package mutate

import (
	"context"
	"fmt"

	"github.com/go-logr/logr"
	kyvernov1 "github.com/kyverno/kyverno/api/kyverno/v1"
	kyvernov1beta1 "github.com/kyverno/kyverno/api/kyverno/v1beta1"
	"github.com/kyverno/kyverno/pkg/background/common"
	"github.com/kyverno/kyverno/pkg/client/clientset/versioned"
	kyvernov1listers "github.com/kyverno/kyverno/pkg/client/listers/kyverno/v1"
	"github.com/kyverno/kyverno/pkg/clients/dclient"
	"github.com/kyverno/kyverno/pkg/config"
	engineapi "github.com/kyverno/kyverno/pkg/engine/api"
	"github.com/kyverno/kyverno/pkg/engine/jmespath"
	"github.com/kyverno/kyverno/pkg/event"
	admissionutils "github.com/kyverno/kyverno/pkg/utils/admission"
	engineutils "github.com/kyverno/kyverno/pkg/utils/engine"
	"go.uber.org/multierr"
	admissionv1 "k8s.io/api/admission/v1"
	"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"
)

var ErrEmptyPatch error = fmt.Errorf("empty resource to patch")

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

	// listers
	policyLister  kyvernov1listers.ClusterPolicyLister
	npolicyLister kyvernov1listers.PolicyLister
	nsLister      corev1listers.NamespaceLister

	configuration config.Configuration
	eventGen      event.Interface

	log logr.Logger
	jp  jmespath.Interface
}

// NewMutateExistingController returns an instance of the MutateExistingController
func NewMutateExistingController(
	client dclient.Interface,
	kyvernoClient versioned.Interface,
	statusControl common.StatusControlInterface,
	engine engineapi.Engine,
	policyLister kyvernov1listers.ClusterPolicyLister,
	npolicyLister kyvernov1listers.PolicyLister,
	nsLister corev1listers.NamespaceLister,
	dynamicConfig config.Configuration,
	eventGen event.Interface,
	log logr.Logger,
	jp jmespath.Interface,
) *mutateExistingController {
	c := mutateExistingController{
		client:        client,
		kyvernoClient: kyvernoClient,
		statusControl: statusControl,
		engine:        engine,
		policyLister:  policyLister,
		npolicyLister: npolicyLister,
		nsLister:      nsLister,
		configuration: dynamicConfig,
		eventGen:      eventGen,
		log:           log,
		jp:            jp,
	}
	return &c
}

func (c *mutateExistingController) ProcessUR(ur *kyvernov1beta1.UpdateRequest) error {
	logger := c.log.WithValues("name", ur.GetName(), "policy", ur.Spec.GetPolicyKey(), "resource", ur.Spec.GetResource().String())
	var errs []error

	policy, err := c.getPolicy(ur)
	if err != nil {
		logger.Error(err, "failed to get policy")
		return err
	}

	for _, rule := range policy.GetSpec().Rules {
		if !rule.HasMutateExisting() || ur.Spec.Rule != rule.Name {
			continue
		}

		var trigger *unstructured.Unstructured
		admissionRequest := ur.Spec.Context.AdmissionRequestInfo.AdmissionRequest
		if admissionRequest == nil {
			trigger, err = common.GetResource(c.client, ur.Spec, c.log)
			if err != nil || trigger == nil {
				logger.WithName(rule.Name).Error(err, "failed to get trigger resource")
				if err := updateURStatus(c.statusControl, *ur, err); err != nil {
					return err
				}
				continue
			}
		} else {
			if admissionRequest.Operation == admissionv1.Create {
				trigger, err = common.GetResource(c.client, ur.Spec, c.log)
				if err != nil || trigger == nil {
					if admissionRequest.SubResource == "" {
						logger.WithName(rule.Name).Error(err, "failed to get trigger resource")
						if err := updateURStatus(c.statusControl, *ur, err); err != nil {
							return err
						}
						continue
					} else {
						logger.WithName(rule.Name).Info("trigger resource not found for subresource, reverting to resource in AdmissionReviewRequest", "subresource", admissionRequest.SubResource)
						newResource, _, err := admissionutils.ExtractResources(nil, *admissionRequest)
						if err != nil {
							logger.WithName(rule.Name).Error(err, "failed to extract resources from admission review request")
							errs = append(errs, err)
							continue
						}
						trigger = &newResource
					}
				}
			} else {
				newResource, oldResource, err := admissionutils.ExtractResources(nil, *admissionRequest)
				if err != nil {
					logger.WithName(rule.Name).Error(err, "failed to extract resources from admission review request")
					errs = append(errs, err)
					continue
				}

				trigger = &newResource
				if newResource.Object == nil {
					trigger = &oldResource
				}
			}
		}

		namespaceLabels := engineutils.GetNamespaceSelectorsFromNamespaceLister(trigger.GetKind(), trigger.GetNamespace(), c.nsLister, logger)
		policyContext, err := common.NewBackgroundContext(logger, c.client, ur, policy, trigger, c.configuration, c.jp, namespaceLabels)
		if err != nil {
			logger.WithName(rule.Name).Error(err, "failed to build policy context")
			errs = append(errs, err)
			continue
		}
		if admissionRequest != nil {
			var gvk schema.GroupVersionKind
			gvk, err = c.client.Discovery().GetGVKFromGVR(schema.GroupVersionResource(admissionRequest.Resource))
			if err != nil {
				logger.WithName(rule.Name).Error(err, "failed to get GVK from GVR", "GVR", admissionRequest.Resource)
				errs = append(errs, err)
				continue
			}
			policyContext = policyContext.WithResourceKind(gvk, admissionRequest.SubResource)
		}

		er := c.engine.Mutate(context.TODO(), policyContext)
		for _, r := range er.PolicyResponse.Rules {
			patched, parentGVR, patchedSubresource := r.PatchedTarget()
			switch r.Status() {
			case engineapi.RuleStatusFail, engineapi.RuleStatusError, engineapi.RuleStatusWarn:
				err := fmt.Errorf("failed to mutate existing resource, rule %s, response %v: %s", r.Name(), r.Status(), r.Message())
				logger.Error(err, "")
				errs = append(errs, err)
				c.report(err, policy, rule.Name, patched)

			case engineapi.RuleStatusSkip:
				err := fmt.Errorf("mutate existing rule skipped, rule %s, response %v: %s", r.Name(), r.Status(), r.Message())
				logger.Info(err.Error())

			case engineapi.RuleStatusPass:
				patchedNew := patched
				if patchedNew == nil {
					logger.Error(ErrEmptyPatch, "", "rule", r.Name(), "message", r.Message())
					errs = append(errs, ErrEmptyPatch)
					continue
				}

				patchedNew.SetResourceVersion(patched.GetResourceVersion())
				var updateErr error
				if patchedSubresource == "status" {
					_, updateErr = c.client.UpdateStatusResource(context.TODO(), patchedNew.GetAPIVersion(), patchedNew.GetKind(), patchedNew.GetNamespace(), patchedNew.Object, false)
				} else if patchedSubresource != "" {
					parentResourceGVR := parentGVR
					parentResourceGV := schema.GroupVersion{Group: parentResourceGVR.Group, Version: parentResourceGVR.Version}
					parentResourceGVK, err := c.client.Discovery().GetGVKFromGVR(parentResourceGV.WithResource(parentResourceGVR.Resource))
					if err != nil {
						logger.Error(err, "failed to get GVK from GVR", "GVR", parentResourceGVR)
						errs = append(errs, err)
						continue
					}
					_, updateErr = c.client.UpdateResource(context.TODO(), parentResourceGV.String(), parentResourceGVK.Kind, patchedNew.GetNamespace(), patchedNew.Object, false, patchedSubresource)
				} else {
					_, updateErr = c.client.UpdateResource(context.TODO(), patchedNew.GetAPIVersion(), patchedNew.GetKind(), patchedNew.GetNamespace(), patchedNew.Object, false)
				}
				if updateErr != nil {
					errs = append(errs, updateErr)
					logger.WithName(rule.Name).Error(updateErr, "failed to update target resource", "namespace", patchedNew.GetNamespace(), "name", patchedNew.GetName())
				} else {
					logger.WithName(rule.Name).V(4).Info("successfully mutated existing resource", "namespace", patchedNew.GetNamespace(), "name", patchedNew.GetName())
				}

				c.report(updateErr, policy, rule.Name, patched)
			}
		}
	}

	err = multierr.Combine(errs...)
	return updateURStatus(c.statusControl, *ur, err)
}

func (c *mutateExistingController) getPolicy(ur *kyvernov1beta1.UpdateRequest) (policy kyvernov1.PolicyInterface, err error) {
	pNamespace, pName, err := cache.SplitMetaNamespaceKey(ur.Spec.Policy)
	if err != nil {
		return nil, err
	}

	if pNamespace != "" {
		return c.npolicyLister.Policies(pNamespace).Get(pName)
	}

	return c.policyLister.Get(pName)
}

func (c *mutateExistingController) report(err error, policy kyvernov1.PolicyInterface, rule string, target *unstructured.Unstructured) {
	var events []event.Info

	if target == nil {
		c.log.WithName("mutateExisting").Info("cannot generate events for empty target resource", "policy", policy.GetName(), "rule", rule)
		return
	}

	if err != nil {
		events = event.NewBackgroundFailedEvent(err, policy, rule, event.MutateExistingController,
			kyvernov1.ResourceSpec{Kind: target.GetKind(), Namespace: target.GetNamespace(), Name: target.GetName()})
	} else {
		events = event.NewBackgroundSuccessEvent(event.MutateExistingController, policy,
			[]kyvernov1.ResourceSpec{{Kind: target.GetKind(), Namespace: target.GetNamespace(), Name: target.GetName()}})
	}

	c.eventGen.Add(events...)
}

func updateURStatus(statusControl common.StatusControlInterface, ur kyvernov1beta1.UpdateRequest, err error) error {
	if err != nil {
		if _, err := statusControl.Failed(ur.GetName(), err.Error(), nil); err != nil {
			return err
		}
	} else {
		if _, err := statusControl.Success(ur.GetName(), nil); err != nil {
			return err
		}
	}
	return nil
}