fix: optimize namespace listing to resolve N+1 problem

cmd/kubectl-accurate/sub/list.go

@@ -57,59 +57,45 @@ 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)
+	allNamespaces := &corev1.NamespaceList{}
+	if err := o.client.List(ctx, allNamespaces); err != nil {
+		return fmt.Errorf("failed to list all namespaces: %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 := make(map[string]*corev1.Namespace)
+	childMap := make(map[string][]*corev1.Namespace)
+
+	for i := range allNamespaces.Items {
+		ns := &allNamespaces.Items[i]
+		nsMap[ns.Name] = ns
+		if parent, ok := ns.Labels[constants.LabelParent]; ok {
+			childMap[parent] = append(childMap[parent], ns)
 		}
-		nsMap[parent] = append(nsMap[parent], ns)
 	}
 
-	if o.root != "" {
-		if _, exists := nsMap[o.root]; !exists {
-			return fmt.Errorf("specified root namespace '%s' not found", o.root)
+	var roots []*corev1.Namespace
+	for _, ns := range allNamespaces.Items {
+		if ns.Labels[constants.LabelType] == constants.NSTypeRoot {
+			roots = append(roots, &ns)
 		}
-		return o.showNSTree(ctx, o.root, nsMap, 0)
 	}
 
-	rootNamespaces, exists := nsMap[""]
-	if !exists || len(rootNamespaces) == 0 {
-		return fmt.Errorf("no root namespaces found; ensure namespaces have correct labels")
+	for _, root := range roots {
+		o.showNSRecursive(root, childMap, 0)
 	}
 
-	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) showNSTree(ctx context.Context, name string, nsMap map[string][]corev1.Namespace, level int) error {
-	if name == "" {
-		return fmt.Errorf("invalid namespace name: empty string")
-	}
-
-	fmt.Fprintf(o.streams.Out, "%*s%s\n", level, "", name)
-
-	children, exists := nsMap[name]
-	if !exists || len(children) == 0 {
-		return nil
+func (o *listOptions) showNSRecursive(ns *corev1.Namespace, childMap map[string][]*corev1.Namespace, level int) {
+	subMark := " "
+	if _, ok := ns.Labels[constants.LabelParent]; ok {
+		subMark = "⮡"
 	}
+	fmt.Fprintf(o.streams.Out, "%*s%s%s\n", level, "", subMark, ns.Name)
 
 	level += indent
-	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)
-		}
+	for _, child := range childMap[ns.Name] {
+		o.showNSRecursive(child, childMap, level)
 	}
-	return nil
 }