import showdown from "showdown";
import yaml from "yaml";
import { promises as fs } from "fs";

const posts = await fs.readdir("posts");

function splitPostHeader(postData: string): [string, string] {
  if (postData.startsWith("---\n")) {
    const headerEndIndex = postData.indexOf("\n---\n", 4);

    return [
      postData.substring(4, headerEndIndex),
      postData.substring(headerEndIndex + 5),
    ];
  }
  return ["", postData];
}

await fs.rm("build", { recursive: true });
await fs.mkdir("build");
declare interface PostMetadata {
  name: string;
  unlisted?: boolean;
  tags?: Array<string>;
  description?: string;
}

const baseTemplate = await fs.readFile("template.html", { encoding: "utf-8" });

function makeHtmlForPost(postMetadata: PostMetadata, markdown: string): string {
  const converter = new showdown.Converter();
  const htmlPostBody = converter.makeHtml(markdown);
  const variables = {
    postBody: htmlPostBody,
    title: postMetadata.name,
  };
  return baseTemplate.replace(
    /%([a-zA-Z]+)%/g,
    (_, match) => variables[match] ?? `Missing variable: ${match}`,
  );
}

for (let postPath of posts) {
  const totalPostPath = `posts/${postPath}`;
  if (!postPath.endsWith(".md")) {
    await fs.copyFile(totalPostPath, `build/${postPath}`);
    continue;
  }
  const postText = await fs.readFile(totalPostPath, { encoding: "utf-8" });
  const [postHeader, postBody] = splitPostHeader(postText);
  const postMetadata = yaml.parse(postHeader) as PostMetadata;
  const postHtml = makeHtmlForPost(postMetadata, postBody);
  const targetPath = `build/${postPath.replace(".md", ".html")}`;
  fs.writeFile(targetPath, postHtml, { encoding: "utf-8" });
}