pflib-net/pflib-net/dice/Dice.cs

namespace pflib_net.dice;

public class Dice
{
    private int _keepHighest;
    private int _keepLowest;
    private int Count { get; set; }
    private int Size { get; set; }

    private int KeepHighest
    {
        get => _keepHighest;
        set
        {
            if (value > 0 && KeepLowest > 0)
            {
                throw new InvalidOperationException("Cannot set keepHighest and keepLowest at the same time");
            }
            _keepHighest = value;
        }
    }

    private int KeepLowest
    {
        get => _keepLowest;
        set
        {
            if (value > 0 && KeepHighest > 0)
            {
                throw new InvalidOperationException("Cannot set keepHighest and keepLowest at the same time");
            }

            _keepLowest = value;
        }
    }
    private int Add { get; set; }
    private static readonly Random Random = new();

    public Dice(int size, int count = 1, int keepHighest = 0, int keepLowest = 0, int add = 0)
    {
        Count = count;
        Size = size;
        KeepHighest = keepHighest;
        KeepLowest = keepLowest;
        Add = add;
    }

    public Dice Kh(int keepHighest)
    {
        KeepHighest = keepHighest;
        return this;
    }

    public Dice Kl(int keepLowest)
    {
        KeepLowest = keepLowest;
        return this;
    }

    public int Roll()
    {
        var rolls = new List<int>();
        for (var i = 0; i < Count; i++)
        {
            rolls.Add(Random.Next(Size) + 1);
        }
        rolls.Sort();

        if (KeepHighest > 0)
        {
            var repeats = Count - KeepHighest;
            for (var i = 0; i < repeats; i++)
            {
                rolls.Remove(rolls.Max());
            }
        }

        if (KeepLowest > 0)
        {
            var repeats = Count - KeepLowest;
            
            for (var i = 0; i < repeats; i++)
            {
                rolls.Remove(rolls.Min());
            }
        }
        return rolls.Sum() + Add;
    }
}

public static class IntExtension
{
    public static Dice D(this int count, int size)
    {
        return new Dice(size, count);
    }
}