package afero

import (
	"os"
	"path/filepath"
	"strings"
	"time"
)

type BasePathFs struct {
	base Fs
	path string
}

// The BasePathFs restricts all operations to a given path within an Fs.
// The given file name to the operations on this Fs will be prepended with
// the base path before calling the base Fs.
// Any file name (after filepath.Clean()) outside this base path will be
// treated as non existing file.
//
// Note that it does not clean the error messages on return, so you may
// reveal the real path on errors.
func NewBasePathFs(base Fs, path string) FilterFs {
	return &BasePathFs{base: base, path: filepath.Clean(path) + string(os.PathSeparator)}
}

func (b *BasePathFs) AddFilter(fs FilterFs) {
	fs.SetSource(b.base)
	b.base = fs
}

func (b *BasePathFs) SetSource(fs Fs) {
	b.base = fs
}

// on a file outside the base path it returns the given file name and an error,
// else the given file with the base path prepended
func (b *BasePathFs) RealPath(name string) (path string, err error) {
	path = filepath.Clean(filepath.Join(b.path, name))
	if !strings.HasPrefix(path, b.path) {
		return name, os.ErrNotExist
	}
	return path, nil
}

func (b *BasePathFs) Chtimes(name string, atime, mtime time.Time) (err error) {
	if name, err = b.RealPath(name); err != nil {
		return &os.PathError{"chtimes", name, err}
	}
	return b.base.Chtimes(name, atime, mtime)
}

func (b *BasePathFs) Chmod(name string, mode os.FileMode) (err error) {
	if name, err = b.RealPath(name); err != nil {
		return &os.PathError{"chmod", name, err}
	}
	return b.base.Chmod(name, mode)
}

func (b *BasePathFs) Name() string {
	return "BasePathFs"
}

func (b *BasePathFs) Stat(name string) (fi os.FileInfo, err error) {
	if name, err = b.RealPath(name); err != nil {
		return nil, &os.PathError{"stat", name, err}
	}
	return b.base.Stat(name)
}

func (b *BasePathFs) Rename(oldname, newname string) (err error) {
	if oldname, err = b.RealPath(oldname); err != nil {
		return &os.PathError{"rename", oldname, err}
	}
	if newname, err = b.RealPath(newname); err != nil {
		return &os.PathError{"rename", newname, err}
	}
	return b.base.Rename(oldname, newname)
}

func (b *BasePathFs) RemoveAll(name string) (err error) {
	if name, err = b.RealPath(name); err != nil {
		return &os.PathError{"remove_all", name, err}
	}
	return b.base.RemoveAll(name)
}

func (b *BasePathFs) Remove(name string) (err error) {
	if name, err = b.RealPath(name); err != nil {
		return &os.PathError{"remove", name, err}
	}
	return b.base.Remove(name)
}

func (b *BasePathFs) OpenFile(name string, flag int, mode os.FileMode) (f File, err error) {
	if name, err = b.RealPath(name); err != nil {
		return nil, &os.PathError{"openfile", name, err}
	}
	return b.base.OpenFile(name, flag, mode)
}

func (b *BasePathFs) Open(name string) (f File, err error) {
	if name, err = b.RealPath(name); err != nil {
		return nil, &os.PathError{"open", name, err}
	}
	return b.base.Open(name)
}

func (b *BasePathFs) Mkdir(name string, mode os.FileMode) (err error) {
	if name, err = b.RealPath(name); err != nil {
		return &os.PathError{"mkdir", name, err}
	}
	return b.base.Mkdir(name, mode)
}

func (b *BasePathFs) MkdirAll(name string, mode os.FileMode) (err error) {
	if name, err = b.RealPath(name); err != nil {
		return &os.PathError{"mkdir", name, err}
	}
	return b.base.MkdirAll(name, mode)
}

func (b *BasePathFs) Create(name string) (f File, err error) {
	if name, err = b.RealPath(name); err != nil {
		return nil, &os.PathError{"create", name, err}
	}
	return b.base.Create(name)
}

// vim: ts=4 sw=4 noexpandtab nolist syn=go