(dest);
    if (is_aligned) {
      copy_and_swap_32_aligned(pd, ps, count);
    } else {
      copy_and_swap_32_unaligned(pd, ps, count);
    }
  } else if (sizeof(T) == 8) {
    auto ps = reinterpret_cast<const uint64_t*>(src);
    auto pd = reinterpret_cast<uint64_t*>(dest);
    if (is_aligned) {
      copy_and_swap_64_aligned(pd, ps, count);
    } else {
      copy_and_swap_64_unaligned(pd, ps, count);
    }
  } else {
    assert_always("Invalid memory::copy_and_swap size");
  }
}

/// Load a value of type T from arbitrary memory (handles unaligned access).
template <typename T>
inline T load(const void* mem) {
  static_assert(std::is_trivially_copyable_v<T>, "T must be trivially copyable");
  T result;
  std::memcpy(&result, mem, sizeof(T));
  return result;
}

/// Load a value of type T from memory and byte-swap it.
template <typename T>
inline T load_and_swap(const void* mem) {
  return byte_swap(load<T>(mem));
}

// String specializations need custom logic
template <>
inline std::string load_and_swap<std::string>(const void* mem) {
  std::string value;
  for (int i = 0;; ++i) {
    auto c = load_and_swap<uint8_t>(reinterpret_cast<const uint8_t*>(mem) + i);
    if (!c) {
      break;
    }
    value.push_back(static_cast<char>(c));
  }
  return value;
}
template <>
inline std::u16string load_and_swap<std::u16string>(const void* mem) {
  std::u16string value;
  for (int i = 0;; ++i) {
    auto c = load_and_swap<uint16_t>(reinterpret_cast<const uint16_t*>(mem) + i);
    if (!c) {
      break;
    }
    value.push_back(static_cast<wchar_t>(c));
  }
  return value;
}

/// Store a value of type T to arbitrary memory (handles unaligned access).
template <typename T>
inline void store(void* mem, const T& value) {
  static_assert(std::is_trivially_copyable_v<T>, "T must be trivially copyable");
  std::memcpy(mem, &value, sizeof(T));
}

/// Store a byte-swapped value of type T to memory.
template <typename T>
inline void store_and_swap(void* mem, const T& value) {
  store(mem, byte_swap(value));
}

// String specializations need custom logic
template <>
inline void store_and_swap<std::string_view>(void* mem, const std::string_view& value) {
  for (size_t i = 0; i < value.size(); ++i) {
    store_and_swap<uint8_t>(reinterpret_cast<uint8_t*>(mem) + i, value[i]);
  }
}
template <>
inline void store_and_swap<std::string>(void* mem, const std::string& value) {
  return store_and_swap<std::string_view>(mem, value);
}
template <>
inline void store_and_swap<std::u16string_view>(void* mem, const std::u16string_view& value) {
  for (size_t i = 0; i < value.size(); ++i) {
    store_and_swap<uint16_t>(reinterpret_cast<uint16_t*>(mem) + i, value[i]);
  }
}
template <>
inline void store_and_swap<std::u16string>(void* mem, const std::u16string& value) {
  return store_and_swap<std::u16string_view>(mem, value);
}

using fourcc_t = uint32_t;

// Get FourCC in host byte order
constexpr inline fourcc_t make_fourcc(char a, char b, char c, char d) {
  return fourcc_t((static_cast<fourcc_t>(a) << 24) | (static_cast<fourcc_t>(b) << 16) |
                  (static_cast<fourcc_t>(c) << 8) | static_cast<fourcc_t>(d));
}

// Get FourCC in host byte order
constexpr inline fourcc_t make_fourcc(const std::string_view fourcc) {
  if (fourcc.length() != 4) {
    throw std::runtime_error("Invalid fourcc length");
  }
  return make_fourcc(fourcc[0], fourcc[1], fourcc[2], fourcc[3]);
}

}  // namespace memory
}  // namespace rex