const ALLOW_MANY = ['by', 'url', 'genre', 'license'];

export function getMetadata(raw_code) {

  if (raw_code == null) {

    console.error('could not extract metadata from missing pattern code');

    raw_code = '';

  }

  const comment_regexp = /\/\*([\s\S]*?)\*\/|\/\/(.*)$/gm;

  const comments = [...raw_code.matchAll(comment_regexp)].map((c) => (c[1] || c[2] || '').trim());

  const tags = {};

  const [prefix, title] = (comments[0] || '').split('"');

  if (prefix.trim() === '' && title !== undefined) {

    tags['title'] = title;

  }

  for (const comment of comments) {

    const tag_matches = comment.split('@').slice(1);

    for (const tag_match of tag_matches) {

      let [tag, tag_value] = tag_match.split(/ (.*)/s);

      tag = tag.trim();

      tag_value = (tag_value || '').replaceAll(/ +/g, ' ').trim();

      if (ALLOW_MANY.includes(tag)) {

        const tag_list = tag_value

          .split(/[,\n]/)

          .map((t) => t.trim())

          .filter((t) => t !== '');

        tags[tag] = tag in tags ? tags[tag].concat(tag_list) : tag_list;

      } else {

        tag_value = tag_value.replaceAll(/\s+/g, ' ');

        tags[tag] = tag in tags ? tags[tag] + ' ' + tag_value : tag_value;

      }

    }

  }

  return tags;

}