/*

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 controllers

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"strings"

	"github.com/go-logr/logr"
	reconcilehelper "github.com/kubeflow/kubeflow/components/common/reconcilehelper"
	"github.com/kubeflow/kubeflow/components/notebook-controller/api/v1beta1"
	"github.com/kubeflow/kubeflow/components/notebook-controller/pkg/culler"
	"github.com/kubeflow/kubeflow/components/notebook-controller/pkg/metrics"
	appsv1 "k8s.io/api/apps/v1"
	corev1 "k8s.io/api/core/v1"
	apierrs "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/apimachinery/pkg/util/intstr"
	"k8s.io/client-go/tools/record"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"
	"sigs.k8s.io/controller-runtime/pkg/event"
	"sigs.k8s.io/controller-runtime/pkg/handler"
	"sigs.k8s.io/controller-runtime/pkg/predicate"
	"sigs.k8s.io/controller-runtime/pkg/reconcile"
	"sigs.k8s.io/controller-runtime/pkg/source"
)

const DefaultContainerPort = 8888
const DefaultServingPort = 80
const AnnotationRewriteURI = "notebooks.kubeflow.org/http-rewrite-uri"
const AnnotationHeadersRequestSet = "notebooks.kubeflow.org/http-headers-request-set"

// The default fsGroup of PodSecurityContext.
// https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.11/#podsecuritycontext-v1-core
const DefaultFSGroup = int64(100)

/*
We generally want to ignore (not requeue) NotFound errors, since we'll get a
reconciliation request once the object exists, and requeuing in the meantime
won't help.
*/
func ignoreNotFound(err error) error {
	if apierrs.IsNotFound(err) {
		return nil
	}
	return err
}

// NotebookReconciler reconciles a Notebook object
type NotebookReconciler struct {
	client.Client
	Log           logr.Logger
	Scheme        *runtime.Scheme
	Metrics       *metrics.Metrics
	EventRecorder record.EventRecorder
}

// +kubebuilder:rbac:groups=core,resources=pods,verbs=get;list;watch
// +kubebuilder:rbac:groups=core,resources=events,verbs=get;list;watch;create
// +kubebuilder:rbac:groups=core,resources=services,verbs="*"
// +kubebuilder:rbac:groups=apps,resources=statefulsets,verbs="*"
// +kubebuilder:rbac:groups=kubeflow.org,resources=notebooks;notebooks/status;notebooks/finalizers,verbs="*"
// +kubebuilder:rbac:groups="networking.istio.io",resources=virtualservices,verbs="*"

func (r *NotebookReconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
	ctx := context.Background()
	log := r.Log.WithValues("notebook", req.NamespacedName)

	// TODO(yanniszark): Can we avoid reconciling Events and Notebook in the same queue?
	event := &corev1.Event{}
	var getEventErr error
	getEventErr = r.Get(ctx, req.NamespacedName, event)
	if getEventErr == nil {
		involvedNotebook := &v1beta1.Notebook{}
		nbName, err := nbNameFromInvolvedObject(r.Client, &event.InvolvedObject)
		if err != nil {
			return ctrl.Result{}, err
		}
		involvedNotebookKey := types.NamespacedName{Name: nbName, Namespace: req.Namespace}
		if err := r.Get(ctx, involvedNotebookKey, involvedNotebook); err != nil {
			log.Error(err, "unable to fetch Notebook by looking at event")
			return ctrl.Result{}, ignoreNotFound(err)
		}
		r.EventRecorder.Eventf(involvedNotebook, event.Type, event.Reason,
			"Reissued from %s/%s: %s", strings.ToLower(event.InvolvedObject.Kind), event.InvolvedObject.Name, event.Message)
	}
	if getEventErr != nil && !apierrs.IsNotFound(getEventErr) {
		return ctrl.Result{}, getEventErr
	}
	// If not found, continue. Is not an event.

	instance := &v1beta1.Notebook{}
	if err := r.Get(ctx, req.NamespacedName, instance); err != nil {
		log.Error(err, "unable to fetch Notebook")
		return ctrl.Result{}, ignoreNotFound(err)
	}

	// Reconcile StatefulSet
	ss := generateStatefulSet(instance)
	if err := ctrl.SetControllerReference(instance, ss, r.Scheme); err != nil {
		return ctrl.Result{}, err
	}
	// Check if the StatefulSet already exists
	foundStateful := &appsv1.StatefulSet{}
	justCreated := false
	err := r.Get(ctx, types.NamespacedName{Name: ss.Name, Namespace: ss.Namespace}, foundStateful)
	if err != nil && apierrs.IsNotFound(err) {
		log.Info("Creating StatefulSet", "namespace", ss.Namespace, "name", ss.Name)
		r.Metrics.NotebookCreation.WithLabelValues(ss.Namespace).Inc()
		err = r.Create(ctx, ss)
		justCreated = true
		if err != nil {
			log.Error(err, "unable to create Statefulset")
			r.Metrics.NotebookFailCreation.WithLabelValues(ss.Namespace).Inc()
			return ctrl.Result{}, err
		}
	} else if err != nil {
		log.Error(err, "error getting Statefulset")
		return ctrl.Result{}, err
	}
	// Update the foundStateful object and write the result back if there are any changes
	if !justCreated && reconcilehelper.CopyStatefulSetFields(ss, foundStateful) {
		log.Info("Updating StatefulSet", "namespace", ss.Namespace, "name", ss.Name)
		err = r.Update(ctx, foundStateful)
		if err != nil {
			log.Error(err, "unable to update Statefulset")
			return ctrl.Result{}, err
		}
	}

	// Reconcile service
	service := generateService(instance)
	if err := ctrl.SetControllerReference(instance, service, r.Scheme); err != nil {
		return ctrl.Result{}, err
	}
	// Check if the Service already exists
	foundService := &corev1.Service{}
	justCreated = false
	err = r.Get(ctx, types.NamespacedName{Name: service.Name, Namespace: service.Namespace}, foundService)
	if err != nil && apierrs.IsNotFound(err) {
		log.Info("Creating Service", "namespace", service.Namespace, "name", service.Name)
		err = r.Create(ctx, service)
		justCreated = true
		if err != nil {
			log.Error(err, "unable to create Service")
			return ctrl.Result{}, err
		}
	} else if err != nil {
		log.Error(err, "error getting Statefulset")
		return ctrl.Result{}, err
	}
	// Update the foundService object and write the result back if there are any changes
	if !justCreated && reconcilehelper.CopyServiceFields(service, foundService) {
		log.Info("Updating Service\n", "namespace", service.Namespace, "name", service.Name)
		err = r.Update(ctx, foundService)
		if err != nil {
			log.Error(err, "unable to update Service")
			return ctrl.Result{}, err
		}
	}

	// Reconcile virtual service if we use ISTIO.
	if os.Getenv("USE_ISTIO") == "true" {
		err = r.reconcileVirtualService(instance)
		if err != nil {
			return ctrl.Result{}, err
		}
	}

	// Update the readyReplicas if the status is changed
	if foundStateful.Status.ReadyReplicas != instance.Status.ReadyReplicas {
		log.Info("Updating Status", "namespace", instance.Namespace, "name", instance.Name)
		instance.Status.ReadyReplicas = foundStateful.Status.ReadyReplicas
		err = r.Status().Update(ctx, instance)
		if err != nil {
			return ctrl.Result{}, err
		}
	}

	// Check the pod status
	pod := &corev1.Pod{}
	podFound := false
	err = r.Get(ctx, types.NamespacedName{Name: ss.Name + "-0", Namespace: ss.Namespace}, pod)
	if err != nil && apierrs.IsNotFound(err) {
		// This should be reconciled by the StatefulSet
		log.Info("Pod not found...")
	} else if err != nil {
		return ctrl.Result{}, err
	} else {
		// Got the pod
		podFound = true

		// Update status of the CR using the ContainerState of
		// the container that has the same name as the CR.
		// If no container of same name is found, the state of the CR is not updated.
		if len(pod.Status.ContainerStatuses) > 0 {
			notebookContainerFound := false
			for i := range pod.Status.ContainerStatuses {
				if pod.Status.ContainerStatuses[i].Name != instance.Name {
					continue
				}
				if pod.Status.ContainerStatuses[i].State == instance.Status.ContainerState {
					continue
				}

				log.Info("Updating Notebook CR state: ", "namespace", instance.Namespace, "name", instance.Name)
				cs := pod.Status.ContainerStatuses[i].State
				instance.Status.ContainerState = cs
				oldConditions := instance.Status.Conditions
				newCondition := getNextCondition(cs)
				// Append new condition
				if len(oldConditions) == 0 || oldConditions[0].Type != newCondition.Type ||
					oldConditions[0].Reason != newCondition.Reason ||
					oldConditions[0].Message != newCondition.Message {
					log.Info("Appending to conditions: ", "namespace", instance.Namespace, "name", instance.Name, "type", newCondition.Type, "reason", newCondition.Reason, "message", newCondition.Message)
					instance.Status.Conditions = append([]v1beta1.NotebookCondition{newCondition}, oldConditions...)
				}
				err = r.Status().Update(ctx, instance)
				if err != nil {
					return ctrl.Result{}, err
				}
				notebookContainerFound = true
				break

			}
			if !notebookContainerFound {
				log.Error(nil, "Could not find the Notebook container, will not update the status of the CR. No container has the same name as the CR.", "CR name:", instance.Name)
			}
		}
	}

	// Check if the Notebook needs to be stopped
	if podFound && culler.NotebookNeedsCulling(instance.ObjectMeta) {
		log.Info(fmt.Sprintf(
			"Notebook %s/%s needs culling. Setting annotations",
			instance.Namespace, instance.Name))

		// Set annotations to the Notebook
		culler.SetStopAnnotation(&instance.ObjectMeta, r.Metrics)
		r.Metrics.NotebookCullingCount.WithLabelValues(instance.Namespace, instance.Name).Inc()
		err = r.Update(ctx, instance)
		if err != nil {
			return ctrl.Result{}, err
		}
	} else if podFound && !culler.StopAnnotationIsSet(instance.ObjectMeta) {
		// The Pod is either too fresh, or the idle time has passed and it has
		// received traffic. In this case we will be periodically checking if
		// it needs culling.
		return ctrl.Result{RequeueAfter: culler.GetRequeueTime()}, nil
	}

	return ctrl.Result{}, nil
}

func getNextCondition(cs corev1.ContainerState) v1beta1.NotebookCondition {
	var nbtype = ""
	var nbreason = ""
	var nbmsg = ""

	if cs.Running != nil {
		nbtype = "Running"
	} else if cs.Waiting != nil {
		nbtype = "Waiting"
		nbreason = cs.Waiting.Reason
		nbmsg = cs.Waiting.Message
	} else {
		nbtype = "Terminated"
		nbreason = cs.Terminated.Reason
		nbmsg = cs.Terminated.Reason
	}

	newCondition := v1beta1.NotebookCondition{
		Type:          nbtype,
		LastProbeTime: metav1.Now(),
		Reason:        nbreason,
		Message:       nbmsg,
	}
	return newCondition
}

func generateStatefulSet(instance *v1beta1.Notebook) *appsv1.StatefulSet {
	replicas := int32(1)
	if culler.StopAnnotationIsSet(instance.ObjectMeta) {
		replicas = 0
	}

	ss := &appsv1.StatefulSet{
		ObjectMeta: metav1.ObjectMeta{
			Name:      instance.Name,
			Namespace: instance.Namespace,
		},
		Spec: appsv1.StatefulSetSpec{
			Replicas: &replicas,
			Selector: &metav1.LabelSelector{
				MatchLabels: map[string]string{
					"statefulset": instance.Name,
				},
			},
			Template: corev1.PodTemplateSpec{
				ObjectMeta: metav1.ObjectMeta{Labels: map[string]string{
					"statefulset":   instance.Name,
					"notebook-name": instance.Name,
				}},
				Spec: instance.Spec.Template.Spec,
			},
		},
	}
	// copy all of the Notebook labels to the pod including poddefault related labels
	l := &ss.Spec.Template.ObjectMeta.Labels
	for k, v := range instance.ObjectMeta.Labels {
		(*l)[k] = v
	}

	podSpec := &ss.Spec.Template.Spec
	container := &podSpec.Containers[0]
	if container.WorkingDir == "" {
		container.WorkingDir = "/home/jovyan"
	}
	if container.Ports == nil {
		container.Ports = []corev1.ContainerPort{
			{
				ContainerPort: DefaultContainerPort,
				Name:          "notebook-port",
				Protocol:      "TCP",
			},
		}
	}
	container.Env = append(container.Env, corev1.EnvVar{
		Name:  "NB_PREFIX",
		Value: "/notebook/" + instance.Namespace + "/" + instance.Name,
	})

	// For some platforms (like OpenShift), adding fsGroup: 100 is troublesome.
	// This allows for those platforms to bypass the automatic addition of the fsGroup
	// and will allow for the Pod Security Policy controller to make an appropriate choice
	// https://github.com/kubernetes-sigs/controller-runtime/issues/4617
	if value, exists := os.LookupEnv("ADD_FSGROUP"); !exists || value == "true" {
		if podSpec.SecurityContext == nil {
			fsGroup := DefaultFSGroup
			podSpec.SecurityContext = &corev1.PodSecurityContext{
				FSGroup: &fsGroup,
			}
		}
	}
	return ss
}

func generateService(instance *v1beta1.Notebook) *corev1.Service {
	// Define the desired Service object
	port := DefaultContainerPort
	containerPorts := instance.Spec.Template.Spec.Containers[0].Ports
	if containerPorts != nil {
		port = int(containerPorts[0].ContainerPort)
	}
	svc := &corev1.Service{
		ObjectMeta: metav1.ObjectMeta{
			Name:      instance.Name,
			Namespace: instance.Namespace,
		},
		Spec: corev1.ServiceSpec{
			Type:     "ClusterIP",
			Selector: map[string]string{"statefulset": instance.Name},
			Ports: []corev1.ServicePort{
				{
					// Make port name follow Istio pattern so it can be managed by istio rbac
					Name:       "http-" + instance.Name,
					Port:       DefaultServingPort,
					TargetPort: intstr.FromInt(port),
					Protocol:   "TCP",
				},
			},
		},
	}
	return svc
}

func virtualServiceName(kfName string, namespace string) string {
	return fmt.Sprintf("notebook-%s-%s", namespace, kfName)
}

func generateVirtualService(instance *v1beta1.Notebook) (*unstructured.Unstructured, error) {
	name := instance.Name
	namespace := instance.Namespace
	clusterDomain := "cluster.local"
	prefix := fmt.Sprintf("/notebook/%s/%s/", namespace, name)

	// unpack annotations from Notebook resource
	annotations := make(map[string]string)
	for k, v := range instance.ObjectMeta.Annotations {
		annotations[k] = v
	}

	rewrite := fmt.Sprintf("/notebook/%s/%s/", namespace, name)
	// If AnnotationRewriteURI is present, use this value for "rewrite"
	if _, ok := annotations[AnnotationRewriteURI]; ok && len(annotations[AnnotationRewriteURI]) > 0 {
		rewrite = annotations[AnnotationRewriteURI]
	}

	if clusterDomainFromEnv, ok := os.LookupEnv("CLUSTER_DOMAIN"); ok {
		clusterDomain = clusterDomainFromEnv
	}
	service := fmt.Sprintf("%s.%s.svc.%s", name, namespace, clusterDomain)

	vsvc := &unstructured.Unstructured{}
	vsvc.SetAPIVersion("networking.istio.io/v1alpha3")
	vsvc.SetKind("VirtualService")
	vsvc.SetName(virtualServiceName(name, namespace))
	vsvc.SetNamespace(namespace)
	if err := unstructured.SetNestedStringSlice(vsvc.Object, []string{"*"}, "spec", "hosts"); err != nil {
		return nil, fmt.Errorf("Set .spec.hosts error: %v", err)
	}

	istioGateway := os.Getenv("ISTIO_GATEWAY")
	if len(istioGateway) == 0 {
		istioGateway = "kubeflow/kubeflow-gateway"
	}
	if err := unstructured.SetNestedStringSlice(vsvc.Object, []string{istioGateway},
		"spec", "gateways"); err != nil {
		return nil, fmt.Errorf("Set .spec.gateways error: %v", err)
	}

	headersRequestSet := make(map[string]string)
	// If AnnotationHeadersRequestSet is present, use its values in "headers.request.set"
	if _, ok := annotations[AnnotationHeadersRequestSet]; ok && len(annotations[AnnotationHeadersRequestSet]) > 0 {
		requestHeadersBytes := []byte(annotations[AnnotationHeadersRequestSet])
		if err := json.Unmarshal(requestHeadersBytes, &headersRequestSet); err != nil {
			// if JSON decoding fails, set an empty map
			headersRequestSet = make(map[string]string)
		}
	}
	// cast from map[string]string, as SetNestedSlice needs map[string]interface{}
	headersRequestSetInterface := make(map[string]interface{})
	for key, element := range headersRequestSet {
		headersRequestSetInterface[key] = element
	}

	// the http section of the istio VirtualService spec
	http := []interface{}{
		map[string]interface{}{
			"headers": map[string]interface{}{
				"request": map[string]interface{}{
					"set": headersRequestSetInterface,
				},
			},
			"match": []interface{}{
				map[string]interface{}{
					"uri": map[string]interface{}{
						"prefix": prefix,
					},
				},
			},
			"rewrite": map[string]interface{}{
				"uri": rewrite,
			},
			"route": []interface{}{
				map[string]interface{}{
					"destination": map[string]interface{}{
						"host": service,
						"port": map[string]interface{}{
							"number": int64(DefaultServingPort),
						},
					},
				},
			},
			"timeout": "300s",
		},
	}

	// add http section to istio VirtualService spec
	if err := unstructured.SetNestedSlice(vsvc.Object, http, "spec", "http"); err != nil {
		return nil, fmt.Errorf("Set .spec.http error: %v", err)
	}

	return vsvc, nil

}

func (r *NotebookReconciler) reconcileVirtualService(instance *v1beta1.Notebook) error {
	log := r.Log.WithValues("notebook", instance.Namespace)
	virtualService, err := generateVirtualService(instance)
	if err := ctrl.SetControllerReference(instance, virtualService, r.Scheme); err != nil {
		return err
	}
	// Check if the virtual service already exists.
	foundVirtual := &unstructured.Unstructured{}
	justCreated := false
	foundVirtual.SetAPIVersion("networking.istio.io/v1alpha3")
	foundVirtual.SetKind("VirtualService")
	err = r.Get(context.TODO(), types.NamespacedName{Name: virtualServiceName(instance.Name,
		instance.Namespace), Namespace: instance.Namespace}, foundVirtual)
	if err != nil && apierrs.IsNotFound(err) {
		log.Info("Creating virtual service", "namespace", instance.Namespace, "name",
			virtualServiceName(instance.Name, instance.Namespace))
		err = r.Create(context.TODO(), virtualService)
		justCreated = true
		if err != nil {
			return err
		}
	} else if err != nil {
		return err
	}

	if !justCreated && reconcilehelper.CopyVirtualService(virtualService, foundVirtual) {
		log.Info("Updating virtual service", "namespace", instance.Namespace, "name",
			virtualServiceName(instance.Name, instance.Namespace))
		err = r.Update(context.TODO(), foundVirtual)
		if err != nil {
			return err
		}
	}

	return nil
}

func isStsOrPodEvent(event *corev1.Event) bool {
	return event.InvolvedObject.Kind == "Pod" || event.InvolvedObject.Kind == "StatefulSet"
}

func nbNameFromInvolvedObject(c client.Client, object *corev1.ObjectReference) (string, error) {
	name, namespace := object.Name, object.Namespace

	if object.Kind == "StatefulSet" {
		return name, nil
	}
	if object.Kind == "Pod" {
		pod := &corev1.Pod{}
		err := c.Get(
			context.TODO(),
			types.NamespacedName{
				Namespace: namespace,
				Name:      name,
			},
			pod,
		)
		if err != nil {
			return "", err
		}
		if nbName, ok := pod.Labels["notebook-name"]; ok {
			return nbName, nil
		}
	}
	return "", fmt.Errorf("object isn't related to a Notebook")
}

func nbNameExists(client client.Client, nbName string, namespace string) bool {
	if err := client.Get(context.Background(), types.NamespacedName{Namespace: namespace, Name: nbName}, &v1beta1.Notebook{}); err != nil {
		// If error != NotFound, trigger the reconcile call anyway to avoid loosing a potential relevant event
		return !apierrs.IsNotFound(err)
	}
	return true
}

func (r *NotebookReconciler) SetupWithManager(mgr ctrl.Manager) error {
	builder := ctrl.NewControllerManagedBy(mgr).
		For(&v1beta1.Notebook{}).
		Owns(&appsv1.StatefulSet{}).
		Owns(&corev1.Service{})
	// watch Istio virtual service
	if os.Getenv("USE_ISTIO") == "true" {
		virtualService := &unstructured.Unstructured{}
		virtualService.SetAPIVersion("networking.istio.io/v1alpha3")
		virtualService.SetKind("VirtualService")
		builder.Owns(virtualService)
	}

	// TODO(lunkai): After this is fixed:
	// https://github.com/kubernetes-sigs/controller-runtime/issues/572
	// We don't have to call Build to get the controller.
	c, err := builder.Build(r)
	if err != nil {
		return err
	}

	// watch underlying pod
	mapFn := handler.ToRequestsFunc(
		func(a handler.MapObject) []ctrl.Request {
			return []ctrl.Request{
				{NamespacedName: types.NamespacedName{
					Name:      a.Meta.GetLabels()["notebook-name"],
					Namespace: a.Meta.GetNamespace(),
				}},
			}
		})
	p := predicate.Funcs{
		UpdateFunc: func(e event.UpdateEvent) bool {
			if _, ok := e.MetaOld.GetLabels()["notebook-name"]; !ok {
				return false
			}
			return e.ObjectOld != e.ObjectNew
		},
		CreateFunc: func(e event.CreateEvent) bool {
			if _, ok := e.Meta.GetLabels()["notebook-name"]; !ok {
				return false
			}
			return true
		},
	}

	eventToRequest := handler.ToRequestsFunc(
		func(a handler.MapObject) []ctrl.Request {
			return []reconcile.Request{
				{NamespacedName: types.NamespacedName{
					Name:      a.Meta.GetName(),
					Namespace: a.Meta.GetNamespace(),
				}},
			}
		})

	eventsPredicates := predicate.Funcs{
		UpdateFunc: func(e event.UpdateEvent) bool {
			event := e.ObjectNew.(*corev1.Event)
			nbName, err := nbNameFromInvolvedObject(r.Client, &event.InvolvedObject)
			if err != nil {
				return false
			}
			return e.ObjectOld != e.ObjectNew &&
				isStsOrPodEvent(event) &&
				nbNameExists(r.Client, nbName, e.MetaNew.GetNamespace())
		},
		CreateFunc: func(e event.CreateEvent) bool {
			event := e.Object.(*corev1.Event)
			nbName, err := nbNameFromInvolvedObject(r.Client, &event.InvolvedObject)
			if err != nil {
				return false
			}
			return isStsOrPodEvent(event) &&
				nbNameExists(r.Client, nbName, e.Meta.GetNamespace())
		},
	}

	if err = c.Watch(
		&source.Kind{Type: &corev1.Pod{}},
		&handler.EnqueueRequestsFromMapFunc{
			ToRequests: mapFn,
		},
		p); err != nil {
		return err
	}

	if err = c.Watch(
		&source.Kind{Type: &corev1.Event{}},
		&handler.EnqueueRequestsFromMapFunc{
			ToRequests: eventToRequest,
		},
		eventsPredicates); err != nil {
		return err
	}

	return nil
}