Add /brotli endpoint (#27)

Parity with http://httpbin.org/ .  This is similar to #20 but uses a
Go-only implementation translated by c2go:

https://github.com/andybalholm/brotli

README.md

@@ -30,6 +30,7 @@ This way, you can write tests without relying on an external dependency like [ht
 - `/cache/:n` Sets a Cache-Control header for _n_ seconds.
 - `/gzip` Returns gzip-encoded data.
 - `/deflate` Returns deflate-encoded data.
+- `/brotli` Returns brotli-encoded data.
 - `/robots.txt` Returns some robots.txt rules.
 - `/deny` Denied by robots.txt file.
 - `/basic-auth/:user/:passwd` Challenges HTTP Basic Auth.

glide.yaml

@@ -4,6 +4,8 @@ import:
   version: ~1.3.0
 - package: github.com/pkg/errors
   version: ~0.8.0
+- package: github.com/andybalholm/brotli
+  version: ~1.0.0
 testImport:
 - package: github.com/stretchr/testify
   version: ~1.2.1

handlers.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/andybalholm/brotli"
 	"github.com/gorilla/mux"
 	"github.com/pkg/errors"
 )
@@ -64,6 +65,7 @@ func GetMux() *mux.Router {
 	r.HandleFunc(`/cache`, CacheHandler).Methods(http.MethodGet, http.MethodHead)
 	r.HandleFunc(`/cache/{n:[\d]+}`, SetCacheHandler).Methods(http.MethodGet, http.MethodHead)
 	r.HandleFunc(`/gzip`, GZIPHandler).Methods(http.MethodGet, http.MethodHead)
+	r.HandleFunc(`/brotli`, BrotliHandler).Methods(http.MethodGet, http.MethodHead)
 	r.HandleFunc(`/deflate`, DeflateHandler).Methods(http.MethodGet, http.MethodHead)
 	r.HandleFunc(`/html`, HTMLHandler).Methods(http.MethodGet, http.MethodHead)
 	r.HandleFunc(`/xml`, XMLHandler).Methods(http.MethodGet, http.MethodHead)
@@ -441,6 +443,25 @@ func DeflateHandler(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+// BrotliHandler returns a Brotli-encoded response
+func BrotliHandler(w http.ResponseWriter, r *http.Request) {
+	h, _, _ := net.SplitHostPort(r.RemoteAddr)
+
+	v := brotliResponse{
+		headersResponse: headersResponse{getHeaders(r)},
+		ipResponse:      ipResponse{h},
+		Compressed:      true,
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.Header().Add("Content-Encoding", "br")
+	ww := brotli.NewWriter(w)
+	defer ww.Close() // flush
+	if err := writeJSON(ww, v); err != nil {
+		writeErrorJSON(w, errors.Wrap(err, "failed to write json"))
+	}
+}
+
 // RobotsTXTHandler returns a robots.txt response.
 func RobotsTXTHandler(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "text/plain")

handlers_test.go

@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/ahmetb/go-httpbin"
+	"github.com/andybalholm/brotli"
 	"github.com/stretchr/testify/require"
 
 	"golang.org/x/net/html/charset"
@@ -570,6 +571,30 @@ func TestDeflate(t *testing.T) {
 	require.True(t, v.Deflated)
 }
 
+func TestBrotli(t *testing.T) {
+	srv := testServer()
+	defer srv.Close()
+
+	client := new(http.Client)
+	req, err := http.NewRequest("GET", srv.URL+"/brotli", nil)
+	require.Nil(t, err)
+
+	req.Header.Add("Accept-Encoding", "br")
+	resp, err := client.Do(req)
+	require.Nil(t, err)
+	defer resp.Body.Close()
+
+	require.EqualValues(t, "br", resp.Header.Get("Content-Encoding"))
+	require.EqualValues(t, "application/json", resp.Header.Get("Content-Type"))
+	zr := brotli.NewReader(resp.Body)
+
+	var v struct {
+		Compressed bool `json:"compressed"`
+	}
+	require.Nil(t, json.NewDecoder(zr).Decode(&v))
+	require.True(t, v.Compressed)
+}
+
 func TestRobotsTXT(t *testing.T) {
 	srv := testServer()
 	defer srv.Close()

types.go

@@ -54,6 +54,12 @@ type deflateResponse struct {
 	Deflated bool `json:"deflated"`
 }
 
+type brotliResponse struct {
+	headersResponse
+	ipResponse
+	Compressed bool `json:"compressed"`
+}
+
 type basicAuthResponse struct {
 	Authenticated bool   `json:"authenticated"`
 	User          string `json:"user"`