md-blog/post-build.ts

import fs from "fs";
import process from "process";
import { Feed } from "feed";
import articlesConfig from "./articles/config.json";

function getFiles(dir: string): string[] {
  return fs.readdirSync(dir).flatMap((name) => {
    const path = `${dir}/${name}`;
    if (fs.statSync(path).isDirectory()) {
      return getFiles(path);
    } else {
      return [path];
    }
  });
}

const METADATA_BLOCK_REGEX = /^---\n([\s\S]*?)---\n/m;
const METADATA_REGEX = /^(\w+):(.*)$/gm;

function readArticleMetadata(path: string): Record<string, string> | null {
  const content = fs.readFileSync(path, { encoding: "utf8" });
  const match: RegExpExecArray | null = METADATA_BLOCK_REGEX.exec(content);
  if (!match?.[1]) {
    console.warn(`No metadata for: ${path}`);
    return null;
  }
  let subMatch: RegExpExecArray | null = null;
  const metadata: Record<string, string> = {
    path: path.replaceAll("/index.md", ""),
  };
  do {
    subMatch = METADATA_REGEX.exec(match[1]);
    if (subMatch?.[1] && subMatch[2]) {
      metadata[subMatch[1]] = subMatch[2].trim();
    }
  } while (subMatch);
  return metadata;
}

function formatArticlePage(
  metadata: Record<string, string>,
  baseHtml: string,
): string {
  let outHtml = baseHtml;
  outHtml = outHtml.replace(/<.*?property="og:url".*?>/gm, "");
  outHtml = outHtml.replace(
    /<\/head>/gm,
    `<meta property="og:url" content="${articlesConfig.base_url}${metadata.path}/">\n</head>`,
  );
  const blog_title = articlesConfig.title.replace(/(<([^>]+)>)/gi, "").trim();
  if (metadata.title) {
    const title = metadata.title.replace(/(<([^>]+)>)/gi, "").trim();
    outHtml = outHtml.replace(
      /<title>.*?<\/title>/gm,
      `<title>${blog_title} — ${title}</title>`,
    );
    outHtml = outHtml.replace(/<.*?property="og:title".*?>/gm, "");
    outHtml = outHtml.replace(
      /<\/head>/gm,
      `<meta property="og:title" content="${title}">\n</head>`,
    );
    outHtml = outHtml.replace(/<.*?property="og:description".*?>/gm, "");
    outHtml = outHtml.replace(
      /<\/head>/gm,
      `<meta property="og:description" content="${blog_title}">\n</head>`,
    );
  }
  if (metadata.thumbnail) {
    outHtml = outHtml.replace(/<.*?property="og:image".*?>/gm, "");
    outHtml = outHtml.replace(
      /<\/head>/gm,
      `<meta property="og:image" content="${metadata.thumbnail.replace("./", articlesConfig.base_url + metadata.path + "/")}">\n</head>`,
    );
  }
  return outHtml;
}

function addFeedArticle(metadata: Record<string, string>, feed: Feed) {
  if (metadata.draft !== "true") {
    feed.addItem({
      title: metadata.title.replace(/(<([^>]+)>)/gi, "").trim(),
      id: metadata.path,
      link: `${articlesConfig.base_url}${metadata.path}/`,
      date: new Date(Date.parse(metadata.date)),
      image: metadata.thumbnail.replace(
        "./",
        articlesConfig.base_url + metadata.path + "/",
      ),
    });
  }
}

const indexContent = fs.readFileSync("dist/index.html", { encoding: "utf8" });

if (!indexContent) {
  console.error("Could not read dist/index.html");
  process.exit(1);
}

const metadatas = getFiles("articles")
  .filter((path) => /\/index.md$/.exec(path))
  .map((path) => readArticleMetadata(path))
  .filter((metadata) => !!metadata);

const feed = new Feed({
  title: articlesConfig.title.replace(/(<([^>]+)>)/gi, "").trim(),
  id: articlesConfig.base_url,
  link: articlesConfig.base_url,
  language: articlesConfig.lang,
  favicon: articlesConfig.base_url + "articles/favicon.ico",
  generator: "md-blog",
  feedLinks: {
    json: articlesConfig.base_url + "feed.json",
    atom: articlesConfig.base_url + "atom.xml",
    rss: articlesConfig.base_url + "rss",
  },
  updated: new Date(
    Math.max(
      0,
      ...metadatas
        .filter((metadata) => metadata.draft !== "true")
        .map((metadata) => Date.parse(metadata.date)),
    ),
  ),
});

metadatas.forEach((metadata) => {
  fs.writeFileSync(
    `dist/${metadata.path}/index.html`,
    formatArticlePage(metadata, indexContent),
  );
  console.info(`Wrote dist/${metadata.path}/index.html`);
  addFeedArticle(metadata, feed);
});

fs.writeFileSync("dist/feed.json", feed.json1());
console.info(`Wrote dist/feed.json`);
fs.writeFileSync("dist/atom.xml", feed.atom1());
console.info(`Wrote dist/atom.xml`);
fs.writeFileSync("dist/rss.xml", feed.rss2());
console.info(`Wrote dist/rss.xml`);