package http

import (
	"bufio"
	"compress/gzip"
	"container/list"
	"context"
	"crypto/tls"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"net/http/httptrace"
	"net/textproto"
	"net/url"
	"os"
	"reflect"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"golang.org/x/net/http/httpguts"
	"golang.org/x/net/http/httpproxy"
)

var DefaultTransport RoundTripper = &Transport{
	Proxy: ProxyFromEnvironment,
	DialContext: (&net.Dialer{
		Timeout:   30 * time.Second,
		KeepAlive: 30 * time.Second,
	}).DialContext,
	ForceAttemptHTTP2:     true,
	MaxIdleConns:          100,
	IdleConnTimeout:       90 * time.Second,
	TLSHandshakeTimeout:   10 * time.Second,
	ExpectContinueTimeout: 1 * time.Second,
}

const DefaultMaxIdleConnsPerHost = 2

type Transport struct {
	idleMu       sync.Mutex
	closeIdle    bool                                // user has requested to close all idle conns
	idleConn     map[connectMethodKey][]*persistConn // most recently used at end
	idleConnWait map[connectMethodKey]wantConnQueue  // waiting getConns
	idleLRU      connLRU

	reqMu       sync.Mutex
	reqCanceler map[cancelKey]func(error)

	altMu    sync.Mutex   // guards changing altProto only
	altProto atomic.Value // of nil or map[string]RoundTripper, key is URI scheme

	connsPerHostMu   sync.Mutex
	connsPerHost     map[connectMethodKey]int
	connsPerHostWait map[connectMethodKey]wantConnQueue // waiting getConns

	Proxy func(*Request) (*url.URL, error)

	DialContext func(ctx context.Context, network, addr string) (net.Conn, error)

	Dial func(network, addr string) (net.Conn, error)

	DialTLSContext func(ctx context.Context, network, addr string) (net.Conn, error)

	DialTLS func(network, addr string) (net.Conn, error)

	TLSClientConfig *tls.Config

	TLSHandshakeTimeout time.Duration

	DisableKeepAlives bool

	DisableCompression bool

	MaxIdleConns int

	MaxIdleConnsPerHost int

	MaxConnsPerHost int

	IdleConnTimeout time.Duration

	ResponseHeaderTimeout time.Duration

	ExpectContinueTimeout time.Duration

	TLSNextProto map[string]func(authority string, c *tls.Conn) RoundTripper

	ProxyConnectHeader Header

	GetProxyConnectHeader func(ctx context.Context, proxyURL *url.URL, target string) (Header, error)

	MaxResponseHeaderBytes int64

	WriteBufferSize int

	ReadBufferSize int

	nextProtoOnce      sync.Once
	h2transport        h2Transport // non-nil if http2 wired up
	tlsNextProtoWasNil bool        // whether TLSNextProto was nil when the Once fired

	ForceAttemptHTTP2 bool
}

type cancelKey struct {
	req *Request
}

func (t *Transport) writeBufferSize() int {
	if t.WriteBufferSize > 0 {
		return t.WriteBufferSize
	}
	return 4 << 10
}

func (t *Transport) readBufferSize() int {
	if t.ReadBufferSize > 0 {
		return t.ReadBufferSize
	}
	return 4 << 10
}

func (t *Transport) Clone() *Transport {
	t.nextProtoOnce.Do(t.onceSetNextProtoDefaults)
	t2 := &Transport{
		Proxy:                  t.Proxy,
		DialContext:            t.DialContext,
		Dial:                   t.Dial,
		DialTLS:                t.DialTLS,
		DialTLSContext:         t.DialTLSContext,
		TLSHandshakeTimeout:    t.TLSHandshakeTimeout,
		DisableKeepAlives:      t.DisableKeepAlives,
		DisableCompression:     t.DisableCompression,
		MaxIdleConns:           t.MaxIdleConns,
		MaxIdleConnsPerHost:    t.MaxIdleConnsPerHost,
		MaxConnsPerHost:        t.MaxConnsPerHost,
		IdleConnTimeout:        t.IdleConnTimeout,
		ResponseHeaderTimeout:  t.ResponseHeaderTimeout,
		ExpectContinueTimeout:  t.ExpectContinueTimeout,
		ProxyConnectHeader:     t.ProxyConnectHeader.Clone(),
		GetProxyConnectHeader:  t.GetProxyConnectHeader,
		MaxResponseHeaderBytes: t.MaxResponseHeaderBytes,
		ForceAttemptHTTP2:      t.ForceAttemptHTTP2,
		WriteBufferSize:        t.WriteBufferSize,
		ReadBufferSize:         t.ReadBufferSize,
	}
	if t.TLSClientConfig != nil {
		t2.TLSClientConfig = t.TLSClientConfig.Clone()
	}
	if !t.tlsNextProtoWasNil {
		npm := map[string]func(authority string, c *tls.Conn) RoundTripper{}
		for k, v := range t.TLSNextProto {
			npm[k] = v
		}
		t2.TLSNextProto = npm
	}
	return t2
}

type h2Transport interface {
	CloseIdleConnections()
}

func (t *Transport) hasCustomTLSDialer() bool {
	return t.DialTLS != nil || t.DialTLSContext != nil
}

func (t *Transport) onceSetNextProtoDefaults() {
	t.tlsNextProtoWasNil = (t.TLSNextProto == nil)
	if strings.Contains(os.Getenv("GODEBUG"), "http2client=0") {
		return
	}

	altProto, _ := t.altProto.Load().(map[string]RoundTripper)
	if rv := reflect.ValueOf(altProto["https"]); rv.IsValid() && rv.Type().Kind() == reflect.Struct && rv.Type().NumField() == 1 {
		if v := rv.Field(0); v.CanInterface() {
			if h2i, ok := v.Interface().(h2Transport); ok {
				t.h2transport = h2i
				return
			}
		}
	}

		return
	}

		return
	}
	if omitBundledHTTP2 {
		return
	}
	t2, err := http2configureTransports(t)
	if err != nil {
		log.Printf("Error enabling Transport HTTP/2 support: %v", err)
		return
	}
	t.h2transport = t2

	if limit1 := t.MaxResponseHeaderBytes; limit1 != 0 && t2.MaxHeaderListSize == 0 {
		const h2max = 1<<32 - 1
		if limit1 >= h2max {
			t2.MaxHeaderListSize = h2max
		} else {
			t2.MaxHeaderListSize = uint32(limit1)
		}
	}
}

func ProxyFromEnvironment(req *Request) (*url.URL, error) {
	return envProxyFunc()(req.URL)
}

func ProxyURL(fixedURL *url.URL) func(*Request) (*url.URL, error) {
	return func(*Request) (*url.URL, error) {
		return fixedURL, nil
	}
}

type transportRequest struct {
	*Request                         // original request, not to be mutated
	extra     Header                 // extra headers to write, or nil
	trace     *httptrace.ClientTrace // optional
	cancelKey cancelKey

	mu  sync.Mutex // guards err
	err error      // first setError value for mapRoundTripError to consider
}

func (tr *transportRequest) extraHeaders() Header {
	if tr.extra == nil {
		tr.extra = make(Header)
	}
	return tr.extra
}

func (tr *transportRequest) setError(err error) {
	tr.mu.Lock()
	if tr.err == nil {
		tr.err = err
	}
	tr.mu.Unlock()
}

func (t *Transport) useRegisteredProtocol(req *Request) bool {

		return false
	}
	return true
}

func (t *Transport) alternateRoundTripper(req *Request) RoundTripper {
	if !t.useRegisteredProtocol(req) {
		return nil
	}
	altProto, _ := t.altProto.Load().(map[string]RoundTripper)
	return altProto[req.URL.Scheme]
}

func (t *Transport) roundTrip(req *Request) (*Response, error) {
	t.nextProtoOnce.Do(t.onceSetNextProtoDefaults)
	ctx := req.Context()
	trace := httptrace.ContextClientTrace(ctx)

	if req.URL == nil {
		req.closeBody()
		return nil, errors.New("http: nil Request.URL")
	}
	if req.Header == nil {
		req.closeBody()
		return nil, errors.New("http: nil Request.Header")
	}
	scheme := req.URL.Scheme
	isHTTP := scheme == "http" || scheme == "https"
	if isHTTP {
		for k, vv := range req.Header {
			if !httpguts.ValidHeaderFieldName(k) {
				req.closeBody()
				return nil, fmt.Errorf("net/http: invalid header field name %q", k)
			}
			for _, v := range vv {
				if !httpguts.ValidHeaderFieldValue(v) {
					req.closeBody()
					return nil, fmt.Errorf("net/http: invalid header field value %q for key %v", v, k)
				}
			}
		}
	}

	origReq := req
	cancelKey := cancelKey{origReq}
	req = setupRewindBody(req)

	if altRT := t.alternateRoundTripper(req); altRT != nil {
		if resp, err := altRT.RoundTrip(req); err != ErrSkipAltProtocol {
			return resp, err
		}
		var err error
		req, err = rewindBody(req)
		if err != nil {
			return nil, err
		}
	}
	if !isHTTP {
		req.closeBody()
		return nil, badStringError("unsupported protocol scheme", scheme)
	}
	if req.Method != "" && !validMethod(req.Method) {
		req.closeBody()
		return nil, fmt.Errorf("net/http: invalid method %q", req.Method)
	}
	if req.URL.Host == "" {
		req.closeBody()
		return nil, errors.New("http: no Host in request URL")
	}

	for {
		select {
		case <-ctx.Done():
			req.closeBody()
			return nil, ctx.Err()
		default:
		}

		treq := &transportRequest{Request: req, trace: trace, cancelKey: cancelKey}
		cm, err := t.connectMethodForRequest(treq)
		if err != nil {
			req.closeBody()
			return nil, err
		}

		pconn, err := t.getConn(treq, cm)
		if err != nil {
			t.setReqCanceler(cancelKey, nil)
			req.closeBody()
			return nil, err
		}

		var resp *Response

			t.setReqCanceler(cancelKey, nil) // not cancelable with CancelRequest
			resp, err = pconn.alt.RoundTrip(req)
		} else {
			resp, err = pconn.roundTrip(treq)
		}
		if err == nil {
			resp.Request = origReq
			return resp, nil
		}

		if http2isNoCachedConnError(err) {
			if t.removeIdleConn(pconn) {
				t.decConnsPerHost(pconn.cacheKey)
			}

			if e, ok := err.(transportReadFromServerError); ok {
				err = e.err
			}
			return nil, err
		}
		testHookRoundTripRetried()

		req, err = rewindBody(req)
		if err != nil {
			return nil, err
		}
	}
}

var errCannotRewind = errors.New("net/http: cannot rewind body after connection loss")

type readTrackingBody struct {
	io.ReadCloser
	didRead  bool
	didClose bool
}

func (r *readTrackingBody) Read(data []byte) (int, error) {
	r.didRead = true
	return r.ReadCloser.Read(data)
}

func (r *readTrackingBody) Close() error {
	r.didClose = true
	return r.ReadCloser.Close()
}

func setupRewindBody(req *Request) *Request {
	if req.Body == nil || req.Body == NoBody {
		return req
	}
	newReq := *req
	newReq.Body = &readTrackingBody{ReadCloser: req.Body}
	return &newReq
}

func rewindBody(req *Request) (rewound *Request, err error) {
	if req.Body == nil || req.Body == NoBody || (!req.Body.(*readTrackingBody).didRead && !req.Body.(*readTrackingBody).didClose) {
		return req, nil // nothing to rewind
	}
	if !req.Body.(*readTrackingBody).didClose {
		req.closeBody()
	}
	if req.GetBody == nil {
		return nil, errCannotRewind
	}
	body, err := req.GetBody()
	if err != nil {
		return nil, err
	}
	newReq := *req
	newReq.Body = &readTrackingBody{ReadCloser: body}
	return &newReq, nil
}

func (pc *persistConn) shouldRetryRequest(req *Request, err error) bool {

		return true
	}

		return false
	}

		return false
	}

		return req.outgoingLength() == 0 || req.GetBody != nil
	}

		return false
	}

		return true
	}

		return true
	}
	return false // conservatively
}

var ErrSkipAltProtocol = errors.New("net/http: skip alternate protocol")

func (t *Transport) RegisterProtocol(scheme string, rt RoundTripper) {
	t.altMu.Lock()
	defer t.altMu.Unlock()
	oldMap, _ := t.altProto.Load().(map[string]RoundTripper)
	if _, exists := oldMap[scheme]; exists {
		panic("protocol " + scheme + " already registered")
	}
	newMap := make(map[string]RoundTripper)
	for k, v := range oldMap {
		newMap[k] = v
	}
	newMap[scheme] = rt
	t.altProto.Store(newMap)
}

func (t *Transport) CloseIdleConnections() {
	t.nextProtoOnce.Do(t.onceSetNextProtoDefaults)
	t.idleMu.Lock()
	m := t.idleConn
	t.idleConn = nil
	t.closeIdle = true // close newly idle connections
	t.idleLRU = connLRU{}
	t.idleMu.Unlock()
	for _, conns := range m {
		for _, pconn := range conns {
			pconn.close(errCloseIdleConns)
		}
	}
	if t2 := t.h2transport; t2 != nil {
		t2.CloseIdleConnections()
	}
}

func (t *Transport) CancelRequest(req *Request) {
	t.cancelRequest(cancelKey{req}, errRequestCanceled)
}

func (t *Transport) cancelRequest(key cancelKey, err error) bool {
	t.reqMu.Lock()
	cancel := t.reqCanceler[key]
	delete(t.reqCanceler, key)
	t.reqMu.Unlock()
	if cancel != nil {
		cancel(err)
	}

	return cancel != nil
}

	envProxyOnce      sync.Once
	envProxyFuncValue func(*url.URL) (*url.URL, error)
)

func envProxyFunc() func(*url.URL) (*url.URL, error) {
	envProxyOnce.Do(func() {
		envProxyFuncValue = httpproxy.FromEnvironment().ProxyFunc()
	})
	return envProxyFuncValue
}

func resetProxyConfig() {
	envProxyOnce = sync.Once{}
	envProxyFuncValue = nil
}

func (t *Transport) connectMethodForRequest(treq *transportRequest) (cm connectMethod, err error) {
	cm.targetScheme = treq.URL.Scheme
	cm.targetAddr = canonicalAddr(treq.URL)
	if t.Proxy != nil {
		cm.proxyURL, err = t.Proxy(treq.Request)
	}
	cm.onlyH1 = treq.requiresHTTP1()
	return cm, err
}

func (cm *connectMethod) proxyAuth() string {
	if cm.proxyURL == nil {
		return ""
	}
	if u := cm.proxyURL.User; u != nil {
		username := u.Username()
		password, _ := u.Password()
		return "Basic " + basicAuth(username, password)
	}
	return ""
}

var (
	errKeepAlivesDisabled = errors.New("http: putIdleConn: keep alives disabled")
	errConnBroken         = errors.New("http: putIdleConn: connection is in bad state")
	errCloseIdle          = errors.New("http: putIdleConn: CloseIdleConnections was called")
	errTooManyIdle        = errors.New("http: putIdleConn: too many idle connections")
	errTooManyIdleHost    = errors.New("http: putIdleConn: too many idle connections for host")
	errCloseIdleConns     = errors.New("http: CloseIdleConnections called")
	errReadLoopExiting    = errors.New("http: persistConn.readLoop exiting")
	errIdleConnTimeout    = errors.New("http: idle connection timeout")

	errServerClosedIdle = errors.New("http: server closed idle connection")
)

type transportReadFromServerError struct {
	err error
}

func (e transportReadFromServerError) Unwrap() error { return e.err }

func (e transportReadFromServerError) Error() string {
	return fmt.Sprintf("net/http: Transport failed to read from server: %v", e.err)
}

func (t *Transport) putOrCloseIdleConn(pconn *persistConn) {
	if err := t.tryPutIdleConn(pconn); err != nil {
		pconn.close(err)
	}
}

func (t *Transport) maxIdleConnsPerHost() int {
	if v := t.MaxIdleConnsPerHost; v != 0 {
		return v
	}
	return DefaultMaxIdleConnsPerHost
}

func (t *Transport) tryPutIdleConn(pconn *persistConn) error {
	if t.DisableKeepAlives || t.MaxIdleConnsPerHost < 0 {
		return errKeepAlivesDisabled
	}
	if pconn.isBroken() {
		return errConnBroken
	}
	pconn.markReused()

	t.idleMu.Lock()
	defer t.idleMu.Unlock()

	if pconn.alt != nil && t.idleLRU.m[pconn] != nil {
		return nil
	}

	key := pconn.cacheKey
	if q, ok := t.idleConnWait[key]; ok {
		done := false

			for q.len() > 0 {
				w := q.popFront()
				if w.tryDeliver(pconn, nil) {
					done = true
					break
				}
			}

			for q.len() > 0 {
				w := q.popFront()
				w.tryDeliver(pconn, nil)
			}
		}
		if q.len() == 0 {
			delete(t.idleConnWait, key)
		} else {
			t.idleConnWait[key] = q
		}
		if done {
			return nil
		}
	}

	if t.closeIdle {
		return errCloseIdle
	}
	if t.idleConn == nil {
		t.idleConn = make(map[connectMethodKey][]*persistConn)
	}
	idles := t.idleConn[key]
	if len(idles) >= t.maxIdleConnsPerHost() {
		return errTooManyIdleHost
	}
	for _, exist := range idles {
		if exist == pconn {
			log.Fatalf("dup idle pconn %p in freelist", pconn)
		}
	}
	t.idleConn[key] = append(idles, pconn)
	t.idleLRU.add(pconn)
	if t.MaxIdleConns != 0 && t.idleLRU.len() > t.MaxIdleConns {
		oldest := t.idleLRU.removeOldest()
		oldest.close(errTooManyIdle)
		t.removeIdleConnLocked(oldest)
	}

	if t.IdleConnTimeout > 0 && pconn.alt == nil {
		if pconn.idleTimer != nil {
			pconn.idleTimer.Reset(t.IdleConnTimeout)
		} else {
			pconn.idleTimer = time.AfterFunc(t.IdleConnTimeout, pconn.closeConnIfStillIdle)
		}
	}
	pconn.idleAt = time.Now()
	return nil
}

func (t *Transport) queueForIdleConn(w *wantConn) (delivered bool) {
	if t.DisableKeepAlives {
		return false
	}

	t.idleMu.Lock()
	defer t.idleMu.Unlock()

	t.closeIdle = false

		return false
	}

	var oldTime time.Time
	if t.IdleConnTimeout > 0 {
		oldTime = time.Now().Add(-t.IdleConnTimeout)
	}

	if list, ok := t.idleConn[w.key]; ok {
		stop := false
		delivered := false
		for len(list) > 0 && !stop {
			pconn := list[len(list)-1]

			tooOld := !oldTime.IsZero() && pconn.idleAt.Round(0).Before(oldTime)

				go pconn.closeConnIfStillIdle()
			}

				list = list[:len(list)-1]
				continue
			}
			delivered = w.tryDeliver(pconn, nil)
			if delivered {

					t.idleLRU.remove(pconn)
					list = list[:len(list)-1]
				}
			}
			stop = true
		}
		if len(list) > 0 {
			t.idleConn[w.key] = list
		} else {
			delete(t.idleConn, w.key)
		}
		if stop {
			return delivered
		}
	}

	if t.idleConnWait == nil {
		t.idleConnWait = make(map[connectMethodKey]wantConnQueue)
	}
	q := t.idleConnWait[w.key]
	q.cleanFront()
	q.pushBack(w)
	t.idleConnWait[w.key] = q
	return false
}

func (t *Transport) removeIdleConn(pconn *persistConn) bool {
	t.idleMu.Lock()
	defer t.idleMu.Unlock()
	return t.removeIdleConnLocked(pconn)
}

func (t *Transport) removeIdleConnLocked(pconn *persistConn) bool {
	if pconn.idleTimer != nil {
		pconn.idleTimer.Stop()
	}
	t.idleLRU.remove(pconn)
	key := pconn.cacheKey
	pconns := t.idleConn[key]
	var removed bool
	switch len(pconns) {

	case 1:
		if pconns[0] == pconn {
			delete(t.idleConn, key)
			removed = true
		}
	default:
		for i, v := range pconns {
			if v != pconn {
				continue

			copy(pconns[i:], pconns[i+1:])
			t.idleConn[key] = pconns[:len(pconns)-1]
			removed = true
			break
		}
	}
	return removed
}

func (t *Transport) setReqCanceler(key cancelKey, fn func(error)) {
	t.reqMu.Lock()
	defer t.reqMu.Unlock()
	if t.reqCanceler == nil {
		t.reqCanceler = make(map[cancelKey]func(error))
	}
	if fn != nil {
		t.reqCanceler[key] = fn
	} else {
		delete(t.reqCanceler, key)
	}
}

func (t *Transport) replaceReqCanceler(key cancelKey, fn func(error)) bool {
	t.reqMu.Lock()
	defer t.reqMu.Unlock()
	_, ok := t.reqCanceler[key]
	if !ok {
		return false
	}
	if fn != nil {
		t.reqCanceler[key] = fn
	} else {
		delete(t.reqCanceler, key)
	}
	return true
}

var zeroDialer net.Dialer

func (t *Transport) dial(ctx context.Context, network, addr string) (net.Conn, error) {
	if t.DialContext != nil {
		return t.DialContext(ctx, network, addr)
	}
	if t.Dial != nil {
		c, err := t.Dial(network, addr)
		if c == nil && err == nil {
			err = errors.New("net/http: Transport.Dial hook returned (nil, nil)")
		}
		return c, err
	}
	return zeroDialer.DialContext(ctx, network, addr)
}

type wantConn struct {
	cm    connectMethod
	key   connectMethodKey // cm.key()
	ctx   context.Context  // context for dial
	ready chan struct{}    // closed when pc, err pair is delivered

	beforeDial func()
	afterDial  func()

	mu  sync.Mutex // protects pc, err, close(ready)
	pc  *persistConn
	err error
}

func (w *wantConn) waiting() bool {
	select {
	case <-w.ready:
		return false
	default:
		return true
	}
}

func (w *wantConn) tryDeliver(pc *persistConn, err error) bool {
	w.mu.Lock()
	defer w.mu.Unlock()

	if w.pc != nil || w.err != nil {
		return false
	}

	w.pc = pc
	w.err = err
	if w.pc == nil && w.err == nil {
		panic("net/http: internal error: misuse of tryDeliver")
	}
	close(w.ready)
	return true
}

func (w *wantConn) cancel(t *Transport, err error) {
	w.mu.Lock()
	if w.pc == nil && w.err == nil {
		close(w.ready) // catch misbehavior in future delivery
	}
	pc := w.pc
	w.pc = nil
	w.err = err
	w.mu.Unlock()

	if pc != nil {
		t.putOrCloseIdleConn(pc)
	}
}

	head    []*wantConn
	headPos int
	tail    []*wantConn
}

func (q *wantConnQueue) len() int {
	return len(q.head) - q.headPos + len(q.tail)
}

func (q *wantConnQueue) pushBack(w *wantConn) {
	q.tail = append(q.tail, w)
}

func (q *wantConnQueue) popFront() *wantConn {
	if q.headPos >= len(q.head) {
		if len(q.tail) == 0 {
			return nil

		q.head, q.headPos, q.tail = q.tail, 0, q.head[:0]
	}
	w := q.head[q.headPos]
	q.head[q.headPos] = nil
	q.headPos++
	return w
}

func (q *wantConnQueue) peekFront() *wantConn {
	if q.headPos < len(q.head) {
		return q.head[q.headPos]
	}
	if len(q.tail) > 0 {
		return q.tail[0]
	}
	return nil
}

func (q *wantConnQueue) cleanFront() (cleaned bool) {
	for {
		w := q.peekFront()
		if w == nil || w.waiting() {
			return cleaned
		}
		q.popFront()
		cleaned = true
	}
}

func (t *Transport) customDialTLS(ctx context.Context, network, addr string) (conn net.Conn, err error) {
	if t.DialTLSContext != nil {
		conn, err = t.DialTLSContext(ctx, network, addr)
	} else {
		conn, err = t.DialTLS(network, addr)
	}
	if conn == nil && err == nil {
		err = errors.New("net/http: Transport.DialTLS or DialTLSContext returned (nil, nil)")
	}
	return
}

func (t *Transport) getConn(treq *transportRequest, cm connectMethod) (pc *persistConn, err error) {
	req := treq.Request
	trace := treq.trace
	ctx := req.Context()
	if trace != nil && trace.GetConn != nil {
		trace.GetConn(cm.addr())
	}

	w := &wantConn{
		cm:         cm,
		key:        cm.key(),
		ctx:        ctx,
		ready:      make(chan struct{}, 1),
		beforeDial: testHookPrePendingDial,
		afterDial:  testHookPostPendingDial,
	}
	defer func() {
		if err != nil {
			w.cancel(t, err)
		}
	}()

	if delivered := t.queueForIdleConn(w); delivered {

		if pc.alt == nil && trace != nil && trace.GotConn != nil {
			trace.GotConn(pc.gotIdleConnTrace(pc.idleAt))

		t.setReqCanceler(treq.cancelKey, func(error) {})
		return pc, nil
	}

	cancelc := make(chan error, 1)
	t.setReqCanceler(treq.cancelKey, func(err error) { cancelc <- err })

	t.queueForDial(w)

	select {

		if w.pc != nil && w.pc.alt == nil && trace != nil && trace.GotConn != nil {
			trace.GotConn(httptrace.GotConnInfo{Conn: w.pc.conn, Reused: w.pc.isReused()})
		}

			select {
			case <-req.Cancel:
				return nil, errRequestCanceledConn
			case <-req.Context().Done():
				return nil, req.Context().Err()
			case err := <-cancelc:
				if err == errRequestCanceled {
					err = errRequestCanceledConn
				}
				return nil, err

			}
		}
		return w.pc, w.err
	case <-req.Cancel:
		return nil, errRequestCanceledConn
	case <-req.Context().Done():
		return nil, req.Context().Err()
	case err := <-cancelc:
		if err == errRequestCanceled {
			err = errRequestCanceledConn
		}
		return nil, err
	}
}

func (t *Transport) queueForDial(w *wantConn) {
	w.beforeDial()
	if t.MaxConnsPerHost <= 0 {
		go t.dialConnFor(w)
		return
	}

	t.connsPerHostMu.Lock()
	defer t.connsPerHostMu.Unlock()

	if n := t.connsPerHost[w.key]; n < t.MaxConnsPerHost {
		if t.connsPerHost == nil {
			t.connsPerHost = make(map[connectMethodKey]int)
		}
		t.connsPerHost[w.key] = n + 1
		go t.dialConnFor(w)
		return
	}

	if t.connsPerHostWait == nil {
		t.connsPerHostWait = make(map[connectMethodKey]wantConnQueue)
	}
	q := t.connsPerHostWait[w.key]
	q.cleanFront()
	q.pushBack(w)
	t.connsPerHostWait[w.key] = q
}

func (t *Transport) dialConnFor(w *wantConn) {
	defer w.afterDial()

	pc, err := t.dialConn(w.ctx, w.cm)
	delivered := w.tryDeliver(pc, err)

		t.putOrCloseIdleConn(pc)
	}
	if err != nil {
		t.decConnsPerHost(w.key)
	}
}

func (t *Transport) decConnsPerHost(key connectMethodKey) {
	if t.MaxConnsPerHost <= 0 {
		return
	}

	t.connsPerHostMu.Lock()
	defer t.connsPerHostMu.Unlock()
	n := t.connsPerHost[key]

		panic("net/http: internal error: connCount underflow")
	}

	if q := t.connsPerHostWait[key]; q.len() > 0 {
		done := false
		for q.len() > 0 {
			w := q.popFront()
			if w.waiting() {
				go t.dialConnFor(w)
				done = true
				break
			}
		}
		if q.len() == 0 {
			delete(t.connsPerHostWait, key)

			t.connsPerHostWait[key] = q
		}
		if done {
			return
		}
	}

	if n--; n == 0 {
		delete(t.connsPerHost, key)
	} else {
		t.connsPerHost[key] = n
	}
}

	cfg := cloneTLSConfig(pconn.t.TLSClientConfig)
	if cfg.ServerName == "" {
		cfg.ServerName = name
	}
	if pconn.cacheKey.onlyH1 {
		cfg.NextProtos = nil
	}
	plainConn := pconn.conn
	tlsConn := tls.Client(plainConn, cfg)
	errc := make(chan error, 2)
	var timer *time.Timer // for canceling TLS handshake
	if d := pconn.t.TLSHandshakeTimeout; d != 0 {
		timer = time.AfterFunc(d, func() {
			errc <- tlsHandshakeTimeoutError{}
		})
	}
	go func() {
		if trace != nil && trace.TLSHandshakeStart != nil {
			trace.TLSHandshakeStart()
		}
		err := tlsConn.Handshake()
		if timer != nil {
			timer.Stop()
		}
		errc <- err
	}()
	if err := <-errc; err != nil {
		plainConn.Close()
		if trace != nil && trace.TLSHandshakeDone != nil {
			trace.TLSHandshakeDone(tls.ConnectionState{}, err)
		}
		return err
	}
	cs := tlsConn.ConnectionState()
	if trace != nil && trace.TLSHandshakeDone != nil {
		trace.TLSHandshakeDone(cs, nil)
	}
	pconn.tlsState = &cs
	pconn.conn = tlsConn
	return nil
}

type erringRoundTripper interface {
	RoundTripErr() error
}

func (t *Transport) dialConn(ctx context.Context, cm connectMethod) (pconn *persistConn, err error) {
	pconn = &persistConn{
		t:             t,
		cacheKey:      cm.key(),
		reqch:         make(chan requestAndChan, 1),
		writech:       make(chan writeRequest, 1),
		closech:       make(chan struct{}),
		writeErrCh:    make(chan error, 1),
		writeLoopDone: make(chan struct{}),
	}
	trace := httptrace.ContextClientTrace(ctx)
	wrapErr := func(err error) error {

			return &net.OpError{Op: "proxyconnect", Net: "tcp", Err: err}
		}
		return err
	}
	if cm.scheme() == "https" && t.hasCustomTLSDialer() {
		var err error
		pconn.conn, err = t.customDialTLS(ctx, "tcp", cm.addr())
		if err != nil {
			return nil, wrapErr(err)
		}

			if trace != nil && trace.TLSHandshakeStart != nil {
				trace.TLSHandshakeStart()
			}
			if err := tc.Handshake(); err != nil {
				go pconn.conn.Close()
				if trace != nil && trace.TLSHandshakeDone != nil {
					trace.TLSHandshakeDone(tls.ConnectionState{}, err)
				}
				return nil, err
			}
			cs := tc.ConnectionState()
			if trace != nil && trace.TLSHandshakeDone != nil {
				trace.TLSHandshakeDone(cs, nil)
			}
			pconn.tlsState = &cs
		}
	} else {
		conn, err := t.dial(ctx, "tcp", cm.addr())
		if err != nil {
			return nil, wrapErr(err)
		}
		pconn.conn = conn
		if cm.scheme() == "https" {
			var firstTLSHost string
			if firstTLSHost, _, err = net.SplitHostPort(cm.addr()); err != nil {
				return nil, wrapErr(err)
			}
			if err = pconn.addTLS(firstTLSHost, trace); err != nil {
				return nil, wrapErr(err)
			}
		}
	}

	switch {

	case cm.proxyURL.Scheme == "socks5":
		conn := pconn.conn
		d := socksNewDialer("tcp", conn.RemoteAddr().String())
		if u := cm.proxyURL.User; u != nil {
			auth := &socksUsernamePassword{
				Username: u.Username(),
			}
			auth.Password, _ = u.Password()
			d.AuthMethods = []socksAuthMethod{
				socksAuthMethodNotRequired,
				socksAuthMethodUsernamePassword,
			}
			d.Authenticate = auth.Authenticate
		}
		if _, err := d.DialWithConn(ctx, conn, "tcp", cm.targetAddr); err != nil {
			conn.Close()
			return nil, err
		}
	case cm.targetScheme == "http":
		pconn.isProxy = true
		if pa := cm.proxyAuth(); pa != "" {
			pconn.mutateHeaderFunc = func(h Header) {
				h.Set("Proxy-Authorization", pa)
			}
		}
	case cm.targetScheme == "https":
		conn := pconn.conn
		var hdr Header
		if t.GetProxyConnectHeader != nil {
			var err error
			hdr, err = t.GetProxyConnectHeader(ctx, cm.proxyURL, cm.targetAddr)
			if err != nil {
				conn.Close()
				return nil, err
			}
		} else {
			hdr = t.ProxyConnectHeader
		}
		if hdr == nil {
			hdr = make(Header)
		}
		if pa := cm.proxyAuth(); pa != "" {
			hdr = hdr.Clone()
			hdr.Set("Proxy-Authorization", pa)
		}
		connectReq := &Request{
			Method: "CONNECT",
			URL:    &url.URL{Opaque: cm.targetAddr},
			Host:   cm.targetAddr,
			Header: hdr,
		}

		connectCtx := ctx
		if ctx.Done() == nil {
			newCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
			defer cancel()
			connectCtx = newCtx
		}

		didReadResponse := make(chan struct{}) // closed after CONNECT write+read is done or fails
		var (
			resp *Response
			err  error // write or read error

		go func() {
			defer close(didReadResponse)
			err = connectReq.Write(conn)
			if err != nil {
				return

			br := bufio.NewReader(conn)
			resp, err = ReadResponse(br, connectReq)
		}()
		select {
		case <-connectCtx.Done():
			conn.Close()
			<-didReadResponse
			return nil, connectCtx.Err()

		}
		if err != nil {
			conn.Close()
			return nil, err
		}
		if resp.StatusCode != 200 {
			f := strings.SplitN(resp.Status, " ", 2)
			conn.Close()
			if len(f) < 2 {
				return nil, errors.New("unknown status code")
			}
			return nil, errors.New(f[1])
		}
	}

	if cm.proxyURL != nil && cm.targetScheme == "https" {
		if err := pconn.addTLS(cm.tlsHost(), trace); err != nil {
			return nil, err
		}
	}

	if s := pconn.tlsState; s != nil && s.NegotiatedProtocolIsMutual && s.NegotiatedProtocol != "" {
		if next, ok := t.TLSNextProto[s.NegotiatedProtocol]; ok {
			alt := next(cm.targetAddr, pconn.conn.(*tls.Conn))

				return nil, e.RoundTripErr()
			}
			return &persistConn{t: t, cacheKey: pconn.cacheKey, alt: alt}, nil
		}
	}

	pconn.br = bufio.NewReaderSize(pconn, t.readBufferSize())
	pconn.bw = bufio.NewWriterSize(persistConnWriter{pconn}, t.writeBufferSize())

	go pconn.readLoop()
	go pconn.writeLoop()
	return pconn, nil
}

type persistConnWriter struct {
	pc *persistConn
}

func (w persistConnWriter) Write(p []byte) (n int, err error) {
	n, err = w.pc.conn.Write(p)
	w.pc.nwrite += int64(n)
	return
}

func (w persistConnWriter) ReadFrom(r io.Reader) (n int64, err error) {
	n, err = io.Copy(w.pc.conn, r)
	w.pc.nwrite += n
	return
}

var _ io.ReaderFrom = (*persistConnWriter)(nil)

type connectMethod struct {
	_            incomparable
	proxyURL     *url.URL // nil for no proxy, else full proxy URL

	targetAddr string
	onlyH1     bool // whether to disable HTTP/2 and force HTTP/1
}

func (cm *connectMethod) key() connectMethodKey {
	proxyStr := ""
	targetAddr := cm.targetAddr
	if cm.proxyURL != nil {
		proxyStr = cm.proxyURL.String()
		if (cm.proxyURL.Scheme == "http" || cm.proxyURL.Scheme == "https") && cm.targetScheme == "http" {
			targetAddr = ""
		}
	}
	return connectMethodKey{
		proxy:  proxyStr,
		scheme: cm.targetScheme,
		addr:   targetAddr,
		onlyH1: cm.onlyH1,
	}
}

func (cm *connectMethod) scheme() string {
	if cm.proxyURL != nil {
		return cm.proxyURL.Scheme
	}
	return cm.targetScheme
}

func (cm *connectMethod) addr() string {
	if cm.proxyURL != nil {
		return canonicalAddr(cm.proxyURL)
	}
	return cm.targetAddr
}

func (cm *connectMethod) tlsHost() string {
	h := cm.targetAddr
	if hasPort(h) {
		h = h[:strings.LastIndex(h, ":")]
	}
	return h
}

type connectMethodKey struct {
	proxy, scheme, addr string
	onlyH1              bool
}

	var h1 string
	if k.onlyH1 {
		h1 = ",h1"
	}
	return fmt.Sprintf("%s|%s%s|%s", k.proxy, k.scheme, h1, k.addr)
}

	alt RoundTripper

	t         *Transport
	cacheKey  connectMethodKey
	conn      net.Conn
	tlsState  *tls.ConnectionState
	br        *bufio.Reader       // from conn
	bw        *bufio.Writer       // to conn
	nwrite    int64               // bytes written
	reqch     chan requestAndChan // written by roundTrip; read by readLoop
	writech   chan writeRequest   // written by roundTrip; read by writeLoop
	closech   chan struct{}       // closed when conn closed
	isProxy   bool
	sawEOF    bool  // whether we've seen EOF from conn; owned by readLoop

	writeErrCh chan error

	writeLoopDone chan struct{} // closed when write loop ends

	idleAt    time.Time   // time it last become idle
	idleTimer *time.Timer // holding an AfterFunc to close it

	mu                   sync.Mutex // guards following fields
	numExpectedResponses int
	closed               error // set non-nil when conn is closed, before closech is closed
	canceledErr          error // set non-nil if conn is canceled
	broken               bool  // an error has happened on this connection; marked broken so it's not reused.

	mutateHeaderFunc func(Header)
}

func (pc *persistConn) maxHeaderResponseSize() int64 {
	if v := pc.t.MaxResponseHeaderBytes; v != 0 {
		return v
	}
	return 10 << 20 // conservative default; same as http2
}

func (pc *persistConn) Read(p []byte) (n int, err error) {
	if pc.readLimit <= 0 {
		return 0, fmt.Errorf("read limit of %d bytes exhausted", pc.maxHeaderResponseSize())
	}
	if int64(len(p)) > pc.readLimit {
		p = p[:pc.readLimit]
	}
	n, err = pc.conn.Read(p)
	if err == io.EOF {
		pc.sawEOF = true
	}
	pc.readLimit -= int64(n)
	return
}

func (pc *persistConn) isBroken() bool {
	pc.mu.Lock()
	b := pc.closed != nil
	pc.mu.Unlock()
	return b
}

func (pc *persistConn) canceled() error {
	pc.mu.Lock()
	defer pc.mu.Unlock()
	return pc.canceledErr
}

func (pc *persistConn) isReused() bool {
	pc.mu.Lock()
	r := pc.reused
	pc.mu.Unlock()
	return r
}

func (pc *persistConn) gotIdleConnTrace(idleAt time.Time) (t httptrace.GotConnInfo) {
	pc.mu.Lock()
	defer pc.mu.Unlock()
	t.Reused = pc.reused
	t.Conn = pc.conn
	t.WasIdle = true
	if !idleAt.IsZero() {
		t.IdleTime = time.Since(idleAt)
	}
	return
}

func (pc *persistConn) cancelRequest(err error) {
	pc.mu.Lock()
	defer pc.mu.Unlock()
	pc.canceledErr = err
	pc.closeLocked(errRequestCanceled)
}

func (pc *persistConn) closeConnIfStillIdle() {
	t := pc.t
	t.idleMu.Lock()
	defer t.idleMu.Unlock()

		return
	}
	t.removeIdleConnLocked(pc)
	pc.close(errIdleConnTimeout)
}

func (pc *persistConn) mapRoundTripError(req *transportRequest, startBytesWritten int64, err error) error {
	if err == nil {
		return nil
	}

	<-pc.writeLoopDone

	if cerr := pc.canceled(); cerr != nil {
		return cerr
	}

	req.mu.Lock()
	reqErr := req.err
	req.mu.Unlock()
	if reqErr != nil {
		return reqErr
	}

		return err
	}

		return err
	}
	if pc.isBroken() {
		if pc.nwrite == startBytesWritten {
			return nothingWrittenError{err}
		}
		return fmt.Errorf("net/http: HTTP/1.x transport connection broken: %v", err)
	}
	return err
}

var errCallerOwnsConn = errors.New("read loop ending; caller owns writable underlying conn")

func (pc *persistConn) readLoop() {
	closeErr := errReadLoopExiting // default value, if not changed below
	defer func() {
		pc.close(closeErr)
		pc.t.removeIdleConn(pc)
	}()

	tryPutIdleConn := func(trace *httptrace.ClientTrace) bool {
		if err := pc.t.tryPutIdleConn(pc); err != nil {
			closeErr = err
			if trace != nil && trace.PutIdleConn != nil && err != errKeepAlivesDisabled {
				trace.PutIdleConn(err)
			}
			return false
		}
		if trace != nil && trace.PutIdleConn != nil {
			trace.PutIdleConn(nil)
		}
		return true
	}

	eofc := make(chan struct{})
	defer close(eofc) // unblock reader on errors

	testHookMu.Lock()
	testHookReadLoopBeforeNextRead := testHookReadLoopBeforeNextRead
	testHookMu.Unlock()

	alive := true
	for alive {
		pc.readLimit = pc.maxHeaderResponseSize()
		_, err := pc.br.Peek(1)

		pc.mu.Lock()
		if pc.numExpectedResponses == 0 {
			pc.readLoopPeekFailLocked(err)
			pc.mu.Unlock()
			return
		}
		pc.mu.Unlock()

		rc := <-pc.reqch
		trace := httptrace.ContextClientTrace(rc.req.Context())

		var resp *Response
		if err == nil {
			resp, err = pc.readResponse(rc, trace)
		} else {
			err = transportReadFromServerError{err}
			closeErr = err
		}

		if err != nil {
			if pc.readLimit <= 0 {
				err = fmt.Errorf("net/http: server response headers exceeded %d bytes; aborted", pc.maxHeaderResponseSize())
			}

			select {
			case rc.ch <- responseAndError{err: err}:
			case <-rc.callerGone:
				return
			}
			return
		}
		pc.readLimit = maxInt64 // effectively no limit for response bodies

		pc.mu.Lock()
		pc.numExpectedResponses--
		pc.mu.Unlock()

		bodyWritable := resp.bodyIsWritable()
		hasBody := rc.req.Method != "HEAD" && resp.ContentLength != 0

			alive = false
		}

		if !hasBody || bodyWritable {
			replaced := pc.t.replaceReqCanceler(rc.cancelKey, nil)

			alive = alive &&
				!pc.sawEOF &&
				pc.wroteRequest() &&
				replaced && tryPutIdleConn(trace)

			if bodyWritable {
				closeErr = errCallerOwnsConn
			}

			select {
			case rc.ch <- responseAndError{res: resp}:
			case <-rc.callerGone:
				return
			}

			testHookReadLoopBeforeNextRead()
			continue
		}

		waitForBodyRead := make(chan bool, 2)
		body := &bodyEOFSignal{
			body: resp.Body,
			earlyCloseFn: func() error {
				waitForBodyRead <- false
				<-eofc // will be closed by deferred call at the end of the function
				return nil

			},
			fn: func(err error) error {
				isEOF := err == io.EOF
				waitForBodyRead <- isEOF
				if isEOF {
					<-eofc // see comment above eofc declaration
				} else if err != nil {
					if cerr := pc.canceled(); cerr != nil {
						return cerr
					}
				}
				return err
			},
		}

		resp.Body = body
		if rc.addedGzip && strings.EqualFold(resp.Header.Get("Content-Encoding"), "gzip") {
			resp.Body = &gzipReader{body: body}
			resp.Header.Del("Content-Encoding")
			resp.Header.Del("Content-Length")
			resp.ContentLength = -1
			resp.Uncompressed = true
		}

		select {
		case rc.ch <- responseAndError{res: resp}:
		case <-rc.callerGone:
			return
		}

		select {
		case bodyEOF := <-waitForBodyRead:
			replaced := pc.t.replaceReqCanceler(rc.cancelKey, nil) // before pc might return to idle pool
			alive = alive &&
				bodyEOF &&
				!pc.sawEOF &&
				pc.wroteRequest() &&
				replaced && tryPutIdleConn(trace)
			if bodyEOF {
				eofc <- struct{}{}
			}
		case <-rc.req.Cancel:
			alive = false
			pc.t.CancelRequest(rc.req)
		case <-rc.req.Context().Done():
			alive = false
			pc.t.cancelRequest(rc.cancelKey, rc.req.Context().Err())
		case <-pc.closech:
			alive = false
		}

		testHookReadLoopBeforeNextRead()
	}
}

func (pc *persistConn) readLoopPeekFailLocked(peekErr error) {
	if pc.closed != nil {
		return
	}
	if n := pc.br.Buffered(); n > 0 {
		buf, _ := pc.br.Peek(n)
		if is408Message(buf) {
			pc.closeLocked(errServerClosedIdle)
			return
		} else {
			log.Printf("Unsolicited response received on idle HTTP channel starting with %q; err=%v", buf, peekErr)
		}
	}

		pc.closeLocked(errServerClosedIdle)
	} else {
		pc.closeLocked(fmt.Errorf("readLoopPeekFailLocked: %v", peekErr))
	}
}

func is408Message(buf []byte) bool {
	if len(buf) < len("HTTP/1.x 408") {
		return false
	}
	if string(buf[:7]) != "HTTP/1." {
		return false
	}
	return string(buf[8:12]) == " 408"
}

func (pc *persistConn) readResponse(rc requestAndChan, trace *httptrace.ClientTrace) (resp *Response, err error) {
	if trace != nil && trace.GotFirstResponseByte != nil {
		if peek, err := pc.br.Peek(1); err == nil && len(peek) == 1 {
			trace.GotFirstResponseByte()
		}
	}
	num1xx := 0               // number of informational 1xx headers received
	const max1xxResponses = 5 // arbitrary bound on number of informational responses

	continueCh := rc.continueCh
	for {
		resp, err = ReadResponse(pc.br, rc.req)
		if err != nil {
			return
		}
		resCode := resp.StatusCode
		if continueCh != nil {
			if resCode == 100 {
				if trace != nil && trace.Got100Continue != nil {
					trace.Got100Continue()
				}
				continueCh <- struct{}{}
				continueCh = nil
			} else if resCode >= 200 {
				close(continueCh)
				continueCh = nil
			}
		}

		is1xxNonTerminal := is1xx && resCode != StatusSwitchingProtocols
		if is1xxNonTerminal {
			num1xx++
			if num1xx > max1xxResponses {
				return nil, errors.New("net/http: too many 1xx informational responses")
			}
			pc.readLimit = pc.maxHeaderResponseSize() // reset the limit
			if trace != nil && trace.Got1xxResponse != nil {
				if err := trace.Got1xxResponse(resCode, textproto.MIMEHeader(resp.Header)); err != nil {
					return nil, err
				}
			}
			continue
		}
		break
	}
	if resp.isProtocolSwitch() {
		resp.Body = newReadWriteCloserBody(pc.br, pc.conn)
	}

	resp.TLS = pc.tlsState
	return
}

func (pc *persistConn) waitForContinue(continueCh <-chan struct{}) func() bool {
	if continueCh == nil {
		return nil
	}
	return func() bool {
		timer := time.NewTimer(pc.t.ExpectContinueTimeout)
		defer timer.Stop()

		select {
		case _, ok := <-continueCh:
			return ok
		case <-timer.C:
			return true
		case <-pc.closech:
			return false
		}
	}
}

func newReadWriteCloserBody(br *bufio.Reader, rwc io.ReadWriteCloser) io.ReadWriteCloser {
	body := &readWriteCloserBody{ReadWriteCloser: rwc}
	if br.Buffered() != 0 {
		body.br = br
	}
	return body
}

type readWriteCloserBody struct {
	_  incomparable
	br *bufio.Reader // used until empty
	io.ReadWriteCloser
}

func (b *readWriteCloserBody) Read(p []byte) (n int, err error) {
	if b.br != nil {
		if n := b.br.Buffered(); len(p) > n {
			p = p[:n]
		}
		n, err = b.br.Read(p)
		if b.br.Buffered() == 0 {
			b.br = nil
		}
		return n, err
	}
	return b.ReadWriteCloser.Read(p)
}

type nothingWrittenError struct {
	error
}

func (pc *persistConn) writeLoop() {
	defer close(pc.writeLoopDone)
	for {
		select {
		case wr := <-pc.writech:
			startBytesWritten := pc.nwrite
			err := wr.req.Request.write(pc.bw, pc.isProxy, wr.req.extra, pc.waitForContinue(wr.continueCh))
			if bre, ok := err.(requestBodyReadError); ok {

				wr.req.setError(err)
			}
			if err == nil {
				err = pc.bw.Flush()
			}
			if err != nil {
				if pc.nwrite == startBytesWritten {
					err = nothingWrittenError{err}
				}
			}
			pc.writeErrCh <- err // to the body reader, which might recycle us
			wr.ch <- err         // to the roundTrip function
			if err != nil {
				pc.close(err)
				return
			}
		case <-pc.closech:
			return
		}
	}
}

const maxWriteWaitBeforeConnReuse = 50 * time.Millisecond

func (pc *persistConn) wroteRequest() bool {
	select {

		return err == nil

		t := time.NewTimer(maxWriteWaitBeforeConnReuse)
		defer t.Stop()
		select {
		case err := <-pc.writeErrCh:
			return err == nil
		case <-t.C:
			return false
		}
	}
}

type responseAndError struct {
	_   incomparable
	res *Response // else use this response (see res method)
	err error
}

type requestAndChan struct {
	_         incomparable
	req       *Request
	cancelKey cancelKey
	ch        chan responseAndError // unbuffered; always send in select on callerGone

	addedGzip bool

	continueCh chan<- struct{}

	callerGone <-chan struct{} // closed when roundTrip caller has returned
}

type writeRequest struct {
	req *transportRequest
	ch  chan<- error

	continueCh <-chan struct{}
}

type httpError struct {
	err     string
	timeout bool
}

func (e *httpError) Error() string   { return e.err }
func (e *httpError) Timeout() bool   { return e.timeout }
func (e *httpError) Temporary() bool { return true }

var errTimeout error = &httpError{err: "net/http: timeout awaiting response headers", timeout: true}

var errRequestCanceled = http2errRequestCanceled
var errRequestCanceledConn = errors.New("net/http: request canceled while waiting for connection") // TODO: unify?

func nop() {}

var (
	testHookEnterRoundTrip   = nop
	testHookWaitResLoop      = nop
	testHookRoundTripRetried = nop
	testHookPrePendingDial   = nop
	testHookPostPendingDial  = nop

	testHookMu                     sync.Locker = fakeLocker{} // guards following
	testHookReadLoopBeforeNextRead             = nop
)

func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err error) {
	testHookEnterRoundTrip()
	if !pc.t.replaceReqCanceler(req.cancelKey, pc.cancelRequest) {
		pc.t.putOrCloseIdleConn(pc)
		return nil, errRequestCanceled
	}
	pc.mu.Lock()
	pc.numExpectedResponses++
	headerFn := pc.mutateHeaderFunc
	pc.mu.Unlock()

	if headerFn != nil {
		headerFn(req.extraHeaders())
	}

	requestedGzip := false
	if !pc.t.DisableCompression &&
		req.Header.Get("Accept-Encoding") == "" &&
		req.Header.Get("Range") == "" &&

		requestedGzip = true
		req.extraHeaders().Set("Accept-Encoding", "gzip")
	}

	var continueCh chan struct{}
	if req.ProtoAtLeast(1, 1) && req.Body != nil && req.expectsContinue() {
		continueCh = make(chan struct{}, 1)
	}

	if pc.t.DisableKeepAlives &&
		!req.wantsClose() &&
		!isProtocolSwitchHeader(req.Header) {
		req.extraHeaders().Set("Connection", "close")
	}

	gone := make(chan struct{})
	defer close(gone)

	defer func() {
		if err != nil {
			pc.t.setReqCanceler(req.cancelKey, nil)
		}
	}()

	const debugRoundTrip = false

	startBytesWritten := pc.nwrite
	writeErrCh := make(chan error, 1)
	pc.writech <- writeRequest{req, writeErrCh, continueCh}

	resc := make(chan responseAndError)
	pc.reqch <- requestAndChan{
		req:        req.Request,
		cancelKey:  req.cancelKey,
		ch:         resc,
		addedGzip:  requestedGzip,
		continueCh: continueCh,
		callerGone: gone,
	}

	var respHeaderTimer <-chan time.Time
	cancelChan := req.Request.Cancel
	ctxDoneChan := req.Context().Done()
	pcClosed := pc.closech
	canceled := false
	for {
		testHookWaitResLoop()
		select {
		case err := <-writeErrCh:
			if debugRoundTrip {
				req.logf("writeErrCh resv: %T/%#v", err, err)
			}
			if err != nil {
				pc.close(fmt.Errorf("write error: %v", err))
				return nil, pc.mapRoundTripError(req, startBytesWritten, err)
			}
			if d := pc.t.ResponseHeaderTimeout; d > 0 {
				if debugRoundTrip {
					req.logf("starting timer for %v", d)
				}
				timer := time.NewTimer(d)
				defer timer.Stop() // prevent leaks
				respHeaderTimer = timer.C
			}
		case <-pcClosed:
			pcClosed = nil
			if canceled || pc.t.replaceReqCanceler(req.cancelKey, nil) {
				if debugRoundTrip {
					req.logf("closech recv: %T %#v", pc.closed, pc.closed)
				}
				return nil, pc.mapRoundTripError(req, startBytesWritten, pc.closed)
			}
		case <-respHeaderTimer:
			if debugRoundTrip {
				req.logf("timeout waiting for response headers.")
			}
			pc.close(errTimeout)
			return nil, errTimeout
		case re := <-resc:
			if (re.res == nil) == (re.err == nil) {
				panic(fmt.Sprintf("internal error: exactly one of res or err should be set; nil=%v", re.res == nil))
			}
			if debugRoundTrip {
				req.logf("resc recv: %p, %T/%#v", re.res, re.err, re.err)
			}
			if re.err != nil {
				return nil, pc.mapRoundTripError(req, startBytesWritten, re.err)
			}
			return re.res, nil
		case <-cancelChan:
			canceled = pc.t.cancelRequest(req.cancelKey, errRequestCanceled)
			cancelChan = nil
		case <-ctxDoneChan:
			canceled = pc.t.cancelRequest(req.cancelKey, req.Context().Err())
			cancelChan = nil
			ctxDoneChan = nil
		}
	}
}

type tLogKey struct{}

func (tr *transportRequest) logf(format string, args ...interface{}) {
	if logf, ok := tr.Request.Context().Value(tLogKey{}).(func(string, ...interface{})); ok {
		logf(time.Now().Format(time.RFC3339Nano)+": "+format, args...)
	}
}

func (pc *persistConn) markReused() {
	pc.mu.Lock()
	pc.reused = true
	pc.mu.Unlock()
}

func (pc *persistConn) close(err error) {
	pc.mu.Lock()
	defer pc.mu.Unlock()
	pc.closeLocked(err)
}

func (pc *persistConn) closeLocked(err error) {
	if err == nil {
		panic("nil error")
	}
	pc.broken = true
	if pc.closed == nil {
		pc.closed = err

		if pc.alt == nil {
			if err != errCallerOwnsConn {
				pc.conn.Close()
			}
			close(pc.closech)
		}
	}
	pc.mutateHeaderFunc = nil
}

var portMap = map[string]string{
	"http":   "80",
	"https":  "443",
	"socks5": "1080",
}

func canonicalAddr(url *url.URL) string {
	addr := url.Hostname()
	if v, err := idnaASCII(addr); err == nil {
		addr = v
	}
	port := url.Port()
	if port == "" {
		port = portMap[url.Scheme]
	}
	return net.JoinHostPort(addr, port)
}

type bodyEOFSignal struct {
	body         io.ReadCloser
	mu           sync.Mutex        // guards following 4 fields
	closed       bool              // whether Close has been called
	rerr         error             // sticky Read error
	fn           func(error) error // err will be nil on Read io.EOF
	earlyCloseFn func() error      // optional alt Close func used if io.EOF not seen
}

var errReadOnClosedResBody = errors.New("http: read on closed response body")

func (es *bodyEOFSignal) Read(p []byte) (n int, err error) {
	es.mu.Lock()
	closed, rerr := es.closed, es.rerr
	es.mu.Unlock()
	if closed {
		return 0, errReadOnClosedResBody
	}
	if rerr != nil {
		return 0, rerr
	}

	n, err = es.body.Read(p)
	if err != nil {
		es.mu.Lock()
		defer es.mu.Unlock()
		if es.rerr == nil {
			es.rerr = err
		}
		err = es.condfn(err)
	}
	return
}

func (es *bodyEOFSignal) Close() error {
	es.mu.Lock()
	defer es.mu.Unlock()
	if es.closed {
		return nil
	}
	es.closed = true
	if es.earlyCloseFn != nil && es.rerr != io.EOF {
		return es.earlyCloseFn()
	}
	err := es.body.Close()
	return es.condfn(err)
}

func (es *bodyEOFSignal) condfn(err error) error {
	if es.fn == nil {
		return err
	}
	err = es.fn(err)
	es.fn = nil
	return err
}

type gzipReader struct {
	_    incomparable
	body *bodyEOFSignal // underlying HTTP/1 response body framing
	zr   *gzip.Reader   // lazily-initialized gzip reader
	zerr error          // any error from gzip.NewReader; sticky
}

func (gz *gzipReader) Read(p []byte) (n int, err error) {
	if gz.zr == nil {
		if gz.zerr == nil {
			gz.zr, gz.zerr = gzip.NewReader(gz.body)
		}
		if gz.zerr != nil {
			return 0, gz.zerr
		}
	}

	gz.body.mu.Lock()
	if gz.body.closed {
		err = errReadOnClosedResBody
	}
	gz.body.mu.Unlock()

	if err != nil {
		return 0, err
	}
	return gz.zr.Read(p)
}

func (gz *gzipReader) Close() error {
	return gz.body.Close()
}

type tlsHandshakeTimeoutError struct{}

func (tlsHandshakeTimeoutError) Timeout() bool   { return true }
func (tlsHandshakeTimeoutError) Temporary() bool { return true }
func (tlsHandshakeTimeoutError) Error() string   { return "net/http: TLS handshake timeout" }

type fakeLocker struct{}

func (fakeLocker) Lock()   {}
func (fakeLocker) Unlock() {}

func cloneTLSConfig(cfg *tls.Config) *tls.Config {
	if cfg == nil {
		return &tls.Config{}
	}
	return cfg.Clone()
}

type connLRU struct {
	ll *list.List // list.Element.Value type is of *persistConn
	m  map[*persistConn]*list.Element
}

func (cl *connLRU) add(pc *persistConn) {
	if cl.ll == nil {
		cl.ll = list.New()
		cl.m = make(map[*persistConn]*list.Element)
	}
	ele := cl.ll.PushFront(pc)
	if _, ok := cl.m[pc]; ok {
		panic("persistConn was already in LRU")
	}
	cl.m[pc] = ele
}

func (cl *connLRU) removeOldest() *persistConn {
	ele := cl.ll.Back()
	pc := ele.Value.(*persistConn)
	cl.ll.Remove(ele)
	delete(cl.m, pc)
	return pc
}

func (cl *connLRU) remove(pc *persistConn) {
	if ele, ok := cl.m[pc]; ok {
		cl.ll.Remove(ele)
		delete(cl.m, pc)
	}
}

func (cl *connLRU) len() int {
	return len(cl.m)