meshconfig "istio.io/api/mesh/v1alpha1"
	"istio.io/istio/pilot/pkg/model"
	dnsProto "istio.io/istio/pkg/dns/proto"
)

// ConfigGenerator represents the interfaces to be implemented by code that generates xDS responses
type ConfigGenerator interface {
	// BuildListeners returns the list of inbound/outbound listeners for the given proxy. This is the LDS output

		HTTP: echo.HTTP{
			Path: "/" + testName,
		},
	})
	if err != nil {
		return fmt.Errorf("failed to request to external service: %s", err)
	}
	if res.Responses[0].Code != "200" {
		return fmt.Errorf("expected to get 200 status code, got: %s", res.Responses[0].Code)
	}
	return nil
}

func verifyThatRequestWasTunneled(target echo.Instance, expectedSourceIPs []corev1.PodIP, expectedPath string) error {

	}
}

// sendDownstream sends discovery response.
func sendDownstream(downstream adsStream, response *discovery.DiscoveryResponse) error {
	tStart := time.Now()
	defer func() {
		// This is a hint to help debug slow responses.
		if time.Since(tStart) > 10*time.Second {
			proxyLog.Warnf("sendDownstream took %v", time.Since(tStart))
		}
	}()
	return downstream.Send(response)
}

func (p *XdsProxy) close() {

type EndpointFilter struct {
	Address string
	Port    uint32
	Cluster string
	Status  string
}

// ConfigWriter is a writer for processing responses from the Envoy Admin config_dump endpoint
type ConfigWriter struct {
	Stdout   io.Writer
	clusters *clusters.Wrapper
}

// EndpointCluster is used to store the endpoint and cluster
type EndpointCluster struct {

	// Check that each response saw one of the workload IPs for the src echo instance
	addresses := sets.New(src.WorkloadsOrFail(t).Addresses()...)
	return check.Each(func(response echot.Response) error {
		if !addresses.Contains(response.IP) {
			return fmt.Errorf("expected original source (%v) to be propogated, but got %v", addresses.UnsortedList(), response.IP)
		}
		return nil
	})
}

	if lp == nil {
		if h.respondBeforeSync {
			response = h.upstream(proxy, req, hostname)
			response.Truncate(size(proxy.protocol, req))
			_ = w.WriteMsg(response)
		} else {
			log.Debugf("dns request for host %q before lookup table is loaded", hostname)
			response = new(dns.Msg)
			response.SetReply(req)
			response.Rcode = dns.RcodeServerFailure
			_ = w.WriteMsg(response)
		}
		return
	}

				}
			}

			// Validate that we do send initial unhealthy endpoints.
			// ExpectPush=false since we are just querying the initial state, we already got the responses in our initial connection
			if sendUnhealthy {
				validateEndpoints(false, nil, []string{"10.0.0.53:53"})
			} else {
				validateEndpoints(false, nil, nil)
			}
			adscon.WaitClear()

	// Despite this code existing on the SotW code path, sending these partial pushes is still allowed;
	// see https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol#grouping-resources-into-responses
	if !req.Full || canSendPartialFullPushes(req) {
		edsUpdatedServices = model.ConfigNamesOfKind(req.ConfigsUpdated, kind.ServiceEntry)
	}
	var resources model.Resources
	empty := 0
	cached := 0

)

type XdsCacheImpl struct {
	cds typedXdsCache[uint64]
	eds typedXdsCache[uint64]
	rds typedXdsCache[uint64]
	sds typedXdsCache[string]
}

// XdsCache interface defines a store for caching XDS responses.
// All operations are thread safe.
type XdsCache interface {
	// Run starts a background thread to flush evicted indexes periodically.
	Run(stop <-chan struct{})

func size(cs int) {
	xdsCacheSize.Record(float64(cs))
}

type CacheToken uint64

type dependents interface {
	DependentConfigs() []ConfigHash
}

// typedXdsCache interface defines a store for caching XDS responses.
// All operations are thread safe.
type typedXdsCache[K comparable] interface {
	// Flush clears the evicted indexes.
	Flush()