Adds nfr requirements and design for unit 1

2026-06-19 21:34:20 +02:00
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+# NFR Design Patterns — Unit 1: Project Scaffold & Infrastructure
+
+## 1. Performance — Route-Based Code Splitting (Answer Q1-A)
+**Pattern**: Per-feature route modules with lazy-loaded layouts and page components.
+
+- TanStack Router `createLazyFileRoute` for dashboard, users, cms routes
+- Auth and root shell remain eager for fast initial paint and login
+- Vite automatically emits separate chunks per lazy route
+- Aligns with NFR-U1-01 (smallest possible bundle) and BR-U1-05 (TanStack Router)
+
+## 2. Accessibility — Keyboard & Focus Trap (Answer Q2-A)
+**Pattern**: Browser-native Tab order + shadcn/ui focus-visible + modal focus trap only.
+
+- All interactive elements use native `<button>`, `<a>`, form controls
+- `focus-visible` ring provided by shadcn/ui theme (Tailwind ring-2 ring-offset-2)
+- `FocusTrap` component (from `@radix-ui/react-focus-trap` or shadcn/ui dialog primitive) applied exclusively to modals and confirmation dialogs
+- No custom roving tabindex or arrow-key navigation unless explicitly required later
+
+## 3. Testing — Feature-Scoped MSW Handlers (Answer Q3-B)
+**Pattern**: Feature folders under `src/mocks/` with barrel exports.
+
+```
+src/mocks/
+  auth/
+    handlers.ts
+    fixtures.ts
+  users/
+    handlers.ts
+  index.ts
+```
+- `auth/handlers.ts` exports `authHandlers` array used in login, refresh, 401-retry tests
+- Easy to extend per future feature without central file bloat
+- Supports NFR-U1-04 (>70% coverage on auth components)
+
+## 4. Internationalization — Lazy Language Loading (Answer Q4-B)
+**Pattern**: Dynamic import of active locale only.
+
+- `i18next` initialized with `react-i18next` and `i18next-browser-languagedetector`
+- On language change: `i18next.changeLanguage(lng)` triggers `import(`../../public/locales/${lng}/translation.json`)`
+- Fallback to English; no eager bundling of both languages
+- Language switcher in user menu triggers the dynamic load + persists choice in localStorage via detector
+
+## 5. Error Handling — Per-Component ProblemDetails Mapping (Answer Q5-B)
+**Pattern**: Context-aware error presentation instead of global interceptor.
+
+- `ApiClient` throws typed `ProblemDetailsError` (extends Error)
+- Each page/form catches and decides:
+  - 401/403 → redirect or global AuthContext logout
+  - Validation errors (400) → inline field errors via react-hook-form
+  - Transient errors → shadcn/ui toast via `useToast()`
+- Keeps UI responsive and avoids one-size-fits-all toasts
+
+## 6. Configuration — Typed Vite Env + Optional Zod (Answer Q6-A)
+**Pattern**: Strong typing in `vite-env.d.ts` + runtime validation hook.
+
+```ts
+// vite-env.d.ts
+interface ImportMetaEnv {
+  readonly VITE_API_BASE_URL: string;
+  // future flags...
+}
+interface ImportMeta {
+  readonly env: ImportMetaEnv;
+}
+```
+- Optional `useAppConfig()` hook runs Zod parse once at bootstrap (development warning only)
+- Production trusts `.env` values (no runtime overhead)
+
+All patterns respect the "minimal viable" constraints from NFR Requirements (no Sentry, no pre-commit, basic a11y).