import * as fs from 'fs';
import * as crypto from 'crypto';

import showdown from 'showdown';
import { footnotes, highlight, prettify, spoiler, video } from '$lib/showdown';
import { dither } from '$lib/img';

interface Metadata {
  title: string;
  hero?: string;
  series?: string;
  part?: number;
}

export interface Post extends Metadata {
  type: 'post';
  slug: string;
  date: string;
  readtime: number;
  html?: string;
}

export interface Note extends Metadata {
  type: 'note';
  slug: string;
  date: string;
  html?: string;
}

export type Article = Post | Note;

const converter = new showdown.Converter({
  tables: true,
  strikethrough: true,
  // `highlight` needs to be before `prettify`
  extensions: [footnotes, highlight, prettify, spoiler, video]
});

const calculateReadingTime = (text: string) => {
  const wordsPerMinute = 200;
  const words = text
    .trim()
    .split(/\s+/)
    .filter((word) => word.length > 0).length;

  return Math.ceil(words / wordsPerMinute) || 1;
};

const getContentData = (data: string, includeReadTime = true) => {
  // because there is no metadata extension, we need to read the lines
  const lines = data.split('\n');
  const metadataEnd = lines.indexOf('---', 1);
  const body = lines.slice(metadataEnd + 1, lines.length).join('\n');
  const metadata: Metadata = Object.fromEntries(
    lines.slice(1, metadataEnd).map((x: string) => x.split(/:(.*)/s).map((x) => x.trim()))
  ) as Metadata;

  const result = {
    ...metadata,
    html: converter.makeHtml(body)
  };

  if (includeReadTime) {
    return {
      ...result,
      readtime: Math.ceil(calculateReadingTime(body))
    };
  }

  return result;
};

const parseFilename = (file: string) => {
  const f = file.split('/')[1].split('.')[0].split('-');
  const [date, slug] = [f.splice(0, 3).join('-'), f.splice(0, 1)[0]];

  if (slug !== '[cid]') return [date, slug];

  const file_buffer = fs.readFileSync(file);
  const sum = crypto.createHash('sha256');
  sum.update(file_buffer);
  return [date, sum.digest('hex')];
};

const getPostFileList = () => [
  ...fs.readdirSync('_posts').map((x) => `_posts/${x}`),
  ...(process.env.SHOW_DRAFTS ? fs.readdirSync('_drafts').map((x) => `_drafts/${x}`) : [])
];

const getNoteFileList = () => {
  try {
    return fs.readdirSync('_notes').map((x) => `_notes/${x}`);
  } catch (e) {
    return [];
  }
};

const getPosts = (): Post[] => {
  const series: Record<string, string[]> = {};

  return getPostFileList()
    .map((file) => {
      const [date, slug] = parseFilename(file);
      const post = getContentData(fs.readFileSync(file, { encoding: 'utf-8' }), true);

      if (post.series) {
        if (post.series in series) series[post.series].push(date);
        else series[post.series] = [date];
      }

      return { ...post, slug, date, type: 'post' } as Post;
    })
    .map((post) => {
      if (post.series) {
        const part = series[post.series].findIndex((p) => p === post.date);
        post.part = part;
      }
      return post;
    });
};

const getNotes = (): Note[] => {
  const series: Record<string, string[]> = {};

  return getNoteFileList().map((file) => {
    const [date, slug] = parseFilename(file);
    const note = getContentData(fs.readFileSync(file, { encoding: 'utf-8' }), false);

    if (note.series) {
      if (note.series in series) series[note.series].push(date);
      else series[note.series] = [date];
    }

    return { ...note, slug, date, type: 'note' } as Note;
  });
};

const getPost = (snail: string) => getPosts().find((p) => p.slug === snail)!;
const getNote = (snail: string) => getNotes().find((n) => n.slug === snail)!;

const processHTML = (html: string) => {
  html = html.replace(
    /<img src="\/img\/(.*?)" alt="(.*?)"([^>]*)>/gi,
    (match, imgName, altText, attrs) => {
      const found = Object.entries(dither).find(([path, _]) => path.endsWith(imgName))?.[1];
      if (found) {
        return `<img src="${found.default.img.src}" alt="${altText}" data-original="${imgName}"${attrs}>`;
      }
      return match;
    }
  );

  const footnoteContents: Record<string, string> = {};
  html = html.replace(
    /<aside class="footnote-body" id="footnote-(\w+)-body"><sup>\((\w+)\)<\/sup><span>(.*?)<\/span><\/aside>/g,
    (match, footnoteId, _, content) => {
      footnoteContents[footnoteId] = content;
      return '';
    }
  );

  html = html.replace(
    /<span class="footnote-link" id="footnote-(\w+)"><sup>\((\w+)\)<\/sup><\/span>/g,
    (match, footnoteId, displayId) => {
      const content = footnoteContents[footnoteId] || '';
      return `
        <span class="footnote-container">
          <sup>(${displayId})</sup>
          <span class="footnote-content" data-footnote="${footnoteId}">
            <sup>(${displayId})</sup>
            <span>${content}</span>
          </span>
        </span>`;
    }
  );

  return html;
};

export { getPosts, getPost, getNotes, getNote, processHTML };