import { join } from 'path';
import fs from 'fs/promises';
import yaml from 'yaml';
import { marked } from 'marked';
import hljs from 'highlight.js';
import { getDateObject } from '../utils/date-object';
import { BlogPost, BlogPostTag } from '../types/post';

const dir = join('content', 'blog');

marked.use({
  renderer: {
    code: (code, info, escaped): string => {
      const language = hljs.getLanguage(info) ? info : 'plaintext';
      const created = hljs.highlight(code, { language }).value;
      return `<div class="codeblock"><pre><code class="hljs language-${language}">${created}</code></pre></div>`;
    },
    link: (href: string, title: string, text: string): string => {
      return `<a href="${href}" rel="nofollow" target="_blank"${
        title ? ` title="${title}"` : ''
      }>${text}</a>`;
    },
  },
});

export async function readBlogPosts(
  condition?: (body: BlogPost) => boolean,
  render = true,
  includeContent = true
) {
  const files = await fs.readdir(dir);
  const readMD = files.filter((file) => file.endsWith('.md'));
  const readFiles = [];
  for (const file of readMD) {
    const post = await readBlogPost(
      file.replace('.md', ''),
      condition,
      render,
      includeContent
    );
    if (!post) continue;
    readFiles.push(post);
  }
  readFiles.sort((a, b) =>
    new Date(b.date)
      .toISOString()
      .localeCompare(new Date(a.date).toISOString(), 'en', { numeric: true })
  );
  return readFiles;
}

export async function readBlogPost(
  slug: string,
  condition?: (body: BlogPost) => boolean,
  render = true,
  includeContent = true
): Promise<BlogPost[]> {
  const decoded = decodeURIComponent(slug);
  if (!slug || decoded.includes('/') || decoded.includes('.'))
    throw new Error('Invalid post slug');

  const file = `${slug}.md`;
  const mdpath = join(dir, file);
  const read = await fs.readFile(mdpath, { encoding: 'utf-8' });

  const { header: parsedHeader, length: headerLength } = await readHeader(read);
  const renderedMd = render
    ? await marked(read.substring(headerLength), { async: true })
    : undefined;
  const { year, month, day } = getDateObject(parsedHeader);
  const content = {
    ...parsedHeader,
    file,
    slug,
    fullSlug: `${year}/${month}/${day}/${slug}`,
    markdown: includeContent ? read.substring(headerLength) : undefined,
    html: renderedMd,
  };

  if (condition) {
    if (!condition(content)) {
      return;
    }
  }

  return content;
}

export async function getTags(): Promise<BlogPostTag[]> {
  const posts = await readBlogPosts(undefined, false, false);
  const obj: BlogPostTag[] = [];

  for (const post of posts) {
    for (const tag of post.tags || []) {
      const find = obj.find((item) => item.name === tag);
      if (find) {
        find.count++;
        find.posts.push(post.slug);
        continue;
      }

      obj.push({
        name: tag,
        count: 1,
        posts: [post.slug],
      });
    }
  }

  obj.sort((a, b) => a.name.localeCompare(b.name, 'en'));

  return obj;
}

export async function getArchiveTree(condition?: (body: BlogPost) => boolean) {
  const posts = await readBlogPosts(condition, false, false);
  const obj = {};

  for (const post of posts) {
    const { year, month, day } = getDateObject(post);

    if (!obj[year]) {
      obj[year] = {};
    }

    if (!obj[year][month]) {
      obj[year][month] = {};
    }

    if (!obj[year][month][day]) {
      obj[year][month][day] = [];
    }

    obj[year][month][day].push(post.slug);
  }

  return obj;
}

export async function generatePaths(prefix = '/') {
  const tree = await getArchiveTree();
  const paths = [];

  for (const year of Object.keys(tree)) {
    paths.push(`${prefix}archive/${year}`);
    for (const month of Object.keys(tree[year])) {
      paths.push(`${prefix}archive/${year}/${month}`);
      for (const day of Object.keys(tree[year][month])) {
        paths.push(`${prefix}archive/${year}/${month}/${day}`);
      }
    }
  }

  paths.sort((a, b) => b.localeCompare(a, 'en', { numeric: true }));

  return paths;
}

async function readHeader(fileContents: string) {
  const splitter = fileContents.split('\n');
  let header = '';

  for (const line of splitter) {
    if (line === '---') {
      if (!header.length) continue;
      break;
    }
    header += line + '\n';
  }

  return {
    header: yaml.parse(header),
    length: header.length + 9,
  };
}