extern alias engine;
using System.Reflection;
using System.Runtime.Serialization;
using engine::SVSim.BattleEngine.Rng;
using SVSim.BattleNode.Protocol;
using NetworkBattleReceiver = engine::NetworkBattleReceiver;
using NetworkBattleDefine = engine::NetworkBattleDefine;
using BattleManagerBase = engine::BattleManagerBase;
using BattlePlayerBase = engine::BattlePlayerBase;
using BattleCardBase = engine::BattleCardBase;
using ClassBattleCardBase = engine::ClassBattleCardBase;
using CardCreatorBase = engine::CardCreatorBase;
using CostAddModifier = engine::CostAddModifier;
using SBattleLoad = engine::SBattleLoad;
using CardTemplate = engine::CardTemplate;
using GameObject = engine::UnityEngine.GameObject;
using RealTimeNetworkAgent = engine::RealTimeNetworkAgent;
using Gungnir = engine::Gungnir;
using NetworkNullLogger = engine::NetworkNullLogger;
using ToolboxGame = engine::Wizard.ToolboxGame;
using GameMgr = engine::GameMgr;
using BattleUIContainer = engine::BattleUIContainer;
using BackGroundBase = engine::BackGroundBase;
using NullPlayerEmotion = engine::Wizard.Battle.Player.Emotion.NullPlayerEmotion;
using NetworkMulliganPhase = engine::Wizard.Battle.Phase.NetworkMulliganPhase;
using MulliganInfoControl = engine::Wizard.Battle.Mulligan.MulliganInfoControl;
using UIWidget = engine::UIWidget;
using UISprite = engine::UISprite;
using NullDetailPanelControl = engine::NullDetailPanelControl;
using DetailPanelControl = engine::DetailPanelControl;

namespace SVSim.BattleNode.Sessions.Engine;

/// <summary>One authoritative engine per BattleSession, seated as both players (design ND2). A faithful
/// SHADOW: it mirrors each client's resolved play, never overrides/rejects/originates (ND1). Ingest is
/// the engine's own NetworkBattleReceiver.ReceivedMessage (ND4); isPlayer selects the seat (F-N-2).
///
/// The headless wiring here is the production analogue of the test HeadlessFixture
/// (NewNetworkEmitBattle / SeedDeck / InitLeaderLife / InitCardTemplates). It deliberately omits the
/// emit-only RealTimeNetworkAgent scaffolding the test uses for the SEND path — the shadow engine only
/// RECEIVES (F-N-2), so no socket-agent is constructed. The engine's global init (CardMaster, GameMgr,
/// Wizard.Data) is the caller's responsibility (the test does HeadlessEngineEnv.EnsureInitialized;
/// the live node guards Setup in try/catch so an un-initialized host degrades to a no-op shadow).</summary>
internal sealed class SessionBattleEngine
{
    private const int DefaultLeaderLife = 20;

    private HeadlessNetworkBattleMgr? _mgr;
    private NetworkBattleReceiver? _receiver;

    /// <summary>True once Setup has built the two-seat battle.</summary>
    public bool IsReady => _mgr is not null;

    /// <summary>Construct the two-seat network battle from both decks + the master seed (design F-N-5).
    /// <paramref name="seatADeck"/>/<paramref name="seatBDeck"/> are the per-side deck orders the node
    /// already computed (BattleSessionState.GetShuffledDeck) and handed each client.
    /// <paramref name="seatAClass"/>/<paramref name="seatBClass"/> are each seat's class ordinal (1..8,
    /// the <c>CardClass</c> int value); they select the leader's class via the all-8-class
    /// ClassCharacterList EngineGlobalInit installs (chara_id == class_id for 1..8). The 3-arg overload
    /// behavior is preserved by the defaults (1/2), matching the test-harness charaIds.
    /// <para>NOTE: GameMgr (the leader chara ids set below) is a PROCESS GLOBAL. Setting per-session
    /// chara ids is therefore only safe while exactly one engine-backed battle exists at a time — the
    /// invariant <see cref="EngineSessionGate"/> enforces on the caller side.</para></summary>
    public void Setup(int masterSeed,
        IReadOnlyList<long> seatADeck, IReadOnlyList<long> seatBDeck,
        int seatAClass = 1, int seatBClass = 2)
    {
        // Prime the engine's process-global statics (CardMaster, Wizard.Data, all-8-class Master,
        // GameMgr/netUser/udid). Idempotent (process-once); makes the LIVE host ready so Setup succeeds
        // here rather than throwing into the shadow's no-op path (Phase 2 N2, carried-risk A).
        EngineGlobalInit.EnsureInitialized();

        // rng defaults to SeededRandomSource(masterSeed) inside the mgr — the stream is born aligned
        // with the seed the node handed both clients (F-N-5; O-N-2 "bit-aligned anyway").
        var mgr = new HeadlessNetworkBattleMgr(new SessionContentsCreator(masterSeed));
        // Recovery mode is the engine's OWN headless replay path: the live view/UI touches on the
        // receive cycle (BattleUIContainer.DisableMenu, turn-control UI, card-view creation, VFX
        // waits) are all gated `!IsRecovery` (BattleUIContainer.cs:130, BattleManagerBase.cs:1499+),
        // so this collapses them to no-ops without changing authoritative state. Set AFTER construction
        // so the ctor still wired the LIVE NetworkBattleReceiver (ND4) rather than the replay receiver.
        // Safe for shadow: the only thing !IsRecovery additionally enables is EMIT, which a pure shadow
        // never does (it never originates a send).
        mgr.IsRecovery = true;

        // Seat each player as the other's opponent (private field on BattlePlayerBase, as the real
        // match-load does). Mirrors HeadlessFixture.NewNetworkEmitBattle.
        BattlePlayerBase player = mgr.GetBattlePlayer(isPlayer: true);
        BattlePlayerBase enemy = mgr.GetBattlePlayer(isPlayer: false);
        SetField(player, "_opponentBattlePlayer", enemy);
        SetField(enemy, "_opponentBattlePlayer", player);
        player.IsSelfTurn = true;
        enemy.IsSelfTurn = false;

        InitLeaderLife(mgr);       // a 0-life leader reads as game-over and silently blocks plays
        InitCardTemplates(mgr);    // play/draw resolution touches the (no-op) card view layer
        InitHeadlessViews(mgr);    // turn/play cycle dereferences UI-container + emotion refs
        InstallHeadlessNetworkAgent(); // turn-flow resolve reads ToolboxGame.RealTimeNetworkAgent

        // Per-session leader class: chara_id == class_id for 1..8 in the all-8-class ClassCharacterList,
        // so writing the seats' class ordinals into GameMgr's DataMgr resolves each leader's correct
        // class. Process-global — safe only under EngineSessionGate (see method remarks above).
        SetGameMgrCharaIds(seatAClass, seatBClass);

        SeedDeck(mgr, seatADeck, isPlayer: true);
        SeedDeck(mgr, seatBDeck, isPlayer: false);

        WireMulliganPhase(mgr);    // wire OperateReceive.OnReceiveDeal -> StartDeal (deal seats the hand)

        _mgr = mgr;
        // Use the mgr's OWN receiver — the ctor already wired it to the mgr's OperateReceive +
        // NetworkBattleData (NetworkBattleManagerBase.cs:266, non-recovery branch). This is the same
        // receiver the engine's RecoveryDataHandler drives when replaying recorded frames.
        _receiver = mgr.GetNetworkBattleReceiver();
    }

    /// <summary>Ingest one client frame into the engine for the given seat. <paramref name="isPlayerSeat"/>
    /// maps the sender to the engine's player(true)/opponent(false) seat (F-N-2). A throw/reject is
    /// returned as a detected-desync EVENT (ND6), never silently absorbed.</summary>
    public EngineIngestResult Receive(MsgEnvelope env, bool isPlayerSeat)
    {
        if (_mgr is null || _receiver is null)
            throw new InvalidOperationException("Receive before Setup.");

        var dict = ToEngineDict((env.Body as RawBody)?.Entries);
        var uri = MapUri(env.Uri);

        try
        {
            // Mirror the engine's own recorded-frame replay (RecoveryDataHandler.cs:283): every
            // ingested action resolves through the isHaveSequence ConductReceiveData path, and
            // checkBreakData:false so a partial/handshake frame is not rejected as a break.
            bool accepted = _receiver.ReceivedMessage(
                uri, isHaveSequence: true, dict, isPlayerSeat, handler: null, checkBreakData: false);
            return accepted ? EngineIngestResult.Ok() : EngineIngestResult.Reject($"receiver rejected {env.Uri}");
        }
        catch (Exception ex)
        {
            // Keep the first few frames: a headless-gap NRE/ANE is almost always diagnosable from the
            // call chain (the throwing leaf is often a ThrowHelper, so one frame is too few).
            var site = string.Join(" || ", (ex.StackTrace ?? "").Split('\n').Take(4).Select(s => s.Trim()));
            return EngineIngestResult.Reject($"{env.Uri} threw: {ex.GetType().Name}: {ex.Message} @ {site}");
        }
    }

    // --- live board-state reads (N1 oracle surface; design F-N-4 board-state reads) ----------------
    // Each returns LIVE engine state off the seated player, mirroring the Phase-1 oracle reads
    // (VanillaFollowerOracleTests: player.Pp, player.HandCardList.Count, ClassAndInPlayCardList,
    // leader == the Class card). seat:true == player, false == opponent (F-N-2).

    public int LeaderLife(bool playerSeat) => Seat(playerSeat).Class.Life;
    public int Pp(bool playerSeat) => Seat(playerSeat).Pp;
    public int HandCount(bool playerSeat) => Seat(playerSeat).HandCardList.Count;
    public int DeckCount(bool playerSeat) => Seat(playerSeat).DeckCardList.Count;
    public int Turn(bool playerSeat) => Seat(playerSeat).Turn;

    /// <summary>Followers in play, excluding the leader (the Class card occupies one slot of
    /// ClassAndInPlayCardList).</summary>
    public int BoardCount(bool playerSeat) => Math.Max(0, Seat(playerSeat).ClassAndInPlayCardList.Count - 1);

    /// <summary>The engine <c>Index</c> of the hand card at the given hand position. The receive-path
    /// Play frame addresses a card by its engine Index (playIdx), which equals deck position + 1 for
    /// a card dealt from the seeded deck.</summary>
    public int HandCardIndex(bool playerSeat, int handPos) => Seat(playerSeat).HandCardList[handPos].Index;

    /// <summary>The real <c>CardId</c> (wire identity) of the in-play follower at <paramref name="boardPos"/>
    /// (0-based, skipping the leader/Class card at ClassAndInPlayCardList[0] — same convention as
    /// <see cref="BoardCount"/>). Used to assert an opponent reveal seated the substituted card with its
    /// true identity (M-HC-2): before the reveal the slot holds a hidden dummy (cardId 0); after, the
    /// engine-resolved actual card carries the wire cardId.</summary>
    public int InPlayCardId(bool playerSeat, int boardPos) =>
        Seat(playerSeat).ClassAndInPlayCardList[boardPos + 1].CardId;

    /// <summary>The engine-RESOLVED play-time cost of the card whose engine <c>Index</c> == <paramref name="idx"/>
    /// on <paramref name="playerSeat"/> (M-HC-3a). This is the discounted cost the play actually paid —
    /// spellboost reduction, board-dependent modifiers and all — read straight off the engine, so the
    /// opponent-facing knownList carries the SAME cost the engine charged (closing the spellboost
    /// cost-desync BY CONSTRUCTION: no bookkeeping, the engine already knows).
    /// <para>READ-MOMENT: the conductor's <c>ShadowIngest</c> runs <c>engine.Receive</c> (→ resolves the
    /// play) BEFORE the handler runs, so at read time the played card has LEFT the hand — a follower sits
    /// in <c>ClassAndInPlayCardList</c>, a spell in <c>CemeteryList</c>. <see cref="BattleCardBase.PlayCard"/>
    /// captures <c>_playedCost = useCost</c> (== the fully-resolved <c>Cost</c> at the moment of play,
    /// incl. every CostModifier) onto the card object, which persists after the card leaves the hand —
    /// so <see cref="BattleCardBase.PlayedCost"/> is the authoritative play-time discounted cost. We search
    /// the seat's post-resolution zones (in-play, cemetery) by <c>Index</c>, then fall back to the hand
    /// (a not-yet-resolved card, e.g. a degenerate test path) reading the live <c>Cost</c> there.</para>
    /// <para>Degrades to <paramref name="fallback"/> when the engine is not set up (the single-active-engine
    /// gate left this session without an owned engine) or the idx resolves to no card — so a non-engine
    /// session never crashes and a vanilla play simply emits its base cost via the caller's fallback.</para></summary>
    public int PlayedCardCost(bool playerSeat, int idx, int fallback = 0)
    {
        if (_mgr is null) return fallback;
        var card = FindByIndex(Seat(playerSeat), idx);
        if (card is null) return fallback;
        // PlayedCost is set (>= 0) once PlayCard resolved the play; before that (a card still in hand on a
        // degenerate path) read the live Cost, which already folds in any registered CostModifier.
        return card.PlayedCost >= 0 ? card.PlayedCost : card.Cost;
    }

    // Locate the card with the given engine Index across the seat's post-resolution zones. Order matters
    // only for disambiguation; Index is unique per card so the first hit is the card. In-play (followers)
    // and cemetery (spells) are where a just-resolved play lands; hand is the pre-resolution fallback.
    private static BattleCardBase? FindByIndex(BattlePlayerBase seat, int idx)
    {
        foreach (var c in seat.ClassAndInPlayCardList)
            if (c.Index == idx) return c;
        foreach (var c in seat.CemeteryList)
            if (c.Index == idx) return c;
        foreach (var c in seat.HandCardList)
            if (c.Index == idx) return c;
        return null;
    }

    /// <summary>TEST SEAM (M-HC-3a validation): register a cost-reducing modifier on the hand card at
    /// engine <c>Index</c> == <paramref name="idx"/>, mimicking what card 101314020's <c>when_spell_charge</c>
    /// <c>cost_change add=ADD_CHARGE_COUNT*-1</c> skill does once it has accumulated <paramref name="charge"/>
    /// spellboost charges (each charge adds a <c>CostAddModifier(-1)</c>; the engine's own
    /// <see cref="Skill_cost_change"/> builds exactly this). Used to drive the count→cost resolution
    /// deterministically headless without pumping the (VFX-coupled) spell-charge skill chain through a
    /// real multi-spell sequence — the engine's authentic <see cref="BattleCardBase.Cost"/> getter then
    /// resolves the discount, and <see cref="BattleCardBase.PlayCard"/> captures it as PlayedCost on the
    /// next play. Returns the resolved hand-card Cost AFTER seeding (base − charge) for the caller to pin.
    /// No-op-returns -1 if the engine isn't set up or no hand card has that Index.</summary>
    internal int SeedHandCardSpellboostCost(bool playerSeat, int idx, int charge)
    {
        if (_mgr is null) return -1;
        BattleCardBase? card = null;
        foreach (var c in Seat(playerSeat).HandCardList)
            if (c.Index == idx) { card = c; break; }
        if (card is null) return -1;
        for (int i = 0; i < charge; i++)
            card.AddCostModifier(new CostAddModifier(-1), null, eventCall: false);
        card.SetSpellChargeCount(charge); // keep the charge count consistent with the modifiers (cosmetic here)
        return card.Cost;
    }

    private engine::BattlePlayerBase Seat(bool playerSeat) =>
        (_mgr ?? throw new InvalidOperationException("read before Setup")).GetBattlePlayer(playerSeat);

    private static NetworkBattleDefine.NetworkBattleURI MapUri(NetworkBattleUri uri)
        => Enum.Parse<NetworkBattleDefine.NetworkBattleURI>(uri.ToString());

    // The receiver reads keys via Enum.IsDefined over NetworkParameter and casts nested values to
    // List<object> / Dictionary<string,object>; the node decodes nested data as the nullable
    // List<object?> / Dictionary<string,object?>. Rebox to the non-nullable shape, dropping nulls
    // (the receiver presence-checks keys, so an absent key is the correct encoding of a null).
    private static Dictionary<string, object> ToEngineDict(Dictionary<string, object?>? entries)
    {
        var result = new Dictionary<string, object>();
        if (entries is null) return result;
        foreach (var (k, v) in entries)
            if (v is not null) result[k] = Rebox(v);
        return result;
    }

    private static object Rebox(object v) => v switch
    {
        Dictionary<string, object?> d => d.Where(kv => kv.Value is not null)
                                          .ToDictionary(kv => kv.Key, kv => Rebox(kv.Value!)),
        List<object?> l => l.Where(x => x is not null).Select(x => Rebox(x!)).ToList(),
        _ => v,
    };

    // --- headless wiring (production analogue of HeadlessFixture) -----------------------------------

    private static void InitLeaderLife(BattleManagerBase mgr, int life = DefaultLeaderLife)
    {
        ((ClassBattleCardBase)mgr.GetBattlePlayer(true).Class).InitBaseMaxLife(life);
        ((ClassBattleCardBase)mgr.GetBattlePlayer(false).Class).InitBaseMaxLife(life);
    }

    private static void InitCardTemplates(BattleManagerBase mgr)
    {
        mgr.SBattleLoad = new SBattleLoad
        {
            UnitCardTemplate = new CardTemplate(),
            SpellCardTemplate = new CardTemplate(),
            FieldCardTemplate = new CardTemplate(),
        };
        mgr.Battle3DContainer = new GameObject();
        mgr.CardHolder = new GameObject();
        mgr.ECardHolder = new GameObject();
        mgr.PCardPlace = new GameObject();
        mgr.ChoiceCardHolder = new GameObject();
        mgr.EvolveCardHolder = new GameObject();
    }

    // Seed the no-op UI refs the receive/turn cycle dereferences. Under IsRecovery the methods on
    // these (e.g. BattleUIContainer.DisableMenu) no-op, but the receiver still CALLS them, so the
    // references must be non-null. PlayerEmotion is the engine's own NullPlayerEmotion.
    private static void InitHeadlessViews(BattleManagerBase mgr)
    {
        mgr.BattleUIContainer = (BattleUIContainer)FormatterServices.GetUninitializedObject(typeof(BattleUIContainer));
        // Revealed-card creation (ReplaceReceivedCard.CreateActualCard -> CreateBaseCardGameObject)
        // clones the card prefab under _backGround.m_Battle3DContainer — a field distinct from
        // mgr.Battle3DContainer. Seed a no-op BackGround with a non-null container.
        var bg = (BackGroundBase)FormatterServices.GetUninitializedObject(typeof(BackGroundBase));
        SetProperty(bg, "m_Battle3DContainer", new GameObject());
        SetField(mgr, "_backGround", bg);
        // PlayerEmotion is declared on BattlePlayer (the player seat); BattleEnemy has none — set
        // where present.
        TrySetProperty(mgr.GetBattlePlayer(true), "PlayerEmotion", new NullPlayerEmotion());
        TrySetProperty(mgr.GetBattlePlayer(false), "PlayerEmotion", new NullPlayerEmotion());

        // The receive play path runs SetupActionProcessorEvent (BattlePlayerBase.cs:1431/1438), which
        // wires BattleMgr.DetailMgr.DetailPanelControl.UpdateCardDescription* into OnPlayComplete/
        // OnEvolutionComplete. DetailMgr is created in CreateManager but its panel controls are null
        // headless. Seed the engine's own NullDetailPanelControl no-op (IDetailPanelControl) + an
        // uninitialized SubDetailPanelControl (concrete DetailPanelControl, read on other action arms).
        mgr.DetailMgr.DetailPanelControl = new NullDetailPanelControl();
        mgr.DetailMgr.SubDetailPanelControl =
            (DetailPanelControl)FormatterServices.GetUninitializedObject(typeof(DetailPanelControl));
    }

    // Hold a strong reference to the wired mulligan phase: its StartDeal closure is what
    // OperateReceive.OnReceiveDeal invokes, and it stores the mulligan mgr/controls that seat the hand.
    private NetworkMulliganPhase? _mulliganPhase;

    // Wire the receive path's deal handler. In production the phase machine advances to
    // NetworkMulliganPhase, whose Setup/MulliganEventSetting wires OperateReceive.OnReceiveDeal ->
    // MulliganPhaseBase.StartDeal (NetworkMulliganPhase.cs:91). The node never pumps the phase machine
    // (BattleManagerBase.Update is never called), and the node's PhaseCreator yields no NetworkMulligan
    // phase anyway — so construct the phase directly and run MulliganEventSetting() to install that
    // delegate. The phase ctor's Initialize builds the player/opponent mulligan controls (PlayerMlgCtrl
    // via InitMulligan) off the no-op view leaves the shim GameObject lazily materializes. The DEAL
    // mutation (cards deck->hand) happens synchronously inside StartDeal -> CreateMulliganDealList +
    // DrawFirstMulliganCard; the VFX it returns are cosmetic (dropped by HeadlessConductorVfxMgr).
    private void WireMulliganPhase(HeadlessNetworkBattleMgr mgr)
    {
        // The phase ctor's Initialize does NGUITools.AddChild(Battle3DContainer,
        // GetPrefabMgr().Get("Prefab/UI/MulliganInfo")).GetComponent<MulliganInfoControl>(). PrefabMgr.Get
        // returns null for an unregistered prefab (engine logic — not editable), and AddChild(parent,
        // null) -> Instantiate(null) -> null -> NRE on GetComponent. Seed a no-op GameObject under that
        // key so AddChild clones it and the shim GameObject lazily materializes a no-op
        // MulliganInfoControl. Node seed (allowed); the control is never shown/updated headless.
        var prefab = new GameObject();
        SeedMulliganInfoControl(prefab);
        var prefabData = GameMgr.GetIns().GetPrefabMgr().GetPrefabData();
        prefabData["Prefab/UI/MulliganInfo"] = prefab;

        var phase = new NetworkMulliganPhase(mgr, mgr.NetworkSender);
        phase.MulliganEventSetting();
        _mulliganPhase = phase;
    }

    // Materialize a no-op MulliganInfoControl on the prefab GameObject and seed the view-leaf fields the
    // phase ctor's PlayerMulliganView ctor -> MulliganInfoControl.InitMulliganInfo reads:
    //   _partsPlayer/_partsOpponent (private nested MulliganParts) — each needs a non-null _exchangeMark
    //     array (read for .Length in InitMulliganInfo) plus non-null _keepZone/_abandonZone UIWidgets
    //     (read for .gameObject elsewhere on the mulligan path).
    // The shim GameObject lazily creates the MulliganInfoControl but does NOT fill the MulliganParts
    // (it isn't a Component, so WireComponentFields skips it). Node seed (allowed) — pure no-op view leaves.
    private static void SeedMulliganInfoControl(GameObject prefab)
    {
        var ctrl = prefab.GetComponent<MulliganInfoControl>(); // Shim GameObject.GetComponent<T>() lazily materialises a no-op component — not a real Unity scene; this is intentional and will not NRE.
        var partsType = typeof(MulliganInfoControl)
            .GetNestedType("MulliganParts", BindingFlags.NonPublic)
            ?? throw new InvalidOperationException("MulliganInfoControl.MulliganParts nested type not found");
        SetField(ctrl, "_partsPlayer", BuildMulliganParts(partsType));
        SetField(ctrl, "_partsOpponent", BuildMulliganParts(partsType));
    }

    private static object BuildMulliganParts(Type partsType)
    {
        var parts = FormatterServices.GetUninitializedObject(partsType);
        SetField(parts, "_exchangeMark", Array.CreateInstance(typeof(UISprite), 0));
        SetField(parts, "_keepZone", NewUiWidget());
        SetField(parts, "_abandonZone", NewUiWidget());
        return parts;
    }

    // A UIWidget is read for .gameObject (Component.gameObject) on the mulligan path; create one on a
    // fresh GameObject so its gameObject backref resolves.
    private static UIWidget NewUiWidget() => new GameObject().GetComponent<UIWidget>();

    /// <summary>Seat one side's full deck in order (idx == list position + 1). Each card is created
    /// through the engine's own null-view seam and pushed via AddToDeck — the SeedDeck primitive the
    /// test harness proved (HeadlessFixture.SeedDeck).</summary>
    private static void SeedDeck(BattleManagerBase mgr, IReadOnlyList<long> deck, bool isPlayer)
    {
        BattlePlayerBase owner = mgr.GetBattlePlayer(isPlayer);
        for (int i = 0; i < deck.Count; i++)
        {
            var card = CreateHeadlessCard(mgr, (int)deck[i], index: i + 1, isPlayer);
            owner.AddToDeck(card);
        }
    }

    private static readonly MethodInfo CreateCardWithoutResources =
        typeof(CardCreatorBase).GetMethod("CreateCardWithoutResources",
            BindingFlags.NonPublic | BindingFlags.Static)
        ?? throw new InvalidOperationException("CardCreatorBase.CreateCardWithoutResources not found");

    private static BattleCardBase CreateHeadlessCard(BattleManagerBase mgr, int cardId, int index, bool isPlayer)
    {
        var io = mgr.CreatePlayerInnerOptionsBuilder();
        var card = (BattleCardBase)CreateCardWithoutResources.Invoke(
            null, new object[] { cardId, index, isPlayer, mgr, io })!;
        mgr.GetBattlePlayer(isPlayer).SetupCardEvent(card);
        return card;
    }

    // The turn-flow + emit bookkeeping reads the global ToolboxGame.RealTimeNetworkAgent (e.g.
    // RealTimeNetworkAgent.GetIsFirstPlayer/GetTurnState, which delegate to GameMgr's
    // NetworkUserInfoData.TurnState; AddActionSequence touches _gungnir). Headless there is no socket
    // agent, so seed a no-op one — mirroring HeadlessFixture.NewNetworkEmitBattle. _notEmit short-
    // circuits the byte-push before any socket I/O; the shadow engine never originates a send anyway.
    // NOTE: this is a process-global; one engine per process is assumed for the shadow (revisit for
    // live multi-session — see design O-N status). Idempotent enough for the per-battle setup.
    private static void InstallHeadlessNetworkAgent()
    {
        var agent = (RealTimeNetworkAgent)FormatterServices.GetUninitializedObject(typeof(RealTimeNetworkAgent));
        agent.SetCurrentMatchingStatus(RealTimeNetworkAgent.MatchingStatus.Prepared);
        SetField(agent, "_gungnir", FormatterServices.GetUninitializedObject(typeof(Gungnir)));
        SetProperty(agent, "NetworkLogger", new NetworkNullLogger());
        SetField(agent, "_notEmit", true);
        ToolboxGame.SetRealTimeNetworkBattle(agent);
    }

    // Write the two seats' class ordinals into GameMgr's DataMgr leader chara ids. Mirrors the test
    // seam HeadlessFixture.cs:202-204 (SetField(dm, "_playerCharaId"/"_enemyCharaId", ...)). chara_id ==
    // class_id for 1..8 in EngineGlobalInit's all-8-class ClassCharacterList, so the ordinal selects the
    // class. A non-positive ordinal (e.g. CardClass.None == 0) clamps to the default seat (1/2).
    // GameMgr is a process global → safe only under EngineSessionGate (one engine-backed battle at a
    // time).
    private static void SetGameMgrCharaIds(int a, int b)
    {
        var dm = GameMgr.GetIns().GetDataMgr();
        SetField(dm, "_playerCharaId", a <= 0 ? 1 : a);
        SetField(dm, "_enemyCharaId", b <= 0 ? 2 : b);
    }

    private static void SetField(object obj, string name, object value)
    {
        var f = obj.GetType().GetField(name,
            BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public)
            ?? throw new InvalidOperationException($"{obj.GetType().Name} has no field '{name}'");
        f.SetValue(obj, value);
    }

    private static void SetProperty(object obj, string name, object value)
    {
        var t = obj.GetType();
        PropertyInfo? p = null;
        while (t is not null && p is null)
        {
            p = t.GetProperty(name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
            t = t.BaseType;
        }
        (p ?? throw new InvalidOperationException($"{obj.GetType().Name} has no property '{name}'"))
            .SetValue(obj, value);
    }

    private static void TrySetProperty(object obj, string name, object value)
    {
        var t = obj.GetType();
        while (t is not null)
        {
            var p = t.GetProperty(name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
            if (p is not null) { p.SetValue(obj, value); return; }
            t = t.BaseType;
        }
    }
}