/// Utility functions for gold/silver purity factor calculation and formatting.
/// Standard rule: Purity is represented as a fraction between 0.0 and 1.0 (e.g. 0.916 for 22KT / 91.6%).
/// If a raw value > 1.0 is supplied (such as 91.6 or 75.0), it is normalized by dividing by 100 with a maximum of 1.0.

double normalizePurity(num? rawPurity) {
  if (rawPurity == null || rawPurity <= 0) return 1.0;
  double p = rawPurity.toDouble();
  if (p > 1.0) {
    p = p / 100.0;
  }
  if (p > 1.0) {
    p = 1.0;
  }
  return p;
}

String formatPurity(num? rawPurity) {
  final p = normalizePurity(rawPurity);
  return p.toStringAsFixed(3);
}

/// Resolves purity factor prioritizing the category (metal grade e.g. 22KT -> 0.916)
/// then falling back to product-specific purity or 1.0.
double resolvePurity({num? categoryPurity, num? productPurity}) {
  if (categoryPurity != null && categoryPurity > 0) {
    return normalizePurity(categoryPurity);
  }
  if (productPurity != null && productPurity > 0) {
    return normalizePurity(productPurity);
  }
  return 1.0;
}