feat: gateway Controller watches HTTPRoutes

The Gateway controller now watches for all the accepted HTTPRoutes that
reference it as a parent.

Signed-off-by: Mattia Lavacca <lavacca.mattia@gmail.com>

internal/controllers/gateway/gateway_controller.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/go-logr/logr"
 	"github.com/kong/go-kong/kong"
+	"github.com/samber/lo"
 	"github.com/samber/mo"
 	corev1 "k8s.io/api/core/v1"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
@@ -130,6 +131,15 @@ func (r *GatewayReconciler) SetupWithManager(mgr ctrl.Manager) error {
 		return err
 	}
 
+	// if a HTTPRoute gets accepted by a Gateway, we need to make sure to trigger
+	// reconciliation on the gateway, as we need to update the number of attachedRoutes.
+	if err := c.Watch(
+		&source.Kind{Type: &gatewayv1beta1.HTTPRoute{}},
+		handler.EnqueueRequestsFromMapFunc(r.listGatewaysForHTTPRoute),
+	); err != nil {
+		return err
+	}
+
 	// watch ReferenceGrants, which may invalidate or allow cross-namespace TLSConfigs
 	if r.enableReferenceGrant {
 		if err := c.Watch(
@@ -266,6 +276,43 @@ func (r *GatewayReconciler) listGatewaysForService(svc client.Object) (recs []re
 	return
 }
 
+// TODO
+func (r *GatewayReconciler) listGatewaysForHTTPRoute(obj client.Object) []reconcile.Request {
+	httpRoute, ok := obj.(*gatewayv1beta1.HTTPRoute)
+	if !ok {
+		r.Log.Error(
+			fmt.Errorf("unexpected object type"),
+			"httproute watch predicate received unexpected object type",
+			"expected", "*gatewayv1beta1.HTTPRoute", "found", reflect.TypeOf(obj),
+		)
+		return nil
+	}
+	recs := []reconcile.Request{}
+	for _, routeParentStatus := range httpRoute.Status.Parents {
+		gatewayNamespace := httpRoute.Namespace
+		parentRef := routeParentStatus.ParentRef
+		if (parentRef.Group != nil && parentRef.Group != &gatewayV1beta1Group) ||
+			(parentRef.Kind != nil && parentRef.Kind != util.StringToGatewayAPIKindPtr("HTTPRoute")) {
+			continue
+		}
+		if parentRef.Namespace != nil {
+			gatewayNamespace = string(*parentRef.Namespace)
+		}
+		if lo.ContainsBy(routeParentStatus.Conditions, func(condition metav1.Condition) bool {
+			return condition.Type == string(gatewayv1beta1.RouteConditionAccepted) &&
+				condition.Status == metav1.ConditionTrue
+		}) {
+			recs = append(recs, reconcile.Request{
+				NamespacedName: k8stypes.NamespacedName{
+					Namespace: gatewayNamespace,
+					Name:      string(parentRef.Name),
+				},
+			})
+		}
+	}
+	return recs
+}
+
 // isGatewayService is a watch predicate that filters out events for objects that aren't
 // the gateway service referenced by --publish-service or --publish-service-udp.
 func (r *GatewayReconciler) isGatewayService(obj client.Object) bool {