#pragma once

#include <bitset>

#include <cstdint>

#include <memory>

#include <string>

#include "envoy/api/io_error.h"

#include "envoy/common/platform.h"

#include "envoy/common/pure.h"

#include "envoy/common/time.h"

#include "absl/status/statusor.h"

#include "absl/strings/string_view.h"

#include "absl/types/optional.h"

namespace Envoy {

namespace Filesystem {

using FlagSet = std::bitset<5>;

enum class DestinationType { File, Stderr, Stdout, TmpFile };

enum class FileType { Regular, Directory, Other };

struct FileInfo {

  const std::string name_;

  // the size of the file in bytes, or `nullopt` if the size could not be determined

  //         (e.g. for directories, or windows symlinks.)

  const absl::optional<uint64_t> size_;

  // Note that if the file represented by name_ is a symlink, type_ will be the file type of the

  // target. For example, if name_ is a symlink to a directory, its file type will be Directory.

  // A broken symlink on posix will have `FileType::Regular`.

  const FileType file_type_;

  const absl::optional<SystemTime> time_created_;

  const absl::optional<SystemTime> time_last_accessed_;

  const absl::optional<SystemTime> time_last_modified_;

};

/**

 * Abstraction for a basic file on disk.

 */

class File {

public:

  enum Operation {

    // Open a file for reading.

    Read,

    // Open a file for writing. The file will be truncated if neither Append nor

    // KeepExisting is set.

    Write,

    // Create the file if it does not already exist

    Create,

    // If writing, append to the file rather than writing to the beginning and

    // truncating after write.

    Append,

    // To open for write, without appending, and without truncating, add the

    // KeepExistingData flag. It is especially important to set this flag if

    // using pwrite, as the Windows implementation of truncation will interact

    // poorly with pwrite.

    KeepExistingData,

  };

  /**

   * Open the file with Flag

   * The file will be closed when this object is destructed

   *

   * @return bool whether the open succeeded

   */

  virtual Api::IoCallBoolResult open(FlagSet flags) PURE;

  /**

   * Write the buffer to the file. The file must be explicitly opened before writing.

   *

   * @return ssize_t number of bytes written, or -1 for failure

   */

  virtual Api::IoCallSizeResult write(absl::string_view buffer) PURE;

  /**

   * Get additional details about the file. May or may not require a file system operation.

   *

   * @return FileInfo the file info.

   */

  virtual Api::IoCallResult<FileInfo> info() PURE;

  /**

   * Close the file.

   *

   * @return bool whether the close succeeded

   */

  virtual Api::IoCallBoolResult close() PURE;

  /**

   * Read a chunk of data from the file to a buffer. The file must be explicitly opened

   * before reading.

   * @param buf The buffer to copy the data into.

   * @param count The maximum number of bytes to read.

   * @param offset The offset in the file at which to start reading.

   * @return ssize_t number of bytes read, or -1 for failure.

   */

  virtual Api::IoCallSizeResult pread(void* buf, uint64_t count, uint64_t offset) PURE;

  /**

   * Write a chunk of data from a buffer to the file. The file must be explicitly opened

   * before writing.

   * @param buf The buffer to read the data from.

   * @param count The maximum number of bytes to write.

   * @param offset The offset in the file at which to start writing.

   * @return ssize_t number of bytes written, or -1 for failure.

   */

  virtual Api::IoCallSizeResult pwrite(const void* buf, uint64_t count, uint64_t offset) PURE;

  /**

   * @return bool is the file open

   */

  virtual bool isOpen() const PURE;

  /**

   * @return string the file path

   */

  virtual absl::string_view path() const PURE;

  /**

   * @return the type of the destination

   */

  virtual DestinationType destinationType() const PURE;

};

using FilePtr = std::unique_ptr<File>;

/**

 * Contains the result of splitting the file name and its parent directory from

 * a given file path.

 */

struct PathSplitResult {

  absl::string_view directory_;

  absl::string_view file_;

};

/**

 * Contains the file type and the path.

 */

struct FilePathAndType {

  FilePathAndType() = default;

  FilePathAndType(DestinationType file_type, absl::string_view path)

  DestinationType file_type_;

  std::string path_;

};

/**

 * Abstraction for some basic filesystem operations

 */

class Instance {

public:

  /**

   *  @param file_info The path and the type of the File

   *  @return a FilePtr. The file is not opened.

   */

  virtual FilePtr createFile(const FilePathAndType& file_info) PURE;

  /**

   * @return bool whether a file exists on disk and can be opened for read.

   */

  virtual bool fileExists(const std::string& path) PURE;

  /**

   * @return FileInfo containing information about the file, or an error status.

   */

  virtual Api::IoCallResult<FileInfo> stat(absl::string_view path) PURE;

  /**

   * Attempts to create the given path, recursively if necessary.

   * @return bool true if one or more directories was created and the path exists,

   *         false if the path already existed, an error status if the path does

   *         not exist after the call.

   */

  virtual Api::IoCallBoolResult createPath(absl::string_view path) PURE;

  /**

   * @return bool whether a directory exists on disk and can be opened for read.

   */

  virtual bool directoryExists(const std::string& path) PURE;

  /**

   * @return ssize_t the size in bytes of the specified file, or -1 if the file size

   *                 cannot be determined for any reason, including without limitation

   *                 the non-existence of the file.

   */

  virtual ssize_t fileSize(const std::string& path) PURE;

  /**

   * @return full file content as a string or an error if the file can not be read.

   * Be aware, this is not most highly performing file reading method.

   */

  virtual absl::StatusOr<std::string> fileReadToEnd(const std::string& path) PURE;

  /**

   * @path file path to split

   * @return PathSplitResult containing the parent directory of the input path and the file name or

   * an error status.

   */

  virtual absl::StatusOr<PathSplitResult> splitPathFromFilename(absl::string_view path) PURE;

  /**

   * Determine if the path is on a list of paths Envoy will refuse to access. This

   * is a basic sanity check for users, denying some clearly bad paths. Paths

   * may still be problematic (e.g. indirectly leading to /dev/mem) even if this

   * returns false, it is up to the user to validate that supplied paths are

   * valid.

   * @param path some filesystem path.

   * @return is the path on the deny list?

   */

  virtual bool illegalPath(const std::string& path) PURE;

};

using InstancePtr = std::unique_ptr<Instance>;

struct DirectoryEntry {

  // name_ is the name of the file in the directory, not including the directory path itself

  // For example, if we have directory a/b containing file c, name_ will be c

  std::string name_;

  // Note that if the file represented by name_ is a symlink, type_ will be the file type of the

  // target. For example, if name_ is a symlink to a directory, its file type will be Directory.

  FileType type_;

  // The file size in bytes for regular files. nullopt for FileType::Directory and FileType::Other,

  // and, on Windows, also nullopt for symlinks, and on Linux nullopt for broken symlinks.

  absl::optional<uint64_t> size_bytes_;

};

class DirectoryIteratorImpl;

// Failures during this iteration will be silent; check status() after initialization

// and after each increment, if error-handling is desired.

class DirectoryIterator {

public:

  virtual DirectoryIteratorImpl& operator++() PURE;

protected:

  DirectoryEntry entry_;

  absl::Status status_;

};

} // namespace Filesystem

} // namespace Envoy