// getDisks builds the raw spec for the disks that should be attached to
// the new instances and returns it. This will always include a root
// disk with characteristics determined by the provides args and
// constraints.
func getDisks(spec *instances.InstanceSpec, cons constraints.Value, ser, eUUID string) ([]google.DiskSpec, error) {
	size := common.MinRootDiskSizeGiB(ser)
	if cons.RootDisk != nil && *cons.RootDisk > size {
		size = common.MiBToGiB(*cons.RootDisk)
	}
	var imageURL string
	os, err := series.GetOSFromSeries(ser)
	if err != nil {
		return nil, errors.Trace(err)
	}
	switch os {
	case jujuos.Ubuntu:
		imageURL = ubuntuImageBasePath
	case jujuos.Windows:
		imageURL = windowsImageBasePath
	default:
		return nil, errors.Errorf("os %s is not supported on the gce provider", os.String())
	}
	dSpec := google.DiskSpec{
		Series:      ser,
		SizeHintGB:  size,
		ImageURL:    imageURL + spec.Image.Id,
		Boot:        true,
		AutoDelete:  true,
		Description: eUUID,
	}
	if cons.RootDisk != nil && dSpec.TooSmall() {
		msg := "Ignoring root-disk constraint of %dM because it is smaller than the GCE image size of %dG"
		logger.Infof(msg, *cons.RootDisk, google.MinDiskSizeGB(ser))
	}
	return []google.DiskSpec{dSpec}, nil
}

// getDisks builds the raw spec for the disks that should be attached to
// the new instances and returns it. This will always include a root
// disk with characteristics determined by the provides args and
// constraints.
func getDisks(spec *instances.InstanceSpec, cons constraints.Value) []google.DiskSpec {
	size := common.MinRootDiskSizeGiB
	if cons.RootDisk != nil && *cons.RootDisk > size {
		size = common.MiBToGiB(*cons.RootDisk)
	}
	dSpec := google.DiskSpec{
		SizeHintGB: size,
		ImageURL:   imageBasePath + spec.Image.Id,
		Boot:       true,
		AutoDelete: true,
	}
	if cons.RootDisk != nil && dSpec.TooSmall() {
		msg := "Ignoring root-disk constraint of %dM because it is smaller than the GCE image size of %dG"
		logger.Infof(msg, *cons.RootDisk, google.MinDiskSizeGB)
	}
	return []google.DiskSpec{dSpec}
}