package origin

import (
	"context"
	"crypto/tls"
	"fmt"
	"net"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/google/uuid"
	"github.com/pkg/errors"
	"github.com/prometheus/client_golang/prometheus"
	"golang.org/x/sync/errgroup"

	"github.com/cloudflare/cloudflared/buffer"
	"github.com/cloudflare/cloudflared/cmd/cloudflared/buildinfo"
	"github.com/cloudflare/cloudflared/cmd/cloudflared/ui"
	"github.com/cloudflare/cloudflared/connection"
	"github.com/cloudflare/cloudflared/h2mux"
	"github.com/cloudflare/cloudflared/ingress"
	"github.com/cloudflare/cloudflared/logger"
	"github.com/cloudflare/cloudflared/signal"
	"github.com/cloudflare/cloudflared/tunnelrpc"
	"github.com/cloudflare/cloudflared/tunnelrpc/pogs"
	tunnelpogs "github.com/cloudflare/cloudflared/tunnelrpc/pogs"
	"github.com/cloudflare/cloudflared/websocket"
)

const (
	dialTimeout              = 15 * time.Second
	openStreamTimeout        = 30 * time.Second
	muxerTimeout             = 5 * time.Second
	lbProbeUserAgentPrefix   = "Mozilla/5.0 (compatible; Cloudflare-Traffic-Manager/1.0; +https://www.cloudflare.com/traffic-manager/;"
	TagHeaderNamePrefix      = "Cf-Warp-Tag-"
	DuplicateConnectionError = "EDUPCONN"
	FeatureSerializedHeaders = "serialized_headers"
	FeatureQuickReconnects   = "quick_reconnects"
)

type rpcName string

const (
	register     rpcName = "register"
	reconnect    rpcName = "reconnect"
	unregister   rpcName = "unregister"
	authenticate rpcName = " authenticate"
)

type TunnelConfig struct {
	BuildInfo          *buildinfo.BuildInfo
	ClientID           string
	CloseConnOnce      *sync.Once // Used to close connectedSignal no more than once
	CompressionQuality uint64
	EdgeAddrs          []string
	GracePeriod        time.Duration
	HAConnections      int
	HeartbeatInterval  time.Duration
	Hostname           string
	IncidentLookup     IncidentLookup
	IsAutoupdated      bool
	IsFreeTunnel       bool
	LBPool             string
	Logger             logger.Service
	TransportLogger    logger.Service
	MaxHeartbeats      uint64
	Metrics            *TunnelMetrics
	MetricsUpdateFreq  time.Duration
	OriginCert         []byte
	ReportedVersion    string
	Retries            uint
	RunFromTerminal    bool
	Tags               []tunnelpogs.Tag
	TlsConfig          *tls.Config
	WSGI               bool

	// feature-flag to use new edge reconnect tokens
	UseReconnectToken bool

	NamedTunnel     *NamedTunnelConfig
	ReplaceExisting bool
	TunnelEventChan chan<- ui.TunnelEvent
	IngressRules    ingress.Ingress
}

type dupConnRegisterTunnelError struct{}

var errDuplicationConnection = &dupConnRegisterTunnelError{}

func (e dupConnRegisterTunnelError) Error() string {
	return "already connected to this server, trying another address"
}

type muxerShutdownError struct{}

func (e muxerShutdownError) Error() string {
	return "muxer shutdown"
}

// RegisterTunnel error from server
type serverRegisterTunnelError struct {
	cause     error
	permanent bool
}

func (e serverRegisterTunnelError) Error() string {
	return e.cause.Error()
}

// RegisterTunnel error from client
type clientRegisterTunnelError struct {
	cause error
}

func newRPCError(cause error, counter *prometheus.CounterVec, name rpcName) clientRegisterTunnelError {
	counter.WithLabelValues(cause.Error(), string(name)).Inc()
	return clientRegisterTunnelError{cause: cause}
}

func (e clientRegisterTunnelError) Error() string {
	return e.cause.Error()
}

func (c *TunnelConfig) muxerConfig(handler h2mux.MuxedStreamHandler) h2mux.MuxerConfig {
	return h2mux.MuxerConfig{
		Timeout:            muxerTimeout,
		Handler:            handler,
		IsClient:           true,
		HeartbeatInterval:  c.HeartbeatInterval,
		MaxHeartbeats:      c.MaxHeartbeats,
		Logger:             c.TransportLogger,
		CompressionQuality: h2mux.CompressionSetting(c.CompressionQuality),
	}
}

func (c *TunnelConfig) RegistrationOptions(connectionID uint8, OriginLocalIP string, uuid uuid.UUID) *tunnelpogs.RegistrationOptions {
	policy := tunnelrpc.ExistingTunnelPolicy_balance
	if c.HAConnections <= 1 && c.LBPool == "" {
		policy = tunnelrpc.ExistingTunnelPolicy_disconnect
	}
	return &tunnelpogs.RegistrationOptions{
		ClientID:             c.ClientID,
		Version:              c.ReportedVersion,
		OS:                   fmt.Sprintf("%s_%s", c.BuildInfo.GoOS, c.BuildInfo.GoArch),
		ExistingTunnelPolicy: policy,
		PoolName:             c.LBPool,
		Tags:                 c.Tags,
		ConnectionID:         connectionID,
		OriginLocalIP:        OriginLocalIP,
		IsAutoupdated:        c.IsAutoupdated,
		RunFromTerminal:      c.RunFromTerminal,
		CompressionQuality:   c.CompressionQuality,
		UUID:                 uuid.String(),
		Features:             c.SupportedFeatures(),
	}
}

func (c *TunnelConfig) ConnectionOptions(originLocalAddr string, numPreviousAttempts uint8) *tunnelpogs.ConnectionOptions {
	// attempt to parse out origin IP, but don't fail since it's informational field
	host, _, _ := net.SplitHostPort(originLocalAddr)
	originIP := net.ParseIP(host)

	return &tunnelpogs.ConnectionOptions{
		Client:              c.NamedTunnel.Client,
		OriginLocalIP:       originIP,
		ReplaceExisting:     c.ReplaceExisting,
		CompressionQuality:  uint8(c.CompressionQuality),
		NumPreviousAttempts: numPreviousAttempts,
	}
}

func (c *TunnelConfig) SupportedFeatures() []string {
	features := []string{FeatureSerializedHeaders}
	if c.NamedTunnel == nil {
		features = append(features, FeatureQuickReconnects)
	}
	return features
}

func (c *TunnelConfig) IsTrialTunnel() bool {
	return c.Hostname == ""
}

type NamedTunnelConfig struct {
	Auth     pogs.TunnelAuth
	ID       uuid.UUID
	Client   pogs.ClientInfo
	Protocol Protocol
}

type Protocol int64

const (
	h2muxProtocol Protocol = iota
	http2Protocol
)

func ParseProtocol(s string) (Protocol, bool) {
	switch s {
	case "h2mux":
		return h2muxProtocol, true
	case "http2":
		return http2Protocol, true
	default:
		return 0, false
	}
}

func StartTunnelDaemon(ctx context.Context, config *TunnelConfig, connectedSignal *signal.Signal, cloudflaredID uuid.UUID, reconnectCh chan ReconnectSignal) error {
	s, err := NewSupervisor(config, cloudflaredID)
	if err != nil {
		return err
	}
	return s.Run(ctx, connectedSignal, reconnectCh)
}

func ServeTunnelLoop(ctx context.Context,
	credentialManager *reconnectCredentialManager,
	config *TunnelConfig,
	addr *net.TCPAddr,
	connectionIndex uint8,
	connectedSignal *signal.Signal,
	cloudflaredUUID uuid.UUID,
	bufferPool *buffer.Pool,
	reconnectCh chan ReconnectSignal,
) error {
	config.Metrics.incrementHaConnections()
	defer config.Metrics.decrementHaConnections()
	backoff := BackoffHandler{MaxRetries: config.Retries}
	connectedFuse := h2mux.NewBooleanFuse()
	go func() {
		if connectedFuse.Await() {
			connectedSignal.Notify()
		}
	}()
	// Ensure the above goroutine will terminate if we return without connecting
	defer connectedFuse.Fuse(false)
	for {
		err, recoverable := ServeTunnel(
			ctx,
			credentialManager,
			config,
			config.Logger,
			addr, connectionIndex,
			connectedFuse,
			&backoff,
			cloudflaredUUID,
			bufferPool,
			reconnectCh,
		)
		if recoverable {
			if duration, ok := backoff.GetBackoffDuration(ctx); ok {
				if config.TunnelEventChan != nil {
					config.TunnelEventChan <- ui.TunnelEvent{Index: connectionIndex, EventType: ui.Reconnecting}
				}
				config.Logger.Infof("Retrying connection %d in %s seconds", connectionIndex, duration)
				backoff.Backoff(ctx)
				continue
			}
		}
		return err
	}
}

func ServeTunnel(
	ctx context.Context,
	credentialManager *reconnectCredentialManager,
	config *TunnelConfig,
	logger logger.Service,
	addr *net.TCPAddr,
	connectionIndex uint8,
	connectedFuse *h2mux.BooleanFuse,
	backoff *BackoffHandler,
	cloudflaredUUID uuid.UUID,
	bufferPool *buffer.Pool,
	reconnectCh chan ReconnectSignal,
) (err error, recoverable bool) {
	// Treat panics as recoverable errors
	defer func() {
		if r := recover(); r != nil {
			var ok bool
			err, ok = r.(error)
			if !ok {
				err = fmt.Errorf("ServeTunnel: %v", r)
			}
			recoverable = true
		}
	}()

	// If launch-ui flag is set, send disconnect msg
	if config.TunnelEventChan != nil {
		defer func() {
			config.TunnelEventChan <- ui.TunnelEvent{Index: connectionIndex, EventType: ui.Disconnected}
		}()
	}

	connectionTag := uint8ToString(connectionIndex)

	if config.NamedTunnel != nil && config.NamedTunnel.Protocol == http2Protocol {
		return ServeNamedTunnel(ctx, config, connectionIndex, addr, connectedFuse, reconnectCh)
	}

	// Returns error from parsing the origin URL or handshake errors
	handler, originLocalAddr, err := NewTunnelHandler(ctx, config, addr, connectionIndex, bufferPool)
	if err != nil {
		switch err.(type) {
		case connection.DialError:
			logger.Errorf("Connection %d unable to dial edge: %s", connectionIndex, err)
		case h2mux.MuxerHandshakeError:
			logger.Errorf("Connection %d handshake with edge server failed: %s", connectionIndex, err)
		default:
			logger.Errorf("Connection %d failed: %s", connectionIndex, err)
			return err, false
		}
		return err, true
	}

	errGroup, serveCtx := errgroup.WithContext(ctx)

	errGroup.Go(func() (err error) {
		defer func() {
			if err == nil {
				connectedFuse.Fuse(true)
				backoff.SetGracePeriod()
			}
		}()

		if config.UseReconnectToken && connectedFuse.Value() {
			err := ReconnectTunnel(serveCtx, handler.muxer, config, logger, connectionIndex, originLocalAddr, cloudflaredUUID, credentialManager)
			if err == nil {
				return nil
			}
			// log errors and proceed to RegisterTunnel
			logger.Errorf("Couldn't reconnect connection %d. Reregistering it instead. Error was: %v", connectionIndex, err)
		}
		return RegisterTunnel(serveCtx, credentialManager, handler.muxer, config, logger, connectionIndex, originLocalAddr, cloudflaredUUID)
	})

	errGroup.Go(func() error {
		updateMetricsTickC := time.Tick(config.MetricsUpdateFreq)
		for {
			select {
			case <-serveCtx.Done():
				// UnregisterTunnel blocks until the RPC call returns
				if connectedFuse.Value() {
					if config.NamedTunnel != nil {
						_ = UnregisterConnection(ctx, handler.muxer, config)
					} else {
						_ = UnregisterTunnel(handler.muxer, config)
					}
				}
				handler.muxer.Shutdown()
				return nil
			case <-updateMetricsTickC:
				handler.UpdateMetrics(connectionTag)
			}
		}
	})

	errGroup.Go(func() error {
		for {
			select {
			case reconnect := <-reconnectCh:
				return &reconnect
			case <-serveCtx.Done():
				return nil
			}
		}
	})

	errGroup.Go(func() error {
		// All routines should stop when muxer finish serving. When muxer is shutdown
		// gracefully, it doesn't return an error, so we need to return errMuxerShutdown
		// here to notify other routines to stop
		err := handler.muxer.Serve(serveCtx)
		if err == nil {
			return muxerShutdownError{}
		}
		return err
	})

	err = errGroup.Wait()
	if err != nil {
		switch err := err.(type) {
		case *dupConnRegisterTunnelError:
			// don't retry this connection anymore, let supervisor pick new a address
			return err, false
		case *serverRegisterTunnelError:
			logger.Errorf("Register tunnel error from server side: %s", err.cause)
			// Don't send registration error return from server to Sentry. They are
			// logged on server side
			if incidents := config.IncidentLookup.ActiveIncidents(); len(incidents) > 0 {
				logger.Error(activeIncidentsMsg(incidents))
			}
			return err.cause, !err.permanent
		case *clientRegisterTunnelError:
			logger.Errorf("Register tunnel error on client side: %s", err.cause)
			return err, true
		case *muxerShutdownError:
			logger.Info("Muxer shutdown")
			return err, true
		case *ReconnectSignal:
			logger.Infof("Restarting connection %d due to reconnect signal in %d seconds", connectionIndex, err.Delay)
			err.DelayBeforeReconnect()
			return err, true
		default:
			if err == context.Canceled {
				logger.Debugf("Serve tunnel error: %s", err)
				return err, false
			}
			logger.Errorf("Serve tunnel error: %s", err)
			return err, true
		}
	}
	return nil, true
}

func RegisterConnectionWithH2Mux(
	ctx context.Context,
	muxer *h2mux.Muxer,
	config *TunnelConfig,
	connectionIndex uint8,
	originLocalAddr string,
	numPreviousAttempts uint8,
) error {
	const registerConnection = "registerConnection"

	config.TransportLogger.Debug("initiating RPC stream for RegisterConnection")
	rpcClient, err := newTunnelRPCClient(ctx, muxer, config, registerConnection)
	if err != nil {
		return err
	}
	defer rpcClient.Close()

	conn, err := rpcClient.RegisterConnection(
		ctx,
		config.NamedTunnel.Auth,
		config.NamedTunnel.ID,
		connectionIndex,
		config.ConnectionOptions(originLocalAddr, numPreviousAttempts),
	)
	if err != nil {
		if err.Error() == DuplicateConnectionError {
			config.Metrics.regFail.WithLabelValues("dup_edge_conn", registerConnection).Inc()
			return errDuplicationConnection
		}
		config.Metrics.regFail.WithLabelValues("server_error", registerConnection).Inc()
		return serverRegistrationErrorFromRPC(err)
	}

	config.Metrics.regSuccess.WithLabelValues(registerConnection).Inc()
	config.Logger.Infof("Connection %d registered with %s using ID %s", connectionIndex, conn.Location, conn.UUID)

	// If launch-ui flag is set, send connect msg
	if config.TunnelEventChan != nil {
		config.TunnelEventChan <- ui.TunnelEvent{Index: connectionIndex, EventType: ui.Connected, Location: conn.Location}
	}

	return nil
}

func ServeNamedTunnel(
	ctx context.Context,
	config *TunnelConfig,
	connIndex uint8,
	addr *net.TCPAddr,
	connectedFuse *h2mux.BooleanFuse,
	reconnectCh chan ReconnectSignal,
) (err error, recoverable bool) {
	tlsServerConn, err := connection.DialEdge(ctx, dialTimeout, config.TlsConfig, addr)
	if err != nil {
		return err, true
	}

	cfdServer, err := newHTTP2Server(config, connIndex, tlsServerConn.LocalAddr(), connectedFuse)
	if err != nil {
		return err, false
	}

	errGroup, serveCtx := errgroup.WithContext(ctx)
	errGroup.Go(func() error {
		cfdServer.serve(serveCtx, tlsServerConn)
		return fmt.Errorf("Connection with edge closed")
	})

	errGroup.Go(func() error {
		select {
		case reconnect := <-reconnectCh:
			return &reconnect
		case <-serveCtx.Done():
			return nil
		}
	})

	err = errGroup.Wait()
	if err != nil {
		return err, true
	}
	return nil, false
}

func serverRegistrationErrorFromRPC(err error) *serverRegisterTunnelError {
	if retryable, ok := err.(*tunnelpogs.RetryableError); ok {
		return &serverRegisterTunnelError{
			cause:     retryable.Unwrap(),
			permanent: false,
		}
	}
	return &serverRegisterTunnelError{
		cause:     err,
		permanent: true,
	}
}

func UnregisterConnection(
	ctx context.Context,
	muxer *h2mux.Muxer,
	config *TunnelConfig,
) error {
	config.TransportLogger.Debug("initiating RPC stream for UnregisterConnection")
	rpcClient, err := newTunnelRPCClient(ctx, muxer, config, register)
	if err != nil {
		// RPC stream open error
		return err
	}
	defer rpcClient.Close()

	return rpcClient.UnregisterConnection(ctx)
}

func RegisterTunnel(
	ctx context.Context,
	credentialManager *reconnectCredentialManager,
	muxer *h2mux.Muxer,
	config *TunnelConfig,
	logger logger.Service,
	connectionID uint8,
	originLocalIP string,
	uuid uuid.UUID,
) error {
	config.TransportLogger.Debug("initiating RPC stream to register")
	if config.TunnelEventChan != nil {
		config.TunnelEventChan <- ui.TunnelEvent{EventType: ui.RegisteringTunnel}
	}

	rpcClient, err := newTunnelRPCClient(ctx, muxer, config, register)
	if err != nil {
		return err
	}
	defer rpcClient.Close()
	// Request server info without blocking tunnel registration; must use capnp library directly.
	serverInfoPromise := tunnelrpc.TunnelServer{Client: rpcClient.Client}.GetServerInfo(ctx, func(tunnelrpc.TunnelServer_getServerInfo_Params) error {
		return nil
	})
	LogServerInfo(serverInfoPromise.Result(), connectionID, config.Metrics, logger, config.TunnelEventChan)
	registration := rpcClient.RegisterTunnel(
		ctx,
		config.OriginCert,
		config.Hostname,
		config.RegistrationOptions(connectionID, originLocalIP, uuid),
	)
	if registrationErr := registration.DeserializeError(); registrationErr != nil {
		// RegisterTunnel RPC failure
		return processRegisterTunnelError(registrationErr, config.Metrics, register)
	}

	// Send free tunnel URL to UI
	if config.TunnelEventChan != nil {
		config.TunnelEventChan <- ui.TunnelEvent{EventType: ui.SetUrl, Url: registration.Url}
	}
	credentialManager.SetEventDigest(connectionID, registration.EventDigest)
	return processRegistrationSuccess(config, logger, connectionID, registration, register, credentialManager)
}

func processRegistrationSuccess(
	config *TunnelConfig,
	logger logger.Service,
	connectionID uint8,
	registration *tunnelpogs.TunnelRegistration,
	name rpcName,
	credentialManager *reconnectCredentialManager,
) error {
	for _, logLine := range registration.LogLines {
		logger.Info(logLine)
	}

	if registration.TunnelID != "" {
		config.Metrics.tunnelsHA.AddTunnelID(connectionID, registration.TunnelID)
		logger.Infof("Each HA connection's tunnel IDs: %v", config.Metrics.tunnelsHA.String())
	}

	// Print out the user's trial zone URL in a nice box (if they requested and got one and UI flag is not set)
	if config.TunnelEventChan == nil {
		if config.IsTrialTunnel() {
			if registrationURL, err := url.Parse(registration.Url); err == nil {
				for _, line := range asciiBox(trialZoneMsg(registrationURL.String()), 2) {
					logger.Info(line)
				}
			} else {
				logger.Error("Failed to connect tunnel, please try again.")
				return fmt.Errorf("empty URL in response from Cloudflare edge")
			}
		}
	}

	credentialManager.SetConnDigest(connectionID, registration.ConnDigest)
	config.Metrics.userHostnamesCounts.WithLabelValues(registration.Url).Inc()

	logger.Infof("Route propagating, it may take up to 1 minute for your new route to become functional")
	config.Metrics.regSuccess.WithLabelValues(string(name)).Inc()
	return nil
}

func processRegisterTunnelError(err tunnelpogs.TunnelRegistrationError, metrics *TunnelMetrics, name rpcName) error {
	if err.Error() == DuplicateConnectionError {
		metrics.regFail.WithLabelValues("dup_edge_conn", string(name)).Inc()
		return errDuplicationConnection
	}
	metrics.regFail.WithLabelValues("server_error", string(name)).Inc()
	return serverRegisterTunnelError{
		cause:     err,
		permanent: err.IsPermanent(),
	}
}

func UnregisterTunnel(muxer *h2mux.Muxer, config *TunnelConfig) error {
	config.TransportLogger.Debug("initiating RPC stream to unregister")
	ctx := context.Background()
	rpcClient, err := newTunnelRPCClient(ctx, muxer, config, unregister)
	if err != nil {
		// RPC stream open error
		return err
	}
	defer rpcClient.Close()

	// gracePeriod is encoded in int64 using capnproto
	return rpcClient.UnregisterTunnel(ctx, config.GracePeriod.Nanoseconds())
}

func LogServerInfo(
	promise tunnelrpc.ServerInfo_Promise,
	connectionID uint8,
	metrics *TunnelMetrics,
	logger logger.Service,
	tunnelEventChan chan<- ui.TunnelEvent,
) {
	serverInfoMessage, err := promise.Struct()
	if err != nil {
		logger.Errorf("Failed to retrieve server information: %s", err)
		return
	}
	serverInfo, err := tunnelpogs.UnmarshalServerInfo(serverInfoMessage)
	if err != nil {
		logger.Errorf("Failed to retrieve server information: %s", err)
		return
	}
	// If launch-ui flag is set, send connect msg
	if tunnelEventChan != nil {
		tunnelEventChan <- ui.TunnelEvent{Index: connectionID, EventType: ui.Connected, Location: serverInfo.LocationName}
	}
	logger.Infof("Connected to %s", serverInfo.LocationName)
	metrics.registerServerLocation(uint8ToString(connectionID), serverInfo.LocationName)
}

func serveWebsocket(wsResp WebsocketResp, req *http.Request, rule *ingress.Rule) (*http.Response, error) {
	if hostHeader := rule.Config.HTTPHostHeader; hostHeader != "" {
		req.Header.Set("Host", hostHeader)
		req.Host = hostHeader
	}

	dialler, ok := rule.Service.(websocket.Dialler)
	if !ok {
		return nil, fmt.Errorf("Websockets aren't supported by the origin service '%s'", rule.Service)
	}
	conn, response, err := websocket.ClientConnect(req, dialler)
	if err != nil {
		return nil, err
	}
	defer conn.Close()
	err = wsResp.WriteRespHeaders(response)
	if err != nil {
		return nil, errors.Wrap(err, "Error writing response header")
	}
	// Copy to/from stream to the undelying connection. Use the underlying
	// connection because cloudflared doesn't operate on the message themselves
	websocket.Stream(conn.UnderlyingConn(), wsResp)

	return response, nil
}

func uint8ToString(input uint8) string {
	return strconv.FormatUint(uint64(input), 10)
}

// Print out the given lines in a nice ASCII box.
func asciiBox(lines []string, padding int) (box []string) {
	maxLen := maxLen(lines)
	spacer := strings.Repeat(" ", padding)

	border := "+" + strings.Repeat("-", maxLen+(padding*2)) + "+"

	box = append(box, border)
	for _, line := range lines {
		box = append(box, "|"+spacer+line+strings.Repeat(" ", maxLen-len(line))+spacer+"|")
	}
	box = append(box, border)
	return
}

func maxLen(lines []string) int {
	max := 0
	for _, line := range lines {
		if len(line) > max {
			max = len(line)
		}
	}
	return max
}

func trialZoneMsg(url string) []string {
	return []string{
		"Your free tunnel has started! Visit it:",
		"  " + url,
	}
}

func activeIncidentsMsg(incidents []Incident) string {
	preamble := "There is an active Cloudflare incident that may be related:"
	if len(incidents) > 1 {
		preamble = "There are active Cloudflare incidents that may be related:"
	}
	incidentStrings := []string{}
	for _, incident := range incidents {
		incidentString := fmt.Sprintf("%s (%s)", incident.Name, incident.URL())
		incidentStrings = append(incidentStrings, incidentString)
	}
	return preamble + " " + strings.Join(incidentStrings, "; ")

}

func findCfRayHeader(h1 *http.Request) string {
	return h1.Header.Get("Cf-Ray")
}

func isLBProbeRequest(req *http.Request) bool {
	return strings.HasPrefix(req.UserAgent(), lbProbeUserAgentPrefix)
}

func newTunnelRPCClient(ctx context.Context, muxer *h2mux.Muxer, config *TunnelConfig, rpcName rpcName) (tunnelpogs.TunnelServer_PogsClient, error) {
	openStreamCtx, openStreamCancel := context.WithTimeout(ctx, openStreamTimeout)
	defer openStreamCancel()
	stream, err := muxer.OpenRPCStream(openStreamCtx)
	if err != nil {
		return tunnelpogs.TunnelServer_PogsClient{}, err
	}
	rpcClient, err := connection.NewTunnelRPCClient(ctx, stream, config.TransportLogger)
	if err != nil {
		// RPC stream open error
		return tunnelpogs.TunnelServer_PogsClient{}, newRPCError(err, config.Metrics.rpcFail, rpcName)
	}
	return rpcClient, nil
}