import 'dart:math';

/// Tunables for spelling familiarity scoring and weighted selection.
abstract final class SpellingProgressPolicy {
  /// Added to [familiarity_score] when the user answers the quiz correctly.
  static const int correctDelta = 1;

  /// Subtracted from [familiarity_score] when the user answers incorrectly.
  static const int incorrectDelta = 1;

  /// Base weight before familiarity adjustment.
  static const double baseWeight = 1.0;

  /// Weight reduction per point of positive familiarity (mastered words).
  static const double penaltyPerPoint = 0.15;

  /// Minimum selection weight — never zero chance.
  static const double minWeight = 0.05;

  /// Selection weight for a catalog item given the user's familiarity score.
  static double weightForScore(int familiarityScore) {
    return max(
      minWeight,
      baseWeight - familiarityScore * penaltyPerPoint,
    );
  }

  /// Applies a graded quiz outcome to the stored familiarity score.
  static int scoreAfterAttempt({
    required int currentScore,
    required bool correct,
  }) {
    if (correct) {
      return currentScore + correctDelta;
    }
    return currentScore - incorrectDelta;
  }
}