cluster: introduce Region.Cluster and m/{region}/k8s_token

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

pkg/cluster/cluster_scan.go

@@ -4,6 +4,7 @@ import (
 	"io/fs"
 	"path"
 	"sort"
+	"strings"
 
 	"darvaza.org/core"
 )
@@ -12,6 +13,10 @@ const (
 	// ZoneRegionsFileName indicates the file containing
 	// region names as references
 	ZoneRegionsFileName = "regions"
+
+	// RegionClusterTokenFileName contains the kubernetes
+	// token of the cluster this region represents
+	RegionClusterTokenFileName = "k8s_token"
 )
 
 func (m *Cluster) scan(opts *ScanOptions) error {
@@ -186,6 +191,8 @@ func (z *Zone) scan() error {
 		switch {
 		case name == ZoneRegionsFileName:
 			err = z.loadRegions()
+		case name == RegionClusterTokenFileName:
+			err = z.loadClusterToken()
 		case e.IsDir():
 			err = z.scanSubdirectory(name)
 		default:
@@ -218,6 +225,32 @@ func (z *Zone) loadRegions() error {
 	return err
 }
 
+func (z *Zone) loadClusterToken() error {
+	var token string
+
+	filename := path.Join(z.Name, RegionClusterTokenFileName)
+	lines, err := z.zones.ReadLines(filename)
+	if err != nil {
+		return err
+	}
+
+	// first non-empty line
+	for _, s := range lines {
+		s = strings.TrimSpace(s)
+		if s != "" {
+			token = s
+			break
+		}
+	}
+
+	err = z.zones.setRegionClusterToken(z.Name, token)
+	if err != nil {
+		err = core.Wrap(err, filename)
+	}
+
+	return err
+}
+
 func (z *Zone) scanSubdirectory(name string) error {
 	m := &Machine{
 		zone:   z,