package policystatus

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
	"sync"
	"time"

	v1 "github.com/kyverno/kyverno/pkg/api/kyverno/v1"
	"github.com/kyverno/kyverno/pkg/client/clientset/versioned"
	kyvernolister "github.com/kyverno/kyverno/pkg/client/listers/kyverno/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/util/wait"
	log "sigs.k8s.io/controller-runtime/pkg/log"
)

// Policy status implementation works in the following way,
//Currently policy status maintains a cache of the status of
//each policy.
//Every x unit of time the status of policy is updated using
//the data from the cache.
//The sync exposes a listener which accepts a statusUpdater
//interface which dictates how the status should be updated.
//The status is updated by a worker that receives the interface
//on a channel.
//The worker then updates the current status using the methods
//exposed by the interface.
//Current implementation is designed to be threadsafe with optimised
//locking for each policy.

// statusUpdater defines a type to have a method which
//updates the given status
type statusUpdater interface {
	PolicyName() string
	UpdateStatus(status v1.PolicyStatus) v1.PolicyStatus
}

// Listener ...
type Listener chan statusUpdater

// Send sends an update request
func (l Listener) Send(s statusUpdater) {
	l <- s
}

// Sync is the object which is used to initialize
//the policyStatus sync, can be considered the parent object
//since it contains access to all the persistent data present
//in this package.
type Sync struct {
	cache    *cache
	Listener Listener
	client   *versioned.Clientset
	lister   kyvernolister.ClusterPolicyLister
	nsLister kyvernolister.PolicyLister
}

type cache struct {
	dataMu     sync.RWMutex
	data       map[string]v1.PolicyStatus
	keyToMutex *keyToMutex
}

// NewSync ...
func NewSync(c *versioned.Clientset, lister kyvernolister.ClusterPolicyLister, nsLister kyvernolister.PolicyLister) *Sync {
	return &Sync{
		cache: &cache{
			dataMu:     sync.RWMutex{},
			data:       make(map[string]v1.PolicyStatus),
			keyToMutex: newKeyToMutex(),
		},
		client:   c,
		lister:   lister,
		nsLister: nsLister,
		Listener: make(chan statusUpdater, 20),
	}
}

// Run ...
func (s *Sync) Run(workers int, stopCh <-chan struct{}) {
	for i := 0; i < workers; i++ {
		go s.updateStatusCache(stopCh)
	}

	wait.Until(s.updatePolicyStatus, 10*time.Second, stopCh)
	<-stopCh
}

// updateStatusCache is a worker which updates the current status
//using the statusUpdater interface
func (s *Sync) updateStatusCache(stopCh <-chan struct{}) {
	for {
		select {
		case statusUpdater := <-s.Listener:
			s.cache.keyToMutex.Get(statusUpdater.PolicyName()).Lock()

			s.cache.dataMu.RLock()
			status, exist := s.cache.data[statusUpdater.PolicyName()]
			s.cache.dataMu.RUnlock()
			if !exist {
				policy, _ := s.lister.Get(statusUpdater.PolicyName())
				if policy != nil {
					status = policy.Status
				}
			}
			updatedStatus := statusUpdater.UpdateStatus(status)

			s.cache.dataMu.Lock()
			s.cache.data[statusUpdater.PolicyName()] = updatedStatus
			s.cache.dataMu.Unlock()

			s.cache.keyToMutex.Get(statusUpdater.PolicyName()).Unlock()
			oldStatus, _ := json.Marshal(status)
			newStatus, _ := json.Marshal(updatedStatus)
			log.Log.V(4).Info(fmt.Sprintf("\nupdated status of policy - %v\noldStatus:\n%v\nnewStatus:\n%v\n", statusUpdater.PolicyName(), string(oldStatus), string(newStatus)))
		case <-stopCh:
			return
		}
	}
}

// updatePolicyStatus updates the status in the policy resource definition
//from the status cache, syncing them
func (s *Sync) updatePolicyStatus() {
	s.cache.dataMu.Lock()
	var nameToStatus = make(map[string]v1.PolicyStatus, len(s.cache.data))
	for k, v := range s.cache.data {
		nameToStatus[k] = v
	}
	s.cache.dataMu.Unlock()

	for policyName, status := range nameToStatus {
		// Identify Policy and ClusterPolicy based on namespace in key
		// key = <namespace>/<name> for namespacepolicy and key = <name> for clusterpolicy
		// and update the respective policies
		namespace := ""
		isNamespacedPolicy := false
		key := policyName
		index := strings.Index(policyName, "/")
		if index != -1 {
			namespace = policyName[:index]
			isNamespacedPolicy = true
			policyName = policyName[index+1:]
		}
		if !isNamespacedPolicy {
			policy, err := s.lister.Get(policyName)
			if err != nil {
				continue
			}

			policy.Status = status
			_, err = s.client.KyvernoV1().ClusterPolicies().UpdateStatus(context.TODO(), policy, metav1.UpdateOptions{})
			if err != nil {
				s.cache.dataMu.Lock()
				delete(s.cache.data, policyName)
				s.cache.dataMu.Unlock()
				log.Log.Error(err, "failed to update policy status")
			}
		} else {
			policy, err := s.nsLister.Policies(namespace).Get(policyName)
			if err != nil {
				s.cache.dataMu.Lock()
				delete(s.cache.data, key)
				s.cache.dataMu.Unlock()
				continue
			}
			policy.Status = status
			_, err = s.client.KyvernoV1().Policies(namespace).UpdateStatus(context.TODO(), policy, metav1.UpdateOptions{})
			if err != nil {
				s.cache.dataMu.Lock()
				delete(s.cache.data, key)
				s.cache.dataMu.Unlock()
				log.Log.Error(err, "failed to update namespace policy status")
			}
		}

	}
}