kubens: implement namespace switching

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

cmd/kubens/list.go

@@ -22,10 +22,6 @@ func (op ListOp) Run(stdout, stderr io.Writer) error {
 	kc := new(kubeconfig.Kubeconfig).WithLoader(cmdutil.DefaultLoader)
 	defer kc.Close()
 	if err := kc.Parse(); err != nil {
-		if cmdutil.IsNotFoundErr(err) {
-			printer.Warning(stderr, "kubeconfig file not found")
-			return nil
-		}
 		return errors.Wrap(err, "kubeconfig error")
 	}
 
@@ -38,13 +34,9 @@ func (op ListOp) Run(stdout, stderr io.Writer) error {
 		return errors.Wrap(err, "cannot read current namespace")
 	}
 
-	kubectl, err := findKubectl()
+	ns, err := queryNamespaces()
 	if err != nil {
-		return err
-	}
-	ns, err := queryNamespaces(kubectl)
-	if err != nil {
-		return err
+		return errors.Wrap(err, "could not list namespaces (is the cluster accessible?)")
 	}
 
 	currentColor := color.New(color.FgGreen, color.Bold)
@@ -68,7 +60,14 @@ func findKubectl() (string, error) {
 	return v, errors.Wrap(err, "kubectl not found, needed for kubens")
 }
 
-func queryNamespaces(kubectl string) ([]string, error) {
+func queryNamespaces() ([]string, error) {
+	kubectl ,err := findKubectl()
+	if err != nil {
+		return nil ,err
+	}
+
+	// TODO add a log message to user if kubectl is taking >1s
+
 	var b bytes.Buffer
 	cmd := exec.Command(kubectl, "get", "namespaces", `-o=jsonpath={range .items[*].metadata.name}{@}{"\n"}{end}`)
 	cmd.Env = os.Environ()

cmd/kubens/statefile.go

@@ -9,7 +9,7 @@ import (
 	"github.com/ahmetb/kubectx/internal/cmdutil"
 )
 
-var defaultDir = filepath.Join(cmdutil.HomeDir(), "kubens")
+var defaultDir = filepath.Join(cmdutil.HomeDir(), ".kube", "kubens")
 
 type NSFile struct {
 	dir string

cmd/kubens/switch.go

@@ -2,10 +2,81 @@ package main
 
 import (
 	"io"
+
+	"github.com/pkg/errors"
+
+	"github.com/ahmetb/kubectx/internal/cmdutil"
+	"github.com/ahmetb/kubectx/internal/kubeconfig"
+	"github.com/ahmetb/kubectx/internal/printer"
 )
 
-type SwitchOp struct{ Target string }
-
-func (s SwitchOp) Run(stdout, stderr io.Writer) error {
-	panic("implement me")
+type SwitchOp struct {
+	Target string // '-' for back and forth, or NAME
+}
+
+func (s SwitchOp) Run(_, stderr io.Writer) error {
+	kc := new(kubeconfig.Kubeconfig).WithLoader(cmdutil.DefaultLoader)
+	defer kc.Close()
+	if err := kc.Parse(); err != nil {
+		return errors.Wrap(err, "kubeconfig error")
+	}
+
+	ctx := kc.GetCurrentContext()
+	if ctx == "" {
+		return errors.New("current-context is not set")
+	}
+	curNS, err := kc.NamespaceOfContext(ctx)
+	if ctx == "" {
+		return errors.New("failed to get current namespace")
+	}
+
+	f := NewNSFile(ctx)
+	prev, err := f.Load()
+	if err != nil {
+		return errors.Wrap(err, "failed to load previous namespace from file")
+	}
+
+	toNS := s.Target
+	if s.Target == "-" {
+		if prev == "" {
+			return errors.Errorf("No previous namespace found for current context (%s)", ctx)
+		}
+		toNS = prev
+	}
+
+	ok, err := namespaceExists(toNS)
+	if err != nil {
+		return errors.Wrap(err, "failed to query if namespace exists (is cluster accessible?)")
+	}
+	if !ok {
+		return errors.Errorf("no namespace exists with name %q", toNS)
+	}
+
+	if err := kc.SetNamespace(ctx, toNS); err != nil {
+		return errors.Wrapf(err, "failed to change to namespace %q", toNS)
+	}
+	if err := kc.Save(); err != nil {
+		return errors.Wrap(err, "failed to save kubeconfig file")
+	}
+	if curNS != toNS {
+		if err := f.Save(curNS); err != nil {
+			return errors.Wrap(err, "failed to save the previous namespace to file")
+		}
+	}
+
+	err = printer.Success(stderr, "Active namespace is %q", toNS)
+	return err
+}
+
+func namespaceExists(ns string) (bool, error) {
+	nses, err := queryNamespaces()
+	if err != nil {
+		return false, err
+	}
+	for _, v := range nses {
+		if v == ns {
+			return true, nil
+		}
+	}
+	return false, nil
 }