Initial draft of shifting from chi to gorilla/mux

middleware/logger.go

@@ -0,0 +1,172 @@
+package middleware
+
+import (
+	"bytes"
+	"context"
+	"log"
+	"net/http"
+	"os"
+	"runtime"
+	"time"
+)
+
+var (
+	// LogEntryCtxKey is the context.Context key to store the request log entry.
+	LogEntryCtxKey = &contextKey{"LogEntry"}
+
+	// DefaultLogger is called by the Logger middleware handler to log each request.
+	// Its made a package-level variable so that it can be reconfigured for custom
+	// logging configurations.
+	DefaultLogger func(next http.Handler) http.Handler
+)
+
+// Logger is a middleware that logs the start and end of each request, along
+// with some useful data about what was requested, what the response status was,
+// and how long it took to return. When standard output is a TTY, Logger will
+// print in color, otherwise it will print in black and white. Logger prints a
+// request ID if one is provided.
+//
+// Alternatively, look at https://github.com/goware/httplog for a more in-depth
+// http logger with structured logging support.
+//
+// IMPORTANT NOTE: Logger should go before any other middleware that may change
+// the response, such as middleware.Recoverer. Example:
+//
+//	r := chi.NewRouter()
+//	r.Use(middleware.Logger)        // <--<< Logger should come before Recoverer
+//	r.Use(middleware.Recoverer)
+//	r.Get("/", handler)
+func Logger(next http.Handler) http.Handler {
+	return DefaultLogger(next)
+}
+
+// RequestLogger returns a logger handler using a custom LogFormatter.
+func RequestLogger(f LogFormatter) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		fn := func(w http.ResponseWriter, r *http.Request) {
+			entry := f.NewLogEntry(r)
+			ww := NewWrapResponseWriter(w, r.ProtoMajor)
+
+			t1 := time.Now()
+			defer func() {
+				entry.Write(ww.Status(), ww.BytesWritten(), ww.Header(), time.Since(t1), nil)
+			}()
+
+			next.ServeHTTP(ww, WithLogEntry(r, entry))
+		}
+		return http.HandlerFunc(fn)
+	}
+}
+
+// LogFormatter initiates the beginning of a new LogEntry per request.
+// See DefaultLogFormatter for an example implementation.
+type LogFormatter interface {
+	NewLogEntry(r *http.Request) LogEntry
+}
+
+// LogEntry records the final log when a request completes.
+// See defaultLogEntry for an example implementation.
+type LogEntry interface {
+	Write(status, bytes int, header http.Header, elapsed time.Duration, extra interface{})
+	Panic(v interface{}, stack []byte)
+}
+
+// GetLogEntry returns the in-context LogEntry for a request.
+func GetLogEntry(r *http.Request) LogEntry {
+	entry, _ := r.Context().Value(LogEntryCtxKey).(LogEntry)
+	return entry
+}
+
+// WithLogEntry sets the in-context LogEntry for a request.
+func WithLogEntry(r *http.Request, entry LogEntry) *http.Request {
+	r = r.WithContext(context.WithValue(r.Context(), LogEntryCtxKey, entry))
+	return r
+}
+
+// LoggerInterface accepts printing to stdlib logger or compatible logger.
+type LoggerInterface interface {
+	Print(v ...interface{})
+}
+
+// DefaultLogFormatter is a simple logger that implements a LogFormatter.
+type DefaultLogFormatter struct {
+	Logger  LoggerInterface
+	NoColor bool
+}
+
+// NewLogEntry creates a new LogEntry for the request.
+func (l *DefaultLogFormatter) NewLogEntry(r *http.Request) LogEntry {
+	useColor := !l.NoColor
+	entry := &defaultLogEntry{
+		DefaultLogFormatter: l,
+		request:             r,
+		buf:                 &bytes.Buffer{},
+		useColor:            useColor,
+	}
+
+	reqID := GetReqID(r.Context())
+	if reqID != "" {
+		cW(entry.buf, useColor, nYellow, "[%s] ", reqID)
+	}
+	cW(entry.buf, useColor, nCyan, "\"")
+	cW(entry.buf, useColor, bMagenta, "%s ", r.Method)
+
+	scheme := "http"
+	if r.TLS != nil {
+		scheme = "https"
+	}
+	cW(entry.buf, useColor, nCyan, "%s://%s%s %s\" ", scheme, r.Host, r.RequestURI, r.Proto)
+
+	entry.buf.WriteString("from ")
+	entry.buf.WriteString(r.RemoteAddr)
+	entry.buf.WriteString(" - ")
+
+	return entry
+}
+
+type defaultLogEntry struct {
+	*DefaultLogFormatter
+	request  *http.Request
+	buf      *bytes.Buffer
+	useColor bool
+}
+
+func (l *defaultLogEntry) Write(status, bytes int, header http.Header, elapsed time.Duration, extra interface{}) {
+	switch {
+	case status < 200:
+		cW(l.buf, l.useColor, bBlue, "%03d", status)
+	case status < 300:
+		cW(l.buf, l.useColor, bGreen, "%03d", status)
+	case status < 400:
+		cW(l.buf, l.useColor, bCyan, "%03d", status)
+	case status < 500:
+		cW(l.buf, l.useColor, bYellow, "%03d", status)
+	default:
+		cW(l.buf, l.useColor, bRed, "%03d", status)
+	}
+
+	cW(l.buf, l.useColor, bBlue, " %dB", bytes)
+
+	l.buf.WriteString(" in ")
+	if elapsed < 500*time.Millisecond {
+		cW(l.buf, l.useColor, nGreen, "%s", elapsed)
+	} else if elapsed < 5*time.Second {
+		cW(l.buf, l.useColor, nYellow, "%s", elapsed)
+	} else {
+		cW(l.buf, l.useColor, nRed, "%s", elapsed)
+	}
+
+	l.Logger.Print(l.buf.String())
+}
+
+func (l *defaultLogEntry) Panic(v interface{}, stack []byte) {
+	PrintPrettyStack(v)
+}
+
+func init() {
+	color := true
+	if runtime.GOOS == "windows" {
+		color = false
+	}
+	DefaultLogger = RequestLogger(&DefaultLogFormatter{Logger: log.New(os.Stdout, "", log.LstdFlags), NoColor: !color})
+}

middleware/middleware.go

@@ -0,0 +1,23 @@
+package middleware
+
+import "net/http"
+
+// New will create a new middleware handler from a http.Handler.
+func New(h http.Handler) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			h.ServeHTTP(w, r)
+		})
+	}
+}
+
+// contextKey is a value for use with context.WithValue. It's used as
+// a pointer so it fits in an interface{} without allocation. This technique
+// for defining context keys was copied from Go 1.7's new use of context in net/http.
+type contextKey struct {
+	name string
+}
+
+func (k *contextKey) String() string {
+	return "chi/middleware context value " + k.name
+}

middleware/realip.go

@@ -0,0 +1,56 @@
+package middleware
+
+// Ported from Chi's middleware, source:
+// https://github.com/go-chi/chi/blob/master/middleware/realip.go
+
+import (
+	"net"
+	"net/http"
+	"strings"
+)
+
+var trueClientIP = http.CanonicalHeaderKey("True-Client-IP")
+var xForwardedFor = http.CanonicalHeaderKey("X-Forwarded-For")
+var xRealIP = http.CanonicalHeaderKey("X-Real-IP")
+
+// RealIP is a middleware that sets a http.Request's RemoteAddr to the results
+// of parsing either the True-Client-IP, X-Real-IP or the X-Forwarded-For headers
+// (in that order).
+//
+// This middleware should be inserted fairly early in the middleware stack to
+// ensure that subsequent layers (e.g., request loggers) which examine the
+// RemoteAddr will see the intended value.
+//
+// You should only use this middleware if you can trust the headers passed to
+// you (in particular, the three headers this middleware uses), for example
+// because you have placed a reverse proxy like HAProxy or nginx in front of
+// chi. If your reverse proxies are configured to pass along arbitrary header
+// values from the client, or if you use this middleware without a reverse
+// proxy, malicious clients will be able to make you very sad (or, depending on
+// how you're using RemoteAddr, vulnerable to an attack of some sort).
+func RealIP(h http.Handler) http.Handler {
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		if rip := realIP(r); rip != "" {
+			r.RemoteAddr = rip
+		}
+		h.ServeHTTP(w, r)
+	}
+
+	return http.HandlerFunc(fn)
+}
+
+func realIP(r *http.Request) string {
+	var ip string
+
+	if tcip := r.Header.Get(trueClientIP); tcip != "" {
+		ip = tcip
+	} else if xrip := r.Header.Get(xRealIP); xrip != "" {
+		ip = xrip
+	} else if xff := r.Header.Get(xForwardedFor); xff != "" {
+		ip, _, _ = strings.Cut(xff, ",")
+	}
+	if ip == "" || net.ParseIP(ip) == nil {
+		return ""
+	}
+	return ip
+}

middleware/recoverer.go

@@ -0,0 +1,203 @@
+package middleware
+
+// The original work was derived from Chi's middleware, source:
+// https://github.com/go-chi/chi/blob/master/middleware/recoverer.go
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"runtime/debug"
+	"strings"
+)
+
+// Recoverer is a middleware that recovers from panics, logs the panic (and a
+// backtrace), and returns a HTTP 500 (Internal Server Error) status if
+// possible. Recoverer prints a request ID if one is provided.
+//
+// Alternatively, look at https://github.com/go-chi/httplog middleware pkgs.
+func Recoverer(next http.Handler) http.Handler {
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		defer func() {
+			if rvr := recover(); rvr != nil {
+				if rvr == http.ErrAbortHandler {
+					// we don't recover http.ErrAbortHandler so the response
+					// to the client is aborted, this should not be logged
+					panic(rvr)
+				}
+
+				logEntry := GetLogEntry(r)
+				if logEntry != nil {
+					logEntry.Panic(rvr, debug.Stack())
+				} else {
+					PrintPrettyStack(rvr)
+				}
+
+				if r.Header.Get("Connection") != "Upgrade" {
+					w.WriteHeader(http.StatusInternalServerError)
+				}
+			}
+		}()
+
+		next.ServeHTTP(w, r)
+	}
+
+	return http.HandlerFunc(fn)
+}
+
+// for ability to test the PrintPrettyStack function
+var recovererErrorWriter io.Writer = os.Stderr
+
+func PrintPrettyStack(rvr interface{}) {
+	debugStack := debug.Stack()
+	s := prettyStack{}
+	out, err := s.parse(debugStack, rvr)
+	if err == nil {
+		recovererErrorWriter.Write(out)
+	} else {
+		// print stdlib output as a fallback
+		os.Stderr.Write(debugStack)
+	}
+}
+
+type prettyStack struct {
+}
+
+func (s prettyStack) parse(debugStack []byte, rvr interface{}) ([]byte, error) {
+	var err error
+	useColor := true
+	buf := &bytes.Buffer{}
+
+	cW(buf, false, bRed, "\n")
+	cW(buf, useColor, bCyan, " panic: ")
+	cW(buf, useColor, bBlue, "%v", rvr)
+	cW(buf, false, bWhite, "\n \n")
+
+	// process debug stack info
+	stack := strings.Split(string(debugStack), "\n")
+	lines := []string{}
+
+	// locate panic line, as we may have nested panics
+	for i := len(stack) - 1; i > 0; i-- {
+		lines = append(lines, stack[i])
+		if strings.HasPrefix(stack[i], "panic(") {
+			lines = lines[0 : len(lines)-2] // remove boilerplate
+			break
+		}
+	}
+
+	// reverse
+	for i := len(lines)/2 - 1; i >= 0; i-- {
+		opp := len(lines) - 1 - i
+		lines[i], lines[opp] = lines[opp], lines[i]
+	}
+
+	// decorate
+	for i, line := range lines {
+		lines[i], err = s.decorateLine(line, useColor, i)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	for _, l := range lines {
+		fmt.Fprintf(buf, "%s", l)
+	}
+	return buf.Bytes(), nil
+}
+
+func (s prettyStack) decorateLine(line string, useColor bool, num int) (string, error) {
+	line = strings.TrimSpace(line)
+	if strings.HasPrefix(line, "\t") || strings.Contains(line, ".go:") {
+		return s.decorateSourceLine(line, useColor, num)
+	}
+	if strings.HasSuffix(line, ")") {
+		return s.decorateFuncCallLine(line, useColor, num)
+	}
+	if strings.HasPrefix(line, "\t") {
+		return strings.Replace(line, "\t", "      ", 1), nil
+	}
+	return fmt.Sprintf("    %s\n", line), nil
+}
+
+func (s prettyStack) decorateFuncCallLine(line string, useColor bool, num int) (string, error) {
+	idx := strings.LastIndex(line, "(")
+	if idx < 0 {
+		return "", errors.New("not a func call line")
+	}
+
+	buf := &bytes.Buffer{}
+	pkg := line[0:idx]
+	// addr := line[idx:]
+	method := ""
+
+	if idx := strings.LastIndex(pkg, string(os.PathSeparator)); idx < 0 {
+		if idx := strings.Index(pkg, "."); idx > 0 {
+			method = pkg[idx:]
+			pkg = pkg[0:idx]
+		}
+	} else {
+		method = pkg[idx+1:]
+		pkg = pkg[0 : idx+1]
+		if idx := strings.Index(method, "."); idx > 0 {
+			pkg += method[0:idx]
+			method = method[idx:]
+		}
+	}
+	pkgColor := nYellow
+	methodColor := bGreen
+
+	if num == 0 {
+		cW(buf, useColor, bRed, " -> ")
+		pkgColor = bMagenta
+		methodColor = bRed
+	} else {
+		cW(buf, useColor, bWhite, "    ")
+	}
+	cW(buf, useColor, pkgColor, "%s", pkg)
+	cW(buf, useColor, methodColor, "%s\n", method)
+	// cW(buf, useColor, nBlack, "%s", addr)
+	return buf.String(), nil
+}
+
+func (s prettyStack) decorateSourceLine(line string, useColor bool, num int) (string, error) {
+	idx := strings.LastIndex(line, ".go:")
+	if idx < 0 {
+		return "", errors.New("not a source line")
+	}
+
+	buf := &bytes.Buffer{}
+	path := line[0 : idx+3]
+	lineno := line[idx+3:]
+
+	idx = strings.LastIndex(path, string(os.PathSeparator))
+	dir := path[0 : idx+1]
+	file := path[idx+1:]
+
+	idx = strings.Index(lineno, " ")
+	if idx > 0 {
+		lineno = lineno[0:idx]
+	}
+	fileColor := bCyan
+	lineColor := bGreen
+
+	if num == 1 {
+		cW(buf, useColor, bRed, " ->   ")
+		fileColor = bRed
+		lineColor = bMagenta
+	} else {
+		cW(buf, false, bWhite, "      ")
+	}
+	cW(buf, useColor, bWhite, "%s", dir)
+	cW(buf, useColor, fileColor, "%s", file)
+	cW(buf, useColor, lineColor, "%s", lineno)
+	if num == 1 {
+		cW(buf, false, bWhite, "\n")
+	}
+	cW(buf, false, bWhite, "\n")
+
+	return buf.String(), nil
+}

middleware/request_id.go

@@ -0,0 +1,96 @@
+package middleware
+
+// Ported from chi's middleware, source:
+// https://github.com/go-chi/chi/blob/master/middleware/request_id.go
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"net/http"
+	"os"
+	"strings"
+	"sync/atomic"
+)
+
+// Key to use when setting the request ID.
+type ctxKeyRequestID int
+
+// RequestIDKey is the key that holds the unique request ID in a request context.
+const RequestIDKey ctxKeyRequestID = 0
+
+// RequestIDHeader is the name of the HTTP Header which contains the request id.
+// Exported so that it can be changed by developers
+var RequestIDHeader = "X-Request-Id"
+
+var prefix string
+var reqid atomic.Uint64
+
+// A quick note on the statistics here: we're trying to calculate the chance that
+// two randomly generated base62 prefixes will collide. We use the formula from
+// http://en.wikipedia.org/wiki/Birthday_problem
+//
+// P[m, n] \approx 1 - e^{-m^2/2n}
+//
+// We ballpark an upper bound for $m$ by imagining (for whatever reason) a server
+// that restarts every second over 10 years, for $m = 86400 * 365 * 10 = 315360000$
+//
+// For a $k$ character base-62 identifier, we have $n(k) = 62^k$
+//
+// Plugging this in, we find $P[m, n(10)] \approx 5.75%$, which is good enough for
+// our purposes, and is surely more than anyone would ever need in practice -- a
+// process that is rebooted a handful of times a day for a hundred years has less
+// than a millionth of a percent chance of generating two colliding IDs.
+
+func init() {
+	hostname, err := os.Hostname()
+	if hostname == "" || err != nil {
+		hostname = "localhost"
+	}
+	var buf [12]byte
+	var b64 string
+	for len(b64) < 10 {
+		rand.Read(buf[:])
+		b64 = base64.StdEncoding.EncodeToString(buf[:])
+		b64 = strings.NewReplacer("+", "", "/", "").Replace(b64)
+	}
+
+	prefix = fmt.Sprintf("%s/%s", hostname, b64[0:10])
+}
+
+// RequestID is a middleware that injects a request ID into the context of each
+// request. A request ID is a string of the form "host.example.com/random-0001",
+// where "random" is a base62 random string that uniquely identifies this go
+// process, and where the last number is an atomically incremented request
+// counter.
+func RequestID(next http.Handler) http.Handler {
+	fn := func(w http.ResponseWriter, r *http.Request) {
+		ctx := r.Context()
+		requestID := r.Header.Get(RequestIDHeader)
+		if requestID == "" {
+			myid := reqid.Add(1)
+			requestID = fmt.Sprintf("%s-%06d", prefix, myid)
+		}
+		ctx = context.WithValue(ctx, RequestIDKey, requestID)
+		next.ServeHTTP(w, r.WithContext(ctx))
+	}
+	return http.HandlerFunc(fn)
+}
+
+// GetReqID returns a request ID from the given context if one is present.
+// Returns the empty string if a request ID cannot be found.
+func GetReqID(ctx context.Context) string {
+	if ctx == nil {
+		return ""
+	}
+	if reqID, ok := ctx.Value(RequestIDKey).(string); ok {
+		return reqID
+	}
+	return ""
+}
+
+// NextRequestID generates the next request ID in the sequence.
+func NextRequestID() uint64 {
+	return reqid.Add(1)
+}

middleware/terminal.go

@@ -0,0 +1,63 @@
+package middleware
+
+// Ported from Goji's middleware, source:
+// https://github.com/zenazn/goji/tree/master/web/middleware
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+var (
+	// Normal colors
+	nBlack   = []byte{'\033', '[', '3', '0', 'm'}
+	nRed     = []byte{'\033', '[', '3', '1', 'm'}
+	nGreen   = []byte{'\033', '[', '3', '2', 'm'}
+	nYellow  = []byte{'\033', '[', '3', '3', 'm'}
+	nBlue    = []byte{'\033', '[', '3', '4', 'm'}
+	nMagenta = []byte{'\033', '[', '3', '5', 'm'}
+	nCyan    = []byte{'\033', '[', '3', '6', 'm'}
+	nWhite   = []byte{'\033', '[', '3', '7', 'm'}
+	// Bright colors
+	bBlack   = []byte{'\033', '[', '3', '0', ';', '1', 'm'}
+	bRed     = []byte{'\033', '[', '3', '1', ';', '1', 'm'}
+	bGreen   = []byte{'\033', '[', '3', '2', ';', '1', 'm'}
+	bYellow  = []byte{'\033', '[', '3', '3', ';', '1', 'm'}
+	bBlue    = []byte{'\033', '[', '3', '4', ';', '1', 'm'}
+	bMagenta = []byte{'\033', '[', '3', '5', ';', '1', 'm'}
+	bCyan    = []byte{'\033', '[', '3', '6', ';', '1', 'm'}
+	bWhite   = []byte{'\033', '[', '3', '7', ';', '1', 'm'}
+
+	reset = []byte{'\033', '[', '0', 'm'}
+)
+
+var IsTTY bool
+
+func init() {
+	// This is sort of cheating: if stdout is a character device, we assume
+	// that means it's a TTY. Unfortunately, there are many non-TTY
+	// character devices, but fortunately stdout is rarely set to any of
+	// them.
+	//
+	// We could solve this properly by pulling in a dependency on
+	// code.google.com/p/go.crypto/ssh/terminal, for instance, but as a
+	// heuristic for whether to print in color or in black-and-white, I'd
+	// really rather not.
+	fi, err := os.Stdout.Stat()
+	if err == nil {
+		m := os.ModeDevice | os.ModeCharDevice
+		IsTTY = fi.Mode()&m == m
+	}
+}
+
+// colorWrite
+func cW(w io.Writer, useColor bool, color []byte, s string, args ...interface{}) {
+	if IsTTY && useColor {
+		w.Write(color)
+	}
+	fmt.Fprintf(w, s, args...)
+	if IsTTY && useColor {
+		w.Write(reset)
+	}
+}

middleware/wrap_writer.go

@@ -0,0 +1,241 @@
+package middleware
+
+// The original work was derived from Goji's middleware, source:
+// https://github.com/zenazn/goji/tree/master/web/middleware
+
+import (
+	"bufio"
+	"io"
+	"net"
+	"net/http"
+)
+
+// NewWrapResponseWriter wraps an http.ResponseWriter, returning a proxy that allows you to
+// hook into various parts of the response process.
+func NewWrapResponseWriter(w http.ResponseWriter, protoMajor int) WrapResponseWriter {
+	_, fl := w.(http.Flusher)
+
+	bw := basicWriter{ResponseWriter: w}
+
+	if protoMajor == 2 {
+		_, ps := w.(http.Pusher)
+		if fl && ps {
+			return &http2FancyWriter{bw}
+		}
+	} else {
+		_, hj := w.(http.Hijacker)
+		_, rf := w.(io.ReaderFrom)
+		if fl && hj && rf {
+			return &httpFancyWriter{bw}
+		}
+		if fl && hj {
+			return &flushHijackWriter{bw}
+		}
+		if hj {
+			return &hijackWriter{bw}
+		}
+	}
+
+	if fl {
+		return &flushWriter{bw}
+	}
+
+	return &bw
+}
+
+// WrapResponseWriter is a proxy around an http.ResponseWriter that allows you to hook
+// into various parts of the response process.
+type WrapResponseWriter interface {
+	http.ResponseWriter
+	// Status returns the HTTP status of the request, or 0 if one has not
+	// yet been sent.
+	Status() int
+	// BytesWritten returns the total number of bytes sent to the client.
+	BytesWritten() int
+	// Tee causes the response body to be written to the given io.Writer in
+	// addition to proxying the writes through. Only one io.Writer can be
+	// tee'd to at once: setting a second one will overwrite the first.
+	// Writes will be sent to the proxy before being written to this
+	// io.Writer. It is illegal for the tee'd writer to be modified
+	// concurrently with writes.
+	Tee(io.Writer)
+	// Unwrap returns the original proxied target.
+	Unwrap() http.ResponseWriter
+	// Discard causes all writes to the original ResponseWriter be discarded,
+	// instead writing only to the tee'd writer if it's set.
+	// The caller is responsible for calling WriteHeader and Write on the
+	// original ResponseWriter once the processing is done.
+	Discard()
+}
+
+// basicWriter wraps a http.ResponseWriter that implements the minimal
+// http.ResponseWriter interface.
+type basicWriter struct {
+	http.ResponseWriter
+	tee         io.Writer
+	code        int
+	bytes       int
+	wroteHeader bool
+	discard     bool
+}
+
+func (b *basicWriter) WriteHeader(code int) {
+	if code >= 100 && code <= 199 && code != http.StatusSwitchingProtocols {
+		if !b.discard {
+			b.ResponseWriter.WriteHeader(code)
+		}
+	} else if !b.wroteHeader {
+		b.code = code
+		b.wroteHeader = true
+		if !b.discard {
+			b.ResponseWriter.WriteHeader(code)
+		}
+	}
+}
+
+func (b *basicWriter) Write(buf []byte) (n int, err error) {
+	b.maybeWriteHeader()
+	if !b.discard {
+		n, err = b.ResponseWriter.Write(buf)
+		if b.tee != nil {
+			_, err2 := b.tee.Write(buf[:n])
+			// Prefer errors generated by the proxied writer.
+			if err == nil {
+				err = err2
+			}
+		}
+	} else if b.tee != nil {
+		n, err = b.tee.Write(buf)
+	} else {
+		n, err = io.Discard.Write(buf)
+	}
+	b.bytes += n
+	return n, err
+}
+
+func (b *basicWriter) maybeWriteHeader() {
+	if !b.wroteHeader {
+		b.WriteHeader(http.StatusOK)
+	}
+}
+
+func (b *basicWriter) Status() int {
+	return b.code
+}
+
+func (b *basicWriter) BytesWritten() int {
+	return b.bytes
+}
+
+func (b *basicWriter) Tee(w io.Writer) {
+	b.tee = w
+}
+
+func (b *basicWriter) Unwrap() http.ResponseWriter {
+	return b.ResponseWriter
+}
+
+func (b *basicWriter) Discard() {
+	b.discard = true
+}
+
+// flushWriter ...
+type flushWriter struct {
+	basicWriter
+}
+
+func (f *flushWriter) Flush() {
+	f.wroteHeader = true
+	fl := f.basicWriter.ResponseWriter.(http.Flusher)
+	fl.Flush()
+}
+
+var _ http.Flusher = &flushWriter{}
+
+// hijackWriter ...
+type hijackWriter struct {
+	basicWriter
+}
+
+func (f *hijackWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	hj := f.basicWriter.ResponseWriter.(http.Hijacker)
+	return hj.Hijack()
+}
+
+var _ http.Hijacker = &hijackWriter{}
+
+// flushHijackWriter ...
+type flushHijackWriter struct {
+	basicWriter
+}
+
+func (f *flushHijackWriter) Flush() {
+	f.wroteHeader = true
+	fl := f.basicWriter.ResponseWriter.(http.Flusher)
+	fl.Flush()
+}
+
+func (f *flushHijackWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	hj := f.basicWriter.ResponseWriter.(http.Hijacker)
+	return hj.Hijack()
+}
+
+var _ http.Flusher = &flushHijackWriter{}
+var _ http.Hijacker = &flushHijackWriter{}
+
+// httpFancyWriter is a HTTP writer that additionally satisfies
+// http.Flusher, http.Hijacker, and io.ReaderFrom. It exists for the common case
+// of wrapping the http.ResponseWriter that package http gives you, in order to
+// make the proxied object support the full method set of the proxied object.
+type httpFancyWriter struct {
+	basicWriter
+}
+
+func (f *httpFancyWriter) Flush() {
+	f.wroteHeader = true
+	fl := f.basicWriter.ResponseWriter.(http.Flusher)
+	fl.Flush()
+}
+
+func (f *httpFancyWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	hj := f.basicWriter.ResponseWriter.(http.Hijacker)
+	return hj.Hijack()
+}
+
+func (f *http2FancyWriter) Push(target string, opts *http.PushOptions) error {
+	return f.basicWriter.ResponseWriter.(http.Pusher).Push(target, opts)
+}
+
+func (f *httpFancyWriter) ReadFrom(r io.Reader) (int64, error) {
+	if f.basicWriter.tee != nil {
+		n, err := io.Copy(&f.basicWriter, r)
+		f.basicWriter.bytes += int(n)
+		return n, err
+	}
+	rf := f.basicWriter.ResponseWriter.(io.ReaderFrom)
+	f.basicWriter.maybeWriteHeader()
+	n, err := rf.ReadFrom(r)
+	f.basicWriter.bytes += int(n)
+	return n, err
+}
+
+var _ http.Flusher = &httpFancyWriter{}
+var _ http.Hijacker = &httpFancyWriter{}
+var _ http.Pusher = &http2FancyWriter{}
+var _ io.ReaderFrom = &httpFancyWriter{}
+
+// http2FancyWriter is a HTTP2 writer that additionally satisfies
+// http.Flusher, and io.ReaderFrom. It exists for the common case
+// of wrapping the http.ResponseWriter that package http gives you, in order to
+// make the proxied object support the full method set of the proxied object.
+type http2FancyWriter struct {
+	basicWriter
+}
+
+func (f *http2FancyWriter) Flush() {
+	f.wroteHeader = true
+	fl := f.basicWriter.ResponseWriter.(http.Flusher)
+	fl.Flush()
+}
+
+var _ http.Flusher = &http2FancyWriter{}