package controllers

import (
	"context"
	"time"

	"k8s.io/apimachinery/pkg/api/errors"

	aboutv1alpha1 "github.com/aws/aws-cloud-map-mcs-controller-for-k8s/pkg/apis/about/v1alpha1"
	"github.com/aws/aws-cloud-map-mcs-controller-for-k8s/pkg/cloudmap"
	"github.com/aws/aws-cloud-map-mcs-controller-for-k8s/pkg/common"
	"github.com/aws/aws-cloud-map-mcs-controller-for-k8s/pkg/model"
	"github.com/aws/aws-cloud-map-mcs-controller-for-k8s/pkg/version"
	"github.com/aws/aws-sdk-go-v2/aws"
	v1 "k8s.io/api/core/v1"
	discovery "k8s.io/api/discovery/v1"

	"k8s.io/apimachinery/pkg/types"
	"k8s.io/client-go/util/workqueue"
	"sigs.k8s.io/controller-runtime/pkg/builder"
	"sigs.k8s.io/controller-runtime/pkg/controller"
	"sigs.k8s.io/controller-runtime/pkg/controller/controllerutil"
	"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"

	"k8s.io/apimachinery/pkg/runtime"
	ctrl "sigs.k8s.io/controller-runtime"
	"sigs.k8s.io/controller-runtime/pkg/client"

	multiclusterv1alpha1 "github.com/aws/aws-cloud-map-mcs-controller-for-k8s/pkg/apis/multicluster/v1alpha1"
)

// ServiceExportReconciler reconciles a ServiceExport object
type ServiceExportReconciler struct {
	Client       client.Client
	Log          common.Logger
	Scheme       *runtime.Scheme
	CloudMap     cloudmap.ServiceDiscoveryClient
	ClusterUtils model.ClusterUtils
}

// +kubebuilder:rbac:groups="",resources=services,verbs=get
// +kubebuilder:rbac:groups=about.k8s.io,resources=clusterproperties,verbs=create;get;list;watch;update;patch;delete
// +kubebuilder:rbac:groups="discovery.k8s.io",resources=endpointslices,verbs=list;watch;create
// +kubebuilder:rbac:groups=multicluster.x-k8s.io,resources=serviceexports,verbs=get;list;watch;update;patch
// +kubebuilder:rbac:groups=multicluster.x-k8s.io,resources=serviceexports/finalizers,verbs=get;update

func (r *ServiceExportReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	namespace := req.Namespace
	name := req.NamespacedName
	r.Log.Debug("reconciling ServiceExport", "Namespace", namespace, "Name", name)

	serviceExport := multiclusterv1alpha1.ServiceExport{}
	if err := r.Client.Get(ctx, name, &serviceExport); err != nil {
		if errors.IsNotFound(err) {
			r.Log.Debug("no ServiceExport found",
				"Namespace", namespace, "Name", name)
		} else {
			r.Log.Error(err, "error fetching ServiceExport",
				"Namespace", namespace, "Name", name)
		}
		return ctrl.Result{}, nil
	}

	// Mark ServiceExport to be deleted, which is indicated by the deletion timestamp being set.
	isServiceExportMarkedForDelete := !serviceExport.GetDeletionTimestamp().IsZero()

	service := v1.Service{}
	namespacedName := types.NamespacedName{Namespace: serviceExport.Namespace, Name: serviceExport.Name}
	if err := r.Client.Get(ctx, namespacedName, &service); err != nil {
		if errors.IsNotFound(err) {
			r.Log.Info("no Service found, deleting the ServiceExport", "Namespace", serviceExport.Namespace, "Name", serviceExport.Name)
			// Mark ServiceExport to be deleted, if the corresponding Service is not found
			isServiceExportMarkedForDelete = true
		} else {
			r.Log.Error(err, "error fetching Service", "Namespace", serviceExport.Namespace, "Name", serviceExport.Name)
			return ctrl.Result{}, nil
		}
	}

	clusterProperties, err := r.ClusterUtils.GetClusterProperties(ctx)
	if err != nil {
		r.Log.Error(err, "unable to retrieve ClusterId and ClusterSetId")
		return ctrl.Result{}, err
	}

	// Check if the service export is marked to be deleted
	if isServiceExportMarkedForDelete {
		return r.handleDelete(ctx, clusterProperties.ClusterId(), &serviceExport)
	}

	return r.handleUpdate(ctx, clusterProperties.ClusterId(), &serviceExport, &service)
}

func (r *ServiceExportReconciler) handleUpdate(ctx context.Context, clusterId string, serviceExport *multiclusterv1alpha1.ServiceExport, service *v1.Service) (ctrl.Result, error) {
	err := r.addFinalizerAndOwnerRef(ctx, serviceExport, service)
	if err != nil {
		return ctrl.Result{}, err
	}

	r.Log.Info("updating Cloud Map service", "namespace", service.Namespace, "name", service.Name)
	cmService, err := r.createOrGetCloudMapService(ctx, service)
	if err != nil {
		r.Log.Error(err, "error fetching Service from Cloud Map", "namespace", service.Namespace, "name", service.Name)
		return ctrl.Result{}, err
	}

	endpoints, err := r.extractEndpoints(ctx, service, serviceExport)
	if err != nil {
		r.Log.Error(err, "error extracting Endpoints", "namespace", serviceExport.Namespace, "name", serviceExport.Name)
		return ctrl.Result{}, err
	}

	// Compute diff between Cloud Map and K8s endpoints, and apply changes
	plan := model.Plan{
		Current: cmService.GetEndpoints(clusterId),
		Desired: endpoints,
	}
	changes := plan.CalculateChanges()

	if changes.HasUpdates() {
		// merge creates and updates (Cloud Map RegisterEndpoints can handle both)
		upserts := changes.Create
		upserts = append(upserts, changes.Update...)

		if err := r.CloudMap.RegisterEndpoints(ctx, service.Namespace, service.Name, upserts); err != nil {
			r.Log.Error(err, "error registering Endpoints to Cloud Map", "namespace", service.Namespace, "name", service.Name)
			return ctrl.Result{}, err
		}
	}

	if changes.HasDeletes() {
		if err := r.CloudMap.DeleteEndpoints(ctx, service.Namespace, service.Name, changes.Delete); err != nil {
			r.Log.Error(err, "error deleting Endpoints from Cloud Map", "namespace", cmService.Namespace, "name", cmService.Name)
			return ctrl.Result{}, err
		}
	}

	if changes.IsNone() {
		r.Log.Info("no changes to export to Cloud Map", "namespace", service.Namespace, "name", service.Name)
	}

	return ctrl.Result{}, nil
}

func (r *ServiceExportReconciler) addFinalizerAndOwnerRef(ctx context.Context, serviceExport *multiclusterv1alpha1.ServiceExport, service *v1.Service) error {
	// Add the finalizer to the service export if not present, ensures the ServiceExport won't be deleted
	if !controllerutil.ContainsFinalizer(serviceExport, ServiceExportFinalizer) {
		controllerutil.AddFinalizer(serviceExport, ServiceExportFinalizer)
		if err := r.Client.Update(ctx, serviceExport); err != nil {
			r.Log.Error(err, "error adding finalizer", "Namespace", serviceExport.Namespace, "Name", serviceExport.Name)
			return err
		}
	}
	if len(serviceExport.GetOwnerReferences()) == 0 {
		err := controllerutil.SetControllerReference(service, serviceExport, r.Scheme)
		if err == nil {
			err = r.Client.Update(ctx, serviceExport)
		}
		if err != nil {
			r.Log.Error(err, "error setting Service as an owner of the ServiceExport", "namespace", service.Namespace, "name", service.Name)
			return err
		}
	}
	return nil
}

func (r *ServiceExportReconciler) createOrGetCloudMapService(ctx context.Context, service *v1.Service) (*model.Service, error) {
	cmService, err := r.CloudMap.GetService(ctx, service.Namespace, service.Name)
	if common.IsUnknown(err) {
		return nil, err
	}

	if common.IsNotFound(err) {
		err = r.CloudMap.CreateService(ctx, service.Namespace, service.Name)
		if err != nil {
			r.Log.Error(err, "error creating a new Service in Cloud Map", "namespace", service.Namespace, "name", service.Name)
			return nil, err
		}
		if cmService, err = r.CloudMap.GetService(ctx, service.Namespace, service.Name); err != nil {
			return nil, err
		}
	}

	return cmService, nil
}

func (r *ServiceExportReconciler) handleDelete(ctx context.Context, clusterId string, serviceExport *multiclusterv1alpha1.ServiceExport) (ctrl.Result, error) {
	if controllerutil.ContainsFinalizer(serviceExport, ServiceExportFinalizer) {
		r.Log.Info("removing service export", "namespace", serviceExport.Namespace, "name", serviceExport.Name)

		cmService, err := r.CloudMap.GetService(ctx, serviceExport.Namespace, serviceExport.Name)
		if common.IsUnknown(err) {
			r.Log.Error(err, "error fetching Service from Cloud Map", "namespace", serviceExport.Namespace, "name", serviceExport.Name)
			return ctrl.Result{}, err
		}
		if cmService != nil {
			if err := r.CloudMap.DeleteEndpoints(ctx, cmService.Namespace, cmService.Name, cmService.GetEndpoints(clusterId)); err != nil {
				r.Log.Error(err, "error deleting Endpoints from Cloud Map", "namespace", cmService.Namespace, "name", cmService.Name)
				return ctrl.Result{}, err
			}
		}

		// Remove finalizer. Once all finalizers have been
		// removed, the ServiceExport object will be deleted.
		controllerutil.RemoveFinalizer(serviceExport, ServiceExportFinalizer)
		if err := r.Client.Update(ctx, serviceExport); err != nil {
			return ctrl.Result{}, err
		}
	}

	return ctrl.Result{}, nil
}

func (r *ServiceExportReconciler) extractEndpoints(ctx context.Context, svc *v1.Service, svcExport *multiclusterv1alpha1.ServiceExport) ([]*model.Endpoint, error) {
	clusterProperties, err := r.ClusterUtils.GetClusterProperties(ctx)
	if err != nil {
		r.Log.Error(err, "unable to retrieve ClusterId and ClusterSetId")
		return nil, err
	}

	endpointSlices := discovery.EndpointSliceList{}
	err = r.Client.List(ctx, &endpointSlices,
		client.InNamespace(svc.Namespace), client.MatchingLabels{discovery.LabelServiceName: svc.Name})

	if err != nil {
		return nil, err
	}

	serviceType := ExtractServiceType(svc)

	servicePortMap := make(map[string]model.Port)
	for _, svcPort := range svc.Spec.Ports {
		servicePortMap[svcPort.Name] = ServicePortToPort(svcPort)
	}

	var svcExportCreationTimestamp int64 = 0
	if !svcExport.ObjectMeta.CreationTimestamp.IsZero() {
		svcExportCreationTimestamp = svcExport.ObjectMeta.CreationTimestamp.Time.UnixMilli()
	}

	attributes := make(map[string]string)
	attributes[model.K8sVersionAttr] = version.GetPackageVersion()

	endpoints := make([]*model.Endpoint, 0)
	for _, slice := range endpointSlices.Items {
		for _, endpointPort := range slice.Ports {
			for _, endpoint := range slice.Endpoints {
				port := EndpointPortToPort(endpointPort)
				readyCondition := aws.ToBool(endpoint.Conditions.Ready)

				for _, IP := range endpoint.Addresses {
					endpoints = append(endpoints, &model.Endpoint{
						Id:                             model.EndpointIdFromIPAddressAndPort(IP, port),
						IP:                             IP,
						AddressType:                    slice.AddressType,
						EndpointPort:                   port,
						ServicePort:                    servicePortMap[*endpointPort.Name],
						ClusterId:                      clusterProperties.ClusterId(),
						ClusterSetId:                   clusterProperties.ClusterSetId(),
						ServiceType:                    serviceType,
						ServiceExportCreationTimestamp: svcExportCreationTimestamp,
						Ready:                          readyCondition,
						Hostname:                       aws.ToString(endpoint.Hostname),
						Nodename:                       aws.ToString(endpoint.NodeName),
						Attributes:                     attributes,
					})
				}
			}
		}
	}

	return endpoints, nil
}

func (r *ServiceExportReconciler) SetupWithManager(mgr ctrl.Manager) error {
	return ctrl.NewControllerManagedBy(mgr).
		For(&multiclusterv1alpha1.ServiceExport{}).
		// Filter-out all the events if the cluster-properties are not found
		WithEventFilter(r.clusterPropertyFilter()).
		// Watch for the changes to Service which have corresponding ServiceExport
		Watches(
			&source.Kind{Type: &v1.Service{}},
			&handler.EnqueueRequestForObject{},
			builder.WithPredicates(r.serviceExportPredicates()),
		).
		// Watch for the changes to the EndpointSlice object which have corresponding ServiceExport.
		// This object is bound to be updated when Deployment are updated.
		Watches(
			&source.Kind{Type: &discovery.EndpointSlice{}},
			handler.EnqueueRequestsFromMapFunc(r.endpointSliceMappingFunction()),
			builder.WithPredicates(r.serviceExportPredicates()),
		).
		// Watch for changes to ClusterProperty objects. If a ClusterProperty object is
		// created, updated or deleted, the controller will reconcile all service exports
		Watches(
			&source.Kind{Type: &aboutv1alpha1.ClusterProperty{}},
			handler.EnqueueRequestsFromMapFunc(r.clusterPropertyMappingFunction()),
		).
		WithOptions(controller.Options{
			// rate-limiting is applied to reconcile responses with an error
			// We are increasing the base delay to 500ms, defaults baseDelay: 5ms, maxDelay: 1000s
			RateLimiter: workqueue.NewItemExponentialFailureRateLimiter(500*time.Millisecond, 1000*time.Second),
		}).
		Complete(r)
}

func (r *ServiceExportReconciler) endpointSliceMappingFunction() handler.MapFunc {
	return func(object client.Object) []reconcile.Request {
		labels := object.GetLabels()
		serviceName := labels[discovery.LabelServiceName]
		return []reconcile.Request{
			{NamespacedName: types.NamespacedName{
				Name:      serviceName,
				Namespace: object.GetNamespace(),
			}},
		}
	}
}

func (r *ServiceExportReconciler) clusterPropertyMappingFunction() handler.MapFunc {
	// Return reconcile requests for all service exports
	return func(object client.Object) []reconcile.Request {
		// Reset clusterproperties if there is an &aboutv1alpha1.ClusterProperty{} event
		err := r.ClusterUtils.LoadClusterProperties(context.TODO())
		if err != nil {
			return nil
		}

		serviceExports := &multiclusterv1alpha1.ServiceExportList{}
		if err := r.Client.List(context.TODO(), serviceExports); err != nil {
			r.Log.Error(err, "error listing ServiceExports")
			return nil
		}

		result := make([]reconcile.Request, 0)
		for _, serviceExport := range serviceExports.Items {
			result = append(result, reconcile.Request{NamespacedName: types.NamespacedName{
				Name:      serviceExport.Name,
				Namespace: serviceExport.Namespace,
			}})
		}
		return result
	}
}

func (r *ServiceExportReconciler) serviceExportPredicates() predicate.Funcs {
	return predicate.Funcs{
		GenericFunc: func(e event.GenericEvent) bool {
			return r.doesObjectHaveServiceExport(e.Object)
		},
		CreateFunc: func(e event.CreateEvent) bool {
			return r.doesObjectHaveServiceExport(e.Object)
		},
		UpdateFunc: func(e event.UpdateEvent) bool {
			return r.doesObjectHaveServiceExport(e.ObjectNew)
		},
		DeleteFunc: func(e event.DeleteEvent) bool {
			return r.doesObjectHaveServiceExport(e.Object)
		},
	}
}

func (r *ServiceExportReconciler) doesObjectHaveServiceExport(object client.Object) bool {
	serviceName, ok := object.GetLabels()[discovery.LabelServiceName]
	if !ok {
		serviceName = object.GetName()
	}
	ns := types.NamespacedName{
		Name:      serviceName,
		Namespace: object.GetNamespace(),
	}
	svcExport := multiclusterv1alpha1.ServiceExport{}
	if err := r.Client.Get(context.TODO(), ns, &svcExport); err != nil {
		return false
	}
	return true
}

func (r *ServiceExportReconciler) clusterPropertyFilter() predicate.Funcs {
	return predicate.Funcs{
		GenericFunc: func(e event.GenericEvent) bool {
			return r.doesClusterPropertyExists()
		},
		CreateFunc: func(e event.CreateEvent) bool {
			return r.doesClusterPropertyExists()
		},
		UpdateFunc: func(e event.UpdateEvent) bool {
			return r.doesClusterPropertyExists()
		},
		DeleteFunc: func(e event.DeleteEvent) bool {
			return r.doesClusterPropertyExists()
		},
	}
}

func (r *ServiceExportReconciler) doesClusterPropertyExists() bool {
	clusterProperties, err := r.ClusterUtils.GetClusterProperties(context.TODO())
	if err != nil {
		r.Log.Error(err, "unable to retrieve ClusterId and ClusterSetId")
		return false
	}
	r.Log.Debug("clusterProperties found", "ClusterId", clusterProperties.ClusterId(), "ClusterSetId", clusterProperties.ClusterSetId())
	return clusterProperties.IsValid()
}