import of old blog posts

lib/posts.ts

@@ -89,6 +89,16 @@ export function getAllPostIds() {
   }
 }
 
+export function getAdjacentPosts(slug: string): { prev: PostMeta | null; next: PostMeta | null } {
+  const posts = getSortedPostsData(); // newest → oldest
+  const index = posts.findIndex((p) => p.id === slug);
+  if (index === -1) return { prev: null, next: null };
+  return {
+    prev: posts[index + 1] ?? null, // older
+    next: posts[index - 1] ?? null, // newer
+  };
+}
+
 export async function getPostData(id: string): Promise<PostData> {
   const fullPath = path.join(postsDirectory, `${id}.mdx`);
   if (!fs.existsSync(fullPath)) notFound();