vercel-development

What this skill does

# Vercel Development Best Practices

## Overview

This skill provides comprehensive guidelines for developing and deploying applications on Vercel, with a focus on Next.js, React Server Components, Edge Functions, and the Vercel AI SDK.

## Core Principles

- Write concise, technical TypeScript code with accurate examples
- Use functional and declarative programming patterns; avoid classes
- Minimize 'use client', 'useEffect', and 'setState'; favor React Server Components (RSC)
- Implement responsive design with Tailwind CSS using mobile-first approach
- Optimize for Core Web Vitals and performance

## Project Structure

```
my-app/
├── app/                    # App Router pages and layouts
│   ├── (auth)/            # Route groups
│   ├── api/               # API routes
│   ├── layout.tsx         # Root layout
│   └── page.tsx           # Home page
├── components/            # React components
│   ├── ui/               # UI primitives
│   └── features/         # Feature components
├── lib/                   # Utility functions
├── hooks/                 # Custom React hooks
├── types/                 # TypeScript types
├── public/               # Static assets
└── vercel.json           # Vercel configuration
```

## Next.js App Router Guidelines

### File Naming Conventions
- Use lowercase with dashes for directories (e.g., `components/auth-wizard`)
- Prefer named exports for components and functions
- Use `page.tsx` for route pages, `layout.tsx` for layouts
- Use `loading.tsx` for loading states, `error.tsx` for error boundaries

### Server Components (Default)
```typescript
// app/users/page.tsx
import { getUsers } from '@/lib/data';

export default async function UsersPage() {
  const users = await getUsers();

  return (
    <main>
      <h1>Users</h1>
      <ul>
        {users.map(user => (
          <li key={user.id}>{user.name}</li>
        ))}
      </ul>
    </main>
  );
}
```

### Client Components (When Needed)
```typescript
'use client';

import { useState } from 'react';

export function Counter() {
  const [count, setCount] = useState(0);

  return (
    <button onClick={() => setCount(c => c + 1)}>
      Count: {count}
    </button>
  );
}
```

## TypeScript Standards

### Type Definitions
```typescript
// Use interfaces over types for object shapes
interface User {
  id: string;
  name: string;
  email: string;
  createdAt: Date;
}

// Use types for unions and complex types
type Status = 'pending' | 'active' | 'inactive';

// Avoid enums; use const objects instead
const STATUS = {
  PENDING: 'pending',
  ACTIVE: 'active',
  INACTIVE: 'inactive',
} as const;

type StatusValue = typeof STATUS[keyof typeof STATUS];
```

### Component Props
```typescript
interface ButtonProps {
  children: React.ReactNode;
  variant?: 'primary' | 'secondary' | 'ghost';
  size?: 'sm' | 'md' | 'lg';
  disabled?: boolean;
  onClick?: () => void;
}

export function Button({
  children,
  variant = 'primary',
  size = 'md',
  disabled = false,
  onClick,
}: ButtonProps) {
  // Implementation
}
```

## API Routes

### Route Handlers
```typescript
// app/api/users/route.ts
import { NextRequest, NextResponse } from 'next/server';
import { z } from 'zod';

const CreateUserSchema = z.object({
  name: z.string().min(1),
  email: z.string().email(),
});

export async function GET(request: NextRequest) {
  const users = await getUsers();
  return NextResponse.json(users);
}

export async function POST(request: NextRequest) {
  try {
    const body = await request.json();
    const validated = CreateUserSchema.parse(body);

    const user = await createUser(validated);
    return NextResponse.json(user, { status: 201 });
  } catch (error) {
    if (error instanceof z.ZodError) {
      return NextResponse.json(
        { error: 'Validation failed', details: error.errors },
        { status: 400 }
      );
    }
    return NextResponse.json(
      { error: 'Internal server error' },
      { status: 500 }
    );
  }
}
```

### Edge Runtime
```typescript
// app/api/edge-function/route.ts
export const runtime = 'edge';

export async function GET(request: Request) {
  return new Response(JSON.stringify({ message: 'Hello from the edge!' }), {
    headers: { 'Content-Type': 'application/json' },
  });
}
```

## Vercel AI SDK Integration

### Streaming Chat UI
```typescript
'use client';

import { useChat } from 'ai/react';

export function Chat() {
  const { messages, input, handleInputChange, handleSubmit, isLoading } = useChat({
    api: '/api/chat',
  });

  return (
    <div className="flex flex-col h-full">
      <div className="flex-1 overflow-y-auto">
        {messages.map(message => (
          <div key={message.id} className={message.role === 'user' ? 'text-right' : ''}>
            <p>{message.content}</p>
          </div>
        ))}
      </div>

      <form onSubmit={handleSubmit}>
        <input
          value={input}
          onChange={handleInputChange}
          placeholder="Type a message..."
          disabled={isLoading}
        />
      </form>
    </div>
  );
}
```

### AI API Route
```typescript
// app/api/chat/route.ts
import { openai } from '@ai-sdk/openai';
import { streamText } from 'ai';

export async function POST(request: Request) {
  const { messages } = await request.json();

  const result = await streamText({
    model: openai('gpt-4-turbo'),
    messages,
    system: 'You are a helpful assistant.',
  });

  return result.toDataStreamResponse();
}
```

### Error Handling for AI
```typescript
import { openai } from '@ai-sdk/openai';
import { streamText } from 'ai';

export async function POST(request: Request) {
  try {
    const { messages } = await request.json();

    const result = await streamText({
      model: openai('gpt-4-turbo'),
      messages,
    });

    return result.toDataStreamResponse();
  } catch (error) {
    // Handle rate limiting
    if (error.message?.includes('rate limit')) {
      return new Response('Rate limit exceeded. Please try again later.', {
        status: 429,
      });
    }

    // Handle quota exceeded
    if (error.message?.includes('quota')) {
      return new Response('API quota exceeded.', { status: 402 });
    }

    // Fallback to alternative model
    console.error('Primary model failed:', error);
    return new Response('Service temporarily unavailable.', { status: 503 });
  }
}
```

## Data Fetching

### Server-Side Data Fetching
```typescript
// Fetch data in Server Components
async function getData() {
  const res = await fetch('https://api.example.com/data', {
    next: { revalidate: 3600 }, // Cache for 1 hour
  });

  if (!res.ok) {
    throw new Error('Failed to fetch data');
  }

  return res.json();
}

export default async function Page() {
  const data = await getData();
  return <div>{/* Render data */}</div>;
}
```

### URL State Management
```typescript
// Use URL query parameters for server state
import { useSearchParams, useRouter } from 'next/navigation';

export function Filters() {
  const searchParams = useSearchParams();
  const router = useRouter();

  const updateFilter = (key: string, value: string) => {
    const params = new URLSearchParams(searchParams);
    params.set(key, value);
    router.push(`?${params.toString()}`);
  };

  return (/* Filter UI */);
}
```

## Performance Optimization

### Image Optimization
```typescript
import Image from 'next/image';

export function Hero() {
  return (
    <Image
      src="/hero.jpg"
      alt="Hero image"
      width={1200}
      height={600}
      priority // Load immediately for LCP
      placeholder="blur"
      blurDataURL="data:image/jpeg;base64,..."
    />
  );
}
```

### Dynamic Imports
```typescript
import dynamic from 'next/dynamic';

// Lazy load heavy components
const HeavyChart = dynamic(() => import('@/components/heavy-chart'), {
  loading: () => <div>Loading chart...</div>,
  ssr: false, // Disable SSR if needed
});
```

### Suspense Boundaries
```typescript
import { Suspense } from 'react';

export default