package kubernetes

import (
	"strings"

	"github.com/coredns/coredns/plugin/etcd/msg"
	"github.com/coredns/coredns/plugin/kubernetes/object"
	"github.com/coredns/coredns/plugin/pkg/dnsutil"
	"github.com/coredns/coredns/request"

	"github.com/miekg/dns"
)

// External implements the ExternalFunc call from the external plugin.
// It returns any services matching in the services' ExternalIPs.
func (k *Kubernetes) External(state request.Request) ([]msg.Service, int) {
	if state.QType() == dns.TypePTR {
		ip := dnsutil.ExtractAddressFromReverse(state.Name())
		if ip != "" {
			svcs, err := k.ExternalReverse(ip)
			if err != nil {
				return nil, dns.RcodeNameError
			}
			return svcs, dns.RcodeSuccess
		}
		// for invalid reverse names, fall through to determine proper nxdomain/nodata response
	}

	base, _ := dnsutil.TrimZone(state.Name(), state.Zone)

	segs := dns.SplitDomainName(base)
	last := len(segs) - 1
	if last < 0 {
		return nil, dns.RcodeServerFailure
	}
	// We are dealing with a fairly normal domain name here, but we still need to have the service
	// and the namespace:
	// service.namespace.<base>
	var port, protocol string
	namespace := segs[last]
	if !k.namespaceExposed(namespace) {
		return nil, dns.RcodeNameError
	}

	last--
	if last < 0 {
		return nil, dns.RcodeSuccess
	}

	service := segs[last]
	last--
	if last == 1 {
		protocol = stripUnderscore(segs[last])
		port = stripUnderscore(segs[last-1])
		last -= 2
	}

	if last != -1 {
		// too long
		return nil, dns.RcodeNameError
	}

	idx := object.ServiceKey(service, namespace)
	serviceList := k.APIConn.SvcIndex(idx)

	services := []msg.Service{}
	zonePath := msg.Path(state.Zone, coredns)
	rcode := dns.RcodeNameError

	for _, svc := range serviceList {
		if namespace != svc.Namespace {
			continue
		}
		if service != svc.Name {
			continue
		}

		for _, ip := range svc.ExternalIPs {
			for _, p := range svc.Ports {
				if !(matchPortAndProtocol(port, p.Name, protocol, string(p.Protocol))) {
					continue
				}
				rcode = dns.RcodeSuccess
				s := msg.Service{Host: ip, Port: int(p.Port), TTL: k.ttl}
				s.Key = strings.Join([]string{zonePath, svc.Namespace, svc.Name}, "/")

				services = append(services, s)
			}
		}
	}
	if state.QType() == dns.TypePTR {
		// if this was a PTR request, return empty service list, but retain rcode for proper nxdomain/nodata response
		return nil, rcode
	}
	return services, rcode
}

// ExternalAddress returns the external service address(es) for the CoreDNS service.
func (k *Kubernetes) ExternalAddress(state request.Request) []dns.RR {
	// If CoreDNS is running inside the Kubernetes cluster: k.nsAddrs() will return the external IPs of the services
	// targeting the CoreDNS Pod.
	// If CoreDNS is running outside of the Kubernetes cluster: k.nsAddrs() will return the first non-loopback IP
	// address seen on the local system it is running on. This could be the wrong answer if coredns is using the *bind*
	// plugin to bind to a different IP address.
	return k.nsAddrs(true, state.Zone)
}

// ExternalServices returns all services with external IPs
func (k *Kubernetes) ExternalServices(zone string) (services []msg.Service) {
	zonePath := msg.Path(zone, coredns)
	for _, svc := range k.APIConn.ServiceList() {
		for _, ip := range svc.ExternalIPs {
			for _, p := range svc.Ports {
				s := msg.Service{Host: ip, Port: int(p.Port), TTL: k.ttl}
				s.Key = strings.Join([]string{zonePath, svc.Namespace, svc.Name}, "/")
				services = append(services, s)
				s.Key = strings.Join(append([]string{zonePath, svc.Namespace, svc.Name}, strings.ToLower("_"+string(p.Protocol)), strings.ToLower("_"+string(p.Name))), "/")
				s.TargetStrip = 2
				services = append(services, s)
			}
		}
	}
	return services
}

//ExternalSerial returns the serial of the external zone
func (k *Kubernetes) ExternalSerial(string) uint32 {
	return uint32(k.APIConn.Modified(true))
}

// ExternalReverse does a reverse lookup for the external IPs
func (k *Kubernetes) ExternalReverse(ip string) ([]msg.Service, error) {
	records := k.serviceRecordForExternalIP(ip)
	if len(records) == 0 {
		return records, errNoItems
	}
	return records, nil
}

func (k *Kubernetes) serviceRecordForExternalIP(ip string) []msg.Service {
	var svcs []msg.Service
	for _, service := range k.APIConn.SvcExtIndexReverse(ip) {
		if len(k.Namespaces) > 0 && !k.namespaceExposed(service.Namespace) {
			continue
		}
		domain := strings.Join([]string{service.Name, service.Namespace}, ".")
		svcs = append(svcs, msg.Service{Host: domain, TTL: k.ttl})
	}
	return svcs
}