Clean Blog system

- Improved the blog posts
- Add a test to visit the blog index
- Add Tailwind Typography for the markdown blog posts

lib/blogApi.ts

@@ -0,0 +1,75 @@
+// This is a set of functions for the Blog system.
+
+import { bundleMDX } from 'mdx-bundler';
+import fs from 'node:fs';
+import { join } from 'node:path';
+import matter from 'gray-matter';
+
+const postsDirectory = join(process.cwd(), '_posts');
+
+export function getPostSlugs(): string[] {
+  return fs.readdirSync(postsDirectory);
+}
+type Items = {
+  [key: string]: string;
+};
+
+export function getPostBySlug(slug: string, fields: string[] = []): Items {
+  const realSlug = slug.replace(/\.mdx$/, '');
+  const fullPath = join(postsDirectory, `${realSlug}.mdx`);
+  const fileContents = fs.readFileSync(fullPath, 'utf8');
+  const {
+    data,
+    content,
+  }: {
+    data: Items;
+    content: string;
+  } = matter(fileContents);
+
+  const items: Items = {};
+
+  // Ensure only the minimal needed data is exposed
+  for (const field of fields) {
+    if (field === 'slug') {
+      items[field] = realSlug;
+    }
+    if (field === 'content') {
+      items[field] = content;
+    }
+
+    if (typeof data[field] !== 'undefined') {
+      items[field] = data[field];
+    }
+  }
+
+  return items;
+}
+
+export function getAllPosts(fields: string[] = []): Items[] {
+  const slugs = getPostSlugs();
+  return (
+    slugs
+      .map((slug) => getPostBySlug(slug, fields))
+      // sort posts by date in descending order
+      .sort((post1, post2) => (post1.date > post2.date ? -1 : 1))
+  );
+}
+
+type Parameters_ = {
+  slug: string;
+  frontmatter: { [key: string]: any };
+  code: string;
+};
+
+export async function getPostData(slug: string): Promise<Parameters_> {
+  const realSlug = slug.replace(/\.mdx$/, '');
+  const fullPath = join(postsDirectory, `${realSlug}.mdx`);
+  const source = fs.readFileSync(fullPath, 'utf8');
+  const { code, frontmatter } = await bundleMDX({ source: source });
+
+  return {
+    slug,
+    frontmatter,
+    code,
+  };
+}