/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef INCLUDE_PERFETTO_EXT_BASE_FILE_UTILS_H_
#define INCLUDE_PERFETTO_EXT_BASE_FILE_UTILS_H_

#include <fcntl.h>  // For mode_t & O_RDONLY/RDWR. Exists also on Windows.
#include <stddef.h>

#include <functional>
#include <memory>
#include <optional>
#include <string>
#include <vector>

#include "perfetto/base/build_config.h"
#include "perfetto/base/export.h"
#include "perfetto/base/status.h"
#include "perfetto/ext/base/scoped_file.h"
#include "perfetto/ext/base/sys_types.h"

namespace perfetto {
namespace base {

class TaskRunner;

#if PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
using FileOpenMode = int;
inline constexpr char kDevNull[] = "NUL";
inline constexpr char kFopenReadFlag[] = "r";
#else
using FileOpenMode = mode_t;
inline constexpr char kDevNull[] = "/dev/null";
inline constexpr char kFopenReadFlag[] = "re";
#endif

constexpr FileOpenMode kFileModeInvalid = static_cast<FileOpenMode>(-1);

// Cross-platform variant of ReadFileDescriptor() that takes a PlatformHandle.
// On Windows normalizes ERROR_BROKEN_PIPE to EOF so behavior matches POSIX.
bool ReadPlatformHandle(PlatformHandle, std::string* out);

// Reads from |fd|, appending what is currently available into |*out|.
// Returns:
//  True: EOF reached (all writers of |fd| have closed their end).
//  False: read error. On a non-blocking |fd| this includes EAGAIN (no data
//    currently available but writers are still alive); callers can check
//    IsAgain(errno) and retry on the next readability notification.
bool ReadFileDescriptor(int fd, std::string* out);

// Convenience wrapper around ReadFileDescriptor() that takes a FILE*.
bool ReadFileStream(FILE* f, std::string* out);

// Opens |path| read-only and reads its contents into |*out|.
// Returns false if the file cannot be opened.
bool ReadFile(const std::string& path, std::string* out);

// A wrapper around read(2). It deals with Linux vs Windows includes. It also
// deals with handling EINTR. Has the same semantics of UNIX's read(2).
ssize_t Read(int fd, void* dst, size_t dst_size);

// Call write until all data is written or an error is detected.
//
// man 2 write:
//   If a write() is interrupted by a signal handler before any bytes are
//   written, then the call fails with the error EINTR; if it is
//   interrupted after at least one byte has been written, the call
//   succeeds, and returns the number of bytes written.
ssize_t WriteAll(int fd, const void* buf, size_t count);

// Copies all data from |fd_in| to |fd_out|. Saves the offset of |fd_in|,
// rewinds it to the beginning, copies the content, and restores the offset.
// |fd_in| can't be a pipe, socket of FIFO.
base::Status CopyFileContents(int fd_in, int fd_out);

ssize_t WriteAllHandle(PlatformHandle, const void* buf, size_t count);

ScopedFile OpenFile(const std::string& path,
                    int flags,
                    FileOpenMode = kFileModeInvalid);
ScopedFstream OpenFstream(const std::string& path, const std::string& mode);

// This is an alias for close(). It's to avoid leaking windows.h in headers.
// Exported because ScopedFile is used in the /include/ext API by Chromium
// component builds.
int PERFETTO_EXPORT_COMPONENT CloseFile(int fd);

bool FlushFile(int fd);

// Returns true if mkdir succeeds, false if it fails (see errno in that case).
bool Mkdir(const std::string& path);

// Calls rmdir() on UNIX, _rmdir() on Windows.
bool Rmdir(const std::string& path);

// Wrapper around access(path, F_OK).
bool FileExists(const std::string& path);

// Gets the extension for a filename. If the file has two extensions, returns
// only the last one (foo.pb.gz => .gz). Returns empty string if there is no
// extension.
std::string GetFileExtension(const std::string& filename);

// Returns the basename component of a path (the final component after the last
// directory separator). Behaves like man 2 basename, but works with both '/'
// and '\' separators for cross-platform compatibility.
// Examples:
//   Basename("/usr/bin/ls") => "ls"
//   Basename("/usr/bin/") => "bin"
//   Basename("/") => "/"
//   Basename("foo") => "foo"
//   Basename("") => "."
//   Basename("C:\\Windows\\System32") => "System32"
std::string Basename(const std::string& path);

// Returns the directory component of a path (everything up to but not
// including the final component). Behaves like man 2 dirname, but works with
// both '/' and '\' separators for cross-platform compatibility.
// Examples:
//   Dirname("/usr/bin/ls") => "/usr/bin"
//   Dirname("/usr/bin") => "/usr"
//   Dirname("/") => "/"
//   Dirname("foo") => "."
//   Dirname("") => "."
//   Dirname("C:\\Windows\\System32") => "C:\\Windows"
std::string Dirname(const std::string& path);

// Puts the path to all files under |dir_path| in |output|, recursively walking
// subdirectories. File paths are relative to |dir_path|. Only files are
// included, not directories. Path separator is always '/', even on windows (not
// '\').
base::Status ListFilesRecursive(const std::string& dir_path,
                                std::vector<std::string>& output);

// Lists immediate subdirectories in |dir_path| (non-recursive). Directory names
// are relative to |dir_path| and do not include the path separator. Returns
// only directories, not files. Works on both Unix and Windows.
base::Status ListDirectories(const std::string& dir_path,
                             std::vector<std::string>& output);

// Sets |path|'s owner group to |group_name| and permission mode bits to
// |mode_bits|.
base::Status SetFilePermissions(const std::string& path,
                                const std::string& group_name,
                                const std::string& mode_bits);

// Returns the size of the file located at |path|, or nullopt in case of error.
std::optional<uint64_t> GetFileSize(const std::string& path);

// Returns the size of the open file |fd|, or nullopt in case of error.
std::optional<uint64_t> GetFileSize(PlatformHandle fd);

// This class uses inotify (on Linux/Android) to watch for the creation of
// files in the filesystem. When the specified file is created, it triggers a
// callback function.
// Destroying the returned unique_ptr will automatically unregister the watch.
//
// Note: This only works with filesystem paths (not abstract sockets or other
// special file types).
// It's only supported on Linux and Android, it's a no-op (returns nullptr) on
// other platforms.
//
// Usage:
//   auto watch = LinuxFileWatch::WatchFileCreation(
//       task_runner, "/tmp/my_file", []() {
//         // Called when /tmp/my_file is created
//       });
class LinuxFileWatch {
 public:
  // Creates a watcher for file creation. Returns nullptr if the path is not a
  // valid filesystem path or if the platform doesn't support inotify. The
  // callback will be invoked on the provided TaskRunner when the file is
  // created.
  static std::unique_ptr<LinuxFileWatch> WatchFileCreation(
      TaskRunner*,
      const char* path,
      std::function<void()> callback);

  virtual ~LinuxFileWatch();

 protected:
  LinuxFileWatch() = default;
};

}  // namespace base
}  // namespace perfetto

#endif  // INCLUDE_PERFETTO_EXT_BASE_FILE_UTILS_H_
