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 HumanMahjongPlayer? _human;
    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,
        string? humanPlayer = null)
    {
        _rules = rules;
        _autoMode = autoMode;
        _ais = playerNames.Select((n, i) => new RandomMahjongAI(n, new Random(i * 7919))).ToList();
        if (humanPlayer != null)
            _human = new HumanMahjongPlayer(humanPlayer);

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

        var phases = BuildPhases();
        var (wc, r258) = GetWinParams();
        _phaseMachine = new MahjongPhaseMachine(phases, _solver, wildcardCount: wc, require258: r258);

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

        // 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();
        var player = State.CurrentPlayer;

        // Phase 1: Check reactions to last discard BEFORE drawing
        if (State.LastDiscard.HasValue && State.LastDiscardPlayer != null)
        {
            bool reacted = HandleDiscardReactions(State.LastDiscard.Value);
            if (reacted)
            {
                AdvancePlayer();
                return State.RecentEvents;
            }
            State.LastDiscard = null;
            State.LastDiscardPlayer = null;
        }

        // Phase 2: Draw card (skip for dealer on first turn — they already have 14)
        bool isDealerFirstTurn = (player == State.Dealer && State.RoundNumber == 0);
        if (!isDealerFirstTurn)
        {
        if (State.Deck.Count > 0)
        {
            int drawn = State.Deck[^1];
            State.Deck.RemoveAt(State.Deck.Count - 1);
            State.Hands[player].Add(drawn);
            State.AddEvent("draw", player, drawn,
                $"摸牌: {MahjongTile.ToString(drawn)}");

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

            if (_rules.Phases.Any(p => p.ParallelElimination))
            {
                CheckHuaZhu();
                CheckTing();
            }
            Settle();
            return State.RecentEvents;
        }
        } // end if (!isDealerFirstTurn)

        // Phase 3: Player decides what to do with their drawn hand
        bool requireWinFan = _rules.WinMinFan > 0;
        var legalActions = _phaseMachine.GetLegalActions(State, player, requireWinFan);
        var (action, tile) = _human != null && player == _human.Name
            ? _human.Decide(legalActions, State)
            : _ais.First(a => a.Name == player).Decide(legalActions, State);

        if (action == "win")
        {
            var (wc, r258) = GetWinParams();
            int wildInHand = CountWildcardsInHand(State.Hands[player]);
            var result = _solver.CheckWin(State.Hands[player],
                wildcardCount: wildInHand, require258Pair: r258);
            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))
            {
                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)}");
        }

        AdvancePlayer();
        return State.RecentEvents;
    }

    /// <summary>Get wildcard count and 258-pair requirement for current rules.</summary>
    private (int wildcardCount, bool require258) GetWinParams()
    {
        int wc = _rules.WildcardRules != null ? _rules.Deck.WildcardCount : 0;
        bool r258 = _rules.WinCondition?.PairMustBe258 ?? false;
        return (wc, r258);
    }

    /// <summary>Count wildcard tiles in a hand (encoding 50-59).</summary>
    private static int CountWildcardsInHand(List<int> hand)
        => hand.Count(MahjongTile.IsWildcard);

    /// <summary>
    /// Let other players react to a discard (pung/kong/win).
    /// Returns true if someone reacted (turn passes to them).
    /// </summary>
    private bool HandleDiscardReactions(int discardTile)
    {
        // Collect claims from all alive players except the discarder
        var claims = new List<(string player, int priority, string action)>();
        string discarder = State.LastDiscardPlayer ?? "";

        // Check in player order (starting after discarder)
        int startIdx = State.PlayerOrder.IndexOf(discarder);
        for (int offset = 1; offset < State.PlayerOrder.Count; offset++)
        {
            string p = State.PlayerOrder[(startIdx + offset) % State.PlayerOrder.Count];
            if (!State.AlivePlayers.Contains(p)) continue;
            if (p == discarder) continue;

            int sameCount = State.Hands[p].Count(t => t == discardTile);
            string? claim = null;
            int priority = 0;

            // Check win first (highest priority)
            var handWithTile = new List<int>(State.Hands[p]) { discardTile };
            var (wc, r258) = GetWinParams();
            int wildInHand = CountWildcardsInHand(handWithTile);
            var winResult = _solver.CheckWin(handWithTile,
                wildcardCount: wildInHand, require258Pair: r258);
            if (winResult != null && winResult.IsWin)
                claim = "win";
            else if (sameCount >= 3)
                claim = "ming_kong";
            else if (sameCount >= 2)
                claim = "pung";

            if (claim == null) continue;
            priority = claim switch { "win" => 4, "ming_kong" => 3, "pung" => 2, _ => 0 };

            // For same priority, closer seat wins (first claim in order)
            // For higher priority, it overrides all previous claims
            if (claims.Count == 0 || priority > claims[0].priority)
                claims.Add((p, priority, claim));
            // Same priority: first claimant wins (closer to discarder in seat order)
            // Different (lower) priority: ignored — higher priority already claimed
        }

        if (claims.Count == 0) return false;
        var best = claims[0];
        string bp = best.player;

        if (best.action == "win")
        {
            // Remove the winning tile from pool (it's now part of the winning hand)
            State.DiscardPool.Remove(discardTile);

            var handWithTile = new List<int>(State.Hands[bp]) { discardTile };
            var (wc2, r2582) = GetWinParams();
            int wildInHand2 = CountWildcardsInHand(handWithTile);
            var winResult = _solver.CheckWin(handWithTile,
                wildcardCount: wildInHand2, require258Pair: r2582);
            State.HuPlayers.Add(bp);
            State.AlivePlayers.Remove(bp);
            State.AddEvent("win", bp, discardTile,
                $"胡！{MahjongTile.ToString(discardTile)}");

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

        if (best.action == "pung" || best.action == "ming_kong")
        {
            // Remove the discarded tile from pool (it's now in the meld)
            State.DiscardPool.Remove(discardTile);

            // Remove tiles from hand (pung: 2, ming_kong: 3)
            // The discard tile is taken from pool, not from hand
            int toRemove = best.action == "ming_kong" ? 3 : 2;
            for (int r = 0; r < toRemove; r++)
                State.Hands[bp].Remove(discardTile);

            // Create exposed meld
            int meldSize = best.action == "ming_kong" ? 4 : 3;
            var meldTiles = Enumerable.Repeat(discardTile, meldSize).ToList();
            State.Exposed[bp].Add(new Meld
            {
                Type = best.action,
                Tiles = meldTiles,
                SourcePlayer = discarder
            });
            State.CurrentPlayer = bp;
            State.LastDiscard = null;
            State.LastDiscardPlayer = null;
            State.AddEvent(best.action, bp, discardTile,
                best.action == "pung" ? "碰！" : "明杠！");

            // After pung/kong, the reacting player must discard a tile
            var hand = State.Hands[bp];
            if (hand.Count > 0)
            {
                int tileToDiscard = hand[Random.Shared.Next(hand.Count)];
                State.Hands[bp].Remove(tileToDiscard);
                State.LastDiscard = tileToDiscard;
                State.LastDiscardPlayer = bp;
                State.DiscardPool.Add(tileToDiscard);
                State.AddEvent("discard", bp, tileToDiscard,
                    $"出牌: {MahjongTile.ToString(tileToDiscard)}");
            }
            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;

        // All possible tiles that could be drawn (numbered 1-9 across 3 suits + 7 honors)
        var allPossibleTiles = MahjongTile.AllTiles(
            includeHonors: _rules.Deck.IncludeHonors,
            includeFlowers: false);

        foreach (var p in State.AlivePlayers)
        {
            bool ting = false;
            var hand = State.Hands[p];

            // For each possible tile we could draw, check if hand + tile is a win
            foreach (var tile in allPossibleTiles)
            {
                // Count how many of this tile exist (4 max per tile type)
                int alreadyHave = hand.Count(t => t == tile);
                if (alreadyHave >= 4) continue; // can't draw more of this tile

                var r = _solver.CheckWin(hand, newTile: tile,
                    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");
        }
    }

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