package policy

import (
	"context"
	"crypto/rand"
	"fmt"
	"math/big"
	"reflect"
	"time"

	"github.com/go-logr/logr"
	kyverno "github.com/kyverno/kyverno/pkg/api/kyverno/v1"
	kyvernoclient "github.com/kyverno/kyverno/pkg/client/clientset/versioned"
	"github.com/kyverno/kyverno/pkg/client/clientset/versioned/scheme"
	kyvernoinformer "github.com/kyverno/kyverno/pkg/client/informers/externalversions/kyverno/v1"
	kyvernolister "github.com/kyverno/kyverno/pkg/client/listers/kyverno/v1"
	"github.com/kyverno/kyverno/pkg/config"
	client "github.com/kyverno/kyverno/pkg/dclient"
	"github.com/kyverno/kyverno/pkg/event"
	"github.com/kyverno/kyverno/pkg/policyreport"
	"github.com/kyverno/kyverno/pkg/resourcecache"
	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"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/wait"
	informers "k8s.io/client-go/informers/core/v1"
	typedcorev1 "k8s.io/client-go/kubernetes/typed/core/v1"
	listerv1 "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"
)

const (
	// maxRetries is the number of times a Policy 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 times
	// a deployment is going to be requeued:
	//
	// 5ms, 10ms, 20ms, 40ms, 80ms, 160ms, 320ms, 640ms, 1.3s, 2.6s, 5.1s, 10.2s, 20.4s, 41s, 82s
	maxRetries = 15
)

// PolicyController is responsible for synchronizing Policy objects stored
// in the system with the corresponding policy violations
type PolicyController struct {
	client        *client.Client
	kyvernoClient *kyvernoclient.Clientset
	eventGen      event.Interface
	eventRecorder record.EventRecorder

	// Policies that need to be synced
	queue workqueue.RateLimitingInterface

	// pLister can list/get policy from the shared informer's store
	pLister kyvernolister.ClusterPolicyLister

	// npLister can list/get namespace policy from the shared informer's store
	npLister kyvernolister.PolicyLister

	// grLister can list/get generate request from the shared informer's store
	grLister kyvernolister.GenerateRequestLister

	// nsLister can list/get namespaces from the shared informer's store
	nsLister listerv1.NamespaceLister

	// pListerSynced returns true if the cluster policy store has been synced at least once
	pListerSynced cache.InformerSynced

	// npListerSynced returns true if the namespace policy store has been synced at least once
	npListerSynced cache.InformerSynced

	// pvListerSynced returns true if the cluster policy violation store has been synced at least once
	cpvListerSynced cache.InformerSynced

	// pvListerSynced returns true if the policy violation store has been synced at least once
	nspvListerSynced cache.InformerSynced

	// nsListerSynced returns true if the namespace store has been synced at least once
	nsListerSynced cache.InformerSynced

	// grListerSynced returns true if the generate request store has been synced at least once
	grListerSynced cache.InformerSynced

	// Resource manager, manages the mapping for already processed resource
	rm resourceManager

	// helpers to validate against current loaded configuration
	configHandler config.Interface

	// policy report generator
	prGenerator policyreport.GeneratorInterface

	// resCache - controls creation and fetching of resource informer cache
	resCache resourcecache.ResourceCacheIface

	log logr.Logger
}

// NewPolicyController create a new PolicyController
func NewPolicyController(kyvernoClient *kyvernoclient.Clientset,
	client *client.Client,
	pInformer kyvernoinformer.ClusterPolicyInformer,
	npInformer kyvernoinformer.PolicyInformer,
	grInformer kyvernoinformer.GenerateRequestInformer,
	configHandler config.Interface,
	eventGen event.Interface,
	prGenerator policyreport.GeneratorInterface,
	namespaces informers.NamespaceInformer,
	log logr.Logger,
	resCache resourcecache.ResourceCacheIface) (*PolicyController, error) {

	// Event broad caster
	eventBroadcaster := record.NewBroadcaster()
	eventBroadcaster.StartLogging(log.V(5).Info)
	eventInterface, err := client.GetEventsInterface()
	if err != nil {
		return nil, err
	}
	eventBroadcaster.StartRecordingToSink(&typedcorev1.EventSinkImpl{Interface: eventInterface})

	pc := PolicyController{
		client:        client,
		kyvernoClient: kyvernoClient,
		eventGen:      eventGen,
		eventRecorder: eventBroadcaster.NewRecorder(scheme.Scheme, v1.EventSource{Component: "policy_controller"}),
		queue:         workqueue.NewNamedRateLimitingQueue(workqueue.DefaultControllerRateLimiter(), "policy"),
		configHandler: configHandler,
		prGenerator:   prGenerator,
		log:           log,
		resCache:      resCache,
	}

	pInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc:    pc.addPolicy,
		UpdateFunc: pc.updatePolicy,
		DeleteFunc: pc.deletePolicy,
	})

	npInformer.Informer().AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc:    pc.addNsPolicy,
		UpdateFunc: pc.updateNsPolicy,
		DeleteFunc: pc.deleteNsPolicy,
	})

	pc.pLister = pInformer.Lister()
	pc.npLister = npInformer.Lister()

	pc.nsLister = namespaces.Lister()
	pc.grLister = grInformer.Lister()
	pc.pListerSynced = pInformer.Informer().HasSynced
	pc.npListerSynced = npInformer.Informer().HasSynced

	pc.nsListerSynced = namespaces.Informer().HasSynced
	pc.grListerSynced = grInformer.Informer().HasSynced

	// resource manager
	// rebuild after 300 seconds/ 5 mins
	//TODO: pass the time in seconds instead of converting it internally
	pc.rm = NewResourceManager(30)

	return &pc, nil
}

func (pc *PolicyController) canBackgroundProcess(p *kyverno.ClusterPolicy) bool {
	logger := pc.log.WithValues("policy", p.Name)
	if !p.BackgroundProcessingEnabled() {
		logger.V(4).Info("background processed is disabled")
		return false
	}

	if err := ContainsVariablesOtherThanObject(*p); err != nil {
		logger.V(4).Info("policy cannot be processed in the background")
		return false
	}

	return true
}

func (pc *PolicyController) addPolicy(obj interface{}) {
	logger := pc.log
	p := obj.(*kyverno.ClusterPolicy)

	logger.Info("policy created event", "uid", p.UID, "kind", "ClusterPolicy", "policy_name", p.Name)

	if !pc.canBackgroundProcess(p) {
		return
	}

	logger.V(4).Info("queuing policy for background processing", "name", p.Name)
	pc.enqueuePolicy(p)
}

func (pc *PolicyController) updatePolicy(old, cur interface{}) {
	logger := pc.log
	oldP := old.(*kyverno.ClusterPolicy)
	curP := cur.(*kyverno.ClusterPolicy)

	if !pc.canBackgroundProcess(curP) {
		return
	}

	if reflect.DeepEqual(oldP.Spec, curP.Spec) {
		return
	}

	logger.V(4).Info("updating policy", "name", oldP.Name)

	pc.enqueueRCRDeletedRule(oldP, curP)
	pc.enqueuePolicy(curP)
}

func (pc *PolicyController) deletePolicy(obj interface{}) {
	logger := pc.log
	p, ok := obj.(*kyverno.ClusterPolicy)
	if !ok {
		tombstone, ok := obj.(cache.DeletedFinalStateUnknown)
		if !ok {
			logger.Info("couldn't get object from tombstone", "obj", obj)
			return
		}

		p, ok = tombstone.Obj.(*kyverno.ClusterPolicy)
		if !ok {
			logger.Info("tombstone container object that is not a policy", "obj", obj)
			return
		}
	}

	logger.Info("policy deleted event", "uid", p.UID, "kind", "ClusterPolicy", "policy_name", p.Name)

	// we process policies that are not set of background processing
	// as we need to clean up GRs when a policy is deleted
	pc.enqueuePolicy(p)
	pc.enqueueRCRDeletedPolicy(p.Name)
}

func (pc *PolicyController) addNsPolicy(obj interface{}) {
	logger := pc.log
	p := obj.(*kyverno.Policy)

	logger.Info("policy created event", "uid", p.UID, "kind", "Policy", "policy_name", p.Name, "namespaces", p.Namespace)

	pol := ConvertPolicyToClusterPolicy(p)
	if !pc.canBackgroundProcess(pol) {
		return
	}
	logger.V(4).Info("queuing policy for background processing", "namespace", pol.Namespace, "name", pol.Name)
	pc.enqueuePolicy(pol)
}

func (pc *PolicyController) updateNsPolicy(old, cur interface{}) {
	logger := pc.log
	oldP := old.(*kyverno.Policy)
	curP := cur.(*kyverno.Policy)
	ncurP := ConvertPolicyToClusterPolicy(curP)
	if !pc.canBackgroundProcess(ncurP) {
		return
	}

	if reflect.DeepEqual(oldP.Spec, curP.Spec) {
		return
	}

	logger.V(4).Info("updating namespace policy", "namespace", oldP.Namespace, "name", oldP.Name)

	pc.enqueueRCRDeletedRule(ConvertPolicyToClusterPolicy(oldP), ncurP)
	pc.enqueuePolicy(ncurP)
}

func (pc *PolicyController) deleteNsPolicy(obj interface{}) {
	logger := pc.log
	p, ok := obj.(*kyverno.Policy)
	if !ok {
		tombstone, ok := obj.(cache.DeletedFinalStateUnknown)
		if !ok {
			logger.Info("couldn't get object from tombstone", "obj", obj)
			return
		}

		p, ok = tombstone.Obj.(*kyverno.Policy)
		if !ok {
			logger.Info("tombstone container object that is not a policy", "obj", obj)
			return
		}
	}

	logger.Info("policy deleted event", "uid", p.UID, "kind", "Policy", "policy_name", p.Name, "namespaces", p.Namespace)

	pol := ConvertPolicyToClusterPolicy(p)

	// we process policies that are not set of background processing
	// as we need to clean up GRs when a policy is deleted
	pc.enqueuePolicy(pol)
	pc.enqueueRCRDeletedPolicy(p.Name)
}

func (pc *PolicyController) enqueueRCRDeletedRule(old, cur *kyverno.ClusterPolicy) {
	curRule := make(map[string]bool)
	for _, rule := range cur.Spec.Rules {
		curRule[rule.Name] = true
	}

	for _, rule := range old.Spec.Rules {
		if !curRule[rule.Name] {
			pc.prGenerator.Add(policyreport.Info{
				PolicyName: cur.GetName(),
				Results: []policyreport.EngineResponseResult{
					{
						Rules: []kyverno.ViolatedRule{
							{Name: rule.Name},
						},
					},
				},
			})
		}
	}
}

func (pc *PolicyController) enqueueRCRDeletedPolicy(policyName string) {
	pc.prGenerator.Add(policyreport.Info{
		PolicyName: policyName,
	})
}

func (pc *PolicyController) enqueuePolicy(policy *kyverno.ClusterPolicy) {
	logger := pc.log
	key, err := cache.MetaNamespaceKeyFunc(policy)
	if err != nil {
		logger.Error(err, "failed to enqueue policy")
		return
	}
	pc.queue.Add(key)
}

// Run begins watching and syncing.
func (pc *PolicyController) Run(workers int, stopCh <-chan struct{}) {
	logger := pc.log

	defer utilruntime.HandleCrash()
	defer pc.queue.ShutDown()

	logger.Info("starting")
	defer logger.Info("shutting down")

	if !cache.WaitForCacheSync(stopCh, pc.pListerSynced, pc.npListerSynced, pc.nsListerSynced, pc.grListerSynced) {
		logger.Info("failed to sync informer cache")
		return
	}

	for i := 0; i < workers; i++ {
		go wait.Until(pc.worker, time.Second, stopCh)
	}
	<-stopCh
}

// worker runs a worker thread that just dequeues items, processes them, and marks them done.
// It enforces that the syncHandler is never invoked concurrently with the same key.
func (pc *PolicyController) worker() {
	for pc.processNextWorkItem() {
	}
}

func (pc *PolicyController) processNextWorkItem() bool {
	key, quit := pc.queue.Get()
	if quit {
		return false
	}
	defer pc.queue.Done(key)
	err := pc.syncPolicy(key.(string))
	pc.handleErr(err, key)

	return true
}

func (pc *PolicyController) handleErr(err error, key interface{}) {
	logger := pc.log
	if err == nil {
		pc.queue.Forget(key)
		return
	}

	if pc.queue.NumRequeues(key) < maxRetries {
		logger.Error(err, "failed to sync policy", "key", key)
		pc.queue.AddRateLimited(key)
		return
	}

	utilruntime.HandleError(err)
	logger.V(2).Info("dropping policy out of queue", "key", key)
	pc.queue.Forget(key)
}

func (pc *PolicyController) syncPolicy(key string) error {
	logger := pc.log.WithName("syncPolicy")
	startTime := time.Now()
	logger.V(4).Info("started syncing policy", "key", key, "startTime", startTime)
	defer func() {
		logger.V(4).Info("finished syncing policy", "key", key, "processingTime", time.Since(startTime).String())
	}()

	grList, err := pc.grLister.List(labels.Everything())
	if err != nil {
		logger.Error(err, "failed to list generate request")
	}

	policy, err := pc.getPolicy(key)
	if err != nil {
		if errors.IsNotFound(err) {
			deleteGR(pc.kyvernoClient, key, grList, logger)
			return nil
		}

		return err
	}

	updateGR(pc.kyvernoClient, policy.Name, grList, logger)
	pc.processExistingResources(policy)
	return nil
}

func (pc *PolicyController) getPolicy(key string) (policy *kyverno.ClusterPolicy, err error) {
	namespace, key, isNamespacedPolicy := parseNamespacedPolicy(key)
	if !isNamespacedPolicy {
		return pc.pLister.Get(key)
	}

	nsPolicy, err := pc.npLister.Policies(namespace).Get(key)
	if err == nil && nsPolicy != nil {
		policy = ConvertPolicyToClusterPolicy(nsPolicy)
	}

	return
}

func deleteGR(kyvernoClient *kyvernoclient.Clientset, policyKey string, grList []*kyverno.GenerateRequest, logger logr.Logger) {
	for _, v := range grList {
		if policyKey == v.Spec.Policy {
			err := kyvernoClient.KyvernoV1().GenerateRequests(config.KyvernoNamespace).Delete(context.TODO(), v.GetName(), metav1.DeleteOptions{})
			if err != nil && !errors.IsNotFound(err) {
				logger.Error(err, "failed to delete gr", "name", v.GetName())
			}
		}
	}
}

func updateGR(kyvernoClient *kyvernoclient.Clientset, policyKey string, grList []*kyverno.GenerateRequest, logger logr.Logger) {
	for _, gr := range grList {
		if policyKey == gr.Spec.Policy {
			grLabels := gr.Labels
			if len(grLabels) == 0 {
				grLabels = make(map[string]string)
			}

			nBig, err := rand.Int(rand.Reader, big.NewInt(100000))
			if err != nil {
				logger.Error(err, "failed to generate random interger")
			}
			grLabels["policy-update"] = fmt.Sprintf("revision-count-%d", nBig.Int64())
			gr.SetLabels(grLabels)

			_, err = kyvernoClient.KyvernoV1().GenerateRequests(config.KyvernoNamespace).Update(context.TODO(), gr, metav1.UpdateOptions{})
			if err != nil {
				logger.Error(err, "failed to update gr", "name", gr.GetName())
			}
		}
	}
}