class Nutrient {
  final String name;
  final String unit;
  final String rdaType;
  final String? note;
  final UpperLimit? ul; // nutrient-level UL (optional)
  final List<LifeStage> lifeStages;

  Nutrient({
    required this.name,
    required this.unit,
    required this.rdaType,
    this.note,
    this.ul,
    required this.lifeStages,
  });

  factory Nutrient.fromJson(String name, Map<String, dynamic> json) {
    return Nutrient(
      name: name,
      unit: json['unit'],
      rdaType: json['rda_type'],
      note: json['note'],
      ul: (json['ul'] is Map<String, dynamic>) ? UpperLimit.fromJson(json['ul'] as Map<String, dynamic>) : null,
      lifeStages: (json['life_stages'] as List)
          .map((stage) => LifeStage.fromJson(stage))
          .toList(),
    );
  }
}

class LifeStage {
  final String ageRange;
  final String sex;
  final double value;
  final double? valueMin;
  final double? valueMax;
  final double? ul;
  final String? description;

  LifeStage({
    required this.ageRange,
    required this.sex,
    required this.value,
    this.valueMin,
    this.valueMax,
    this.ul,
    this.description,
  });

  factory LifeStage.fromJson(Map<String, dynamic> json) {
    return LifeStage(
      ageRange: json['age_range'],
      sex: json['sex'],
      value: (json['value'] as num?)?.toDouble() ?? 0.0,
      valueMin: json['value_min'] != null ? (json['value_min'] as num).toDouble() : null,
      valueMax: json['value_max'] != null ? (json['value_max'] as num).toDouble() : null,
      ul: json['ul'] != null ? (json['ul'] as num).toDouble() : null,
      description: json['description'],
    );
  }
}

class UpperLimit {
  final double value;
  final String unit;
  final String? duration;
  final String? note;

  const UpperLimit({
    required this.value,
    required this.unit,
    this.duration,
    this.note,
  });

  factory UpperLimit.fromJson(Map<String, dynamic> json) {
    return UpperLimit(
      value: (json['value'] as num).toDouble(),
      unit: json['unit'] ?? '',
      duration: json['duration'],
      note: json['note'],
    );
  }
}