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

namespace RuleEngine.Core;

/// Mahjong tile int encoding + static utilities
public static class MahjongTile
{
    // Encoding: 万1-9=1-9, 条1-9=11-19, 筒1-9=21-29
    // 字: 东=31,南=32,西=33,北=34,中=35,发=36,白=37
    // 花: 春=41..菊=48
    // 宝牌: 50-59 (extra wildcards added to deck)

    public const int WildcardBase = 50;

    /// <summary>Check if tile is in the encoding-50+ wildcard range only (no configured set).</summary>
    public static bool IsWildcard(int tile) => tile >= WildcardBase && tile <= WildcardBase + 9;

    /// <summary>Check if tile is a wildcard including game-specific configured set.</summary>
    public static bool IsWildcard(int tile, WildcardRegistry wildcards) =>
        tile >= WildcardBase && tile <= WildcardBase + 9 || wildcards.IsWildcard(tile);

    public static int Encode(string suit, int rank)
    {
        return suit switch
        {
            "万" => rank,
            "条" => 10 + rank,
            "筒" => 20 + rank,
            _ => throw new ArgumentException($"Unknown suit: {suit}")
        };
    }

    /// <summary>ToString with optional wildcard display context.</summary>
    public static string ToString(int tile) => ToStringCore(tile);

    /// <summary>ToString with game-specific wildcard registry for 🀫 display.</summary>
    public static string ToString(int tile, WildcardRegistry wildcards) =>
        wildcards.IsWildcard(tile) ? $"🀫{TileName(tile)}" : ToStringCore(tile);

    private static string ToStringCore(int tile)
    {
        if (tile >= 1 && tile <= 9) return $"{tile}万";
        if (tile >= 11 && tile <= 19) return $"{tile - 10}条";
        if (tile >= 21 && tile <= 29) return $"{tile - 20}筒";
        return tile switch
        {
            31 => "东", 32 => "南", 33 => "西", 34 => "北",
            35 => "中", 36 => "发", 37 => "白",
            41 => "春", 42 => "夏", 43 => "秋", 44 => "冬",
            45 => "梅", 46 => "兰", 47 => "竹", 48 => "菊",
            >= 50 and <= 59 => "🃏",
            _ => $"?{tile}"
        };
    }

    private static string TileName(int tile) => tile switch
    {
        31 => "东", 32 => "南", 33 => "西", 34 => "北",
        35 => "中", 36 => "发", 37 => "白",
        _ => $"?{tile}"
    };

    /// 0=万, 1=条, 2=筒, 3=字, 4=花, 5=宝牌
    public static int Suit(int tile)
    {
        if (tile >= 1 && tile <= 9) return 0;
        if (tile >= 11 && tile <= 19) return 1;
        if (tile >= 21 && tile <= 29) return 2;
        if (tile >= 31 && tile <= 37) return 3;
        if (tile >= 41 && tile <= 48) return 4;
        if (tile >= 50 && tile <= 59) return 5;
        return -1;
    }

    public static int Rank(int tile)
    {
        if (tile >= 1 && tile <= 9) return tile;
        if (tile >= 11 && tile <= 19) return tile - 10;
        if (tile >= 21 && tile <= 29) return tile - 20;
        if (tile >= 31 && tile <= 37) return tile;
        if (tile >= 41 && tile <= 48) return tile;
        return tile;
    }

    public static string SuitName(int suit) => suit switch
    {
        0 => "万", 1 => "条", 2 => "筒", 3 => "字", 4 => "花", 5 => "宝牌", _ => "?"
    };

    public static bool IsHonor(int tile) => tile >= 31 && tile <= 37;
    public static bool IsFlower(int tile) => tile >= 41 && tile <= 48;
    public static bool IsNumbered(int tile) => tile >= 1 && tile <= 29;
    public static bool IsTerminal(int tile)
    {
        if (IsHonor(tile)) return true;
        if (IsNumbered(tile))
        {
            int r = Rank(tile);
            return r == 1 || r == 9;
        }
        return false;
    }

    public static bool SameSuit(int a, int b) => Suit(a) == Suit(b);

    public static int[] AllTiles(bool includeHonors = false, bool includeFlowers = false, int wildcardCount = 0,
        int wildcardBase = 50)
    {
        int count = 27 + (includeHonors ? 7 : 0) + (includeFlowers ? 8 : 0) + wildcardCount;
        var tiles = new int[count];
        int idx = 0;
        for (int i = 1; i <= 9; i++) tiles[idx++] = i;
        for (int i = 1; i <= 9; i++) tiles[idx++] = 10 + i;
        for (int i = 1; i <= 9; i++) tiles[idx++] = 20 + i;
        if (includeHonors)
        {
            for (int i = 31; i <= 37; i++) tiles[idx++] = i;
        }
        if (includeFlowers)
        {
            for (int i = 41; i <= 48; i++) tiles[idx++] = i;
        }
        for (int i = 0; i < wildcardCount; i++)
            tiles[idx++] = wildcardBase + i;
        return tiles;
    }
}