Add support for Traditional Chinese translation (#2309)

* Init Traditional Chinese(zh-TW) translation

* Update Traditional Chinese translation

* Fix stiff and typo translation

* Update locale handler to support new locale

* Remove unsupported locale directory test case

i18n/locale_conf.json

 {
   "translations": [
-    {"file": "messages-en.xtb", "key": "en"},
-    {"file": "messages-zh.xtb", "key": "zh"},
-    {"file": "messages-ja.xtb", "key": "ja"}
+    {"file": "messages-en.xtb",    "key": "en"},
+    {"file": "messages-zh-tw.xtb", "key": "zh-tw"},
+    {"file": "messages-zh.xtb",    "key": "zh"},
+    {"file": "messages-ja.xtb",    "key": "ja"}
   ]
 }

src/app/backend/handler/localehandler.go

@@ -19,6 +19,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"os"
+	"strings"
 
 	"github.com/golang/glog"
 	"golang.org/x/text/language"
@@ -40,7 +41,7 @@ type Translation struct {
 // LocaleHandler serves different localized versions of the frontend application
 // based on the Accept-Language header.
 type LocaleHandler struct {
-	SupportedLocales []string
+	SupportedLocales []language.Tag
 }
 
 // CreateLocaleHandler loads the localization configuration and constructs a LocaleHandler.
@@ -48,16 +49,16 @@ func CreateLocaleHandler() *LocaleHandler {
 	locales, err := getSupportedLocales("./locale_conf.json")
 	if err != nil {
 		glog.Warningf("Error when loading the localization configuration. Dashboard will not be localized. %s", err)
-		locales = []string{}
+		locales = []language.Tag{}
 	}
 	return &LocaleHandler{SupportedLocales: locales}
 }
 
-func getSupportedLocales(configFile string) ([]string, error) {
+func getSupportedLocales(configFile string) ([]language.Tag, error) {
 	// read config file
 	localesFile, err := ioutil.ReadFile(configFile)
 	if err != nil {
-		return []string{}, err
+		return []language.Tag{}, err
 	}
 
 	// unmarshall
@@ -68,9 +69,9 @@ func getSupportedLocales(configFile string) ([]string, error) {
 	}
 
 	// filter locale keys
-	result := []string{}
+	result := []language.Tag{}
 	for _, translation := range localization.Translations {
-		result = append(result, translation.Key)
+		result = append(result, language.Make(translation.Key))
 	}
 	return result, nil
 }
@@ -93,19 +94,22 @@ func (handler *LocaleHandler) determineLocalizedDir(locale string) string {
 		return defaultDir
 	}
 
-	for _, tag := range tags {
-		matchedLocale := ""
-		for _, l := range handler.SupportedLocales {
+	locales := handler.SupportedLocales
+	tag, _, confidence := language.NewMatcher(locales).Match(tags...)
+	matchedLocale := strings.ToLower(tag.String())
+	if confidence != language.Exact {
+		matchedLocale = ""
+		for _, l := range locales {
 			base, _ := tag.Base()
-			if l == base.String() {
-				matchedLocale = l
-				break
+			if l.String() == base.String() {
+				matchedLocale = l.String()
 			}
 		}
-		localeDir := "./public/" + matchedLocale
-		if matchedLocale != "" && handler.dirExists(localeDir) {
-			return localeDir
-		}
+	}
+
+	localeDir := "./public/" + matchedLocale
+	if matchedLocale != "" && handler.dirExists(localeDir) {
+		return localeDir
 	}
 	return defaultDir
 }

src/app/backend/handler/localehandler_test.go

@@ -20,12 +20,22 @@ import (
 	"os"
 	"reflect"
 	"testing"
+
+	"golang.org/x/text/language"
 )
 
+func languageMake(locales []string) []language.Tag {
+	result := []language.Tag{}
+	for _, locale := range locales {
+		result = append(result, language.Make(locale))
+	}
+	return result
+}
+
 func TestGetSupportedLocales(t *testing.T) {
 	cases := []struct {
 		localization Localization
-		expected     []string
+		expected     []language.Tag
 	}{
 		{
 			Localization{
@@ -34,11 +44,11 @@ func TestGetSupportedLocales(t *testing.T) {
 					{File: "ja/index.html", Key: "ja"},
 				},
 			},
-			[]string{"en", "ja"},
+			languageMake([]string{"en", "ja"}),
 		},
 		{
 			Localization{},
-			[]string{},
+			[]language.Tag{},
 		},
 	}
 
@@ -67,7 +77,7 @@ func TestDetermineLocale(t *testing.T) {
 	}{
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			false,
 			"en",
@@ -75,7 +85,7 @@ func TestDetermineLocale(t *testing.T) {
 		},
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			false,
 			"de",
@@ -83,7 +93,7 @@ func TestDetermineLocale(t *testing.T) {
 		},
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			false,
 			"ja",
@@ -91,7 +101,7 @@ func TestDetermineLocale(t *testing.T) {
 		},
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			true,
 			"ja",
@@ -99,7 +109,7 @@ func TestDetermineLocale(t *testing.T) {
 		},
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			true,
 			"ja,en-US;q=0.8,en;q=0.6",
@@ -107,7 +117,7 @@ func TestDetermineLocale(t *testing.T) {
 		},
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			true,
 			"af,ja,en-US;q=0.8,en;q=0.6",
@@ -115,7 +125,7 @@ func TestDetermineLocale(t *testing.T) {
 		},
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			true,
 			"af,en-US;q=0.8,en;q=0.6",
@@ -123,12 +133,60 @@ func TestDetermineLocale(t *testing.T) {
 		},
 		{
 			&LocaleHandler{
-				SupportedLocales: []string{"en", "ja"},
+				SupportedLocales: languageMake([]string{"en", "ja"}),
 			},
 			true,
 			"",
 			defaultDir,
 		},
+		{
+			&LocaleHandler{
+				SupportedLocales: languageMake([]string{"en", "zh-tw", "zh-hk", "zh", "ar-dz"}),
+			},
+			true,
+			"en",
+			"./public/en",
+		},
+		{
+			&LocaleHandler{
+				SupportedLocales: languageMake([]string{"en", "zh-tw", "zh-hk", "zh", "ar-dz"}),
+			},
+			true,
+			"zh",
+			"./public/zh",
+		},
+		{
+			&LocaleHandler{
+				SupportedLocales: languageMake([]string{"en", "zh-tw", "zh-hk", "zh", "ar-dz"}),
+			},
+			true,
+			"zh-cn",
+			"./public/zh",
+		},
+		{
+			&LocaleHandler{
+				SupportedLocales: languageMake([]string{"en", "zh-tw", "zh-hk", "zh", "ar-dz"}),
+			},
+			true,
+			"ar",
+			"./public/en",
+		},
+		{
+			&LocaleHandler{
+				SupportedLocales: languageMake([]string{"en", "zh-tw", "zh-hk", "zh", "ar-dz"}),
+			},
+			true,
+			"ar-bh",
+			"./public/en",
+		},
+		{
+			&LocaleHandler{
+				SupportedLocales: languageMake([]string{"en", "zh-tw", "zh", "ar-dz"}),
+			},
+			true,
+			"af,zh-HK,zh;q=0.8,en;q=0.6",
+			"./public/zh",
+		},
 	}
 
 	for _, c := range cases {
@@ -139,7 +197,7 @@ func TestDetermineLocale(t *testing.T) {
 					t.Fatalf("%s", err)
 				}
 				for _, lang := range c.handler.SupportedLocales {
-					err = os.Mkdir("./public/"+lang, 0777)
+					err = os.Mkdir("./public/"+lang.String(), 0777)
 					if err != nil {
 						t.Fatalf("%s", err)
 					}