io

type File interface {
	fs.File
	io.ReadSeekCloser
	io.ReaderAt
}

type FileWriter interface {
	io.WriteCloser
	io.ReaderFrom
}

type IO interface {
	// Open opens the named file.
	//
	// When Open returns an error, it should be of type *PathError
	// with the Op field set to "open", the Path field set to name,
	// and the Err field describing the problem.
	//
	// Open should reject attempts to open names that do not satisfy
	// fs.ValidPath(name), returning a *PathError with Err set to
	// ErrInvalid or ErrNotExist.
	Open(name string) (File, error)

	// Remove removes the named file or (empty) directory.
	//
	// If there is an error, it will be of type *PathError.
	Remove(name string) error
}

type KeyExtractor func(path string) (string, error)

type LocalFS struct{}

type ReadDirFile interface {
	File

	// ReadDir read the contents of the directory and returns a slice
	// of up to n DirEntry values in directory order. Subsequent calls
	// on the same file will yield further DirEntry values.
	//
	// If n > 0, ReadDir returns at most n DirEntry structures. In this
	// case, if ReadDir returns an empty slice, it will return a non-nil
	// error explaining why.
	//
	// At the end of a directory, the error is io.EOF. (ReadDir must return
	// io.EOF itself, not an error wrapping io.EOF.)
	//
	// If n <= 0, ReadDir returns all the DirEntry values from the directory
	// in a single slice. In this case, if ReadDir succeeds (reads all the way
	// to the end of the directory), it returns the slice and a nil error.
	// If it encounters an error before the end of the directory, ReadDir
	// returns the DirEntry list read until that point and a non-nil error.
	ReadDir(n int) ([]fs.DirEntry, error)
}

type ReadFileIO interface {
	IO

	// ReadFile reads the named file and returns its contents.
	// A successful call returns a nil error, not io.EOF.
	// (Because ReadFile reads the whole file, the expected EOF
	// from the final Read is not treated as an error to be reported.)
	//
	// The caller is permitted to modify the returned byte slice.
	// This method should return a copy of the underlying data.
	ReadFile(name string) ([]byte, error)
}

type WriteFileIO interface {
	IO

	// Create attempts to create the named file and return a writer
	// for it.
	Create(name string) (FileWriter, error)

	// WriteFile writes p to the named file.
	WriteFile(name string, p []byte) error
}