wiki.ts

import debounce from 'common/debounce';

export type WikiTheory = (nodes: Tree.Node[]) => void;

export default function wikiTheory(): WikiTheory {
  const cache = new Map<string, string>();
  const show = (html: string) => {
    $('.analyse__wiki').html(html).toggleClass('empty', !html);
    lichess.pubsub.emit('chat.resize');
  };

  const plyPrefix = (node: Tree.Node) => `${Math.floor((node.ply + 1) / 2)}${node.ply % 2 === 1 ? '._' : '...'}`;

  const wikiBooksUrl = 'https://en.wikibooks.org';
  const apiArgs = 'redirects&origin=*&action=query&prop=extracts&formatversion=2&format=json&exchars=1200';

  const removeEmptyParagraph = (html: string) => html.replace(/<p>(<br \/>|\s)*<\/p>/g, '');

  const removeTableHeader = (html: string) => html.replace('<h2><span id="Theory_table">Theory table</span></h2>', '');
  const removeTableExpl = (html: string) =>
    html.replace(/For explanation of theory tables see theory table and for notation see algebraic notation.?/, '');
  const removeContributing = (html: string) =>
    html.replace('When contributing to this Wikibook, please follow the Conventions for organization.', '');

  const readMore = (title: string) =>
    `<p><a target="_blank" href="${wikiBooksUrl}/wiki/${title}">Read more on WikiBooks</a></p>`;

  const transform = (html: string, title: string) =>
    removeEmptyParagraph(removeTableHeader(removeTableExpl(removeContributing(html)))) + readMore(title);

  return debounce(
    async (nodes: Tree.Node[]) => {
      const pathParts = nodes.slice(1).map(n => `${plyPrefix(n)}${n.san}`);
      const path = pathParts.join('/').replace(/[+!#?]/g, '') ?? '';
      if (pathParts.length > 30 || !path || path.length > 255 - 21) show('');
      else if (cache.has(path)) show(cache.get(path)!);
      else if (
        Array.from({ length: pathParts.length }, (_, i) => -i - 1)
          .map(i => pathParts.slice(0, i).join('/'))
          .some(sub => cache.has(sub) && !cache.get(sub)!.length)
      )
        show('');
      else {
        const title = `Chess_Opening_Theory/${path}`;
        try {
          const res = await fetch(`${wikiBooksUrl}/w/api.php?titles=${title}&${apiArgs}`);
          const saveAndShow = (html: string) => {
            cache.set(path, html);
            show(html);
          };
          if (res.ok) {
            const json = await res.json();
            const page = json.query.pages[0];
            if (page.missing) saveAndShow('');
            else if (page.invalid) show('invalid request: ' + page.invalidreason);
            else if (!page.extract) show('error: unexpected API response:<br><pre>' + JSON.stringify(page) + '</pre>');
            else saveAndShow(transform(page.extract, title));
          } else saveAndShow('');
        } catch (err) {
          show('error: ' + err);
        }
      }
    },
    500,
    true
  );
}