type FileSystem interface {
	// User returns the user that the ClientImpl is acting under. This is either the
	// current system user or the kerberos principal.
	User(ctx context.Context) string
	// ReadFile reads the file named by filename and returns the contents.
	ReadFile(ctx context.Context, filename string) ([]byte, error)
	// CopyToLocal copies the HDFS file specified by src to the local file at dst.
	// If dst already exists, it will be overwritten.
	CopyToLocal(ctx context.Context, src string, dst string) error
	// CopyToRemote copies the local file specified by src to the HDFS file at dst.
	CopyToRemote(ctx context.Context, src string, dst string) error
	// Close terminates all underlying socket connections to remote server.
	Close(ctx context.Context) error
	// GetContentSummary returns a ContentSummary representing the named file or
	// directory. The summary contains information about the entire tree rooted
	// in the named file; for instance, it can return the total size of all
	GetContentSummary(ctx context.Context, name string) (*ContentSummary, error)
	// Open returns an FileReaderImpl which can be used for reading.
	Open(ctx context.Context, name string) (FileReader, error)
	// Create opens a new file in HDFS with the default replication, block size,
	// and permissions (0644), and returns an io.WriteCloser for writing
	// to it. Because of the way that HDFS writes are buffered and acknowledged
	// asynchronously, it is very important that Close is called after all data has
	// been written.
	Create(ctx context.Context, name string) (FileWriter, error)
	// CreateFile opens a new file in HDFS with the given replication, block size,
	// and permissions, and returns an io.WriteCloser for writing to it. Because of
	// the way that HDFS writes are buffered and acknowledged asynchronously, it is
	// very important that Close is called after all data has been written.
	CreateFile(ctx context.Context, name string, replication int, blockSize int64, perm os.FileMode) (FileWriter, error)
	// Append opens an existing file in HDFS and returns an io.WriteCloser for
	// writing to it. Because of the way that HDFS writes are buffered and
	// acknowledged asynchronously, it is very important that Close is called after
	// all data has been written.
	Append(ctx context.Context, name string) (FileWriter, error)
	// CreateEmptyFile creates a empty file at the given name, with the
	// permissions 0644.
	CreateEmptyFile(ctx context.Context, name string) error
	// Mkdir creates a new directory with the specified name and permission bits.
	Mkdir(ctx context.Context, dirname string, perm os.FileMode) error
	// MkdirAll creates a directory for dirname, along with any necessary parents,
	// and returns nil, or else returns an error. The permission bits perm are used
	// for all directories that MkdirAll creates. If dirname is already a directory,
	// MkdirAll does nothing and returns nil.
	MkdirAll(ctx context.Context, dirname string, perm os.FileMode) error
	// Chmod changes the mode of the named file to mode.
	Chmod(ctx context.Context, name string, perm os.FileMode) error
	// Chown changes the user and group of the file. Unlike os.Chown, this takes
	// a string username and group (since that's what HDFS uses.)
	//
	// If an empty string is passed for user or group, that field will not be
	// changed remotely.
	Chown(ctx context.Context, name string, user, group string) error

	// Chtimes changes the access and modification times of the named file.
	Chtimes(ctx context.Context, name string, atime time.Time, mtime time.Time) error
	// ReadDir reads the directory named by dirname and returns a list of sorted
	// directory entries.
	//
	// The os.FileInfo values returned will not have block location attached to
	// the struct returned by Sys().
	ReadDir(ctx context.Context, dirname string) ([]os.FileInfo, error)
	// Remove removes the named file or (empty) directory.
	Remove(ctx context.Context, name string) error
	// RemoveAll removes path and any children it contains. It removes everything it
	// can but returns the first error it encounters. If the path does not exist,
	// RemoveAll returns nil (no error).
	RemoveAll(ctx context.Context, name string) error
	// Rename renames (moves) a file.
	Rename(ctx context.Context, oldpath, newpath string) error
	// RenameWithOverwrite renames (moves) a file. Overwrite option is taken as input.
	RenameWithOverwriteOption(ctx context.Context, oldpath, newpath string, overwrite bool) error
	// Stat returns an os.FileInfo describing the named file or directory.
	Stat(ctx context.Context, name string) (os.FileInfo, error)
	StatFs(ctx context.Context) (FsInfo, error)
	// Walk walks the file tree rooted at root, calling walkFn for each file or
	// directory in the tree, including root.All errors that arise visiting files
	// and directories are filtered by walkFn. The files are walked in lexical
	// order, which makes the output deterministic but means that for very large
	// directories Walk can be inefficient. Walk does not follow symbolic links.
	Walk(ctx context.Context, root string, walkFn filepath.WalkFunc) error
}