package rings

import "net/netip"

// RingThreePrefix returns the subnet corresponding to
// the pods of a cluster.
//
// Ring 3 is a `10.(region_id << 4).0.0/12` network
func RingThreePrefix(region RegionID) (subnet netip.Prefix, err error) {
	switch {
	case !region.Valid():
		err = ErrOutOfRange(region, "region")
	default:
		addr := AddrFrom4(10, uint(region)<<4, 0, 0)
		subnet = netip.PrefixFrom(addr, RingThreeBits)
	}
	return subnet, err
}