package public

import (
	"context"
	"fmt"
	"math"
	"strings"
	"time"

	"github.com/prometheus/common/model"
	pb "github.com/runconduit/conduit/controller/gen/public"
	"github.com/runconduit/conduit/pkg/k8s"
	log "github.com/sirupsen/logrus"
	appsv1beta2 "k8s.io/api/apps/v1beta2"
	apiv1 "k8s.io/api/core/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/labels"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/client-go/tools/cache"
)

type promType string
type promResult struct {
	prom promType
	vec  model.Vector
	err  error
}

const (
	reqQuery             = "sum(increase(response_total%s[%s])) by (%s, classification)"
	latencyQuantileQuery = "histogram_quantile(%s, sum(irate(response_latency_ms_bucket%s[%s])) by (le, %s))"

	promRequests   = promType("QUERY_REQUESTS")
	promLatencyP50 = promType("0.5")
	promLatencyP95 = promType("0.95")
	promLatencyP99 = promType("0.99")

	deploymentLabel            = model.LabelName("deployment")
	namespaceLabel             = model.LabelName("namespace")
	podLabel                   = model.LabelName("pod")
	replicationControllerLabel = model.LabelName("replication_controller")
	serviceLabel               = model.LabelName("service")

	dstNamespaceLabel = model.LabelName("dst_namespace")
)

var (
	promTypes = []promType{promRequests, promLatencyP50, promLatencyP95, promLatencyP99}

	k8sResourceTypesToPromLabels = map[string]model.LabelName{
		k8s.KubernetesDeployments:            deploymentLabel,
		k8s.KubernetesNamespaces:             namespaceLabel,
		k8s.KubernetesPods:                   podLabel,
		k8s.KubernetesReplicationControllers: replicationControllerLabel,
		k8s.KubernetesServices:               serviceLabel,
	}
)

type meshedCount struct {
	inMesh uint64
	total  uint64
}

func (s *grpcServer) StatSummary(ctx context.Context, req *pb.StatSummaryRequest) (*pb.StatSummaryResponse, error) {
	var err error
	var objectMap map[string]metav1.ObjectMeta
	var meshCount map[string]*meshedCount

	switch req.Selector.Resource.Type {
	case k8s.KubernetesDeployments:
		objectMap, meshCount, err = s.getDeployments(req.Selector.Resource)
	case k8s.KubernetesNamespaces:
		objectMap, meshCount, err = s.getNamespaces(req.Selector.Resource)
	case k8s.KubernetesPods:
		objectMap, meshCount, err = s.getPods(req.Selector.Resource)
	case k8s.KubernetesReplicationControllers:
		objectMap, meshCount, err = s.getReplicationControllers(req.Selector.Resource)
	case k8s.KubernetesServices:

		switch req.Outbound.(type) {
		case *pb.StatSummaryRequest_FromResource:
			objectMap, meshCount, err = s.getServices(req.Selector.Resource)
		default:
			err = fmt.Errorf("Service only supported as a target on 'from' queries, or as a destination on 'to' queries.")
		}

	default:
		err = fmt.Errorf("Unimplemented resource type: %v", req.Selector.Resource.Type)
	}
	if err != nil {
		return nil, err
	}

	return s.objectQuery(ctx, req, objectMap, meshCount)
}

func (s *grpcServer) objectQuery(
	ctx context.Context,
	req *pb.StatSummaryRequest,
	objects map[string]metav1.ObjectMeta,
	meshCount map[string]*meshedCount,
) (*pb.StatSummaryResponse, error) {
	rows := make([]*pb.StatTable_PodGroup_Row, 0)

	requestMetrics, err := s.getRequests(ctx, req, req.TimeWindow)
	if err != nil {
		return nil, err
	}

	var keys []string

	if req.GetOutbound() == nil || req.GetNone() != nil {
		// if this request doesn't have outbound filtering, return all rows
		for key := range objects {
			keys = append(keys, key)
		}
	} else {
		// otherwise only return rows for which we have stats
		for key := range requestMetrics {
			keys = append(keys, key)
		}
	}

	for _, key := range keys {
		resource, ok := objects[key]
		if !ok {
			continue
		}

		row := pb.StatTable_PodGroup_Row{
			Resource: &pb.Resource{
				Namespace: resource.Namespace,
				Type:      req.Selector.Resource.Type,
				Name:      resource.Name,
			},
			TimeWindow: req.TimeWindow,
			Stats:      requestMetrics[key],
		}

		if count, ok := meshCount[key]; ok {
			row.MeshedPodCount = count.inMesh
			row.TotalPodCount = count.total
		}

		rows = append(rows, &row)
	}

	rsp := pb.StatSummaryResponse{
		Response: &pb.StatSummaryResponse_Ok_{ // https://github.com/golang/protobuf/issues/205
			Ok: &pb.StatSummaryResponse_Ok{
				StatTables: []*pb.StatTable{
					&pb.StatTable{
						Table: &pb.StatTable_PodGroup_{
							PodGroup: &pb.StatTable_PodGroup{
								Rows: rows,
							},
						},
					},
				},
			},
		},
	}

	return &rsp, nil
}

func promLabelNames(resource *pb.Resource) model.LabelNames {
	names := model.LabelNames{namespaceLabel}
	if resource.Type != k8s.KubernetesNamespaces {
		names = append(names, promResourceType(resource))
	}
	return names
}

func promDstLabelNames(resource *pb.Resource) model.LabelNames {
	names := model.LabelNames{dstNamespaceLabel}
	if resource.Type != k8s.KubernetesNamespaces {
		names = append(names, "dst_"+promResourceType(resource))
	}
	return names
}

func promLabels(resource *pb.Resource) model.LabelSet {
	set := model.LabelSet{}
	if resource.Name != "" {
		set[promResourceType(resource)] = model.LabelValue(resource.Name)
	}
	if resource.Type != k8s.KubernetesNamespaces && resource.Namespace != "" {
		set[namespaceLabel] = model.LabelValue(resource.Namespace)
	}
	return set
}

func promDstLabels(resource *pb.Resource) model.LabelSet {
	set := model.LabelSet{}
	if resource.Name != "" {
		set["dst_"+promResourceType(resource)] = model.LabelValue(resource.Name)
	}
	if resource.Type != k8s.KubernetesNamespaces && resource.Namespace != "" {
		set[dstNamespaceLabel] = model.LabelValue(resource.Namespace)
	}
	return set
}

func promDirectionLabels(direction string) model.LabelSet {
	return model.LabelSet{
		model.LabelName("direction"): model.LabelValue(direction),
	}
}

func promResourceType(resource *pb.Resource) model.LabelName {
	return k8sResourceTypesToPromLabels[resource.Type]
}

func buildRequestLabels(req *pb.StatSummaryRequest) (model.LabelSet, model.LabelNames) {
	var labelNames model.LabelNames
	labels := model.LabelSet{}

	switch out := req.Outbound.(type) {
	case *pb.StatSummaryRequest_ToResource:
		labelNames = promLabelNames(req.Selector.Resource)
		labels = labels.Merge(promDstLabels(out.ToResource))
		labels = labels.Merge(promLabels(req.Selector.Resource))
		labels = labels.Merge(promDirectionLabels("outbound"))

	case *pb.StatSummaryRequest_FromResource:
		labelNames = promDstLabelNames(req.Selector.Resource)
		labels = labels.Merge(promLabels(out.FromResource))
		labels = labels.Merge(promDirectionLabels("outbound"))

	default:
		labelNames = promLabelNames(req.Selector.Resource)
		labels = labels.Merge(promLabels(req.Selector.Resource))
		labels = labels.Merge(promDirectionLabels("inbound"))

	}

	return labels, labelNames
}

func (s *grpcServer) getRequests(ctx context.Context, req *pb.StatSummaryRequest, timeWindow string) (map[string]*pb.BasicStats, error) {
	reqLabels, groupBy := buildRequestLabels(req)
	resultChan := make(chan promResult)

	// kick off 4 asynchronous queries: 1 request volume + 3 latency
	go func() {
		requestsQuery := fmt.Sprintf(reqQuery, reqLabels, timeWindow, groupBy)
		resultVector, err := s.queryProm(ctx, requestsQuery)

		resultChan <- promResult{
			prom: promRequests,
			vec:  resultVector,
			err:  err,
		}
	}()

	for _, quantile := range []promType{promLatencyP50, promLatencyP95, promLatencyP99} {
		go func(quantile promType) {
			latencyQuery := fmt.Sprintf(latencyQuantileQuery, quantile, reqLabels, timeWindow, groupBy)
			latencyResult, err := s.queryProm(ctx, latencyQuery)

			resultChan <- promResult{
				prom: quantile,
				vec:  latencyResult,
				err:  err,
			}
		}(quantile)
	}

	// process results, receive one message per prometheus query type
	var err error
	results := []promResult{}
	for i := 0; i < len(promTypes); i++ {
		result := <-resultChan
		if result.err != nil {
			log.Errorf("queryProm failed with: %s", result.err)
			err = result.err
		} else {
			results = append(results, result)
		}
	}
	if err != nil {
		return nil, err
	}

	return processRequests(results, groupBy), nil
}

func processRequests(results []promResult, groupBy model.LabelNames) map[string]*pb.BasicStats {
	basicStats := make(map[string]*pb.BasicStats)

	for _, result := range results {
		for _, sample := range result.vec {
			label := metricToKey(sample.Metric, groupBy)
			if basicStats[label] == nil {
				basicStats[label] = &pb.BasicStats{}
			}

			value := uint64(0)
			if !math.IsNaN(float64(sample.Value)) {
				value = uint64(math.Round(float64(sample.Value)))
			}

			switch result.prom {
			case promRequests:
				switch string(sample.Metric[model.LabelName("classification")]) {
				case "success":
					basicStats[label].SuccessCount = value
				case "failure":
					basicStats[label].FailureCount = value
				}
			case promLatencyP50:
				basicStats[label].LatencyMsP50 = value
			case promLatencyP95:
				basicStats[label].LatencyMsP95 = value
			case promLatencyP99:
				basicStats[label].LatencyMsP99 = value
			}
		}
	}

	return basicStats
}

func metricToKey(metric model.Metric, groupBy model.LabelNames) string {
	values := []string{}
	for _, k := range groupBy {
		values = append(values, string(metric[k]))
	}
	return strings.Join(values, "/")
}

func (s *grpcServer) getDeployments(res *pb.Resource) (map[string]metav1.ObjectMeta, map[string]*meshedCount, error) {
	var err error
	var deployments []*appsv1beta2.Deployment

	if res.Namespace == "" {
		deployments, err = s.deployLister.List(labels.Everything())
	} else if res.Name == "" {
		deployments, err = s.deployLister.Deployments(res.Namespace).List(labels.Everything())
	} else {
		var deployment *appsv1beta2.Deployment
		deployment, err = s.deployLister.Deployments(res.Namespace).Get(res.Name)
		deployments = []*appsv1beta2.Deployment{deployment}
	}

	if err != nil {
		return nil, nil, err
	}

	meshedPodCount := make(map[string]*meshedCount)
	deploymentMap := make(map[string]metav1.ObjectMeta)
	for _, deployment := range deployments {
		key, err := cache.MetaNamespaceKeyFunc(deployment)
		if err != nil {
			return nil, nil, err
		}
		deploymentMap[key] = deployment.ObjectMeta

		meshCount, err := s.getMeshedPodCount(deployment.Namespace, deployment)
		if err != nil {
			return nil, nil, err
		}
		meshedPodCount[key] = meshCount
	}

	return deploymentMap, meshedPodCount, nil
}

func (s *grpcServer) getNamespaces(res *pb.Resource) (map[string]metav1.ObjectMeta, map[string]*meshedCount, error) {
	var err error
	var namespaces []*apiv1.Namespace

	if res.Name == "" {
		namespaces, err = s.namespaceLister.List(labels.Everything())
	} else {
		var namespace *apiv1.Namespace
		namespace, err = s.namespaceLister.Get(res.Name)
		namespaces = []*apiv1.Namespace{namespace}
	}

	if err != nil {
		return nil, nil, err
	}

	meshedPodCount := make(map[string]*meshedCount)
	namespaceMap := make(map[string]metav1.ObjectMeta)
	for _, namespace := range namespaces {
		key, err := cache.MetaNamespaceKeyFunc(namespace)
		if err != nil {
			return nil, nil, err
		}
		namespaceMap[key] = namespace.ObjectMeta

		meshCount, err := s.getMeshedPodCount(namespace.Name, namespace)
		if err != nil {
			return nil, nil, err
		}
		meshedPodCount[key] = meshCount
	}

	return namespaceMap, meshedPodCount, nil
}

func (s *grpcServer) getPods(res *pb.Resource) (map[string]metav1.ObjectMeta, map[string]*meshedCount, error) {
	var err error
	var pods []*apiv1.Pod

	if res.Namespace == "" {
		pods, err = s.podLister.List(labels.Everything())
	} else if res.Name == "" {
		pods, err = s.podLister.Pods(res.Namespace).List(labels.Everything())
	} else {
		var pod *apiv1.Pod
		pod, err = s.podLister.Pods(res.Namespace).Get(res.Name)
		pods = []*apiv1.Pod{pod}
	}

	if err != nil {
		return nil, nil, err
	}

	meshedPodCount := make(map[string]*meshedCount)
	podMap := make(map[string]metav1.ObjectMeta)
	for _, pod := range pods {
		if !isPendingOrRunning(pod) {
			continue
		}

		key, err := cache.MetaNamespaceKeyFunc(pod)
		if err != nil {
			return nil, nil, err
		}
		podMap[key] = pod.ObjectMeta

		meshCount := &meshedCount{total: 1}
		if isInMesh(pod) {
			meshCount.inMesh++
		}
		meshedPodCount[key] = meshCount
	}

	return podMap, meshedPodCount, nil
}

func (s *grpcServer) getReplicationControllers(res *pb.Resource) (map[string]metav1.ObjectMeta, map[string]*meshedCount, error) {
	var err error
	var rcs []*apiv1.ReplicationController

	if res.Namespace == "" {
		rcs, err = s.replicationControllerLister.List(labels.Everything())
	} else if res.Name == "" {
		rcs, err = s.replicationControllerLister.ReplicationControllers(res.Namespace).List(labels.Everything())
	} else {
		var rc *apiv1.ReplicationController
		rc, err = s.replicationControllerLister.ReplicationControllers(res.Namespace).Get(res.Name)
		rcs = []*apiv1.ReplicationController{rc}
	}

	if err != nil {
		return nil, nil, err
	}

	meshedPodCount := make(map[string]*meshedCount)
	rcMap := make(map[string]metav1.ObjectMeta)
	for _, rc := range rcs {
		key, err := cache.MetaNamespaceKeyFunc(rc)
		if err != nil {
			return nil, nil, err
		}
		rcMap[key] = rc.ObjectMeta

		meshCount, err := s.getMeshedPodCount(rc.Namespace, rc)
		if err != nil {
			return nil, nil, err
		}
		meshedPodCount[key] = meshCount
	}

	return rcMap, meshedPodCount, nil
}

func (s *grpcServer) getServices(res *pb.Resource) (map[string]metav1.ObjectMeta, map[string]*meshedCount, error) {
	var err error
	var services []*apiv1.Service

	if res.Namespace == "" {
		services, err = s.serviceLister.List(labels.Everything())
	} else if res.Name == "" {
		services, err = s.serviceLister.Services(res.Namespace).List(labels.Everything())
	} else {
		var svc *apiv1.Service
		svc, err = s.serviceLister.Services(res.Namespace).Get(res.Name)
		services = []*apiv1.Service{svc}
	}

	if err != nil {
		return nil, nil, err
	}

	meshedPodCount := make(map[string]*meshedCount)
	svcMap := make(map[string]metav1.ObjectMeta)
	for _, svc := range services {
		key, err := cache.MetaNamespaceKeyFunc(svc)
		if err != nil {
			return nil, nil, err
		}
		svcMap[key] = svc.ObjectMeta

		meshCount, err := s.getMeshedPodCount(svc.Namespace, svc)
		if err != nil {
			return nil, nil, err
		}
		meshedPodCount[key] = meshCount
	}

	return svcMap, meshedPodCount, nil
}

func (s *grpcServer) getMeshedPodCount(namespace string, obj runtime.Object) (*meshedCount, error) {
	selector, err := getSelectorFromObject(obj)
	if err != nil {
		return nil, err
	}

	pods, err := s.podLister.Pods(namespace).List(selector)
	if err != nil {
		return nil, err
	}

	meshCount := &meshedCount{}
	for _, pod := range pods {
		if !isPendingOrRunning(pod) {
			continue
		}

		meshCount.total++
		if isInMesh(pod) {
			meshCount.inMesh++
		}
	}

	return meshCount, nil
}

func isInMesh(pod *apiv1.Pod) bool {
	_, ok := pod.Annotations[k8s.ProxyVersionAnnotation]
	return ok
}

func isPendingOrRunning(pod *apiv1.Pod) bool {
	pending := pod.Status.Phase == apiv1.PodPending
	running := pod.Status.Phase == apiv1.PodRunning
	terminating := pod.DeletionTimestamp != nil
	return (pending || running) && !terminating
}

func getSelectorFromObject(obj runtime.Object) (labels.Selector, error) {
	switch typed := obj.(type) {
	case *apiv1.Namespace:
		return labels.Everything(), nil

	case *appsv1beta2.Deployment:
		return labels.Set(typed.Spec.Selector.MatchLabels).AsSelector(), nil

	case *apiv1.ReplicationController:
		return labels.Set(typed.Spec.Selector).AsSelector(), nil

	case *apiv1.Service:
		return labels.Set(typed.Spec.Selector).AsSelector(), nil

	default:
		return nil, fmt.Errorf("Cannot get object selector: %v", obj)
	}
}

func (s *grpcServer) queryProm(ctx context.Context, query string) (model.Vector, error) {
	log.Debugf("Query request: %+v", query)

	// single data point (aka summary) query
	res, err := s.prometheusAPI.Query(ctx, query, time.Time{})
	if err != nil {
		log.Errorf("Query(%+v) failed with: %+v", query, err)
		return nil, err
	}
	log.Debugf("Query response: %+v", res)

	if res.Type() != model.ValVector {
		err = fmt.Errorf("Unexpected query result type (expected Vector): %s", res.Type())
		log.Error(err)
		return nil, err
	}

	return res.(model.Vector), nil
}