package policy

import (
	"errors"
	"strings"
	"sync"
	"time"

	"github.com/go-logr/logr"
	kyvernov1 "github.com/kyverno/kyverno/api/kyverno/v1"
	"github.com/kyverno/kyverno/pkg/autogen"
	"github.com/kyverno/kyverno/pkg/common"
	"github.com/kyverno/kyverno/pkg/engine"
	"github.com/kyverno/kyverno/pkg/engine/response"
	"github.com/kyverno/kyverno/pkg/metrics"
	policyExecutionDuration "github.com/kyverno/kyverno/pkg/metrics/policyexecutionduration"
	policyResults "github.com/kyverno/kyverno/pkg/metrics/policyresults"
	kubeutils "github.com/kyverno/kyverno/pkg/utils/kube"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
)

func (pc *PolicyController) processExistingResources(policy kyvernov1.PolicyInterface) {
	logger := pc.log.WithValues("policy", policy.GetName())
	logger.V(4).Info("applying policy to existing resources")

	// Parse through all the resources drops the cache after configured rebuild time
	pc.rm.Drop()

	for _, rule := range autogen.ComputeRules(policy) {
		if !rule.HasValidate() && !rule.HasVerifyImages() {
			continue
		}
		matchKinds := rule.MatchResources.GetKinds()
		pc.processExistingKinds(matchKinds, policy, rule, logger)
	}
}

func (pc *PolicyController) applyAndReportPerNamespace(policy kyvernov1.PolicyInterface, kind string, ns string, rule kyvernov1.Rule, logger logr.Logger, metricAlreadyRegistered *bool) {
	rMap := pc.getResourcesPerNamespace(kind, ns, rule, logger)
	excludeAutoGenResources(policy, rMap, logger)
	if len(rMap) == 0 {
		return
	}

	var engineResponses []*response.EngineResponse
	for _, resource := range rMap {
		responses := pc.applyPolicy(policy, resource, logger)
		engineResponses = append(engineResponses, responses...)
	}

	if !*metricAlreadyRegistered && len(engineResponses) > 0 {
		for _, engineResponse := range engineResponses {
			// registering the kyverno_policy_results_total metric concurrently
			go pc.registerPolicyResultsMetricValidation(logger, policy, *engineResponse)
			// registering the kyverno_policy_execution_duration_seconds metric concurrently
			go pc.registerPolicyExecutionDurationMetricValidate(logger, policy, *engineResponse)
		}
		*metricAlreadyRegistered = true
	}

	pc.report(engineResponses, logger)
}

func (pc *PolicyController) registerPolicyResultsMetricValidation(logger logr.Logger, policy kyvernov1.PolicyInterface, engineResponse response.EngineResponse) {
	if err := policyResults.ProcessEngineResponse(pc.metricsConfig, policy, engineResponse, metrics.BackgroundScan, metrics.ResourceCreated); err != nil {
		logger.Error(err, "error occurred while registering kyverno_policy_results_total metrics for the above policy", "name", policy.GetName())
	}
}

func (pc *PolicyController) registerPolicyExecutionDurationMetricValidate(logger logr.Logger, policy kyvernov1.PolicyInterface, engineResponse response.EngineResponse) {
	if err := policyExecutionDuration.ProcessEngineResponse(pc.metricsConfig, policy, engineResponse, metrics.BackgroundScan, "", metrics.ResourceCreated); err != nil {
		logger.Error(err, "error occurred while registering kyverno_policy_execution_duration_seconds metrics for the above policy", "name", policy.GetName())
	}
}

func (pc *PolicyController) applyPolicy(policy kyvernov1.PolicyInterface, resource unstructured.Unstructured, logger logr.Logger) (engineResponses []*response.EngineResponse) {
	// pre-processing, check if the policy and resource version has been processed before
	if !pc.rm.ProcessResource(policy.GetName(), policy.GetResourceVersion(), resource.GetKind(), resource.GetNamespace(), resource.GetName(), resource.GetResourceVersion()) {
		logger.V(4).Info("policy and resource already processed", "policyResourceVersion", policy.GetResourceVersion(), "resourceResourceVersion", resource.GetResourceVersion(), "kind", resource.GetKind(), "namespace", resource.GetNamespace(), "name", resource.GetName())
	}

	namespaceLabels := common.GetNamespaceSelectorsFromNamespaceLister(resource.GetKind(), resource.GetNamespace(), pc.nsLister, logger)
	engineResponse := applyPolicy(policy, resource, logger, pc.configHandler.GetExcludeGroupRole(), pc.client, namespaceLabels)
	engineResponses = append(engineResponses, engineResponse...)

	// post-processing, register the resource as processed
	pc.rm.RegisterResource(policy.GetName(), policy.GetResourceVersion(), resource.GetKind(), resource.GetNamespace(), resource.GetName(), resource.GetResourceVersion())

	return
}

// excludeAutoGenResources filter out the pods / jobs with ownerReference
func excludeAutoGenResources(policy kyvernov1.PolicyInterface, resourceMap map[string]unstructured.Unstructured, log logr.Logger) {
	for uid, r := range resourceMap {
		if engine.ManagedPodResource(policy, r) {
			log.V(4).Info("exclude resource", "namespace", r.GetNamespace(), "kind", r.GetKind(), "name", r.GetName())
			delete(resourceMap, uid)
		}
	}
}

// Condition defines condition type
type Condition int

const (
	// NotEvaluate to not evaluate condition
	NotEvaluate Condition = 0
	// Process to evaluate condition
	Process Condition = 1
	// Skip to ignore/skip the condition
	Skip Condition = 2
)

// NewResourceManager returns a new ResourceManager
func NewResourceManager(rebuildTime int64) *ResourceManager {
	rm := ResourceManager{
		scope:       make(map[string]bool),
		data:        make(map[string]interface{}),
		time:        time.Now(),
		rebuildTime: rebuildTime,
	}
	// set time it was built
	return &rm
}

// ResourceManager stores the details on already processed resources for caching
type ResourceManager struct {
	// we drop and re-build the cache
	// based on the memory consumer of by the map
	scope       map[string]bool
	data        map[string]interface{}
	mux         sync.RWMutex
	time        time.Time
	rebuildTime int64 // after how many seconds should we rebuild the cache
}

type resourceManager interface {
	ProcessResource(policy, pv, kind, ns, name, rv string) bool
	// TODO	removeResource(kind, ns, name string) error
	RegisterResource(policy, pv, kind, ns, name, rv string)
	RegisterScope(kind string, namespaced bool)
	GetScope(kind string) (bool, error)
	Drop()
}

// Drop drop the cache after every rebuild interval mins
func (rm *ResourceManager) Drop() {
	timeSince := time.Since(rm.time)
	if timeSince > time.Duration(rm.rebuildTime)*time.Second {
		rm.mux.Lock()
		defer rm.mux.Unlock()
		rm.data = map[string]interface{}{}
		rm.time = time.Now()
	}
}

var empty struct{}

// RegisterResource stores if the policy is processed on this resource version
func (rm *ResourceManager) RegisterResource(policy, pv, kind, ns, name, rv string) {
	rm.mux.Lock()
	defer rm.mux.Unlock()
	// add the resource
	key := buildKey(policy, pv, kind, ns, name, rv)
	rm.data[key] = empty
}

// ProcessResource returns true if the policy was not applied on the resource
func (rm *ResourceManager) ProcessResource(policy, pv, kind, ns, name, rv string) bool {
	rm.mux.RLock()
	defer rm.mux.RUnlock()

	key := buildKey(policy, pv, kind, ns, name, rv)
	_, ok := rm.data[key]
	return !ok
}

// RegisterScope stores the scope of the given kind
func (rm *ResourceManager) RegisterScope(kind string, namespaced bool) {
	rm.mux.Lock()
	defer rm.mux.Unlock()

	rm.scope[kind] = namespaced
}

// GetScope gets the scope of the given kind
// return error if kind is not registered
func (rm *ResourceManager) GetScope(kind string) (bool, error) {
	rm.mux.RLock()
	defer rm.mux.RUnlock()

	namespaced, ok := rm.scope[kind]
	if !ok {
		return false, errors.New("NotFound")
	}

	return namespaced, nil
}

func buildKey(policy, pv, kind, ns, name, rv string) string {
	return policy + "/" + pv + "/" + kind + "/" + ns + "/" + name + "/" + rv
}

func (pc *PolicyController) processExistingKinds(kinds []string, policy kyvernov1.PolicyInterface, rule kyvernov1.Rule, logger logr.Logger) {
	for _, kind := range kinds {
		logger = logger.WithValues("rule", rule.Name, "kind", kind)
		_, err := pc.rm.GetScope(kind)
		if err != nil {
			gv, k := kubeutils.GetKindFromGVK(kind)
			if !strings.Contains(k, "*") {
				resourceSchema, _, err := pc.client.Discovery().FindResource(gv, k)
				if err != nil {
					logger.Error(err, "failed to find resource", "kind", k)
					continue
				}
				pc.rm.RegisterScope(k, resourceSchema.Namespaced)
			}
		}

		// this tracker would help to ensure that even for multiple namespaces, duplicate metric are not generated
		metricRegisteredTracker := false

		if policy.GetNamespace() != "" {
			ns := policy.GetNamespace()
			pc.applyAndReportPerNamespace(policy, kind, ns, rule, logger.WithValues("kind", kind).WithValues("ns", ns), &metricRegisteredTracker)
			continue
		}

		pc.applyAndReportPerNamespace(policy, kind, "", rule, logger.WithValues("kind", kind), &metricRegisteredTracker)
	}
}