// migrateVolume links the contents of a volume created pre Docker 1.7
// into the location expected by the local driver.
// It creates a symlink from DOCKER_ROOT/vfs/dir/VOLUME_ID to DOCKER_ROOT/volumes/VOLUME_ID/_container_data.
// It preserves the volume json configuration generated pre Docker 1.7 to be able to
// downgrade from Docker 1.7 to Docker 1.6 without losing volume compatibility.
func migrateVolume(id, vfs string) error {
	l, err := volumedrivers.Lookup(volume.DefaultDriverName)
	if err != nil {
		return err
	}

	newDataPath := l.(*local.Root).DataPath(id)
	fi, err := os.Stat(newDataPath)
	if err != nil && !os.IsNotExist(err) {
		return err
	}

	if fi != nil && fi.IsDir() {
		return nil
	}

	return os.Symlink(vfs, newDataPath)
}

// verifyVolumesInfo ports volumes configured for the containers pre docker 1.7.
// It reads the container configuration and creates valid mount points for the old volumes.
func (daemon *Daemon) verifyVolumesInfo(container *Container) error {
	// Inspect old structures only when we're upgrading from old versions
	// to versions >= 1.7 and the MountPoints has not been populated with volumes data.
	if len(container.MountPoints) == 0 && len(container.Volumes) > 0 {
		for destination, hostPath := range container.Volumes {
			vfsPath := filepath.Join(daemon.root, "vfs", "dir")
			rw := container.VolumesRW != nil && container.VolumesRW[destination]

			if strings.HasPrefix(hostPath, vfsPath) {
				id := filepath.Base(hostPath)
				if err := migrateVolume(id, hostPath); err != nil {
					return err
				}
				container.addLocalMountPoint(id, destination, rw)
			} else { // Bind mount
				id, source := volume.ParseVolumeSource(hostPath)
				container.addBindMountPoint(id, source, destination, rw)
			}
		}
	} else if len(container.MountPoints) > 0 {
		// Volumes created with a Docker version >= 1.7. We verify integrity in case of data created
		// with Docker 1.7 RC versions that put the information in
		// DOCKER_ROOT/volumes/VOLUME_ID rather than DOCKER_ROOT/volumes/VOLUME_ID/_container_data.
		l, err := volumedrivers.Lookup(volume.DefaultDriverName)
		if err != nil {
			return err
		}

		for _, m := range container.MountPoints {
			if m.Driver != volume.DefaultDriverName {
				continue
			}
			dataPath := l.(*local.Root).DataPath(m.Name)
			volumePath := filepath.Dir(dataPath)

			d, err := ioutil.ReadDir(volumePath)
			if err != nil {
				// If the volume directory doesn't exist yet it will be recreated,
				// so we only return the error when there is a different issue.
				if !os.IsNotExist(err) {
					return err
				}
				// Do not check when the volume directory does not exist.
				continue
			}
			if validVolumeLayout(d) {
				continue
			}

			if err := os.Mkdir(dataPath, 0755); err != nil {
				return err
			}

			// Move data inside the data directory
			for _, f := range d {
				oldp := filepath.Join(volumePath, f.Name())
				newp := filepath.Join(dataPath, f.Name())
				if err := os.Rename(oldp, newp); err != nil {
					logrus.Errorf("Unable to move %s to %s\n", oldp, newp)
				}
			}
		}

		return container.toDiskLocking()
	}

	return nil
}