namespace QuestionsApi.Services;

public static class DynamicReviewPolicy
{
    private static readonly int[] IntervalsDays = [1, 3, 7, 21, 45];

    public static DateTime FirstDue(DateTime nowUtc) => nowUtc.AddDays(IntervalsDays[0]);

    public static (int Stage, DateTime? DueUtc, bool Mastered) AfterReview(
        int currentStage,
        bool isCorrect,
        DateTime nowUtc)
    {
        if (!isCorrect)
            return (0, FirstDue(nowUtc), false);

        var nextStage = Math.Clamp(currentStage + 1, 1, IntervalsDays.Length);
        if (nextStage >= IntervalsDays.Length)
            return (nextStage, null, true);
        return (nextStage, nowUtc.AddDays(IntervalsDays[nextStage]), false);
    }
}