split-horizon-operator/internal/controller/externaldnswatcher_controller.go

/*
Copyright 2025.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package controller

import (
	"context"
	"fmt"
	dnsv1alpha1 "git.mayers.cloud/superflo22/split-horizon-operator/api/v1alpha1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"sigs.k8s.io/controller-runtime/pkg/handler"
	gatewayv1 "sigs.k8s.io/gateway-api/apis/v1"
	"strings"

	"k8s.io/apimachinery/pkg/runtime"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/log"
)

// ExternalDNSWatcherReconciler reconciles a ExternalDNSWatcher object
type ExternalDNSWatcherReconciler struct {
	client.Client
	Scheme *runtime.Scheme
}

// +kubebuilder:rbac:groups=dns.mayers.cloud,resources=externaldnswatchers,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=dns.mayers.cloud,resources=externaldnswatchers/status,verbs=get;update;patch
// +kubebuilder:rbac:groups=dns.mayers.cloud,resources=externaldnswatchers/finalizers,verbs=update

// Reconcile is part of the main kubernetes reconciliation loop which aims to
// move the current state of the cluster closer to the desired state.
// TODO(user): Modify the Reconcile function to compare the state specified by
// the ExternalDNSWatcher object against the actual cluster state, and then
// perform operations to make the cluster state reflect the state specified by
// the user.
//
// For more details, check Reconcile and its Result here:
// - https://pkg.go.dev/sigs.k8s.io/controller-runtime@v0.19.0/pkg/reconcile
func (r *ExternalDNSWatcherReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	log := log.FromContext(ctx)

	// Step 1: Fetch the Gateway
	var gateway gatewayv1.Gateway
	if err := r.Get(ctx, req.NamespacedName, &gateway); err != nil {
		return ctrl.Result{}, client.IgnoreNotFound(err)
	}

	// Step 2: Check annotation
	annotations := gateway.GetAnnotations()
	if annotations["dns.mayers.cloud/enabled"] != "true" {
		log.Info("ExternalDNS watcher is not enabled")
		return ctrl.Result{}, nil
	}

	network := annotations["dns.mayers.cloud/network"]
	authority := annotations["dns.mayers.cloud/authority"]
	if network == "" || authority == "" {
		log.Info("Missing required annotations")
		return ctrl.Result{}, nil
	}

	// Step 3: Get Gateway IP (if available)
	var gatewayIPs []string
	for _, addr := range gateway.Status.Addresses {
		if addr.Type == nil || *addr.Type == gatewayv1.IPAddressType {
			gatewayIPs = append(gatewayIPs, addr.Value)
		}
	}

	// Step 4: List HTTPRoutes that reference this Gateway
	var routes gatewayv1.HTTPRouteList
	if err := r.List(ctx, &routes, client.InNamespace(req.Namespace)); err != nil {
		return ctrl.Result{}, err
	}

	for _, route := range routes.Items {
		for _, parent := range route.Spec.ParentRefs {

			// Check if the parent is a Gateway and matches the current gateway
			if string(*parent.Kind) == "Gateway" && string(parent.Name) == gateway.Name {
				// Step 5: Collect hostnames
				for _, hostname := range route.Spec.Hostnames {
					record := &dnsv1alpha1.TechnitiumRecord{
						TypeMeta: metav1.TypeMeta{
							Kind:       "TechnitiumRecord",
							APIVersion: "dns.mayers.cloud/v1alpha1",
						},
						ObjectMeta: metav1.ObjectMeta{
							Name:      fmt.Sprintf("%s", strings.ReplaceAll(string(hostname), ".", "-")),
							Namespace: route.Namespace,
						},
						Spec: dnsv1alpha1.TechnitiumRecordSpec{
							AuthorityRef: dnsv1alpha1.AuthorityReference{
								Name: authority,
							},
							Name:      string(hostname),
							TTL:       300,
							ClassPath: "SimpleAddress",
							RecordData: map[string][]string{
								network: gatewayIPs,
							},
						},
					}
					// Log the record yaml
					log.Info("TechnitiumRecord", "record", record)

					if err := r.Client.Patch(ctx, record, client.Apply, client.ForceOwnership, client.FieldOwner("external-dns-watcher")); err != nil {
						log.Error(err, "Failed to apply TechnitiumRecord")
					} else {
						log.Info("Reconciled TechnitiumRecord", "name", record.Name)
					}
				}
			}
		}
	}

	return ctrl.Result{}, nil
}

// SetupWithManager sets up the controller with the Manager.
func (r *ExternalDNSWatcherReconciler) SetupWithManager(mgr ctrl.Manager) error {
	return ctrl.NewControllerManagedBy(mgr).
		// Uncomment the following line adding a pointer to an instance of the controlled resource as an argument
		Named("external_dns_controller").
		Watches(
			&gatewayv1.Gateway{},
			&handler.EnqueueRequestForObject{},
		).
		Watches(
			&gatewayv1.HTTPRoute{},
			&handler.EnqueueRequestForObject{},
		).
		Complete(r)
}