Add interactive switching to kubens

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

cmd/kubens/flags.go

@@ -3,7 +3,10 @@ package main
 import (
 	"fmt"
 	"io"
+	"os"
 	"strings"
+
+	"github.com/ahmetb/kubectx/internal/cmdutil"
 )
 
 // UnsupportedOp indicates an unsupported flag.
@@ -17,9 +20,9 @@ func (op UnsupportedOp) Run(_, _ io.Writer) error {
 // and decides which operation should be taken.
 func parseArgs(argv []string) Op {
 	if len(argv) == 0 {
-		//if env.IsInteractiveMode(os.Stdout) {
+		if cmdutil.IsInteractiveMode(os.Stdout) {
-		//	return InteractiveSwitchOp{SelfCmd: os.Args[0]}
+			return InteractiveSwitchOp{SelfCmd: os.Args[0]}
-		//}
+		}
 		return ListOp{}
 	}
 

cmd/kubens/fzf.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/pkg/errors"
+
+	"github.com/ahmetb/kubectx/internal/cmdutil"
+	"github.com/ahmetb/kubectx/internal/env"
+	"github.com/ahmetb/kubectx/internal/kubeconfig"
+	"github.com/ahmetb/kubectx/internal/printer"
+)
+
+type InteractiveSwitchOp struct {
+	SelfCmd string
+}
+
+// TODO(ahmetb) This method is heavily repetitive vs kubectx/fzf.go.
+func (op InteractiveSwitchOp) Run(_, stderr io.Writer) error {
+	// parse kubeconfig just to see if it can be loaded
+	kc := new(kubeconfig.Kubeconfig).WithLoader(cmdutil.DefaultLoader)
+	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")
+	}
+	defer kc.Close()
+
+	cmd := exec.Command("fzf", "--ansi", "--no-preview")
+	var out bytes.Buffer
+	cmd.Stdin = os.Stdin
+	cmd.Stderr = stderr
+	cmd.Stdout = &out
+
+	cmd.Env = append(os.Environ(),
+		fmt.Sprintf("FZF_DEFAULT_COMMAND=%s", op.SelfCmd),
+		fmt.Sprintf("%s=1", env.EnvForceColor))
+	if err := cmd.Run(); err != nil {
+		if _, ok := err.(*exec.ExitError); !ok {
+			return err
+		}
+	}
+	choice := strings.TrimSpace(out.String())
+	if choice == "" {
+		return errors.New("you did not choose any of the options")
+	}
+	name, err := switchNamespace(kc, choice)
+	if err != nil {
+		return errors.Wrap(err, "failed to switch context")
+	}
+	printer.Success(stderr, "Switched to context %s.", printer.SuccessColor.Sprint(name))
+	return nil
+}

cmd/kubens/switch.go

@@ -21,52 +21,59 @@ func (s SwitchOp) Run(_, stderr io.Writer) error {
 		return errors.Wrap(err, "kubeconfig error")
 	}
 
+	toNS, err := switchNamespace(kc, s.Target)
+	if err != nil {
+		return err
+	}
+	err = printer.Success(stderr, "Active namespace is %q", toNS)
+	return err
+}
+
+func switchNamespace(kc *kubeconfig.Kubeconfig, ns string) (string, error) {
 	ctx := kc.GetCurrentContext()
 	if ctx == "" {
-		return errors.New("current-context is not set")
+		return "", errors.New("current-context is not set")
 	}
 	curNS, err := kc.NamespaceOfContext(ctx)
 	if ctx == "" {
-		return errors.New("failed to get current namespace")
+		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")
+		return "", errors.Wrap(err, "failed to load previous namespace from file")
 	}
 
-	toNS := s.Target
+	if ns == "-" {
-	if s.Target == "-" {
 		if prev == "" {
-			return errors.Errorf("No previous namespace found for current context (%s)", ctx)
+			return "", errors.Errorf("No previous namespace found for current context (%s)", ctx)
 		}
-		toNS = prev
+		ns = prev
 	}
 
-	ok, err := namespaceExists(toNS)
+	ok, err := namespaceExists(ns)
 	if err != nil {
-		return errors.Wrap(err, "failed to query if namespace exists (is cluster accessible?)")
+		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)
+		return "", errors.Errorf("no namespace exists with name %q", ns)
 	}
 
-	if err := kc.SetNamespace(ctx, toNS); err != nil {
+	if err := kc.SetNamespace(ctx, ns); err != nil {
-		return errors.Wrapf(err, "failed to change to namespace %q", toNS)
+		return "", errors.Wrapf(err, "failed to change to namespace %q", ns)
 	}
 	if err := kc.Save(); err != nil {
-		return errors.Wrap(err, "failed to save kubeconfig file")
+		return "", errors.Wrap(err, "failed to save kubeconfig file")
 	}
-	if curNS != toNS {
+	if curNS != ns {
 		if err := f.Save(curNS); err != nil {
-			return errors.Wrap(err, "failed to save the previous namespace to file")
+			return "", errors.Wrap(err, "failed to save the previous namespace to file")
 		}
 	}
+	return ns, nil
+}
 
-	err = printer.Success(stderr, "Active namespace is %q", toNS)
-	return err
-}
 
 func namespaceExists(ns string) (bool, error) {
 	nses, err := queryNamespaces()