package crd

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"github.com/containous/traefik/v2/pkg/config/dynamic"
	"github.com/containous/traefik/v2/pkg/log"
	"github.com/containous/traefik/v2/pkg/provider/kubernetes/crd/traefik/v1alpha1"
	"github.com/containous/traefik/v2/pkg/tls"
	corev1 "k8s.io/api/core/v1"
)

func (p *Provider) loadIngressRouteConfiguration(ctx context.Context, client Client, tlsConfigs map[string]*tls.CertAndStores) *dynamic.HTTPConfiguration {
	conf := &dynamic.HTTPConfiguration{
		Routers:     map[string]*dynamic.Router{},
		Middlewares: map[string]*dynamic.Middleware{},
		Services:    map[string]*dynamic.Service{},
	}

	for _, ingressRoute := range client.GetIngressRoutes() {
		ctxRt := log.With(ctx, log.Str("ingress", ingressRoute.Name), log.Str("namespace", ingressRoute.Namespace))
		logger := log.FromContext(ctxRt)

		// TODO keep the name ingressClass?
		if !shouldProcessIngress(p.IngressClass, ingressRoute.Annotations[annotationKubernetesIngressClass]) {
			continue
		}

		err := getTLSHTTP(ctx, ingressRoute, client, tlsConfigs)
		if err != nil {
			logger.Errorf("Error configuring TLS: %v", err)
		}

		ingressName := ingressRoute.Name
		if len(ingressName) == 0 {
			ingressName = ingressRoute.GenerateName
		}

		for _, route := range ingressRoute.Spec.Routes {
			if route.Kind != "Rule" {
				logger.Errorf("Unsupported match kind: %s. Only \"Rule\" is supported for now.", route.Kind)
				continue
			}

			if len(route.Match) == 0 {
				logger.Errorf("Empty match rule")
				continue
			}

			if err := checkStringQuoteValidity(route.Match); err != nil {
				logger.Errorf("Invalid syntax for match rule: %s", route.Match)
				continue
			}

			key, err := makeServiceKey(route.Match, ingressName)
			if err != nil {
				logger.Error(err)
				continue
			}

			serviceName := makeID(ingressRoute.Namespace, key)

			for _, service := range route.Services {
				balancerServerHTTP, err := createLoadBalancerServerHTTP(client, ingressRoute.Namespace, service)
				if err != nil {
					logger.
						WithField("serviceName", service.Name).
						WithField("servicePort", service.Port).
						Errorf("Cannot create service: %v", err)
					continue
				}

				// If there is only one service defined, we skip the creation of the load balancer of services,
				// i.e. the service on top is directly a load balancer of servers.
				if len(route.Services) == 1 {
					conf.Services[serviceName] = balancerServerHTTP
					break
				}

				serviceKey := fmt.Sprintf("%s-%s-%d", serviceName, service.Name, service.Port)
				conf.Services[serviceKey] = balancerServerHTTP

				srv := dynamic.WRRService{Name: serviceKey}
				srv.SetDefaults()
				if service.Weight != nil {
					srv.Weight = service.Weight
				}

				if conf.Services[serviceName] == nil {
					conf.Services[serviceName] = &dynamic.Service{Weighted: &dynamic.WeightedRoundRobin{}}
				}
				conf.Services[serviceName].Weighted.Services = append(conf.Services[serviceName].Weighted.Services, srv)
			}

			var mds []string
			for _, mi := range route.Middlewares {
				if strings.Contains(mi.Name, "@") {
					if len(mi.Namespace) > 0 {
						logger.
							WithField(log.MiddlewareName, mi.Name).
							Warnf("namespace %q is ignored in cross-provider context", mi.Namespace)
					}
					mds = append(mds, mi.Name)
					continue
				}

				ns := mi.Namespace
				if len(ns) == 0 {
					ns = ingressRoute.Namespace
				}
				mds = append(mds, makeID(ns, mi.Name))
			}

			conf.Routers[serviceName] = &dynamic.Router{
				Middlewares: mds,
				Priority:    route.Priority,
				EntryPoints: ingressRoute.Spec.EntryPoints,
				Rule:        route.Match,
				Service:     serviceName,
			}

			if ingressRoute.Spec.TLS != nil {
				tlsConf := &dynamic.RouterTLSConfig{
					CertResolver: ingressRoute.Spec.TLS.CertResolver,
					Domains:      ingressRoute.Spec.TLS.Domains,
				}

				if ingressRoute.Spec.TLS.Options != nil && len(ingressRoute.Spec.TLS.Options.Name) > 0 {
					tlsOptionsName := ingressRoute.Spec.TLS.Options.Name
					// Is a Kubernetes CRD reference, (i.e. not a cross-provider reference)
					ns := ingressRoute.Spec.TLS.Options.Namespace
					if !strings.Contains(tlsOptionsName, "@") {
						if len(ns) == 0 {
							ns = ingressRoute.Namespace
						}
						tlsOptionsName = makeID(ns, tlsOptionsName)
					} else if len(ns) > 0 {
						logger.
							WithField("TLSoptions", ingressRoute.Spec.TLS.Options.Name).
							Warnf("namespace %q is ignored in cross-provider context", ns)
					}

					tlsConf.Options = tlsOptionsName
				}
				conf.Routers[serviceName].TLS = tlsConf
			}
		}
	}

	return conf
}

func createLoadBalancerServerHTTP(client Client, namespace string, service v1alpha1.Service) (*dynamic.Service, error) {
	servers, err := loadServers(client, namespace, service)
	if err != nil {
		return nil, err
	}

	// TODO: support other strategies.
	lb := &dynamic.ServersLoadBalancer{}
	lb.SetDefaults()

	lb.Servers = servers

	lb.PassHostHeader = service.PassHostHeader
	if lb.PassHostHeader == nil {
		passHostHeader := true
		lb.PassHostHeader = &passHostHeader
	}
	lb.ResponseForwarding = service.ResponseForwarding

	return &dynamic.Service{
		LoadBalancer: lb,
	}, nil
}

func loadServers(client Client, namespace string, svc v1alpha1.Service) ([]dynamic.Server, error) {
	strategy := svc.Strategy
	if strategy == "" {
		strategy = "RoundRobin"
	}
	if strategy != "RoundRobin" {
		return nil, fmt.Errorf("load balancing strategy %v is not supported", strategy)
	}

	service, exists, err := client.GetService(namespace, svc.Name)
	if err != nil {
		return nil, err
	}

	if !exists {
		return nil, fmt.Errorf("service not found %s/%s", namespace, svc.Name)
	}

	var portSpec *corev1.ServicePort
	for _, p := range service.Spec.Ports {
		if svc.Port == p.Port {
			portSpec = &p
			break
		}
	}

	if portSpec == nil {
		return nil, errors.New("service port not found")
	}

	var servers []dynamic.Server
	if service.Spec.Type == corev1.ServiceTypeExternalName {
		protocol := "http"
		if portSpec.Port == 443 || strings.HasPrefix(portSpec.Name, "https") {
			protocol = "https"
		}

		servers = append(servers, dynamic.Server{
			URL: fmt.Sprintf("%s://%s:%d", protocol, service.Spec.ExternalName, portSpec.Port),
		})
	} else {
		endpoints, endpointsExists, endpointsErr := client.GetEndpoints(namespace, svc.Name)
		if endpointsErr != nil {
			return nil, endpointsErr
		}

		if !endpointsExists {
			return nil, errors.New("endpoints not found")
		}

		if len(endpoints.Subsets) == 0 {
			return nil, errors.New("subset not found")
		}

		var port int32
		for _, subset := range endpoints.Subsets {
			for _, p := range subset.Ports {
				if portSpec.Name == p.Name {
					port = p.Port
					break
				}
			}

			if port == 0 {
				return nil, errors.New("cannot define a port")
			}

			protocol := "http"
			switch svc.Scheme {
			case "http", "https", "h2c":
				protocol = svc.Scheme
			case "":
				if portSpec.Port == 443 || strings.HasPrefix(portSpec.Name, "https") {
					protocol = "https"
				}
			default:
				return nil, fmt.Errorf("invalid scheme %q specified", svc.Scheme)
			}

			for _, addr := range subset.Addresses {
				servers = append(servers, dynamic.Server{
					URL: fmt.Sprintf("%s://%s:%d", protocol, addr.IP, port),
				})
			}
		}
	}

	return servers, nil
}

func getTLSHTTP(ctx context.Context, ingressRoute *v1alpha1.IngressRoute, k8sClient Client, tlsConfigs map[string]*tls.CertAndStores) error {
	if ingressRoute.Spec.TLS == nil {
		return nil
	}
	if ingressRoute.Spec.TLS.SecretName == "" {
		log.FromContext(ctx).Debugf("No secret name provided")
		return nil
	}

	configKey := ingressRoute.Namespace + "/" + ingressRoute.Spec.TLS.SecretName
	if _, tlsExists := tlsConfigs[configKey]; !tlsExists {
		tlsConf, err := getTLS(k8sClient, ingressRoute.Spec.TLS.SecretName, ingressRoute.Namespace)
		if err != nil {
			return err
		}

		tlsConfigs[configKey] = tlsConf
	}

	return nil
}