chore: import upstream snapshot with attribution

internal/base/middleware/accept_language.go

@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package middleware
+
+import (
+	"strings"
+
+	"github.com/apache/answer/internal/base/constant"
+	"github.com/apache/answer/internal/base/translator"
+	"github.com/gin-gonic/gin"
+	"github.com/segmentfault/pacman/i18n"
+	"golang.org/x/text/language"
+)
+
+const maxAcceptLanguageLength = 256
+
+// ExtractAndSetAcceptLanguage extract accept language from header and set to context
+func ExtractAndSetAcceptLanguage(ctx *gin.Context) {
+	// The language of our front-end configuration, like en_US
+	acceptLanguage := ctx.GetHeader(constant.AcceptLanguageFlag)
+	if len(acceptLanguage) > maxAcceptLanguageLength {
+		ctx.Set(constant.AcceptLanguageFlag, i18n.LanguageEnglish)
+		return
+	}
+	tag, _, err := language.ParseAcceptLanguage(acceptLanguage)
+	if err != nil || len(tag) == 0 {
+		ctx.Set(constant.AcceptLanguageFlag, i18n.LanguageEnglish)
+		return
+	}
+
+	acceptLang := strings.ReplaceAll(tag[0].String(), "-", "_")
+
+	for _, option := range translator.LanguageOptions {
+		if option.Value == acceptLang {
+			ctx.Set(constant.AcceptLanguageFlag, i18n.Language(acceptLang))
+			return
+		}
+	}
+
+	// default language
+	ctx.Set(constant.AcceptLanguageFlag, i18n.LanguageEnglish)
+}