// Copyright Istio 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 controller

import (
	"github.com/hashicorp/go-multierror"
	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/labels"
	listerv1 "k8s.io/client-go/listers/core/v1"
	"k8s.io/client-go/tools/cache"
)

import (
	"github.com/apache/dubbo-go-pixiu/pilot/pkg/model"
	"github.com/apache/dubbo-go-pixiu/pilot/pkg/serviceregistry/kube/controller/filter"
	"github.com/apache/dubbo-go-pixiu/pkg/config/mesh"
	kubelib "github.com/apache/dubbo-go-pixiu/pkg/kube"
)

// initialize handlers for discovery selection scoping
func (c *Controller) initDiscoveryHandlers(
	kubeClient kubelib.Client,
	endpointMode EndpointMode,
	meshWatcher mesh.Watcher,
	discoveryNamespacesFilter filter.DiscoveryNamespacesFilter,
) {
	c.initDiscoveryNamespaceHandlers(kubeClient, endpointMode, discoveryNamespacesFilter)
	c.initMeshWatcherHandler(kubeClient, endpointMode, meshWatcher, discoveryNamespacesFilter)
}

// handle discovery namespace membership changes triggered by namespace events,
// which requires triggering create/delete event handlers for services, pods, and endpoints,
// and updating the DiscoveryNamespacesFilter.
func (c *Controller) initDiscoveryNamespaceHandlers(
	kubeClient kubelib.Client,
	endpointMode EndpointMode,
	discoveryNamespacesFilter filter.DiscoveryNamespacesFilter,
) {
	otype := "Namespaces"
	c.nsInformer.AddEventHandler(cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			incrementEvent(otype, "add")
			ns := obj.(*v1.Namespace)
			if discoveryNamespacesFilter.NamespaceCreated(ns.ObjectMeta) {
				c.queue.Push(func() error {
					c.handleSelectedNamespace(endpointMode, ns.Name)
					return nil
				})
			}
		},
		UpdateFunc: func(old, new interface{}) {
			incrementEvent(otype, "update")
			oldNs := old.(*v1.Namespace)
			newNs := new.(*v1.Namespace)
			membershipChanged, namespaceAdded := discoveryNamespacesFilter.NamespaceUpdated(oldNs.ObjectMeta, newNs.ObjectMeta)
			if membershipChanged {
				var handleFunc func() error
				if namespaceAdded {
					handleFunc = func() error {
						c.handleSelectedNamespace(endpointMode, newNs.Name)
						return nil
					}
				} else {
					handleFunc = func() error {
						c.handleDeselectedNamespace(kubeClient, endpointMode, newNs.Name)
						return nil
					}
				}
				c.queue.Push(handleFunc)
			}
		},
		DeleteFunc: func(obj interface{}) {
			incrementEvent(otype, "delete")
			ns, ok := obj.(*v1.Namespace)
			if !ok {
				if tombstone, ok := obj.(cache.DeletedFinalStateUnknown); ok {
					if cast, ok := tombstone.Obj.(*v1.Namespace); ok {
						ns = cast
					} else {
						log.Errorf("Failed to convert to tombstoned namespace object: %v", obj)
						return
					}
				} else {
					log.Errorf("Failed to convert to namespace object: %v", obj)
					return
				}
			}
			discoveryNamespacesFilter.NamespaceDeleted(ns.ObjectMeta)
			// no need to invoke object handlers since objects within the namespace will trigger delete events
		},
	})
}

// handle discovery namespace membership changes triggered by changes to meshConfig's discovery selectors
// which requires updating the DiscoveryNamespaceFilter and triggering create/delete event handlers for services/pods/endpoints
// for membership changes
func (c *Controller) initMeshWatcherHandler(
	kubeClient kubelib.Client,
	endpointMode EndpointMode,
	meshWatcher mesh.Watcher,
	discoveryNamespacesFilter filter.DiscoveryNamespacesFilter,
) {
	meshWatcher.AddMeshHandler(func() {
		newSelectedNamespaces, deselectedNamespaces := discoveryNamespacesFilter.SelectorsChanged(meshWatcher.Mesh().GetDiscoverySelectors())

		for _, nsName := range newSelectedNamespaces {
			nsName := nsName // need to shadow variable to ensure correct value when evaluated inside the closure below
			c.queue.Push(func() error {
				c.handleSelectedNamespace(endpointMode, nsName)
				return nil
			})
		}

		for _, nsName := range deselectedNamespaces {
			nsName := nsName // need to shadow variable to ensure correct value when evaluated inside the closure below
			c.queue.Push(func() error {
				c.handleDeselectedNamespace(kubeClient, endpointMode, nsName)
				return nil
			})
		}
	})
}

// issue create events for all services, pods, and endpoints in the newly labeled namespace
func (c *Controller) handleSelectedNamespace(endpointMode EndpointMode, ns string) {
	var errs *multierror.Error

	// for each resource type, issue create events for objects in the labeled namespace

	services, err := c.serviceLister.Services(ns).List(labels.Everything())
	if err != nil {
		log.Errorf("error listing services: %v", err)
		return
	}
	for _, svc := range services {
		errs = multierror.Append(errs, c.onServiceEvent(svc, model.EventAdd))
	}

	pods, err := listerv1.NewPodLister(c.pods.informer.GetIndexer()).Pods(ns).List(labels.Everything())
	if err != nil {
		log.Errorf("error listing pods: %v", err)
		return
	}
	for _, pod := range pods {
		errs = multierror.Append(errs, c.pods.onEvent(pod, model.EventAdd))
	}

	switch endpointMode {
	case EndpointsOnly:
		endpoints, err := listerv1.NewEndpointsLister(c.endpoints.getInformer().GetIndexer()).Endpoints(ns).List(labels.Everything())
		if err != nil {
			log.Errorf("error listing endpoints: %v", err)
			return
		}
		for _, ep := range endpoints {
			errs = multierror.Append(errs, c.endpoints.onEvent(ep, model.EventAdd))
		}
	case EndpointSliceOnly:
		endpointSlices, err := c.endpoints.(*endpointSliceController).listSlices(ns, labels.Everything())
		if err != nil {
			log.Errorf("error listing endpoint slices: %v", err)
			return
		}
		for _, ep := range endpointSlices {
			errs = multierror.Append(errs, c.endpoints.onEvent(ep, model.EventAdd))
		}
	}

	if err := multierror.Flatten(errs.ErrorOrNil()); err != nil {
		log.Errorf("one or more errors while handling newly labeled discovery namespace %s: %v", ns, err)
	}
}

// issue delete events for all services, pods, and endpoints in the delabled namespace
// use kubeClient.KubeInformer() to bypass filter in order to list resources from non-labeled namespace,
// which fetches informers from the SharedInformerFactory cache (i.e. does not instantiate a new informer)
func (c *Controller) handleDeselectedNamespace(kubeClient kubelib.Client, endpointMode EndpointMode, ns string) {
	var errs *multierror.Error

	// for each resource type, issue delete events for objects in the delabled namespace

	services, err := kubeClient.KubeInformer().Core().V1().Services().Lister().Services(ns).List(labels.Everything())
	if err != nil {
		log.Errorf("error listing services: %v", err)
		return
	}
	for _, svc := range services {
		errs = multierror.Append(errs, c.onServiceEvent(svc, model.EventDelete))
	}

	pods, err := kubeClient.KubeInformer().Core().V1().Pods().Lister().Pods(ns).List(labels.Everything())
	if err != nil {
		log.Errorf("error listing pods: %v", err)
		return
	}
	for _, pod := range pods {
		errs = multierror.Append(errs, c.pods.onEvent(pod, model.EventDelete))
	}

	switch endpointMode {
	case EndpointsOnly:
		endpoints, err := kubeClient.KubeInformer().Core().V1().Endpoints().Lister().Endpoints(ns).List(labels.Everything())
		if err != nil {
			log.Errorf("error listing endpoints: %v", err)
			return
		}
		for _, ep := range endpoints {
			errs = multierror.Append(errs, c.endpoints.onEvent(ep, model.EventDelete))
		}
	case EndpointSliceOnly:
		endpointSlices, err := c.endpoints.(*endpointSliceController).listSlices(ns, labels.Everything())
		if err != nil {
			log.Errorf("error listing endpoint slices: %v", err)
			return
		}
		for _, ep := range endpointSlices {
			errs = multierror.Append(errs, c.endpoints.onEvent(ep, model.EventDelete))
		}
	}

	if err := multierror.Flatten(errs.ErrorOrNil()); err != nil {
		log.Errorf("one or more errors while handling delabeled discovery namespace %s: %v", ns, err)
	}
}