package controlloop

import (
	"context"
	"encoding/json"
	"fmt"
	"net"
	"os"
	"strconv"
	"strings"
	"time"

	v1 "k8s.io/api/core/v1"
	"k8s.io/apimachinery/pkg/util/wait"
	v1coreinformerfactory "k8s.io/client-go/informers"
	v1corelisters "k8s.io/client-go/listers/core/v1"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/tools/record"
	"k8s.io/client-go/util/workqueue"

	nadv1 "github.com/k8snetworkplumbingwg/network-attachment-definition-client/pkg/apis/k8s.cni.cncf.io/v1"
	nadinformers "github.com/k8snetworkplumbingwg/network-attachment-definition-client/pkg/client/informers/externalversions"
	nadlister "github.com/k8snetworkplumbingwg/network-attachment-definition-client/pkg/client/listers/k8s.cni.cncf.io/v1"

	"github.com/k8snetworkplumbingwg/whereabouts/pkg/allocate"
	whereaboutsv1alpha1 "github.com/k8snetworkplumbingwg/whereabouts/pkg/api/whereabouts.cni.cncf.io/v1alpha1"
	wbinformers "github.com/k8snetworkplumbingwg/whereabouts/pkg/client/informers/externalversions"
	wblister "github.com/k8snetworkplumbingwg/whereabouts/pkg/client/listers/whereabouts.cni.cncf.io/v1alpha1"
	"github.com/k8snetworkplumbingwg/whereabouts/pkg/config"
	"github.com/k8snetworkplumbingwg/whereabouts/pkg/logging"
	wbclient "github.com/k8snetworkplumbingwg/whereabouts/pkg/storage/kubernetes"
	"github.com/k8snetworkplumbingwg/whereabouts/pkg/types"
)

const (
	defaultMountPath      = "/host"
	ipReconcilerQueueName = "pod-updates"
	syncPeriod            = time.Second
	whereaboutsConfigPath = "/etc/cni/net.d/whereabouts.d/whereabouts.conf"
	maxRetries            = 2
)

const (
	addressGarbageCollected        = "IPAddressGarbageCollected"
	addressGarbageCollectionFailed = "IPAddressGarbageCollectionFailed"
)

type garbageCollector func(ctx context.Context, mode int, ipamConf types.IPAMConfig, containerID string, podRef string) (net.IPNet, error)

type PodController struct {
	arePodsSynched          cache.InformerSynced
	areIPPoolsSynched       cache.InformerSynced
	areNetAttachDefsSynched cache.InformerSynced
	podsInformer            cache.SharedIndexInformer
	ipPoolInformer          cache.SharedIndexInformer
	netAttachDefInformer    cache.SharedIndexInformer
	podLister               v1corelisters.PodLister
	ipPoolLister            wblister.IPPoolLister
	netAttachDefLister      nadlister.NetworkAttachmentDefinitionLister
	broadcaster             record.EventBroadcaster
	recorder                record.EventRecorder
	workqueue               workqueue.RateLimitingInterface
	mountPath               string
	cleanupFunc             garbageCollector
}

// NewPodController ...
func NewPodController(k8sCoreInformerFactory v1coreinformerfactory.SharedInformerFactory, wbSharedInformerFactory wbinformers.SharedInformerFactory, netAttachDefInformerFactory nadinformers.SharedInformerFactory, broadcaster record.EventBroadcaster, recorder record.EventRecorder) *PodController {
	return newPodController(k8sCoreInformerFactory, wbSharedInformerFactory, netAttachDefInformerFactory, broadcaster, recorder, wbclient.IPManagement)
}

func newPodController(k8sCoreInformerFactory v1coreinformerfactory.SharedInformerFactory, wbSharedInformerFactory wbinformers.SharedInformerFactory, netAttachDefInformerFactory nadinformers.SharedInformerFactory, broadcaster record.EventBroadcaster, recorder record.EventRecorder, cleanupFunc garbageCollector) *PodController {
	k8sPodFilteredInformer := k8sCoreInformerFactory.Core().V1().Pods()
	ipPoolInformer := wbSharedInformerFactory.Whereabouts().V1alpha1().IPPools()
	netAttachDefInformer := netAttachDefInformerFactory.K8sCniCncfIo().V1().NetworkAttachmentDefinitions()

	poolInformer := ipPoolInformer.Informer()
	networksInformer := netAttachDefInformer.Informer()
	podsInformer := k8sPodFilteredInformer.Informer()

	queue := workqueue.NewNamedRateLimitingQueue(
		workqueue.DefaultControllerRateLimiter(),
		ipReconcilerQueueName)

	podsInformer.AddEventHandler(
		cache.ResourceEventHandlerFuncs{
			DeleteFunc: func(obj interface{}) {
				onPodDelete(queue, obj)
			},
		})

	return &PodController{
		arePodsSynched:          podsInformer.HasSynced,
		areIPPoolsSynched:       poolInformer.HasSynced,
		areNetAttachDefsSynched: networksInformer.HasSynced,
		broadcaster:             broadcaster,
		recorder:                recorder,
		podsInformer:            podsInformer,
		ipPoolInformer:          poolInformer,
		netAttachDefInformer:    networksInformer,
		podLister:               k8sPodFilteredInformer.Lister(),
		ipPoolLister:            ipPoolInformer.Lister(),
		netAttachDefLister:      netAttachDefInformer.Lister(),
		workqueue:               queue,
		cleanupFunc:             cleanupFunc,
	}
}

// Start runs worker thread after performing cache synchronization
func (pc *PodController) Start(stopChan <-chan struct{}) {
	logging.Verbosef("starting network controller")
	defer pc.workqueue.ShutDown()

	if ok := cache.WaitForCacheSync(stopChan, pc.arePodsSynched, pc.areNetAttachDefsSynched, pc.areIPPoolsSynched); !ok {
		logging.Verbosef("failed waiting for caches to sync")
	}

	go wait.Until(pc.worker, syncPeriod, stopChan)

	<-stopChan
	logging.Verbosef("shutting down network controller")
}

func (pc *PodController) worker() {
	for pc.processNextWorkItem() {
	}
}

func (pc *PodController) processNextWorkItem() bool {
	queueItem, shouldQuit := pc.workqueue.Get()
	if shouldQuit {
		return false
	}
	defer pc.workqueue.Done(queueItem)

	pod := queueItem.(*v1.Pod)
	err := pc.garbageCollectPodIPs(pod)
	logging.Verbosef("result of garbage collecting pods: %+v", err)
	pc.handleResult(pod, err)

	return true
}

func (pc *PodController) garbageCollectPodIPs(pod *v1.Pod) error {
	podNamespace := pod.GetNamespace()
	podName := pod.GetName()

	ifaceStatuses, err := podNetworkStatus(pod)
	if err != nil {
		return fmt.Errorf("failed to access the network status for pod [%s/%s]: %v", podName, podNamespace, err)
	}

	for _, ifaceStatus := range ifaceStatuses {
		if ifaceStatus.Default {
			logging.Verbosef("skipped net-attach-def for default network")
			continue
		}
		nad, err := pc.ifaceNetAttachDef(ifaceStatus)
		if err != nil {
			return fmt.Errorf("failed to get network-attachment-definition for iface %s: %+v", ifaceStatus.Name, err)
		}

		mountPath := defaultMountPath
		if pc.mountPath != "" {
			mountPath = pc.mountPath
		}

		logging.Verbosef("the NAD's config: %s", nad.Spec)
		ipamConfig, err := ipamConfiguration(nad, podNamespace, podName, mountPath)
		if err != nil && isInvalidPluginType(err) {
			logging.Debugf("error while computing something: %v", err)
			continue
		} else if err != nil {
			return fmt.Errorf("failed to create an IPAM configuration for the pod %s iface %s: %+v", podID(podNamespace, podName), ifaceStatus.Name, err)
		}

		pool, err := pc.ipPool(ipamConfig.Range)
		if err != nil {
			return fmt.Errorf("failed to get the IPPool data: %+v", err)
		}

		logging.Verbosef("pool range [%s]", pool.Spec.Range)
		for allocationIndex, allocation := range pool.Spec.Allocations {
			if allocation.PodRef == podID(podNamespace, podName) {
				logging.Verbosef("stale allocation to cleanup: %+v", allocation)

				if _, err := pc.cleanupFunc(context.TODO(), types.Deallocate, *ipamConfig, allocation.ContainerID, podID(podNamespace, podName)); err != nil {
					logging.Errorf("failed to cleanup allocation: %v", err)
				}
				if err := pc.addressGarbageCollected(pod, nad.GetName(), pool.Spec.Range, allocationIndex); err != nil {
					logging.Errorf("failed to issue event for successful IP address cleanup: %v", err)
				}
			}
		}
	}

	return nil
}

func isInvalidPluginType(err error) bool {
	_, isInvalidPluginError := err.(*config.InvalidPluginError)
	return isInvalidPluginError
}

func (pc *PodController) handleResult(pod *v1.Pod, err error) {
	if err == nil {
		pc.workqueue.Forget(pod)
		return
	}

	podNamespace := pod.GetNamespace()
	podName := pod.GetName()
	currentRetries := pc.workqueue.NumRequeues(pod)
	if currentRetries <= maxRetries {
		logging.Verbosef(
			"re-queuing IP address reconciliation request for pod %s; retry #: %d",
			podID(podNamespace, podName),
			currentRetries)
		pc.workqueue.AddRateLimited(pod)
		return
	}

	pc.addressGarbageCollectionFailed(pod, err)
}

func (pc *PodController) ifaceNetAttachDef(ifaceStatus nadv1.NetworkStatus) (*nadv1.NetworkAttachmentDefinition, error) {
	const (
		namespaceIndex = 0
		nameIndex      = 1
	)

	logging.Debugf("pod's network status: %+v", ifaceStatus)
	ifaceInfo := strings.Split(ifaceStatus.Name, "/")
	if len(ifaceInfo) < 2 {
		return nil, fmt.Errorf("pod %s name does not feature namespace/pod name syntax", ifaceStatus.Name)
	}

	netNamespaceName := ifaceInfo[namespaceIndex]
	netName := ifaceInfo[nameIndex]

	nad, err := pc.netAttachDefLister.NetworkAttachmentDefinitions(netNamespaceName).Get(netName)
	if err != nil {
		return nil, err
	}
	return nad, nil
}

func (pc *PodController) ipPool(cidr string) (*whereaboutsv1alpha1.IPPool, error) {
	pool, err := pc.ipPoolLister.IPPools(ipPoolsNamespace()).Get(wbclient.NormalizeRange(cidr))
	if err != nil {
		return nil, err
	}
	return pool, nil
}

func (pc *PodController) addressGarbageCollected(pod *v1.Pod, networkName string, ipRange string, allocationIndex string) error {
	if pc.recorder != nil {
		ip, _, err := net.ParseCIDR(ipRange)
		if err != nil {
			return err
		}
		index, err := strconv.Atoi(allocationIndex)
		if err != nil {
			return err
		}
		pc.recorder.Eventf(
			pod,
			v1.EventTypeNormal,
			addressGarbageCollected,
			"successful cleanup of IP address [%s] from network %s",
			allocate.IPAddOffset(ip, uint64(index)),
			networkName)
	}
	return nil
}

func (pc *PodController) addressGarbageCollectionFailed(pod *v1.Pod, err error) {
	logging.Errorf(
		"dropping pod [%s] deletion out of the queue - could not reconcile IP: %+v",
		podID(pod.GetNamespace(), pod.GetName()),
		err)

	pc.workqueue.Forget(pod)

	if pc.recorder != nil {
		pc.recorder.Eventf(
			pod,
			v1.EventTypeWarning,
			addressGarbageCollectionFailed,
			"failed to garbage collect addresses for pod %s",
			podID(pod.GetNamespace(), pod.GetName()))
	}
}

func onPodDelete(queue workqueue.RateLimitingInterface, obj interface{}) {
	pod, err := podFromTombstone(obj)
	if err != nil {
		logging.Errorf("cannot create pod object from %v on pod delete: %v", obj, err)
		return
	}

	logging.Verbosef("deleted pod [%s]", podID(pod.GetNamespace(), pod.GetName()))
	queue.Add(stripPod(pod)) // we only need the pod's metadata & its network-status annotations. Hence we strip it.
}

func podID(podNamespace string, podName string) string {
	return fmt.Sprintf("%s/%s", podNamespace, podName)
}

func podNetworkStatus(pod *v1.Pod) ([]nadv1.NetworkStatus, error) {
	var ifaceStatuses []nadv1.NetworkStatus
	networkStatus, found := pod.Annotations[nadv1.NetworkStatusAnnot]
	if found {
		if err := json.Unmarshal([]byte(networkStatus), &ifaceStatuses); err != nil {
			return nil, err
		}
	}
	return ifaceStatuses, nil
}

func ipamConfiguration(nad *nadv1.NetworkAttachmentDefinition, podNamespace string, podName string, mountPath string) (*types.IPAMConfig, error) {
	mounterWhereaboutsConfigFilePath := mountPath + whereaboutsConfigPath

	ipamConfig, err := config.LoadIPAMConfiguration([]byte(nad.Spec.Config), "", mounterWhereaboutsConfigFilePath)
	if err != nil {
		return nil, err
	}
	ipamConfig.PodName = podName
	ipamConfig.PodNamespace = podNamespace
	ipamConfig.Kubernetes.KubeConfigPath = mountPath + ipamConfig.Kubernetes.KubeConfigPath // must use the mount path

	return ipamConfig, nil
}

func ipPoolsNamespace() string {
	const wbNamespaceEnvVariableName = "WHEREABOUTS_NAMESPACE"
	if wbNamespace, found := os.LookupEnv(wbNamespaceEnvVariableName); found {
		return wbNamespace
	}

	const wbDefaultNamespace = "kube-system"
	return wbDefaultNamespace
}

func podFromTombstone(obj interface{}) (*v1.Pod, error) {
	pod, isPod := obj.(*v1.Pod)
	if !isPod {
		tombstone, ok := obj.(cache.DeletedFinalStateUnknown)
		if !ok {
			return nil, fmt.Errorf("received unexpected object: %v", obj)
		}
		pod, ok = tombstone.Obj.(*v1.Pod)
		if !ok {
			return nil, fmt.Errorf("deletedFinalStateUnknown contained non-Pod object: %v", tombstone.Obj)
		}
	}
	return pod, nil
}

func stripPod(pod *v1.Pod) *v1.Pod {
	newPod := pod.DeepCopy()
	newPod.Spec = v1.PodSpec{}
	newPod.Status = v1.PodStatus{}
	return newPod
}