package fs

import (
	"io"
	"os"
	"path/filepath"
	"runtime"
	"strings"
)

// File is an open file on a file system.
type File interface {
	io.Reader
	io.Writer
	io.Closer

	Fd() uintptr
	Readdirnames(n int) ([]string, error)
	Readdir(int) ([]os.FileInfo, error)
	Seek(int64, int) (int64, error)
	Stat() (os.FileInfo, error)
}

// fixpath returns an absolute path on windows, so restic can open long file names.
func fixpath(name string) string {
	if runtime.GOOS == "windows" {
		abspath, err := filepath.Abs(name)
		if err == nil {
			// Check if \\?\UNC\ already exists.
			if strings.HasPrefix(abspath, `\\?\UNC\`) {
				return abspath
			}
			// Check if \\?\ already exists.
			if strings.HasPrefix(abspath, `\\?\`) {
				return abspath
			}
			// Check if path starts with \\.
			if strings.HasPrefix(abspath, `\\`) {
				return strings.Replace(abspath, `\\`, `\\?\UNC\`, 1)
			}
			// Normal path.
			return `\\?\` + abspath
		}
	}
	return name
}

// Chmod changes the mode of the named file to mode.
func Chmod(name string, mode os.FileMode) error {
	return os.Chmod(fixpath(name), mode)
}

// Mkdir creates a new directory with the specified name and permission bits.  If there is an error, it will be of type
// *PathError.
func Mkdir(name string, perm os.FileMode) error {
	return os.Mkdir(fixpath(name), perm)
}

// MkdirAll creates a directory named path, 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 path is already a directory,
// MkdirAll does nothing and returns nil.
func MkdirAll(path string, perm os.FileMode) error {
	return os.MkdirAll(fixpath(path), perm)
}

// Readlink returns the destination of the named symbolic link.  If there is an error, it will be of type *PathError.
func Readlink(name string) (string, error) {
	return os.Readlink(fixpath(name))
}

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

// 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).
func RemoveAll(path string) error {
	return os.RemoveAll(fixpath(path))
}

// Rename renames (moves) oldpath to newpath.  If newpath already exists, Rename replaces it.  OS-specific restrictions
// may apply when oldpath and newpath are in different directories.  If there is an error, it will be of type
// *LinkError.
func Rename(oldpath, newpath string) error {
	return os.Rename(fixpath(oldpath), fixpath(newpath))
}

// Symlink creates newname as a symbolic link to oldname.  If there is an error, it will be of type *LinkError.
func Symlink(oldname, newname string) error {
	return os.Symlink(fixpath(oldname), fixpath(newname))
}

// Stat returns a FileInfo structure describing the named file.  If there is an error, it will be of type *PathError.
func Stat(name string) (os.FileInfo, error) {
	return os.Stat(fixpath(name))
}

// Lstat returns the FileInfo structure describing the named file.  If the file is a symbolic link, the returned
// FileInfo describes the symbolic link.  Lstat makes no attempt to follow the link.  If there is an error, it will be
// of type *PathError.
func Lstat(name string) (os.FileInfo, error) {
	return os.Lstat(fixpath(name))
}

// Create creates the named file with mode 0666 (before umask), truncating it if it already exists. If successful,
// methods on the returned File can be used for I/O; the associated file descriptor has mode O_RDWR.  If there is an
// error, it will be of type *PathError.
func Create(name string) (*os.File, error) {
	return os.Create(fixpath(name))
}

// OpenFile is the generalized open call; most users will use Open or Create instead.  It opens the named file with
// specified flag (O_RDONLY etc.) and perm, (0666 etc.) if applicable.  If successful, methods on the returned File can
// be used for I/O.  If there is an error, it will be of type *PathError.
func OpenFile(name string, flag int, perm os.FileMode) (*os.File, error) {
	return os.OpenFile(fixpath(name), flag, perm)
}

// 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.
func Walk(root string, walkFn filepath.WalkFunc) error {
	return filepath.Walk(fixpath(root), walkFn)
}