package net

import (
	"internal/bytealg"
	"internal/stringslite"
	"net/netip"
	"time"
)

// See resolv.conf(5) on a Linux machine.
func dnsReadConfig(filename string) *dnsConfig {
	conf := &dnsConfig{
		ndots:    1,
		timeout:  5 * time.Second,
		attempts: 2,
	}
	file, err := open(filename)
	if err != nil {
		conf.servers = defaultNS
		conf.search = dnsDefaultSearch()
		conf.err = err

// The provided Resolver is optional. nil means to not consider its options.
// It also returns dnsConfig when it was used to determine the lookup order.
func (c *conf) addrLookupOrder(r *Resolver, addr string) (ret hostLookupOrder, dnsConf *dnsConfig) {
	if c.dnsDebugLevel > 1 {
		defer func() {
			print("go package net: addrLookupOrder(", addr, ") = ", ret.String(), "\n")
		}()
	}

	Priority                      *int32                                       `json:"priority,omitempty"`
	DNSConfig                     *PodDNSConfigApplyConfiguration              `json:"dnsConfig,omitempty"`
	ReadinessGates                []PodReadinessGateApplyConfiguration         `json:"readinessGates,omitempty"`

func newClient() (*dnsClient, error) {
	servers := NetworkGatewayTestDNSServers
	if len(servers) == 0 {
		dnsConfig, err := dns.ClientConfigFromFile("/etc/resolv.conf")
		if err != nil {
			return nil, err
		}
		if dnsConfig != nil {
			for _, s := range dnsConfig.Servers {
				servers = append(servers, net.JoinHostPort(s, dnsConfig.Port))
			}
		}
		// TODO take search namespaces into account
		// TODO what about /etc/hosts?

	if os.IsNotExist(err) {
		return false, nil
	}
	if err != nil {
		return false, err
	}

	return stat.Mode().IsRegular(), nil
}

func getHostDNSConfig(resolverConfig string) (*runtimeapi.DNSConfig, error) {
	if resolverConfig == "" {
		// This handles "" by returning defaults.
		return getDNSConfig(resolverConfig)
	}

	isFile, err := fileExists(resolverConfig)
	if err != nil {

	// traffic to port 53 will be captured.
	if c.RedirectDNS && !c.CaptureAllDNS {
		dnsConfig, err := dns.ClientConfigFromFile("/etc/resolv.conf")
		if err != nil {
			return fmt.Errorf("failed to load /etc/resolv.conf: %v", err)
		}
		c.DNSServersV4, c.DNSServersV6 = netutil.IPsSplitV4V6(dnsConfig.Servers)
	}
	return nil
}

// mock net.InterfaceAddrs to make its unit test become available
var (

	// name in our local nametable. If not, we will forward the query to the
	// upstream resolvers as is.
	if dnsConfig != nil {
		for _, s := range dnsConfig.Servers {
			h.resolvConfServers = append(h.resolvConfServers, net.JoinHostPort(s, dnsConfig.Port))
		}
		h.searchNamespaces = dnsConfig.Search
	}

	log.WithLabels("search", h.searchNamespaces, "servers", h.resolvConfServers).Debugf("initialized DNS")

}

// GetPodDNS returns DNS settings for the pod.
// This function is defined in kubecontainer.RuntimeHelper interface so we
// have to implement it.
func (kl *Kubelet) GetPodDNS(pod *v1.Pod) (*runtimeapi.DNSConfig, error) {
	return kl.dnsConfigurer.GetPodDNS(pod)

			Uid:       podUID,
			Attempt:   attempt,
		},
		Labels:      newPodLabels(pod),
		Annotations: newPodAnnotations(pod),
	}

	dnsConfig, err := m.runtimeHelper.GetPodDNS(pod)
	if err != nil {
		return nil, err
	}
	podSandboxConfig.DnsConfig = dnsConfig

	if !kubecontainer.IsHostNetworkPod(pod) {
		// TODO: Add domain support in new runtime interface

	GenerateRunContainerOptions(ctx context.Context, pod *v1.Pod, container *v1.Container, podIP string, podIPs []string) (contOpts *RunContainerOptions, cleanupAction func(), err error)
	GetPodDNS(pod *v1.Pod) (dnsConfig *runtimeapi.DNSConfig, err error)
	// GetPodCgroupParent returns the CgroupName identifier, and its literal cgroupfs form on the host
	// of a pod.
	GetPodCgroupParent(pod *v1.Pod) string
	GetPodDir(podUID types.UID) string