From 20b341df619c8ba4b35e8f994dff3fdf5db745be Mon Sep 17 00:00:00 2001
From: Tapajit Chandra Paul <tapajit@appscode.com>
Date: Thu, 7 Sep 2023 16:33:03 +0600
Subject: [PATCH] Add default valid nodepool name generator and Update
 validator for the nodepool name

Signed-off-by: Tapajit Chandra Paul <tapajit@appscode.com>
Signed-off-by: tapojit047 <tapajit@appscode.com>
---
 .../azuremanagedmachinepool_webhook.go        | 53 ++++++++++++++++++-
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/api/v1beta1/azuremanagedmachinepool_webhook.go b/api/v1beta1/azuremanagedmachinepool_webhook.go
index 86be164f2aa..decb9878678 100644
--- a/api/v1beta1/azuremanagedmachinepool_webhook.go
+++ b/api/v1beta1/azuremanagedmachinepool_webhook.go
@@ -23,11 +23,13 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"unicode"
 
 	"github.com/pkg/errors"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/runtime"
 	kerrors "k8s.io/apimachinery/pkg/util/errors"
+	utilrand "k8s.io/apimachinery/pkg/util/rand"
 	"k8s.io/apimachinery/pkg/util/validation/field"
 	"k8s.io/utils/ptr"
 	"sigs.k8s.io/cluster-api-provider-azure/feature"
@@ -72,9 +74,9 @@ func (mw *azureManagedMachinePoolWebhook) Default(ctx context.Context, obj runti
 	m.Labels[LabelAgentPoolMode] = m.Spec.Mode
 
 	if m.Spec.Name == nil || *m.Spec.Name == "" {
-		m.Spec.Name = &m.Name
+		aksNodePoolName := generateAKSNodePoolName(m.Name)
+		m.Spec.Name = &aksNodePoolName
 	}
-
 	if m.Spec.OSType == nil {
 		m.Spec.OSType = ptr.To(DefaultOSType)
 	}
@@ -82,6 +84,24 @@ func (mw *azureManagedMachinePoolWebhook) Default(ctx context.Context, obj runti
 	return nil
 }
 
+// Generates a valid unique nodepool name following limitations of Azure.
+func generateAKSNodePoolName(name string) string {
+	name = strings.ToLower(name)
+	name = strings.Map(func(r rune) rune {
+		if unicode.IsNumber(r) || unicode.IsLetter(r) {
+			return r
+		}
+		return -1
+	}, name)
+	name = strings.TrimLeftFunc(name, unicode.IsNumber)
+	if len(name) > 6 {
+		name = name[:6]
+	} else if name == "" {
+		name = "pool"
+	}
+	return fmt.Sprintf("%s%s", name, utilrand.String(6))
+}
+
 //+kubebuilder:webhook:verbs=create;update;delete,path=/validate-infrastructure-cluster-x-k8s-io-v1beta1-azuremanagedmachinepool,mutating=false,failurePolicy=fail,matchPolicy=Equivalent,groups=infrastructure.cluster.x-k8s.io,resources=azuremanagedmachinepools,versions=v1beta1,name=validation.azuremanagedmachinepools.infrastructure.cluster.x-k8s.io,sideEffects=None,admissionReviewVersions=v1;v1beta1
 
 // ValidateCreate implements webhook.Validator so a webhook will be registered for the type.
@@ -371,6 +391,35 @@ func (m *AzureManagedMachinePool) validateName() error {
 			"Windows agent pool name can not be longer than 6 characters.")
 	}
 
+	// Length check for linux following restrictions of AKS.
+	if (m.Spec.OSType == nil || *m.Spec.OSType == LinuxOS) &&
+		(m.Spec.Name != nil && len(*m.Spec.Name) > 12) {
+		return field.Invalid(
+			field.NewPath("Spec", "Name"),
+			m.Spec.Name,
+			"Linux agent pool name can not be longer than 12 characters.")
+	}
+
+	// Common Checks for both Windows & Linux following restrictions of AKS.
+	if m.Spec.Name != nil {
+		for _, char := range *m.Spec.Name {
+			if !unicode.IsLower(char) && !unicode.IsNumber(char) {
+				return field.Invalid(
+					field.NewPath("Spec", "Name"),
+					m.Spec.Name,
+					"Agent pool name may only contain lowercase alphanumeric characters.")
+			}
+		}
+
+		nodePoolName := *m.Spec.Name
+		if !unicode.IsLower(rune(nodePoolName[0])) {
+			return field.Invalid(
+				field.NewPath("Spec", "Name"),
+				m.Spec.Name,
+				"Linux agent pool name must begin with a lowercase letter.")
+		}
+	}
+
 	return nil
 }