/*
Copyright 2021 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 webhook_test

import (
	"context"
	"crypto/tls"
	"errors"
	"net"
	"net/http"
	"path/filepath"
	"strconv"
	"time"

	. "github.com/onsi/ginkgo"
	. "github.com/onsi/gomega"
	appsv1 "k8s.io/api/apps/v1"
	corev1 "k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/client-go/kubernetes/scheme"
	"sigs.k8s.io/controller-runtime/pkg/certwatcher"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/manager"
	"sigs.k8s.io/controller-runtime/pkg/webhook"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
	"sigs.k8s.io/controller-runtime/pkg/webhook/admission/admissiontest"
)

var _ = Describe("Webhook", func() {
	var c client.Client
	var obj *appsv1.Deployment
	BeforeEach(func() {
		Expect(cfg).NotTo(BeNil())
		var err error
		c, err = client.New(cfg, client.Options{})
		Expect(err).NotTo(HaveOccurred())

		obj = &appsv1.Deployment{
			TypeMeta: metav1.TypeMeta{
				APIVersion: "apps/v1",
				Kind:       "Deployment",
			},
			ObjectMeta: metav1.ObjectMeta{
				Name:      "test-deployment",
				Namespace: "default",
			},
			Spec: appsv1.DeploymentSpec{
				Selector: &metav1.LabelSelector{
					MatchLabels: map[string]string{"foo": "bar"},
				},
				Template: corev1.PodTemplateSpec{
					ObjectMeta: metav1.ObjectMeta{Labels: map[string]string{"foo": "bar"}},
					Spec: corev1.PodSpec{
						Containers: []corev1.Container{
							{
								Name:  "nginx",
								Image: "nginx",
							},
						},
					},
				},
			},
		}
	})
	Context("when running a webhook server with a manager", func() {
		It("should reject create request for webhook that rejects all requests", func() {
			m, err := manager.New(cfg, manager.Options{
				Port:    testenv.WebhookInstallOptions.LocalServingPort,
				Host:    testenv.WebhookInstallOptions.LocalServingHost,
				CertDir: testenv.WebhookInstallOptions.LocalServingCertDir,
			}) // we need manager here just to leverage manager.SetFields
			Expect(err).NotTo(HaveOccurred())
			server := m.GetWebhookServer()
			server.Register("/failing", &webhook.Admission{Handler: &rejectingValidator{}})

			ctx, cancel := context.WithCancel(context.Background())
			go func() {
				err = server.Start(ctx)
				Expect(err).NotTo(HaveOccurred())
			}()

			Eventually(func() bool {
				err = c.Create(context.TODO(), obj)
				return apierrors.ReasonForError(err) == metav1.StatusReason("Always denied")
			}, 1*time.Second).Should(BeTrue())

			cancel()
		})
		It("should reject create request for multi-webhook that rejects all requests", func() {
			m, err := manager.New(cfg, manager.Options{
				Port:    testenv.WebhookInstallOptions.LocalServingPort,
				Host:    testenv.WebhookInstallOptions.LocalServingHost,
				CertDir: testenv.WebhookInstallOptions.LocalServingCertDir,
			}) // we need manager here just to leverage manager.SetFields
			Expect(err).NotTo(HaveOccurred())
			server := m.GetWebhookServer()
			server.Register("/failing", &webhook.Admission{Handler: admission.MultiValidatingHandler(&rejectingValidator{})})

			ctx, cancel := context.WithCancel(context.Background())
			go func() {
				err = server.Start(ctx)
				Expect(err).NotTo(HaveOccurred())
			}()

			Eventually(func() bool {
				err = c.Create(context.TODO(), obj)
				return apierrors.ReasonForError(err) == metav1.StatusReason("Always denied")
			}, 1*time.Second).Should(BeTrue())

			cancel()
		})
	})
	Context("when running a webhook server without a manager", func() {
		It("should reject create request for webhook that rejects all requests", func() {
			server := webhook.Server{
				Port:    testenv.WebhookInstallOptions.LocalServingPort,
				Host:    testenv.WebhookInstallOptions.LocalServingHost,
				CertDir: testenv.WebhookInstallOptions.LocalServingCertDir,
			}
			server.Register("/failing", &webhook.Admission{Handler: &rejectingValidator{}})

			ctx, cancel := context.WithCancel(context.Background())
			go func() {
				err := server.StartStandalone(ctx, scheme.Scheme)
				Expect(err).NotTo(HaveOccurred())
			}()

			Eventually(func() bool {
				err := c.Create(context.TODO(), obj)
				return apierrors.ReasonForError(err) == metav1.StatusReason("Always denied")
			}, 1*time.Second).Should(BeTrue())

			cancel()
		})
	})
	Context("when running a standalone webhook", func() {
		It("should reject create request for webhook that rejects all requests", func() {
			ctx, cancel := context.WithCancel(context.Background())

			By("generating the TLS config")
			certPath := filepath.Join(testenv.WebhookInstallOptions.LocalServingCertDir, "tls.crt")
			keyPath := filepath.Join(testenv.WebhookInstallOptions.LocalServingCertDir, "tls.key")

			certWatcher, err := certwatcher.New(certPath, keyPath)
			Expect(err).NotTo(HaveOccurred())
			go func() {
				Expect(certWatcher.Start(ctx)).NotTo(HaveOccurred())
			}()

			cfg := &tls.Config{
				NextProtos:     []string{"h2"},
				GetCertificate: certWatcher.GetCertificate,
				MinVersion:     tls.VersionTLS12,
			}

			By("generating the listener")
			listener, err := tls.Listen("tcp",
				net.JoinHostPort(testenv.WebhookInstallOptions.LocalServingHost,
					strconv.Itoa(testenv.WebhookInstallOptions.LocalServingPort)), cfg)
			Expect(err).NotTo(HaveOccurred())

			By("creating and registering the standalone webhook")
			hook, err := admission.StandaloneWebhook(admission.ValidatingWebhookFor(
				&admissiontest.FakeValidator{
					ErrorToReturn: errors.New("Always denied"),
					GVKToReturn:   schema.GroupVersionKind{Group: "apps", Version: "v1", Kind: "Deployment"},
				}), admission.StandaloneOptions{})
			Expect(err).NotTo(HaveOccurred())
			http.Handle("/failing", hook)

			By("running the http server")
			srv := &http.Server{}
			go func() {
				idleConnsClosed := make(chan struct{})
				go func() {
					<-ctx.Done()
					Expect(srv.Shutdown(context.Background())).NotTo(HaveOccurred())
					close(idleConnsClosed)
				}()
				_ = srv.Serve(listener)
				<-idleConnsClosed
			}()

			Eventually(func() bool {
				err = c.Create(context.TODO(), obj)
				return apierrors.ReasonForError(err) == metav1.StatusReason("Always denied")
			}, 1*time.Second).Should(BeTrue())

			cancel()
		})
	})
})

type rejectingValidator struct {
	d *admission.Decoder
}

func (v *rejectingValidator) InjectDecoder(d *admission.Decoder) error {
	v.d = d
	return nil
}

func (v *rejectingValidator) Handle(ctx context.Context, req admission.Request) admission.Response {
	var obj appsv1.Deployment
	if err := v.d.Decode(req, &obj); err != nil {
		return admission.Denied(err.Error())
	}
	return admission.Denied("Always denied")
}