Allow querying and changeing i18n language via API.

config.go

@@ -45,6 +45,7 @@ type configuration struct {
 	CoreDNS       coreDNSConfig `yaml:"coredns"`
 	Filters       []filter      `yaml:"filters"`
 	UserRules     []string      `yaml:"user_rules"`
+	Language      string        `yaml:"language"` // two-letter ISO 639-1 language code
 
 	sync.RWMutex `yaml:"-"`
 }

control.go

@@ -84,6 +84,7 @@ func handleStatus(w http.ResponseWriter, r *http.Request) {
 		"bootstrap_dns":      config.CoreDNS.BootstrapDNS,
 		"upstream_dns":       config.CoreDNS.UpstreamDNS,
 		"version":            VersionString,
+		"language":           config.Language,
 	}
 
 	jsonVal, err := json.Marshal(data)
@@ -876,6 +877,8 @@ func registerControlHandlers() {
 	http.HandleFunc("/control/querylog_disable", optionalAuth(ensurePOST(handleQueryLogDisable)))
 	http.HandleFunc("/control/set_upstream_dns", optionalAuth(ensurePOST(handleSetUpstreamDNS)))
 	http.HandleFunc("/control/test_upstream_dns", optionalAuth(ensurePOST(handleTestUpstreamDNS)))
+	http.HandleFunc("/control/i18n/change_language", optionalAuth(ensurePOST(handleI18nChangeLanguage)))
+	http.HandleFunc("/control/i18n/current_language", optionalAuth(ensureGET(handleI18nCurrentLanguage)))
 	http.HandleFunc("/control/stats_top", optionalAuth(ensureGET(corednsplugin.HandleStatsTop)))
 	http.HandleFunc("/control/stats", optionalAuth(ensureGET(corednsplugin.HandleStats)))
 	http.HandleFunc("/control/stats_history", optionalAuth(ensureGET(corednsplugin.HandleStatsHistory)))

i18n.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"strings"
+)
+
+// --------------------
+// internationalization
+// --------------------
+var allowedLanguages = map[string]bool{
+	"en": true,
+	"ru": true,
+	"vi": true,
+}
+
+func isLanguageAllowed(language string) bool {
+	l := strings.ToLower(language)
+	if allowedLanguages[l] {
+		return true
+	}
+	return false
+}
+
+func handleI18nCurrentLanguage(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain")
+	_, err := fmt.Fprintf(w, config.Language)
+	if err != nil {
+		errortext := fmt.Sprintf("Unable to write response json: %s", err)
+		log.Println(errortext)
+		http.Error(w, errortext, http.StatusInternalServerError)
+		return
+	}
+}
+
+func handleI18nChangeLanguage(w http.ResponseWriter, r *http.Request) {
+	body, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		errorText := fmt.Sprintf("failed to read request body: %s", err)
+		log.Println(errorText)
+		http.Error(w, errorText, http.StatusBadRequest)
+		return
+	}
+
+	language := strings.TrimSpace(string(body))
+	if language == "" {
+		errorText := fmt.Sprintf("empty language specified")
+		log.Println(errorText)
+		http.Error(w, errorText, http.StatusBadRequest)
+		return
+	}
+	if !isLanguageAllowed(language) {
+		errorText := fmt.Sprintf("unknown language specified: %s", language)
+		log.Println(errorText)
+		http.Error(w, errorText, http.StatusBadRequest)
+		return
+	}
+
+	httpUpdateConfigReloadDNSReturnOK(w, r)
+}

openapi.yaml

@@ -46,6 +46,7 @@ paths:
                               - 1.1.1.1
                               - 1.0.0.1
                             version: "v0.1"
+                            language: "en"
     /enable_protection:
         post:
             tags:
@@ -193,6 +194,33 @@ paths:
                             8.8.8.8: OK
                             8.8.4.4: OK
                             "192.168.1.104:53535": "Couldn't communicate with DNS server"
+    /i18n/change_language:
+        post:
+            tags:
+                - i18n
+            operationId: changeLanguage
+            summary: "Change current language. Argument must be an ISO 639-1 two-letter code"
+            consumes:
+                - text/plain
+            parameters:
+                - in: body
+                  name: language
+                  description: "New language. It must be known to the server and must be an ISO 639-1 two-letter code"
+                  schema:
+                    type: string
+                    example: en
+    /i18n/current_language:
+        get:
+            tags:
+                - i18n
+            operationId: currentLanguage
+            summary: "Get currently set language. Result is ISO 639-1 two-letter code. Empty result means default language."
+            responses:
+                200:
+                    description: OK
+                    examples:
+                        text/plain:
+                            en
     /stats_top:
         get:
             tags: