package generate

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"slices"
	"strings"
	"time"

	"github.com/go-logr/logr"
	gojmespath "github.com/kyverno/go-jmespath"
	kyvernov1 "github.com/kyverno/kyverno/api/kyverno/v1"
	kyvernov2 "github.com/kyverno/kyverno/api/kyverno/v2"
	"github.com/kyverno/kyverno/pkg/background/common"
	"github.com/kyverno/kyverno/pkg/breaker"
	"github.com/kyverno/kyverno/pkg/client/clientset/versioned"
	kyvernov1listers "github.com/kyverno/kyverno/pkg/client/listers/kyverno/v1"
	kyvernov2listers "github.com/kyverno/kyverno/pkg/client/listers/kyverno/v2"
	"github.com/kyverno/kyverno/pkg/clients/dclient"
	"github.com/kyverno/kyverno/pkg/config"
	"github.com/kyverno/kyverno/pkg/engine"
	engineapi "github.com/kyverno/kyverno/pkg/engine/api"
	"github.com/kyverno/kyverno/pkg/engine/jmespath"
	regex "github.com/kyverno/kyverno/pkg/engine/variables/regex"
	"github.com/kyverno/kyverno/pkg/event"
	admissionutils "github.com/kyverno/kyverno/pkg/utils/admission"
	engineutils "github.com/kyverno/kyverno/pkg/utils/engine"
	kubeutils "github.com/kyverno/kyverno/pkg/utils/kube"
	reportutils "github.com/kyverno/kyverno/pkg/utils/report"
	validationpolicy "github.com/kyverno/kyverno/pkg/validation/policy"
	"go.uber.org/multierr"
	admissionv1 "k8s.io/api/admission/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime/schema"
	corev1listers "k8s.io/client-go/listers/core/v1"
	"k8s.io/client-go/tools/cache"
)

type GenerateController struct {
	// clients
	client        dclient.Interface
	kyvernoClient versioned.Interface
	statusControl common.StatusControlInterface
	engine        engineapi.Engine

	// listers
	urLister      kyvernov2listers.UpdateRequestNamespaceLister
	nsLister      corev1listers.NamespaceLister
	policyLister  kyvernov1listers.ClusterPolicyLister
	npolicyLister kyvernov1listers.PolicyLister

	configuration config.Configuration
	eventGen      event.Interface

	log logr.Logger
	jp  jmespath.Interface

	reportsConfig  reportutils.ReportingConfiguration
	reportsBreaker breaker.Breaker
}

// NewGenerateController returns an instance of the Generate-Request Controller
func NewGenerateController(
	client dclient.Interface,
	kyvernoClient versioned.Interface,
	statusControl common.StatusControlInterface,
	engine engineapi.Engine,
	policyLister kyvernov1listers.ClusterPolicyLister,
	npolicyLister kyvernov1listers.PolicyLister,
	urLister kyvernov2listers.UpdateRequestNamespaceLister,
	nsLister corev1listers.NamespaceLister,
	dynamicConfig config.Configuration,
	eventGen event.Interface,
	log logr.Logger,
	jp jmespath.Interface,
	reportsConfig reportutils.ReportingConfiguration,
	reportsBreaker breaker.Breaker,
) *GenerateController {
	c := GenerateController{
		client:         client,
		kyvernoClient:  kyvernoClient,
		statusControl:  statusControl,
		engine:         engine,
		policyLister:   policyLister,
		npolicyLister:  npolicyLister,
		urLister:       urLister,
		nsLister:       nsLister,
		configuration:  dynamicConfig,
		eventGen:       eventGen,
		log:            log,
		jp:             jp,
		reportsConfig:  reportsConfig,
		reportsBreaker: reportsBreaker,
	}
	return &c
}

func (c *GenerateController) ProcessUR(ur *kyvernov2.UpdateRequest) error {
	logger := c.log.WithValues("name", ur.GetName(), "policy", ur.Spec.GetPolicyKey())
	var genResources []kyvernov1.ResourceSpec
	logger.V(2).Info("start processing UR", "ur", ur.Name, "resourceVersion", ur.GetResourceVersion())

	var failures []error
	policy, err := c.getPolicyObject(*ur)
	if err != nil && !apierrors.IsNotFound(err) {
		return fmt.Errorf("error in fetching policy: %v", err)
	}

	for i := 0; i < len(ur.Spec.RuleContext); i++ {
		rule := ur.Spec.RuleContext[i]
		trigger, err := c.getTrigger(ur.Spec, i)
		if err != nil || trigger == nil {
			logger.V(4).Info("the trigger resource does not exist or is pending creation")
			failures = append(failures, fmt.Errorf("rule %s failed: failed to fetch trigger resource: %v", rule.Rule, err))
			continue
		}

		genResources, err = c.applyGenerate(*trigger, *ur, policy, i)
		if err != nil {
			if strings.Contains(err.Error(), doesNotApply) {
				logger.V(3).Info(fmt.Sprintf("skipping rule %s: %v", rule.Rule, err.Error()))
			}

			events := event.NewBackgroundFailedEvent(err, policy, ur.Spec.RuleContext[i].Rule, event.GeneratePolicyController,
				kyvernov1.ResourceSpec{Kind: trigger.GetKind(), Namespace: trigger.GetNamespace(), Name: trigger.GetName()})
			c.eventGen.Add(events...)
		}
	}

	return updateStatus(c.statusControl, *ur, multierr.Combine(failures...), genResources)
}

const doesNotApply = "policy does not apply to resource"

func (c *GenerateController) getTrigger(spec kyvernov2.UpdateRequestSpec, i int) (*unstructured.Unstructured, error) {
	resourceSpec := spec.RuleContext[i].Trigger
	c.log.V(4).Info("fetching trigger", "trigger", resourceSpec.String())
	admissionRequest := spec.Context.AdmissionRequestInfo.AdmissionRequest
	if admissionRequest == nil {
		return common.GetResource(c.client, resourceSpec, spec, c.log)
	} else {
		operation := spec.Context.AdmissionRequestInfo.Operation
		if operation == admissionv1.Delete {
			return c.getTriggerForDeleteOperation(spec, i)
		} else if operation == admissionv1.Create {
			return c.getTriggerForCreateOperation(spec, i)
		} else {
			newResource, oldResource, err := admissionutils.ExtractResources(nil, *admissionRequest)
			if err != nil {
				c.log.Error(err, "failed to extract resources from admission review request")
				return nil, err
			}

			trigger := &newResource
			if newResource.Object == nil {
				trigger = &oldResource
			}
			return trigger, nil
		}
	}
}

func (c *GenerateController) getTriggerForDeleteOperation(spec kyvernov2.UpdateRequestSpec, i int) (*unstructured.Unstructured, error) {
	request := spec.Context.AdmissionRequestInfo.AdmissionRequest
	_, oldResource, err := admissionutils.ExtractResources(nil, *request)
	if err != nil {
		return nil, fmt.Errorf("failed to load resource from context: %w", err)
	}
	labels := oldResource.GetLabels()
	resourceSpec := spec.RuleContext[i].Trigger
	if labels[common.GeneratePolicyLabel] != "" {
		// non-trigger deletion, get trigger from ur spec
		c.log.V(4).Info("non-trigger resource is deleted, fetching the trigger from the UR spec", "trigger", spec.Resource.String())
		return common.GetResource(c.client, resourceSpec, spec, c.log)
	}
	return &oldResource, nil
}

func (c *GenerateController) getTriggerForCreateOperation(spec kyvernov2.UpdateRequestSpec, i int) (*unstructured.Unstructured, error) {
	admissionRequest := spec.Context.AdmissionRequestInfo.AdmissionRequest
	resourceSpec := spec.RuleContext[i].Trigger
	trigger, err := common.GetResource(c.client, resourceSpec, spec, c.log)
	if err != nil || trigger == nil {
		if admissionRequest.SubResource == "" {
			return nil, err
		} else {
			c.log.V(4).Info("trigger resource not found for subresource, reverting to resource in AdmissionReviewRequest", "subresource", admissionRequest.SubResource)
			newResource, _, err := admissionutils.ExtractResources(nil, *admissionRequest)
			if err != nil {
				c.log.Error(err, "failed to extract resources from admission review request")
				return nil, err
			}
			return &newResource, nil
		}
	}
	return trigger, err
}

func (c *GenerateController) applyGenerate(trigger unstructured.Unstructured, ur kyvernov2.UpdateRequest, policy kyvernov1.PolicyInterface, i int) ([]kyvernov1.ResourceSpec, error) {
	logger := c.log.WithValues("name", ur.GetName(), "policy", ur.Spec.GetPolicyKey())
	logger.V(3).Info("applying generate policy")

	ruleContext := ur.Spec.RuleContext[i]
	if ruleContext.DeleteDownstream || policy == nil {
		return nil, c.deleteDownstream(policy, ruleContext, &ur)
	}

	p, ok := buildPolicyWithAppliedRules(policy, ruleContext.Rule)
	if !ok {
		logger.V(4).Info("skip rule application as the rule does not exist in the updaterequest", "rule", ruleContext.Rule)
		return nil, nil
	}

	namespaceLabels := engineutils.GetNamespaceSelectorsFromNamespaceLister(trigger.GetKind(), trigger.GetNamespace(), c.nsLister, logger)
	policyContext, err := common.NewBackgroundContext(logger, c.client, ur.Spec.Context, p, &trigger, c.configuration, c.jp, namespaceLabels)
	if err != nil {
		return nil, err
	}

	admissionRequest := ur.Spec.Context.AdmissionRequestInfo.AdmissionRequest
	if admissionRequest != nil {
		var gvk schema.GroupVersionKind
		gvk, err = c.client.Discovery().GetGVKFromGVR(schema.GroupVersionResource(admissionRequest.Resource))
		if err != nil {
			return nil, err
		}
		policyContext = policyContext.WithResourceKind(gvk, admissionRequest.SubResource)
	}

	// check if the policy still applies to the resource
	engineResponse := c.engine.Generate(context.Background(), policyContext)
	if len(engineResponse.PolicyResponse.Rules) == 0 {
		logger.V(4).Info(doesNotApply)
		return nil, errors.New(doesNotApply)
	}

	var applicableRules []string
	for _, r := range engineResponse.PolicyResponse.Rules {
		if r.Status() == engineapi.RuleStatusPass {
			applicableRules = append(applicableRules, r.Name())
		}
	}

	// Apply the generate rule on resource
	genResourcesMap, err := c.ApplyGeneratePolicy(logger, policyContext, applicableRules)
	if err != nil {
		return nil, err
	}

	for i, v := range engineResponse.PolicyResponse.Rules {
		if resources, ok := genResourcesMap[v.Name()]; ok {
			unstResources, err := c.GetUnstrResources(resources)
			if err != nil {
				c.log.Error(err, "failed to get unst resource names report")
			}
			engineResponse.PolicyResponse.Rules[i] = *v.WithGeneratedResources(unstResources)
		}
	}

	if c.needsReports(trigger) {
		if err := c.createReports(context.TODO(), policyContext.NewResource(), engineResponse); err != nil {
			c.log.Error(err, "failed to create report")
		}
	}

	genResources := make([]kyvernov1.ResourceSpec, 0)
	for _, v := range genResourcesMap {
		genResources = append(genResources, v...)
	}

	for _, res := range genResources {
		e := event.NewResourceGenerationEvent(ur.Spec.Policy, ur.Spec.RuleContext[i].Rule, event.GeneratePolicyController, res)
		c.eventGen.Add(e)
	}

	e := event.NewBackgroundSuccessEvent(event.GeneratePolicyController, policy, genResources)
	c.eventGen.Add(e...)

	return genResources, err
}

// getPolicyObject gets the policy spec from the ClusterPolicy/Policy
func (c *GenerateController) getPolicyObject(ur kyvernov2.UpdateRequest) (kyvernov1.PolicyInterface, error) {
	pNamespace, pName, err := cache.SplitMetaNamespaceKey(ur.Spec.Policy)
	if err != nil {
		return nil, err
	}

	if pNamespace == "" {
		policyObj, err := c.policyLister.Get(pName)
		if err != nil {
			return nil, err
		}
		return policyObj, err
	}
	npolicyObj, err := c.npolicyLister.Policies(pNamespace).Get(pName)
	if err != nil {
		return nil, err
	}
	return npolicyObj, nil
}

func (c *GenerateController) ApplyGeneratePolicy(log logr.Logger, policyContext *engine.PolicyContext, applicableRules []string) (map[string][]kyvernov1.ResourceSpec, error) {
	genResources := make(map[string][]kyvernov1.ResourceSpec)
	policy := policyContext.Policy()
	resource := policyContext.NewResource()
	// To manage existing resources, we compare the creation time for the default resource to be generated and policy creation time
	ruleNameToProcessingTime := make(map[string]time.Duration)
	applyRules := policy.GetSpec().GetApplyRules()
	applyCount := 0
	log = log.WithValues("policy", policy.GetName(), "trigger", resource.GetNamespace()+"/"+resource.GetName())

	for _, rule := range policy.GetSpec().Rules {
		var err error
		if !rule.HasGenerate() {
			continue
		}

		if !slices.Contains(applicableRules, rule.Name) {
			continue
		}
		if rule.Generation.Synchronize {
			ruleRaw, err := json.Marshal(rule.DeepCopy())
			if err != nil {
				return nil, fmt.Errorf("failed to serialize the policy: %v", err)
			}
			vars := regex.RegexVariables.FindAllStringSubmatch(string(ruleRaw), -1)

			for _, s := range vars {
				for _, banned := range validationpolicy.ForbiddenUserVariables {
					if banned.Match([]byte(s[2])) {
						log.V(2).Info("warning: resources with admission request variables may not be regenerated", "policy", policy.GetName(), "rule", rule.Name, "variable", s[2])
					}
				}
			}
		}

		startTime := time.Now()
		var genResource []kyvernov1.ResourceSpec
		if applyRules == kyvernov1.ApplyOne && applyCount > 0 {
			break
		}
		logger := log.WithValues("rule", rule.Name)
		contextLoader := c.engine.ContextLoader(policy, rule)
		if err := contextLoader(context.TODO(), rule.Context, policyContext.JSONContext()); err != nil {
			if _, ok := err.(gojmespath.NotFoundError); ok {
				logger.V(3).Info("failed to load rule level context", "reason", err.Error())
			} else {
				logger.Error(err, "failed to load rule level context")
			}
			return nil, fmt.Errorf("failed to load rule level context: %v", err)
		}

		if rule.Generation.ForEachGeneration != nil {
			g := newForeachGenerator(c.client, logger, policyContext, policy, rule, rule.Context, rule.GetAnyAllConditions(), policyContext.NewResource(), rule.Generation.ForEachGeneration, contextLoader)
			genResource, err = g.generateForeach()
		} else {
			g := newGenerator(c.client, logger, policyContext, policy, rule, rule.Context, rule.GetAnyAllConditions(), policyContext.NewResource(), rule.Generation.GeneratePattern, contextLoader)
			genResource, err = g.generate()
		}

		if err != nil {
			log.Error(err, "failed to apply generate rule")
			return nil, err
		}
		ruleNameToProcessingTime[rule.Name] = time.Since(startTime)
		genResources[rule.Name] = genResource
		applyCount++
	}

	return genResources, nil
}

// NewGenerateControllerWithOnlyClient returns an instance of Controller with only the client.
func NewGenerateControllerWithOnlyClient(client dclient.Interface, engine engineapi.Engine) *GenerateController {
	c := GenerateController{
		client: client,
		engine: engine,
	}
	return &c
}

// GetUnstrResource converts ResourceSpec object to type Unstructured
func (c *GenerateController) GetUnstrResources(genResourceSpecs []kyvernov1.ResourceSpec) ([]*unstructured.Unstructured, error) {
	resources := []*unstructured.Unstructured{}
	for _, genResourceSpec := range genResourceSpecs {
		resource, err := c.client.GetResource(context.TODO(), genResourceSpec.APIVersion, genResourceSpec.Kind, genResourceSpec.Namespace, genResourceSpec.Name)
		if err != nil {
			return nil, err
		}
		resources = append(resources, resource)
	}
	return resources, nil
}

func (c *GenerateController) needsReports(trigger unstructured.Unstructured) bool {
	createReport := c.reportsConfig.GenerateReportsEnabled()
	// check if the resource supports reporting
	if !reportutils.IsGvkSupported(trigger.GroupVersionKind()) {
		createReport = false
	}

	return createReport
}

func (c *GenerateController) createReports(
	ctx context.Context,
	resource unstructured.Unstructured,
	engineResponses ...engineapi.EngineResponse,
) error {
	report := reportutils.BuildGenerateReport(resource.GetNamespace(), resource.GroupVersionKind(), resource.GetName(), resource.GetUID(), engineResponses...)
	if len(report.GetResults()) > 0 {
		err := c.reportsBreaker.Do(ctx, func(ctx context.Context) error {
			_, err := reportutils.CreateReport(ctx, report, c.kyvernoClient)
			return err
		})
		if err != nil {
			return err
		}
	}
	return nil
}

func updateStatus(statusControl common.StatusControlInterface, ur kyvernov2.UpdateRequest, err error, genResources []kyvernov1.ResourceSpec) error {
	if err != nil {
		if _, err := statusControl.Failed(ur.GetName(), err.Error(), genResources); err != nil {
			return err
		}
	} else {
		if _, err := statusControl.Success(ur.GetName(), genResources); err != nil {
			return err
		}
	}
	return nil
}

func GetUnstrRule(rule *kyvernov1.Generation) (*unstructured.Unstructured, error) {
	ruleData, err := json.Marshal(rule)
	if err != nil {
		return nil, err
	}
	return kubeutils.BytesToUnstructured(ruleData)
}