// ApplyDiff extracts the changeset from the given diff into the
// layer with the specified id and parent, returning the size of the
// new layer in bytes.
func (gdw *naiveDiffDriver) ApplyDiff(id, parent string, diff archive.ArchiveReader) (bytes int64, err error) {
	driver := gdw.ProtoDriver

	// Mount the root filesystem so we can apply the diff/layer.
	layerFs, err := driver.Get(id, "")
	if err != nil {
		return
	}
	defer driver.Put(id)

	start := time.Now().UTC()
	log.Debugf("Start untar layer")
	if err = archive.ApplyLayer(layerFs, diff); err != nil {
		return
	}
	log.Debugf("Untar time: %vs", time.Now().UTC().Sub(start).Seconds())

	if parent == "" {
		return utils.TreeSize(layerFs)
	}

	parentFs, err := driver.Get(parent, "")
	if err != nil {
		err = fmt.Errorf("Driver %s failed to get image parent %s: %s", driver, parent, err)
		return
	}
	defer driver.Put(parent)

	changes, err := archive.ChangesDirs(layerFs, parentFs)
	if err != nil {
		return
	}

	return archive.ChangesSize(layerFs, changes), nil
}

// ApplyDiff applies the new layer on top of the root, if parent does not exist with will return a ErrApplyDiffFallback error.
func (d *Driver) ApplyDiff(id string, parent string, diff archive.ArchiveReader) (size int64, err error) {
	dir := d.dir(id)

	if parent == "" {
		return 0, ErrApplyDiffFallback
	}

	parentRootDir := path.Join(d.dir(parent), "root")
	if _, err := os.Stat(parentRootDir); err != nil {
		return 0, ErrApplyDiffFallback
	}

	// We now know there is a parent, and it has a "root" directory containing
	// the full root filesystem. We can just hardlink it and apply the
	// layer. This relies on two things:
	// 1) ApplyDiff is only run once on a clean (no writes to upper layer) container
	// 2) ApplyDiff doesn't do any in-place writes to files (would break hardlinks)
	// These are all currently true and are not expected to break

	tmpRootDir, err := ioutil.TempDir(dir, "tmproot")
	if err != nil {
		return 0, err
	}
	defer func() {
		if err != nil {
			os.RemoveAll(tmpRootDir)
		} else {
			os.RemoveAll(path.Join(dir, "upper"))
			os.RemoveAll(path.Join(dir, "work"))
			os.RemoveAll(path.Join(dir, "merged"))
			os.RemoveAll(path.Join(dir, "lower-id"))
		}
	}()

	if err = copyDir(parentRootDir, tmpRootDir, copyHardlink); err != nil {
		return 0, err
	}

	start := time.Now().UTC()
	log.Debugf("Start untar layer")
	if err = chrootarchive.ApplyLayer(tmpRootDir, diff); err != nil {
		return 0, err
	}
	log.Debugf("Untar time: %vs", time.Now().UTC().Sub(start).Seconds())

	changes, err := archive.ChangesDirs(tmpRootDir, parentRootDir, nil)
	if err != nil {
		return 0, err
	}

	size = archive.ChangesSize(tmpRootDir, changes)

	rootDir := path.Join(dir, "root")
	if err := os.Rename(tmpRootDir, rootDir); err != nil {
		return 0, err
	}

	return
}

// DiffSize calculates the changes between the specified layer
// and its parent and returns the size in bytes of the changes
// relative to its base filesystem directory.
func (d *WindowsGraphDriver) DiffSize(id, parent string) (size int64, err error) {
	changes, err := d.Changes(id, parent)
	if err != nil {
		return
	}

	layerFs, err := d.Get(id, "")
	if err != nil {
		return
	}
	defer d.Put(id)

	return archive.ChangesSize(layerFs, changes), nil
}

// DiffSize calculates the changes between the specified layer
// and its parent and returns the size in bytes of the changes
// relative to its base filesystem directory.
func (gdw *naiveDiffDriver) DiffSize(id, parent string) (size int64, err error) {
	driver := gdw.ProtoDriver

	changes, err := gdw.Changes(id, parent)
	if err != nil {
		return
	}

	layerFs, err := driver.Get(id, "")
	if err != nil {
		return
	}
	defer driver.Put(id)

	return archive.ChangesSize(layerFs, changes), nil
}

// DiffSize calculates the changes between the specified layer
// and its parent and returns the size in bytes of the changes
// relative to its base filesystem directory.
func (d *Driver) DiffSize(id, parent string) (size int64, err error) {
	rPId, err := d.resolveID(parent)
	if err != nil {
		return
	}

	changes, err := d.Changes(id, rPId)
	if err != nil {
		return
	}

	layerFs, err := d.Get(id, "")
	if err != nil {
		return
	}
	defer d.Put(id)

	return archive.ChangesSize(layerFs, changes), nil
}