/*
Copyright 2022 The Karmada Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package search

import (
	"fmt"
	"reflect"
	"strings"
	"sync"
	"time"

	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/api/meta"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/kubernetes"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/util/workqueue"
	"k8s.io/klog/v2"
	"sigs.k8s.io/controller-runtime/pkg/client"

	clusterv1alpha1 "github.com/karmada-io/karmada/pkg/apis/cluster/v1alpha1"
	policyv1alpha1 "github.com/karmada-io/karmada/pkg/apis/policy/v1alpha1"
	searchv1alpha1 "github.com/karmada-io/karmada/pkg/apis/search/v1alpha1"
	informerfactory "github.com/karmada-io/karmada/pkg/generated/informers/externalversions"
	clusterlister "github.com/karmada-io/karmada/pkg/generated/listers/cluster/v1alpha1"
	"github.com/karmada-io/karmada/pkg/search/backendstore"
	"github.com/karmada-io/karmada/pkg/util"
	"github.com/karmada-io/karmada/pkg/util/fedinformer"
	"github.com/karmada-io/karmada/pkg/util/fedinformer/genericmanager"
	"github.com/karmada-io/karmada/pkg/util/gclient"
	"github.com/karmada-io/karmada/pkg/util/helper"
	"github.com/karmada-io/karmada/pkg/util/restmapper"
)

type registrySet map[string]struct{}

type clusterRegistry struct {
	registries registrySet
	resources  map[schema.GroupVersionResource]registrySet
}

func (c *clusterRegistry) unregistry() bool {
	return len(c.registries) == 0
}

// Controller ResourceRegistry controller
type Controller struct {
	restConfig      *rest.Config
	restMapper      meta.RESTMapper
	informerFactory informerfactory.SharedInformerFactory
	clusterLister   clusterlister.ClusterLister
	queue           workqueue.TypedRateLimitingInterface[any]

	clusterRegistry sync.Map

	InformerManager genericmanager.MultiClusterInformerManager
}

// NewController returns a new ResourceRegistry controller
func NewController(restConfig *rest.Config, factory informerfactory.SharedInformerFactory, restMapper meta.RESTMapper) (*Controller, error) {
	clusterLister := factory.Cluster().V1alpha1().Clusters().Lister()
	queue := workqueue.NewTypedRateLimitingQueue[any](workqueue.DefaultTypedControllerRateLimiter[any]())

	c := &Controller{
		restConfig:      restConfig,
		informerFactory: factory,
		clusterLister:   clusterLister,
		queue:           queue,
		restMapper:      restMapper,

		InformerManager: genericmanager.GetInstance(),
	}
	c.addAllEventHandlers()

	// TODO: leader election and full sync
	cs, err := kubernetes.NewForConfig(restConfig)
	if err != nil {
		return nil, err
	}
	backendstore.Init(cs)
	return c, nil
}

// addAllEventHandlers adds all event handlers to the informer
func (c *Controller) addAllEventHandlers() {
	clusterInformer := c.informerFactory.Cluster().V1alpha1().Clusters().Informer()
	_, err := clusterInformer.AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc:    c.addCluster,
		UpdateFunc: c.updateCluster,
		DeleteFunc: c.deleteCluster,
	})
	if err != nil {
		klog.Errorf("Failed to add handlers for Clusters: %v", err)
	}

	resourceRegistryInformer := c.informerFactory.Search().V1alpha1().ResourceRegistries().Informer()
	_, err = resourceRegistryInformer.AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc:    c.addResourceRegistry,
		UpdateFunc: c.updateResourceRegistry,
		DeleteFunc: c.deleteResourceRegistry,
	})
	if err != nil {
		klog.Errorf("Failed to add handlers for Clusters: %v", err)
	}

	// ignore the error here because the informers haven't been started
	_ = clusterInformer.SetTransform(fedinformer.StripUnusedFields)
	_ = resourceRegistryInformer.SetTransform(fedinformer.StripUnusedFields)
}

// Start the controller
func (c *Controller) Start(stopCh <-chan struct{}) {
	klog.Infof("Starting karmada search controller")

	defer runtime.HandleCrash()

	c.informerFactory.WaitForCacheSync(stopCh)

	go wait.Until(c.worker, time.Second, stopCh)

	go func() {
		<-stopCh
		genericmanager.StopInstance()
		klog.Infof("Shutting down karmada search controller")
	}()
}

// worker processes the queue of resourceRegistry objects.
func (c *Controller) worker() {
	for c.cacheNext() {
	}
}

// cacheNext processes the next cluster object in the queue.
func (c *Controller) cacheNext() bool {
	// Wait until there is a new item in the working queue
	key, shutdown := c.queue.Get()
	if shutdown {
		klog.Errorf("Fail to pop item from queue")
		return false
	}

	// Tell the queue that we are done with processing this key. This unblocks the key for other workers
	// This allows safe parallel processing because two pods with the same key are never processed in
	// parallel.
	defer c.queue.Done(key)

	err := c.doCacheCluster(key.(string))
	// Handle the error if something went wrong during the execution of the business logic
	c.handleErr(err, key)
	return true
}

// handleErr checks if an error happened and makes sure we will retry later.
func (c *Controller) handleErr(err error, key interface{}) {
	if err == nil {
		c.queue.Forget(key)
		return
	}

	klog.Errorf("Error cache member cluster %v, %v", key, err)
	c.queue.AddRateLimited(key)
}

func (c *Controller) getClusterMatchedRegistries(cluster *clusterv1alpha1.Cluster) (indexedByName, matched map[string]*searchv1alpha1.ResourceRegistry, err error) {
	client := c.informerFactory.Search().V1alpha1().ResourceRegistries().Lister()
	var registries []*searchv1alpha1.ResourceRegistry
	if registries, err = client.List(labels.Everything()); err != nil {
		klog.Errorf("List resource registries for reconciling cluster failed, err: %s", err)
		return
	}
	if len(registries) == 0 {
		klog.Infof("No resource registries, no need to reconcile cluster")
		return
	}
	indexedByName = make(map[string]*searchv1alpha1.ResourceRegistry, len(registries))
	matched = make(map[string]*searchv1alpha1.ResourceRegistry, len(registries))
	for i, registry := range registries {
		indexedByName[registry.Name] = registries[i]
		if util.ClusterMatches(cluster, registry.Spec.TargetCluster) {
			matched[registry.Name] = registries[i]
		}
	}
	return
}

func (c *Controller) getRegistryAddedResources(registry *searchv1alpha1.ResourceRegistry, cr *clusterRegistry, added []schema.GroupVersionResource) []schema.GroupVersionResource {
	resourcesToWatch := c.getResources(registry.Spec.ResourceSelectors)
	for _, resource := range resourcesToWatch {
		if resourcesOnWatching, exist := cr.resources[resource]; exist {
			resourcesOnWatching[registry.Name] = struct{}{}
		} else {
			added = append(added, resource)
			cr.resources[resource] = registrySet{registry.Name: struct{}{}}
		}
	}
	return added
}

func (c *Controller) getClusterRegistriesModification(registries map[string]*searchv1alpha1.ResourceRegistry, matched map[string]*searchv1alpha1.ResourceRegistry, cr *clusterRegistry, added []string, removed []string) (updated *clusterRegistry, addedResources []schema.GroupVersionResource, removedResources []schema.GroupVersionResource) {
	defer func() {
		updated = cr
	}()
	if cr == nil {
		cr = &clusterRegistry{
			resources:  make(map[schema.GroupVersionResource]registrySet),
			registries: make(registrySet)}
	}
	for _, name := range removed {
		delete(cr.registries, name)
		for resource, previousRegistries := range cr.resources {
			delete(previousRegistries, name)
			if len(previousRegistries) == 0 {
				removedResources = append(removedResources, resource)
			}
		}
		for _, resource := range removedResources {
			delete(cr.resources, resource)
		}
	}
	for _, name := range added {
		cr.registries[name] = struct{}{}
		addedResources = c.getRegistryAddedResources(registries[name], cr, addedResources)
	}
	for _, registry := range matched {
		addedResources = c.getRegistryAddedResources(registry, cr, addedResources)
	}
	return
}

func (c *Controller) findOpenSearchBackend(matchedRegistries map[string]*searchv1alpha1.ResourceRegistry) *searchv1alpha1.BackendStoreConfig {
	for _, registry := range matchedRegistries {
		if backend := registry.Spec.BackendStore; backend != nil && backend.OpenSearch != nil {
			// one cluster may be related to multi registries,
			// however only one backend could keep in memory with one cluster
			return backend
		}
	}
	return nil
}

func (c *Controller) clusterAbleToCache(cluster string) (cls *clusterv1alpha1.Cluster, able bool, err error) {
	cls, err = c.clusterLister.Get(cluster)
	if err != nil {
		if apierrors.IsNotFound(err) {
			klog.Infof("Try to stop cluster informer %s", cluster)
			c.InformerManager.Stop(cluster)
			return
		}
		return
	}

	if !cls.DeletionTimestamp.IsZero() {
		klog.Infof("Try to stop cluster informer %s", cluster)
		c.InformerManager.Stop(cluster)
		return
	}

	if !util.IsClusterReady(&cls.Status) {
		klog.Warningf("cluster %s is notReady try to stop this cluster informer", cluster)
		c.InformerManager.Stop(cluster)
		return
	}
	able = true
	return
}

func (c *Controller) reconcileClusterWithRegistries(cls *clusterv1alpha1.Cluster) (matchedRegistries map[string]*searchv1alpha1.ResourceRegistry, cr *clusterRegistry, resourcesChanged, newRegistry bool, err error) {
	cluster := cls.Name
	var allRegistries map[string]*searchv1alpha1.ResourceRegistry
	allRegistries, matchedRegistries, err = c.getClusterMatchedRegistries(cls)
	if err != nil {
		klog.Errorf("Get cluster matched resource registries failed, cluster: %s, error: %s", cluster, err)
		return
	}
	klog.V(4).Infof("Registries matched with cluster, cluster: %s, registries: %s",
		cluster, strings.Join(util.Keys(matchedRegistries), ", "))
	v, hasExistingRegistries := c.clusterRegistry.Load(cluster)
	var addedRegistries, removedRegistries []string
	if !hasExistingRegistries {
		klog.Infof("Cluster %s has no existing registries", cluster)
		addedRegistries, removedRegistries = util.DiffKey(registrySet(nil), matchedRegistries)
	} else {
		crv := v.(clusterRegistry)
		cr = &crv
		addedRegistries, removedRegistries = util.DiffKey(cr.registries, matchedRegistries)
	}
	if len(addedRegistries) > 0 {
		klog.V(4).Infof("New registries added to cluster, cluster: %s, registries: %s", cluster, strings.Join(addedRegistries, ", "))
	} else {
		klog.V(4).Infof("No registries added to cluster, cluster: %s", cluster)
	}
	if len(removedRegistries) > 0 {
		klog.V(4).Infof("Old registries removed from cluster, cluster: %s, registries: %s", cluster, strings.Join(removedRegistries, ", "))
	} else {
		klog.V(4).Infof("No registries removed from cluster, cluster: %s", cluster)
	}
	var addedResources, removedResources []schema.GroupVersionResource
	cr, addedResources, removedResources = c.getClusterRegistriesModification(allRegistries, matchedRegistries, cr, addedRegistries, removedRegistries)
	currentWatchingResources := util.Keys(cr.resources)
	resourcesString := util.StringerJoin(currentWatchingResources, ", ")
	if len(addedResources) > 0 {
		klog.V(4).Infof("New watching resources added to cluster, cluster: %s, resources: %s", cluster, util.StringerJoin(addedResources, ", "))
	} else {
		klog.V(4).Infof("No watching resources added to cluster, cluster: %s, resources: %s", cluster, resourcesString)
	}
	if len(removedResources) > 0 {
		klog.V(4).Infof("Resources watching removed from cluster, cluster: %s, resources: %s", cluster, util.StringerJoin(removedResources, ", "))
	} else {
		klog.V(4).Infof("No resources watching removed from cluster, cluster: %s, resources: %s", cluster, resourcesString)
	}
	resourcesChanged = len(addedResources) > 0 || len(removedResources) > 0
	newRegistry = !hasExistingRegistries
	return
}

func (c *Controller) getRegistryBackendHandler(cluster string, matchedRegistries map[string]*searchv1alpha1.ResourceRegistry) (cache.ResourceEventHandler, error) {
	backend := backendstore.GetBackend(cluster)
	if backend == nil {
		backendConfig := c.findOpenSearchBackend(matchedRegistries)
		backendstore.AddBackend(cluster, backendConfig)
		backend = backendstore.GetBackend(cluster)
	}
	if backend == nil {
		return nil, fmt.Errorf("failed to get backend store for cluster %s", cluster)
	}
	handler := backend.ResourceEventHandlerFuncs()
	if handler == nil {
		return nil, fmt.Errorf("failed to get resource event handler for cluster %s", cluster)
	}
	return handler, nil
}

var controlPlaneClientBuilder = func(restConfig *rest.Config) client.Client {
	return gclient.NewForConfigOrDie(restConfig)
}
var clusterDynamicClientBuilder = func(cluster string, controlPlaneClient client.Client) (*util.DynamicClusterClient, error) {
	return util.NewClusterDynamicClientSet(cluster, controlPlaneClient)
}

// doCacheCluster processes the resourceRegistry object
// TODO: update status
func (c *Controller) doCacheCluster(cluster string) error {
	// STEP0: stop informer manager for the cluster which does not exist anymore or is not ready.
	cls, able, err := c.clusterAbleToCache(cluster)
	if err != nil || !able {
		return err
	}
	matchedRegistries, cr, resourcesChanged, newRegistry, err := c.reconcileClusterWithRegistries(cls)
	if err != nil {
		return err
	}

	// STEP1:  stop informer manager for the cluster which is not referenced by any `SearchRegistry` object.
	if cr.unregistry() {
		klog.Infof("Try to stop cluster informer %s", cluster)
		c.InformerManager.Stop(cluster)
		return nil
	}

	if resourcesChanged {
		klog.Infof("Create new informer for cluster %s", cluster)
		c.InformerManager.Stop(cluster)
	}

	if newRegistry {
		c.clusterRegistry.Store(cluster, *cr)
	}
	handler, err := c.getRegistryBackendHandler(cluster, matchedRegistries)
	if err != nil {
		return err
	}

	var newInformerCreated bool
	// STEP2: added/updated cluster, builds an informer manager for a specific cluster.
	if !c.InformerManager.IsManagerExist(cluster) {
		klog.Info("Try to build informer manager for cluster ", cluster)
		controlPlaneClient := controlPlaneClientBuilder(c.restConfig)

		clusterDynamicClient, err := clusterDynamicClientBuilder(cluster, controlPlaneClient)
		if err != nil {
			return err
		}
		_ = c.InformerManager.ForCluster(cluster, clusterDynamicClient.DynamicClientSet, 0)
		newInformerCreated = true
	}

	if !newInformerCreated && !resourcesChanged {
		return nil
	}

	sci := c.InformerManager.GetSingleClusterManager(cluster)
	for gvr := range cr.resources {
		gvk, err := c.restMapper.KindFor(gvr)
		if err != nil {
			klog.Errorf("Failed to get gvk: %v", err)
			continue
		}
		if !helper.IsAPIEnabled(cls.Status.APIEnablements, gvk.GroupVersion().String(), gvk.Kind) {
			klog.Warningf("Resource %s is not enabled for cluster %s", gvr.String(), cluster)
			continue
		}
		klog.Infof("Add informer for %s, %v", cluster, gvr)
		sci.ForResource(gvr, handler)
	}
	klog.Infof("Start informer for %s", cluster)
	sci.Start()
	_ = sci.WaitForCacheSync()
	klog.Infof("Start informer for %s done", cluster)

	return nil
}

// addResourceRegistry parse the resourceRegistry object and add Cluster to the queue
func (c *Controller) addResourceRegistry(obj interface{}) {
	rr := obj.(*searchv1alpha1.ResourceRegistry)

	for _, cluster := range c.getClusters(rr.Spec.TargetCluster) {
		c.queue.Add(cluster)
	}
}

// updateResourceRegistry parse the resourceRegistry object and add (added/deleted) Cluster to the queue
func (c *Controller) updateResourceRegistry(oldObj, newObj interface{}) {
	oldRR := oldObj.(*searchv1alpha1.ResourceRegistry)
	newRR := newObj.(*searchv1alpha1.ResourceRegistry)

	if reflect.DeepEqual(oldRR.Spec, newRR.Spec) {
		klog.V(4).Infof("Ignore ResourceRegistry(%s) update event as spec not changed", newRR.Name)
		return
	}
	clusterSet := sets.New[string]()
	for _, registry := range []*searchv1alpha1.ResourceRegistry{newRR, oldRR} {
		clusters := c.getClusters(registry.Spec.TargetCluster)
		clusterSet.Insert(clusters...)
	}
	for _, cluster := range clusterSet.UnsortedList() {
		c.queue.Add(cluster)
	}
}

// deleteResourceRegistry parse the resourceRegistry object and add deleted Cluster to the queue
func (c *Controller) deleteResourceRegistry(obj interface{}) {
	rr, isRR := obj.(*searchv1alpha1.ResourceRegistry)
	// We can get DeletedFinalStateUnknown instead of *searchv1alpha1.ResourceRegistry here and
	// we need to handle that correctly.
	if !isRR {
		deletedState, ok := obj.(cache.DeletedFinalStateUnknown)
		if !ok {
			klog.ErrorS(nil, "Received unpexpected object", "object", obj)
			return
		}
		rr, ok = deletedState.Obj.(*searchv1alpha1.ResourceRegistry)
		if !ok {
			klog.ErrorS(nil, "DeletedFinalStateUnknown contained non-ResourceRegistry object", "object", deletedState.Obj)
			return
		}
	}

	for _, cluster := range c.getClusters(rr.Spec.TargetCluster) {
		c.queue.Add(cluster)
	}
}

// addCluster adds a cluster object to the queue if needed
func (c *Controller) addCluster(obj interface{}) {
	cluster := obj.(*clusterv1alpha1.Cluster)

	c.queue.Add(cluster.GetName())
}

// updateCluster rebuild informer if Cluster.Spec is changed
func (c *Controller) updateCluster(oldObj, curObj interface{}) {
	curCluster := curObj.(*clusterv1alpha1.Cluster)

	oldCluster := oldObj.(*clusterv1alpha1.Cluster)
	if curCluster.ResourceVersion == oldCluster.ResourceVersion {
		// no change, do nothing.
		return
	}

	if curCluster.DeletionTimestamp != nil {
		// cluster is being deleted.
		c.queue.Add(curCluster.GetName())
	}

	if !reflect.DeepEqual(curCluster.Spec, oldCluster.Spec) || !reflect.DeepEqual(curCluster.Labels, oldCluster.Labels) ||
		!reflect.DeepEqual(curCluster.Status.APIEnablements, oldCluster.Status.APIEnablements) {
		c.queue.Add(curCluster.GetName())
	}
}

// deleteCluster set cluster to not exists
func (c *Controller) deleteCluster(obj interface{}) {
	cluster, isCluster := obj.(*clusterv1alpha1.Cluster)
	// We can get DeletedFinalStateUnknown instead of *clusterV1alpha1.Cluster here and
	// we need to handle that correctly.
	if !isCluster {
		deletedState, ok := obj.(cache.DeletedFinalStateUnknown)
		if !ok {
			klog.ErrorS(nil, "Received unexpected object", "object", obj)
			return
		}
		cluster, ok = deletedState.Obj.(*clusterv1alpha1.Cluster)
		if !ok {
			klog.ErrorS(nil, "DeletedFinalStateUnknown contained non-Cluster object", "object", deletedState.Obj)
			return
		}
	}

	_, ok := c.clusterRegistry.Load(cluster.GetName())
	if !ok {
		// unregistered cluster, do nothing.
		return
	}

	// remove backend store
	backendstore.DeleteBackend(cluster.GetName())

	c.queue.Add(cluster.GetName())
}

// getClusters returns the cluster from the resourceRegistry object
func (c *Controller) getClusters(affinity policyv1alpha1.ClusterAffinity) []string {
	clusters := make([]string, 0)
	lst, err := c.clusterLister.List(labels.Everything())
	if err != nil {
		klog.Errorf("Failed to list clusters: %v", err)
		return clusters
	}
	for _, cls := range lst {
		if util.ClusterMatches(cls, affinity) {
			clusters = append(clusters, cls.GetName())
		}
	}
	return clusters
}

// getResources returns the resources from the resourceRegistry object
func (c *Controller) getResources(selectors []searchv1alpha1.ResourceSelector) []schema.GroupVersionResource {
	resources := make([]schema.GroupVersionResource, 0)
	for _, rs := range selectors {
		gvr, err := restmapper.GetGroupVersionResource(
			c.restMapper, schema.FromAPIVersionAndKind(rs.APIVersion, rs.Kind),
		)
		if err != nil {
			klog.Errorf("Failed to get gvr: %v", err)
			continue
		}
		resources = append(resources, gvr)
	}
	return resources
}