HokmPlay/server/src/Hokm.Engine/Deck.cs

namespace Hokm.Engine;

public static class Deck
{
    public static readonly Suit[] Suits = { Suit.Spades, Suit.Hearts, Suit.Diamonds, Suit.Clubs };

    public static List<Card> Create()
    {
        var deck = new List<Card>(52);
        foreach (var suit in Suits)
            for (int rank = 2; rank <= 14; rank++)
                deck.Add(new Card(suit, rank));
        return deck;
    }

    /// <summary>Fisher–Yates shuffle into a new list.</summary>
    public static List<Card> Shuffle(IReadOnlyList<Card> input, Random rng)
    {
        var arr = input.ToList();
        for (int i = arr.Count - 1; i > 0; i--)
        {
            int j = rng.Next(i + 1);
            (arr[i], arr[j]) = (arr[j], arr[i]);
        }
        return arr;
    }

    public static List<Card> SortHand(IEnumerable<Card> hand)
    {
        static int Order(Suit s) => s switch
        {
            Suit.Spades => 0,
            Suit.Hearts => 1,
            Suit.Clubs => 2,
            Suit.Diamonds => 3,
            _ => 4,
        };
        return hand.OrderBy(c => Order(c.Suit)).ThenByDescending(c => c.Rank).ToList();
    }
}