zones: set first node of a Zone as ring0 gateway if it doesn't have one already

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

pkg/zones/scan.go

@@ -11,6 +11,7 @@ func (m *Zones) scan() error {
 		m.scanMachines,
 		m.scanZoneIDs,
 		m.scanSort,
+		m.scanGateways,
 	} {
 		if err := fn(); err != nil {
 			return err
@@ -115,6 +116,16 @@ func (m *Zones) scanSort() error {
 	return nil
 }
 
+func (m *Zones) scanGateways() error {
+	var err error
+
+	m.ForEachZone(func(z *Zone) bool {
+		_, _, err = z.GetGateway()
+		return err != nil
+	})
+	return err
+}
+
 func (z *Zone) scan() error {
 	// each directory is a machine
 	entries, err := fs.ReadDir(z.zones.dir, z.Name)
@@ -139,3 +150,41 @@ func (z *Zone) scan() error {
 
 	return nil
 }
+
+// GetGateway returns the first gateway found, if none
+// files will be created to enable the first [Machine] to
+// be one
+func (z *Zone) GetGateway() (*Machine, bool, error) {
+	var first *Machine
+	var gateway *Machine
+
+	z.zones.ForEachMachine(func(p *Machine) bool {
+		switch {
+		case p.IsGateway():
+			// found
+			gateway = p
+		case first == nil:
+			// remember
+			first = p
+		default:
+			// keep looking
+		}
+
+		return gateway != nil
+	})
+
+	switch {
+	case gateway != nil:
+		// found one
+		return gateway, false, nil
+	case first != nil:
+		// make one
+		if err := first.SetGateway(true); err != nil {
+			return first, false, err
+		}
+		return first, true, nil
+	default:
+		// Zone without nodes?
+		panic("unreachable")
+	}
+}