supervisor-oidc: hoist OIDC discovery handler for testing

Signed-off-by: Andrew Keesler <akeesler@vmware.com>

internal/controller/supervisorconfig/dynamic_config_watcher.go

@@ -4,6 +4,9 @@
 package supervisorconfig
 
 import (
+	"fmt"
+
+	k8serrors "k8s.io/apimachinery/pkg/api/errors"
 	corev1informers "k8s.io/client-go/informers/core/v1"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/klog/v2"
@@ -12,14 +15,30 @@ import (
 	"go.pinniped.dev/internal/controllerlib"
 )
 
+const (
+	issuerConfigMapKey = "issuer"
+)
+
+// IssuerSetter can be notified of a valid issuer with its SetIssuer function. If there is no
+// longer any valid issuer, then nil can be passed to this interface.
+//
+// Implementations of this type should be thread-safe to support calls from multiple goroutines.
+type IssuerSetter interface {
+	SetIssuer(issuer *string)
+}
+
 type dynamicConfigWatcherController struct {
-	k8sClient         kubernetes.Interface
-	configMapInformer corev1informers.ConfigMapInformer
+	configMapName      string
+	configMapNamespace string
+	issuerSetter       IssuerSetter
+	k8sClient          kubernetes.Interface
+	configMapInformer  corev1informers.ConfigMapInformer
 }
 
 func NewDynamicConfigWatcherController(
 	serverInstallationNamespace string,
 	configMapName string,
+	issuerObserver IssuerSetter,
 	k8sClient kubernetes.Interface,
 	configMapInformer corev1informers.ConfigMapInformer,
 	withInformer pinnipedcontroller.WithInformerOptionFunc,
@@ -28,8 +47,11 @@ func NewDynamicConfigWatcherController(
 		controllerlib.Config{
 			Name: "DynamicConfigWatcherController",
 			Syncer: &dynamicConfigWatcherController{
-				k8sClient:         k8sClient,
-				configMapInformer: configMapInformer,
+				configMapNamespace: serverInstallationNamespace,
+				configMapName:      configMapName,
+				issuerSetter:       issuerObserver,
+				k8sClient:          k8sClient,
+				configMapInformer:  configMapInformer,
 			},
 		},
 		withInformer(
@@ -44,9 +66,47 @@ func NewDynamicConfigWatcherController(
 func (c *dynamicConfigWatcherController) Sync(ctx controllerlib.Context) error {
 	// TODO Watch the configmap to find the issuer name, ingress url, etc.
 	// TODO Update some kind of in-memory representation of the configuration so the discovery endpoint can use it.
-	// TODO The discovery endpoint would return an error until all missing configuration options are filled in.
+	// TODO The discovery endpoint would return an error until all missing configuration options are
+	// filled in.
 
-	klog.InfoS("DynamicConfigWatcherController sync finished")
+	configMap, err := c.configMapInformer.
+		Lister().
+		ConfigMaps(c.configMapNamespace).
+		Get(c.configMapName)
+	notFound := k8serrors.IsNotFound(err)
+	if err != nil && !notFound {
+		return fmt.Errorf("failed to get %s/%s secret: %w", c.configMapNamespace, c.configMapName, err)
+	}
+
+	if notFound {
+		klog.InfoS(
+			"dynamicConfigWatcherController Sync found no configmap",
+			"configmap",
+			klog.KRef(c.configMapNamespace, c.configMapName),
+		)
+		c.issuerSetter.SetIssuer(nil)
+		return nil
+	}
+
+	issuer, ok := configMap.Data[issuerConfigMapKey]
+	if !ok {
+		klog.InfoS(
+			"dynamicConfigWatcherController Sync found no issuer",
+			"configmap",
+			klog.KObj(configMap),
+		)
+		c.issuerSetter.SetIssuer(nil)
+		return nil
+	}
+
+	klog.InfoS(
+		"dynamicConfigWatcherController Sync issuer",
+		"configmap",
+		klog.KObj(configMap),
+		"issuer",
+		issuer,
+	)
+	c.issuerSetter.SetIssuer(&issuer)
 
 	return nil
 }