// A deliberately tiny Markdown subset for the texts of reference: paragraphs,
// line breaks, lists, **bold**, *italic*, `code`. HTML is always escaped first,
// so a proposal can never inject markup.

const ESCAPES: Record<string, string> = { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' };

export function escapeHtml(s: string): string {
  return s.replace(/[&<>"']/g, (c) => ESCAPES[c] ?? c);
}

export function inline(s: string): string {
  return escapeHtml(s)
    .replace(/`([^`]+)`/g, '<code>$1</code>')
    .replace(/\*\*([^*]+)\*\*/g, '<strong>$1</strong>')
    .replace(/(^|[^*])\*([^*\s][^*]*?)\*(?!\*)/g, '$1<em>$2</em>');
}

const BULLET = /^\s*[-*]\s+/;
const NUMBERED = /^\s*\d+[.)]\s+/;

export function render(md: string): string {
  const blocks = md.replace(/\r\n?/g, '\n').trim().split(/\n\s*\n/);
  return blocks
    .map((block) => {
      const lines = block.split('\n').filter((l) => l.trim().length > 0);
      if (lines.length > 0 && lines.every((l) => BULLET.test(l))) {
        return `<ul>${lines.map((l) => `<li>${inline(l.replace(BULLET, ''))}</li>`).join('')}</ul>`;
      }
      if (lines.length > 0 && lines.every((l) => NUMBERED.test(l))) {
        return `<ol>${lines.map((l) => `<li>${inline(l.replace(NUMBERED, ''))}</li>`).join('')}</ol>`;
      }
      return `<p>${lines.map(inline).join('<br>')}</p>`;
    })
    .join('');
}

/** Plain text, for one-line excerpts. */
export function plain(md: string): string {
  return md.replace(/[*`]/g, '').replace(/^\s*[-*]\s+/gm, '').replace(/\s+/g, ' ').trim();
}