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package afero
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import (
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	"io/fs"
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	"os"
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	"path/filepath"
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	"runtime"
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	"strings"
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	"time"
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)
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var (
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	_ Lstater        = (*BasePathFs)(nil)
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	_ fs.ReadDirFile = (*BasePathFile)(nil)
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)
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// The BasePathFs restricts all operations to a given path within an Fs.
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// The given file name to the operations on this Fs will be prepended with
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// the base path before calling the base Fs.
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// Any file name (after filepath.Clean()) outside this base path will be
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// treated as non existing file.
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//
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// Note that it does not clean the error messages on return, so you may
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// reveal the real path on errors.
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type BasePathFs struct {
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	source Fs
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	path   string
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}
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type BasePathFile struct {
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	File
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	path string
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}
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func (f *BasePathFile) Name() string {
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	sourcename := f.File.Name()
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	return strings.TrimPrefix(sourcename, filepath.Clean(f.path))
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}
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func (f *BasePathFile) ReadDir(n int) ([]fs.DirEntry, error) {
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	if rdf, ok := f.File.(fs.ReadDirFile); ok {
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		return rdf.ReadDir(n)
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	}
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	return readDirFile{f.File}.ReadDir(n)
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}
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func NewBasePathFs(source Fs, path string) Fs {
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	return &BasePathFs{source: source, path: path}
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}
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// on a file outside the base path it returns the given file name and an error,
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// else the given file with the base path prepended
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func (b *BasePathFs) RealPath(name string) (path string, err error) {
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	if err := validateBasePathName(name); err != nil {
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		return name, err
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	}
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	bpath := filepath.Clean(b.path)
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	path = filepath.Clean(filepath.Join(bpath, name))
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	if !strings.HasPrefix(path, bpath) {
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		return name, os.ErrNotExist
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	}
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	return path, nil
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}
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func validateBasePathName(name string) error {
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	if runtime.GOOS != "windows" {
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		// Not much to do here;
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		// the virtual file paths all look absolute on *nix.
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		return nil
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	}
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	// On Windows a common mistake would be to provide an absolute OS path
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	// We could strip out the base part, but that would not be very portable.
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	if filepath.IsAbs(name) {
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		return os.ErrNotExist
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	}
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	return nil
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}
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func (b *BasePathFs) Chtimes(name string, atime, mtime time.Time) (err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return &os.PathError{Op: "chtimes", Path: name, Err: err}
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	}
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	return b.source.Chtimes(name, atime, mtime)
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}
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func (b *BasePathFs) Chmod(name string, mode os.FileMode) (err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return &os.PathError{Op: "chmod", Path: name, Err: err}
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	}
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	return b.source.Chmod(name, mode)
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}
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func (b *BasePathFs) Chown(name string, uid, gid int) (err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return &os.PathError{Op: "chown", Path: name, Err: err}
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	}
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	return b.source.Chown(name, uid, gid)
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}
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func (b *BasePathFs) Name() string {
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	return "BasePathFs"
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}
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func (b *BasePathFs) Stat(name string) (fi os.FileInfo, err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return nil, &os.PathError{Op: "stat", Path: name, Err: err}
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	}
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	return b.source.Stat(name)
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}
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func (b *BasePathFs) Rename(oldname, newname string) (err error) {
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	if oldname, err = b.RealPath(oldname); err != nil {
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		return &os.PathError{Op: "rename", Path: oldname, Err: err}
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	}
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	if newname, err = b.RealPath(newname); err != nil {
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		return &os.PathError{Op: "rename", Path: newname, Err: err}
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	}
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	return b.source.Rename(oldname, newname)
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}
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func (b *BasePathFs) RemoveAll(name string) (err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return &os.PathError{Op: "remove_all", Path: name, Err: err}
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	}
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	return b.source.RemoveAll(name)
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}
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func (b *BasePathFs) Remove(name string) (err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return &os.PathError{Op: "remove", Path: name, Err: err}
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	}
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	return b.source.Remove(name)
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}
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func (b *BasePathFs) OpenFile(name string, flag int, mode os.FileMode) (f File, err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return nil, &os.PathError{Op: "openfile", Path: name, Err: err}
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	}
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	sourcef, err := b.source.OpenFile(name, flag, mode)
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	if err != nil {
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		return nil, err
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	}
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	return &BasePathFile{sourcef, b.path}, nil
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}
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func (b *BasePathFs) Open(name string) (f File, err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return nil, &os.PathError{Op: "open", Path: name, Err: err}
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	}
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	sourcef, err := b.source.Open(name)
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	if err != nil {
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		return nil, err
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	}
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	return &BasePathFile{File: sourcef, path: b.path}, nil
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}
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func (b *BasePathFs) Mkdir(name string, mode os.FileMode) (err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return &os.PathError{Op: "mkdir", Path: name, Err: err}
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	}
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	return b.source.Mkdir(name, mode)
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}
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func (b *BasePathFs) MkdirAll(name string, mode os.FileMode) (err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return &os.PathError{Op: "mkdir", Path: name, Err: err}
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	}
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	return b.source.MkdirAll(name, mode)
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}
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func (b *BasePathFs) Create(name string) (f File, err error) {
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	if name, err = b.RealPath(name); err != nil {
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		return nil, &os.PathError{Op: "create", Path: name, Err: err}
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	}
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	sourcef, err := b.source.Create(name)
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	if err != nil {
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		return nil, err
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	}
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	return &BasePathFile{File: sourcef, path: b.path}, nil
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}
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func (b *BasePathFs) LstatIfPossible(name string) (os.FileInfo, bool, error) {
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	name, err := b.RealPath(name)
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	if err != nil {
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		return nil, false, &os.PathError{Op: "lstat", Path: name, Err: err}
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	}
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	if lstater, ok := b.source.(Lstater); ok {
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		return lstater.LstatIfPossible(name)
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	}
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	fi, err := b.source.Stat(name)
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	return fi, false, err
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}
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func (b *BasePathFs) SymlinkIfPossible(oldname, newname string) error {
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	oldname, err := b.RealPath(oldname)
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	if err != nil {
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		return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: err}
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	}
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	newname, err = b.RealPath(newname)
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	if err != nil {
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		return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: err}
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	}
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	if linker, ok := b.source.(Linker); ok {
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		return linker.SymlinkIfPossible(oldname, newname)
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	}
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	return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: ErrNoSymlink}
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}
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func (b *BasePathFs) ReadlinkIfPossible(name string) (string, error) {
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	name, err := b.RealPath(name)
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	if err != nil {
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		return "", &os.PathError{Op: "readlink", Path: name, Err: err}
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	}
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	if reader, ok := b.source.(LinkReader); ok {
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		return reader.ReadlinkIfPossible(name)
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	}
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	return "", &os.PathError{Op: "readlink", Path: name, Err: ErrNoReadlink}
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}
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