package control

import (
	"context"
	"encoding/json"
	"errors"
	"time"

	kubecore "k8s.io/api/core/v1"
	k8inform "k8s.io/client-go/informers"
	k8client "k8s.io/client-go/kubernetes"
	k8cache "k8s.io/client-go/tools/cache"

	k8meta "k8s.io/apimachinery/pkg/apis/meta/v1"
	k8types "k8s.io/apimachinery/pkg/types"
	k8patch "k8s.io/apimachinery/pkg/util/strategicpatch"

	"helmet/app/logger"
)

type Proxy interface {
	CreateOrUpdateForwarder(ctx context.Context, proto string, lport, dport uint32, addrs ...string) error
	DeleteForwarder(ctx context.Context, proto string, lport uint32) error
}

type Dummyproxy struct {
	log *logger.Logger
}

func NewDummyproxy() Proxy {
	return &Dummyproxy{
		log: logger.NewLogger("dummyproxy"),
	}
}

func (prox *Dummyproxy) CreateOrUpdateForwarder(ctx context.Context, proto string, lport, dport uint32, addrs ...string) error {
	return nil
}
func (prox *Dummyproxy) DeleteForwarder(ctx context.Context, proto string, lport uint32) error {
	return nil
}

type Controller struct {
	lbaddr    string
	clientset k8client.Interface
	informer  k8cache.SharedIndexInformer
	ctx       context.Context
	cancel    context.CancelFunc
	log       *logger.Logger
	proxy     Proxy
}

func NewController(proxy Proxy, clientset k8client.Interface, lbaddr string) *Controller {
	ctx, cancel := context.WithCancel(context.Background())
	cont := &Controller{
		proxy:     proxy,
		clientset: clientset,
		ctx:       ctx,
		cancel:    cancel,
		lbaddr:    lbaddr,
	}
	cont.log = logger.NewLogger("controller")
	return cont
}

func (cont *Controller) ProbeAPI() bool {
	ctx, _ := context.WithTimeout(cont.ctx, 5*time.Second)
	opts := k8meta.ListOptions{
		Limit: 1,
	}
	_, err := cont.clientset.CoreV1().Services("").List(ctx, opts)
	if err != nil {
		cont.log.Errorf("Error connecting to API: %v", err)
		return false
	}
	return true
}

func (cont *Controller) Run() error {
	cont.log.Debugf("Start controller")
	factory := k8inform.NewSharedInformerFactory(cont.clientset, 10*time.Second)
	defer factory.Shutdown()

	serviceInformer := factory.Core().V1().Services().Informer()
	handler := k8cache.ResourceEventHandlerFuncs{
		AddFunc:    cont.addService,
		UpdateFunc: cont.updateService,
		DeleteFunc: cont.deleteService,
	}
	serviceInformer.AddEventHandler(handler)

	ctx, cancel := context.WithCancel(cont.ctx)
	defer cancel()
	factory.Start(ctx.Done())
	synced := factory.WaitForCacheSync(ctx.Done())
	for _, sync := range synced {
		if !sync {
			cont.log.Errorf("Cannot sync controller")
			err := errors.New("Cannot sync controller")
			return err
		}
	}
	cont.informer = serviceInformer
	<-ctx.Done()
	cont.log.Debugf("Stop controller")
	return nil
}

func (cont *Controller) Stop() {
	cont.cancel()
}

// https://pkg.go.dev/k8s.io/api/core/v1#Service

func (cont *Controller) addService(obj any) {
	service := obj.(*kubecore.Service)
	service = service.DeepCopy()
	if service.Spec.Type == kubecore.ServiceTypeLoadBalancer {
		cont.log.Infof("Service %s/%s created", service.Namespace, service.Name)
		forws := makeForwardings(service)
		cont.log.Debugf("Service %s/%s forwards: %++v", service.Namespace, service.Name, forws)

		for _, forw := range forws {
			err := cont.proxy.CreateOrUpdateForwarder(cont.ctx, forw.Proto, forw.Port, forw.Port, forw.Destinations...)
			if err != nil {
				cont.log.Errorf("Error forwarding service %s/%s: %v", service.Namespace, service.Name, err)
			}
		}
		cont.log.Debugf("Service %s/%s forwarded", service.Namespace, service.Name)
		err := cont.addStatus(service)
		if err != nil {
			cont.log.Debugf("Error patch service %s/%s: %v", service.Namespace, service.Name, err)
		}
		err = cont.addFinalizer(service)
		if err != nil {
			cont.log.Debugf("Error patch service %s/%s: %v", service.Namespace, service.Name, err)
		}
		cont.log.Debugf("Service %s/%s patched", service.Namespace, service.Name)
	}
}

func (cont *Controller) updateService(oldObj, newObj any) {
	newService := newObj.(*kubecore.Service)
	newService = newService.DeepCopy()
	oldService := oldObj.(*kubecore.Service)
	oldService = oldService.DeepCopy()
	if newService.Spec.Type == kubecore.ServiceTypeLoadBalancer {
		if cont.serviceDifferent(oldService, newService) {
			cont.log.Infof("Service %s/%s updated", newService.Namespace, newService.Name)
			forws := makeForwardings(newService)
			for _, forw := range forws {
				err := cont.proxy.CreateOrUpdateForwarder(cont.ctx, forw.Proto, forw.Port, forw.Port, forw.Destinations...)
				if err != nil {
					cont.log.Errorf("Error forwarding service %s/%s: %v", newService.Namespace, newService.Name, err)
					return
				}
			}
			err := cont.addStatus(newService)
			if err != nil {
				cont.log.Errorf("Error patch service %s/%s: %v", newService.Namespace, newService.Name, err)
			}
		}
	}
}

func (cont *Controller) deleteService(obj any) {
	service := obj.(*kubecore.Service)
	service = service.DeepCopy()
	if service.Spec.Type == kubecore.ServiceTypeLoadBalancer {
		cont.log.Debugf("Service %s/%s deleted", service.Namespace, service.Name)
		forws := makeForwardings(service)
		for _, forw := range forws {
			err := cont.proxy.DeleteForwarder(cont.ctx, forw.Proto, forw.Port)
			if err != nil {
				cont.log.Errorf("Error unforwarding service %s/%s: %v", service.Namespace, service.Name, err)
			}
		}
		err := cont.deleteFinalizer(service)
		if err != nil {
			cont.log.Debugf("Error patch service %s/%s: %v", service.Namespace, service.Name, err)
		}
		cont.log.Debugf("Service %s/%s unforwarded", service.Namespace, service.Name)
	}
}

type Forwarding struct {
	Proto        string
	Port         uint32
	Destinations []string
}

func makeForwardings(service *kubecore.Service) []*Forwarding {
	forwardings := make([]*Forwarding, 0)
	for _, port := range service.Spec.Ports {
		forwarding := &Forwarding{
			Proto:        string(port.Protocol),
			Port:         uint32(port.Port),
			Destinations: make([]string, 0),
		}
		for _, ipaddr := range service.Spec.ClusterIPs {
			forwarding.Destinations = append(forwarding.Destinations, ipaddr)
		}
		forwardings = append(forwardings, forwarding)
	}
	return forwardings
}

const LoadBalancerFinalizer = "service.kubernetes.io/load-balancer"

func (cont *Controller) addFinalizer(oldSvc *kubecore.Service) error {
	var err error
	for _, finalizer := range oldSvc.ObjectMeta.Finalizers {
		if finalizer == LoadBalancerFinalizer {
			return err
		}
	}
	newSvc := oldSvc.DeepCopy()
	newSvc.ObjectMeta.Finalizers = append(newSvc.ObjectMeta.Finalizers, LoadBalancerFinalizer)
	err = cont.patchService(oldSvc, newSvc)
	if err != nil {
		return err
	}
	return err
}

func (cont *Controller) deleteFinalizer(oldSvc *kubecore.Service) error {
	var err error
	haveFinalizer := false
	newFinalizers := make([]string, 0)
	for _, finalizer := range oldSvc.ObjectMeta.Finalizers {
		if finalizer == LoadBalancerFinalizer {
			haveFinalizer = true
		} else {
			newFinalizers = append(newFinalizers, finalizer)
		}
	}
	if !haveFinalizer {
		return err
	}
	newSvc := oldSvc.DeepCopy()
	newSvc.ObjectMeta.Finalizers = newFinalizers
	err = cont.patchService(oldSvc, newSvc)
	if err != nil {
		return err
	}
	return err
}

func (cont *Controller) addStatus(oldSvc *kubecore.Service) error {
	var err error
	newSvc := oldSvc.DeepCopy()
	ingressMode := kubecore.LoadBalancerIPModeProxy
	ingresses := make([]kubecore.LoadBalancerIngress, 0)
	ingresses = append(ingresses, kubecore.LoadBalancerIngress{
		IP:     cont.lbaddr,
		IPMode: &ingressMode,
	})
	status := kubecore.LoadBalancerStatus{
		Ingress: ingresses,
	}
	newSvc.Status.LoadBalancer = status
	err = cont.patchService(oldSvc, newSvc)
	if err != nil {
		return err
	}
	return err
}

func (cont *Controller) patchService(oldSvc, newSvc *kubecore.Service) error {
	var err error
	oldData, err := json.Marshal(oldSvc)
	if err != nil {
		return err
	}
	newData, err := json.Marshal(newSvc)
	if err != nil {
		return err
	}
	patchBytes, err := k8patch.CreateTwoWayMergePatch(oldData, newData, kubecore.Service{})
	if err != nil {
		return err
	}
	//cont.log.Debugf("patch: %s\n", string(patchBytes))

	ctx, _ := context.WithTimeout(cont.ctx, 5*time.Second)
	patchServiceOpts := k8meta.PatchOptions{}
	strategy := k8types.StrategicMergePatchType
	_, err = cont.clientset.CoreV1().Services(oldSvc.Namespace).
		Patch(ctx, oldSvc.Name, strategy, patchBytes, patchServiceOpts, "status")
	if err != nil {
		return err
	}
	return err
}

func (cont *Controller) serviceDifferent(oldService, newService *kubecore.Service) bool {
	type Address struct {
		Port    int32
		Proto   kubecore.Protocol
		Address string
	}
	oldAddreses := make([]Address, 0)
	for _, port := range oldService.Spec.Ports {
		for _, ipaddr := range oldService.Spec.ClusterIPs {
			address := Address{
				Port:    port.Port,
				Proto:   port.Protocol,
				Address: ipaddr,
			}
			oldAddreses = append(oldAddreses, address)
		}
	}
	newAddreses := make([]Address, 0)
	for _, port := range newService.Spec.Ports {
		for _, ipaddr := range newService.Spec.ClusterIPs {
			address := Address{
				Port:    port.Port,
				Proto:   port.Protocol,
				Address: ipaddr,
			}
			newAddreses = append(newAddreses, address)
		}
	}
	if len(newAddreses) != len(oldAddreses) {
		return true
	}
	for _, newAddress := range newAddreses {
		newFound := false
		for _, oldAddress := range oldAddreses {
			if oldAddress == newAddress {
				newFound = true
			}
		}
		if !newFound {
			return true
		}
	}
	for _, oldAddress := range oldAddreses {
		oldFound := false
		for _, newAddress := range newAddreses {
			if newAddress == oldAddress {
				oldFound = true
			}
		}
		if !oldFound {
			return true
		}
	}
	return false
}