/*
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 crdregistration

import (
	"fmt"
	"time"

	"k8s.io/klog/v2"

	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
	crdinformers "k8s.io/apiextensions-apiserver/pkg/client/informers/externalversions/apiextensions/v1"
	crdlisters "k8s.io/apiextensions-apiserver/pkg/client/listers/apiextensions/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime/schema"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/util/workqueue"
	v1 "k8s.io/kube-aggregator/pkg/apis/apiregistration/v1"
)

// AutoAPIServiceRegistration is an interface which callers can re-declare locally and properly cast to for
// adding and removing APIServices
type AutoAPIServiceRegistration interface {
	// AddAPIServiceToSync adds an API service to auto-register.
	AddAPIServiceToSync(in *v1.APIService)
	// RemoveAPIServiceToSync removes an API service to auto-register.
	RemoveAPIServiceToSync(name string)
}

type crdRegistrationController struct {
	crdLister crdlisters.CustomResourceDefinitionLister
	crdSynced cache.InformerSynced

	apiServiceRegistration AutoAPIServiceRegistration

	syncHandler func(groupVersion schema.GroupVersion) error

	syncedInitialSet chan struct{}

	// queue is where incoming work is placed to de-dup and to allow "easy" rate limited requeues on errors
	// this is actually keyed by a groupVersion
	queue workqueue.RateLimitingInterface
}

// NewCRDRegistrationController returns a controller which will register CRD GroupVersions with the auto APIService registration
// controller so they automatically stay in sync.
func NewCRDRegistrationController(crdinformer crdinformers.CustomResourceDefinitionInformer, apiServiceRegistration AutoAPIServiceRegistration) *crdRegistrationController {
	c := &crdRegistrationController{
		crdLister:              crdinformer.Lister(),
		crdSynced:              crdinformer.Informer().HasSynced,
		apiServiceRegistration: apiServiceRegistration,
		syncedInitialSet:       make(chan struct{}),
		queue:                  workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "crd_autoregistration_controller"),
	}
	c.syncHandler = c.handleVersionUpdate

	crdinformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			cast := obj.(*apiextensionsv1.CustomResourceDefinition)
			c.enqueueCRD(cast)
		},
		UpdateFunc: func(oldObj, newObj interface{}) {
			// Enqueue both old and new object to make sure we remove and add appropriate API services.
			// The working queue will resolve any duplicates and only changes will stay in the queue.
			c.enqueueCRD(oldObj.(*apiextensionsv1.CustomResourceDefinition))
			c.enqueueCRD(newObj.(*apiextensionsv1.CustomResourceDefinition))
		},
		DeleteFunc: func(obj interface{}) {
			cast, ok := obj.(*apiextensionsv1.CustomResourceDefinition)
			if !ok {
				tombstone, ok := obj.(cache.DeletedFinalStateUnknown)
				if !ok {
					klog.V(2).Infof("Couldn't get object from tombstone %#v", obj)
					return
				}
				cast, ok = tombstone.Obj.(*apiextensionsv1.CustomResourceDefinition)
				if !ok {
					klog.V(2).Infof("Tombstone contained unexpected object: %#v", obj)
					return
				}
			}
			c.enqueueCRD(cast)
		},
	})

	return c
}

func (c *crdRegistrationController) Run(workers int, stopCh <-chan struct{}) {
	defer utilruntime.HandleCrash()
	// make sure the work queue is shutdown which will trigger workers to end
	defer c.queue.ShutDown()

	klog.Infof("Starting crd-autoregister controller")
	defer klog.Infof("Shutting down crd-autoregister controller")

	// wait for your secondary caches to fill before starting your work
	if !cache.WaitForNamedCacheSync("crd-autoregister", stopCh, c.crdSynced) {
		return
	}

	// process each item in the list once
	if crds, err := c.crdLister.List(labels.Everything()); err != nil {
		utilruntime.HandleError(err)
	} else {
		for _, crd := range crds {
			for _, version := range crd.Spec.Versions {
				if err := c.syncHandler(schema.GroupVersion{Group: crd.Spec.Group, Version: version.Name}); err != nil {
					utilruntime.HandleError(err)
				}
			}
		}
	}
	close(c.syncedInitialSet)

	// start up your worker threads based on workers.  Some controllers have multiple kinds of workers
	for i := 0; i < workers; i++ {
		// runWorker will loop until "something bad" happens.  The .Until will then rekick the worker
		// after one second
		go wait.Until(c.runWorker, time.Second, stopCh)
	}

	// wait until we're told to stop
	<-stopCh
}

// WaitForInitialSync blocks until the initial set of CRD resources has been processed
func (c *crdRegistrationController) WaitForInitialSync() {
	<-c.syncedInitialSet
}

func (c *crdRegistrationController) runWorker() {
	// hot loop until we're told to stop.  processNextWorkItem will automatically wait until there's work
	// available, so we don't worry about secondary waits
	for c.processNextWorkItem() {
	}
}

// processNextWorkItem deals with one key off the queue.  It returns false when it's time to quit.
func (c *crdRegistrationController) processNextWorkItem() bool {
	// pull the next work item from queue.  It should be a key we use to lookup something in a cache
	key, quit := c.queue.Get()
	if quit {
		return false
	}
	// you always have to indicate to the queue that you've completed a piece of work
	defer c.queue.Done(key)

	// do your work on the key.  This method will contains your "do stuff" logic
	err := c.syncHandler(key.(schema.GroupVersion))
	if err == nil {
		// if you had no error, tell the queue to stop tracking history for your key.  This will
		// reset things like failure counts for per-item rate limiting
		c.queue.Forget(key)
		return true
	}

	// there was a failure so be sure to report it.  This method allows for pluggable error handling
	// which can be used for things like cluster-monitoring
	utilruntime.HandleError(fmt.Errorf("%v failed with : %v", key, err))
	// since we failed, we should requeue the item to work on later.  This method will add a backoff
	// to avoid hotlooping on particular items (they're probably still not going to work right away)
	// and overall controller protection (everything I've done is broken, this controller needs to
	// calm down or it can starve other useful work) cases.
	c.queue.AddRateLimited(key)

	return true
}

func (c *crdRegistrationController) enqueueCRD(crd *apiextensionsv1.CustomResourceDefinition) {
	for _, version := range crd.Spec.Versions {
		c.queue.Add(schema.GroupVersion{Group: crd.Spec.Group, Version: version.Name})
	}
}

func (c *crdRegistrationController) handleVersionUpdate(groupVersion schema.GroupVersion) error {
	apiServiceName := groupVersion.Version + "." + groupVersion.Group

	// check all CRDs.  There shouldn't that many, but if we have problems later we can index them
	crds, err := c.crdLister.List(labels.Everything())
	if err != nil {
		return err
	}
	for _, crd := range crds {
		if crd.Spec.Group != groupVersion.Group {
			continue
		}
		for _, version := range crd.Spec.Versions {
			if version.Name != groupVersion.Version || !version.Served {
				continue
			}

			c.apiServiceRegistration.AddAPIServiceToSync(&v1.APIService{
				ObjectMeta: metav1.ObjectMeta{Name: apiServiceName},
				Spec: v1.APIServiceSpec{
					Group:                groupVersion.Group,
					Version:              groupVersion.Version,
					GroupPriorityMinimum: 1000, // CRDs should have relatively low priority
					VersionPriority:      100,  // CRDs will be sorted by kube-like versions like any other APIService with the same VersionPriority
				},
			})
			return nil
		}
	}

	c.apiServiceRegistration.RemoveAPIServiceToSync(apiServiceName)
	return nil
}
