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

namespace RuleEngine.Core;

/// <summary>
/// Per-game wildcard configuration — replaces the old static HashSet approach.
/// Each MahjongGameState owns its own registry so different game variants
/// don't leak wildcard state between tests or concurrent games.
/// </summary>
public class WildcardRegistry
{
    private readonly HashSet<int> _wildcards = new();
    private int _wildcardBase;

    /// <summary>Base wildcard encoding. Default 50, configurable from DSL wildcard_encoding.</summary>
    public int WildcardBase
    {
        get => _wildcardBase;
        set { _wildcardBase = value > 0 ? value : 50; }
    }

    /// <summary>The tile revealed from deck to determine random wildcards (骰子翻牌定精).</summary>
    public int? RevealedTile { get; set; }

    public WildcardRegistry() { _wildcardBase = MahjongTile.WildcardBase; }
    public WildcardRegistry(int wildcardBase) { _wildcardBase = wildcardBase > 0 ? wildcardBase : MahjongTile.WildcardBase; }

    /// <summary>Non-extra wildcard tiles — normal tiles (e.g. 红中=35) that ALSO act as wildcards.</summary>
    public IReadOnlySet<int> ConfiguredWildcards => _wildcards;

    public void Clear() { _wildcards.Clear(); RevealedTile = null; }
    public void Add(int tile) => _wildcards.Add(tile);

    public void AddRange(IEnumerable<int> tiles)
    {
        foreach (var t in tiles) _wildcards.Add(t);
    }

    /// <summary>Is this tile a wildcard? Checks encoding range AND configured set.</summary>
    public bool IsWildcard(int tile) =>
        (tile >= _wildcardBase && tile <= _wildcardBase + 9) || _wildcards.Contains(tile);

    /// <summary>Count how many tiles in a list are wildcards.</summary>
    public int CountWildcards(IReadOnlyList<int> tiles) =>
        tiles.Count(t => IsWildcard(t));

    /// <summary>Parse wildcard tile names from DSL into encodings.</summary>
    public static int? NameToEncoding(string name) => name switch
    {
        "红中" => 35,
        "发财" => 36,
        "白板" => 37,
        _ => null
    };

    /// <summary>
    /// Compute wildcard tiles from a revealed tile (翻牌定精).
    /// Numbered suits: rank+1 is main 精, rank+2 is secondary 精 (wraps 9→1).
    /// Honor tiles: next in honor sequence (东→南→西→北→中→发→白→东).
    /// </summary>
    /// <param name="revealedTile">The tile flipped from the deck.</param>
    /// <param name="count">How many next tiles to treat as wildcards (default 2 = 正精+副精).</param>
    /// <returns>List of tile encodings that should become wildcards.</returns>
    public static List<int> ComputeNextTiles(int revealedTile, int count = 2)
    {
        var result = new List<int>();
        int suit = MahjongTile.Suit(revealedTile);

        if (suit == 3) // Honors: 东(31)→南(32)→西(33)→北(34)→中(35)→发(36)→白(37)→东(31)
        {
            for (int i = 1; i <= count; i++)
            {
                int next = revealedTile + i;
                if (next > 37) next = 31 + (next - 38);
                result.Add(next);
            }
        }
        else if (suit is >= 0 and <= 2) // Numbered: 万(1-9) / 条(11-19) / 筒(21-29)
        {
            int baseVal = suit switch { 0 => 0, 1 => 10, _ => 20 };
            int rank = MahjongTile.Rank(revealedTile);
            for (int i = 1; i <= count; i++)
            {
                int nextRank = (rank + i - 1) % 9 + 1;
                result.Add(baseVal + nextRank);
            }
        }
        return result;
    }

    public WildcardRegistry Clone()
    {
        var r = new WildcardRegistry(_wildcardBase);
        r.AddRange(_wildcards);
        r.RevealedTile = RevealedTile;
        return r;
    }
}