import Dot from 'dot';
import { cp, mkdir, readdir, readFile, writeFile } from 'fs/promises';
import { debuglog } from 'util';
import { join } from 'path';
import { rmIfExists } from '../utils.js';

const internals = {
  kIndexName: 'index.gmi',
  kGeminiRe: /\.gmi$/i,

  debuglog: debuglog('blog'),

  buildUrl(id, slug) {

    return `./${id}/${slug}`;
  },

  buildTitle(id, slug) {

    const date = new Date(Number(id));
    const shortDate = date.toISOString().split('T')[0];
    const title = slug.split('-').join(' ');
    return `${shortDate} ${title}`;
  },

  buildLink(id, slug) {

    return `=> ${internals.buildUrl(id,slug)} ${internals.buildTitle(id,slug)}`;
  }
};

export default async function (templateDirectory, source, target) {

  internals.debuglog(`Reading archive ${source}`);
  const postIds = (await readdir(source))
    .sort((a, b) => Number(b) - Number(a));
  const posts = [];
  for (const id of postIds) {
    const postDirectory = join(source, id);
    const slug = (await readdir(postDirectory))
      .filter((entry) => internals.kGeminiRe.test(entry))[0];

    posts.push({ id, slug });
  }

  internals.debuglog(`Read ${posts.length} posts`);

  internals.debuglog('Generating Archive Index');
  const indexLocation = join(templateDirectory, internals.kIndexName);

  internals.debuglog(`Reading ${indexLocation}`);
  const indexTemplate = await readFile(indexLocation, { encoding: 'utf8' });

  internals.debuglog('Writing Archive Index');
  const index = Dot.template(indexTemplate, {
    ...Dot.templateSettings,
    strip: false
  })({
    posts: posts.map((post) => internals.buildLink(post.id, post.slug)).join('\n')
  });

  try {
    internals.debuglog('Removing index');
    await rmIfExists(target);
  }
  finally {
    internals.debuglog('Creating index');
    await mkdir(target);
    const indexFile = join(target, internals.kIndexName);
    await writeFile(indexFile, index);

    internals.debuglog('Copying posts to archive');
    await cp(source, target, { recursive: true });
  }
}