feat(acceptHeaders): avoid matching zero-quality item

See also: https://www.rfc-editor.org/rfc/rfc9110.html#quality.values

> The weight is normalized to a real number in the range 0 through 1, ...
> a value of 0 means "not acceptable".

Author: marjune163

src/acceptHeaders/accepts.go

@@ -28,6 +28,8 @@ func (accepts Accepts) GetPreferredValue(availables []string) (index int, value
 			}
 		}
 	}
+
+	index = -1
 	return
 }
 
@@ -38,9 +40,19 @@ func ParseAccepts(input string) Accepts {
 		return nil
 	}
 
-	accepts := make(Accepts, entryCount)
+	accepts := make(Accepts, 0, entryCount)
 	for i := 0; i < entryCount; i++ {
-		accepts[i] = parseAcceptItem(strings.TrimSpace(entries[i]))
+		input := strings.TrimSpace(entries[i])
+		if len(input) == 0 {
+			continue
+		}
+
+		accept := parseAcceptItem(input)
+		if accept.quality <= 0 {
+			continue
+		}
+
+		accepts = append(accepts, accept)
 	}
 	sort.Sort(accepts)
 	return accepts

src/acceptHeaders/accepts_test.go

@@ -127,11 +127,12 @@ func TestParseAcceptEncoding(t *testing.T) {
 }
 
 func TestParseAcceptEncoding2(t *testing.T) {
-	acceptEncoding := "gzip;v=b3;q=0.9, deflate"
+	acceptEncoding := "gzip;v=b3;q=0.9, deflate, br;q=0.0, zstd;  q=0, "
 	accepts := ParseAccepts(acceptEncoding)
 
 	var index int
 	var preferred string
+	var ok bool
 	index, preferred, _ = accepts.GetPreferredValue([]string{"gzip"})
 	if index != 0 {
 		t.Error(index)
@@ -187,4 +188,23 @@ func TestParseAcceptEncoding2(t *testing.T) {
 	if preferred != "deflate" {
 		t.Error(preferred)
 	}
+
+	index, preferred, ok = accepts.GetPreferredValue([]string{"zstd", "br"})
+	if index != -1 {
+		t.Error(index)
+	}
+	if ok {
+		t.Error(preferred)
+	}
+
+	index, preferred, ok = accepts.GetPreferredValue([]string{"zstd", "br", "gzip"})
+	if index != 2 {
+		t.Error(index)
+	}
+	if preferred != "gzip" {
+		t.Error(preferred)
+	}
+	if !ok {
+		t.Error(preferred)
+	}
 }