/// Cumulative guess / prospective-question score from the API.
class GuessScoreSummary {
  const GuessScoreSummary({
    required this.total,
    required this.answersTotal,
    required this.answersCorrect,
    required this.percentCorrect,
    this.slotStart,
    this.newerSlotStart,
  });

  final num total;
  final int answersTotal;
  final int answersCorrect;
  final num percentCorrect;

  /// Older edge of the active session-half pair in the history window.
  final DateTime? slotStart;

  /// Newer edge of the active pair (next session half after [slotStart]).
  final DateTime? newerSlotStart;

  static const GuessScoreSummary empty = GuessScoreSummary(
    total: 0,
    answersTotal: 0,
    answersCorrect: 0,
    percentCorrect: 0,
  );

  factory GuessScoreSummary.fromJson(Map<String, dynamic> json) {
    final int answersTotal = (json['answersTotal'] as num?)?.toInt() ?? 0;
    final int answersCorrect = (json['answersCorrect'] as num?)?.toInt() ?? 0;
    final num? percentRaw = json['percentCorrect'] as num?;
    final num percentCorrect = percentRaw ??
        (answersTotal > 0 ? (answersCorrect / answersTotal) * 100 : 0);
    return GuessScoreSummary(
      total: json['total'] as num? ?? 0,
      answersTotal: answersTotal,
      answersCorrect: answersCorrect,
      percentCorrect: percentCorrect,
      slotStart: _parseOptionalUtc(json['slotStart'] as String?),
      newerSlotStart: _parseOptionalUtc(json['newerSlotStart'] as String?),
    );
  }

  static DateTime? _parseOptionalUtc(String? wire) {
    if (wire == null || wire.isEmpty) {
      return null;
    }
    return DateTime.tryParse(wire)?.toUtc();
  }
}