import type { HighlightLanguage } from './languages';
import * as languages from './languages';

type LanguagesMap = Record<string, HighlightLanguage>;

/**
 * A key-value map to get language info from alias.
 *
 * - key: alias
 * - value: language
 */
let languagesMap: LanguagesMap;

/**
 * Lazy generate languages map.
 */
const getLanguagesMap = (): LanguagesMap => {
  if (!languagesMap) {
    languagesMap = Object.values(languages).reduce((result, item) => {
      item.aliases.forEach((alias) => {
        result[alias] = item;
      });
      return result;
    }, {});
  }

  return languagesMap;
};

/**
 * Resolve language for highlight from token info.
 */
export const resolveLanguage = (info: string): HighlightLanguage => {
  // Get user-defined language alias.
  const alias = info.match(/^([a-zA-Z]+)/)?.[1] || 'text';

  // If the alias does not have a match in the map fallback to the alias itself.
  return (
    getLanguagesMap()[alias] ?? {
      name: alias,
      ext: alias,
      aliases: [alias],
    }
  );
};