From 455a570e9c01687d07fd86c908bbcb2ebc2eefd6 Mon Sep 17 00:00:00 2001
From: Barna Csorogi <barnacs@justletit.be>
Date: Fri, 31 Aug 2018 23:28:46 +0800
Subject: [PATCH] decompress brotli payload before minifying

---
 transcoder/zip.go | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/transcoder/zip.go b/transcoder/zip.go
index 70c2b99..629bbcc 100644
--- a/transcoder/zip.go
+++ b/transcoder/zip.go
@@ -2,17 +2,19 @@ package transcoder
 
 import (
 	"compress/gzip"
-	"github.com/barnacs/compy/proxy"
-	brotlienc "gopkg.in/kothar/brotli-go.v0/enc"
 	"net/http"
 	"strings"
+
+	"github.com/barnacs/compy/proxy"
+	brotlidec "gopkg.in/kothar/brotli-go.v0/dec"
+	brotlienc "gopkg.in/kothar/brotli-go.v0/enc"
 )
 
 type Zip struct {
 	proxy.Transcoder
 	BrotliCompressionLevel int
 	GzipCompressionLevel   int
-	SkipGzipped            bool
+	SkipCompressed         bool
 }
 
 func (t *Zip) Transcode(w *proxy.ResponseWriter, r *proxy.ResponseReader, headers http.Header) error {
@@ -28,7 +30,7 @@ func (t *Zip) Transcode(w *proxy.ResponseWriter, r *proxy.ResponseReader, header
 	}
 
 	// always gunzip if the client supports Brotli
-	if r.Header().Get("Content-Encoding") == "gzip" && (shouldBrotli || !t.SkipGzipped) {
+	if r.Header().Get("Content-Encoding") == "gzip" && (shouldBrotli || !t.SkipCompressed) {
 		gzr, err := gzip.NewReader(r.Reader)
 		if err != nil {
 			return err
@@ -39,6 +41,14 @@ func (t *Zip) Transcode(w *proxy.ResponseWriter, r *proxy.ResponseReader, header
 		w.Header().Del("Content-Encoding")
 	}
 
+	if r.Header().Get("Content-Encoding") == "br" && !t.SkipCompressed {
+		brr := brotlidec.NewBrotliReader(r.Reader)
+		defer brr.Close()
+		r.Reader = brr
+		r.Header().Del("Content-Encoding")
+		w.Header().Del("Content-Encoding")
+	}
+
 	if shouldBrotli && compress(r) {
 		params := brotlienc.NewBrotliParams()
 		params.SetQuality(t.BrotliCompressionLevel)