const NAMED: Record<string, string> = {
  amp: '&',
  lt: '<',
  gt: '>',
  quot: '"',
  apos: "'",
  nbsp: ' ',
  hellip: '…',
  mdash: '—',
  ndash: '–',
  lsquo: '‘',
  rsquo: '’',
  ldquo: '“',
  rdquo: '”',
  trade: '™',
  copy: '©',
  reg: '®',
};

/**
 * Decode HTML character references left in plain text. Link previews need it:
 * some sites double-encode their meta tags (Steam: `&amp;quot;`), so after
 * Synapse decodes once the card showed a literal `&quot;`. The result is only
 * ever rendered as React text, so decoding can't inject markup.
 */
export const decodeHtmlEntities = (text: string): string => {
  if (!text.includes('&')) return text;
  return text.replace(/&(#x[0-9a-f]+|#[0-9]+|[a-z]+);/gi, (match, ref: string) => {
    if (ref[0] === '#') {
      const code =
        ref[1] === 'x' || ref[1] === 'X' ? parseInt(ref.slice(2), 16) : parseInt(ref.slice(1), 10);
      return Number.isFinite(code) && code > 0 && code <= 0x10ffff
        ? String.fromCodePoint(code)
        : match;
    }
    return NAMED[ref.toLowerCase()] ?? match;
  });
};