import { readdir } from "node:fs/promises";
import { YAML } from "bun";
import metadata from "./metadata.json";
import templateRaw from "./templates/post.html" with { type: "text" };
import homeRaw from "./templates/home.html" with { type: "text" };

const year = new Date().getFullYear().toString();
const applyVars = (raw: unknown) => (raw as string)
  .replaceAll("[[SITE]]", metadata.title)
  .replaceAll("[[NAME]]", metadata.name)
  .replaceAll("[[TIMEZONE]]", metadata.timezone)
  .replaceAll("[[YEAR]]", year);

const template = applyVars(templateRaw);
const home = applyVars(homeRaw);

const posts = await readdir("./posts");
const postLinks: {
  title: string;
  date: Date;
  link: string;
}[] = [];
const defaultFrontmatter = {
  title: "Untitled",
  desc: "",
  date: "0000-00-00", // YYYY-MM-DD
  draft: true,
};

function fetchFrontmatter(raw?: string) {
  try {
    if (!raw) throw new Error("No frontmatter found.");
    const parsed = { ...defaultFrontmatter, ...(YAML.parse(raw) as typeof defaultFrontmatter) };
    return { ...parsed, date: new Date(parsed.date) };
  } catch {
    console.warn("Failed to parse frontmatter. Using default values.");
    return { ...defaultFrontmatter, date: new Date(NaN) };
  }
}

await Promise.all(posts.map(async (post) => {
  const raw = (await Bun.file(`./posts/${post}`).text()).split("^---");

  const content = raw.at(-1) || "_No content_";
  const frontmatter = fetchFrontmatter(raw.at(0));
  
  const html = Bun.markdown.html(content, {
    autolinks: true,
    headings: true,
    underline: true,
    tagFilter: true,
  });
  const render = template
    .replaceAll("[[TITLE]]", `${metadata.title} - ${frontmatter.title}`)
    .replaceAll("[[POST_TITLE]]", frontmatter.title)
    .replaceAll("[[DATE]]", frontmatter.date.toDateString())
    .replaceAll("[[REVISIONS]]", `${metadata.revisions}/${post}`)
    .replaceAll("[[DESC]]", frontmatter.desc)
    .replace("[[CONTENT]]", html);
  
  await Bun.write(`./dist/posts/${post.replace(".md", ".html")}`, render);

  if (!frontmatter.draft) postLinks.push({
    title: frontmatter.title,
    date: frontmatter.date,
    link: `/posts/${post.replace(".md", ".html")}`,
  });
  
  console.log(`Built page for ${frontmatter.draft ? 'draft' : 'post'}: ${frontmatter.title}`);
  // TODO: table of contents generation
}));

const parsedPosts = postLinks
  .sort((a, b) => b.date.getTime() - a.date.getTime())
  .map((post) => `<li><a href="${post.link}">${post.title}</a> - <i>${post.date.toDateString()}</i></li>`)
  .join("\n");
const render = home
  .replace("[[ABOUT]]", Bun.markdown.html(metadata.description))
  .replace("[[MAIN]]", metadata.main)
  .replace("[[POSTS]]", parsedPosts);

await Bun.write("./dist/index.html", render);