export function esc(s) {
  return (s == null ? '' : String(s))
    .replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;').replace(/'/g, '&#39;');
}

export function stripTags(html) {
  if (!html) return '';
  var d = document.createElement('div');
  d.innerHTML = html;
  return (d.textContent || d.innerText || '').replace(/\s+/g, ' ').trim();
}

export function formatWhen(iso) {
  if (!iso) return '';
  var d = new Date(iso);
  if (isNaN(d.getTime())) return '';
  var now = new Date();
  var sameDay = d.toDateString() === now.toDateString();
  if (sameDay) return d.toLocaleTimeString(undefined, { hour: 'numeric', minute: '2-digit' });
  return d.toLocaleDateString(undefined, { month: 'short', day: 'numeric', year: d.getFullYear() === now.getFullYear() ? undefined : 'numeric' });
}

// Sanitize via DOMPurify (loaded from cdnjs in index.html, also used by
// learningHub.js). If DOMPurify fails to load, render as plain text.
export function sanitizeHtml(html) {
  if (!window.DOMPurify || typeof window.DOMPurify.sanitize !== 'function') {
    console.warn('[notes] 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','strong','em','b','i','u','s','h2','h3','h4',
      'ul','ol','li','a','blockquote','code','pre','hr'],
    ALLOWED_ATTR: ['href','target','rel'],
    ADD_ATTR: ['target'],
    FORBID_ATTR: ['style','onerror','onload','onclick','onmouseover'],
    ALLOW_DATA_ATTR: false
  });
}