frontend-dev-guidelines

Original source / Raw SKILL.md

---
name: frontend-dev-guidelines
description: Frontend development guidelines for ActionPhase React/TypeScript application. Modern patterns including Suspense, lazy loading, useSuspenseQuery, file organization with features directory, Tailwind CSS styling with custom UI components, React Router, dark mode with CSS variables, performance optimization, and TypeScript best practices. Use when creating components, pages, features, fetching data, styling, routing, or working with frontend code.
---

# Frontend Development Guidelines

## Purpose

Comprehensive guide for modern React development, emphasizing Suspense-based data fetching, lazy loading, proper file organization, and performance optimization.

## When to Use This Skill

- Creating new components or pages
- Building new features
- Fetching data with TanStack Query (React Query)
- Setting up routing with React Router
- Styling components with Tailwind CSS and UI component library
- Implementing dark mode with CSS variables
- Performance optimization
- Organizing frontend code
- TypeScript best practices

---

## Quick Start

### New Component Checklist

Creating a component? Follow this checklist:

- [ ] Use `React.FC<Props>` pattern with TypeScript
- [ ] Lazy load if heavy component: `React.lazy(() => import())`
- [ ] Wrap in `<SuspenseLoader>` for loading states
- [ ] Use `useSuspenseQuery` for data fetching
- [ ] Import aliases: `@/` (resolves to src/)
- [ ] Use UI component library: `@/components/ui`
- [ ] Style with Tailwind classes and CSS variables for dark mode
- [ ] Use `useCallback` for event handlers passed to children
- [ ] Default export at bottom
- [ ] No early returns with loading spinners
- [ ] Use toast/notification pattern for user feedback

### New Feature Checklist

Creating a feature? Set up this structure:

- [ ] Create `features/{feature-name}/` directory
- [ ] Create subdirectories: `api/`, `components/`, `hooks/`, `helpers/`, `types/`
- [ ] Create API service file: `api/{feature}Api.ts`
- [ ] Set up TypeScript types in `types/`
- [ ] Create route in `routes/{feature-name}/index.tsx`
- [ ] Lazy load feature components
- [ ] Use Suspense boundaries
- [ ] Export public API from feature `index.ts`

---

## Import Aliases Quick Reference

| Alias | Resolves To | Example |
|-------|-------------|---------|
| `@/` | `src/` | `import { api } from '@/lib/api'` |

ActionPhase uses the `@/` alias for all imports from the src directory. No other aliases are configured.

---

## Common Imports Cheatsheet

```typescript
// React & Lazy Loading
import React, { useState, useCallback, useMemo } from 'react';
const Heavy = React.lazy(() => import('./Heavy'));

// UI Components (ActionPhase)
import { Button, Input, Card, CardBody, Badge, Alert, Spinner } from '@/components/ui';

// TanStack Query (React Query - Suspense)
import { useSuspenseQuery, useQueryClient } from '@tanstack/react-query';

// React Router
import { Route, Routes, Navigate, useNavigate, useParams } from 'react-router-dom';

// Project Components
import { SuspenseLoader } from '@/components/SuspenseLoader';

// Auth & Hooks
import { useAuth } from '@/contexts/AuthContext';
import { api } from '@/lib/api';

// Types
import type { Game, Character, Message } from '@/types';
```

---

## Topic Guides

### 🎨 Component Patterns

**Modern React components use:**
- `React.FC<Props>` for type safety
- `React.lazy()` for code splitting
- `SuspenseLoader` for loading states
- Named const + default export pattern

**Key Concepts:**
- Lazy load heavy components (DataGrid, charts, editors)
- Always wrap lazy components in Suspense
- Use SuspenseLoader component (with fade animation)
- Component structure: Props → Hooks → Handlers → Render → Export

**[📖 Complete Guide: resources/component-patterns.md](resources/component-patterns.md)**

---

### 📊 Data Fetching

**PRIMARY PATTERN: useSuspenseQuery**
- Use with Suspense boundaries
- Cache-first strategy (check grid cache before API)
- Replaces `isLoading` checks
- Type-safe with generics

**API Service Layer:**
- Create `features/{feature}/api/{feature}Api.ts`
- Use `apiClient` axios instance
- Centralized methods per feature
- Route format: `/form/route` (NOT `/api/form/route`)

**[📖 Complete Guide: resources/data-fetching.md](resources/data-fetching.md)**

---

### 📁 File Organization

**features/ vs components/:**
- `features/`: Domain-specific (posts, comments, auth)
- `components/`: Truly reusable (SuspenseLoader, CustomAppBar)

**Feature Subdirectories:**
```
features/
  my-feature/
    api/          # API service layer
    components/   # Feature components
    hooks/        # Custom hooks
    helpers/      # Utility functions
    types/        # TypeScript types
```

**[📖 Complete Guide: resources/file-organization.md](resources/file-organization.md)**

---

### 🎨 Styling

**Primary Methods:**
- Use UI Component Library (`@/components/ui`) for standard elements
- Use Tailwind CSS for layout and custom styling
- Use CSS variables for dark mode support

**Dark Mode Rules:**
```tsx
// ✅ CORRECT - CSS variables
<div className="bg-bg-primary text-text-primary">

// ❌ WRONG - Manual dark classes
<div className="bg-white dark:bg-gray-800">
```

**Component Priority:**
1. Use UI components when available (Button, Input, Card, etc.)
2. Use Tailwind for layout (flex, grid, spacing)
3. Use CSS variables for colors (always)

**[📖 Complete Guide: resources/styling-guide.md](resources/styling-guide.md)**

---

### 🛣️ Routing

**React Router - Traditional Setup:**
- Routes defined in `App.tsx`
- Protected routes with `AuthContext`
- Lazy load pages for code splitting
- Use `useNavigate` for programmatic navigation

**Example:**
```typescript
import { Route, Routes, Navigate } from 'react-router-dom';
import { lazy } from 'react';

const GamePage = lazy(() => import('@/pages/GamePage'));

// In App.tsx
<Routes>
  <Route path="/games/:id" element={
    <ProtectedRoute>
      <GamePage />
    </ProtectedRoute>
  } />
</Routes>
```

**[📖 Complete Guide: resources/routing-guide.md](resources/routing-guide.md)**

---

### ⏳ Loading & Error States

**CRITICAL RULE: No Early Returns**

```typescript
// ❌ NEVER - Causes layout shift
if (isLoading) {
    return <LoadingSpinner />;
}

// ✅ ALWAYS - Consistent layout
<SuspenseLoader>
    <Content />
</SuspenseLoader>
```

**Why:** Prevents Cumulative Layout Shift (CLS), better UX

**Error Handling:**
- Use toast notifications or Alert component for user feedback
- NEVER `react-toastify`
- TanStack Query `onError` callbacks

**[📖 Complete Guide: resources/loading-and-error-states.md](resources/loading-and-error-states.md)**

---

### ⚡ Performance

**Optimization Patterns:**
- `useMemo`: Expensive computations (filter, sort, map)
- `useCallback`: Event handlers passed to children
- `React.memo`: Expensive components
- Debounced search (300-500ms)
- Memory leak prevention (cleanup in useEffect)

**[📖 Complete Guide: resources/performance.md](resources/performance.md)**

---

### 📘 TypeScript

**Standards:**
- Strict mode, no `any` type
- Explicit return types on functions
- Type imports: `import type { User } from '~types/user'`
- Component prop interfaces with JSDoc

**[📖 Complete Guide: resources/typescript-standards.md](resources/typescript-standards.md)**

---

### 🔧 Common Patterns

**Covered Topics:**
- React Hook Form with Zod validation
- DataGrid wrapper contracts
- Dialog component standards
- `useAuth` hook for current user
- Mutation patterns with cache invalidation

**[📖 Complete Guide: resources/common-patterns.md](resources/common-patterns.md)**

---

### 📚 Complete Examples

**Full working examples:**
- Modern component with all patterns
- Complete feature structure
- API service layer
- Route with lazy loading
- Suspense + useSuspenseQuery
- Form with validation

**[📖 Complete Guide: resources/complete-examples.md](resources/complete-examples.md)**

---

## Navigation Guide

| Need to... | Read this resource |
|------------|-------------------|
| Create a component | [component-patterns.md](resources/component-patterns.md) |
| Fetch data | [data-fetching.md](resources/data-fetching.md) |
| Organize files/folders | [file-organization.md](resources/file-organization.md) |
| Style components | [styling-guide.md](resources/styling-guide.md) |
| Set up routing | [routing-guide.md](resources/routing-guide.md) |
| Handle loading/errors | [loading-and-error-states.md](resources/loading-and-error-states.md) |
| Optimize performance | [performance.md](resources/performance.md) |
| TypeScript types | [typescript-standards.md](resources/typescript-standards.md) |
| Forms/Auth/DataGrid | [common-patterns.md](resources/common-patterns.md) |
| See full examples | [complete-examples.md](resources/complete-examples.md) |

---

## Core Principles

1. **Lazy Load Everything Heavy**: Routes, DataGrid, charts, editors
2. **Suspense for Loading**: Use SuspenseLoader, not early returns
3. **useSuspenseQuery**: Primary data fetching pattern for new code
4. **Features are Organized**: api/, components/, hooks/, helpers/ subdirs
5. **Styles Based on Size**: <100 inline, >100 separate
6. **Import Aliases**: Use @/ for all src/ imports
7. **No Early Returns**: Prevents layout shift
8. **Toast/Alert**: For all user notifications

---

## Quick Reference: File Structure

```
src/
  features/
    my-feature/
      api/
        myFeatureApi.ts       # API service
      components/
        MyFeature.tsx         # Main component
        SubComponent.tsx      # Related components
      hooks/
        useMyFeature.ts       # Custom hooks
        useSuspenseMyFeature.ts  # Suspense hooks
      helpers/
        myFeatureHelpers.ts   # Utilities
      types/
        index.ts              # TypeScript types
      index.ts                # Public exports

  components/
    SuspenseLoader/
      SuspenseLoader.tsx      # Reusable loader
    CustomAppBar/
      CustomAppBar.tsx        # Reusable app bar

  routes/
    my-route/
      index.tsx               # Route component
      create/
        index.tsx             # Nested route
```

---

## Modern Component Template (Quick Copy)

```typescript
import React, { useState, useCallback } from 'react';
import { Box, Paper } from '@mui/material';
import { useSuspenseQuery } from '@tanstack/react-query';
import { featureApi } from '../api/featureApi';
import type { FeatureData } from '~types/feature';

interface MyComponentProps {
    id: number;
    onAction?: () => void;
}

export const MyComponent: React.FC<MyComponentProps> = ({ id, onAction }) => {
    const [state, setState] = useState<string>('');

    const { data } = useSuspenseQuery({
        queryKey: ['feature', id],
        queryFn: () => featureApi.getFeature(id),
    });

    const handleAction = useCallback(() => {
        setState('updated');
        onAction?.();
    }, [onAction]);

    return (
        <Box sx={{ p: 2 }}>
            <Paper sx={{ p: 3 }}>
                {/* Content */}
            </Paper>
        </Box>
    );
};

export default MyComponent;
```

For complete examples, see [resources/complete-examples.md](resources/complete-examples.md)

---

## Related Skills

- **error-tracking**: Error tracking with Sentry (applies to frontend too)
- **backend-dev-guidelines**: Backend API patterns that frontend consumes

---

**Skill Status**: Modular structure with progressive loading for optimal context management