httpdebug/httpdebug.go

package httpdebug

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"strings"
	"unicode"
)

type Mode int

const (
	ModeOneline Mode = iota
	ModeTrimmed
	ModeFull
)

var ModeDefault = ModeOneline

// Wrap returns an http handler that serves h while logging requests and responses to stderr. It uses ModeDefault.
func Wrap(h http.Handler) http.Handler {
	return WrapMode(h, ModeDefault)
}

// WrapMode returns an http handler that serves h while logging requests and responses to stderr.
func WrapMode(h http.Handler, m Mode) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch m {
		case ModeTrimmed:
			serveTrimmed(h, w, r, 1024, 128)
		case ModeFull:
			serveTrimmed(h, w, r, 0, 0)
		case ModeOneline:
			buf := &bytes.Buffer{}
			rw := &rw{
				ResponseWriter: w,
				w:              buf,
			}

			h.ServeHTTP(rw, r)
			log.Println(r.Method, r.URL.Path, strings.Repeat("\t", 5-((len(r.Method)+len(r.URL.Path))/12)+1), rw.status, http.StatusText(rw.status), buf.Len(), "bytes", "\t", "("+w.Header().Get("Content-Type")+")")
		}
	})
}

func serveTrimmed(h http.Handler, w http.ResponseWriter, r *http.Request, trimAt, trimTo int64) {
	log.Println(r.Method, r.URL.Path, r.Proto)

	hBuf := &bytes.Buffer{}
	r.Header.Write(hBuf)
	log.Println(hBuf.String())

	requestBuf := &bytes.Buffer{}
	responseBuf := &bytes.Buffer{}

	defer r.Body.Close()

	r.Body = ioutil.NopCloser(io.TeeReader(r.Body, requestBuf))

	rw := &rw{
		ResponseWriter: w,
		w:              responseBuf,
	}

	h.ServeHTTP(rw, r)

	if trimAt > 0 && trimTo > 0 {
		if int64(requestBuf.Len()) > trimAt {
			trimmed := &bytes.Buffer{}
			io.CopyN(trimmed, requestBuf, trimTo)
			requestBuf = trimmed
		}
	}

	log.Println()
	log.Println(logsafe(requestBuf.String()))

	log.Println(rw.status)

	hBuf.Reset()
	w.Header().Write(hBuf)
	log.Println(hBuf.String())

	if trimTo > 0 {
		responseBuf = trim(responseBuf, int(trimTo))
	}

	log.Println()
	log.Println(logsafe(responseBuf.String()))
}

type rw struct {
	http.ResponseWriter
	w      io.Writer
	status int
}

func (rw *rw) WriteHeader(s int) {
	rw.status = s
	rw.ResponseWriter.WriteHeader(s)
}

func (rw *rw) Write(b []byte) (int, error) {
	if rw.status == 0 {
		rw.WriteHeader(http.StatusOK)
	}

	if rw.w != nil {
		rw.w.Write(b)
	}
	return rw.ResponseWriter.Write(b)
}

func logsafe(str string) string {
	buf := &bytes.Buffer{}

	for _, r := range str {
		if unicode.IsPrint(r) || unicode.IsSpace(r) {
			fmt.Fprintf(buf, "%c", r)
		} else {
			fmt.Fprintf(buf, "%x", r)
		}
	}

	return buf.String()
}

func trim(b *bytes.Buffer, n int) *bytes.Buffer {
	trimmed := &bytes.Buffer{}
	io.CopyN(trimmed, b, int64(n))
	return trimmed
}