/*
Copyright 2020 KubeSphere 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 destinationrule

import (
	"context"
	"fmt"
	"reflect"

	"kubesphere.io/kubesphere/pkg/controller/utils/servicemesh"

	"time"

	apinetworkingv1alpha3 "istio.io/api/networking/v1alpha3"
	clientgonetworkingv1alpha3 "istio.io/client-go/pkg/apis/networking/v1alpha3"
	appsv1 "k8s.io/api/apps/v1"
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/types"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/kubernetes/scheme"
	v1core "k8s.io/client-go/kubernetes/typed/core/v1"
	log "k8s.io/klog"

	servicemeshv1alpha2 "kubesphere.io/api/servicemesh/v1alpha2"

	istioclientset "istio.io/client-go/pkg/clientset/versioned"
	istioinformers "istio.io/client-go/pkg/informers/externalversions/networking/v1alpha3"
	istiolisters "istio.io/client-go/pkg/listers/networking/v1alpha3"
	informersv1 "k8s.io/client-go/informers/apps/v1"
	coreinformers "k8s.io/client-go/informers/core/v1"
	clientset "k8s.io/client-go/kubernetes"
	listersv1 "k8s.io/client-go/listers/apps/v1"
	corelisters "k8s.io/client-go/listers/core/v1"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/record"
	"k8s.io/client-go/util/workqueue"

	servicemeshclient "kubesphere.io/kubesphere/pkg/client/clientset/versioned"
	servicemeshinformers "kubesphere.io/kubesphere/pkg/client/informers/externalversions/servicemesh/v1alpha2"
	servicemeshlisters "kubesphere.io/kubesphere/pkg/client/listers/servicemesh/v1alpha2"
)

const (
	// maxRetries is the number of times a service will be retried before it is dropped out of the queue.
	// With the current rate-limiter in use (5ms*2^(maxRetries-1)) the following numbers represent the
	// sequence of delays between successive queuings of a service.
	//
	// 5ms, 10ms, 20ms, 40ms, 80ms, 160ms, 320ms, 640ms, 1.3s, 2.6s, 5.1s, 10.2s, 20.4s, 41s, 82s
	maxRetries = 15
)

type DestinationRuleController struct {
	client clientset.Interface

	destinationRuleClient istioclientset.Interface
	servicemeshClient     servicemeshclient.Interface

	eventBroadcaster record.EventBroadcaster
	eventRecorder    record.EventRecorder

	serviceLister corelisters.ServiceLister
	serviceSynced cache.InformerSynced

	deploymentLister listersv1.DeploymentLister
	deploymentSynced cache.InformerSynced

	servicePolicyLister servicemeshlisters.ServicePolicyLister
	servicePolicySynced cache.InformerSynced

	destinationRuleLister istiolisters.DestinationRuleLister
	destinationRuleSynced cache.InformerSynced

	queue workqueue.RateLimitingInterface

	workerLoopPeriod time.Duration
}

func NewDestinationRuleController(deploymentInformer informersv1.DeploymentInformer,
	destinationRuleInformer istioinformers.DestinationRuleInformer,
	serviceInformer coreinformers.ServiceInformer,
	servicePolicyInformer servicemeshinformers.ServicePolicyInformer,
	client clientset.Interface,
	destinationRuleClient istioclientset.Interface,
	servicemeshClient servicemeshclient.Interface) *DestinationRuleController {

	broadcaster := record.NewBroadcaster()
	broadcaster.StartLogging(func(format string, args ...interface{}) {
		log.Info(fmt.Sprintf(format, args))
	})
	broadcaster.StartRecordingToSink(&v1core.EventSinkImpl{Interface: client.CoreV1().Events("")})
	recorder := broadcaster.NewRecorder(scheme.Scheme, v1.EventSource{Component: "destinationrule-controller"})

	v := &DestinationRuleController{
		client:                client,
		destinationRuleClient: destinationRuleClient,
		servicemeshClient:     servicemeshClient,
		queue:                 workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "destinationrule"),
		workerLoopPeriod:      time.Second,
	}

	v.deploymentLister = deploymentInformer.Lister()
	v.deploymentSynced = deploymentInformer.Informer().HasSynced

	deploymentInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc:    v.addDeployment,
		DeleteFunc: v.deleteDeployment,
		UpdateFunc: func(old, cur interface{}) {
			v.addDeployment(cur)
		},
	})

	v.serviceLister = serviceInformer.Lister()
	v.serviceSynced = serviceInformer.Informer().HasSynced

	serviceInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc:    v.enqueueService,
		DeleteFunc: v.enqueueService,
		UpdateFunc: func(old, cur interface{}) {
			v.enqueueService(cur)
		},
	})

	v.destinationRuleLister = destinationRuleInformer.Lister()
	v.destinationRuleSynced = destinationRuleInformer.Informer().HasSynced

	v.servicePolicyLister = servicePolicyInformer.Lister()
	v.servicePolicySynced = servicePolicyInformer.Informer().HasSynced

	servicePolicyInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: v.addServicePolicy,
		UpdateFunc: func(old, cur interface{}) {
			v.addServicePolicy(cur)
		},
		DeleteFunc: v.addServicePolicy,
	})

	v.eventBroadcaster = broadcaster
	v.eventRecorder = recorder

	return v

}

func (v *DestinationRuleController) Start(ctx context.Context) error {
	return v.Run(5, ctx.Done())
}

func (v *DestinationRuleController) Run(workers int, stopCh <-chan struct{}) error {
	defer utilruntime.HandleCrash()
	defer v.queue.ShutDown()

	log.Info("starting destinationrule controller")
	defer log.Info("shutting down destinationrule controller")

	if !cache.WaitForCacheSync(stopCh, v.serviceSynced, v.destinationRuleSynced, v.deploymentSynced, v.servicePolicySynced) {
		return fmt.Errorf("failed to wait for caches to sync")
	}

	for i := 0; i < workers; i++ {
		go wait.Until(v.worker, v.workerLoopPeriod, stopCh)
	}

	<-stopCh
	return nil
}

func (v *DestinationRuleController) enqueueService(obj interface{}) {
	key, err := cache.MetaNamespaceKeyFunc(obj)
	if err != nil {
		utilruntime.HandleError(fmt.Errorf("couldn't get key for object %+v: %v", obj, err))
		return
	}

	v.queue.Add(key)
}

func (v *DestinationRuleController) worker() {
	for v.processNextWorkItem() {

	}
}

func (v *DestinationRuleController) processNextWorkItem() bool {
	eKey, quit := v.queue.Get()
	if quit {
		return false
	}

	defer v.queue.Done(eKey)

	err := v.syncService(eKey.(string))
	v.handleErr(err, eKey)

	return true
}

// main function of the reconcile for destinationrule
// destinationrule's name is same with the service that created it
func (v *DestinationRuleController) syncService(key string) error {
	startTime := time.Now()
	defer func() {
		log.V(4).Infof("Finished syncing service destinationrule %s in %s.", key, time.Since(startTime))
	}()

	namespace, name, err := cache.SplitMetaNamespaceKey(key)
	if err != nil {
		return err
	}

	service, err := v.serviceLister.Services(namespace).Get(name)
	if err != nil {
		// delete the corresponding destinationrule if there is any, as the service has been deleted.
		err = v.destinationRuleClient.NetworkingV1alpha3().DestinationRules(namespace).Delete(context.Background(), name, metav1.DeleteOptions{})
		if err != nil && !errors.IsNotFound(err) {
			log.Errorf("delete destination rule failed %s/%s, error %v.", namespace, name, err)
			return err
		}

		// delete orphan service policy if there is any
		err = v.servicemeshClient.ServicemeshV1alpha2().ServicePolicies(namespace).Delete(context.Background(), name, metav1.DeleteOptions{})
		if err != nil && !errors.IsNotFound(err) {
			log.Errorf("delete orphan service policy %s/%s failed, %#v", namespace, name, err)
			return err
		}

		return nil
	}

	if len(service.Labels) < len(servicemesh.ApplicationLabels) ||
		!servicemesh.IsApplicationComponent(service.Labels) ||
		!servicemesh.IsServicemeshEnabled(service.Annotations) ||
		len(service.Spec.Ports) == 0 {
		// services don't have enough labels to create a destinationrule
		// or they don't have necessary labels
		// or they don't have servicemesh enabled
		// or they don't have any ports defined
		return nil
	}

	appName := servicemesh.GetComponentName(&service.ObjectMeta)

	// fetch all deployments that match with service selector
	deployments, err := v.deploymentLister.Deployments(namespace).List(labels.Set(service.Spec.Selector).AsSelectorPreValidated())
	if err != nil {
		return err
	}

	subsets := make([]*apinetworkingv1alpha3.Subset, 0)
	for _, deployment := range deployments {

		// not a valid deployment we required
		if !servicemesh.IsApplicationComponent(deployment.Labels) ||
			!servicemesh.IsApplicationComponent(deployment.Spec.Selector.MatchLabels) ||
			deployment.Status.ReadyReplicas == 0 ||
			!servicemesh.IsServicemeshEnabled(deployment.Annotations) {
			continue
		}

		version := servicemesh.GetComponentVersion(&deployment.ObjectMeta)

		if len(version) == 0 {
			log.V(4).Infof("Deployment %s doesn't have a version label", types.NamespacedName{Namespace: deployment.Namespace, Name: deployment.Name}.String())
			continue
		}

		subset := &apinetworkingv1alpha3.Subset{
			Name: servicemesh.NormalizeVersionName(version),
			Labels: map[string]string{
				servicemesh.VersionLabel: version,
			},
		}

		subsets = append(subsets, subset)
	}

	currentDestinationRule, err := v.destinationRuleLister.DestinationRules(namespace).Get(name)
	if err != nil {
		if errors.IsNotFound(err) {
			currentDestinationRule = &clientgonetworkingv1alpha3.DestinationRule{
				ObjectMeta: metav1.ObjectMeta{
					Name:   service.Name,
					Labels: service.Labels,
				},
				Spec: apinetworkingv1alpha3.DestinationRule{
					Host: name,
				},
			}
		} else {
			log.Error(err, "Couldn't get destinationrule for service", "key", key)
			return err
		}
	}

	// fetch all servicepolicies associated to this service
	servicePolicies, err := v.servicePolicyLister.ServicePolicies(namespace).List(labels.SelectorFromSet(map[string]string{servicemesh.AppLabel: appName}))
	if err != nil {
		log.Error(err, "could not list service policies is namespace with component name", "namespace", namespace, "name", appName)
		return err
	}

	dr := currentDestinationRule.DeepCopy()
	dr.Spec.TrafficPolicy = nil
	dr.Spec.Subsets = subsets
	//
	if len(servicePolicies) > 0 {
		if len(servicePolicies) > 1 {
			err = fmt.Errorf("more than one service policy associated with service %s/%s is forbidden", namespace, name)
			log.Error(err, "")
			return err
		}

		sp := servicePolicies[0]
		if sp.Spec.Template.Spec.TrafficPolicy != nil {
			dr.Spec.TrafficPolicy = sp.Spec.Template.Spec.TrafficPolicy
		}

		for _, subset := range sp.Spec.Template.Spec.Subsets {
			for i := range dr.Spec.Subsets {
				if subset.Name == dr.Spec.Subsets[i].Name && subset.TrafficPolicy != nil {
					dr.Spec.Subsets[i].TrafficPolicy = subset.TrafficPolicy
				}
			}
		}
	}

	createDestinationRule := len(currentDestinationRule.ResourceVersion) == 0

	if !createDestinationRule && reflect.DeepEqual(currentDestinationRule.Spec, dr.Spec) &&
		reflect.DeepEqual(currentDestinationRule.Labels, service.Labels) {
		log.V(5).Info("destinationrule are equal, skipping update", "key", types.NamespacedName{Namespace: service.Namespace, Name: service.Name}.String())
		return nil
	}

	newDestinationRule := currentDestinationRule.DeepCopy()
	newDestinationRule.Spec = dr.Spec
	newDestinationRule.Labels = service.Labels
	if newDestinationRule.Annotations == nil {
		newDestinationRule.Annotations = make(map[string]string)
	}

	if createDestinationRule {
		_, err = v.destinationRuleClient.NetworkingV1alpha3().DestinationRules(namespace).Create(context.Background(), newDestinationRule, metav1.CreateOptions{})
	} else {
		_, err = v.destinationRuleClient.NetworkingV1alpha3().DestinationRules(namespace).Update(context.Background(), newDestinationRule, metav1.UpdateOptions{})
	}

	if err != nil {
		if createDestinationRule && errors.IsForbidden(err) {
			// A request is forbidden primarily for two reasons:
			// 1. namespace is terminating, endpoint creation is not allowed by default.
			// 2. policy is misconfigured, in which case no service would function anywhere.
			// Given the frequency of 1, we log at a lower level.
			log.V(5).Info("Forbidden from creating endpoints", "error", err)
		}

		if createDestinationRule {
			v.eventRecorder.Event(newDestinationRule, v1.EventTypeWarning, "FailedToCreateDestinationRule", fmt.Sprintf("Failed to create destinationrule for service %v/%v: %v", service.Namespace, service.Name, err))
		} else {
			v.eventRecorder.Event(newDestinationRule, v1.EventTypeWarning, "FailedToUpdateDestinationRule", fmt.Sprintf("Failed to update destinationrule for service %v/%v: %v", service.Namespace, service.Name, err))
		}

		return err
	}

	return nil
}

// When a destinationrule is added, figure out which service it will be used
// and enqueue it. obj must have *appsv1.Deployment type
func (v *DestinationRuleController) addDeployment(obj interface{}) {
	deploy := obj.(*appsv1.Deployment)

	// not a application component
	if !servicemesh.IsApplicationComponent(deploy.Labels) || !servicemesh.IsApplicationComponent(deploy.Spec.Selector.MatchLabels) {
		return
	}

	services, err := v.getDeploymentServiceMemberShip(deploy)
	if err != nil {
		utilruntime.HandleError(fmt.Errorf("unable to get deployment %s/%s's service memberships", deploy.Namespace, deploy.Name))
		return
	}

	for key := range services {
		v.queue.Add(key)
	}

	return
}

func (v *DestinationRuleController) deleteDeployment(obj interface{}) {
	if _, ok := obj.(*appsv1.Deployment); ok {
		v.addDeployment(obj)
		return
	}

	tombstone, ok := obj.(cache.DeletedFinalStateUnknown)
	if !ok {
		utilruntime.HandleError(fmt.Errorf("couldn't get object from tombstone %#v", obj))
		return
	}

	deploy, ok := tombstone.Obj.(*appsv1.Deployment)
	if !ok {
		utilruntime.HandleError(fmt.Errorf("tombstone contained object that is not a deployment %#v", obj))
		return
	}

	v.addDeployment(deploy)
}

func (v *DestinationRuleController) getDeploymentServiceMemberShip(deployment *appsv1.Deployment) (sets.String, error) {
	set := sets.String{}

	allServices, err := v.serviceLister.Services(deployment.Namespace).List(labels.Everything())
	if err != nil {
		return set, err
	}

	for i := range allServices {
		service := allServices[i]
		if service.Spec.Selector == nil ||
			!servicemesh.IsApplicationComponent(service.Labels) ||
			!servicemesh.IsServicemeshEnabled(service.Annotations) {
			// services with nil selectors match nothing, not everything.
			continue
		}
		selector := labels.Set(service.Spec.Selector).AsSelectorPreValidated()
		if selector.Matches(labels.Set(deployment.Spec.Selector.MatchLabels)) {
			key, err := cache.MetaNamespaceKeyFunc(service)
			if err != nil {
				return nil, err
			}
			set.Insert(key)
		}
	}

	return set, nil
}

func (v *DestinationRuleController) addServicePolicy(obj interface{}) {
	servicePolicy := obj.(*servicemeshv1alpha2.ServicePolicy)

	appName := servicePolicy.Labels[servicemesh.AppLabel]

	services, err := v.serviceLister.Services(servicePolicy.Namespace).List(labels.SelectorFromSet(map[string]string{servicemesh.AppLabel: appName}))
	if err != nil {
		log.Error(err, "cannot list services", "namespace", servicePolicy.Namespace, "name", appName)
		utilruntime.HandleError(fmt.Errorf("cannot list services in namespace %s, with component name %v", servicePolicy.Namespace, appName))
		return
	}

	set := sets.String{}
	for _, service := range services {
		key, err := cache.MetaNamespaceKeyFunc(service)
		if err != nil {
			utilruntime.HandleError(err)
			continue
		}
		set.Insert(key)
	}

	// avoid enqueue a key multiple times
	for key := range set {
		v.queue.Add(key)
	}
}

func (v *DestinationRuleController) handleErr(err error, key interface{}) {
	if err == nil {
		v.queue.Forget(key)
		return
	}

	if v.queue.NumRequeues(key) < maxRetries {
		log.V(2).Info("Error syncing virtualservice for service, retrying.", "key", key, "error", err)
		v.queue.AddRateLimited(key)
		return
	}

	log.V(4).Info("Dropping service out of the queue", "key", key, "error", err)
	v.queue.Forget(key)
	utilruntime.HandleError(err)
}