export function esc(str) {
  if (!str) return '';
  return String(str).replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
}

export function sanitizeHtml(html) {
  // DOMPurify is loaded globally from index.html. If it is unavailable, render
  // as plain text rather than attempting partial sanitization.
  if (!window.DOMPurify || typeof window.DOMPurify.sanitize !== 'function') {
    console.warn('[learningHub] DOMPurify unavailable - rendering as plain text.');
    var d = document.createElement('div');
    d.textContent = String(html == null ? '' : html);
    return d.innerHTML;
  }
  return window.DOMPurify.sanitize(html, {
    ALLOWED_TAGS: ['p','br','b','strong','i','em','u','s','h1','h2','h3','h4','h5','h6',
      'ul','ol','li','a','blockquote','code','pre','table','thead','tbody','tr','th','td',
      'hr','div','span','sub','sup','dl','dt','dd'],
    ALLOWED_ATTR: ['href','colspan','rowspan','class','target','rel'],
    ADD_ATTR: ['target'],
    FORBID_ATTR: ['style','onerror','onload','onclick','onmouseover'],
    ALLOW_DATA_ATTR: false
  });
}