card-game-engine/RuleEngine/MahjongRoom.cs

namespace RuleEngine;

using RuleEngine.AI;
using RuleEngine.Core;
using RuleEngine.Dsl;
using RuleEngine.Patterns;
using RuleEngine.Phase;
using RuleEngine.Scoring;

public class MahjongRoom
{
    public MahjongGameState State { get; private set; } = new();
    public bool IsFinished { get; private set; }
    private readonly MahjongDslRoot _rules;
    private readonly List<RandomMahjongAI> _ais;
    private readonly MeldsSolver _solver;
    private readonly MahjongPhaseMachine _phaseMachine;
    private readonly MahjongScoreEngine _scoreEngine;
    private readonly bool _autoMode;
    private readonly Random _rng = Random.Shared;

    public MahjongRoom(MahjongDslRoot rules, string[] playerNames, bool autoMode = false)
    {
        _rules = rules;
        _autoMode = autoMode;
        _ais = playerNames.Select((n, i) => new RandomMahjongAI(n, new Random(i * 7919))).ToList();

        var fanConfig = BuildFanConfig();
        _solver = new MeldsSolver(fanConfig);

        var phases = BuildPhases();
        _phaseMachine = new MahjongPhaseMachine(phases, _solver);

        _scoreEngine = new MahjongScoreEngine(new ScoringConfig
        {
            Mode = _rules.Scoring.Mode,
            MaxCap = _rules.Scoring.MaxCap
        }, _solver);

        // Init state
        State.PlayerOrder = playerNames.ToList();
        State.AlivePlayers = playerNames.ToList();
        State.Dealer = playerNames[0];
        State.CurrentPlayer = playerNames[0];
        State.Phase = "deal";

        foreach (var p in playerNames)
        {
            State.Hands[p] = new List<int>();
            State.Exposed[p] = new List<Meld>();
            State.Scores[p] = 0;
        }
    }

    private Dictionary<string, FanConfig> BuildFanConfig()
    {
        var config = new Dictionary<string, FanConfig>();
        foreach (var f in _rules.FanTypes)
        {
            config[f.Name] = new FanConfig
            {
                Name = f.Name,
                BaseFan = f.BaseFan,
                Level = f.Level,
                Excludes = f.Excludes ?? new(),
                Conflicts = f.Conflicts ?? new(),
                Condition = f.Condition
            };
        }
        return config;
    }

    private List<PhaseConfig> BuildPhases()
    {
        return _rules.Phases.Select(p => new PhaseConfig
        {
            Name = p.Name,
            Type = p.Type,
            Action = p.Action ?? "",
            Next = p.Next,
            TurnOrder = "counter_clockwise",
            ParallelElimination = p.ParallelElimination,
            SelfActions = p.SubPhases?.SelfAction?.Options?.Select(o => new ActionOption
            {
                Action = o.Action, Priority = o.Priority, Condition = o.Condition
            }).ToList() ?? new(),
            OthersReactions = p.SubPhases?.OthersReaction?.Options?.Select(o => new ActionOption
            {
                Action = o.Action, Priority = o.Priority, Condition = o.Condition
            }).ToList() ?? new(),
            PriorityPolicy = p.SubPhases?.OthersReaction?.PriorityPolicy ?? "highest_wins",
            OnWin = p.SubPhases?.OthersReaction?.OnWin
        }).ToList();
    }

    public void Run()
    {
        Deal();
        IsFinished = false;

        while (!IsFinished)
        {
            if (State.Phase == "deal") { State.Phase = "play"; continue; }
            if (State.Phase == "settle" || IsFinished) break;

            StepTurn();
        }

        if (!IsFinished)
            Settle();
    }

    public List<GameEvent> StepTurn()
    {
        State.RecentEvents.Clear();

        // Draw card
        if (State.Deck.Count > 0)
        {
            int drawn = State.Deck[^1];
            State.Deck.RemoveAt(State.Deck.Count - 1);
            State.Hands[State.CurrentPlayer].Add(drawn);
            State.AddEvent("draw", State.CurrentPlayer, drawn,
                $"摸牌: {MahjongTile.ToString(drawn)}");

            // Check flower
            if (MahjongTile.IsFlower(drawn))
            {
                State.FlowerReplaced++;
                State.AddEvent("flower_drawn", State.CurrentPlayer, drawn,
                    $"花牌 {MahjongTile.ToString(drawn)} → 补牌");
                // Flower into flower pool and draw again
                if (!State.FlowerPool.ContainsKey(State.CurrentPlayer))
                    State.FlowerPool[State.CurrentPlayer] = new List<int>();
                State.FlowerPool[State.CurrentPlayer].Add(drawn);
                State.Hands[State.CurrentPlayer].Remove(drawn);
                if (State.Deck.Count > 0)
                {
                    int extra = State.Deck[^1];
                    State.Deck.RemoveAt(State.Deck.Count - 1);
                    State.Hands[State.CurrentPlayer].Add(extra);
                    State.AddEvent("draw", State.CurrentPlayer, extra,
                        $"补牌: {MahjongTile.ToString(extra)}");
                }
            }
        }
        else
        {
            State.IsDeckExhausted = true;
            State.AddEvent("deck_exhausted", "", null, "牌墙耗尽");

            // Blood war: check ting and hua zhu
            if (_rules.Phases.Any(p => p.ParallelElimination))
            {
                CheckHuaZhu();
                CheckTing();
            }
            Settle();
            return State.RecentEvents;
        }

        // Get legal actions for current player
        var player = State.CurrentPlayer;
        bool requireWinFan = _rules.WinMinFan > 0;
        var legalActions = _phaseMachine.GetLegalActions(State, player, requireWinFan);

        // AI decides
        var (action, tile) = _ais.First(a => a.Name == player).Decide(legalActions, State);

        if (action == "win")
        {
            var result = _solver.CheckWin(State.Hands[player]);
            State.HuPlayers.Add(player);
            State.AlivePlayers.Remove(player);
            State.AddEvent("win", player, null,
                $"自摸！番型: {string.Join(" + ", result?.Fans ?? new())}");

            if (_rules.Phases.Any(p => p.ParallelElimination))
            {
                // Blood war: continue without the winner
                if (State.AlivePlayers.Count <= 1)
                {
                    Settle();
                    return State.RecentEvents;
                }
            }
            else
            {
                _scoreEngine.Settle(State, player, result!, isSelfDraw: true);
                Settle();
                return State.RecentEvents;
            }
        }
        else if (action == "discard" && tile.HasValue)
        {
            State.Hands[player].Remove(tile.Value);
            State.LastDiscard = tile.Value;
            State.LastDiscardPlayer = player;
            State.DiscardPool.Add(tile.Value);
            State.AddEvent("discard", player, tile.Value,
                $"出牌: {MahjongTile.ToString(tile.Value)}");

            // Check others' reactions (pung/kong/win)
            bool reactionTaken = CheckReactions(tile.Value);
            if (reactionTaken)
            {
                AdvancePlayer();
                return State.RecentEvents;
            }
        }
        else if (action == "pung")
        {
            // Handle pung
            if (State.LastDiscard.HasValue)
            {
                int t = State.LastDiscard.Value;
                State.Hands[player].RemoveAll(x => x == t);
                State.Hands[player].RemoveAll(x => x == t);
                State.LastDiscard = null;
                State.Exposed[player].Add(new Meld
                {
                    Type = "pung",
                    Tiles = new List<int> { t, t, t },
                    SourcePlayer = State.LastDiscardPlayer ?? ""
                });
                State.AddEvent("pung", player, t, $"碰！{MahjongTile.ToString(t)}");
            }
        }

        AdvancePlayer();
        return State.RecentEvents;
    }

    private bool CheckReactions(int discardTile)
    {
        // Collect all claims with their priorities
        var claims = new List<(string player, int priority, string action)>();
        
        foreach (var p in State.AlivePlayers)
        {
            if (p == State.CurrentPlayer) continue;

            var handWithTile = new List<int>(State.Hands[p]) { discardTile };
            var winResult = _solver.CheckWin(handWithTile);

            if (winResult != null && winResult.IsWin)
                claims.Add((p, 4, "win"));

            int sameCount = State.Hands[p].Count(t => t == discardTile);
            if (sameCount >= 3)
                claims.Add((p, 3, "ming_kong"));
            else if (sameCount >= 2)
                claims.Add((p, 2, "pung"));
        }

        if (claims.Count == 0) return false;

        // Highest-priority claim wins
        var best = claims.OrderByDescending(c => c.priority).First();

        if (best.action == "win")
        {
            var winResult = _solver.CheckWin(
                new List<int>(State.Hands[best.player]) { discardTile });
            
            State.HuPlayers.Add(best.player);
            State.AlivePlayers.Remove(best.player);
            State.AddEvent("win", best.player, discardTile,
                $"胡！{MahjongTile.ToString(discardTile)}");

            if (!_rules.Phases.Any(ph => ph.ParallelElimination))
            {
                _scoreEngine.Settle(State, best.player, winResult!, isSelfDraw: false);
                IsFinished = true;
            }
            return true;
        }

        if (best.action == "pung" || best.action == "ming_kong")
        {
            State.Hands[best.player].RemoveAll(t => t == discardTile);
            State.Hands[best.player].RemoveAll(t => t == discardTile);
            if (best.action == "ming_kong")
                State.Hands[best.player].RemoveAll(t => t == discardTile);
            
            State.Exposed[best.player].Add(new Meld
            {
                Type = best.action,
                Tiles = new List<int> { discardTile, discardTile, discardTile,
                    discardTile },  // 4th for kong
                SourcePlayer = State.CurrentPlayer
            });
            State.CurrentPlayer = best.player;
            State.LastDiscard = null;
            State.AddEvent(best.action, best.player, discardTile, best.action == "pung" ? "碰！" : "明杠！");
            return true;
        }

        return false;
    }

    private void AdvancePlayer()
    {
        int idx = State.PlayerOrder.IndexOf(State.CurrentPlayer);
        for (int i = 0; i < State.PlayerOrder.Count; i++)
        {
            int next = (idx + 1 + i) % State.PlayerOrder.Count;
            if (State.AlivePlayers.Contains(State.PlayerOrder[next]))
            {
                State.CurrentPlayer = State.PlayerOrder[next];
                State.RoundNumber++;
                return;
            }
        }
        // No alive players
        IsFinished = true;
    }

    public void Deal()
    {
        int perPlayer = _rules.Deal.CardsPerPlayer;
        bool includeFlowers = _rules.Deck.IncludeFlowers;
        bool includeHonors = _rules.Deck.IncludeHonors;
        int wildcardCount = _rules.WildcardRules != null ? _rules.Deck.WildcardCount : 0;

        var deck = new MahjongDeck(includeHonors, includeFlowers, wildcardCount);
        deck.Shuffle(_rng);

        State.Deck = deck.Tiles;
        State.AddEvent("deal_start", "", null,
            $"发牌 — {deck.Count}张牌({(includeHonors ? "+字" : "")}{(includeFlowers ? "+花" : "")}{(wildcardCount > 0 ? "+癞子" : "")})");

        foreach (var p in State.PlayerOrder)
        {
            int count = p == State.Dealer ? perPlayer + _rules.Deal.DealerExtra : perPlayer;
            for (int i = 0; i < count; i++)
            {
                int tile = State.Deck[^1];
                State.Deck.RemoveAt(State.Deck.Count - 1);
                State.Hands[p].Add(tile);
            }
        }

        State.AddEvent("deal_done", "", null, "发牌完成");
    }

    private void CheckHuaZhu()
    {
        foreach (var p in State.AlivePlayers)
        {
            var suits = State.Hands[p]
                .Where(t => MahjongTile.IsNumbered(t))
                .Select(MahjongTile.Suit)
                .Distinct()
                .Count();
            if (suits == 3)
                State.AddEvent("hua_zhu", p, null, "花猪！三色齐全");
            else
                State.AddEvent("hua_zhu_ok", p, null, $"✓ {suits}种花色");
        }
    }

    private void CheckTing()
    {
        bool hasWildcard = _rules.WildcardRules != null;
        int wildcardCount = hasWildcard ? _rules.Deck.WildcardCount : 0;
        bool require258 = _rules.WinCondition?.PairMustBe258 ?? false;
        
        foreach (var p in State.AlivePlayers)
        {
            bool ting = false;
            var hand = State.Hands[p];
            for (int i = 0; i < hand.Count; i++)
            {
                var testHand = new List<int>(hand);
                testHand.RemoveAt(i);
                var r = _solver.CheckWin(testHand, wildcardCount: wildcardCount, require258Pair: require258);
                if (r != null && r.IsWin) { ting = true; break; }
            }
            if (ting)
                State.AddEvent("ting_checked", p, null, "✓ 听牌");
            else
            {
                State.AddEvent("ting_failed", p, null, "❌ 未听牌");
                State.AddEvent("pair_validated_258", p, null, "258将检查");
            }
        }
    }

    private void Settle()
    {
        IsFinished = true;
        State.Phase = "settle";
        State.AddEvent("settle", "", null, "结算");
    }
}