package router

import (
	"context"
	"fmt"

	"github.com/google/go-cmp/cmp"
	"github.com/google/go-cmp/cmp/cmpopts"
	gloov1 "github.com/weaveworks/flagger/pkg/apis/gloo/v1"
	"go.uber.org/zap"
	"k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/client-go/kubernetes"

	flaggerv1 "github.com/weaveworks/flagger/pkg/apis/flagger/v1beta1"
	clientset "github.com/weaveworks/flagger/pkg/client/clientset/versioned"
)

// GlooRouter is managing Istio virtual services
type GlooRouter struct {
	kubeClient          kubernetes.Interface
	glooClient          clientset.Interface
	flaggerClient       clientset.Interface
	logger              *zap.SugaredLogger
	upstreamDiscoveryNs string
}

// Reconcile creates or updates the Istio virtual service
func (gr *GlooRouter) Reconcile(canary *flaggerv1.Canary) error {
	apexName, _, _ := canary.GetServiceNames()
	canaryName := fmt.Sprintf("%s-%s-canary-%v", canary.Namespace, apexName, canary.Spec.Service.Port)
	primaryName := fmt.Sprintf("%s-%s-primary-%v", canary.Namespace, apexName, canary.Spec.Service.Port)

	newSpec := gloov1.UpstreamGroupSpec{
		Destinations: []gloov1.WeightedDestination{
			{
				Destination: gloov1.Destination{
					Upstream: gloov1.ResourceRef{
						Name:      primaryName,
						Namespace: gr.upstreamDiscoveryNs,
					},
				},
				Weight: 100,
			},
			{
				Destination: gloov1.Destination{
					Upstream: gloov1.ResourceRef{
						Name:      canaryName,
						Namespace: gr.upstreamDiscoveryNs,
					},
				},
				Weight: 0,
			},
		},
	}

	upstreamGroup, err := gr.glooClient.GlooV1().UpstreamGroups(canary.Namespace).Get(context.TODO(), apexName, metav1.GetOptions{})
	if errors.IsNotFound(err) {
		upstreamGroup = &gloov1.UpstreamGroup{
			ObjectMeta: metav1.ObjectMeta{
				Name:      apexName,
				Namespace: canary.Namespace,
				OwnerReferences: []metav1.OwnerReference{
					*metav1.NewControllerRef(canary, schema.GroupVersionKind{
						Group:   flaggerv1.SchemeGroupVersion.Group,
						Version: flaggerv1.SchemeGroupVersion.Version,
						Kind:    flaggerv1.CanaryKind,
					}),
				},
			},
			Spec: newSpec,
		}

		_, err = gr.glooClient.GlooV1().UpstreamGroups(canary.Namespace).Create(context.TODO(), upstreamGroup, metav1.CreateOptions{})
		if err != nil {
			return fmt.Errorf("UpstreamGroup %s.%s create error: %w", apexName, canary.Namespace, err)
		}
		gr.logger.With("canary", fmt.Sprintf("%s.%s", canary.Name, canary.Namespace)).
			Infof("UpstreamGroup %s.%s created", upstreamGroup.GetName(), canary.Namespace)
		return nil
	} else if err != nil {
		return fmt.Errorf("UpstreamGroup %s.%s get query error: %w", apexName, canary.Namespace, err)
	}

	// update upstreamGroup but keep the original destination weights
	if upstreamGroup != nil {
		if diff := cmp.Diff(
			newSpec,
			upstreamGroup.Spec,
			cmpopts.IgnoreFields(gloov1.WeightedDestination{}, "Weight"),
		); diff != "" {
			clone := upstreamGroup.DeepCopy()
			clone.Spec = newSpec

			_, err = gr.glooClient.GlooV1().UpstreamGroups(canary.Namespace).Update(context.TODO(), clone, metav1.UpdateOptions{})
			if err != nil {
				return fmt.Errorf("UpstreamGroup %s.%s update error: %w", apexName, canary.Namespace, err)
			}
			gr.logger.With("canary", fmt.Sprintf("%s.%s", canary.Name, canary.Namespace)).
				Infof("UpstreamGroup %s.%s updated", upstreamGroup.GetName(), canary.Namespace)
		}
	}

	return nil
}

// GetRoutes returns the destinations weight for primary and canary
func (gr *GlooRouter) GetRoutes(canary *flaggerv1.Canary) (
	primaryWeight int,
	canaryWeight int,
	mirrored bool,
	err error,
) {
	apexName := canary.Spec.TargetRef.Name
	primaryName := fmt.Sprintf("%s-%s-primary-%v", canary.Namespace, canary.Spec.TargetRef.Name, canary.Spec.Service.Port)

	upstreamGroup, err := gr.glooClient.GlooV1().UpstreamGroups(canary.Namespace).Get(context.TODO(), apexName, metav1.GetOptions{})
	if err != nil {
		err = fmt.Errorf("UpstreamGroup %s.%s get query error: %w", apexName, canary.Namespace, err)
		return
	}

	if len(upstreamGroup.Spec.Destinations) < 2 {
		err = fmt.Errorf("UpstreamGroup %s.%s destinations not found", apexName, canary.Namespace)
		return
	}

	for _, dst := range upstreamGroup.Spec.Destinations {
		if dst.Destination.Upstream.Name == primaryName {
			primaryWeight = int(dst.Weight)
			canaryWeight = 100 - primaryWeight
			return
		}
	}

	return
}

// SetRoutes updates the destinations weight for primary and canary
func (gr *GlooRouter) SetRoutes(
	canary *flaggerv1.Canary,
	primaryWeight int,
	canaryWeight int,
	_ bool,
) error {
	apexName, _, _ := canary.GetServiceNames()
	canaryName := fmt.Sprintf("%s-%s-canary-%v", canary.Namespace, apexName, canary.Spec.Service.Port)
	primaryName := fmt.Sprintf("%s-%s-primary-%v", canary.Namespace, apexName, canary.Spec.Service.Port)

	if primaryWeight == 0 && canaryWeight == 0 {
		return fmt.Errorf("RoutingRule %s.%s update failed: no valid weights", apexName, canary.Namespace)
	}

	upstreamGroup, err := gr.glooClient.GlooV1().UpstreamGroups(canary.Namespace).Get(context.TODO(), apexName, metav1.GetOptions{})
	if err != nil {
		return fmt.Errorf("UpstreamGroup %s.%s query error: %w", apexName, canary.Namespace, err)
	}

	upstreamGroup.Spec = gloov1.UpstreamGroupSpec{
		Destinations: []gloov1.WeightedDestination{
			{
				Destination: gloov1.Destination{
					Upstream: gloov1.ResourceRef{
						Name:      primaryName,
						Namespace: gr.upstreamDiscoveryNs,
					},
				},
				Weight: uint32(primaryWeight),
			},
			{
				Destination: gloov1.Destination{
					Upstream: gloov1.ResourceRef{
						Name:      canaryName,
						Namespace: gr.upstreamDiscoveryNs,
					},
				},
				Weight: uint32(canaryWeight),
			},
		},
	}

	_, err = gr.glooClient.GlooV1().UpstreamGroups(canary.Namespace).Update(context.TODO(), upstreamGroup, metav1.UpdateOptions{})
	if err != nil {
		return fmt.Errorf("UpstreamGroup %s.%s update error: %w", apexName, canary.Namespace, err)
	}
	return nil
}

func (gr *GlooRouter) Finalize(_ *flaggerv1.Canary) error {
	return nil
}