cluster: add recursive RegionIterator to Zone

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/cluster/regions.go

@@ -9,6 +9,7 @@ var (
 	_ MachineIterator = (*Region)(nil)
 	_ ZoneIterator    = (*Region)(nil)
 
+	_ RegionIterator = (*Zone)(nil)
 	_ RegionIterator = (*Cluster)(nil)
 )
 
@@ -131,6 +132,28 @@ func (m *Cluster) appendRegionRegions(name string, subs ...string) {
 	})
 }
 
+// ForEachRegion calls a function on all regions this zone belongs to.
+func (z *Zone) ForEachRegion(fn func(*Region) bool) {
+	if fn == nil {
+		return
+	}
+
+	z.zones.ForEachRegion(func(r *Region) bool {
+		var match bool
+
+		r.ForEachZone(func(z2 *Zone) bool {
+			match = (z == z2)
+			return match
+		})
+
+		if match && fn(r) {
+			return true
+		}
+
+		return false
+	})
+}
+
 func (z *Zone) appendRegions(regions ...string) error {
 	for _, s := range regions {
 		// TODO: validate