/*
Copyright 2017 The Kubernetes Authors.
Copyright 2020 Authors of Arktos - file modified.

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 apiserver

import (
	"fmt"
	"net/http"
	"path"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"github.com/go-openapi/spec"
	"github.com/go-openapi/strfmt"
	"github.com/go-openapi/validate"

	"k8s.io/apiextensions-apiserver/pkg/apis/apiextensions"
	"k8s.io/apiextensions-apiserver/pkg/apiserver/conversion"
	structuralschema "k8s.io/apiextensions-apiserver/pkg/apiserver/schema"
	structuraldefaulting "k8s.io/apiextensions-apiserver/pkg/apiserver/schema/defaulting"
	schemaobjectmeta "k8s.io/apiextensions-apiserver/pkg/apiserver/schema/objectmeta"
	structuralpruning "k8s.io/apiextensions-apiserver/pkg/apiserver/schema/pruning"
	apiservervalidation "k8s.io/apiextensions-apiserver/pkg/apiserver/validation"
	informers "k8s.io/apiextensions-apiserver/pkg/client/informers/internalversion/apiextensions/internalversion"
	listers "k8s.io/apiextensions-apiserver/pkg/client/listers/apiextensions/internalversion"
	"k8s.io/apiextensions-apiserver/pkg/controller/establish"
	"k8s.io/apiextensions-apiserver/pkg/controller/finalizer"
	"k8s.io/apiextensions-apiserver/pkg/controller/openapi/builder"
	"k8s.io/apiextensions-apiserver/pkg/crdserverscheme"
	apiextensionsfeatures "k8s.io/apiextensions-apiserver/pkg/features"
	"k8s.io/apiextensions-apiserver/pkg/registry/customresource"
	"k8s.io/apiextensions-apiserver/pkg/registry/customresource/tableconvertor"

	apiequality "k8s.io/apimachinery/pkg/api/equality"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/runtime/serializer"
	"k8s.io/apimachinery/pkg/runtime/serializer/json"
	"k8s.io/apimachinery/pkg/runtime/serializer/protobuf"
	"k8s.io/apimachinery/pkg/runtime/serializer/versioning"
	"k8s.io/apimachinery/pkg/types"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/sets"
	utilwaitgroup "k8s.io/apimachinery/pkg/util/waitgroup"
	"k8s.io/apiserver/pkg/admission"
	"k8s.io/apiserver/pkg/authorization/authorizer"
	apifilters "k8s.io/apiserver/pkg/endpoints/filters"
	"k8s.io/apiserver/pkg/endpoints/handlers"
	"k8s.io/apiserver/pkg/endpoints/handlers/fieldmanager"
	"k8s.io/apiserver/pkg/endpoints/metrics"
	apirequest "k8s.io/apiserver/pkg/endpoints/request"
	"k8s.io/apiserver/pkg/features"
	"k8s.io/apiserver/pkg/registry/generic"
	genericregistry "k8s.io/apiserver/pkg/registry/generic/registry"
	genericfilters "k8s.io/apiserver/pkg/server/filters"
	"k8s.io/apiserver/pkg/storage/storagebackend"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	utilopenapi "k8s.io/apiserver/pkg/util/openapi"
	"k8s.io/apiserver/pkg/util/webhook"
	"k8s.io/client-go/scale"
	"k8s.io/client-go/scale/scheme/autoscalingv1"
	"k8s.io/client-go/tools/cache"
	"k8s.io/klog"
	"k8s.io/kube-openapi/pkg/util/proto"
)

// crdHandler serves the `/apis` endpoint.
// This is registered as a filter so that it never collides with any explicitly registered endpoints
type crdHandler struct {
	versionDiscoveryHandler *versionDiscoveryHandler
	groupDiscoveryHandler   *groupDiscoveryHandler

	customStorageLock sync.Mutex
	// customStorage contains a crdStorageMap
	// atomic.Value has a very good read performance compared to sync.RWMutex
	// see https://gist.github.com/dim/152e6bf80e1384ea72e17ac717a5000a
	// which is suited for most read and rarely write cases
	customStorage atomic.Value

	crdLister listers.CustomResourceDefinitionLister

	delegate          http.Handler
	restOptionsGetter generic.RESTOptionsGetter
	admission         admission.Interface

	establishingController *establish.EstablishingController

	// MasterCount is used to implement sleep to improve
	// CRD establishing process for HA clusters.
	masterCount int

	converterFactory *conversion.CRConverterFactory

	// so that we can do create on update.
	authorizer authorizer.Authorizer

	// request timeout we should delay storage teardown for
	requestTimeout time.Duration

	// minRequestTimeout applies to CR's list/watch calls
	minRequestTimeout time.Duration

	// staticOpenAPISpec is used as a base for the schema of CR's for the
	// purpose of managing fields, it is how CR handlers get the structure
	// of TypeMeta and ObjectMeta
	staticOpenAPISpec *spec.Swagger
}

// crdInfo stores enough information to serve the storage for the custom resource
type crdInfo struct {
	// spec and acceptedNames are used to compare against if a change is made on a CRD. We only update
	// the storage if one of these changes.
	spec          *apiextensions.CustomResourceDefinitionSpec
	acceptedNames *apiextensions.CustomResourceDefinitionNames

	// Storage per version
	storages map[string]customresource.CustomResourceStorage

	// Request scope per version
	requestScopes map[string]*handlers.RequestScope

	// Scale scope per version
	scaleRequestScopes map[string]*handlers.RequestScope

	// Status scope per version
	statusRequestScopes map[string]*handlers.RequestScope

	// storageVersion is the CRD version used when storing the object in etcd.
	storageVersion string

	waitGroup *utilwaitgroup.SafeWaitGroup
}

// crdStorageMap goes from customresourcedefinition to its storage
type crdStorageMap map[types.UID]*crdInfo

func NewCustomResourceDefinitionHandler(
	versionDiscoveryHandler *versionDiscoveryHandler,
	groupDiscoveryHandler *groupDiscoveryHandler,
	crdInformer informers.CustomResourceDefinitionInformer,
	delegate http.Handler,
	restOptionsGetter generic.RESTOptionsGetter,
	admission admission.Interface,
	establishingController *establish.EstablishingController,
	serviceResolver webhook.ServiceResolver,
	authResolverWrapper webhook.AuthenticationInfoResolverWrapper,
	masterCount int,
	authorizer authorizer.Authorizer,
	requestTimeout time.Duration,
	minRequestTimeout time.Duration,
	staticOpenAPISpec *spec.Swagger) (*crdHandler, error) {
	ret := &crdHandler{
		versionDiscoveryHandler: versionDiscoveryHandler,
		groupDiscoveryHandler:   groupDiscoveryHandler,
		customStorage:           atomic.Value{},
		crdLister:               crdInformer.Lister(),
		delegate:                delegate,
		restOptionsGetter:       restOptionsGetter,
		admission:               admission,
		establishingController:  establishingController,
		masterCount:             masterCount,
		authorizer:              authorizer,
		requestTimeout:          requestTimeout,
		minRequestTimeout:       minRequestTimeout,
		staticOpenAPISpec:       staticOpenAPISpec,
	}
	crdInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		UpdateFunc: ret.updateCustomResourceDefinition,
		DeleteFunc: func(obj interface{}) {
			ret.removeDeadStorage()
		},
	})
	crConverterFactory, err := conversion.NewCRConverterFactory(serviceResolver, authResolverWrapper)
	if err != nil {
		return nil, err
	}
	ret.converterFactory = crConverterFactory

	ret.customStorage.Store(crdStorageMap{})

	return ret, nil
}

// watches are expected to handle storage disruption gracefully,
// both on the server-side (by terminating the watch connection)
// and on the client side (by restarting the watch)
var longRunningFilter = genericfilters.BasicLongRunningRequestCheck(sets.NewString("watch"), sets.NewString())

// possiblyAcrossAllNamespacesVerbs contains those verbs which can be per-namespace and across all
// namespaces for namespaces resources. I.e. for these an empty namespace in the requestInfo is fine.
var possiblyAcrossAllNamespacesVerbs = sets.NewString("list", "watch")

func (r *crdHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	ctx := req.Context()
	req, _ = apifilters.SetShortPathRequestTenant(req)
	requestInfo, _ := apirequest.RequestInfoFrom(ctx)

	crdTenant := requestInfo.Tenant
	// SetShortPathRequestTenant does not update the tenant in a short-path request if it is a system-user request,
	// as it may be an operation across all tenants. Also in some integration tests, the tenant in the requestInfo is not set.
	// However, if code hits here, we know it is NOT a request across multiple tenants,
	// so we can set the tenant here.
	if crdTenant == metav1.TenantNone {
		crdTenant = metav1.TenantSystem
	}

	if !requestInfo.IsResourceRequest {
		pathParts := splitPath(requestInfo.Path)
		// only match /apis/<group>/<version>
		// only registered under /apis
		if len(pathParts) == 3 {
			r.versionDiscoveryHandler.ServeHTTP(w, req)
			return
		}
		// only match /apis/<group>
		if len(pathParts) == 2 {
			r.groupDiscoveryHandler.ServeHTTP(w, req)
			return
		}

		r.delegate.ServeHTTP(w, req)
		return
	}

	crdName := requestInfo.Resource + "." + requestInfo.APIGroup
	crd, err := r.crdLister.CustomResourceDefinitionsWithMultiTenancy(crdTenant).GetAccessibleCrd(crdName)
	if apierrors.IsNotFound(err) {
		r.delegate.ServeHTTP(w, req)
		return
	}
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	// if the scope in the CRD and the scope in request differ (with exception of the verbs in possiblyAcrossAllNamespacesVerbs
	// for namespaced resources), pass request to the delegate, which is supposed to lead to a 404.
	namespacedCRD, namespacedReq := crd.Spec.Scope == apiextensions.NamespaceScoped, len(requestInfo.Namespace) > 0
	if !namespacedCRD && namespacedReq {
		r.delegate.ServeHTTP(w, req)
		return
	}
	if namespacedCRD && !namespacedReq && !possiblyAcrossAllNamespacesVerbs.Has(requestInfo.Verb) {
		r.delegate.ServeHTTP(w, req)
		return
	}

	if !apiextensions.HasServedCRDVersion(crd, requestInfo.APIVersion) {
		r.delegate.ServeHTTP(w, req)
		return
	}

	// There is a small chance that a CRD is being served because NamesAccepted condition is true,
	// but it becomes "unserved" because another names update leads to a conflict
	// and EstablishingController wasn't fast enough to put the CRD into the Established condition.
	// We accept this as the problem is small and self-healing.
	if !apiextensions.IsCRDConditionTrue(crd, apiextensions.NamesAccepted) &&
		!apiextensions.IsCRDConditionTrue(crd, apiextensions.Established) {
		r.delegate.ServeHTTP(w, req)
		return
	}

	terminating := apiextensions.IsCRDConditionTrue(crd, apiextensions.Terminating)

	crdInfo, err := r.getOrCreateServingInfoFor(crd)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	verb := strings.ToUpper(requestInfo.Verb)
	resource := requestInfo.Resource
	subresource := requestInfo.Subresource
	scope := metrics.CleanScope(requestInfo)
	supportedTypes := []string{
		string(types.JSONPatchType),
		string(types.MergePatchType),
	}
	if utilfeature.DefaultFeatureGate.Enabled(features.ServerSideApply) {
		supportedTypes = append(supportedTypes, string(types.ApplyPatchType))
	}

	var handlerFunc http.HandlerFunc
	subresources, err := apiextensions.GetSubresourcesForVersion(crd, requestInfo.APIVersion)
	if err != nil {
		utilruntime.HandleError(err)
		http.Error(w, "the server could not properly serve the CR subresources", http.StatusInternalServerError)
		return
	}
	switch {
	case subresource == "status" && subresources != nil && subresources.Status != nil:
		handlerFunc = r.serveStatus(w, req, requestInfo, crdInfo, terminating, supportedTypes)
	case subresource == "scale" && subresources != nil && subresources.Scale != nil:
		handlerFunc = r.serveScale(w, req, requestInfo, crdInfo, terminating, supportedTypes)
	case len(subresource) == 0:
		handlerFunc = r.serveResource(w, req, requestInfo, crdInfo, terminating, supportedTypes)
	default:
		http.Error(w, "the server could not find the requested resource", http.StatusNotFound)
	}

	if handlerFunc != nil {
		handlerFunc = metrics.InstrumentHandlerFunc(verb, requestInfo.APIGroup, requestInfo.APIVersion, resource, subresource, scope, metrics.APIServerComponent, handlerFunc)
		handler := genericfilters.WithWaitGroup(handlerFunc, longRunningFilter, crdInfo.waitGroup)
		handler.ServeHTTP(w, req)
		return
	}
}

func (r *crdHandler) serveResource(w http.ResponseWriter, req *http.Request, requestInfo *apirequest.RequestInfo, crdInfo *crdInfo, terminating bool, supportedTypes []string) http.HandlerFunc {
	requestScope := crdInfo.requestScopes[requestInfo.APIVersion]
	storage := crdInfo.storages[requestInfo.APIVersion].CustomResource

	switch requestInfo.Verb {
	case "get":
		return handlers.GetResource(storage, storage, requestScope)
	case "list":
		forceWatch := false
		return handlers.ListResource(storage, storage, requestScope, forceWatch, r.minRequestTimeout)
	case "watch":
		forceWatch := true
		return handlers.ListResource(storage, storage, requestScope, forceWatch, r.minRequestTimeout)
	case "create":
		if terminating {
			http.Error(w, fmt.Sprintf("%v not allowed while CustomResourceDefinition is terminating", requestInfo.Verb), http.StatusMethodNotAllowed)
			return nil
		}
		return handlers.CreateResource(storage, requestScope, r.admission)
	case "update":
		return handlers.UpdateResource(storage, requestScope, r.admission)
	case "patch":
		return handlers.PatchResource(storage, requestScope, r.admission, supportedTypes)
	case "delete":
		allowsOptions := true
		return handlers.DeleteResource(storage, allowsOptions, requestScope, r.admission)
	case "deletecollection":
		checkBody := true
		return handlers.DeleteCollection(storage, checkBody, requestScope, r.admission)
	default:
		http.Error(w, fmt.Sprintf("unhandled verb %q", requestInfo.Verb), http.StatusMethodNotAllowed)
		return nil
	}
}

func (r *crdHandler) serveStatus(w http.ResponseWriter, req *http.Request, requestInfo *apirequest.RequestInfo, crdInfo *crdInfo, terminating bool, supportedTypes []string) http.HandlerFunc {
	requestScope := crdInfo.statusRequestScopes[requestInfo.APIVersion]
	storage := crdInfo.storages[requestInfo.APIVersion].Status

	switch requestInfo.Verb {
	case "get":
		return handlers.GetResource(storage, nil, requestScope)
	case "update":
		return handlers.UpdateResource(storage, requestScope, r.admission)
	case "patch":
		return handlers.PatchResource(storage, requestScope, r.admission, supportedTypes)
	default:
		http.Error(w, fmt.Sprintf("unhandled verb %q", requestInfo.Verb), http.StatusMethodNotAllowed)
		return nil
	}
}

func (r *crdHandler) serveScale(w http.ResponseWriter, req *http.Request, requestInfo *apirequest.RequestInfo, crdInfo *crdInfo, terminating bool, supportedTypes []string) http.HandlerFunc {
	requestScope := crdInfo.scaleRequestScopes[requestInfo.APIVersion]
	storage := crdInfo.storages[requestInfo.APIVersion].Scale

	switch requestInfo.Verb {
	case "get":
		return handlers.GetResource(storage, nil, requestScope)
	case "update":
		return handlers.UpdateResource(storage, requestScope, r.admission)
	case "patch":
		return handlers.PatchResource(storage, requestScope, r.admission, supportedTypes)
	default:
		http.Error(w, fmt.Sprintf("unhandled verb %q", requestInfo.Verb), http.StatusMethodNotAllowed)
		return nil
	}
}

func (r *crdHandler) updateCustomResourceDefinition(oldObj, newObj interface{}) {
	oldCRD := oldObj.(*apiextensions.CustomResourceDefinition)
	newCRD := newObj.(*apiextensions.CustomResourceDefinition)

	r.customStorageLock.Lock()
	defer r.customStorageLock.Unlock()

	// Add CRD to the establishing controller queue.
	// For HA clusters, we want to prevent race conditions when changing status to Established,
	// so we want to be sure that CRD is Installing at least for 5 seconds before Establishing it.
	// TODO: find a real HA safe checkpointing mechanism instead of an arbitrary wait.
	if !apiextensions.IsCRDConditionTrue(newCRD, apiextensions.Established) &&
		apiextensions.IsCRDConditionTrue(newCRD, apiextensions.NamesAccepted) {
		if r.masterCount > 1 {
			r.establishingController.QueueCRD(newCRD.Tenant+"/"+newCRD.Name, 5*time.Second)
		} else {
			r.establishingController.QueueCRD(newCRD.Tenant+"/"+newCRD.Name, 0)
		}
	}

	storageMap := r.customStorage.Load().(crdStorageMap)
	oldInfo, found := storageMap[newCRD.UID]
	if !found {
		return
	}
	if apiequality.Semantic.DeepEqual(&newCRD.Spec, oldInfo.spec) && apiequality.Semantic.DeepEqual(&newCRD.Status.AcceptedNames, oldInfo.acceptedNames) {
		klog.V(6).Infof("Ignoring customresourcedefinition %s update because neither spec, nor accepted names changed", oldCRD.Name)
		return
	}

	klog.V(4).Infof("Updating customresourcedefinition %s", oldCRD.Name)

	if oldInfo, ok := storageMap[types.UID(oldCRD.UID)]; ok {
		// Copy because we cannot write to storageMap without a race
		// as it is used without locking elsewhere.
		storageMap2 := storageMap.clone()

		// Remove from the CRD info map and store the map
		delete(storageMap2, types.UID(oldCRD.UID))
		r.customStorage.Store(storageMap2)

		// Tear down the old storage
		go r.tearDown(oldInfo)
	}
}

// removeDeadStorage removes REST storage that isn't being used
func (r *crdHandler) removeDeadStorage() {
	allCustomResourceDefinitions, err := r.crdLister.List(labels.Everything())
	if err != nil {
		utilruntime.HandleError(err)
		return
	}

	r.customStorageLock.Lock()
	defer r.customStorageLock.Unlock()

	oldInfos := []*crdInfo{}
	storageMap := r.customStorage.Load().(crdStorageMap)
	// Copy because we cannot write to storageMap without a race
	// as it is used without locking elsewhere
	storageMap2 := storageMap.clone()
	for uid, s := range storageMap2 {
		found := false
		for _, crd := range allCustomResourceDefinitions {
			if crd.UID == uid {
				found = true
				break
			}
		}
		if !found {
			klog.V(4).Infof("Removing dead CRD storage for %s/%s", s.spec.Group, s.spec.Names.Kind)
			oldInfos = append(oldInfos, s)
			delete(storageMap2, uid)
		}
	}
	r.customStorage.Store(storageMap2)

	for _, s := range oldInfos {
		go r.tearDown(s)
	}
}

// Wait up to a minute for requests to drain, then tear down storage
func (r *crdHandler) tearDown(oldInfo *crdInfo) {
	requestsDrained := make(chan struct{})
	go func() {
		defer close(requestsDrained)
		// Allow time for in-flight requests with a handle to the old info to register themselves
		time.Sleep(time.Second)
		// Wait for in-flight requests to drain
		oldInfo.waitGroup.Wait()
	}()

	select {
	case <-time.After(r.requestTimeout * 2):
		klog.Warningf("timeout waiting for requests to drain for %s/%s, tearing down storage", oldInfo.spec.Group, oldInfo.spec.Names.Kind)
	case <-requestsDrained:
	}

	for _, storage := range oldInfo.storages {
		// destroy only the main storage. Those for the subresources share cacher and etcd clients.
		storage.CustomResource.DestroyFunc()
	}
}

// GetCustomResourceListerCollectionDeleter returns the ListerCollectionDeleter of
// the given crd.
func (r *crdHandler) GetCustomResourceListerCollectionDeleter(crd *apiextensions.CustomResourceDefinition) (finalizer.ListerCollectionDeleter, error) {
	info, err := r.getOrCreateServingInfoFor(crd)
	if err != nil {
		return nil, err
	}
	return info.storages[info.storageVersion].CustomResource, nil
}

func (r *crdHandler) GetCustomResourceStorage(tenant, crdName, version string) (*customresource.CustomResourceStorage, error) {
	crd, err := r.crdLister.CustomResourceDefinitionsWithMultiTenancy(tenant).GetAccessibleCrd(crdName)
	if err != nil {
		return nil, fmt.Errorf("cannot find CRD of %s in tenant %s: %v", crdName, tenant, err)
	}

	var crdInfo *crdInfo
	crdInfo, err = r.getOrCreateServingInfoFor(crd)
	if err != nil {
		return nil, fmt.Errorf("cannot get or create CRD info struct for %s of tenant %s: %v", crdName, tenant, err)
	}

	if s, ok := crdInfo.storages[version]; ok {
		return &s, nil
	}

	return nil, fmt.Errorf("cannot find storage of version %s for crd %s/%s/%s, err: %v", version, crd.Tenant, crd.Namespace, crd.Name, err)
}

func (r *crdHandler) getOrCreateServingInfoFor(crd *apiextensions.CustomResourceDefinition) (*crdInfo, error) {
	storageMap := r.customStorage.Load().(crdStorageMap)
	if ret, ok := storageMap[crd.UID]; ok {
		return ret, nil
	}

	r.customStorageLock.Lock()
	defer r.customStorageLock.Unlock()

	storageMap = r.customStorage.Load().(crdStorageMap)
	if ret, ok := storageMap[crd.UID]; ok {
		return ret, nil
	}

	storageVersion, err := apiextensions.GetCRDStorageVersion(crd)
	if err != nil {
		return nil, err
	}

	// Scope/Storages per version.
	requestScopes := map[string]*handlers.RequestScope{}
	storages := map[string]customresource.CustomResourceStorage{}
	statusScopes := map[string]*handlers.RequestScope{}
	scaleScopes := map[string]*handlers.RequestScope{}

	equivalentResourceRegistry := runtime.NewEquivalentResourceRegistry()

	structuralSchemas := map[string]*structuralschema.Structural{}
	for _, v := range crd.Spec.Versions {
		val, err := apiextensions.GetSchemaForVersion(crd, v.Name)
		if err != nil {
			utilruntime.HandleError(err)
			return nil, fmt.Errorf("the server could not properly serve the CR schema")
		}
		if val == nil {
			continue
		}
		structuralSchemas[v.Name], err = structuralschema.NewStructural(val.OpenAPIV3Schema)
		if *crd.Spec.PreserveUnknownFields == false && err != nil {
			utilruntime.HandleError(err)
			return nil, fmt.Errorf("the server could not properly serve the CR schema") // validation should avoid this
		}
	}

	var openAPIModels proto.Models
	if utilfeature.DefaultFeatureGate.Enabled(features.ServerSideApply) && r.staticOpenAPISpec != nil {
		specs := []*spec.Swagger{}
		for _, v := range crd.Spec.Versions {
			s, err := builder.BuildSwagger(crd, v.Name, builder.Options{V2: false, StripDefaults: true, StripValueValidation: true})
			if err != nil {
				utilruntime.HandleError(err)
				return nil, fmt.Errorf("the server could not properly serve the CR schema")
			}
			specs = append(specs, s)
		}
		mergedOpenAPI, err := builder.MergeSpecs(r.staticOpenAPISpec, specs...)
		if err != nil {
			utilruntime.HandleError(err)
			return nil, fmt.Errorf("the server could not properly merge the CR schema")
		}
		openAPIModels, err = utilopenapi.ToProtoModels(mergedOpenAPI)
		if err != nil {
			utilruntime.HandleError(err)
			return nil, fmt.Errorf("the server could not properly serve the CR schema")
		}
	}

	for _, v := range crd.Spec.Versions {
		safeConverter, unsafeConverter, err := r.converterFactory.NewConverter(crd)
		if err != nil {
			return nil, err
		}
		// In addition to Unstructured objects (Custom Resources), we also may sometimes need to
		// decode unversioned Options objects, so we delegate to parameterScheme for such types.
		parameterScheme := runtime.NewScheme()
		parameterScheme.AddUnversionedTypes(schema.GroupVersion{Group: crd.Spec.Group, Version: v.Name},
			&metav1.ListOptions{},
			&metav1.ExportOptions{},
			&metav1.GetOptions{},
			&metav1.DeleteOptions{},
		)
		parameterCodec := runtime.NewParameterCodec(parameterScheme)

		resource := schema.GroupVersionResource{Group: crd.Spec.Group, Version: v.Name, Resource: crd.Status.AcceptedNames.Plural}
		kind := schema.GroupVersionKind{Group: crd.Spec.Group, Version: v.Name, Kind: crd.Status.AcceptedNames.Kind}
		equivalentResourceRegistry.RegisterKindFor(resource, "", kind)

		typer := newUnstructuredObjectTyper(parameterScheme)
		creator := unstructuredCreator{}

		validationSchema, err := apiextensions.GetSchemaForVersion(crd, v.Name)
		if err != nil {
			utilruntime.HandleError(err)
			return nil, fmt.Errorf("the server could not properly serve the CR schema")
		}
		validator, _, err := apiservervalidation.NewSchemaValidator(validationSchema)
		if err != nil {
			return nil, err
		}

		// Check for nil because we dereference this throughout the handler code.
		// Note: we always default this to non-nil. But we should guard these dereferences any way.
		if crd.Spec.PreserveUnknownFields == nil {
			return nil, fmt.Errorf("unexpected nil spec.preserveUnknownFields in the CustomResourceDefinition")
		}

		var statusSpec *apiextensions.CustomResourceSubresourceStatus
		var statusValidator *validate.SchemaValidator
		subresources, err := apiextensions.GetSubresourcesForVersion(crd, v.Name)
		if err != nil {
			utilruntime.HandleError(err)
			return nil, fmt.Errorf("the server could not properly serve the CR subresources")
		}
		if utilfeature.DefaultFeatureGate.Enabled(apiextensionsfeatures.CustomResourceSubresources) && subresources != nil && subresources.Status != nil {
			equivalentResourceRegistry.RegisterKindFor(resource, "status", kind)

			statusSpec = subresources.Status
			// for the status subresource, validate only against the status schema
			if validationSchema != nil && validationSchema.OpenAPIV3Schema != nil && validationSchema.OpenAPIV3Schema.Properties != nil {
				if statusSchema, ok := validationSchema.OpenAPIV3Schema.Properties["status"]; ok {
					openapiSchema := &spec.Schema{}
					if err := apiservervalidation.ConvertJSONSchemaProps(&statusSchema, openapiSchema); err != nil {
						return nil, err
					}
					statusValidator = validate.NewSchemaValidator(openapiSchema, nil, "", strfmt.Default)
				}
			}
		}

		var scaleSpec *apiextensions.CustomResourceSubresourceScale
		if utilfeature.DefaultFeatureGate.Enabled(apiextensionsfeatures.CustomResourceSubresources) && subresources != nil && subresources.Scale != nil {
			equivalentResourceRegistry.RegisterKindFor(resource, "scale", autoscalingv1.SchemeGroupVersion.WithKind("Scale"))

			scaleSpec = subresources.Scale
		}

		columns, err := apiextensions.GetColumnsForVersion(crd, v.Name)
		if err != nil {
			utilruntime.HandleError(err)
			return nil, fmt.Errorf("the server could not properly serve the CR columns")
		}
		table, err := tableconvertor.New(columns)
		if err != nil {
			klog.V(2).Infof("The CRD for %v has an invalid printer specification, falling back to default printing: %v", kind, err)
		}

		storages[v.Name] = customresource.NewStorage(
			resource.GroupResource(),
			kind,
			schema.GroupVersionKind{Group: crd.Spec.Group, Version: v.Name, Kind: crd.Status.AcceptedNames.ListKind},
			customresource.NewStrategy(
				typer,
				// TenantScoped == true if the scope is "Namespaced" or "Tenant"
				crd.Spec.Scope == apiextensions.NamespaceScoped || crd.Spec.Scope == apiextensions.TenantScoped,
				// NamespaceScoped == true if the scope is "Namespaced"
				crd.Spec.Scope == apiextensions.NamespaceScoped,
				kind,
				validator,
				statusValidator,
				structuralSchemas,
				statusSpec,
				scaleSpec,
			),
			crdConversionRESTOptionsGetter{
				RESTOptionsGetter:     r.restOptionsGetter,
				converter:             safeConverter,
				decoderVersion:        schema.GroupVersion{Group: crd.Spec.Group, Version: v.Name},
				encoderVersion:        schema.GroupVersion{Group: crd.Spec.Group, Version: storageVersion},
				structuralSchemas:     structuralSchemas,
				structuralSchemaGK:    kind.GroupKind(),
				preserveUnknownFields: *crd.Spec.PreserveUnknownFields,
			},
			crd.Status.AcceptedNames.Categories,
			table,
		)

		selfLinkPrefix := ""
		// Namer will have different log to generate the self link whether the scope is cluster-scoped or not
		if crd.Spec.Scope == apiextensions.ClusterScoped {
			selfLinkPrefix = "/" + path.Join("apis", crd.Spec.Group, v.Name) + "/" + crd.Status.AcceptedNames.Plural + "/"
		} else {
			selfLinkPrefix = "/" + path.Join("apis", crd.Spec.Group, v.Name) + "/"
		}

		clusterScoped := crd.Spec.Scope == apiextensions.ClusterScoped
		// Note the tenantScoped here takes a different meaning from TenantScoped() in trategy.go.
		// Here tenantScoped simply mean whether the scope is "Tenant",
		// while in strategy.go TenantScoped() is true if the scope is "Namespaced" or "Tenant"
		tenantScoped := crd.Spec.Scope == apiextensions.TenantScoped

		// CRDs explicitly do not support protobuf, but some objects returned by the API server do
		negotiatedSerializer := unstructuredNegotiatedSerializer{
			typer:                 typer,
			creator:               creator,
			converter:             safeConverter,
			structuralSchemas:     structuralSchemas,
			structuralSchemaGK:    kind.GroupKind(),
			preserveUnknownFields: *crd.Spec.PreserveUnknownFields,
		}
		var standardSerializers []runtime.SerializerInfo
		for _, s := range negotiatedSerializer.SupportedMediaTypes() {
			if s.MediaType == runtime.ContentTypeProtobuf {
				continue
			}
			standardSerializers = append(standardSerializers, s)
		}

		requestScopes[v.Name] = &handlers.RequestScope{
			Namer: handlers.ContextBasedNaming{
				SelfLinker:         meta.NewAccessor(),
				ClusterScoped:      clusterScoped,
				TenantScoped:       tenantScoped,
				SelfLinkPathPrefix: selfLinkPrefix,
			},
			Serializer:          negotiatedSerializer,
			ParameterCodec:      parameterCodec,
			StandardSerializers: standardSerializers,

			Creater:         creator,
			Convertor:       safeConverter,
			Defaulter:       unstructuredDefaulter{parameterScheme, structuralSchemas, kind.GroupKind()},
			Typer:           typer,
			UnsafeConvertor: unsafeConverter,

			EquivalentResourceMapper: equivalentResourceRegistry,

			Resource: schema.GroupVersionResource{Group: crd.Spec.Group, Version: v.Name, Resource: crd.Status.AcceptedNames.Plural},
			Kind:     kind,

			// a handler for a specific group-version of a custom resource uses that version as the in-memory representation
			HubGroupVersion: kind.GroupVersion(),

			MetaGroupVersion: metav1.SchemeGroupVersion,

			TableConvertor: storages[v.Name].CustomResource,

			Authorizer: r.authorizer,
		}
		if utilfeature.DefaultFeatureGate.Enabled(features.ServerSideApply) {
			reqScope := *requestScopes[v.Name]
			reqScope.FieldManager, err = fieldmanager.NewCRDFieldManager(
				openAPIModels,
				reqScope.Convertor,
				reqScope.Defaulter,
				reqScope.Kind.GroupVersion(),
				reqScope.HubGroupVersion,
				*crd.Spec.PreserveUnknownFields,
			)
			if err != nil {
				return nil, err
			}
			requestScopes[v.Name] = &reqScope
		}

		// override scaleSpec subresource values
		// shallow copy
		scaleScope := *requestScopes[v.Name]
		scaleConverter := scale.NewScaleConverter()
		scaleScope.Subresource = "scale"
		scaleScope.Serializer = serializer.NewCodecFactory(scaleConverter.Scheme())
		scaleScope.Kind = autoscalingv1.SchemeGroupVersion.WithKind("Scale")
		scaleScope.Namer = handlers.ContextBasedNaming{
			SelfLinker:         meta.NewAccessor(),
			ClusterScoped:      clusterScoped,
			TenantScoped:       tenantScoped,
			SelfLinkPathPrefix: selfLinkPrefix,
			SelfLinkPathSuffix: "/scale",
		}
		scaleScopes[v.Name] = &scaleScope

		// override status subresource values
		// shallow copy
		statusScope := *requestScopes[v.Name]
		statusScope.Subresource = "status"
		statusScope.Serializer = unstructuredNegotiatedSerializer{
			typer: typer, creator: creator,
			converter:             safeConverter,
			structuralSchemas:     structuralSchemas,
			structuralSchemaGK:    kind.GroupKind(),
			preserveUnknownFields: *crd.Spec.PreserveUnknownFields,
		}
		statusScope.Namer = handlers.ContextBasedNaming{
			SelfLinker:         meta.NewAccessor(),
			ClusterScoped:      clusterScoped,
			TenantScoped:       tenantScoped,
			SelfLinkPathPrefix: selfLinkPrefix,
			SelfLinkPathSuffix: "/status",
		}
		statusScopes[v.Name] = &statusScope
	}

	ret := &crdInfo{
		spec:                &crd.Spec,
		acceptedNames:       &crd.Status.AcceptedNames,
		storages:            storages,
		requestScopes:       requestScopes,
		scaleRequestScopes:  scaleScopes,
		statusRequestScopes: statusScopes,
		storageVersion:      storageVersion,
		waitGroup:           &utilwaitgroup.SafeWaitGroup{},
	}

	// Copy because we cannot write to storageMap without a race
	// as it is used without locking elsewhere.
	storageMap2 := storageMap.clone()

	storageMap2[crd.UID] = ret
	r.customStorage.Store(storageMap2)

	return ret, nil
}

type unstructuredNegotiatedSerializer struct {
	typer     runtime.ObjectTyper
	creator   runtime.ObjectCreater
	converter runtime.ObjectConvertor

	structuralSchemas     map[string]*structuralschema.Structural // by version
	structuralSchemaGK    schema.GroupKind
	preserveUnknownFields bool
}

func (s unstructuredNegotiatedSerializer) SupportedMediaTypes() []runtime.SerializerInfo {
	return []runtime.SerializerInfo{
		{
			MediaType:        "application/json",
			MediaTypeType:    "application",
			MediaTypeSubType: "json",
			EncodesAsText:    true,
			Serializer:       json.NewSerializer(json.DefaultMetaFactory, s.creator, s.typer, false),
			PrettySerializer: json.NewSerializer(json.DefaultMetaFactory, s.creator, s.typer, true),
			StreamSerializer: &runtime.StreamSerializerInfo{
				EncodesAsText: true,
				Serializer:    json.NewSerializer(json.DefaultMetaFactory, s.creator, s.typer, false),
				Framer:        json.Framer,
			},
		},
		{
			MediaType:        "application/yaml",
			MediaTypeType:    "application",
			MediaTypeSubType: "yaml",
			EncodesAsText:    true,
			Serializer:       json.NewYAMLSerializer(json.DefaultMetaFactory, s.creator, s.typer),
		},
		{
			MediaType:        "application/vnd.kubernetes.protobuf",
			MediaTypeType:    "application",
			MediaTypeSubType: "vnd.kubernetes.protobuf",
			Serializer:       protobuf.NewSerializer(s.creator, s.typer),
			StreamSerializer: &runtime.StreamSerializerInfo{
				Serializer: protobuf.NewRawSerializer(s.creator, s.typer),
				Framer:     protobuf.LengthDelimitedFramer,
			},
		},
	}
}

func (s unstructuredNegotiatedSerializer) EncoderForVersion(encoder runtime.Encoder, gv runtime.GroupVersioner) runtime.Encoder {
	return versioning.NewCodec(encoder, nil, s.converter, Scheme, Scheme, Scheme, gv, nil, "crdNegotiatedSerializer")
}

func (s unstructuredNegotiatedSerializer) DecoderToVersion(decoder runtime.Decoder, gv runtime.GroupVersioner) runtime.Decoder {
	d := schemaCoercingDecoder{delegate: decoder, validator: unstructuredSchemaCoercer{structuralSchemas: s.structuralSchemas, structuralSchemaGK: s.structuralSchemaGK, preserveUnknownFields: s.preserveUnknownFields}}
	return versioning.NewCodec(nil, d, runtime.UnsafeObjectConvertor(Scheme), Scheme, Scheme, unstructuredDefaulter{
		delegate:           Scheme,
		structuralSchemas:  s.structuralSchemas,
		structuralSchemaGK: s.structuralSchemaGK,
	}, nil, gv, "unstructuredNegotiatedSerializer")
}

type UnstructuredObjectTyper struct {
	Delegate          runtime.ObjectTyper
	UnstructuredTyper runtime.ObjectTyper
}

func newUnstructuredObjectTyper(Delegate runtime.ObjectTyper) UnstructuredObjectTyper {
	return UnstructuredObjectTyper{
		Delegate:          Delegate,
		UnstructuredTyper: crdserverscheme.NewUnstructuredObjectTyper(),
	}
}

func (t UnstructuredObjectTyper) ObjectKinds(obj runtime.Object) ([]schema.GroupVersionKind, bool, error) {
	// Delegate for things other than Unstructured.
	if _, ok := obj.(runtime.Unstructured); !ok {
		return t.Delegate.ObjectKinds(obj)
	}
	return t.UnstructuredTyper.ObjectKinds(obj)
}

func (t UnstructuredObjectTyper) Recognizes(gvk schema.GroupVersionKind) bool {
	return t.Delegate.Recognizes(gvk) || t.UnstructuredTyper.Recognizes(gvk)
}

type unstructuredCreator struct{}

func (c unstructuredCreator) New(kind schema.GroupVersionKind) (runtime.Object, error) {
	ret := &unstructured.Unstructured{}
	ret.SetGroupVersionKind(kind)
	return ret, nil
}

type unstructuredDefaulter struct {
	delegate           runtime.ObjectDefaulter
	structuralSchemas  map[string]*structuralschema.Structural // by version
	structuralSchemaGK schema.GroupKind
}

func (d unstructuredDefaulter) Default(in runtime.Object) {
	// Delegate for things other than Unstructured, and other GKs
	u, ok := in.(runtime.Unstructured)
	if !ok || u.GetObjectKind().GroupVersionKind().GroupKind() != d.structuralSchemaGK {
		d.delegate.Default(in)
		return
	}

	structuraldefaulting.Default(u.UnstructuredContent(), d.structuralSchemas[u.GetObjectKind().GroupVersionKind().Version])
}

type CRDRESTOptionsGetter struct {
	StorageConfig           storagebackend.Config
	StoragePrefix           string
	EnableWatchCache        bool
	DefaultWatchCacheSize   int
	EnableGarbageCollection bool
	DeleteCollectionWorkers int
	CountMetricPollPeriod   time.Duration
}

func (t CRDRESTOptionsGetter) GetRESTOptions(resource schema.GroupResource) (generic.RESTOptions, error) {
	ret := generic.RESTOptions{
		StorageConfig:           &t.StorageConfig,
		Decorator:               generic.UndecoratedStorage,
		EnableGarbageCollection: t.EnableGarbageCollection,
		DeleteCollectionWorkers: t.DeleteCollectionWorkers,
		ResourcePrefix:          resource.Group + "/" + resource.Resource,
		CountMetricPollPeriod:   t.CountMetricPollPeriod,
	}
	if t.EnableWatchCache {
		ret.Decorator = genericregistry.StorageWithCacher(t.DefaultWatchCacheSize)
	}
	return ret, nil
}

// clone returns a clone of the provided crdStorageMap.
// The clone is a shallow copy of the map.
func (in crdStorageMap) clone() crdStorageMap {
	if in == nil {
		return nil
	}
	out := make(crdStorageMap, len(in))
	for key, value := range in {
		out[key] = value
	}
	return out
}

// crdConversionRESTOptionsGetter overrides the codec with one using the
// provided custom converter and custom encoder and decoder version.
type crdConversionRESTOptionsGetter struct {
	generic.RESTOptionsGetter
	converter             runtime.ObjectConvertor
	encoderVersion        schema.GroupVersion
	decoderVersion        schema.GroupVersion
	structuralSchemas     map[string]*structuralschema.Structural // by version
	structuralSchemaGK    schema.GroupKind
	preserveUnknownFields bool
}

func (t crdConversionRESTOptionsGetter) GetRESTOptions(resource schema.GroupResource) (generic.RESTOptions, error) {
	ret, err := t.RESTOptionsGetter.GetRESTOptions(resource)
	if err == nil {
		d := schemaCoercingDecoder{delegate: ret.StorageConfig.Codec, validator: unstructuredSchemaCoercer{
			// drop invalid fields while decoding old CRs (before we haven't had any ObjectMeta validation)
			dropInvalidMetadata:   true,
			structuralSchemas:     t.structuralSchemas,
			structuralSchemaGK:    t.structuralSchemaGK,
			preserveUnknownFields: t.preserveUnknownFields,
		}}
		c := schemaCoercingConverter{delegate: t.converter, validator: unstructuredSchemaCoercer{
			structuralSchemas:     t.structuralSchemas,
			structuralSchemaGK:    t.structuralSchemaGK,
			preserveUnknownFields: t.preserveUnknownFields,
		}}
		ret.StorageConfig.Codec = versioning.NewCodec(
			ret.StorageConfig.Codec,
			d,
			c,
			&unstructuredCreator{},
			crdserverscheme.NewUnstructuredObjectTyper(),
			&unstructuredDefaulter{
				delegate:           Scheme,
				structuralSchemaGK: t.structuralSchemaGK,
				structuralSchemas:  t.structuralSchemas,
			},
			t.encoderVersion,
			t.decoderVersion,
			"crdRESTOptions",
		)
	}
	return ret, err
}

// schemaCoercingDecoder calls the delegate decoder, and then applies the Unstructured schema validator
// to coerce the schema.
type schemaCoercingDecoder struct {
	delegate  runtime.Decoder
	validator unstructuredSchemaCoercer
}

var _ runtime.Decoder = schemaCoercingDecoder{}

func (d schemaCoercingDecoder) Decode(data []byte, defaults *schema.GroupVersionKind, into runtime.Object) (runtime.Object, *schema.GroupVersionKind, error) {
	obj, gvk, err := d.delegate.Decode(data, defaults, into)
	if err != nil {
		return nil, gvk, err
	}
	if u, ok := obj.(*unstructured.Unstructured); ok {
		if err := d.validator.apply(u); err != nil {
			return nil, gvk, err
		}
	}

	return obj, gvk, nil
}

// schemaCoercingConverter calls the delegate converter and applies the Unstructured validator to
// coerce the schema.
type schemaCoercingConverter struct {
	delegate  runtime.ObjectConvertor
	validator unstructuredSchemaCoercer
}

var _ runtime.ObjectConvertor = schemaCoercingConverter{}

func (v schemaCoercingConverter) Convert(in, out, context interface{}) error {
	if err := v.delegate.Convert(in, out, context); err != nil {
		return err
	}

	if u, ok := out.(*unstructured.Unstructured); ok {
		if err := v.validator.apply(u); err != nil {
			return err
		}
	}

	return nil
}

func (v schemaCoercingConverter) ConvertToVersion(in runtime.Object, gv runtime.GroupVersioner) (runtime.Object, error) {
	out, err := v.delegate.ConvertToVersion(in, gv)
	if err != nil {
		return nil, err
	}

	if u, ok := out.(*unstructured.Unstructured); ok {
		if err := v.validator.apply(u); err != nil {
			return nil, err
		}
	}

	return out, nil
}

func (v schemaCoercingConverter) ConvertFieldLabel(gvk schema.GroupVersionKind, label, value string) (string, string, error) {
	return v.delegate.ConvertFieldLabel(gvk, label, value)
}

// unstructuredSchemaCoercer adds to unstructured unmarshalling what json.Unmarshal does
// in addition for native types when decoding into Golang structs:
//
// - validating and pruning ObjectMeta
// - generic pruning of unknown fields following a structural schema.
type unstructuredSchemaCoercer struct {
	dropInvalidMetadata bool

	structuralSchemas     map[string]*structuralschema.Structural
	structuralSchemaGK    schema.GroupKind
	preserveUnknownFields bool
}

func (v *unstructuredSchemaCoercer) apply(u *unstructured.Unstructured) error {
	// save implicit meta fields that don't have to be specified in the validation spec
	kind, foundKind, err := unstructured.NestedString(u.UnstructuredContent(), "kind")
	if err != nil {
		return err
	}
	apiVersion, foundApiVersion, err := unstructured.NestedString(u.UnstructuredContent(), "apiVersion")
	if err != nil {
		return err
	}
	objectMeta, foundObjectMeta, err := schemaobjectmeta.GetObjectMeta(u.Object, v.dropInvalidMetadata)
	if err != nil {
		return err
	}

	// compare group and kind because also other object like DeleteCollection options pass through here
	gv, err := schema.ParseGroupVersion(apiVersion)
	if err != nil {
		return err
	}
	if gv.Group == v.structuralSchemaGK.Group && kind == v.structuralSchemaGK.Kind {
		if !v.preserveUnknownFields {
			// TODO: switch over pruning and coercing at the root to  schemaobjectmeta.Coerce too
			structuralpruning.Prune(u.Object, v.structuralSchemas[gv.Version], false)
		}
		if err := schemaobjectmeta.Coerce(nil, u.Object, v.structuralSchemas[gv.Version], false, v.dropInvalidMetadata); err != nil {
			return err
		}
	}

	// restore meta fields, starting clean
	if foundKind {
		u.SetKind(kind)
	}
	if foundApiVersion {
		u.SetAPIVersion(apiVersion)
	}
	if foundObjectMeta {
		if err := schemaobjectmeta.SetObjectMeta(u.Object, objectMeta); err != nil {
			return err
		}
	}

	return nil
}
