component-patterns

# Component Patterns

Implement React component patterns for building reusable, maintainable components.

## Quick Start

Use composition for most cases, custom hooks for shared logic, and compound components for flexible APIs.

## Instructions

### Composition Pattern

The default pattern for building flexible components.

**Basic composition:**
```tsx
function Card({ children }) {
  return <div className="card">{children}</div>;
}

function CardHeader({ children }) {
  return <div className="card-header">{children}</div>;
}

function CardBody({ children }) {
  return <div className="card-body">{children}</div>;
}

// Usage
<Card>
  <CardHeader>Title</CardHeader>
  <CardBody>Content</CardBody>
</Card>
```

**With props:**
```tsx
interface ButtonProps {
  variant?: 'primary' | 'secondary';
  size?: 'sm' | 'md' | 'lg';
  children: React.ReactNode;
}

function Button({ variant = 'primary', size = 'md', children }: ButtonProps) {
  return (
    <button className={`btn btn-${variant} btn-${size}`}>
      {children}
    </button>
  );
}
```

### Custom Hooks Pattern

Extract and reuse stateful logic across components.

**Basic custom hook:**
```tsx
function useToggle(initialValue = false) {
  const [value, setValue] = useState(initialValue);
  
  const toggle = useCallback(() => {
    setValue(v => !v);
  }, []);
  
  return [value, toggle] as const;
}

// Usage
function Component() {
  const [isOpen, toggleOpen] = useToggle();
  return <button onClick={toggleOpen}>{isOpen ? 'Close' : 'Open'}</button>;
}
```

**Data fetching hook:**
```tsx
function useFetch<T>(url: string) {
  const [data, setData] = useState<T | null>(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<Error | null>(null);
  
  useEffect(() => {
    fetch(url)
      .then(res => res.json())
      .then(setData)
      .catch(setError)
      .finally(() => setLoading(false));
  }, [url]);
  
  return { data, loading, error };
}
```

**Form hook:**
```tsx
function us