package objectwatcher

import (
	"context"
	"fmt"
	"reflect"
	"strings"
	"sync"

	apierrors "k8s.io/apimachinery/pkg/api/errors"
	"k8s.io/apimachinery/pkg/api/meta"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/client-go/kubernetes"
	"k8s.io/klog/v2"
	"sigs.k8s.io/controller-runtime/pkg/client"

	"github.com/karmada-io/karmada/pkg/util"
	"github.com/karmada-io/karmada/pkg/util/restmapper"
)

const (
	generationPrefix      = "gen:"
	resourceVersionPrefix = "rv:"
)

// ObjectWatcher manages operations for object dispatched to member clusters.
type ObjectWatcher interface {
	Create(clusterName string, desireObj *unstructured.Unstructured) error
	Update(clusterName string, desireObj, clusterObj *unstructured.Unstructured) error
	Delete(clusterName string, desireObj *unstructured.Unstructured) error
	NeedsUpdate(clusterName string, desiredObj, clusterObj *unstructured.Unstructured) (bool, error)
}

type objectWatcherImpl struct {
	client.Client
	KubeClientSet kubernetes.Interface
	VersionRecord map[string]map[string]string
	RESTMapper    meta.RESTMapper
	Lock          sync.RWMutex
}

// NewObjectWatcher returns a instance of ObjectWatcher
func NewObjectWatcher(client client.Client, kubeClientSet kubernetes.Interface, restMapper meta.RESTMapper) ObjectWatcher {
	return &objectWatcherImpl{
		Client:        client,
		KubeClientSet: kubeClientSet,
		VersionRecord: make(map[string]map[string]string),
		RESTMapper:    restMapper,
	}
}

func (o *objectWatcherImpl) Create(clusterName string, desireObj *unstructured.Unstructured) error {
	klog.Infof("Start to create resource %v/%v", desireObj.GetNamespace(), desireObj.GetName())
	dynamicClusterClient, err := util.BuildDynamicClusterClient(o.Client, o.KubeClientSet, clusterName)
	if err != nil {
		klog.Errorf("Failed to build dynamic cluster client for cluster %s.", clusterName)
		return err
	}

	gvr, err := restmapper.GetGroupVersionResource(o.RESTMapper, desireObj.GroupVersionKind())
	if err != nil {
		klog.Errorf("Failed to create resource(%s/%s) as mapping GVK to GVR failed: %v", desireObj.GetNamespace(), desireObj.GetName(), err)
		return err
	}

	clusterObj, err := dynamicClusterClient.DynamicClientSet.Resource(gvr).Namespace(desireObj.GetNamespace()).Create(context.TODO(), desireObj, v1.CreateOptions{})
	if err != nil {
		if apierrors.IsAlreadyExists(err) {
			return nil
		}
		klog.Errorf("Failed to create resource %v, err is %v ", desireObj.GetName(), err)
		return err
	}

	// record version
	o.recordVersion(clusterObj, dynamicClusterClient.ClusterName)
	return nil
}

func (o *objectWatcherImpl) Update(clusterName string, desireObj, clusterObj *unstructured.Unstructured) error {
	klog.Infof("Start to update resource %v/%v", desireObj.GetNamespace(), desireObj.GetName())
	dynamicClusterClient, err := util.BuildDynamicClusterClient(o.Client, o.KubeClientSet, clusterName)
	if err != nil {
		klog.Errorf("Failed to build dynamic cluster client for cluster %s.", clusterName)
		return err
	}

	gvr, err := restmapper.GetGroupVersionResource(o.RESTMapper, desireObj.GroupVersionKind())
	if err != nil {
		klog.Errorf("Failed to update resource(%s/%s) as mapping GVK to GVR failed: %v", desireObj.GetNamespace(), desireObj.GetName(), err)
		return err
	}

	err = RetainClusterFields(desireObj, clusterObj)
	if err != nil {
		klog.Errorf("Failed to retain fields: %v", err)
		return err
	}

	resource, err := dynamicClusterClient.DynamicClientSet.Resource(gvr).Namespace(desireObj.GetNamespace()).Update(context.TODO(), desireObj, v1.UpdateOptions{})
	if err != nil {
		klog.Errorf("Failed to update resource %v/%v, err is %v ", desireObj.GetNamespace(), desireObj.GetName(), err)
		return err
	}

	// record version
	o.recordVersion(resource, clusterName)
	return nil
}

func (o *objectWatcherImpl) Delete(clusterName string, desireObj *unstructured.Unstructured) error {
	klog.Infof("Start to delete resource %v/%v", desireObj.GetNamespace(), desireObj.GetName())
	dynamicClusterClient, err := util.BuildDynamicClusterClient(o.Client, o.KubeClientSet, clusterName)
	if err != nil {
		klog.Errorf("Failed to build dynamic cluster client for cluster %s.", clusterName)
		return err
	}

	gvr, err := restmapper.GetGroupVersionResource(o.RESTMapper, desireObj.GroupVersionKind())
	if err != nil {
		klog.Errorf("Failed to delete resource(%s/%s) as mapping GVK to GVR failed: %v", desireObj.GetNamespace(), desireObj.GetName(), err)
		return err
	}

	err = dynamicClusterClient.DynamicClientSet.Resource(gvr).Namespace(desireObj.GetNamespace()).Delete(context.TODO(), desireObj.GetName(), v1.DeleteOptions{})
	if apierrors.IsNotFound(err) {
		err = nil
	}
	if err != nil {
		klog.Errorf("Failed to delete resource %v, err is %v ", desireObj.GetName(), err)
		return err
	}

	objectKey := o.genObjectKey(desireObj)
	o.deleteVersionRecord(dynamicClusterClient.ClusterName, objectKey)

	return nil
}

func (o *objectWatcherImpl) genObjectKey(obj *unstructured.Unstructured) string {
	return obj.GroupVersionKind().String() + "/" + obj.GetNamespace() + "/" + obj.GetName()
}

// recordVersion will add or update resource version records
func (o *objectWatcherImpl) recordVersion(clusterObj *unstructured.Unstructured, clusterName string) {
	objVersion := objectVersion(clusterObj)
	objectKey := o.genObjectKey(clusterObj)
	if o.isClusterVersionRecordExist(clusterName) {
		o.updateVersionRecord(clusterName, objectKey, objVersion)
	} else {
		o.addVersionRecord(clusterName, objectKey, objVersion)
	}
}

// isClusterVersionRecordExist checks if the version record map of given member cluster exist
func (o *objectWatcherImpl) isClusterVersionRecordExist(clusterName string) bool {
	o.Lock.RLock()
	defer o.Lock.RUnlock()

	_, exist := o.VersionRecord[clusterName]

	return exist
}

// getVersionRecord will return the recorded version of given resource(if exist)
func (o *objectWatcherImpl) getVersionRecord(clusterName, resourceName string) (string, bool) {
	o.Lock.RLock()
	defer o.Lock.RUnlock()

	version, exist := o.VersionRecord[clusterName][resourceName]
	return version, exist
}

// addVersionRecord will add new version record of given resource
func (o *objectWatcherImpl) addVersionRecord(clusterName, resourceName, version string) {
	o.Lock.Lock()
	defer o.Lock.Unlock()
	o.VersionRecord[clusterName] = map[string]string{resourceName: version}
}

// updateVersionRecord will update the recorded version of given resource
func (o *objectWatcherImpl) updateVersionRecord(clusterName, resourceName, version string) {
	o.Lock.Lock()
	defer o.Lock.Unlock()
	o.VersionRecord[clusterName][resourceName] = version
}

// deleteVersionRecord will delete the recorded version of given resource
func (o *objectWatcherImpl) deleteVersionRecord(clusterName, resourceName string) {
	o.Lock.Lock()
	defer o.Lock.Unlock()
	delete(o.VersionRecord[clusterName], resourceName)
}

func (o *objectWatcherImpl) NeedsUpdate(clusterName string, desiredObj, clusterObj *unstructured.Unstructured) (bool, error) {
	// get resource version
	version, exist := o.getVersionRecord(clusterName, desiredObj.GroupVersionKind().String()+"/"+desiredObj.GetNamespace()+"/"+desiredObj.GetName())
	if !exist {
		klog.Errorf("Failed to update resource %v/%v for the version record does not exist", desiredObj.GetNamespace(), desiredObj.GetName())
		return false, fmt.Errorf("failed to update resource %v/%v for the version record does not exist", desiredObj.GetNamespace(), desiredObj.GetName())
	}

	return objectNeedsUpdate(desiredObj, clusterObj, version), nil
}

/*
This code is lifted from the kubefed codebase. It's a list of functions to determines whether the provided cluster
object needs to be updated according to the desired object and the recorded version.
For reference: https://github.com/kubernetes-sigs/kubefed/blob/master/pkg/controller/util/propagatedversion.go#L30-L59
*/

// objectVersion retrieves the field type-prefixed value used for
// determining currency of the given cluster object.
func objectVersion(clusterObj *unstructured.Unstructured) string {
	generation := clusterObj.GetGeneration()
	if generation != 0 {
		return fmt.Sprintf("%s%d", generationPrefix, generation)
	}
	return fmt.Sprintf("%s%s", resourceVersionPrefix, clusterObj.GetResourceVersion())
}

// objectNeedsUpdate determines whether the 2 objects provided cluster
// object needs to be updated according to the desired object and the
// recorded version.
func objectNeedsUpdate(desiredObj, clusterObj *unstructured.Unstructured, recordedVersion string) bool {
	targetVersion := objectVersion(clusterObj)

	if recordedVersion != targetVersion {
		return true
	}

	// If versions match and the version is sourced from the
	// generation field, a further check of metadata equivalency is
	// required.
	return strings.HasPrefix(targetVersion, generationPrefix) && !objectMetaObjEquivalent(desiredObj, clusterObj)
}

// objectMetaObjEquivalent checks if cluster-independent, user provided data in two given ObjectMeta are equal. If in
// the future the ObjectMeta structure is expanded then any field that is not populated
// by the api server should be included here.
func objectMetaObjEquivalent(a, b metav1.Object) bool {
	if a.GetName() != b.GetName() {
		return false
	}
	if a.GetNamespace() != b.GetNamespace() {
		return false
	}
	aLabels := a.GetLabels()
	bLabels := b.GetLabels()
	if !reflect.DeepEqual(aLabels, bLabels) && (len(aLabels) != 0 || len(bLabels) != 0) {
		return false
	}
	return true
}