package kubernetes

import (
	"errors"
	"fmt"
	"log"
	"net"
	"strings"
	"time"

	"github.com/coredns/coredns/core/dnsserver"
	"github.com/coredns/coredns/middleware"
	"github.com/coredns/coredns/middleware/pkg/dnsutil"
	"github.com/coredns/coredns/middleware/proxy"
	"github.com/miekg/dns"

	"github.com/mholt/caddy"
	unversionedapi "k8s.io/client-go/1.5/pkg/api/unversioned"
)

func init() {
	caddy.RegisterPlugin("kubernetes", caddy.Plugin{
		ServerType: "dns",
		Action:     setup,
	})
}

func setup(c *caddy.Controller) error {
	kubernetes, err := kubernetesParse(c)
	if err != nil {
		return middleware.Error("kubernetes", err)
	}

	err = kubernetes.InitKubeCache()
	if err != nil {
		return middleware.Error("kubernetes", err)
	}

	// Register KubeCache start and stop functions with Caddy
	c.OnStartup(func() error {
		go kubernetes.APIConn.Run()
		if kubernetes.APIProxy != nil {
			go kubernetes.APIProxy.Run()
		}
		return nil
	})

	c.OnShutdown(func() error {
		if kubernetes.APIProxy != nil {
			kubernetes.APIProxy.Stop()
		}
		return kubernetes.APIConn.Stop()
	})

	dnsserver.GetConfig(c).AddMiddleware(func(next middleware.Handler) middleware.Handler {
		kubernetes.Next = next
		return kubernetes
	})

	// Also register kubernetes for use in autopath.
	dnsserver.GetConfig(c).RegisterHandler(kubernetes)

	return nil
}

func kubernetesParse(c *caddy.Controller) (*Kubernetes, error) {
	k8s := &Kubernetes{
		ResyncPeriod:       defaultResyncPeriod,
		interfaceAddrsFunc: localPodIP,
		PodMode:            PodModeDisabled,
		Proxy:              proxy.Proxy{},
	}

	k8s.autoPathSearch = searchFromResolvConf()

	for c.Next() {
		if c.Val() == "kubernetes" {
			zones := c.RemainingArgs()

			if len(zones) != 0 {
				k8s.Zones = zones
				middleware.Zones(k8s.Zones).Normalize()
			} else {
				k8s.Zones = make([]string, len(c.ServerBlockKeys))
				for i := 0; i < len(c.ServerBlockKeys); i++ {
					k8s.Zones[i] = middleware.Host(c.ServerBlockKeys[i]).Normalize()
				}
			}

			k8s.primaryZone = -1
			for i, z := range k8s.Zones {
				if strings.HasSuffix(z, "in-addr.arpa.") || strings.HasSuffix(z, "ip6.arpa.") {
					continue
				}
				k8s.primaryZone = i
				break
			}

			if k8s.primaryZone == -1 {
				return nil, errors.New("non-reverse zone name must be given for Kubernetes")
			}

			for c.NextBlock() {
				switch c.Val() {
				case "cidrs":

					// DEPRECATION WARNING
					log.Printf("[WARNING] \"cidrs\" will be removed for CoreDNS soon. See https://coredns.io/2017/07/23/corefile-explained#reverse-zones for the replacement")

					args := c.RemainingArgs()
					if len(args) > 0 {
						for _, cidrStr := range args {
							_, cidr, err := net.ParseCIDR(cidrStr)
							if err != nil {
								return nil, fmt.Errorf("invalid cidr: %s", cidrStr)
							}
							k8s.ReverseCidrs = append(k8s.ReverseCidrs, *cidr)

						}
						continue
					}
					return nil, c.ArgErr()
				case "pods":
					args := c.RemainingArgs()
					if len(args) == 1 {
						switch args[0] {
						case PodModeDisabled, PodModeInsecure, PodModeVerified:
							k8s.PodMode = args[0]
						default:
							return nil, fmt.Errorf("wrong value for pods: %s,  must be one of: disabled, verified, insecure", args[0])
						}
						continue
					}
					return nil, c.ArgErr()
				case "namespaces":
					args := c.RemainingArgs()
					if len(args) > 0 {
						k8s.Namespaces = append(k8s.Namespaces, args...)
						continue
					}
					return nil, c.ArgErr()
				case "endpoint":
					args := c.RemainingArgs()
					if len(args) > 0 {
						for _, endpoint := range strings.Split(args[0], ",") {
							k8s.APIServerList = append(k8s.APIServerList, strings.TrimSpace(endpoint))
						}
						continue
					}
					return nil, c.ArgErr()
				case "tls": // cert key cacertfile
					args := c.RemainingArgs()
					if len(args) == 3 {
						k8s.APIClientCert, k8s.APIClientKey, k8s.APICertAuth = args[0], args[1], args[2]
						continue
					}
					return nil, c.ArgErr()
				case "resyncperiod":
					args := c.RemainingArgs()
					if len(args) > 0 {
						rp, err := time.ParseDuration(args[0])
						if err != nil {
							return nil, fmt.Errorf("unable to parse resync duration value: '%v': %v", args[0], err)
						}
						k8s.ResyncPeriod = rp
						continue
					}
					return nil, c.ArgErr()
				case "labels":
					args := c.RemainingArgs()
					if len(args) > 0 {
						labelSelectorString := strings.Join(args, " ")
						ls, err := unversionedapi.ParseToLabelSelector(labelSelectorString)
						if err != nil {
							return nil, fmt.Errorf("unable to parse label selector value: '%v': %v", labelSelectorString, err)
						}
						k8s.LabelSelector = ls
						continue
					}
					return nil, c.ArgErr()
				case "fallthrough":
					args := c.RemainingArgs()
					if len(args) == 0 {
						k8s.Fallthrough = true
						continue
					}
					return nil, c.ArgErr()
				case "upstream":
					args := c.RemainingArgs()
					if len(args) == 0 {
						return nil, c.ArgErr()
					}
					ups, err := dnsutil.ParseHostPortOrFile(args...)
					if err != nil {
						return nil, err
					}
					k8s.Proxy = proxy.NewLookup(ups)
				case "federation": // name zone
					args := c.RemainingArgs()
					if len(args) == 2 {
						k8s.Federations = append(k8s.Federations, Federation{
							name: args[0],
							zone: args[1],
						})
						continue
					}
					return nil, fmt.Errorf("incorrect number of arguments for federation, got %v, expected 2", len(args))
				}
			}
			return k8s, nil
		}
	}
	return nil, errors.New("kubernetes setup called without keyword 'kubernetes' in Corefile")
}

func searchFromResolvConf() []string {
	rc, err := dns.ClientConfigFromFile("/etc/resolv.conf")
	if err != nil {
		return nil
	}
	middleware.Zones(rc.Search).Normalize()
	return rc.Search
}

const (
	defaultResyncPeriod = 5 * time.Minute
	defautNdots         = 0
	defaultOnNXDOMAIN   = dns.RcodeSuccess
)
