loadGreyMatterPost.ts

import fs from "fs";
import path from "path";

const POSTS_PATH = path.join(process.cwd(), "posts");

function loadGreyMatterPost(params) {
  if (
    params === undefined ||
    params.year === undefined ||
    params.slug === undefined
  ) {
    throw new Error("Not Found");
  }

  const posts = fs
    .readdirSync(POSTS_PATH)
    .filter((path) => /\.mdx?$/.test(path))
    .map((path) => fs.readFileSync(POSTS_PATH + "/" + path))
    .map((source) => matter(source));

  const post = posts.find(
    (post) => post.data.path === `/posts/${params.year}/${params.slug}`
  );

  if (post === undefined) {
    throw new Error("Not Found");
  }

  return [post, posts];
}