feat(mobx): implement locale options

src/mobx/State.ts

@@ -5,6 +5,7 @@ import { useContext } from "preact/hooks";
 
 import Auth from "./stores/Auth";
 import Draft from "./stores/Draft";
+import LocaleOptions from "./stores/LocaleOptions";
 
 interface StoreDefinition {
     id: string;
@@ -20,6 +21,7 @@ interface StoreDefinition {
 export default class State {
     auth: Auth;
     draft: Draft;
+    locale: LocaleOptions;
 
     /**
      * Construct new State.
@@ -27,6 +29,7 @@ export default class State {
     constructor() {
         this.auth = new Auth();
         this.draft = new Draft();
+        this.locale = new LocaleOptions();
 
         makeAutoObservable(this);
     }

src/mobx/stores/LocaleOptions.ts

@@ -72,13 +72,21 @@ export default class LocaleOptions implements Persistent<Data> {
 
     // eslint-disable-next-line require-jsdoc
     @action hydrate(data: Data) {
-        this.lang = data.lang;
+        this.setLanguage(data.lang);
     }
 
     /**
      * Get current language.
      */
-    @computed getLang() {
+    @computed getLanguage() {
         return this.lang;
     }
+
+    /**
+     * Set current language.
+     */
+    @action setLanguage(language: Language) {
+        if (typeof Languages[language] === "undefined") return;
+        this.lang = language;
+    }
 }