From 28cfcd02340acbea46adff247017300d96db3a39 Mon Sep 17 00:00:00 2001
From: Carlo Alberto Ferraris <cafxx@strayorange.com>
Date: Thu, 7 Sep 2023 01:02:31 +0000
Subject: [PATCH] handle multiple accept-encoding headers

---
 accepts.go      | 14 ++++++++------
 adapter.go      |  2 +-
 adapter_test.go | 42 +++++++++++++++++++++++++++++++++---------
 3 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/accepts.go b/accepts.go
index 147086e..ccb8d4e 100644
--- a/accepts.go
+++ b/accepts.go
@@ -39,14 +39,16 @@ func acceptedCompression(accept codings, comps comps) []string {
 // Errors encountered during parsing the codings are ignored.
 //
 // See: http://tools.ietf.org/html/rfc2616#section-14.3.
-func parseEncodings(s string) codings {
+func parseEncodings(vv []string) codings {
 	c := make(codings)
-	for _, ss := range strings.Split(s, ",") {
-		coding, qvalue := parseCoding(ss)
-		if coding == "" {
-			continue
+	for _, v := range vv {
+		for _, sv := range strings.Split(v, ",") {
+			coding, qvalue := parseCoding(sv)
+			if coding == "" {
+				continue
+			}
+			c[coding] = qvalue
 		}
-		c[coding] = qvalue
 	}
 	return c
 }
diff --git a/adapter.go b/adapter.go
index 3da818b..19c10c7 100644
--- a/adapter.go
+++ b/adapter.go
@@ -71,7 +71,7 @@ func Adapter(opts ...Option) (func(http.Handler) http.Handler, error) {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			addVaryHeader(w.Header(), acceptEncoding)
 
-			accept := parseEncodings(r.Header.Get(acceptEncoding))
+			accept := parseEncodings(r.Header.Values(acceptEncoding))
 			common := acceptedCompression(accept, c.compressor)
 			if len(common) == 0 {
 				h.ServeHTTP(w, r)
diff --git a/adapter_test.go b/adapter_test.go
index a133cb1..1c67710 100644
--- a/adapter_test.go
+++ b/adapter_test.go
@@ -6,11 +6,11 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
+	"os"
 	"strconv"
 	"testing"
 
@@ -59,8 +59,32 @@ func TestParseEncodings(t *testing.T) {
 	}
 
 	for eg, exp := range examples {
-		act := parseEncodings(eg)
-		assert.Equal(t, exp, act)
+		t.Run(eg, func(t *testing.T) {
+			act := parseEncodings([]string{eg})
+			assert.Equal(t, exp, act)
+		})
+	}
+}
+
+func TestParseEncodings2(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		accept []string
+		parsed codings
+	}{
+		{[]string{"gzip"}, codings{"gzip": 1}},
+		{[]string{"gzip,gzip"}, codings{"gzip": 1}},
+		{[]string{"gzip,gzip;q=0.8"}, codings{"gzip": 0.8}},
+		{[]string{"gzip,gzip;q=0"}, codings{"gzip": 0}},
+		{[]string{"gzip,br"}, codings{"gzip": 1, "br": 1}},
+		{[]string{"gzip", "br"}, codings{"gzip": 1, "br": 1}},
+		{[]string{"gzip", "gzip;q=0,br"}, codings{"gzip": 0, "br": 1}},
+	}
+	for i, c := range cases {
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			assert.Equal(t, c.parsed, parseEncodings(c.accept))
+		})
 	}
 }
 
@@ -443,7 +467,7 @@ func TestGzipHandlerNoBody(t *testing.T) {
 		req.Header.Set("Accept-Encoding", "gzip")
 		handler.ServeHTTP(rec, req)
 
-		body, err := ioutil.ReadAll(rec.Body)
+		body, err := io.ReadAll(rec.Body)
 		if err != nil {
 			t.Fatalf("Unexpected error reading response body: %v", err)
 		}
@@ -514,7 +538,7 @@ func TestGzipHandlerContentLength(t *testing.T) {
 		}
 		defer res.Body.Close()
 
-		body, err := ioutil.ReadAll(res.Body)
+		body, err := io.ReadAll(res.Body)
 		if err != nil {
 			t.Fatalf("Unexpected error reading response body in test iteration %d: %v", num, err)
 		}
@@ -624,7 +648,7 @@ func TestGzipHandlerDoubleWriteHeader(t *testing.T) {
 	}
 	req.Header.Set("Accept-Encoding", "gzip")
 	wrapper.ServeHTTP(rec, req)
-	body, err := ioutil.ReadAll(rec.Body)
+	body, err := io.ReadAll(rec.Body)
 	if err != nil {
 		t.Fatalf("Unexpected error reading response body: %v", err)
 	}
@@ -652,7 +676,7 @@ func TestGzipHandlerDoubleVary(t *testing.T) {
 	req := httptest.NewRequest(http.MethodGet, "/", nil)
 	req.Header.Set("Accept-Encoding", "gzip")
 	wrapper.ServeHTTP(rec, req)
-	body, err := ioutil.ReadAll(rec.Body)
+	body, err := io.ReadAll(rec.Body)
 	if err != nil {
 		t.Fatalf("Unexpected error reading response body: %v", err)
 	}
@@ -1206,7 +1230,7 @@ func zstdStrLevel(s string, lvl kpzstd.EncoderLevel) []byte {
 }
 
 func benchmark(b *testing.B, parallel bool, size int, ae string, d int) {
-	bin, err := ioutil.ReadFile("testdata/benchmark.json")
+	bin, err := os.ReadFile("testdata/benchmark.json")
 	if err != nil {
 		b.Fatal(err)
 	}
@@ -1321,5 +1345,5 @@ func decodeGzip(i io.Reader) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	return ioutil.ReadAll(r)
+	return io.ReadAll(r)
 }