/*
Copyright 2015 The Kubernetes 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 podgc

import (
	"sort"
	"sync"
	"time"

	"k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	coreinformers "k8s.io/client-go/informers/core/v1"
	clientset "k8s.io/client-go/kubernetes"
	corelisters "k8s.io/client-go/listers/core/v1"
	"k8s.io/client-go/tools/cache"
	"k8s.io/kubernetes/pkg/util/metrics"

	"k8s.io/klog"
)

const (
	gcCheckPeriod = 20 * time.Second
)

type PodGCController struct {
	kubeClient clientset.Interface

	podLister       corelisters.PodLister
	podListerSynced cache.InformerSynced

	deletePod              func(namespace, name string) error
	terminatedPodThreshold int
}

func NewPodGC(kubeClient clientset.Interface, podInformer coreinformers.PodInformer, terminatedPodThreshold int) *PodGCController {
	if kubeClient != nil && kubeClient.CoreV1().RESTClient().GetRateLimiter() != nil {
		metrics.RegisterMetricAndTrackRateLimiterUsage("gc_controller", kubeClient.CoreV1().RESTClient().GetRateLimiter())
	}
	gcc := &PodGCController{
		kubeClient:             kubeClient,
		terminatedPodThreshold: terminatedPodThreshold,
		deletePod: func(namespace, name string) error {
			klog.Infof("PodGC is force deleting Pod: %v/%v", namespace, name)
			return kubeClient.CoreV1().Pods(namespace).Delete(name, metav1.NewDeleteOptions(0))
		},
	}

	gcc.podLister = podInformer.Lister()
	gcc.podListerSynced = podInformer.Informer().HasSynced

	return gcc
}

func (gcc *PodGCController) Run(stop <-chan struct{}) {
	defer utilruntime.HandleCrash()

	klog.Infof("Starting GC controller")
	defer klog.Infof("Shutting down GC controller")

	if !cache.WaitForNamedCacheSync("GC", stop, gcc.podListerSynced) {
		return
	}

	go wait.Until(gcc.gc, gcCheckPeriod, stop)

	<-stop
}

func (gcc *PodGCController) gc() {
	pods, err := gcc.podLister.List(labels.Everything())
	if err != nil {
		klog.Errorf("Error while listing all Pods: %v", err)
		return
	}
	if gcc.terminatedPodThreshold > 0 {
		gcc.gcTerminated(pods)
	}
	gcc.gcOrphaned(pods)
	gcc.gcUnscheduledTerminating(pods)
}

func isPodTerminated(pod *v1.Pod) bool {
	if phase := pod.Status.Phase; phase != v1.PodPending && phase != v1.PodRunning && phase != v1.PodUnknown {
		return true
	}
	return false
}

func (gcc *PodGCController) gcTerminated(pods []*v1.Pod) {
	terminatedPods := []*v1.Pod{}
	for _, pod := range pods {
		if isPodTerminated(pod) {
			terminatedPods = append(terminatedPods, pod)
		}
	}

	terminatedPodCount := len(terminatedPods)
	sort.Sort(byCreationTimestamp(terminatedPods))

	deleteCount := terminatedPodCount - gcc.terminatedPodThreshold

	if deleteCount > terminatedPodCount {
		deleteCount = terminatedPodCount
	}
	if deleteCount > 0 {
		klog.Infof("garbage collecting %v pods", deleteCount)
	}

	var wait sync.WaitGroup
	for i := 0; i < deleteCount; i++ {
		wait.Add(1)
		go func(namespace string, name string) {
			defer wait.Done()
			if err := gcc.deletePod(namespace, name); err != nil {
				// ignore not founds
				defer utilruntime.HandleError(err)
			}
		}(terminatedPods[i].Namespace, terminatedPods[i].Name)
	}
	wait.Wait()
}

// gcOrphaned deletes pods that are bound to nodes that don't exist.
func (gcc *PodGCController) gcOrphaned(pods []*v1.Pod) {
	klog.V(4).Infof("GC'ing orphaned")
	// We want to get list of Nodes from the etcd, to make sure that it's as fresh as possible.
	nodes, err := gcc.kubeClient.CoreV1().Nodes().List(metav1.ListOptions{})
	if err != nil {
		return
	}
	nodeNames := sets.NewString()
	for i := range nodes.Items {
		nodeNames.Insert(nodes.Items[i].Name)
	}

	for _, pod := range pods {
		if pod.Spec.NodeName == "" {
			continue
		}
		if nodeNames.Has(pod.Spec.NodeName) {
			continue
		}
		klog.V(2).Infof("Found orphaned Pod %v/%v assigned to the Node %v. Deleting.", pod.Namespace, pod.Name, pod.Spec.NodeName)
		if err := gcc.deletePod(pod.Namespace, pod.Name); err != nil {
			utilruntime.HandleError(err)
		} else {
			klog.V(0).Infof("Forced deletion of orphaned Pod %v/%v succeeded", pod.Namespace, pod.Name)
		}
	}
}

// gcUnscheduledTerminating deletes pods that are terminating and haven't been scheduled to a particular node.
func (gcc *PodGCController) gcUnscheduledTerminating(pods []*v1.Pod) {
	klog.V(4).Infof("GC'ing unscheduled pods which are terminating.")

	for _, pod := range pods {
		if pod.DeletionTimestamp == nil || len(pod.Spec.NodeName) > 0 {
			continue
		}

		klog.V(2).Infof("Found unscheduled terminating Pod %v/%v not assigned to any Node. Deleting.", pod.Namespace, pod.Name)
		if err := gcc.deletePod(pod.Namespace, pod.Name); err != nil {
			utilruntime.HandleError(err)
		} else {
			klog.V(0).Infof("Forced deletion of unscheduled terminating Pod %v/%v succeeded", pod.Namespace, pod.Name)
		}
	}
}

// byCreationTimestamp sorts a list by creation timestamp, using their names as a tie breaker.
type byCreationTimestamp []*v1.Pod

func (o byCreationTimestamp) Len() int      { return len(o) }
func (o byCreationTimestamp) Swap(i, j int) { o[i], o[j] = o[j], o[i] }

func (o byCreationTimestamp) Less(i, j int) bool {
	if o[i].CreationTimestamp.Equal(&o[j].CreationTimestamp) {
		return o[i].Name < o[j].Name
	}
	return o[i].CreationTimestamp.Before(&o[j].CreationTimestamp)
}