App Specific Patterns

Jotai State Management

Directory Structure

src/states/
├── ui/
│   ├── sidebar/              # Multi-file feature
│   ├── device.ts             # Single-file feature
│   └── modal/                # 1 modal = 1 file
│       ├── page-create.ts
│       └── page-delete.ts
├── page/                     # Page data state
├── server-configurations/
└── context.ts

features/{name}/client/states/  # Feature-scoped atoms

Placement Rules

Derived Atoms

import { atom } from 'jotai';

export const currentPageAtom = atom<Page | null>(null);

// Derived (read-only)
export const currentPagePathAtom = atom((get) => {
  return get(currentPageAtom)?.path ?? null;
});

SWR Data Fetching

Directory

src/stores-universal/
├── pages.ts       # Page hooks
├── users.ts       # User hooks
└── admin/settings.ts

Patterns

import useSWR from 'swr';
import useSWRImmutable from 'swr/immutable';

// Auto-revalidation
export const usePageList = () => useSWR<Page[]>('/api/v3/pages', fetcher);

// No auto-revalidation (static data)
export const usePageById = (id: string | null) =>
  useSWRImmutable<Page>(id ? `/api/v3/pages/${id}` : null, fetcher);

Testing (apps/app Specific)

Mocking Next.js Router

import { mockDeep } from 'vitest-mock-extended';
import type { NextRouter } from 'next/router';

const createMockRouter = (overrides = {}) => {
  const mock = mockDeep<NextRouter>();
  mock.pathname = '/test';
  mock.push.mockResolvedValue(true);
  return Object.assign(mock, overrides);
};

vi.mock('next/router', () => ({
  useRouter: () => createMockRouter(),
}));

Testing with Jotai

import { Provider } from 'jotai';
import { useHydrateAtoms } from 'jotai/utils';

const HydrateAtoms = ({ initialValues, children }) => {
  useHydrateAtoms(initialValues);
  return children;
};

const renderWithJotai = (ui, initialValues = []) => render(
  <Provider>
    <HydrateAtoms initialValues={initialValues}>{ui}</HydrateAtoms>
  </Provider>
);

// Usage
renderWithJotai(<PageHeader />, [[currentPageAtom, mockPage]]);

Testing SWR

import { SWRConfig } from 'swr';

const wrapper = ({ children }) => (
  <SWRConfig value={{ dedupingInterval: 0, provider: () => new Map() }}>
    {children}
  </SWRConfig>
);

const { result } = renderHook(() => usePageById('123'), { wrapper });

Path Aliases

Always use ~/ for imports:

import { PageService } from '~/server/services/PageService';
import { currentPageAtom } from '~/states/page/page-atoms';

Summary

1. Next.js: .page.tsx suffix, getLayout for layouts
2. Jotai: states/ global, features/*/client/states/ feature-scoped
3. SWR: stores-universal/, null key for conditional fetch
4. Testing: Mock router, hydrate Jotai, wrap SWR config
5. Imports: Always ~/ path alias