// SPDX-License-Identifier: Apache-2.0

// SPDX-FileCopyrightText: 2019-2024 Second State INC

#pragma once

#include "common/defines.h"

#include "common/errcode.h"

#include "common/span.h"

#include "common/types.h"

#include "host/wasi/error.h"

#include "host/wasi/vfs.h"

#include <functional>

#include <limits>

#include <optional>

#include <string_view>

#include <vector>

#if WASMEDGE_OS_LINUX || WASMEDGE_OS_MACOS

#include <dirent.h>

#include <sys/stat.h>

#include <unordered_map>

#elif WASMEDGE_OS_WINDOWS

#include "system/winapi.h"

#endif

#if WASMEDGE_OS_LINUX

#if defined(__GLIBC_PREREQ)

#if defined(_LIBCPP_GLIBC_PREREQ)

#undef _LIBCPP_GLIBC_PREREQ

#endif

#define _LIBCPP_GLIBC_PREREQ(a, b) 0

#else

#if defined(_LIBCPP_GLIBC_PREREQ)

#define __GLIBC_PREREQ(a, b) _LIBCPP_GLIBC_PREREQ(a, b)

#else

#define __GLIBC_PREREQ(a, b) 1

#endif

#endif

#endif

#if WASMEDGE_OS_LINUX

#include <sys/epoll.h>

#endif

#if WASMEDGE_OS_MACOS

#include <sys/event.h>

#endif

namespace WasmEdge {

namespace Host {

namespace WASI {

#if WASMEDGE_OS_LINUX || WASMEDGE_OS_MACOS

struct FdHolder {

  FdHolder(const FdHolder &) = delete;

  FdHolder &operator=(const FdHolder &) = delete;

  FdHolder(FdHolder &&RHS) noexcept

      : Fd(std::exchange(RHS.Fd, -1)), Cleanup(RHS.Cleanup) {

    RHS.Cleanup = true;

  }

  FdHolder &operator=(FdHolder &&RHS) noexcept {

    using std::swap;

    swap(Fd, RHS.Fd);

    Cleanup = RHS.Cleanup;

    RHS.Cleanup = true;

    return *this;

  }

  constexpr FdHolder() noexcept : Fd(-1), Cleanup(true) {}

  ~FdHolder() noexcept {

    if (Cleanup) {

      reset();

    }

  }

  explicit constexpr FdHolder(int Fd, bool Cleanup = true) noexcept

      : Fd(Fd), Cleanup(Cleanup) {}

  constexpr bool ok() const noexcept { return Fd >= 0; }

  void reset() noexcept;

  int release() noexcept { return std::exchange(Fd, -1); }

  void emplace(int NewFd) noexcept {

    reset();

    Fd = NewFd;

  }

  int getFd() noexcept { return Fd; }

  int Fd = -1;

  bool Cleanup : 1;

};

struct DirHolder {

  DirHolder(const DirHolder &) = delete;

  DirHolder &operator=(const DirHolder &) = delete;

  DirHolder(DirHolder &&RHS) noexcept {

    using std::swap;

    swap(Dir, RHS.Dir);

    swap(Cookie, RHS.Cookie);

  }

  DirHolder &operator=(DirHolder &&RHS) noexcept {

    using std::swap;

    swap(Dir, RHS.Dir);

    swap(Cookie, RHS.Cookie);

    return *this;

  }

  DirHolder() noexcept = default;

  explicit DirHolder(DIR *D) noexcept : Dir(D) {}

  constexpr bool ok() const noexcept { return Dir != nullptr; }

  ~DirHolder() noexcept { reset(); }

  void reset() noexcept;

  void emplace(DIR *NewDir) noexcept {

    reset();

    Dir = NewDir;

  }

  DIR *Dir = nullptr;

  uint64_t Cookie = 0;

  static_assert(__STDCPP_DEFAULT_NEW_ALIGNMENT__ >= alignof(__wasi_dirent_t));

  std::vector<uint8_t> Buffer;

};

#endif

#if WASMEDGE_OS_LINUX

struct TimerHolder {

  TimerHolder(const TimerHolder &) = delete;

  TimerHolder &operator=(const TimerHolder &) = delete;

  TimerHolder(TimerHolder &&RHS) noexcept {

    using std::swap;

    swap(Id, RHS.Id);

  }

  TimerHolder &operator=(TimerHolder &&RHS) noexcept {

    using std::swap;

    swap(Id, RHS.Id);

    return *this;

  }

  constexpr TimerHolder() = default;

  explicit constexpr TimerHolder(timer_t T) noexcept : Id(T) {}

  ~TimerHolder() noexcept { reset(); }

  void reset() noexcept;

  void emplace(timer_t NewId) noexcept {

    reset();

    Id = NewId;

  }

  std::optional<timer_t> Id;

};

#endif

#if WASMEDGE_OS_WINDOWS

struct HandleHolder {

  enum class HandleType : uint8_t {

    NormalHandle,

    StdHandle,

    NormalSocket,

  };

  HandleHolder(const HandleHolder &) = delete;

  HandleHolder &operator=(const HandleHolder &) = delete;

  HandleHolder(HandleHolder &&RHS) noexcept {

    using std::swap;

    swap(*this, RHS);

  }

  HandleHolder &operator=(HandleHolder &&RHS) noexcept {

    using std::swap;

    swap(*this, RHS);

    return *this;

  }

  constexpr HandleHolder() noexcept = default;

  ~HandleHolder() noexcept { reset(); }

  HandleHolder(winapi::HANDLE_ Handle, bool IsStdHandle) noexcept

      : Handle(likely(Handle != winapi::INVALID_HANDLE_VALUE_) ? Handle

                                                               : nullptr),

        Type(IsStdHandle ? HandleType::StdHandle : HandleType::NormalHandle) {}

  HandleHolder(winapi::SOCKET_ Socket) noexcept

      : Socket(Socket), Type(HandleType::NormalSocket) {}

  HandleHolder(const std::filesystem::path &Path,

               const winapi::DWORD_ AccessFlags,

               const winapi::DWORD_ ShareFlags,

               const winapi::DWORD_ CreationDisposition,

               const winapi::DWORD_ AttributeFlags) noexcept;

  bool reopen(const winapi::DWORD_ AccessFlags, const winapi::DWORD_ ShareFlags,

              const winapi::DWORD_ AttributeFlags) noexcept;

  constexpr bool ok() const noexcept { return Handle != nullptr; }

  constexpr bool isStdHandle() const noexcept {

    return Type == HandleType::StdHandle;

  }

  constexpr bool isSocket() const noexcept {

    return Type == HandleType::NormalSocket;

  }

  void reset() noexcept;

  winapi::HANDLE_ release() noexcept { return std::exchange(Handle, nullptr); }

  winapi::HANDLE_ exchange(winapi::HANDLE_ NewHandle) noexcept {

    return std::exchange(Handle, NewHandle);

  }

  void emplace(winapi::HANDLE_ NewHandle) noexcept {

    reset();

    Handle = NewHandle;

  }

  friend void swap(HandleHolder &LHS, HandleHolder &RHS) noexcept {

    using std::swap;

    swap(LHS.Handle, RHS.Handle);

    swap(LHS.Type, RHS.Type);

  }

  WasiExpect<void> filestatGet(__wasi_filestat_t &FileStat) const noexcept;

  union {

    winapi::HANDLE_ Handle = nullptr;

    winapi::SOCKET_ Socket;

  };

  HandleType Type = HandleType::NormalHandle;

};

template <typename T> class FindHolderBase {

private:

  struct Proxy : T {

    static void doReset(T &Base) noexcept {

      const auto Ptr = &T::doReset;

      return (Base.*Ptr)();

    }

    static WasiExpect<void> doRewind(T &Base, bool First) noexcept {

      const auto Ptr = &T::doRewind;

      return (Base.*Ptr)(First);

    }

    static bool doNext(T &Base) noexcept {

      const auto Ptr = &T::doNext;

      return (Base.*Ptr)();

    }

    static WasiExpect<void> doLoadDirent(T &Base) noexcept {

      const auto Ptr = &T::doLoadDirent;

      return (Base.*Ptr)();

    }

  };

public:

  FindHolderBase(FindHolderBase &&RHS) noexcept {

    using std::swap;

    swap(Handle, RHS.Handle);

    swap(Cookie, RHS.Cookie);

    swap(Buffer, RHS.Buffer);

  }

  FindHolderBase &operator=(FindHolderBase &&RHS) noexcept {

    using std::swap;

    swap(Handle, RHS.Handle);

    swap(Cookie, RHS.Cookie);

    swap(Buffer, RHS.Buffer);

    return *this;

  }

  FindHolderBase() noexcept = default;

  FindHolderBase(const FindHolderBase &) noexcept = delete;

  FindHolderBase &operator=(const FindHolderBase &) noexcept = delete;

  constexpr bool ok() const noexcept { return Handle != nullptr; }

  ~FindHolderBase() noexcept { reset(); }

  WasiExpect<void> emplace(winapi::HANDLE_ PathHandle) noexcept;

  void reset() noexcept {

    Proxy::doReset(static_cast<T &>(*this));

    Path.clear();

    Handle = nullptr;

    Cookie = 0;

    Buffer.clear();

  }

  WasiExpect<void> seek(uint64_t NewCookie) noexcept;

  bool next() noexcept;

  WasiExpect<void> loadDirent() noexcept;

  size_t write(Span<uint8_t> Output) noexcept;

protected:

  auto getPath() const noexcept { return Path; }

  auto getHandle() const noexcept { return Handle; }

  void setHandle(winapi::HANDLE_ New) noexcept { Handle = New; }

  auto getCookie() const noexcept { return Cookie; }

  Span<const uint8_t> getBuffer() const noexcept { return Buffer; }

  Span<uint8_t> getBuffer() noexcept { return Buffer; }

  void resizeBuffer(size_t Size) noexcept { Buffer.resize(Size); }

private:

  std::filesystem::path Path;

  winapi::HANDLE_ Handle = nullptr;

  uint64_t Cookie = 0;

  static_assert(__STDCPP_DEFAULT_NEW_ALIGNMENT__ >= alignof(__wasi_dirent_t));

  std::vector<uint8_t> Buffer;

};

#if !WINAPI_PARTITION_DESKTOP || NTDDI_VERSION >= NTDDI_VISTA

class FindHolder : public FindHolderBase<FindHolder> {

public:

  const winapi::FILE_ID_BOTH_DIR_INFO_ &getData() const noexcept;

protected:

  void doReset() noexcept;

  WasiExpect<void> doRewind(bool First) noexcept;

  bool doNext() noexcept;

  WasiExpect<void> doLoadDirent() noexcept;

private:

  bool nextData() noexcept;

  WASMEDGE_WINAPI_DETAIL_EXTENSION union {

    winapi::FILE_ID_BOTH_DIR_INFO_ FindData;

    std::array<uint8_t,

               sizeof(winapi::FILE_ID_BOTH_DIR_INFO_) +

                   sizeof(wchar_t[winapi::UNICODE_STRING_MAX_CHARS_ + 1])>

        FindDataPadding;

  } FindDataUnion;

  uint32_t Cursor = 0;

  static_assert(std::numeric_limits<decltype(Cursor)>::max() >

                sizeof(FindDataUnion));

};

#else

class FindHolder : public FindHolderBase<FindHolder> {

protected:

  WasiExpect<winapi::HANDLE_> doEmplace(const std::filesystem::path &NewPath,

                                        winapi::HANDLE_ PathHandle) noexcept;

  void doReset() noexcept;

  WasiExpect<void> doRewind(bool First) noexcept;

  bool doNext() noexcept;

  WasiExpect<void> doLoadDirent() noexcept;

private:

  winapi::WIN32_FIND_DATAW_ FindData;

};

#endif

#endif

enum class TriggerType {

  Level,

  Edge,

};

class Poller;

class INode

#if WASMEDGE_OS_LINUX || WASMEDGE_OS_MACOS

    : public FdHolder

#elif WASMEDGE_OS_WINDOWS

    : public HandleHolder

#endif

{

public:

  INode(const INode &) = delete;

  INode &operator=(const INode &) = delete;

  INode(INode &&RHS) noexcept = default;

  INode &operator=(INode &&RHS) noexcept = default;

  static INode stdIn() noexcept;

  static INode stdOut() noexcept;

  static INode stdErr() noexcept;

  static WasiExpect<INode> fromFd(int32_t Fd);

  /// Open a file or directory.

  ///

  /// @param[in] Path The absolute path of the file or directory to open.

  /// @param[in] OpenFlags The method by which to open the file.

  /// @param[in] FdFlags The method by which to open the file.

  /// @param[in] VFSFlags The method by which to open the file.

  /// @return The file descriptor of the file that has been opened, or WASI

  /// error.

  static WasiExpect<INode> open(std::string Path, __wasi_oflags_t OpenFlags,

                                __wasi_fdflags_t FdFlags,

                                VFS::Flags VFSFlags) noexcept;

  /// Provide file advisory information on a file descriptor.

  ///

  /// Note: This is similar to `posix_fadvise` in POSIX.

  ///

  /// @param[in] Offset The offset within the file to which the advisory

  /// applies.

  /// @param[in] Len The length of the region to which the advisory applies.

  /// @param[in] Advice The advice.

  /// @return Nothing or WASI error

  WasiExpect<void> fdAdvise(__wasi_filesize_t Offset, __wasi_filesize_t Len,

                            __wasi_advice_t Advice) const noexcept;

  /// Force the allocation of space in a file.

  ///

  /// Note: This is similar to `posix_fallocate` in POSIX.

  ///

  /// @param[in] Offset The offset at which to start the allocation.

  /// @param[in] Len The length of the area that is allocated.

  /// @return Nothing or WASI error

  WasiExpect<void> fdAllocate(__wasi_filesize_t Offset,

                              __wasi_filesize_t Len) const noexcept;

  /// Synchronize the data of a file to disk.

  ///

  /// Note: This is similar to `fdatasync` in POSIX.

  ///

  /// @return Nothing or WASI error

  WasiExpect<void> fdDatasync() const noexcept;

  /// Get the attributes of a file descriptor.

  ///

  /// Note: This returns similar flags to `fsync(fd, F_GETFL)` in POSIX, as

  /// well

  ///

  /// as additional fields.

  /// @param[out] FdStat Result.

  /// @return Nothing or WASI error

  WasiExpect<void> fdFdstatGet(__wasi_fdstat_t &FdStat) const noexcept;

  /// Adjust the flags associated with a file descriptor.

  ///

  /// Note: This is similar to `fcntl(fd, F_SETFL, flags)` in POSIX.

  ///

  /// @param[in] FdFlags The desired values of the file descriptor flags.

  /// @return Nothing or WASI error

  WasiExpect<void> fdFdstatSetFlags(__wasi_fdflags_t FdFlags) const noexcept;

  /// Return the attributes of an open file.

  ///

  /// @param[out] Filestat Result.

  /// @return Nothing or WASI error

  WasiExpect<void> fdFilestatGet(__wasi_filestat_t &Filestat) const noexcept;

  /// Adjust the size of an open file. If this increases the file's size, the

  /// extra bytes are filled with zeros.

  ///

  /// Note: This is similar to `ftruncate` in POSIX.

  ///

  /// @param[in] Size The desired file size.

  /// @return Nothing or WASI error

  WasiExpect<void> fdFilestatSetSize(__wasi_filesize_t Size) const noexcept;

  /// Adjust the timestamps of an open file or directory.

  ///

  /// Note: This is similar to `futimens` in POSIX.

  ///

  /// @param[in] ATim The desired values of the data access timestamp.

  /// @param[in] MTim The desired values of the data modification timestamp.

  /// @param[in] FstFlags A bitmask indicating which timestamps to adjust.

  /// @return Nothing or WASI error

  WasiExpect<void>

  fdFilestatSetTimes(__wasi_timestamp_t ATim, __wasi_timestamp_t MTim,

                     __wasi_fstflags_t FstFlags) const noexcept;

  /// Read from a file descriptor, without using and updating the file

  /// descriptor's offset.

  ///

  /// Note: This is similar to `preadv` in POSIX.

  ///

  /// @param[in] IOVs List of scatter/gather vectors in which to store data.

  /// @param[in] Offset The offset within the file at which to read.

  /// @param[out] NRead The number of bytes read.

  /// @return Nothing or WASI error

  WasiExpect<void> fdPread(Span<Span<uint8_t>> IOVs, __wasi_filesize_t Offset,

                           __wasi_size_t &NRead) const noexcept;

  /// Write to a file descriptor, without using and updating the file

  /// descriptor's offset.

  ///

  /// Note: This is similar to `pwritev` in POSIX.

  ///

  /// @param[in] IOVs List of scatter/gather vectors from which to retrieve

  /// data.

  /// @param[in] Offset The offset within the file at which to write.

  /// @param[out] NWritten The number of bytes written.

  /// @return Nothing or WASI error

  WasiExpect<void> fdPwrite(Span<Span<const uint8_t>> IOVs,

                            __wasi_filesize_t Offset,

                            __wasi_size_t &NWritten) const noexcept;

  /// Read from a file descriptor.

  ///

  /// Note: This is similar to `readv` in POSIX.

  ///

  /// @param[in] IOVs List of scatter/gather vectors to which to store data.

  /// @param[out] NRead The number of bytes read.

  /// @return Nothing or WASI error

  WasiExpect<void> fdRead(Span<Span<uint8_t>> IOVs,

                          __wasi_size_t &NRead) const noexcept;

  /// Read directory entries from a directory.

  ///

  /// When successful, the contents of the output buffer consist of a sequence

  /// of directory entries. Each directory entry consists of a `dirent`

  /// object, followed by `dirent::d_namlen` bytes holding the name of the

  /// directory entry.

  ///

  /// This function fills the output buffer as much as possible,

  /// potentially truncating the last directory entry. This allows the caller

  /// to grow its read buffer size in case it's too small to fit a single

  /// large directory entry, or skip the oversized directory entry.

  ///

  /// @param[out] Buffer The buffer where directory entries are stored.

  /// @param[in] Cookie The location within the directory to start reading

  /// @param[out] Size The number of bytes stored in the read buffer. If less

  /// than the size of the read buffer, the end of the directory has been

  /// reached.

  /// @return Nothing or WASI error

  WasiExpect<void> fdReaddir(Span<uint8_t> Buffer, __wasi_dircookie_t Cookie,

                             __wasi_size_t &Size) noexcept;

  /// Move the offset of a file descriptor.

  ///

  /// Note: This is similar to `lseek` in POSIX.

  ///

  /// @param[in] Offset The number of bytes to move.

  /// @param[in] Whence The base from which the offset is relative.

  /// @param[out] Size The new offset of the file descriptor, relative to the

  /// start of the file.

  /// @return Nothing or WASI error

  WasiExpect<void> fdSeek(__wasi_filedelta_t Offset, __wasi_whence_t Whence,

                          __wasi_filesize_t &Size) const noexcept;

  /// Synchronize the data and metadata of a file to disk.

  ///

  /// Note: This is similar to `fsync` in POSIX.

  ///

  /// @return Nothing or WASI error

  WasiExpect<void> fdSync() const noexcept;

  /// Return the current offset of a file descriptor.

  ///

  /// Note: This is similar to `lseek(fd, 0, SEEK_CUR)` in POSIX.

  ///

  /// @param[out] Size The current offset of the file descriptor, relative to

  /// the start of the file.

  /// @return Nothing or WASI error

  WasiExpect<void> fdTell(__wasi_filesize_t &Size) const noexcept;

  /// Write to a file descriptor.

  ///

  /// Note: This is similar to `writev` in POSIX.

  ///

  /// @param[in] IOVs List of scatter/gather vectors from which to retrieve

  /// data.

  /// @param[out] NWritten The number of bytes written.

  /// @return Nothing or WASI error

  WasiExpect<void> fdWrite(Span<Span<const uint8_t>> IOVs,

                           __wasi_size_t &NWritten) const noexcept;

  /// Get the native handler.

  ///

  /// Note: Users should cast this native handler to corresponding types

  /// on different operating systems. E.g. int on POSIX or void * on Windows

  ///

  /// @return The native handler in uint64_t.

  WasiExpect<uint64_t> getNativeHandler() const noexcept;

  /// Create a directory.

  ///

  /// Note: This is similar to `mkdirat` in POSIX.

  ///

  /// @param[in] Path The path at which to create the directory.

  /// @return Nothing or WASI error

  WasiExpect<void> pathCreateDirectory(std::string Path) const noexcept;

  /// Return the attributes of a file or directory.

  ///

  /// Note: This is similar to `stat` in POSIX.

  ///

  /// @param[in] Path The path of the file or directory to inspect.

  /// @param[out] Filestat The buffer where the file's attributes are stored.

  /// @return Nothing or WASI error

  WasiExpect<void> pathFilestatGet(std::string Path,

                                   __wasi_filestat_t &Filestat) const noexcept;

  /// Adjust the timestamps of a file or directory.

  ///

  /// Note: This is similar to `utimensat` in POSIX.

  ///

  /// @param[in] Path The path of the file or directory to inspect.

  /// @param[in] ATim The desired values of the data access timestamp.

  /// @param[in] MTim The desired values of the data modification timestamp.

  /// @param[in] FstFlags A bitmask indicating which timestamps to adjust.

  /// @return Nothing or WASI error

  WasiExpect<void>

  pathFilestatSetTimes(std::string Path, __wasi_timestamp_t ATim,

                       __wasi_timestamp_t MTim,

                       __wasi_fstflags_t FstFlags) const noexcept;

  /// Create a hard link.

  ///

  /// Note: This is similar to `linkat` in POSIX.

  ///

  /// @param[in] Old The working directory at which the resolution of the old

  /// path starts.

  /// @param[in] OldPath The source path from which to link.

  /// @param[in] New The working directory at which the resolution of the new

  /// path starts.

  /// @param[in] NewPath The destination path at which to create the hard

  /// link. resolved.

  /// @return Nothing or WASI error

  static WasiExpect<void> pathLink(const INode &Old, std::string OldPath,

                                   const INode &New,

                                   std::string NewPath) noexcept;

  /// Open a file or directory.

  ///

  /// The returned file descriptor is not guaranteed to be the lowest-numbered

  /// file descriptor not currently open; it is randomized to prevent

  /// applications from depending on making assumptions about indexes, since

  /// this is error-prone in multi-threaded contexts. The returned file

  /// descriptor is guaranteed to be less than 2**31.

  ///

  /// Note: This is similar to `openat` in POSIX.

  ///

  /// @param[in] Path The relative path of the file or directory to open,

  /// relative to the `path_open::fd` directory.

  /// @param[in] OpenFlags The method by which to open the file.

  /// @param[in] FdFlags The method by which to open the file.

  /// @param[in] VFSFlags The method by which to open the file.

  /// @return The file descriptor of the file that has been opened, or WASI

  /// error.

  WasiExpect<INode> pathOpen(std::string Path, __wasi_oflags_t OpenFlags,

                             __wasi_fdflags_t FdFlags,

                             VFS::Flags VFSFlags) const noexcept;

  /// Read the contents of a symbolic link.

  ///

  /// Note: This is similar to `readlinkat` in POSIX.

  ///

  /// @param[in] Path The path of the symbolic link from which to read.

  /// @param[out] Buffer The buffer to which to write the contents of the

  /// symbolic link.

  /// @param[out] NRead The number of bytes read.

  /// @return Nothing or WASI error.

  WasiExpect<void> pathReadlink(std::string Path, Span<char> Buffer,

                                __wasi_size_t &NRead) const noexcept;

  /// Remove a directory.

  ///

  /// Return `errno::notempty` if the directory is not empty.

  ///

  /// Note: This is similar to `unlinkat(fd, path, AT_REMOVEDIR)` in POSIX.

  ///

  /// @param[in] Path The path to a directory to remove.

  /// @return Nothing or WASI error.

  WasiExpect<void> pathRemoveDirectory(std::string Path) const noexcept;

  /// Rename a file or directory.

  ///

  /// Note: This is similar to `renameat` in POSIX.

  ///

  /// @param[in] Old The working directory at which the resolution of the old

  /// path starts.

  /// @param[in] OldPath The source path of the file or directory to rename.

  /// @param[in] New The working directory at which the resolution of the new

  /// path starts.

  /// @param[in] NewPath The destination path to which to rename the file or

  /// directory.

  /// @return Nothing or WASI error.

  static WasiExpect<void> pathRename(const INode &Old, std::string OldPath,

                                     const INode &New,

                                     std::string NewPath) noexcept;

  /// Create a symbolic link.

  ///

  /// Note: This is similar to `symlinkat` in POSIX.

  ///

  /// @param[in] OldPath The contents of the symbolic link.

  /// @param[in] NewPath The destination path at which to create the symbolic

  /// link.

  /// @return Nothing or WASI error

  WasiExpect<void> pathSymlink(std::string OldPath,

                               std::string NewPath) const noexcept;

  /// Unlink a file.

  ///

  /// Return `errno::isdir` if the path refers to a directory.

  ///

  /// Note: This is similar to `unlinkat(fd, path, 0)` in POSIX.

  ///

  /// @param[in] Path The path to a file to unlink.

  /// @return Nothing or WASI error.

  WasiExpect<void> pathUnlinkFile(std::string Path) const noexcept;

  static WasiExpect<void>

  getAddrinfo(std::string_view NodeStr, std::string_view ServiceStr,

              const __wasi_addrinfo_t &Hint, uint32_t MaxResLength,

              Span<__wasi_addrinfo_t *> WasiAddrinfoArray,

              Span<__wasi_sockaddr_t *> WasiSockaddrArray,

              Span<char *> AiAddrSaDataArray, Span<char *> AiCanonnameArray,

              /*Out*/ __wasi_size_t &ResLength) noexcept;

  static WasiExpect<INode> sockOpen(__wasi_address_family_t SysDomain,

                                    __wasi_sock_type_t SockType) noexcept;

  WasiExpect<void> sockBind(__wasi_address_family_t AddressFamily,

                            Span<const uint8_t> Address,

                            uint16_t Port) noexcept;

  WasiExpect<void> sockListen(int32_t Backlog) noexcept;

  WasiExpect<INode> sockAccept(__wasi_fdflags_t FdFlags) noexcept;

  WasiExpect<void> sockConnect(__wasi_address_family_t AddressFamily,

                               Span<const uint8_t> Address,

                               uint16_t Port) noexcept;

  /// Receive a message from a socket.

  ///

  /// Note: This is similar to `recv` in POSIX, though it also supports

  /// reading the data into multiple buffers in the manner of `readv`.

  ///

  /// @param[in] RiData List of scatter/gather vectors to which to store data.

  /// @param[in] RiFlags Message flags.

  /// @param[out] NRead Return the number of bytes stored in RiData.

  /// @param[out] RoFlags Return message flags.

  /// @return Nothing or WASI error.

  WasiExpect<void> sockRecv(Span<Span<uint8_t>> RiData,

                            __wasi_riflags_t RiFlags, __wasi_size_t &NRead,

                            __wasi_roflags_t &RoFlags) const noexcept;

  /// Receive a message from a socket.

  ///

  /// Note: This is similar to `recvfrom` in POSIX, though it also supports

  /// reading the data into multiple buffers in the manner of `readv`.

  ///

  /// @param[in] RiData List of scatter/gather vectors to which to store data.

  /// @param[in] RiFlags Message flags.

  /// @param[out] AddressFamilyPtr The pointer to store address family.

  /// @param[out] Address The buffer to store address.

  /// @param[out] PortPtr The pointer to store port.

  /// @param[out] NRead Return the number of bytes stored in RiData.

  /// @param[out] RoFlags Return message flags.

  /// @return Nothing or WASI error.

  WasiExpect<void> sockRecvFrom(Span<Span<uint8_t>> RiData,

                                __wasi_riflags_t RiFlags,

                                __wasi_address_family_t *AddressFamilyPtr,

                                Span<uint8_t> Address, uint16_t *PortPtr,

                                __wasi_size_t &NRead,

                                __wasi_roflags_t &RoFlags) const noexcept;

  /// Send a message on a socket.

  ///

  /// Note: This is similar to `send` in POSIX, though it also supports

  /// writing the data from multiple buffers in the manner of `writev`.

  ///

  /// @param[in] SiData List of scatter/gather vectors to which to retrieve

  /// data.

  /// @param[in] SiFlags Message flags.

  /// @param[out] NWritten The number of bytes transmitted.

  /// @return Nothing or WASI error

  WasiExpect<void> sockSend(Span<Span<const uint8_t>> SiData,

                            __wasi_siflags_t SiFlags,

                            __wasi_size_t &NWritten) const noexcept;

  /// Send a message on a socket.

  ///

  /// Note: This is similar to `sendto` in POSIX, though it also supports

  /// writing the data from multiple buffers in the manner of `writev`.

  ///

  /// @param[in] SiData List of scatter/gather vectors to which to retrieve

  /// data.

  /// @param[in] SiFlags Message flags.

  /// @param[in] AddressFamily Address family of the target.

  /// @param[in] Address Address of the target.

  /// @param[in] Port Connected port.

  /// @param[out] NWritten The number of bytes transmitted.

  /// @return Nothing or WASI error

  WasiExpect<void> sockSendTo(Span<Span<const uint8_t>> SiData,

                              __wasi_siflags_t SiFlags,

                              __wasi_address_family_t AddressFamily,

                              Span<const uint8_t> Address, uint16_t Port,

                              __wasi_size_t &NWritten) const noexcept;

  /// Shut down socket send and receive channels.

  ///

  /// Note: This is similar to `shutdown` in POSIX.

  ///

  /// @param[in] SdFlags Which channels on the socket to shut down.

  /// @return Nothing or WASI error

  WasiExpect<void> sockShutdown(__wasi_sdflags_t SdFlags) const noexcept;

  WasiExpect<void> sockGetOpt(__wasi_sock_opt_level_t SockOptLevel,

                              __wasi_sock_opt_so_t SockOptName,

                              Span<uint8_t> &Flag) const noexcept;

  WasiExpect<void> sockSetOpt(__wasi_sock_opt_level_t SockOptLevel,

                              __wasi_sock_opt_so_t SockOptName,

                              Span<const uint8_t> Flag) const noexcept;

  WasiExpect<void> sockGetLocalAddr(__wasi_address_family_t *AddressFamilyPtr,

                                    Span<uint8_t> Address,

                                    uint16_t *PortPtr) const noexcept;

  WasiExpect<void> sockGetPeerAddr(__wasi_address_family_t *AddressFamilyPtr,

                                   Span<uint8_t> Address,

                                   uint16_t *PortPtr) const noexcept;

  /// File type.

  WasiExpect<__wasi_filetype_t> filetype() const noexcept;

  /// Check if this inode is a directory.

  bool isDirectory() const noexcept;

  /// Check if this inode is a symbolic link.

  bool isSymlink() const noexcept;

  /// File size.

  WasiExpect<__wasi_filesize_t> filesize() const noexcept;

  /// Check if current user has execute permission on this inode.

  bool canBrowse() const noexcept;

private:

  friend class Poller;

#if WASMEDGE_OS_LINUX || WASMEDGE_OS_MACOS

public:

  using FdHolder::FdHolder;

private:

  mutable std::optional<struct stat> Stat;

  DirHolder Dir;

  __wasi_filetype_t unsafeFiletype() const noexcept;

  WasiExpect<void> updateStat() const noexcept;

#elif WASMEDGE_OS_WINDOWS

public:

  using HandleHolder::HandleHolder;

private:

  __wasi_fdflags_t SavedFdFlags = {};

  uint8_t SavedVFSFlags = {};

  FindHolder Find;

#endif

};

class PollerContext;

class Poller

#if WASMEDGE_OS_LINUX || WASMEDGE_OS_MACOS

    : public FdHolder

#endif

{

public:

  Poller(const Poller &) = delete;

  Poller &operator=(const Poller &) = delete;

  Poller(Poller &&RHS) noexcept = default;

  Poller &operator=(Poller &&RHS) noexcept = default;

  Poller(PollerContext &) noexcept;

  /// Records an error for polling.

  ///

  /// @param[in] UserData User-provided value that may be attached to objects

  /// that is retained when extracted from the implementation.

  /// @param[in] Error Occurred while processing the subscription request.

  /// @param[in] Type The type of event that occurred

  /// additionally to coalesce with other events.

  void error(__wasi_userdata_t UserData, __wasi_errno_t Error,

             __wasi_eventtype_t Type) noexcept {

    assuming(Events.size() < WasiEvents.size());

    auto &Event = Events.emplace_back();

    Event.Valid = true;

    Event.userdata = UserData;

    Event.error = Error;

    Event.type = Type;

    switch (Type) {

    case __WASI_EVENTTYPE_FD_READ:

    case __WASI_EVENTTYPE_FD_WRITE:

      Event.fd_readwrite.nbytes = 0;

      Event.fd_readwrite.flags = static_cast<__wasi_eventrwflags_t>(0);

      break;

    default:

      break;

    }

  }

  /// Prepare for concurrently polling for the occurrence of a set of events.

  ///

  /// @param[in] Events The output buffer for events.

  WasiExpect<void> prepare(Span<__wasi_event_t> Events) noexcept;

  /// Concurrently poll for a time event.

  ///

  /// @param[in] Clock The clock against which to compare the timestamp.

  /// @param[in] Timeout The absolute or relative timestamp

  /// @param[in] Precision The amount of time that the implementation may wait

  /// @param[in] Flags Specifying whether the timeout is absolute or relative

  /// additionally to coalesce with other events.

  /// @param[in] UserData User-provided value that may be attached to objects

  /// that is retained when extracted from the implementation.

  void clock(__wasi_clockid_t Clock, __wasi_timestamp_t Timeout,

             __wasi_timestamp_t Precision, __wasi_subclockflags_t Flags,

             __wasi_userdata_t UserData) noexcept;

  void read(const INode &Fd, TriggerType Trigger,

            __wasi_userdata_t UserData) noexcept;

  void write(const INode &Fd, TriggerType Trigger,

             __wasi_userdata_t UserData) noexcept;

  void close(const INode &Fd) noexcept;

  /// Concurrently poll for events.

  void wait() noexcept;

  /// Return number of events.

  ///

  /// @return Number of event occurred

  __wasi_size_t result() const noexcept {

    assuming(Events.size() == WasiEvents.size());

    __wasi_size_t NEvent = 0;

    for (const auto &Event : Events) {

      if (Event.Valid) {

        WasiEvents[NEvent] = Event;

        ++NEvent;

      }

    }

    return NEvent;

  }

  /// Reset all status

  void reset() noexcept;

  bool ok() noexcept;

protected:

  std::reference_wrapper<PollerContext> Ctx;

private:

  Span<__wasi_event_t> WasiEvents;

  struct OptionalEvent : __wasi_event_t {

    bool Valid;

  };

  std::vector<OptionalEvent> Events;

#if WASMEDGE_OS_LINUX | WASMEDGE_OS_MACOS

  struct FdData {

    OptionalEvent *ReadEvent = nullptr;

    OptionalEvent *WriteEvent = nullptr;

  };

  std::unordered_map<int, FdData> FdDatas;

  std::unordered_map<int, FdData> OldFdDatas;

#endif

#if WASMEDGE_OS_WINDOWS

  struct SocketData {

    OptionalEvent *ReadEvent = nullptr;

    OptionalEvent *WriteEvent = nullptr;

  };

  std::unordered_map<winapi::SOCKET_, SocketData> SocketDatas;

  winapi::FD_SET_ ReadFds = {0, {}}, WriteFds = {0, {}};

#endif

#if WASMEDGE_OS_LINUX

  friend class PollerContext;

  struct Timer : public FdHolder {

    Timer(const Timer &) = delete;

    Timer &operator=(const Timer &) = delete;

    Timer(Timer &&RHS) noexcept = default;

    Timer &operator=(Timer &&RHS) noexcept = default;

    constexpr Timer(__wasi_clockid_t C) noexcept : Clock(C) {}

    WasiExpect<void> create() noexcept;

    WasiExpect<void> setTime(__wasi_timestamp_t Timeout,

                             __wasi_timestamp_t Precision,

                             __wasi_subclockflags_t Flags) noexcept;

    __wasi_clockid_t Clock;

#if !__GLIBC_PREREQ(2, 8)

    FdHolder Notify;

    TimerHolder TimerId;

#endif

  };

  std::vector<Timer> Timers;

  std::vector<struct epoll_event> EPollEvents;

#endif

#if WASMEDGE_OS_MACOS

  std::vector<struct kevent> KEvents;

  uint64_t NextTimerId = 0;

#endif

#if WASMEDGE_OS_WINDOWS

  std::unordered_map<winapi::HANDLE_, OptionalEvent *> ConsoleReadEvent;

  std::unordered_map<winapi::HANDLE_, OptionalEvent *> ConsoleWriteEvent;

  OptionalEvent *TimeoutEvent = nullptr;

  winapi::TIMEVAL_ MinimumTimeout;

#endif

};

class PollerContext {

#if WASMEDGE_OS_LINUX

public:

  WasiExpect<Poller::Timer> acquireTimer(__wasi_clockid_t Clock) noexcept;

  void releaseTimer(Poller::Timer &&) noexcept;

private:

  std::mutex TimerMutex; ///< Protect TimerPool

  std::unordered_map<__wasi_clockid_t, std::vector<Poller::Timer>> TimerPool;

#else

#endif

};

} // namespace WASI

} // namespace Host

} // namespace WasmEdge