refactor: optimize namespace listing and tree display logic

cmd/kubectl-accurate/sub/list.go

@@ -57,44 +57,58 @@ func (o *listOptions) Fill(streams genericiooptions.IOStreams, config *genericcl
 }
 
 func (o *listOptions) Run(ctx context.Context) error {
+	nsList := &corev1.NamespaceList{}
+	if err := o.client.List(ctx, nsList); err != nil {
+		return fmt.Errorf("failed to list namespaces from Kubernetes API: %w", err)
+	}
+
+	nsMap := make(map[string][]corev1.Namespace)
+	for _, ns := range nsList.Items {
+		parent := ""
+		if ns.Labels != nil {
+			if p, exists := ns.Labels[constants.LabelParent]; exists {
+				parent = p
+			}
+		}
+		nsMap[parent] = append(nsMap[parent], ns)
+	}
+
 	if o.root != "" {
-		return o.showNS(ctx, o.root, 0)
+		if _, exists := nsMap[o.root]; !exists {
+			return fmt.Errorf("specified root namespace '%s' not found", o.root)
+		}
+		return o.showNSTree(ctx, o.root, nsMap, 0)
 	}
 
-	roots := &corev1.NamespaceList{}
-	if err := o.client.List(ctx, roots, client.MatchingLabels{constants.LabelType: constants.NSTypeRoot}); err != nil {
-		return fmt.Errorf("failed to list the root namespaces: %w", err)
+	rootNamespaces, exists := nsMap[""]
+	if !exists || len(rootNamespaces) == 0 {
+		return fmt.Errorf("no root namespaces found; ensure namespaces have correct labels")
 	}
 
-	for _, ns := range roots.Items {
-		if err := o.showNS(ctx, ns.Name, 0); err != nil {
-			return err
+	for _, ns := range rootNamespaces {
+		if err := o.showNSTree(ctx, ns.Name, nsMap, 0); err != nil {
+			return fmt.Errorf("failed to display namespace tree for '%s': %w", ns.Name, err)
 		}
 	}
 	return nil
 }
 
-func (o *listOptions) showNS(ctx context.Context, name string, level int) error {
-	ns := &corev1.Namespace{}
-	if err := o.client.Get(ctx, client.ObjectKey{Name: name}, ns); err != nil {
-		return fmt.Errorf("failed to get namespace %s: %w", name, err)
+func (o *listOptions) showNSTree(ctx context.Context, name string, nsMap map[string][]corev1.Namespace, level int) error {
+	if name == "" {
+		return fmt.Errorf("invalid namespace name: empty string")
 	}
 
-	subMark := " "
-	if _, ok := ns.Labels[constants.LabelParent]; ok {
-		subMark = "⮡"
-	}
-	fmt.Fprintf(o.streams.Out, "%*s%s%s\n", level, "", subMark, name)
+	fmt.Fprintf(o.streams.Out, "%*s%s\n", level, "", name)
 
-	children := &corev1.NamespaceList{}
-	if err := o.client.List(ctx, children, client.MatchingLabels{constants.LabelParent: name}); err != nil {
-		return fmt.Errorf("failed to list the children of %s: %w", name, err)
+	children, exists := nsMap[name]
+	if !exists || len(children) == 0 {
+		return nil
 	}
 
 	level += indent
-	for _, child := range children.Items {
-		if err := o.showNS(ctx, child.Name, level); err != nil {
-			return err
+	for _, child := range children {
+		if err := o.showNSTree(ctx, child.Name, nsMap, level); err != nil {
+			return fmt.Errorf("failed to process child namespace '%s': %w", child.Name, err)
 		}
 	}
 	return nil