jpictl: introduce `jpictl dns write` command

it renders BIND config to describe the public view of the cluster

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

cmd/jpictl/dns.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"context"
+	"os"
+
+	"github.com/spf13/cobra"
+
+	"git.jpi.io/amery/jpictl/pkg/cluster"
+	"git.jpi.io/amery/jpictl/pkg/dns"
+)
+
+func newDNSManager(m *cluster.Cluster) (*dns.Manager, error) {
+	ctx := context.TODO()
+
+	domain := m.Domain
+	if m.Name != "" {
+		domain = m.Name + "." + domain
+	}
+
+	mgr, err := dns.NewManager(dns.WithDomain(domain), dns.WithLogger(log))
+	if err != nil {
+		return nil, err
+	}
+
+	m.ForEachZone(func(z *cluster.Zone) bool {
+		z.ForEachMachine(func(p *cluster.Machine) bool {
+			err = mgr.AddHost(ctx, z.Name, p.ID, true, p.PublicAddresses...)
+			return err != nil
+		})
+
+		return err != nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	m.ForEachRegion(func(r *cluster.Region) bool {
+		r.ForEachZone(func(z *cluster.Zone) bool {
+			err = mgr.AddRegion(ctx, r.Name, z.Name)
+			return err != nil
+		})
+
+		return err != nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return mgr, nil
+}
+
+// Command
+var dnsCmd = &cobra.Command{
+	Use: "dns",
+}
+
+var dnsWriteCmd = &cobra.Command{
+	Use:    "write",
+	Short:  "dns write generates public DNS records",
+	PreRun: setVerbosity,
+	RunE: func(_ *cobra.Command, _ []string) error {
+		m, err := cfg.LoadZones(true)
+		if err != nil {
+			return err
+		}
+
+		mgr, err := newDNSManager(m)
+		if err != nil {
+			return err
+		}
+
+		_, err = mgr.WriteTo(os.Stdout)
+		return err
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(dnsCmd)
+
+	dnsCmd.AddCommand(dnsWriteCmd)
+}