cluster: introduce Region interators

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

pkg/cluster/regions.go

@@ -1,5 +1,10 @@
 package cluster
 
+var (
+	_ MachineIterator = (*Region)(nil)
+	_ ZoneIterator    = (*Region)(nil)
+)
+
 // Region represents a group of zones geographically related
 type Region struct {
 	m     *Cluster
@@ -9,6 +14,43 @@ type Region struct {
 	Regions []string `json:",omitempty" yaml:",omitempty"`
 }
 
+// ForEachRegion calls a function for each Region of the cluster
+// until instructed to terminate the loop
+func (m *Cluster) ForEachRegion(fn func(r *Region) bool) {
+	for i := range m.Regions {
+		r := &m.Regions[i]
+		if fn(r) {
+			return
+		}
+	}
+}
+
+// ForEachMachine calls a function for each Machine in the region
+// until instructed to terminate the loop
+func (r *Region) ForEachMachine(fn func(*Machine) bool) {
+	r.ForEachZone(func(z *Zone) bool {
+		var term bool
+
+		z.ForEachMachine(func(p *Machine) bool {
+			term = fn(p)
+			return term
+		})
+
+		return term
+	})
+}
+
+// ForEachZone calls a function for each Zone in the region
+// until instructed to terminate the loop
+func (r *Region) ForEachZone(fn func(*Zone) bool) {
+	for _, p := range r.zones {
+		if fn(p) {
+			// terminate
+			return
+		}
+	}
+}
+
 func (m *Cluster) initRegions(_ *ScanOptions) error {
 	regions := make(map[string][]*Zone)