package node

import (
	"context"
	"sync"
	"time"

	"github.com/pkg/errors"
	"github.com/virtual-kubelet/virtual-kubelet/errdefs"
	"github.com/virtual-kubelet/virtual-kubelet/log"
	"github.com/virtual-kubelet/virtual-kubelet/trace"
	corev1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	corev1listers "k8s.io/client-go/listers/core/v1"
	"k8s.io/client-go/tools/cache"
)

const (
	podStatusReasonNotFound          = "NotFound"
	podStatusMessageNotFound         = "The pod status was not found and may have been deleted from the provider"
	containerStatusReasonNotFound    = "NotFound"
	containerStatusMessageNotFound   = "Container was not found and was likely deleted"
	containerStatusExitCodeNotFound  = -137
	statusTerminatedReason           = "Terminated"
	containerStatusTerminatedMessage = "Container was terminated. The exit code may not reflect the real exit code"
)

// syncProvderWrapper wraps a PodLifecycleHandler to give it async-like pod status notification behavior
type syncProviderWrapper struct {
	PodLifecycleHandler
	notify func(*corev1.Pod)
	l      corev1listers.PodLister

	// deletedPods makes sure we don't set the "NotFOund" status
	// for pods which have been requested to be deleted.
	// This is needed for our loop which just grabs pod statues every 5 seconds
	deletedPods sync.Map
}

// This is used to clean up keys for deleted pods after they have been fully deleted in the API server
type syncWrapper interface {
	_deletePodKey(context.Context, string)
}

func (p *syncProviderWrapper) NotifyPods(ctx context.Context, f func(*corev1.Pod)) {
	p.notify = f
}

func (p *syncProviderWrapper) _deletePodKey(ctx context.Context, key string) {
	log.G(ctx).WithField("key", key).Debug("Cleaning up pod from deletion cache")
	p.deletedPods.Delete(key)
}

func (p *syncProviderWrapper) DeletePod(ctx context.Context, pod *corev1.Pod) error {
	log.G(ctx).Debug("syncProviderWrappped.DeletePod")
	key, err := cache.MetaNamespaceKeyFunc(pod)
	if err != nil {
		return err
	}

	p.deletedPods.Store(key, pod)
	if err := p.PodLifecycleHandler.DeletePod(ctx, pod.DeepCopy()); err != nil {
		log.G(ctx).WithField("key", key).WithError(err).Debug("Removed key from deleted pods cache")
		// We aren't going to actually delete the pod from the provider since there is an error so delete it from our cache,
		// otherwise we could end up leaking pods in our deletion cache.
		// Delete will be retried by the pod controller.
		p.deletedPods.Delete(key)
		return err
	}

	if shouldSkipPodStatusUpdate(pod) {
		log.G(ctx).Debug("skipping pod status update for terminated pod")
		return nil
	}

	updated := pod.DeepCopy()
	updated.Status.Phase = corev1.PodSucceeded
	now := metav1.NewTime(time.Now())
	for i, cs := range updated.Status.ContainerStatuses {
		updated.Status.ContainerStatuses[i].State.Terminated = &corev1.ContainerStateTerminated{
			Reason:     statusTerminatedReason,
			Message:    containerStatusTerminatedMessage,
			FinishedAt: now,
		}
		if cs.State.Running != nil {
			updated.Status.ContainerStatuses[i].State.Terminated.StartedAt = cs.State.Running.StartedAt
		}
	}
	updated.Status.Reason = statusTerminatedReason

	p.notify(updated)
	log.G(ctx).Debug("Notified pod terminal pod status")

	return nil
}

func (p *syncProviderWrapper) run(ctx context.Context) {
	interval := 5 * time.Second
	timer := time.NewTimer(interval)

	defer timer.Stop()

	if !timer.Stop() {
		<-timer.C
	}

	for {
		log.G(ctx).Debug("Pod status update loop start")
		timer.Reset(interval)
		select {
		case <-ctx.Done():
			log.G(ctx).WithError(ctx.Err()).Debug("sync wrapper loop exiting")
			return
		case <-timer.C:
		}
		p.syncPodStatuses(ctx)
	}
}

func (p *syncProviderWrapper) syncPodStatuses(ctx context.Context) {
	ctx, span := trace.StartSpan(ctx, "syncProviderWrapper.syncPodStatuses")
	defer span.End()

	// Update all the pods with the provider status.
	pods, err := p.l.List(labels.Everything())
	if err != nil {
		err = errors.Wrap(err, "error getting pod list from kubernetes")
		span.SetStatus(err)
		log.G(ctx).WithError(err).Error("Error updating pod statuses")
		return
	}
	ctx = span.WithField(ctx, "nPods", int64(len(pods)))

	for _, pod := range pods {
		if shouldSkipPodStatusUpdate(pod) {
			log.G(ctx).Debug("Skipping pod status update")
			continue
		}

		if err := p.updatePodStatus(ctx, pod); err != nil {
			log.G(ctx).WithFields(map[string]interface{}{
				"name":      pod.Name,
				"namespace": pod.Namespace,
			}).WithError(err).Error("Could not fetch pod status")
		}
	}
}

func (p *syncProviderWrapper) updatePodStatus(ctx context.Context, podFromKubernetes *corev1.Pod) error {
	ctx, span := trace.StartSpan(ctx, "syncProviderWrapper.getPodStatus")
	defer span.End()
	ctx = addPodAttributes(ctx, span, podFromKubernetes)

	podStatus, err := p.PodLifecycleHandler.GetPodStatus(ctx, podFromKubernetes.Namespace, podFromKubernetes.Name)
	if err != nil {
		if !errdefs.IsNotFound(err) {
			span.SetStatus(err)
			return err
		}
	}
	if podStatus != nil {
		pod := podFromKubernetes.DeepCopy()
		podStatus.DeepCopyInto(&pod.Status)
		p.notify(pod)
		return nil
	}

	key, err := cache.MetaNamespaceKeyFunc(podFromKubernetes)
	if err != nil {
		return err
	}

	if _, exists := p.deletedPods.Load(key); exists {
		log.G(ctx).Debug("pod is in known deleted state, ignoring")
		return nil
	}

	// Only change the status when the pod was already up
	// Only doing so when the pod was successfully running makes sure we don't run into race conditions during pod creation.
	if podFromKubernetes.Status.Phase == corev1.PodRunning || time.Since(podFromKubernetes.ObjectMeta.CreationTimestamp.Time) > time.Minute {
		// Set the pod to failed, this makes sure if the underlying container implementation is gone that a new pod will be created.
		podStatus = podFromKubernetes.Status.DeepCopy()
		podStatus.Phase = corev1.PodFailed
		podStatus.Reason = podStatusReasonNotFound
		podStatus.Message = podStatusMessageNotFound
		now := metav1.NewTime(time.Now())
		for i, c := range podStatus.ContainerStatuses {
			if c.State.Running == nil {
				continue
			}
			podStatus.ContainerStatuses[i].State.Terminated = &corev1.ContainerStateTerminated{
				ExitCode:    containerStatusExitCodeNotFound,
				Reason:      containerStatusReasonNotFound,
				Message:     containerStatusMessageNotFound,
				FinishedAt:  now,
				StartedAt:   c.State.Running.StartedAt,
				ContainerID: c.ContainerID,
			}
			podStatus.ContainerStatuses[i].State.Running = nil
		}
		log.G(ctx).Debug("Setting pod not found on pod status")
	}

	pod := podFromKubernetes.DeepCopy()
	podStatus.DeepCopyInto(&pod.Status)
	p.notify(pod)
	return nil
}