Feature/fyp 40

backend/src/db/handlers/profiles.ts

@@ -7,7 +7,7 @@ type Profile = {
   email?: string | null;
   username?: string;
   photo?: string | null;
-  settings?: Record<string, any> | null;
+  settings?: Record<string, unknown> | null;
   bio?: string | null;
 };
 
@@ -50,7 +50,16 @@ export const uploadAvatar = async (
 const getProfileById = async (userId: string) => {
   try {
     const result = await pool.query(
-      "SELECT id, photo, username, bio FROM profiles WHERE id = $1",
+      `
+      SELECT
+        id,
+        photo,
+        username,
+        bio,
+        settings->>'country_code' AS country_code
+      FROM profiles
+      WHERE id = $1
+      `,
       [userId]
     );
     return result.rows[0];
@@ -63,7 +72,18 @@ const getProfileById = async (userId: string) => {
 const getMyProfile = async (userId: string) => {
     try {
         const result = await pool.query(
-          "SELECT id, photo, username, email, settings, bio FROM profiles WHERE id = $1",
+          `
+          SELECT
+            id,
+            photo,
+            username,
+            email,
+            settings,
+            bio,
+            settings->>'country_code' AS country_code
+          FROM profiles
+          WHERE id = $1
+          `,
           [userId]
         );
         return result.rows[0];
@@ -79,9 +99,9 @@ const createProfile = async (userProfile: Profile) => {
   }
   const result = await pool.query(
     `
-        INSERT INTO profiles (id, email, username, photo, settings, bio, created_at, updated_at) 
+        INSERT INTO profiles (id, email, username, photo, settings, bio, created_at, updated_at)
         VALUES ($1, $2, $3, $4, $5, $6, NOW(), NOW())
-        RETURNING id, email, username, photo, settings, bio
+        RETURNING id, email, username, photo, settings, bio, settings->>'country_code' AS country_code
         `,
     [
       userProfile.userId,
@@ -105,7 +125,7 @@ const updateProfile = async (userProfile: Profile) => {
                 bio = $5,
                 updated_at = NOW()
             WHERE id = $1 
-            RETURNING *
+            RETURNING id, email, username, photo, settings, bio, settings->>'country_code' AS country_code
         `,
     [
       userProfile.userId,

backend/src/routes/authenticated/forums/replies.ts

@@ -40,7 +40,8 @@ router.get("/", async (req, res) => {
 				r.parent_reply_id,
 				r.created_at,
 				p.username,
-				p.photo
+				p.photo,
+				p.settings->>'country_code' AS country_code
 			FROM public.replies r
 			LEFT JOIN public.profiles p ON p.id = r.user_id
 			WHERE r.thread_id = $1

backend/src/routes/authenticated/forums/threads.ts

@@ -72,7 +72,8 @@ router.get("/", async (req, res) => {
 				t.created_at,
 				t.updated_at,
 				p.username,
-				p.photo
+				p.photo,
+				p.settings->>'country_code' AS country_code
 			FROM public.threads t
 			LEFT JOIN public.profiles p ON p.id = t.user_id
 			${whereSql}
@@ -113,7 +114,8 @@ router.get("/:id", async (req, res) => {
 				t.created_at,
 				t.updated_at,
 				p.username,
-				p.photo
+				p.photo,
+				p.settings->>'country_code' AS country_code
 			FROM public.threads t
 			LEFT JOIN public.profiles p ON p.id = t.user_id
 			WHERE t.id = $1

backend/src/routes/authenticated/profiles.ts

@@ -15,6 +15,33 @@ import { authenticateToken } from "../../middlewares/authenticator";
 const router = Router();
 const upload = multer({ storage: multer.memoryStorage() });
 
+const normalizeCountryCode = (value: unknown): string | null => {
+  if (typeof value !== "string") return null;
+  const normalized = value.trim().toUpperCase();
+  return /^[A-Z]{2}$/.test(normalized) ? normalized : null;
+};
+
+const parseSettingsInput = (value: unknown): Record<string, unknown> | null => {
+  if (!value) return null;
+
+  if (typeof value === "string") {
+    try {
+      const parsed = JSON.parse(value) as unknown;
+      return parsed && typeof parsed === "object" && !Array.isArray(parsed)
+        ? (parsed as Record<string, unknown>)
+        : null;
+    } catch {
+      return null;
+    }
+  }
+
+  if (typeof value === "object" && !Array.isArray(value)) {
+    return value as Record<string, unknown>;
+  }
+
+  return null;
+};
+
 // Personal profile routes
 
 router.get("/me", authenticateToken, async (_req, res) => {
@@ -41,19 +68,41 @@ router.patch(
     try {
       const userId = req.user.sub;
 
-      const existingProfile = await getProfileById(userId);
+      const existingProfile = await getMyProfile(userId);
 
       if (!existingProfile) {
         return res.status(404).json({ error: "Profile not found" });
       }
 
       const photoUrl = await uploadAvatar(userId, req.file);
+      const hasCountryCodeField = Object.prototype.hasOwnProperty.call(
+        req.body,
+        "country_code",
+      );
+      const normalizedCountryCode = normalizeCountryCode(req.body.country_code);
+      const incomingSettings = parseSettingsInput(req.body.settings);
+      const existingSettings =
+        existingProfile.settings && typeof existingProfile.settings === "object"
+          ? (existingProfile.settings as Record<string, unknown>)
+          : {};
+      const mergedSettings: Record<string, unknown> = {
+        ...existingSettings,
+        ...(incomingSettings ?? {}),
+      };
+
+      if (hasCountryCodeField) {
+        if (normalizedCountryCode) {
+          mergedSettings.country_code = normalizedCountryCode;
+        } else {
+          delete mergedSettings.country_code;
+        }
+      }
 
       const updatedProfile = {
         userId,
         username: req.body.username ?? existingProfile.username,
         photo: photoUrl ?? existingProfile.photo,
-        settings: req.body.settings ?? existingProfile.settings ?? null, // never undefined
+        settings: Object.keys(mergedSettings).length > 0 ? mergedSettings : null,
         bio: req.body.bio ?? existingProfile.bio ?? null,
       };
 

frontend/src/App.tsx

@@ -20,10 +20,64 @@ import {
   DEFAULT_LOCALE,
   normalizeLocale,
   resolvePathLocaleSegment,
+  type AppLocale,
 } from "./i18n/locales";
 import { localizePath, parseLocaleFromPathname } from "./utils/localeRouting";
 import TopAttractions from "./pages/public/explore/TopAttractions";
 
+const PROFILE_STORAGE_KEY = "profile";
+const HANT_DEFAULT_COUNTRY_CODES = new Set(["HK", "CN", "TW"]);
+
+const resolveLocaleFromCountryCode = (
+  countryCode: string | null | undefined,
+): AppLocale => {
+  const normalized = countryCode?.trim().toUpperCase() ?? "";
+  return HANT_DEFAULT_COUNTRY_CODES.has(normalized)
+    ? "zh-Hant-HK"
+    : "en-GB";
+};
+
+const getUserDefaultLocale = (): AppLocale => {
+  if (typeof window === "undefined") return DEFAULT_LOCALE;
+
+  try {
+    const rawProfile = window.localStorage.getItem(PROFILE_STORAGE_KEY);
+    if (!rawProfile) return DEFAULT_LOCALE;
+
+    const parsedProfile = JSON.parse(rawProfile) as {
+      settings?: {
+        last_used_locale?: unknown;
+        country_code?: unknown;
+      };
+      country_code?: unknown;
+      countryCode?: unknown;
+    };
+
+    const localeFromSettings = normalizeLocale(
+      typeof parsedProfile.settings?.last_used_locale === "string"
+        ? parsedProfile.settings.last_used_locale
+        : null,
+    );
+
+    if (localeFromSettings) {
+      return localeFromSettings;
+    }
+
+    const countryCode =
+      typeof parsedProfile.settings?.country_code === "string"
+        ? parsedProfile.settings.country_code
+        : typeof parsedProfile.country_code === "string"
+          ? parsedProfile.country_code
+          : typeof parsedProfile.countryCode === "string"
+            ? parsedProfile.countryCode
+            : null;
+
+    return resolveLocaleFromCountryCode(countryCode);
+  } catch {
+    return DEFAULT_LOCALE;
+  }
+};
+
 const KNOWN_UNLOCALIZED_PATH_PATTERNS = [
   /^\/$/,
   /^\/events(?:\/[^/]+)?\/?$/,
@@ -68,7 +122,7 @@ const resolveLangQuery = (search: string) => {
 const MissingLocaleRedirect = () => {
   const location = useLocation();
   const langQuery = resolveLangQuery(location.search);
-  const nextLocale = langQuery?.locale ?? DEFAULT_LOCALE;
+  const nextLocale = langQuery?.locale ?? getUserDefaultLocale();
   const nextSearch = langQuery?.search ?? location.search;
 
   return (
@@ -125,7 +179,7 @@ const LocaleGate = () => {
 
     return (
       <Navigate
-        to={`${localizePath("/", langQuery?.locale ?? DEFAULT_LOCALE)}${langQuery?.search ?? ""}${location.hash}`}
+        to={`${localizePath("/", langQuery?.locale ?? getUserDefaultLocale())}${langQuery?.search ?? ""}${location.hash}`}
         replace
       />
     );

frontend/src/components/i18n/LangToggler.tsx

@@ -5,9 +5,12 @@ import { useState, useRef, useEffect } from "react";
 import { useLocation, useNavigate } from "react-router-dom";
 import type { AppLocale } from "../../i18n/locales";
 import { replaceLocaleInPathname } from "../../utils/localeRouting";
+import { useAuth } from "../../context/AuthContext";
+import CONFIG from "../../config";
 
 const LangToggler = () => {
     const { i18n, t } = useTranslation();
+    const { token, profile, refreshProfile } = useAuth();
     const location = useLocation();
     const navigate = useNavigate();
     const [open, setOpen] = useState(false);
@@ -32,6 +35,31 @@ const LangToggler = () => {
     const changeLang = async (lng: AppLocale) => {
         const nextPathname = replaceLocaleInPathname(location.pathname, lng);
         await i18n.changeLanguage(lng);
+
+        if (token && profile) {
+            try {
+                const mergedSettings = {
+                    ...(profile.settings ?? {}),
+                    last_used_locale: lng,
+                };
+
+                await fetch(`${CONFIG.API_BASE_URL}/profiles/me`, {
+                    method: "PATCH",
+                    headers: {
+                        "Content-Type": "application/json",
+                        Authorization: `Bearer ${token}`,
+                    },
+                    body: JSON.stringify({
+                        settings: mergedSettings,
+                    }),
+                });
+
+                await refreshProfile();
+            } catch {
+                // Ignore locale preference persistence failures and continue navigation.
+            }
+        }
+
         navigate(`${nextPathname}${location.search}${location.hash}`);
         setOpen(false);
     };

frontend/src/context/AuthContext.tsx

@@ -9,6 +9,12 @@ export type ProfileType = {
   username: string;
   photo: string | null;
   bio: string | null;
+  country_code: string | null;
+  settings: {
+    country_code?: string;
+    last_used_locale?: string;
+    [key: string]: unknown;
+  } | null;
 };
 
 type AuthContextType = {