/// Shared English-singularization used to fold plural ingredient and unit
/// strings onto one canonical token (`eggs` → `egg`, `lbs` → `lb`,
/// `chicken breasts` → `chicken breast`).
///
/// Rules are intentionally conservative and applied identically to both sides
/// of a comparison (recipe line vs. pantry row), so even imperfect results
/// still match as long as they are consistent.
String singularizeWord(String word) {
  if (word.length <= 2) return word;
  // berries → berry.
  if (word.endsWith('ies') && word.length > 4) {
    return '${word.substring(0, word.length - 3)}y';
  }
  // class / glass — never strip a double s.
  if (word.endsWith('ss')) return word;
  // bunches → bunch, boxes → box, buses → bus, tomatoes → tomato.
  if (word.endsWith('ches') ||
      word.endsWith('shes') ||
      word.endsWith('xes') ||
      word.endsWith('zes') ||
      word.endsWith('ses') ||
      word.endsWith('oes')) {
    return word.substring(0, word.length - 2);
  }
  // status / asparagus keep their s.
  if (word.endsWith('us') || word.endsWith('is')) return word;
  // eggs → egg.
  if (word.endsWith('s')) return word.substring(0, word.length - 1);
  return word;
}

/// Canonical, lowercase ingredient key used for fuzzy pantry ↔ recipe
/// matching (e.g. `Chicken Breast (boneless)` → `chicken breast`).
///
/// The pipeline: trim/lowercase → drop parenthetical qualifiers → collapse
/// punctuation to spaces → singularize each token.
String canonicalIngredientName(String raw) {
  var text = raw.trim().toLowerCase();
  if (text.isEmpty) return '';
  // Drop parenthetical qualifiers: "chicken breast (boneless)" → "chicken breast".
  text = text.replaceAll(RegExp(r'\([^)]*\)'), ' ');
  // Collapse punctuation so "chicken-breast" and "chicken, breast" still
  // match the plain "chicken breast" pantry key.
  text = text.replaceAll(RegExp(r'[^a-z0-9]+'), ' ');
  text = text.replaceAll(RegExp(r'\s+'), ' ').trim();
  if (text.isEmpty) return '';
  return text.split(' ').map(singularizeWord).join(' ');
}