card-game-engine/RuleEngine/Core/Deck.cs

namespace RuleEngine.Core;

public class MahjongDeck
{
    public List<int> Tiles { get; private set; } = new();

    public MahjongDeck(bool includeHonors = false, bool includeFlowers = false, int wildcardCount = 0, int? expectedTotal = null)
    {
        var allTiles = MahjongTile.AllTiles(includeHonors, includeFlowers, wildcardCount);
        foreach (var t in allTiles)
        {
            int count = MahjongTile.IsFlower(t) ? 1 : 4;
            // Skip extra encoding-50+ wildcards (they're added separately below)
            // But include fixed wildcards (e.g. 红中) as normal tiles
            if (t >= MahjongTile.WildcardBase) continue;
            for (int i = 0; i < count; i++)
                Tiles.Add(t);
        }
        // Add extra wildcard tiles
        for (int i = 0; i < wildcardCount; i++)
            Tiles.Add(MahjongTile.WildcardBase + i);

        // Validate against DSL total if specified
        if (expectedTotal.HasValue && Tiles.Count != expectedTotal.Value)
        {
            throw new InvalidOperationException(
                $"牌库大小不匹配: 引擎生成 {Tiles.Count} 张, DSL 声明 {expectedTotal.Value} 张。" +
                $" includeHonors={includeHonors} includeFlowers={includeFlowers} wildcardCount={wildcardCount}." +
                $" 请检查 DSL deck.total 字段与 include_honors/include_flowers 的一致性。");
        }
    }

    public void Shuffle(Random? rng = null)
    {
        rng ??= Random.Shared;
        int n = Tiles.Count;
        while (n > 1)
        {
            int k = rng.Next(n--);
            (Tiles[n], Tiles[k]) = (Tiles[k], Tiles[n]);
        }
    }

    public int Draw()
    {
        if (Tiles.Count == 0)
            throw new InvalidOperationException("Deck is empty");
        int last = Tiles[^1];
        Tiles.RemoveAt(Tiles.Count - 1);
        return last;
    }

    public int Count => Tiles.Count;
}