/*
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.
*/

// This code is mostly lifted from the Kubernetes codebase to establish the internal cache.
// https://github.com/kubernetes/kubernetes/blob/release-1.25/pkg/scheduler/eventhandlers.go

package server

import (
	"fmt"

	corev1 "k8s.io/api/core/v1"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/client-go/informers"
	"k8s.io/client-go/tools/cache"
	"k8s.io/klog/v2"
)

func addAllEventHandlers(es *AccurateSchedulerEstimatorServer, informerFactory informers.SharedInformerFactory) {
	// scheduled pod cache
	_, err := informerFactory.Core().V1().Pods().Informer().AddEventHandler(
		cache.FilteringResourceEventHandler{
			FilterFunc: func(obj interface{}) bool {
				switch t := obj.(type) {
				case *corev1.Pod:
					return assignedPod(t)
				case cache.DeletedFinalStateUnknown:
					if _, ok := t.Obj.(*corev1.Pod); ok {
						// The carried object may be stale, so we don't use it to check if
						// it's assigned or not. Attempting to cleanup anyways.
						return true
					}
					utilruntime.HandleError(fmt.Errorf("unable to convert object %T to *v1.Pod", obj))
					return false
				default:
					utilruntime.HandleError(fmt.Errorf("unable to handle object: %T", obj))
					return false
				}
			},
			Handler: cache.ResourceEventHandlerFuncs{
				AddFunc:    es.addPodToCache,
				UpdateFunc: es.updatePodInCache,
				DeleteFunc: es.deletePodFromCache,
			},
		},
	)
	if err != nil {
		klog.Errorf("Failed to add handler for Pods: %v", err)
	}

	_, err = informerFactory.Core().V1().Nodes().Informer().AddEventHandler(
		cache.ResourceEventHandlerFuncs{
			AddFunc:    es.addNodeToCache,
			UpdateFunc: es.updateNodeInCache,
			DeleteFunc: es.deleteNodeFromCache,
		},
	)
	if err != nil {
		klog.Errorf("Failed to add handler for Pods: %v", err)
	}
}

func (es *AccurateSchedulerEstimatorServer) addPodToCache(obj interface{}) {
	pod, ok := obj.(*corev1.Pod)
	if !ok {
		klog.ErrorS(nil, "Cannot convert to *v1.Pod", "obj", obj)
		return
	}
	klog.V(3).InfoS("Add event for scheduled pod", "pod", klog.KObj(pod))

	if err := es.Cache.AddPod(pod); err != nil {
		klog.ErrorS(err, "Estimator cache AddPod failed", "pod", klog.KObj(pod))
	}
}

func (es *AccurateSchedulerEstimatorServer) updatePodInCache(oldObj, newObj interface{}) {
	oldPod, ok := oldObj.(*corev1.Pod)
	if !ok {
		klog.ErrorS(nil, "Cannot convert oldObj to *v1.Pod", "oldObj", oldObj)
		return
	}
	newPod, ok := newObj.(*corev1.Pod)
	if !ok {
		klog.ErrorS(nil, "Cannot convert newObj to *v1.Pod", "newObj", newObj)
		return
	}
	klog.V(4).InfoS("Update event for scheduled pod", "pod", klog.KObj(oldPod))

	if err := es.Cache.UpdatePod(oldPod, newPod); err != nil {
		klog.ErrorS(err, "Estimator cache UpdatePod failed", "pod", klog.KObj(oldPod))
	}
}

func (es *AccurateSchedulerEstimatorServer) deletePodFromCache(obj interface{}) {
	var pod *corev1.Pod
	switch t := obj.(type) {
	case *corev1.Pod:
		pod = t
	case cache.DeletedFinalStateUnknown:
		var ok bool
		pod, ok = t.Obj.(*corev1.Pod)
		if !ok {
			klog.ErrorS(nil, "Cannot convert to *v1.Pod", "obj", t.Obj)
			return
		}
	default:
		klog.ErrorS(nil, "Cannot convert to *v1.Pod", "obj", t)
		return
	}
	klog.V(3).InfoS("Delete event for scheduled pod", "pod", klog.KObj(pod))
	if err := es.Cache.RemovePod(pod); err != nil {
		klog.ErrorS(err, "Estimator cache RemovePod failed", "pod", klog.KObj(pod))
	}
}

func (es *AccurateSchedulerEstimatorServer) addNodeToCache(obj interface{}) {
	node, ok := obj.(*corev1.Node)
	if !ok {
		klog.ErrorS(nil, "Cannot convert to *v1.Node", "obj", obj)
		return
	}

	es.Cache.AddNode(node)
	klog.V(3).InfoS("Add event for node", "node", klog.KObj(node))
}

func (es *AccurateSchedulerEstimatorServer) updateNodeInCache(oldObj, newObj interface{}) {
	oldNode, ok := oldObj.(*corev1.Node)
	if !ok {
		klog.ErrorS(nil, "Cannot convert oldObj to *v1.Node", "oldObj", oldObj)
		return
	}
	newNode, ok := newObj.(*corev1.Node)
	if !ok {
		klog.ErrorS(nil, "Cannot convert newObj to *v1.Node", "newObj", newObj)
		return
	}

	es.Cache.UpdateNode(oldNode, newNode)
}

func (es *AccurateSchedulerEstimatorServer) deleteNodeFromCache(obj interface{}) {
	var node *corev1.Node
	switch t := obj.(type) {
	case *corev1.Node:
		node = t
	case cache.DeletedFinalStateUnknown:
		var ok bool
		node, ok = t.Obj.(*corev1.Node)
		if !ok {
			klog.ErrorS(nil, "Cannot convert to *v1.Node", "obj", t.Obj)
			return
		}
	default:
		klog.ErrorS(nil, "Cannot convert to *v1.Node", "obj", t)
		return
	}
	klog.V(3).InfoS("Delete event for node", "node", klog.KObj(node))
	if err := es.Cache.RemoveNode(node); err != nil {
		klog.ErrorS(err, "Scheduler cache RemoveNode failed")
	}
}

// assignedPod selects pods that are assigned (scheduled and running).
func assignedPod(pod *corev1.Pod) bool {
	return len(pod.Spec.NodeName) != 0
}