import fs from "fs";
import path from "path";
import { renderToStaticMarkup } from "react-dom/server";
import matter from "gray-matter";
import { serialize } from "next-mdx-remote/serialize";
import { minify } from "terser";
import { compiler } from "markdown-to-jsx";
import removeMarkdown from "remove-markdown";
import sanitizeHtml from "sanitize-html";
import readingTime from "reading-time";
import { baseUrl } from "./config";
import { NOTES_DIR } from "./config/constants";

// remark/rehype markdown plugins
import remarkGfm from "remark-gfm";
import rehypeSlug from "rehype-slug";
import rehypePrism from "rehype-prism-plus";

import type { MinifyOptions } from "terser";
import type { NoteType } from "../types";

// returns all .mdx files in NOTES_DIR (without .mdx extension)
export const getNoteSlugs = () =>
  fs
    .readdirSync(path.join(process.cwd(), NOTES_DIR))
    .filter((file) => /\.mdx$/.test(file))
    .map((noteFile) => noteFile.replace(/\.mdx$/, ""));

// returns front matter and/or *raw* markdown contents of a given slug
export const getNoteData = (slug: string): Omit<NoteType, "source"> & { content: string } => {
  const fullPath = path.join(process.cwd(), NOTES_DIR, `${slug}.mdx`);
  const rawContent = fs.readFileSync(fullPath, "utf8");
  const { data, content } = matter(rawContent);

  // carefully allow VERY limited markdown in post titles...
  const htmlTitle = sanitizeHtml(
    renderToStaticMarkup(
      compiler(data.title, {
        forceInline: true,
        disableParsingRawHTML: true,
      })
    ),
    {
      allowedTags: ["code", "pre", "em", "strong", "del"],
    }
  );

  // return both the parsed YAML front matter (with a few amendments) and the raw, unparsed markdown content
  return {
    frontMatter: {
      ...(data as Omit<NoteType["frontMatter"], "slug" | "title" | "htmlTitle" | "permalink" | "date" | "readingMins">),
      // zero markdown title:
      title: removeMarkdown(data.title),
      // parsed markdown title:
      htmlTitle,
      slug,
      permalink: `${baseUrl}/notes/${slug}/`,
      date: new Date(data.date).toISOString(), // validate/normalize the date string provided from front matter
      readingMins: Math.ceil(readingTime(content).minutes),
    },
    content,
  };
};

// fully parses MDX into JS and returns *everything* about a note
export const getNote = async (slug: string): Promise<NoteType> => {
  const { frontMatter, content } = getNoteData(slug);
  const source = await serialize(content, {
    parseFrontmatter: false,
    mdxOptions: {
      remarkPlugins: [[remarkGfm, { singleTilde: false }]],
      rehypePlugins: [[rehypeSlug], [rehypePrism, { ignoreMissing: true }]],
    },
  });

  // HACK: next-mdx-remote v4 doesn't (yet?) minify compiled JSX output, see:
  // https://github.com/hashicorp/next-mdx-remote/pull/211#issuecomment-1013658514
  // ...so for now, let's do it manually (and conservatively) with terser when building for production.
  const terserOptions: MinifyOptions = {
    ecma: 2018,
    module: true,
    parse: {
      bare_returns: true,
    },
    compress: {
      defaults: true,
    },
    sourceMap: false,
  };
  const compiledSource =
    process.env.NEXT_PUBLIC_VERCEL_ENV === "production"
      ? (await minify(source.compiledSource, terserOptions)).code
      : source.compiledSource;

  return {
    frontMatter,
    source: {
      compiledSource,
    },
  };
};

// returns the front matter of ALL notes, sorted reverse chronologically
export const getAllNotes = () =>
  getNoteSlugs()
    .map((slug) => getNoteData(slug).frontMatter)
    .sort((note1: NoteType["frontMatter"], note2: NoteType["frontMatter"]) => (note1.date > note2.date ? -1 : 1));