refactor: outsource auth function in all routes

frontend/src/routes/app/_hiddenLayout/add-product.tsx

@@ -1,14 +1,10 @@
-import { createFileRoute, redirect } from "@tanstack/react-router";
-import { isAuthenticated } from "../../../utils/api/auth";
+import { createFileRoute } from "@tanstack/react-router";
+import { verifyLogin } from "../../../utils/api/auth";
 import { AddProduct } from "../../../pages/AddProduct";
 
 export const Route = createFileRoute("/app/_hiddenLayout/add-product")({
   beforeLoad: async () => {
-    if (!(await isAuthenticated())) {
-      throw redirect({
-        to: "/login",
-      });
-    }
+    await verifyLogin();
   },
   component: RouteComponent,
 });

frontend/src/routes/app/_hiddenLayout/app-settings.tsx

@@ -1,14 +1,10 @@
-import { createFileRoute, redirect } from "@tanstack/react-router";
-import { isAuthenticated } from "../../../utils/api/auth";
+import { createFileRoute } from "@tanstack/react-router";
+import { verifyLogin } from "../../../utils/api/auth";
 import { Settings } from "../../../pages/Settings";
 
 export const Route = createFileRoute("/app/_hiddenLayout/app-settings")({
   beforeLoad: async () => {
-    if (!(await isAuthenticated())) {
-      throw redirect({
-        to: "/login",
-      });
-    }
+    await verifyLogin();
   },
   component: RouteComponent,
 });

frontend/src/routes/app/_hiddenLayout/inventory.tsx

@@ -1,14 +1,10 @@
-import { createFileRoute, redirect } from "@tanstack/react-router";
-import { isAuthenticated } from "../../../utils/api/auth";
+import { createFileRoute } from "@tanstack/react-router";
+import { verifyLogin } from "../../../utils/api/auth";
 import { InventoryPage } from "../../../pages/Inventory";
 
 export const Route = createFileRoute("/app/_hiddenLayout/inventory")({
   beforeLoad: async () => {
-    if (!(await isAuthenticated())) {
-      throw redirect({
-        to: "/login",
-      });
-    }
+    await verifyLogin();
   },
   component: RouteComponent,
 });

frontend/src/routes/app/_hiddenLayout/storages.tsx

@@ -1,14 +1,10 @@
-import { createFileRoute, redirect } from "@tanstack/react-router";
-import { isAuthenticated } from "../../../utils/api/auth";
+import { createFileRoute } from "@tanstack/react-router";
+import { verifyLogin } from "../../../utils/api/auth";
 import { Storages } from "../../../pages/Storages";
 
 export const Route = createFileRoute("/app/_hiddenLayout/storages")({
   beforeLoad: async () => {
-    if (!(await isAuthenticated())) {
-      throw redirect({
-        to: "/login",
-      });
-    }
+    await verifyLogin();
   },
   component: RouteComponent,
 });

frontend/src/routes/app/_hiddenLayout/view-product.tsx

@@ -1,15 +1,11 @@
-import { createFileRoute, redirect } from "@tanstack/react-router";
+import { createFileRoute } from "@tanstack/react-router";
 import { z } from "zod";
-import { isAuthenticated } from "../../../utils/api/auth";
+import { verifyLogin } from "../../../utils/api/auth";
 import { ViewProduct } from "../../../pages/ViewProduct";
 
 export const Route = createFileRoute("/app/_hiddenLayout/view-product")({
   beforeLoad: async () => {
-    if (!(await isAuthenticated())) {
-      throw redirect({
-        to: "/login",
-      });
-    }
+    await verifyLogin();
   },
   validateSearch: z.object({
     product: z.string(),

frontend/src/routes/index.tsx

@@ -6,6 +6,7 @@ export const Route = createFileRoute("/")({
     if (!(await isAuthenticated())) {
       throw redirect({
         to: "/login",
+        search: { loggedOut: true },
       });
     } else {
       throw redirect({

frontend/src/routes/login.tsx

@@ -1,7 +1,11 @@
 import { createFileRoute } from "@tanstack/react-router";
 import { LoginCard } from "../components/LoginCard";
+import { checkLogin } from "../utils/api/auth.ts";
 
 export const Route = createFileRoute("/login")({
+  beforeLoad: async () => {
+    await checkLogin();
+  },
   component: RouteComponent,
 });
 

frontend/src/utils/api/auth.ts

@@ -4,8 +4,9 @@ import type {TFunction} from "i18next";
 import { fetchSettings } from "./settings";
 import type { ChangePasswordIntf } from "../../misc/interfaces";
 import { createApiError } from "./apiError";
+import { redirect } from "@tanstack/react-router";
 
-export async function isAuthenticated() {
+export const isAuthenticated = async () => {
   if (Cookies.get("token")) {
     const result = await fetch(`${API_BASE}/users/verify-token`, {
       method: "POST",
@@ -23,13 +24,13 @@ export async function isAuthenticated() {
 
   Cookies.remove("token");
   return false;
-}
+};
 
-export async function signInUser(
+export const signInUser = async (
   username: string,
   password: string,
   t: TFunction,
-) {
+) => {
   const result = await fetch(`${API_BASE}/users/login`, {
     method: "POST",
     headers: {
@@ -54,12 +55,7 @@ export async function signInUser(
 
   Cookies.remove("token");
   throw createApiError(response.code, t(response.code || "unknown-error"));
-}
-
-export function signOutUser() {
-    Cookies.remove("token");
-    return {ok: true as const};
-}
+};
 
 export const mutatePassword = async (payload: ChangePasswordIntf) => {
   const result = await fetch(`${API_BASE}/users/change-password`, {
@@ -83,3 +79,20 @@ export const mutatePassword = async (payload: ChangePasswordIntf) => {
 
   throw createApiError(response.code, "Change password failed");
 };
+
+export const verifyLogin = async () => {
+  if (!(await isAuthenticated())) {
+    throw redirect({
+      to: "/login",
+      search: { loggedOut: true },
+    });
+  }
+};
+
+export const checkLogin = async () => {
+  if (await isAuthenticated()) {
+    throw redirect({
+      to: "/app/inventory",
+    });
+  }
+};