feat: vertical slice proxy provider (#2)

Reviewed-on: #2
Co-authored-by: Timo Behrendt <t.behrendt@t00n.de>
Co-committed-by: Timo Behrendt <t.behrendt@t00n.de>

pkg/controllers/application/controller.go

@@ -0,0 +1,286 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+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 application
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"slices"
+	"strconv"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/kubernetes/scheme"
+	typedcorev1 "k8s.io/client-go/kubernetes/typed/core/v1"
+	"k8s.io/client-go/tools/cache"
+	"k8s.io/client-go/tools/record"
+	"k8s.io/client-go/util/workqueue"
+	"k8s.io/klog/v2"
+
+	v1alpha1 "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/apis/application/v1alpha1"
+	clientset "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned"
+	operatorscheme "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned/scheme"
+	informers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/informers/externalversions/application/v1alpha1"
+	listers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/listers/application/v1alpha1"
+	authentikapi "goauthentik.io/api/v3"
+)
+
+const controllerAgentName = "application-controller"
+
+const (
+	SuccessSynced         = "Synced"
+	ErrResourceExists     = "ErrResourceExists"
+	MessageResourceExists = "Resource %q already exists and is not managed by Application"
+	MessageResourceSynced = "Application synced successfully"
+	FieldManager          = controllerAgentName
+)
+
+// Finalizers
+const (
+	DeleteAuthentikApplicationFinalizer = "application.t000-n.de/delete-authentik-application"
+)
+
+type Controller struct {
+	kubeclientset        kubernetes.Interface
+	applicationClientset clientset.Interface
+	authentik            *authentikapi.APIClient
+
+	applicationListener listers.ApplicationLister
+	applicationSynced   cache.InformerSynced
+
+	workqueue workqueue.TypedRateLimitingInterface[cache.ObjectName]
+	recorder  record.EventRecorder
+}
+
+func NewController(
+	ctx context.Context,
+	kubeclientset kubernetes.Interface,
+	applicationClientset clientset.Interface,
+	authentik *authentikapi.APIClient,
+	applicationInformer informers.ApplicationInformer,
+) *Controller {
+	logger := klog.FromContext(ctx)
+
+	utilruntime.Must(operatorscheme.AddToScheme(scheme.Scheme))
+	logger.V(4).Info("Creating event broadcaster")
+
+	eventBroadcaster := record.NewBroadcaster(record.WithContext(ctx))
+	eventBroadcaster.StartStructuredLogging(0)
+	eventBroadcaster.StartRecordingToSink(&typedcorev1.EventSinkImpl{Interface: kubeclientset.CoreV1().Events("")})
+	recorder := eventBroadcaster.NewRecorder(scheme.Scheme, corev1.EventSource{Component: controllerAgentName})
+	ratelimiter := workqueue.NewTypedMaxOfRateLimiter(
+		workqueue.NewTypedItemExponentialFailureRateLimiter[cache.ObjectName](5*time.Millisecond, 1000*time.Second),
+		&workqueue.TypedBucketRateLimiter[cache.ObjectName]{Limiter: rate.NewLimiter(rate.Limit(50), 300)},
+	)
+
+	c := &Controller{
+		kubeclientset:        kubeclientset,
+		applicationClientset: applicationClientset,
+		authentik:            authentik,
+		applicationListener:  applicationInformer.Lister(),
+		applicationSynced:    applicationInformer.Informer().HasSynced,
+		workqueue:            workqueue.NewTypedRateLimitingQueue(ratelimiter),
+		recorder:             recorder,
+	}
+
+	logger.Info("Setting up event handlers")
+	applicationInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+		AddFunc: c.enqueueApplication,
+		UpdateFunc: func(_, newObj interface{}) {
+			c.enqueueApplication(newObj)
+		},
+	})
+
+	return c
+}
+
+func (c *Controller) Run(ctx context.Context, workers int) error {
+	defer utilruntime.HandleCrash()
+	defer c.workqueue.ShutDown()
+	logger := klog.FromContext(ctx)
+
+	logger.Info("Starting Application controller")
+
+	logger.Info("Waiting for informer caches to sync")
+	if ok := cache.WaitForCacheSync(ctx.Done(), c.applicationSynced); !ok {
+		return fmt.Errorf("failed to wait for caches to sync")
+	}
+
+	logger.Info("Starting workers", "count", workers)
+	for i := 0; i < workers; i++ {
+		go wait.UntilWithContext(ctx, c.runWorker, time.Second)
+	}
+
+	logger.Info("Started workers")
+	<-ctx.Done()
+	logger.Info("Shutting down workers")
+	return nil
+}
+
+func (c *Controller) runWorker(ctx context.Context) {
+	for c.processNextWorkItem(ctx) {
+	}
+}
+
+func (c *Controller) processNextWorkItem(ctx context.Context) bool {
+	objRef, shutdown := c.workqueue.Get()
+	logger := klog.FromContext(ctx)
+	if shutdown {
+		return false
+	}
+	defer c.workqueue.Done(objRef)
+
+	err := c.syncHandler(ctx, objRef)
+	if err == nil {
+		c.workqueue.Forget(objRef)
+		logger.Info("Successfully synced", "objectName", objRef)
+		return true
+	}
+	utilruntime.HandleErrorWithContext(ctx, err, "Error syncing; requeuing for later retry", "objectReference", objRef)
+	c.workqueue.AddRateLimited(objRef)
+	return true
+}
+
+func (c *Controller) syncHandler(ctx context.Context, objectRef cache.ObjectName) error {
+	logger := klog.LoggerWithValues(klog.FromContext(ctx), "objectRef", objectRef)
+
+	app, err := c.applicationListener.Applications(objectRef.Namespace).Get(objectRef.Name)
+	if err != nil {
+		if errors.IsNotFound(err) {
+			logger.V(4).Info("Application no longer exists")
+			return nil
+		}
+		return err
+	}
+	logger.V(4).Info("sync Application", "name", app.Name)
+
+	if !app.ObjectMeta.DeletionTimestamp.IsZero() {
+		logger.Info("Reconciling deletion of Application", "name", app.Name)
+		return c.reconcileDelete(ctx, app)
+	}
+
+	if app.Status.PK == "" {
+		logger.Info("Reconciling creation of Application", "name", app.Name)
+		return c.reconcileCreate(ctx, app)
+	}
+
+	// Check if all finalizers are present. If not, we add them. Same pattern as above, just needs a helper function to check for presence of a finalizer.
+	if !slices.Contains(app.ObjectMeta.Finalizers, DeleteAuthentikApplicationFinalizer) {
+		logger.Info("Ensuring finalizers are present", "name", app.Name)
+		return c.ensureFinalizers(ctx, app)
+	}
+
+	logger.Info("Reconciling update of Application", "name", app.Name)
+	return c.reconcileUpdate(ctx, app)
+}
+
+func (c *Controller) ensureFinalizers(ctx context.Context, app *v1alpha1.Application) error {
+	app.ObjectMeta.Finalizers = append(app.ObjectMeta.Finalizers, DeleteAuthentikApplicationFinalizer)
+	return c.updateApplication(ctx, app)
+}
+
+func (c *Controller) reconcileDelete(ctx context.Context, app *v1alpha1.Application) error {
+	pk, err := strconv.ParseInt(app.Status.PK, 10, 32)
+	if err != nil {
+		return fmt.Errorf("error parsing PK: %v", err)
+	}
+
+	r, err := c.authentik.ProvidersApi.ProvidersProxyDestroy(ctx, int32(pk)).Execute()
+	if err != nil {
+		// This handles an edge-case, where when the ProxyProvider on Authentik has already been deleted, but the finalizer is still present. We just remove the finalizer and return.
+		if r != nil && r.StatusCode != http.StatusNotFound {
+			return fmt.Errorf("error when calling `ProvidersAPI.ProvidersProxyDestroy`: %w with response %v", err, r)
+		}
+	}
+
+	app.ObjectMeta.Finalizers = slices.Delete(app.ObjectMeta.Finalizers, slices.Index(app.ObjectMeta.Finalizers, DeleteAuthentikApplicationFinalizer), 1)
+	return c.updateApplication(ctx, app)
+}
+
+func (c *Controller) reconcileUpdate(ctx context.Context, app *v1alpha1.Application) error {
+	_, r, err := c.authentik.CoreApi.CoreApplicationsRetrieve(ctx, app.Spec.Slug).Execute()
+	if err != nil {
+		if r != nil && r.StatusCode == http.StatusNotFound {
+			// This handles an edge-case, where when the Application on Authentik has been deleted, e.g. by mistake. We just remove the PK and return.
+			// During the next reconciliation, the Application will be re-created.
+			app.Status.PK = ""
+			return c.updateApplicationStatus(ctx, app)
+		}
+		return fmt.Errorf("error retrieving existing Application: %v with response %v", err, r)
+	}
+
+	patchedApplicationRequest := &authentikapi.PatchedApplicationRequest{
+		Name:     &app.Spec.Name,
+		Slug:     &app.Spec.Slug,
+		Provider: *authentikapi.NewNullableInt32(&app.Spec.Provider),
+	}
+	resp, r, err := c.authentik.CoreApi.CoreApplicationsPartialUpdate(ctx, app.Spec.Slug).PatchedApplicationRequest(*patchedApplicationRequest).Execute()
+	if err != nil {
+		return fmt.Errorf("error when calling `ProvidersAPI.ProvidersProxyPartialUpdate`: %w with response %v", err, r)
+	}
+
+	app.Status.PK = resp.Pk
+	return c.updateApplicationStatus(ctx, app)
+}
+
+func (c *Controller) reconcileCreate(ctx context.Context, app *v1alpha1.Application) error {
+	applicationRequest := &authentikapi.ApplicationRequest{
+		Name:     app.Spec.Name,
+		Slug:     app.Spec.Slug,
+		Provider: *authentikapi.NewNullableInt32(&app.Spec.Provider),
+	}
+	resp, r, err := c.authentik.CoreApi.CoreApplicationsCreate(ctx).ApplicationRequest(*applicationRequest).Execute()
+	if err != nil {
+		return fmt.Errorf("error when calling `CoreAPI.CoreApplicationsCreate`: %w with response %v", err, r)
+	}
+
+	app.Status.PK = resp.Pk
+	return c.updateApplicationStatus(ctx, app)
+}
+
+func (c *Controller) enqueueApplication(obj interface{}) {
+	objectRef, err := cache.ObjectToName(obj)
+	if err != nil {
+		utilruntime.HandleError(err)
+		return
+	}
+	c.workqueue.Add(objectRef)
+}
+
+func (c *Controller) updateApplicationStatus(ctx context.Context, app *v1alpha1.Application) error {
+	appCopy := app.DeepCopy()
+	_, err := c.applicationClientset.ApplicationV1alpha1().Applications(appCopy.Namespace).UpdateStatus(ctx, appCopy, metav1.UpdateOptions{FieldManager: FieldManager})
+	return err
+}
+
+// Update metadata, spec, etc. of the Application object.
+func (c *Controller) updateApplication(ctx context.Context, app *v1alpha1.Application) error {
+	appCopy := app.DeepCopy()
+	_, err := c.applicationClientset.ApplicationV1alpha1().Applications(appCopy.Namespace).Update(ctx, appCopy, metav1.UpdateOptions{FieldManager: FieldManager})
+	if err != nil {
+		return fmt.Errorf("error updating Application metadata: %v", err)
+	}
+	return nil
+}

pkg/controllers/application/controller_test.go

@@ -0,0 +1,395 @@
+// AI generated tests and not yet reviewed.
+package application
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"slices"
+	"strings"
+	"testing"
+
+	v1alpha1 "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/apis/application/v1alpha1"
+	operatorfake "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned/fake"
+	operatorinformers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/informers/externalversions"
+	authentikapi "goauthentik.io/api/v3"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/client-go/kubernetes/fake"
+	"k8s.io/client-go/tools/cache"
+)
+
+func TestController_syncHandler_create(t *testing.T) {
+	const wantPK = "42"
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		applicationCreate: func(w http.ResponseWriter, _ *http.Request) {
+			writeJSON(t, w, http.StatusCreated, map[string]any{"pk": wantPK})
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, testApplication(), server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: "default", Name: "test-app"})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getApplication(t, ctrl, "default", "test-app")
+	if got.Status.PK != wantPK {
+		t.Fatalf("status.pk = %q, want %q", got.Status.PK, wantPK)
+	}
+}
+
+func TestController_syncHandler_ensureFinalizers(t *testing.T) {
+	app := testApplication()
+	app.Status.PK = "42"
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, app, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: app.Namespace, Name: app.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getApplication(t, ctrl, app.Namespace, app.Name)
+	if !slices.Contains(got.Finalizers, DeleteAuthentikApplicationFinalizer) {
+		t.Fatalf("finalizers = %v, want %q", got.Finalizers, DeleteAuthentikApplicationFinalizer)
+	}
+}
+
+func TestController_syncHandler_update(t *testing.T) {
+	app := testApplication()
+	app.Status.PK = "42"
+	app.Finalizers = []string{DeleteAuthentikApplicationFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		applicationRetrieve: func(w http.ResponseWriter, _ *http.Request) {
+			writeJSON(t, w, http.StatusOK, map[string]any{"pk": "42"})
+		},
+		applicationPartialUpdate: func(w http.ResponseWriter, _ *http.Request) {
+			writeJSON(t, w, http.StatusOK, map[string]any{"pk": "42"})
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, app, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: app.Namespace, Name: app.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getApplication(t, ctrl, app.Namespace, app.Name)
+	if got.Status.PK != "42" {
+		t.Fatalf("status.pk = %q, want 42", got.Status.PK)
+	}
+}
+
+func TestController_syncHandler_update_applicationNotFound(t *testing.T) {
+	app := testApplication()
+	app.Status.PK = "42"
+	app.Finalizers = []string{DeleteAuthentikApplicationFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		applicationRetrieve: func(w http.ResponseWriter, _ *http.Request) {
+			http.NotFound(w, nil)
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, app, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: app.Namespace, Name: app.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getApplication(t, ctrl, app.Namespace, app.Name)
+	if got.Status.PK != "" {
+		t.Fatalf("status.pk = %q, want empty after application not found", got.Status.PK)
+	}
+}
+
+func TestController_syncHandler_delete(t *testing.T) {
+	now := metav1.Now()
+	app := testApplication()
+	app.Status.PK = "42"
+	app.DeletionTimestamp = &now
+	app.Finalizers = []string{DeleteAuthentikApplicationFinalizer}
+
+	var destroyCalled bool
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		proxyDestroy: func(w http.ResponseWriter, r *http.Request) {
+			destroyCalled = true
+			if r.Method != http.MethodDelete {
+				t.Errorf("destroy method = %s, want DELETE", r.Method)
+			}
+			w.WriteHeader(http.StatusNoContent)
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, app, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: app.Namespace, Name: app.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+	if !destroyCalled {
+		t.Fatal("expected Authentik destroy call")
+	}
+
+	got := getApplication(t, ctrl, app.Namespace, app.Name)
+	if slices.Contains(got.Finalizers, DeleteAuthentikApplicationFinalizer) {
+		t.Fatalf("finalizers = %v, want finalizer removed", got.Finalizers)
+	}
+}
+
+func TestController_syncHandler_delete_providerAlreadyGone(t *testing.T) {
+	now := metav1.Now()
+	app := testApplication()
+	app.Status.PK = "42"
+	app.DeletionTimestamp = &now
+	app.Finalizers = []string{DeleteAuthentikApplicationFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		proxyDestroy: func(w http.ResponseWriter, _ *http.Request) {
+			http.NotFound(w, nil)
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, app, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: app.Namespace, Name: app.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getApplication(t, ctrl, app.Namespace, app.Name)
+	if slices.Contains(got.Finalizers, DeleteAuthentikApplicationFinalizer) {
+		t.Fatalf("finalizers = %v, want finalizer removed after 404", got.Finalizers)
+	}
+}
+
+func TestController_syncHandler_notFound(t *testing.T) {
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, nil, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: "default", Name: "missing"})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v, want nil for missing object", err)
+	}
+}
+
+func TestController_syncHandler_invalidPK(t *testing.T) {
+	now := metav1.Now()
+	app := testApplication()
+	app.Status.PK = "not-a-number"
+	app.DeletionTimestamp = &now
+	app.Finalizers = []string{DeleteAuthentikApplicationFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, app, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: app.Namespace, Name: app.Name})
+	if err == nil {
+		t.Fatal("syncHandler() error = nil, want parse error")
+	}
+	if !strings.Contains(err.Error(), "error parsing PK") {
+		t.Fatalf("syncHandler() error = %v, want PK parse error", err)
+	}
+}
+
+func TestController_enqueueApplication(t *testing.T) {
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, _, cancel := newTestController(t, testApplication(), server.URL)
+	t.Cleanup(cancel)
+
+	ctrl.enqueueApplication(testApplication())
+
+	if ctrl.workqueue.Len() != 1 {
+		t.Fatalf("workqueue length = %d, want 1", ctrl.workqueue.Len())
+	}
+}
+
+// --- test helpers ---
+
+func testApplication() *v1alpha1.Application {
+	return &v1alpha1.Application{
+		TypeMeta: metav1.TypeMeta{
+			APIVersion: v1alpha1.SchemeGroupVersion.String(),
+			Kind:       "Application",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "test-app",
+			Namespace: "default",
+		},
+		Spec: v1alpha1.ApplicationSpec{
+			Name:     "My Application",
+			Slug:     "my-app",
+			Provider: 7,
+		},
+	}
+}
+
+func newTestController(t *testing.T, app *v1alpha1.Application, authentikURL string) (*Controller, context.Context, context.CancelFunc) {
+	t.Helper()
+	ctx, cancel := context.WithCancel(context.Background())
+	ctrl, _, stop := newTestControllerWithContext(t, ctx, app, authentikURL)
+	return ctrl, ctx, func() {
+		cancel()
+		stop()
+	}
+}
+
+func newTestControllerWithContext(t *testing.T, ctx context.Context, app *v1alpha1.Application, authentikURL string) (*Controller, context.Context, func()) {
+	t.Helper()
+
+	authentikClient := newAuthentikAPIClientForTest(t, authentikURL)
+
+	var objects []runtime.Object
+	if app != nil {
+		objects = append(objects, app)
+	}
+	applicationClient := operatorfake.NewSimpleClientset(objects...)
+
+	informerFactory := operatorinformers.NewSharedInformerFactory(applicationClient, 0)
+	applicationInformer := informerFactory.Application().V1alpha1().Applications()
+
+	ctrl := NewController(ctx, fake.NewClientset(), applicationClient, authentikClient, applicationInformer)
+
+	informerFactory.Start(ctx.Done())
+	for informerType, synced := range informerFactory.WaitForCacheSync(ctx.Done()) {
+		if !synced {
+			t.Fatalf("informer %v failed to sync", informerType)
+		}
+	}
+
+	return ctrl, ctx, func() {}
+}
+
+func newAuthentikAPIClientForTest(t *testing.T, serverURL string) *authentikapi.APIClient {
+	t.Helper()
+
+	u, err := url.Parse(serverURL)
+	if err != nil {
+		t.Fatalf("parse server URL: %v", err)
+	}
+
+	cfg := authentikapi.NewConfiguration()
+	cfg.Scheme = u.Scheme
+	cfg.Host = u.Host
+
+	return authentikapi.NewAPIClient(cfg)
+}
+
+type authentikTestHandlers struct {
+	applicationCreate        http.HandlerFunc
+	applicationRetrieve      http.HandlerFunc
+	applicationPartialUpdate http.HandlerFunc
+	proxyDestroy             http.HandlerFunc
+}
+
+func newAuthentikTestServer(t *testing.T, handlers authentikTestHandlers) *httptest.Server {
+	t.Helper()
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		path := r.URL.Path
+
+		switch {
+		case path == "/api/v3/core/applications/" && r.Method == http.MethodPost:
+			if handlers.applicationCreate != nil {
+				handlers.applicationCreate(w, r)
+				return
+			}
+			http.NotFound(w, r)
+
+		case strings.HasPrefix(path, "/api/v3/core/applications/") && strings.HasSuffix(path, "/"):
+			slugPath := strings.TrimPrefix(path, "/api/v3/core/applications/")
+			if slugPath == "" {
+				http.NotFound(w, r)
+				return
+			}
+			switch r.Method {
+			case http.MethodGet:
+				if handlers.applicationRetrieve != nil {
+					handlers.applicationRetrieve(w, r)
+					return
+				}
+				http.NotFound(w, r)
+			case http.MethodPatch:
+				if handlers.applicationPartialUpdate != nil {
+					handlers.applicationPartialUpdate(w, r)
+					return
+				}
+				http.NotFound(w, r)
+			default:
+				http.Error(w, "unexpected method on application instance", http.StatusMethodNotAllowed)
+			}
+
+		case strings.HasPrefix(path, "/api/v3/providers/proxy/") && strings.HasSuffix(path, "/"):
+			idPath := strings.TrimPrefix(path, "/api/v3/providers/proxy/")
+			if idPath == "" {
+				http.NotFound(w, r)
+				return
+			}
+			if r.Method == http.MethodDelete {
+				if handlers.proxyDestroy != nil {
+					handlers.proxyDestroy(w, r)
+					return
+				}
+				http.NotFound(w, r)
+				return
+			}
+			http.Error(w, "unexpected method on proxy instance", http.StatusMethodNotAllowed)
+
+		default:
+			http.NotFound(w, r)
+		}
+	})
+
+	return httptest.NewServer(handler)
+}
+
+func writeJSON(t *testing.T, w http.ResponseWriter, status int, body any) {
+	t.Helper()
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	if err := json.NewEncoder(w).Encode(body); err != nil {
+		t.Fatalf("write JSON response: %v", err)
+	}
+}
+
+func getApplication(t *testing.T, ctrl *Controller, namespace, name string) *v1alpha1.Application {
+	t.Helper()
+
+	got, err := ctrl.applicationClientset.ApplicationV1alpha1().Applications(namespace).Get(
+		context.Background(), name, metav1.GetOptions{},
+	)
+	if err != nil {
+		t.Fatalf("get Application: %v", err)
+	}
+	return got
+}

pkg/controllers/policybinding/controller.go

@@ -0,0 +1,287 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+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 policybinding
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"slices"
+	"strconv"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/kubernetes/scheme"
+	typedcorev1 "k8s.io/client-go/kubernetes/typed/core/v1"
+	"k8s.io/client-go/tools/cache"
+	"k8s.io/client-go/tools/record"
+	"k8s.io/client-go/util/workqueue"
+	"k8s.io/klog/v2"
+
+	v1alpha1 "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/apis/policybinding/v1alpha1"
+	clientset "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned"
+	operatorscheme "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned/scheme"
+	informers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/informers/externalversions/policybinding/v1alpha1"
+	listers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/listers/policybinding/v1alpha1"
+	authentikapi "goauthentik.io/api/v3"
+)
+
+const controllerAgentName = "policybinding-controller"
+
+const (
+	SuccessSynced         = "Synced"
+	ErrResourceExists     = "ErrResourceExists"
+	MessageResourceExists = "Resource %q already exists and is not managed by PolicyBinding"
+	MessageResourceSynced = "PolicyBinding synced successfully"
+	FieldManager          = controllerAgentName
+)
+
+// Finalizers
+const (
+	DeleteAuthentikPolicyBindingFinalizer = "policybinding.t000-n.de/delete-authentik-policybinding"
+)
+
+type Controller struct {
+	kubeclientset          kubernetes.Interface
+	policyBindingClientset clientset.Interface
+	authentik              *authentikapi.APIClient
+
+	policyBindingListener listers.PolicyBindingLister
+	policyBindingSynced   cache.InformerSynced
+
+	workqueue workqueue.TypedRateLimitingInterface[cache.ObjectName]
+	recorder  record.EventRecorder
+}
+
+func NewController(
+	ctx context.Context,
+	kubeclientset kubernetes.Interface,
+	policyBindingClientset clientset.Interface,
+	authentik *authentikapi.APIClient,
+	policyBindingInformer informers.PolicyBindingInformer,
+) *Controller {
+	logger := klog.FromContext(ctx)
+
+	utilruntime.Must(operatorscheme.AddToScheme(scheme.Scheme))
+	logger.V(4).Info("Creating event broadcaster")
+
+	eventBroadcaster := record.NewBroadcaster(record.WithContext(ctx))
+	eventBroadcaster.StartStructuredLogging(0)
+	eventBroadcaster.StartRecordingToSink(&typedcorev1.EventSinkImpl{Interface: kubeclientset.CoreV1().Events("")})
+	recorder := eventBroadcaster.NewRecorder(scheme.Scheme, corev1.EventSource{Component: controllerAgentName})
+	ratelimiter := workqueue.NewTypedMaxOfRateLimiter(
+		workqueue.NewTypedItemExponentialFailureRateLimiter[cache.ObjectName](5*time.Millisecond, 1000*time.Second),
+		&workqueue.TypedBucketRateLimiter[cache.ObjectName]{Limiter: rate.NewLimiter(rate.Limit(50), 300)},
+	)
+
+	c := &Controller{
+		kubeclientset:          kubeclientset,
+		policyBindingClientset: policyBindingClientset,
+		authentik:              authentik,
+		policyBindingListener:  policyBindingInformer.Lister(),
+		policyBindingSynced:    policyBindingInformer.Informer().HasSynced,
+		workqueue:              workqueue.NewTypedRateLimitingQueue(ratelimiter),
+		recorder:               recorder,
+	}
+
+	logger.Info("Setting up event handlers")
+	policyBindingInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+		AddFunc: c.enqueuePolicyBinding,
+		UpdateFunc: func(_, newObj interface{}) {
+			c.enqueuePolicyBinding(newObj)
+		},
+	})
+
+	return c
+}
+
+func (c *Controller) Run(ctx context.Context, workers int) error {
+	defer utilruntime.HandleCrash()
+	defer c.workqueue.ShutDown()
+	logger := klog.FromContext(ctx)
+
+	logger.Info("Starting PolicyBinding controller")
+
+	logger.Info("Waiting for informer caches to sync")
+	if ok := cache.WaitForCacheSync(ctx.Done(), c.policyBindingSynced); !ok {
+		return fmt.Errorf("failed to wait for caches to sync")
+	}
+
+	logger.Info("Starting workers", "count", workers)
+	for i := 0; i < workers; i++ {
+		go wait.UntilWithContext(ctx, c.runWorker, time.Second)
+	}
+
+	logger.Info("Started workers")
+	<-ctx.Done()
+	logger.Info("Shutting down workers")
+	return nil
+}
+
+func (c *Controller) runWorker(ctx context.Context) {
+	for c.processNextWorkItem(ctx) {
+	}
+}
+
+func (c *Controller) processNextWorkItem(ctx context.Context) bool {
+	objRef, shutdown := c.workqueue.Get()
+	logger := klog.FromContext(ctx)
+	if shutdown {
+		return false
+	}
+	defer c.workqueue.Done(objRef)
+
+	err := c.syncHandler(ctx, objRef)
+	if err == nil {
+		c.workqueue.Forget(objRef)
+		logger.Info("Successfully synced", "objectName", objRef)
+		return true
+	}
+	utilruntime.HandleErrorWithContext(ctx, err, "Error syncing; requeuing for later retry", "objectReference", objRef)
+	c.workqueue.AddRateLimited(objRef)
+	return true
+}
+
+func (c *Controller) syncHandler(ctx context.Context, objectRef cache.ObjectName) error {
+	logger := klog.LoggerWithValues(klog.FromContext(ctx), "objectRef", objectRef)
+
+	pb, err := c.policyBindingListener.PolicyBindings(objectRef.Namespace).Get(objectRef.Name)
+	if err != nil {
+		if errors.IsNotFound(err) {
+			logger.V(4).Info("PolicyBinding no longer exists")
+			return nil
+		}
+		return err
+	}
+	logger.V(4).Info("sync PolicyBinding", "name", pb.Name)
+
+	if !pb.ObjectMeta.DeletionTimestamp.IsZero() {
+		logger.Info("Reconciling deletion of PolicyBinding", "name", pb.Name)
+		return c.reconcileDelete(ctx, pb)
+	}
+
+	if pb.Status.PK == "" {
+		logger.Info("Reconciling creation of PolicyBinding", "name", pb.Name)
+		return c.reconcileCreate(ctx, pb)
+	}
+
+	// Check if all finalizers are present. If not, we add them. Same pattern as above, just needs a helper function to check for presence of a finalizer.
+	if !slices.Contains(pb.ObjectMeta.Finalizers, DeleteAuthentikPolicyBindingFinalizer) {
+		logger.Info("Ensuring finalizers are present", "name", pb.Name)
+		return c.ensureFinalizers(ctx, pb)
+	}
+
+	logger.Info("Reconciling update of PolicyBinding", "name", pb.Name)
+	return c.reconcileUpdate(ctx, pb)
+}
+
+func (c *Controller) ensureFinalizers(ctx context.Context, pb *v1alpha1.PolicyBinding) error {
+	pb.ObjectMeta.Finalizers = append(pb.ObjectMeta.Finalizers, DeleteAuthentikPolicyBindingFinalizer)
+	return c.updatePolicyBinding(ctx, pb)
+}
+
+func (c *Controller) reconcileDelete(ctx context.Context, pb *v1alpha1.PolicyBinding) error {
+	pk, err := strconv.ParseInt(pb.Status.PK, 10, 32)
+	if err != nil {
+		return fmt.Errorf("error parsing PK: %v", err)
+	}
+
+	r, err := c.authentik.ProvidersApi.ProvidersProxyDestroy(ctx, int32(pk)).Execute()
+	if err != nil {
+		// This handles an edge-case, where when the ProxyProvider on Authentik has already been deleted, but the finalizer is still present. We just remove the finalizer and return.
+		if r != nil && r.StatusCode != http.StatusNotFound {
+			return fmt.Errorf("error when calling `ProvidersAPI.ProvidersProxyDestroy`: %w with response %v", err, r)
+		}
+	}
+
+	pb.ObjectMeta.Finalizers = slices.Delete(pb.ObjectMeta.Finalizers, slices.Index(pb.ObjectMeta.Finalizers, DeleteAuthentikPolicyBindingFinalizer), 1)
+	return c.updatePolicyBinding(ctx, pb)
+}
+
+func (c *Controller) reconcileUpdate(ctx context.Context, pb *v1alpha1.PolicyBinding) error {
+	_, r, err := c.authentik.PoliciesApi.PoliciesBindingsRetrieve(ctx, pb.Status.PK).Execute()
+	if err != nil {
+		if r != nil && r.StatusCode == http.StatusNotFound {
+			// This handles an edge-case, where when the PolicyBinding on Authentik has been deleted, e.g. by mistake. We just remove the PK and return.
+			// During the next reconciliation, the PolicyBinding will be re-created.
+			pb.Status.PK = ""
+			return c.updatePolicyBindingStatus(ctx, pb)
+		}
+		return fmt.Errorf("error retrieving existing PolicyBinding: %v with response %v", err, r)
+	}
+
+	patchedPolicyBindingRequest := &authentikapi.PatchedPolicyBindingRequest{
+		Policy: *authentikapi.NewNullableString(&pb.Spec.Policy),
+		Group:  *authentikapi.NewNullableString(&pb.Spec.Group),
+		User:   *authentikapi.NewNullableInt32(&pb.Spec.User),
+		Target: &pb.Spec.Target,
+		Order:  &pb.Spec.Order,
+	}
+	resp, r, err := c.authentik.PoliciesApi.PoliciesBindingsPartialUpdate(ctx, pb.Status.PK).PatchedPolicyBindingRequest(*patchedPolicyBindingRequest).Execute()
+	if err != nil {
+		return fmt.Errorf("error when calling `ProvidersAPI.ProvidersProxyPartialUpdate`: %w with response %v", err, r)
+	}
+
+	pb.Status.PK = resp.Pk
+	return c.updatePolicyBindingStatus(ctx, pb)
+}
+
+func (c *Controller) reconcileCreate(ctx context.Context, pb *v1alpha1.PolicyBinding) error {
+	policyBindingRequest := &authentikapi.PolicyBindingRequest{
+		Policy: *authentikapi.NewNullableString(&pb.Spec.Policy),
+		Group:  *authentikapi.NewNullableString(&pb.Spec.Group),
+		User:   *authentikapi.NewNullableInt32(&pb.Spec.User),
+		Target: pb.Spec.Target,
+		Order:  pb.Spec.Order,
+	}
+	resp, r, err := c.authentik.PoliciesApi.PoliciesBindingsCreate(ctx).PolicyBindingRequest(*policyBindingRequest).Execute()
+	if err != nil {
+		return fmt.Errorf("error when calling `PoliciesAPI.PoliciesBindingsCreate`: %w with response %v", err, r)
+	}
+
+	pb.Status.PK = resp.Pk
+	return c.updatePolicyBindingStatus(ctx, pb)
+}
+
+func (c *Controller) enqueuePolicyBinding(obj interface{}) {
+	objectRef, err := cache.ObjectToName(obj)
+	if err != nil {
+		utilruntime.HandleError(err)
+		return
+	}
+	c.workqueue.Add(objectRef)
+}
+
+func (c *Controller) updatePolicyBindingStatus(ctx context.Context, pb *v1alpha1.PolicyBinding) error {
+	pbCopy := pb.DeepCopy()
+	_, err := c.policyBindingClientset.PolicyBindingV1alpha1().PolicyBindings(pbCopy.Namespace).UpdateStatus(ctx, pbCopy, metav1.UpdateOptions{FieldManager: FieldManager})
+	return err
+}
+
+// Update metadata, spec, etc. of the PolicyBinding object.
+func (c *Controller) updatePolicyBinding(ctx context.Context, pb *v1alpha1.PolicyBinding) error {
+	pbCopy := pb.DeepCopy()
+	_, err := c.policyBindingClientset.PolicyBindingV1alpha1().PolicyBindings(pbCopy.Namespace).Update(ctx, pbCopy, metav1.UpdateOptions{FieldManager: FieldManager})
+	return err
+}

pkg/controllers/proxyprovider/controller.go

@@ -0,0 +1,296 @@
+/*
+Copyright 2017 The Kubernetes Authors.
+
+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 proxyprovider
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"slices"
+	"strconv"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/kubernetes/scheme"
+	typedcorev1 "k8s.io/client-go/kubernetes/typed/core/v1"
+	"k8s.io/client-go/tools/cache"
+	"k8s.io/client-go/tools/record"
+	"k8s.io/client-go/util/workqueue"
+	"k8s.io/klog/v2"
+
+	v1alpha1 "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/apis/proxyprovider/v1alpha1"
+	clientset "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned"
+	operatorscheme "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned/scheme"
+	informers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/informers/externalversions/proxyprovider/v1alpha1"
+	listers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/listers/proxyprovider/v1alpha1"
+	authentikapi "goauthentik.io/api/v3"
+)
+
+const controllerAgentName = "proxy-provider-controller"
+
+const (
+	SuccessSynced         = "Synced"
+	ErrResourceExists     = "ErrResourceExists"
+	MessageResourceExists = "Resource %q already exists and is not managed by ProxyProvider"
+	MessageResourceSynced = "ProxyProvider synced successfully"
+	FieldManager          = controllerAgentName
+)
+
+// Finalizers
+const (
+	DeleteAuthentikProxyProviderFinalizer = "proxyprovider.t000-n.de/delete-authentik-proxyprovider"
+)
+
+type Controller struct {
+	kubeclientset          kubernetes.Interface
+	proxyProviderClientset clientset.Interface
+	authentik              *authentikapi.APIClient
+
+	proxyLister listers.ProxyProviderLister
+	proxySynced cache.InformerSynced
+
+	workqueue workqueue.TypedRateLimitingInterface[cache.ObjectName]
+	recorder  record.EventRecorder
+}
+
+func NewController(
+	ctx context.Context,
+	kubeclientset kubernetes.Interface,
+	proxyProviderClientset clientset.Interface,
+	authentik *authentikapi.APIClient,
+	proxyInformer informers.ProxyProviderInformer,
+) *Controller {
+	logger := klog.FromContext(ctx)
+
+	utilruntime.Must(operatorscheme.AddToScheme(scheme.Scheme))
+	logger.V(4).Info("Creating event broadcaster")
+
+	eventBroadcaster := record.NewBroadcaster(record.WithContext(ctx))
+	eventBroadcaster.StartStructuredLogging(0)
+	eventBroadcaster.StartRecordingToSink(&typedcorev1.EventSinkImpl{Interface: kubeclientset.CoreV1().Events("")})
+	recorder := eventBroadcaster.NewRecorder(scheme.Scheme, corev1.EventSource{Component: controllerAgentName})
+	ratelimiter := workqueue.NewTypedMaxOfRateLimiter(
+		workqueue.NewTypedItemExponentialFailureRateLimiter[cache.ObjectName](5*time.Millisecond, 1000*time.Second),
+		&workqueue.TypedBucketRateLimiter[cache.ObjectName]{Limiter: rate.NewLimiter(rate.Limit(50), 300)},
+	)
+
+	c := &Controller{
+		kubeclientset:          kubeclientset,
+		proxyProviderClientset: proxyProviderClientset,
+		authentik:              authentik,
+		proxyLister:            proxyInformer.Lister(),
+		proxySynced:            proxyInformer.Informer().HasSynced,
+		workqueue:              workqueue.NewTypedRateLimitingQueue(ratelimiter),
+		recorder:               recorder,
+	}
+
+	logger.Info("Setting up event handlers")
+	proxyInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
+		AddFunc: c.enqueueProxyProvider,
+		UpdateFunc: func(_, newObj interface{}) {
+			c.enqueueProxyProvider(newObj)
+		},
+	})
+
+	return c
+}
+
+func (c *Controller) Run(ctx context.Context, workers int) error {
+	defer utilruntime.HandleCrash()
+	defer c.workqueue.ShutDown()
+	logger := klog.FromContext(ctx)
+
+	logger.Info("Starting ProxyProvider controller")
+
+	logger.Info("Waiting for informer caches to sync")
+	if ok := cache.WaitForCacheSync(ctx.Done(), c.proxySynced); !ok {
+		return fmt.Errorf("failed to wait for caches to sync")
+	}
+
+	logger.Info("Starting workers", "count", workers)
+	for i := 0; i < workers; i++ {
+		go wait.UntilWithContext(ctx, c.runWorker, time.Second)
+	}
+
+	logger.Info("Started workers")
+	<-ctx.Done()
+	logger.Info("Shutting down workers")
+	return nil
+}
+
+func (c *Controller) runWorker(ctx context.Context) {
+	for c.processNextWorkItem(ctx) {
+	}
+}
+
+func (c *Controller) processNextWorkItem(ctx context.Context) bool {
+	objRef, shutdown := c.workqueue.Get()
+	logger := klog.FromContext(ctx)
+	if shutdown {
+		return false
+	}
+	defer c.workqueue.Done(objRef)
+
+	err := c.syncHandler(ctx, objRef)
+	if err == nil {
+		c.workqueue.Forget(objRef)
+		logger.Info("Successfully synced", "objectName", objRef)
+		return true
+	}
+	utilruntime.HandleErrorWithContext(ctx, err, "Error syncing; requeuing for later retry", "objectReference", objRef)
+	c.workqueue.AddRateLimited(objRef)
+	return true
+}
+
+func (c *Controller) syncHandler(ctx context.Context, objectRef cache.ObjectName) error {
+	logger := klog.LoggerWithValues(klog.FromContext(ctx), "objectRef", objectRef)
+
+	pp, err := c.proxyLister.ProxyProviders(objectRef.Namespace).Get(objectRef.Name)
+	if err != nil {
+		if errors.IsNotFound(err) {
+			logger.V(4).Info("ProxyProvider no longer exists")
+			return nil
+		}
+		return err
+	}
+	logger.V(4).Info("sync ProxyProvider", "name", pp.Name)
+
+	if !pp.ObjectMeta.DeletionTimestamp.IsZero() {
+		logger.Info("Reconciling deletion of ProxyProvider", "name", pp.Name)
+		return c.reconcileDelete(ctx, pp)
+	}
+
+	if pp.Status.PK == "" {
+		logger.Info("Reconciling creation of ProxyProvider", "name", pp.Name)
+		return c.reconcileCreate(ctx, pp)
+	}
+
+	// Check if all finalizers are present. If not, we add them. Same pattern as above, just needs a helper function to check for presence of a finalizer.
+	if !slices.Contains(pp.ObjectMeta.Finalizers, DeleteAuthentikProxyProviderFinalizer) {
+		logger.Info("Ensuring finalizers are present", "name", pp.Name)
+		return c.ensureFinalizers(ctx, pp)
+	}
+
+	logger.Info("Reconciling update of ProxyProvider", "name", pp.Name)
+	return c.reconcileUpdate(ctx, pp)
+}
+
+func (c *Controller) ensureFinalizers(ctx context.Context, pp *v1alpha1.ProxyProvider) error {
+	pp.ObjectMeta.Finalizers = append(pp.ObjectMeta.Finalizers, DeleteAuthentikProxyProviderFinalizer)
+	return c.updateProxyProvider(ctx, pp)
+}
+
+func (c *Controller) reconcileDelete(ctx context.Context, pp *v1alpha1.ProxyProvider) error {
+	pk, err := strconv.ParseInt(pp.Status.PK, 10, 32)
+	if err != nil {
+		return fmt.Errorf("error parsing PK: %v", err)
+	}
+
+	r, err := c.authentik.ProvidersApi.ProvidersProxyDestroy(ctx, int32(pk)).Execute()
+	if err != nil {
+		// This handles an edge-case, where when the ProxyProvider on Authentik has already been deleted, but the finalizer is still present. We just remove the finalizer and return.
+		if r != nil && r.StatusCode != http.StatusNotFound {
+			return fmt.Errorf("error when calling `ProvidersAPI.ProvidersProxyDestroy`: %w with response %v", err, r)
+		}
+	}
+
+	pp.ObjectMeta.Finalizers = slices.Delete(pp.ObjectMeta.Finalizers, slices.Index(pp.ObjectMeta.Finalizers, DeleteAuthentikProxyProviderFinalizer), 1)
+	return c.updateProxyProvider(ctx, pp)
+}
+
+func (c *Controller) reconcileUpdate(ctx context.Context, pp *v1alpha1.ProxyProvider) error {
+	// We retrieve the existing PP from the API by slug.
+	pk, err := strconv.ParseInt(pp.Status.PK, 10, 32)
+	if err != nil {
+		return fmt.Errorf("error parsing PK: %v", err)
+	}
+	_, r, err := c.authentik.ProvidersApi.ProvidersAllRetrieve(ctx, int32(pk)).Execute()
+	if err != nil {
+		if r != nil && r.StatusCode == http.StatusNotFound {
+			// This handles an edge-case, where when the PorxyProvider on Authentik has been deleted, e.g. by mistake. We just remove the PK and return.
+			// During the next reconciliation, the ProxyProvider will be re-created.
+			pp.Status.PK = ""
+			return c.updateProxyProviderStatus(ctx, pp)
+		}
+		return fmt.Errorf("error retrieving existing ProxyProvider: %v with response %v", err, r)
+	}
+
+	proxyProviderRequest := &authentikapi.PatchedProxyProviderRequest{
+		Name:              &pp.Spec.Name,
+		AuthorizationFlow: &pp.Spec.AuthorizationFlow,
+		InvalidationFlow:  &pp.Spec.InvalidationFlow,
+		ExternalHost:      &pp.Spec.ExternalHost,
+		Mode:              authentikapi.PROXYMODE_FORWARD_SINGLE.Ptr(),
+	}
+	resp, r, err := c.authentik.ProvidersApi.ProvidersProxyPartialUpdate(ctx, int32(pk)).PatchedProxyProviderRequest(*proxyProviderRequest).Execute()
+	if err != nil {
+		return fmt.Errorf("error when calling `ProvidersAPI.ProvidersProxyPartialUpdate`: %w with response %v", err, r)
+	}
+
+	pp.Status.PK = strconv.Itoa(int(resp.Pk))
+
+	return c.updateProxyProviderStatus(ctx, pp)
+}
+
+func (c *Controller) reconcileCreate(ctx context.Context, pp *v1alpha1.ProxyProvider) error {
+	proxyProviderRequest := &authentikapi.ProxyProviderRequest{
+		Name:              pp.Spec.Name,
+		AuthorizationFlow: pp.Spec.AuthorizationFlow,
+		InvalidationFlow:  pp.Spec.InvalidationFlow,
+		ExternalHost:      pp.Spec.ExternalHost,
+		Mode:              authentikapi.PROXYMODE_FORWARD_SINGLE.Ptr(),
+	}
+	resp, r, err := c.authentik.ProvidersApi.ProvidersProxyCreate(ctx).ProxyProviderRequest(*proxyProviderRequest).Execute()
+	if err != nil {
+		return fmt.Errorf("error when calling `ProvidersAPI.ProvidersProxyCreate`: %w with response %v", err, r)
+	}
+
+	pp.Status.PK = strconv.Itoa(int(resp.Pk))
+	return c.updateProxyProviderStatus(ctx, pp)
+}
+
+func (c *Controller) enqueueProxyProvider(obj interface{}) {
+	objectRef, err := cache.ObjectToName(obj)
+	if err != nil {
+		utilruntime.HandleError(err)
+		return
+	}
+	c.workqueue.Add(objectRef)
+}
+
+func (c *Controller) updateProxyProviderStatus(ctx context.Context, pp *v1alpha1.ProxyProvider) error {
+	ppCopy := pp.DeepCopy()
+	_, err := c.proxyProviderClientset.ProxyproviderV1alpha1().ProxyProviders(ppCopy.Namespace).UpdateStatus(ctx, ppCopy, metav1.UpdateOptions{FieldManager: FieldManager})
+	return err
+}
+
+// Update metadata, spec, etc. of the ProxyProvider object.
+func (c *Controller) updateProxyProvider(ctx context.Context, pp *v1alpha1.ProxyProvider) error {
+	ppCopy := pp.DeepCopy()
+	_, err := c.proxyProviderClientset.ProxyproviderV1alpha1().ProxyProviders(ppCopy.Namespace).Update(ctx, ppCopy, metav1.UpdateOptions{FieldManager: FieldManager})
+	if err != nil {
+		return fmt.Errorf("error updating ProxyProvider metadata: %v", err)
+	}
+	return nil
+}

pkg/controllers/proxyprovider/controller_test.go

@@ -0,0 +1,385 @@
+// AI generated tests and not yet reviewed.
+package proxyprovider
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"slices"
+	"strings"
+	"testing"
+
+	v1alpha1 "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/apis/proxyprovider/v1alpha1"
+	operatorfake "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/clientset/versioned/fake"
+	operatorinformers "gitea.t000-n.de/t.behrendt/authentik-kubernetes-operator/pkg/generated/informers/externalversions"
+	authentikapi "goauthentik.io/api/v3"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/client-go/kubernetes/fake"
+	"k8s.io/client-go/tools/cache"
+)
+
+func TestController_syncHandler_create(t *testing.T) {
+	const wantPK = 42
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		proxyCreate: func(w http.ResponseWriter, _ *http.Request) {
+			writeJSON(t, w, http.StatusCreated, map[string]any{"pk": wantPK})
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, testProxyProvider(), server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: "default", Name: "test-pp"})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getProxyProvider(t, ctrl, "default", "test-pp")
+	if got.Status.PK != "42" {
+		t.Fatalf("status.pk = %q, want 42", got.Status.PK)
+	}
+}
+
+func TestController_syncHandler_ensureFinalizers(t *testing.T) {
+	pp := testProxyProvider()
+	pp.Status.PK = "42"
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, pp, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: pp.Namespace, Name: pp.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getProxyProvider(t, ctrl, pp.Namespace, pp.Name)
+	if !slices.Contains(got.Finalizers, DeleteAuthentikProxyProviderFinalizer) {
+		t.Fatalf("finalizers = %v, want %q", got.Finalizers, DeleteAuthentikProxyProviderFinalizer)
+	}
+}
+
+func TestController_syncHandler_update(t *testing.T) {
+	pp := testProxyProvider()
+	pp.Status.PK = "42"
+	pp.Finalizers = []string{DeleteAuthentikProxyProviderFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		allRetrieve: func(w http.ResponseWriter, _ *http.Request) {
+			writeJSON(t, w, http.StatusOK, map[string]any{"pk": 42})
+		},
+		proxyPartialUpdate: func(w http.ResponseWriter, _ *http.Request) {
+			writeJSON(t, w, http.StatusOK, map[string]any{"pk": 42})
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, pp, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: pp.Namespace, Name: pp.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getProxyProvider(t, ctrl, pp.Namespace, pp.Name)
+	if got.Status.PK != "42" {
+		t.Fatalf("status.pk = %q, want 42", got.Status.PK)
+	}
+}
+
+func TestController_syncHandler_update_providerNotFound(t *testing.T) {
+	pp := testProxyProvider()
+	pp.Status.PK = "42"
+	pp.Finalizers = []string{DeleteAuthentikProxyProviderFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		allRetrieve: func(w http.ResponseWriter, _ *http.Request) {
+			http.NotFound(w, nil)
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, pp, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: pp.Namespace, Name: pp.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getProxyProvider(t, ctrl, pp.Namespace, pp.Name)
+	if got.Status.PK != "" {
+		t.Fatalf("status.pk = %q, want empty after provider not found", got.Status.PK)
+	}
+}
+
+func TestController_syncHandler_delete(t *testing.T) {
+	now := metav1.Now()
+	pp := testProxyProvider()
+	pp.Status.PK = "42"
+	pp.DeletionTimestamp = &now
+	pp.Finalizers = []string{DeleteAuthentikProxyProviderFinalizer}
+
+	var destroyCalled bool
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		proxyDestroy: func(w http.ResponseWriter, r *http.Request) {
+			destroyCalled = true
+			if r.Method != http.MethodDelete {
+				t.Errorf("destroy method = %s, want DELETE", r.Method)
+			}
+			w.WriteHeader(http.StatusNoContent)
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, pp, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: pp.Namespace, Name: pp.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+	if !destroyCalled {
+		t.Fatal("expected Authentik destroy call")
+	}
+
+	got := getProxyProvider(t, ctrl, pp.Namespace, pp.Name)
+	if slices.Contains(got.Finalizers, DeleteAuthentikProxyProviderFinalizer) {
+		t.Fatalf("finalizers = %v, want finalizer removed", got.Finalizers)
+	}
+}
+
+func TestController_syncHandler_delete_providerAlreadyGone(t *testing.T) {
+	now := metav1.Now()
+	pp := testProxyProvider()
+	pp.Status.PK = "42"
+	pp.DeletionTimestamp = &now
+	pp.Finalizers = []string{DeleteAuthentikProxyProviderFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{
+		proxyDestroy: func(w http.ResponseWriter, _ *http.Request) {
+			http.NotFound(w, nil)
+		},
+	})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, pp, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: pp.Namespace, Name: pp.Name})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v", err)
+	}
+
+	got := getProxyProvider(t, ctrl, pp.Namespace, pp.Name)
+	if slices.Contains(got.Finalizers, DeleteAuthentikProxyProviderFinalizer) {
+		t.Fatalf("finalizers = %v, want finalizer removed after 404", got.Finalizers)
+	}
+}
+
+func TestController_syncHandler_notFound(t *testing.T) {
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, nil, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: "default", Name: "missing"})
+	if err != nil {
+		t.Fatalf("syncHandler() error = %v, want nil for missing object", err)
+	}
+}
+
+func TestController_syncHandler_invalidPK(t *testing.T) {
+	pp := testProxyProvider()
+	pp.Status.PK = "not-a-number"
+	pp.Finalizers = []string{DeleteAuthentikProxyProviderFinalizer}
+
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, ctx, cancel := newTestController(t, pp, server.URL)
+	t.Cleanup(cancel)
+
+	err := ctrl.syncHandler(ctx, cache.ObjectName{Namespace: pp.Namespace, Name: pp.Name})
+	if err == nil {
+		t.Fatal("syncHandler() error = nil, want parse error")
+	}
+	if !strings.Contains(err.Error(), "error parsing PK") {
+		t.Fatalf("syncHandler() error = %v, want PK parse error", err)
+	}
+}
+
+func TestController_enqueueProxyProvider(t *testing.T) {
+	server := newAuthentikTestServer(t, authentikTestHandlers{})
+	t.Cleanup(server.Close)
+
+	ctrl, _, cancel := newTestController(t, testProxyProvider(), server.URL)
+	t.Cleanup(cancel)
+
+	ctrl.enqueueProxyProvider(testProxyProvider())
+
+	if ctrl.workqueue.Len() != 1 {
+		t.Fatalf("workqueue length = %d, want 1", ctrl.workqueue.Len())
+	}
+}
+
+// --- test helpers ---
+
+func testProxyProvider() *v1alpha1.ProxyProvider {
+	return &v1alpha1.ProxyProvider{
+		TypeMeta: metav1.TypeMeta{
+			APIVersion: v1alpha1.SchemeGroupVersion.String(),
+			Kind:       "ProxyProvider",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "test-pp",
+			Namespace: "default",
+		},
+		Spec: v1alpha1.ProxyProviderSpec{
+			Name:              "my-app",
+			AuthorizationFlow: "flow-auth",
+			InvalidationFlow:  "flow-invalidate",
+			ExternalHost:      "https://app.example.com",
+		},
+	}
+}
+
+func newTestController(t *testing.T, pp *v1alpha1.ProxyProvider, authentikURL string) (*Controller, context.Context, context.CancelFunc) {
+	t.Helper()
+	ctx, cancel := context.WithCancel(context.Background())
+	ctrl, _, stop := newTestControllerWithContext(t, ctx, pp, authentikURL)
+	return ctrl, ctx, func() {
+		cancel()
+		stop()
+	}
+}
+
+func newTestControllerWithContext(t *testing.T, ctx context.Context, pp *v1alpha1.ProxyProvider, authentikURL string) (*Controller, context.Context, func()) {
+	t.Helper()
+
+	authentikClient := newAuthentikAPIClientForTest(t, authentikURL)
+
+	var objects []runtime.Object
+	if pp != nil {
+		objects = append(objects, pp)
+	}
+	proxyClient := operatorfake.NewSimpleClientset(objects...)
+
+	informerFactory := operatorinformers.NewSharedInformerFactory(proxyClient, 0)
+	proxyInformer := informerFactory.Proxyprovider().V1alpha1().ProxyProviders()
+
+	ctrl := NewController(ctx, fake.NewClientset(), proxyClient, authentikClient, proxyInformer)
+
+	informerFactory.Start(ctx.Done())
+	for informerType, synced := range informerFactory.WaitForCacheSync(ctx.Done()) {
+		if !synced {
+			t.Fatalf("informer %v failed to sync", informerType)
+		}
+	}
+
+	return ctrl, ctx, func() {}
+}
+
+func newAuthentikAPIClientForTest(t *testing.T, serverURL string) *authentikapi.APIClient {
+	t.Helper()
+
+	u, err := url.Parse(serverURL)
+	if err != nil {
+		t.Fatalf("parse server URL: %v", err)
+	}
+
+	cfg := authentikapi.NewConfiguration()
+	cfg.Scheme = u.Scheme
+	cfg.Host = u.Host
+
+	return authentikapi.NewAPIClient(cfg)
+}
+
+type authentikTestHandlers struct {
+	proxyCreate        http.HandlerFunc
+	proxyDestroy       http.HandlerFunc
+	proxyPartialUpdate http.HandlerFunc
+	allRetrieve        http.HandlerFunc
+}
+
+func newAuthentikTestServer(t *testing.T, handlers authentikTestHandlers) *httptest.Server {
+	t.Helper()
+
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		path := r.URL.Path
+
+		switch {
+		case path == "/api/v3/providers/proxy/" && r.Method == http.MethodPost:
+			if handlers.proxyCreate != nil {
+				handlers.proxyCreate(w, r)
+				return
+			}
+			http.NotFound(w, r)
+
+		case strings.HasPrefix(path, "/api/v3/providers/proxy/") && strings.HasSuffix(path, "/"):
+			idPath := strings.TrimPrefix(path, "/api/v3/providers/proxy/")
+			if idPath == "" {
+				http.NotFound(w, r)
+				return
+			}
+			switch r.Method {
+			case http.MethodDelete:
+				if handlers.proxyDestroy != nil {
+					handlers.proxyDestroy(w, r)
+					return
+				}
+				http.NotFound(w, r)
+			case http.MethodPatch:
+				if handlers.proxyPartialUpdate != nil {
+					handlers.proxyPartialUpdate(w, r)
+					return
+				}
+				http.NotFound(w, r)
+			default:
+				http.Error(w, "unexpected method on proxy instance", http.StatusMethodNotAllowed)
+			}
+
+		case strings.HasPrefix(path, "/api/v3/providers/all/") && strings.HasSuffix(path, "/"):
+			if r.Method == http.MethodGet && handlers.allRetrieve != nil {
+				handlers.allRetrieve(w, r)
+				return
+			}
+			http.NotFound(w, r)
+
+		default:
+			http.NotFound(w, r)
+		}
+	})
+
+	return httptest.NewServer(handler)
+}
+
+func writeJSON(t *testing.T, w http.ResponseWriter, status int, body any) {
+	t.Helper()
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	if err := json.NewEncoder(w).Encode(body); err != nil {
+		t.Fatalf("write JSON response: %v", err)
+	}
+}
+
+func getProxyProvider(t *testing.T, ctrl *Controller, namespace, name string) *v1alpha1.ProxyProvider {
+	t.Helper()
+
+	got, err := ctrl.proxyProviderClientset.ProxyproviderV1alpha1().ProxyProviders(namespace).Get(
+		context.Background(), name, metav1.GetOptions{},
+	)
+	if err != nil {
+		t.Fatalf("get ProxyProvider: %v", err)
+	}
+	return got
+}