card-game-engine/RuleEngine/Phase/PhaseMachine.cs

namespace RuleEngine.Phase;

using RuleEngine.Core;
using RuleEngine.Patterns;

public class PhaseConfig
{
    public string Name { get; set; } = "";
    public string Type { get; set; } = "";  // "auto", "mahjong_turn"
    public string Action { get; set; } = "";
    public string? Next { get; set; }
    public string TurnOrder { get; set; } = "counter_clockwise";
    public string? FirstPlayer { get; set; }
    public List<ActionOption> SelfActions { get; set; } = new();
    public List<ActionOption> OthersReactions { get; set; } = new();
    public string PriorityPolicy { get; set; } = "highest_wins";
    public string? OnWin { get; set; }
    public List<EndCondition> EndConditions { get; set; } = new();
    public bool ParallelElimination { get; set; }
    public string? OnEliminate { get; set; }
    public int MaxFan { get; set; } = int.MaxValue;
}

public class ActionOption
{
    public string Action { get; set; } = "";
    public int Priority { get; set; }
    public string? Condition { get; set; }
}

public class EndCondition
{
    public string Type { get; set; } = "";
    public string Action { get; set; } = "";
}

public class MahjongPhaseMachine
{
    private readonly List<PhaseConfig> _phases;
    private readonly MeldsSolver _solver;

    public MahjongPhaseMachine(List<PhaseConfig> phases, MeldsSolver solver)
    {
        _phases = phases;
        _solver = solver;
    }

    public PhaseConfig? GetPhase(string name) => _phases.FirstOrDefault(p => p.Name == name);

    public List<ActionOption> GetLegalActions(MahjongGameState state, string playerId, bool requireWinFan = false)
    {
        var actions = new List<ActionOption>();

        // Always can discard
        foreach (var t in state.Hands[playerId].Distinct())
            actions.Add(new ActionOption { Action = "discard", Priority = 0 });

        // Check pung/kong/win for last discard
        if (state.LastDiscard.HasValue && state.LastDiscardPlayer != playerId)
        {
            if (CanPung(state, playerId, state.LastDiscard.Value))
                actions.Add(new ActionOption { Action = "pung", Priority = 2 });

            if (CanMingKong(state, playerId, state.LastDiscard.Value))
                actions.Add(new ActionOption { Action = "ming_kong", Priority = 3 });

            var handWithTile = new List<int>(state.Hands[playerId]) { state.LastDiscard.Value };
            var result = _solver.CheckWin(handWithTile);
            if (result != null && result.IsWin)
            {
                if (!requireWinFan || result.Fans.Sum(f => GetFanValue(f)) >= 8)
                    actions.Add(new ActionOption { Action = "win", Priority = 4 });
            }
        }

        // Self actions: an_kong, bu_kong, win (tumo)
        if (CanAnKong(state, playerId))
            actions.Add(new ActionOption { Action = "an_kong", Priority = 1 });
        if (CanBuKong(state, playerId))
            actions.Add(new ActionOption { Action = "bu_kong", Priority = 1 });

        var tumoResult = _solver.CheckWin(state.Hands[playerId]);
        if (tumoResult != null && tumoResult.IsWin)
        {
            if (!requireWinFan || tumoResult.Fans.Sum(f => GetFanValue(f)) >= 8)
                actions.Add(new ActionOption { Action = "win", Priority = 4 });
        }

        // Chi
        if (state.LastDiscard.HasValue && state.LastDiscardPlayer != playerId)
        {
            if (CanChi(state, playerId, state.LastDiscard.Value))
                actions.Add(new ActionOption { Action = "chi", Priority = 1 });
        }

        actions.Add(new ActionOption { Action = "pass", Priority = 0 });
        return actions;
    }

    private int GetFanValue(string fanName)
    {
        // Simple lookup — full implementation would read from DSL
        return fanName switch
        {
            "清一色" => 4,
            "对对胡" => 2,
            "暗七对" => 4,
            "带幺九" => 2,
            _ => 1
        };
    }

    private bool CanPung(MahjongGameState state, string playerId, int tile)
    {
        int count = state.Hands[playerId].Count(t => t == tile);
        return count >= 2;
    }

    private bool CanMingKong(MahjongGameState state, string playerId, int tile)
    {
        int count = state.Hands[playerId].Count(t => t == tile);
        return count >= 3;
    }

    private bool CanAnKong(MahjongGameState state, string playerId)
    {
        return false; // Simplified: AI decides during draw phase
    }

    private bool CanBuKong(MahjongGameState state, string playerId)
    {
        // Check if player has an exposed pung and drew the 4th tile
        if (!state.Exposed.ContainsKey(playerId)) return false;
        return state.Exposed[playerId].Any(m => m.Type == "pung" &&
            state.Hands[playerId].Contains(m.Tiles[0]));
    }

    private bool CanChi(MahjongGameState state, string playerId, int tile)
    {
        if (MahjongTile.IsHonor(tile)) return false;
        int suit = MahjongTile.Suit(tile);
        int rank = MahjongTile.Rank(tile);
        var hand = state.Hands[playerId];

        // Check two sequential combinations
        bool hasLower = rank >= 3
            && hand.Count(t => MahjongTile.Suit(t) == suit && MahjongTile.Rank(t) == rank - 2) > 0
            && hand.Count(t => MahjongTile.Suit(t) == suit && MahjongTile.Rank(t) == rank - 1) > 0;
        bool hasMiddle = rank >= 2 && rank <= 8
            && hand.Count(t => MahjongTile.Suit(t) == suit && MahjongTile.Rank(t) == rank - 1) > 0
            && hand.Count(t => MahjongTile.Suit(t) == suit && MahjongTile.Rank(t) == rank + 1) > 0;
        bool hasUpper = rank <= 7
            && hand.Count(t => MahjongTile.Suit(t) == suit && MahjongTile.Rank(t) == rank + 1) > 0
            && hand.Count(t => MahjongTile.Suit(t) == suit && MahjongTile.Rank(t) == rank + 2) > 0;

        return hasLower || hasMiddle || hasUpper;
    }

    public string GetNextPlayer(MahjongGameState state, string currentPlayer)
    {
        var alive = state.AlivePlayers;
        int idx = alive.IndexOf(currentPlayer);
        if (idx < 0) return alive[0];
        int next = (idx + 1) % alive.Count;
        return alive[next];
    }
}