メタデータ (Metadata API)

// app/layout.tsx — 静的メタデータ
import type { Metadata } from 'next';

export const metadata: Metadata = {
  title: {
    default: 'My App',
    template: '%s | My App', // 子ページ: "記事タイトル | My App"
  },
  description: 'アプリの説明',
  openGraph: {
    title: 'My App',
    description: 'OGP説明',
    images: ['/og-image.png'],
  },
  twitter: { card: 'summary_large_image' },
};

// app/blog/[slug]/page.tsx — 動的メタデータ
export async function generateMetadata({
  params,
}: {
  params: Promise<{ slug: string }>;
}): Promise<Metadata> {
  const { slug } = await params;
  const post = await getPost(slug);

  return {
    title: post.title,
    description: post.excerpt,
    openGraph: {
      images: [post.coverImage],
    },
  };
}