/*
Copyright 2016 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 populator implements interfaces that monitor and keep the states of the
caches in sync with the "ground truth".
*/
package populator

import (
	"fmt"
	"sync"
	"time"

	"github.com/golang/glog"

	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
	"k8s.io/kubernetes/pkg/kubelet/pod"
	"k8s.io/kubernetes/pkg/kubelet/util/format"
	"k8s.io/kubernetes/pkg/kubelet/volumemanager/cache"
	"k8s.io/kubernetes/pkg/types"
	"k8s.io/kubernetes/pkg/util/wait"
	"k8s.io/kubernetes/pkg/volume"
	volumetypes "k8s.io/kubernetes/pkg/volume/util/types"
	"k8s.io/kubernetes/pkg/volume/util/volumehelper"
)

// DesiredStateOfWorldPopulator periodically loops through the list of active
// pods and ensures that each one exists in the desired state of the world cache
// if it has volumes. It also verifies that the pods in the desired state of the
// world cache still exist, if not, it removes them.
type DesiredStateOfWorldPopulator interface {
	Run(stopCh <-chan struct{})

	// ReprocessPod removes the specified pod from the list of processedPods
	// (if it exists) forcing it to be reprocessed. This is required to enable
	// remounting volumes on pod updates (volumes like Downward API volumes
	// depend on this behavior to ensure volume content is updated).
	ReprocessPod(podName volumetypes.UniquePodName)
}

// NewDesiredStateOfWorldPopulator returns a new instance of
// DesiredStateOfWorldPopulator.
//
// kubeClient - used to fetch PV and PVC objects from the API server
// loopSleepDuration - the amount of time the populator loop sleeps between
//     successive executions
// podManager - the kubelet podManager that is the source of truth for the pods
//     that exist on this host
// desiredStateOfWorld - the cache to populate
func NewDesiredStateOfWorldPopulator(
	kubeClient internalclientset.Interface,
	loopSleepDuration time.Duration,
	getPodStatusRetryDuration time.Duration,
	podManager pod.Manager,
	desiredStateOfWorld cache.DesiredStateOfWorld,
	kubeContainerRuntime kubecontainer.Runtime) DesiredStateOfWorldPopulator {
	return &desiredStateOfWorldPopulator{
		kubeClient:                kubeClient,
		loopSleepDuration:         loopSleepDuration,
		getPodStatusRetryDuration: getPodStatusRetryDuration,
		podManager:                podManager,
		desiredStateOfWorld:       desiredStateOfWorld,
		pods: processedPods{
			processedPods: make(map[volumetypes.UniquePodName]bool)},
		kubeContainerRuntime: kubeContainerRuntime,
	}
}

type desiredStateOfWorldPopulator struct {
	kubeClient                internalclientset.Interface
	loopSleepDuration         time.Duration
	getPodStatusRetryDuration time.Duration
	podManager                pod.Manager
	desiredStateOfWorld       cache.DesiredStateOfWorld
	pods                      processedPods
	kubeContainerRuntime      kubecontainer.Runtime
	timeOfLastGetPodStatus    time.Time
}

type processedPods struct {
	processedPods map[volumetypes.UniquePodName]bool
	sync.RWMutex
}

func (dswp *desiredStateOfWorldPopulator) Run(stopCh <-chan struct{}) {
	wait.Until(dswp.populatorLoopFunc(), dswp.loopSleepDuration, stopCh)
}

func (dswp *desiredStateOfWorldPopulator) ReprocessPod(
	podName volumetypes.UniquePodName) {
	dswp.deleteProcessedPod(podName)
}

func (dswp *desiredStateOfWorldPopulator) populatorLoopFunc() func() {
	return func() {
		dswp.findAndAddNewPods()

		// findAndRemoveDeletedPods() calls out to the container runtime to
		// determine if the containers for a given pod are terminated. This is
		// an expensive operation, therefore we limit the rate that
		// findAndRemoveDeletedPods() is called independently of the main
		// populator loop.
		if time.Since(dswp.timeOfLastGetPodStatus) < dswp.getPodStatusRetryDuration {
			glog.V(5).Infof(
				"Skipping findAndRemoveDeletedPods(). Not permitted until %v (getPodStatusRetryDuration %v).",
				dswp.timeOfLastGetPodStatus.Add(dswp.getPodStatusRetryDuration),
				dswp.getPodStatusRetryDuration)

			return
		}

		dswp.findAndRemoveDeletedPods()
	}
}

// Iterate through all pods and add to desired state of world if they don't
// exist but should
func (dswp *desiredStateOfWorldPopulator) findAndAddNewPods() {
	for _, pod := range dswp.podManager.GetPods() {
		dswp.processPodVolumes(pod)
	}
}

// Iterate through all pods in desired state of world, and remove if they no
// longer exist
func (dswp *desiredStateOfWorldPopulator) findAndRemoveDeletedPods() {
	var runningPods []*kubecontainer.Pod

	runningPodsFetched := false
	for _, volumeToMount := range dswp.desiredStateOfWorld.GetVolumesToMount() {
		if _, podExists :=
			dswp.podManager.GetPodByUID(volumeToMount.Pod.UID); podExists {
			continue
		}

		// Once a pod has been deleted from kubelet pod manager, do not delete
		// it immediately from volume manager. Instead, check the kubelet
		// containerRuntime to verify that all containers in the pod have been
		// terminated.
		if !runningPodsFetched {
			var getPodsErr error
			runningPods, getPodsErr = dswp.kubeContainerRuntime.GetPods(false)
			if getPodsErr != nil {
				glog.Errorf(
					"kubeContainerRuntime.findAndRemoveDeletedPods returned error %v.",
					getPodsErr)
				continue
			}

			runningPodsFetched = true
			dswp.timeOfLastGetPodStatus = time.Now()
		}

		runningContainers := false
		for _, runningPod := range runningPods {
			if runningPod.ID == volumeToMount.Pod.UID {
				if len(runningPod.Containers) > 0 {
					runningContainers = true
				}

				break
			}
		}

		if runningContainers {
			glog.V(5).Infof(
				"Pod %q has been removed from pod manager. However, it still has one or more containers in the non-exited state. Therefore, it will not be removed from volume manager.",
				format.Pod(volumeToMount.Pod))
			continue
		}

		glog.V(5).Infof(
			"Removing volume %q (volSpec=%q) for pod %q from desired state.",
			volumeToMount.VolumeName,
			volumeToMount.VolumeSpec.Name(),
			format.Pod(volumeToMount.Pod))

		dswp.desiredStateOfWorld.DeletePodFromVolume(
			volumeToMount.PodName, volumeToMount.VolumeName)
		dswp.deleteProcessedPod(volumeToMount.PodName)
	}
}

// processPodVolumes processes the volumes in the given pod and adds them to the
// desired state of the world.
func (dswp *desiredStateOfWorldPopulator) processPodVolumes(pod *api.Pod) {
	if pod == nil {
		return
	}

	uniquePodName := volumehelper.GetUniquePodName(pod)
	if dswp.podPreviouslyProcessed(uniquePodName) {
		return
	}

	// Process volume spec for each volume defined in pod
	for _, podVolume := range pod.Spec.Volumes {
		volumeSpec, volumeGidValue, err :=
			dswp.createVolumeSpec(podVolume, pod.Namespace)
		if err != nil {
			glog.Errorf(
				"Error processing volume %q for pod %q: %v",
				podVolume.Name,
				format.Pod(pod),
				err)
			continue
		}

		// Add volume to desired state of world
		_, err = dswp.desiredStateOfWorld.AddPodToVolume(
			uniquePodName, pod, volumeSpec, podVolume.Name, volumeGidValue)
		if err != nil {
			glog.Errorf(
				"Failed to add volume %q (specName: %q) for pod %q to desiredStateOfWorld. err=%v",
				podVolume.Name,
				volumeSpec.Name(),
				uniquePodName,
				err)
		}

		glog.V(10).Infof(
			"Added volume %q (volSpec=%q) for pod %q to desired state.",
			podVolume.Name,
			volumeSpec.Name(),
			uniquePodName)
	}

	dswp.markPodProcessed(uniquePodName)
}

// podPreviouslyProcessed returns true if the volumes for this pod have already
// been processed by the populator
func (dswp *desiredStateOfWorldPopulator) podPreviouslyProcessed(
	podName volumetypes.UniquePodName) bool {
	dswp.pods.RLock()
	defer dswp.pods.RUnlock()

	_, exists := dswp.pods.processedPods[podName]
	return exists
}

// markPodProcessed records that the volumes for the specified pod have been
// processed by the populator
func (dswp *desiredStateOfWorldPopulator) markPodProcessed(
	podName volumetypes.UniquePodName) {
	dswp.pods.Lock()
	defer dswp.pods.Unlock()

	dswp.pods.processedPods[podName] = true
}

// markPodProcessed removes the specified pod from processedPods
func (dswp *desiredStateOfWorldPopulator) deleteProcessedPod(
	podName volumetypes.UniquePodName) {
	dswp.pods.Lock()
	defer dswp.pods.Unlock()

	delete(dswp.pods.processedPods, podName)
}

// createVolumeSpec creates and returns a mutatable volume.Spec object for the
// specified volume. It dereference any PVC to get PV objects, if needed.
func (dswp *desiredStateOfWorldPopulator) createVolumeSpec(
	podVolume api.Volume, podNamespace string) (*volume.Spec, string, error) {
	if pvcSource :=
		podVolume.VolumeSource.PersistentVolumeClaim; pvcSource != nil {
		glog.V(10).Infof(
			"Found PVC, ClaimName: %q/%q",
			podNamespace,
			pvcSource.ClaimName)

		// If podVolume is a PVC, fetch the real PV behind the claim
		pvName, pvcUID, err := dswp.getPVCExtractPV(
			podNamespace, pvcSource.ClaimName)
		if err != nil {
			return nil, "", fmt.Errorf(
				"error processing PVC %q/%q: %v",
				podNamespace,
				pvcSource.ClaimName,
				err)
		}

		glog.V(10).Infof(
			"Found bound PV for PVC (ClaimName %q/%q pvcUID %v): pvName=%q",
			podNamespace,
			pvcSource.ClaimName,
			pvcUID,
			pvName)

		// Fetch actual PV object
		volumeSpec, volumeGidValue, err :=
			dswp.getPVSpec(pvName, pvcSource.ReadOnly, pvcUID)
		if err != nil {
			return nil, "", fmt.Errorf(
				"error processing PVC %q/%q: %v",
				podNamespace,
				pvcSource.ClaimName,
				err)
		}

		glog.V(10).Infof(
			"Extracted volumeSpec (%v) from bound PV (pvName %q) and PVC (ClaimName %q/%q pvcUID %v)",
			volumeSpec.Name,
			pvName,
			podNamespace,
			pvcSource.ClaimName,
			pvcUID)

		return volumeSpec, volumeGidValue, nil
	}

	// Do not return the original volume object, since the source could mutate it
	clonedPodVolumeObj, err := api.Scheme.DeepCopy(podVolume)
	if err != nil || clonedPodVolumeObj == nil {
		return nil, "", fmt.Errorf(
			"failed to deep copy %q volume object. err=%v", podVolume.Name, err)
	}

	clonedPodVolume, ok := clonedPodVolumeObj.(api.Volume)
	if !ok {
		return nil, "", fmt.Errorf(
			"failed to cast clonedPodVolume %#v to api.Volume",
			clonedPodVolumeObj)
	}

	return volume.NewSpecFromVolume(&clonedPodVolume), "", nil
}

// getPVCExtractPV fetches the PVC object with the given namespace and name from
// the API server extracts the name of the PV it is pointing to and returns it.
// An error is returned if the PVC object's phase is not "Bound".
func (dswp *desiredStateOfWorldPopulator) getPVCExtractPV(
	namespace string, claimName string) (string, types.UID, error) {
	pvc, err :=
		dswp.kubeClient.Core().PersistentVolumeClaims(namespace).Get(claimName)
	if err != nil || pvc == nil {
		return "", "", fmt.Errorf(
			"failed to fetch PVC %s/%s from API server. err=%v",
			namespace,
			claimName,
			err)
	}

	if pvc.Status.Phase != api.ClaimBound || pvc.Spec.VolumeName == "" {
		return "", "", fmt.Errorf(
			"PVC %s/%s has non-bound phase (%q) or empty pvc.Spec.VolumeName (%q)",
			namespace,
			claimName,
			pvc.Status.Phase,
			pvc.Spec.VolumeName)
	}

	return pvc.Spec.VolumeName, pvc.UID, nil
}

// getPVSpec fetches the PV object with the given name from the API server
// and returns a volume.Spec representing it.
// An error is returned if the call to fetch the PV object fails.
func (dswp *desiredStateOfWorldPopulator) getPVSpec(
	name string,
	pvcReadOnly bool,
	expectedClaimUID types.UID) (*volume.Spec, string, error) {
	pv, err := dswp.kubeClient.Core().PersistentVolumes().Get(name)
	if err != nil || pv == nil {
		return nil, "", fmt.Errorf(
			"failed to fetch PV %q from API server. err=%v", name, err)
	}

	if pv.Spec.ClaimRef == nil {
		return nil, "", fmt.Errorf(
			"found PV object %q but it has a nil pv.Spec.ClaimRef indicating it is not yet bound to the claim",
			name)
	}

	if pv.Spec.ClaimRef.UID != expectedClaimUID {
		return nil, "", fmt.Errorf(
			"found PV object %q but its pv.Spec.ClaimRef.UID (%q) does not point to claim.UID (%q)",
			name,
			pv.Spec.ClaimRef.UID,
			expectedClaimUID)
	}

	volumeGidValue := getPVVolumeGidAnnotationValue(pv)
	return volume.NewSpecFromPersistentVolume(pv, pvcReadOnly), volumeGidValue, nil
}

func getPVVolumeGidAnnotationValue(pv *api.PersistentVolume) string {
	if volumeGid, ok := pv.Annotations[volumehelper.VolumeGidAnnotationKey]; ok {
		return volumeGid
	}

	return ""
}
