Extract reusable auth guard decision logic and test router auth behavior against it

Co-Authored-By: Codex <codex@openai.com>

src/router/authGuard.ts

@@ -0,0 +1,74 @@
+// The Lucia project.
+// Copyright 2026-2026 DSP, inc.  All rights reserved.
+// Authors:
+//   imacat.yang@dsp.im (imacat), 2026/03/08
+/**
+ * @module router/authGuard Shared auth-guard decision logic for router.beforeEach
+ *   and unit tests.
+ */
+
+/** Minimal route shape used by auth guard decision logic. */
+export interface GuardRouteTarget {
+  name?: unknown;
+  path?: string;
+  fullPath?: string;
+  matched?: Array<{ meta?: { requiresAuth?: boolean } }>;
+}
+
+/** Dependency contract for evaluating authentication navigation decisions. */
+export interface AuthGuardDependencies {
+  /** Reads a cookie value by name. */
+  getCookie: (name: string) => string | null;
+  /** Attempts to refresh session credentials. */
+  refreshSession: () => Promise<void>;
+  /** Persists the logged-in marker cookie after successful refresh. */
+  setLoginMarker: () => void;
+  /** Encodes return-to path into query-safe payload. */
+  encodeReturnTo: (returnToPath: string) => string;
+}
+
+/**
+ * Evaluates auth-related navigation decisions.
+ * @param {GuardRouteTarget} to - Target route object from router guard.
+ * @param {AuthGuardDependencies} deps - Side-effect dependencies for auth checks.
+ * @returns {Promise<{name: string}|{path: string, query: {"return-to": string}}|undefined>}
+ *   Redirect target when needed, otherwise undefined.
+ */
+export async function evaluateAuthNavigation(
+  to: GuardRouteTarget,
+  deps: AuthGuardDependencies,
+) {
+  const hasLoginMarker = Boolean(deps.getCookie("isLuciaLoggedIn"));
+  const hasAccessToken = Boolean(deps.getCookie("luciaToken"));
+  const hasRefreshToken = Boolean(deps.getCookie("luciaRefreshToken"));
+  const isAuthenticated = hasLoginMarker && hasAccessToken;
+
+  if (to.name === "Login" && isAuthenticated) {
+    return { name: "Files" };
+  }
+
+  const requiresAuth = (to.matched || []).some(
+    (routeRecord) => routeRecord.meta?.requiresAuth,
+  );
+  if (!requiresAuth || isAuthenticated) {
+    return undefined;
+  }
+
+  if (hasRefreshToken) {
+    try {
+      await deps.refreshSession();
+      deps.setLoginMarker();
+      return undefined;
+    } catch {
+      // Fall through to login redirect below.
+    }
+  }
+
+  const returnToPath = to.fullPath || to.path || "/";
+  return {
+    path: "/login",
+    query: {
+      "return-to": deps.encodeReturnTo(returnToPath),
+    },
+  };
+}

src/router/index.ts

@@ -13,6 +13,7 @@ import { createRouter, createWebHistory } from "vue-router";
 import { useLoginStore } from "@/stores/login";
 import { getCookie, setCookie } from "@/utils/cookieUtil";
 import { encodeReturnTo } from "@/utils/returnToEncoding";
+import { evaluateAuthNavigation } from "@/router/authGuard";
 import AuthContainer from "@/views/AuthContainer.vue";
 import MainContainer from "@/views/MainContainer.vue";
 import Login from "@/views/Login/LoginPage.vue";
@@ -174,51 +175,18 @@ const router = createRouter({
   routes,
 });
 
-/**
- * Builds a login redirect target with a return-to query.
- * @param {string} fullPath - The destination path to return after login.
- * @returns {{path: string, query: {"return-to": string}}} The redirect target.
- */
-function buildLoginRedirect(fullPath: string) {
-  return {
-    path: "/login",
-    query: {
-      "return-to": encodeReturnTo(fullPath),
-    },
-  };
-}
-
 // Global navigation guard
 router.beforeEach(async (to) => {
-  // to: Route: the target route object being navigated to
-  const hasLoginMarker = Boolean(getCookie("isLuciaLoggedIn"));
-  const hasAccessToken = Boolean(getCookie("luciaToken"));
-  const hasRefreshToken = Boolean(getCookie("luciaRefreshToken"));
-  const isAuthenticated = hasLoginMarker && hasAccessToken;
-
-  // When navigating to the login page, redirect to Files if already logged in
-  if (to.name === "Login" && isAuthenticated) {
-    return { name: "Files" };
-  }
-
-  const requiresAuth = to.matched.some((routeRecord) => routeRecord.meta.requiresAuth);
-  if (!requiresAuth || isAuthenticated) {
-    return undefined;
-  }
-
-  if (hasRefreshToken) {
-    const loginStore = useLoginStore();
-    try {
+  return evaluateAuthNavigation(to, {
+    getCookie,
+    refreshSession: async () => {
+      const loginStore = useLoginStore();
       await loginStore.refreshToken();
       loginStore.setIsLoggedIn(true);
-      setCookie("isLuciaLoggedIn", "true");
-      return undefined;
-    } catch {
-      return buildLoginRedirect(to.fullPath);
-    }
-  }
-
-  return buildLoginRedirect(to.fullPath);
+    },
+    setLoginMarker: () => setCookie("isLuciaLoggedIn", "true"),
+    encodeReturnTo,
+  });
 });
 
 export default router;

tests/router/routerGuard.test.js

@@ -5,6 +5,7 @@
 
 import { describe, it, expect, beforeEach } from "vitest";
 import { decodeReturnTo } from "@/utils/returnToEncoding";
+import { evaluateAuthNavigation } from "@/router/authGuard";
 
 describe("router beforeEach guard logic", () => {
   beforeEach(() => {
@@ -17,38 +18,30 @@ describe("router beforeEach guard logic", () => {
     });
   });
 
-  // Simulate the guard logic from router/index.ts
+  // Run the real auth guard decision logic from src/router/authGuard.ts
   async function runGuard(to, options = {}) {
     const { refreshSucceeds = true } = options;
-    const hasLoginMarker = document.cookie
-      .split(";")
-      .some((c) => c.trim().startsWith("isLuciaLoggedIn="));
-    const hasAccessToken = document.cookie
-      .split(";")
-      .some((c) => c.trim().startsWith("luciaToken="));
-    const hasRefreshToken = document.cookie
-      .split(";")
-      .some((c) => c.trim().startsWith("luciaRefreshToken="));
-    const isAuthenticated = hasLoginMarker && hasAccessToken;
-
-    if (to.name === "Login") {
-      if (isAuthenticated) return { name: "Files" };
-    }
-
-    const requiresAuth = (to.matched || []).some((r) => r.meta?.requiresAuth);
-    if (requiresAuth && !isAuthenticated) {
-      if (hasRefreshToken) {
-        if (refreshSucceeds) return undefined;
-      }
-      return {
-        path: "/login",
-        query: {
-          "return-to": btoa(to.fullPath || to.path || "/"),
-        },
-      };
-    }
-
-    return undefined;
+    return evaluateAuthNavigation(to, {
+      getCookie: (name) => {
+        const cookieArr = document.cookie.split(";");
+        for (const cookie of cookieArr) {
+          const c = cookie.trim();
+          if (c.startsWith(`${name}=`)) {
+            return c.slice(name.length + 1);
+          }
+        }
+        return null;
+      },
+      refreshSession: async () => {
+        if (!refreshSucceeds) {
+          throw new Error("refresh failed");
+        }
+      },
+      setLoginMarker: () => {
+        document.cookie = "isLuciaLoggedIn=true";
+      },
+      encodeReturnTo: (path) => btoa(path),
+    });
   }
 
   it("redirects logged-in user from Login to Files", () => {