using SVSim.BattleNode.Bridge;
using SVSim.BattleNode.Protocol;
using SVSim.BattleNode.Sessions;
using SVSim.BattleNode.Sessions.Dispatch;
using SVSim.BattleNode.Sessions.Engine;

namespace SVSim.UnitTests.BattleNode.Integration;

/// <summary>
/// Node-native battle harness for the Headless-Conductor milestones (M-HC-*). It reproduces what
/// <c>BattleSession.EnsureEngineSetup</c> does — shuffle each side's deck from a FIXED master seed and
/// <c>SessionBattleEngine.Setup</c> the two seats — then exposes the engine + state + participants so
/// later milestone tests can drive multi-frame sequences and assert on engine board state.
///
/// <para>WHY drive the engine directly (not a full <c>BattleSession</c>): the session's <c>_state</c>
/// and <c>_engine</c> are private with no fixed-seed injection point, and every milestone assertion is
/// on engine board state. The engine (<c>SessionBattleEngine</c>) is the unit under test, so we seat it
/// the same way the session does and skip the WS/dispatch scaffolding.</para>
///
/// <para>The oracle by construction: the node assigns idx = position in the shuffled order
/// (<see cref="BattleSessionState.GetShuffledDeck"/>), and the engine's headless draw is lowest-Index
/// first, so a FIXED seed makes the engine's draw order reproduce the node's BY CONSTRUCTION.</para>
///
/// <para>Engine globals (<c>CardMaster</c>, <c>GameMgr</c>, <c>Wizard.Data</c>) are primed by
/// <c>SessionBattleEngine.Setup</c> itself (it calls <c>EngineGlobalInit.EnsureInitialized()</c>, which
/// loads the full cards.json from <c>AppContext.BaseDirectory/Data/cards.json</c>). The harness adds no
/// global init of its own. NOTE: unlike the live session, the harness does NOT acquire
/// <c>EngineSessionGate</c> — driving the engine directly bypasses it. One engine-backed battle at a
/// time is assumed within a test (the engine's process-global statics can't back two concurrently).</para>
/// </summary>
internal sealed class NodeNativeBattleHarness : IDisposable
{
    /// <summary>A deterministic master seed so deck shuffles (and the engine RNG stream born from it)
    /// are reproducible. Matches the value the engine construction tests use.</summary>
    public const int FixedMasterSeed = 12345;

    /// <summary>Default seat A viewer id — distinct from <see cref="DefaultSeatBViewerId"/> so the two
    /// sides shuffle independently (the shuffle seed mixes in the viewer id).</summary>
    public const long DefaultSeatAViewerId = 1001;
    public const long DefaultSeatBViewerId = 1002;

    /// <summary>Spellboost cost-reducer card (looking ahead to M-HC-3). Known id present in cards.json
    /// (sourced from tk2 battle capture / existing engine tests); a cards.json regeneration that drops
    /// it will produce a traceable failure here.</summary>
    public const long SpellboostCardId = 101314020;

    /// <summary>A second spellboost card seen in the tk2 capture. Known id present in cards.json
    /// (sourced from tk2 battle capture / existing engine tests); a cards.json regeneration that drops
    /// it will produce a traceable failure here.</summary>
    public const long SpellboostCardIdAlt = 100314020;

    /// <summary>A plain vanilla follower the engine resolution path proved out
    /// (HeadlessFixture.FollowerId). The bulk of the deterministic deck. Known id present in cards.json
    /// (sourced from tk2 battle capture / existing engine tests); a cards.json regeneration that drops
    /// it will produce a traceable failure here.</summary>
    public const long VanillaFollowerId = 100011010;

    public BattleSessionState State { get; }
    public StubParticipant SeatA { get; }
    public StubParticipant SeatB { get; }
    public SessionBattleEngine Engine { get; }

    /// <summary>This side's deck in the node's shuffled order (idx == position + 1).</summary>
    public IReadOnlyList<long> SeatADeck { get; }
    public IReadOnlyList<long> SeatBDeck { get; }

    private NodeNativeBattleHarness(
        BattleSessionState state, StubParticipant a, StubParticipant b, SessionBattleEngine engine,
        IReadOnlyList<long> seatADeck, IReadOnlyList<long> seatBDeck)
    {
        State = state;
        SeatA = a;
        SeatB = b;
        Engine = engine;
        SeatADeck = seatADeck;
        SeatBDeck = seatBDeck;
    }

    /// <summary>Build a 30-card deck: mostly the vanilla follower plus a couple of spellboost cards
    /// (so later milestones have a cost-reducer to play). All ids exist in cards.json.</summary>
    public static IReadOnlyList<long> DefaultDeck()
    {
        var deck = new List<long>(30) { SpellboostCardId, SpellboostCardIdAlt };
        deck.AddRange(Enumerable.Repeat(VanillaFollowerId, 30 - deck.Count));
        return deck;
    }

    /// <summary>Seat the engine exactly as <c>BattleSession.EnsureEngineSetup</c> does: shuffle each
    /// side's deck from the fixed seed via <see cref="BattleSessionState.GetShuffledDeck"/>, then
    /// <c>SessionBattleEngine.Setup(seed, deckA, deckB, classA, classB)</c>.</summary>
    public static NodeNativeBattleHarness Create(
        IReadOnlyList<long>? seatADeck = null,
        IReadOnlyList<long>? seatBDeck = null,
        CardClass seatAClass = CardClass.Forestcraft,
        CardClass seatBClass = CardClass.Swordcraft,
        int masterSeed = FixedMasterSeed)
    {
        var state = new BattleSessionState(masterSeed);

        var a = new StubParticipant(DefaultSeatAViewerId, MakeCtx(seatADeck ?? DefaultDeck(), seatAClass));
        var b = new StubParticipant(DefaultSeatBViewerId, MakeCtx(seatBDeck ?? DefaultDeck(), seatBClass));

        var shuffledA = state.GetShuffledDeck(a);
        var shuffledB = state.GetShuffledDeck(b);

        var engine = new SessionBattleEngine();
        engine.Setup(state.MasterSeed, shuffledA, shuffledB,
            (int)a.Context.ClassId, (int)b.Context.ClassId);

        return new NodeNativeBattleHarness(state, a, b, engine, shuffledA, shuffledB);
    }

    private static MatchContext MakeCtx(IReadOnlyList<long> deck, CardClass cls) => new(
        SelfDeckCardIds: deck,
        ClassId: cls, CharaId: ((int)cls).ToString(), CardMasterName: "card_master_node_10015",
        CountryCode: CountryCodes.Korea, UserName: "Player", SleeveId: "3000011",
        EmblemId: "701441011", DegreeId: "300003", FieldId: 43, IsOfficial: 0,
        BattleModeId: BattleModes.TakeTwo);

    // --- engine board-state pass-throughs (seat:true == player A, false == opponent B) ----------

    public bool IsReady => Engine.IsReady;
    public int LeaderLife(bool playerSeat) => Engine.LeaderLife(playerSeat);
    public int Pp(bool playerSeat) => Engine.Pp(playerSeat);
    public int HandCount(bool playerSeat) => Engine.HandCount(playerSeat);
    public int BoardCount(bool playerSeat) => Engine.BoardCount(playerSeat);
    public int DeckCount(bool playerSeat) => Engine.DeckCount(playerSeat);
    public int Turn(bool playerSeat) => Engine.Turn(playerSeat);

    /// <summary>The engine Index of seat A's hand card at <paramref name="handPos"/> (the playIdx a
    /// Play frame would carry to play it).</summary>
    public int PlayerHandCardIndex(int handPos) => Engine.HandCardIndex(playerSeat: true, handPos);

    /// <summary>Build an envelope for <paramref name="body"/> and ingest it into the engine for the
    /// given seat (player == seat A). Mirrors <c>BattleNodeFlowTests.MakeEnvelopeWith</c> +
    /// <c>SessionBattleEngine.Receive</c>.</summary>
    public EngineIngestResult Push(NetworkBattleUri uri, Dictionary<string, object?> body, bool isPlayerSeat)
    {
        var seat = isPlayerSeat ? SeatA : SeatB;
        var env = new MsgEnvelope(
            uri, ViewerId: seat.ViewerId, Uuid: "udid-test", Bid: null, RetryAttempt: 0,
            Cat: EmitCategory.Battle, PubSeq: null, PlaySeq: null,
            Body: new RawBody(body));
        return Engine.Receive(env, isPlayerSeat);
    }

    public void Dispose() { /* engine holds no unmanaged resources; nothing to release. */ }

    /// <summary>Minimal test-only <see cref="IBattleParticipant"/> exposing only the
    /// <see cref="ViewerId"/> + <see cref="Context"/> that the harness reads. Broker members
    /// (<c>PushAsync</c>, <c>RunAsync</c>, <c>TerminateAsync</c>) throw <see cref="NotSupportedException"/>
    /// — the harness drives the engine directly, so a frame must never reach the participant relay.
    /// Silent no-ops would let a misrouted push pass undetected.</summary>
    internal sealed class StubParticipant : IBattleParticipant
    {
        public long ViewerId { get; }
        public MatchContext Context { get; }

        public StubParticipant(long viewerId, MatchContext context)
        {
            ViewerId = viewerId;
            Context = context;
        }

#pragma warning disable CS0067 // FrameEmitted is part of the interface but the stub never raises it.
        public event Func<MsgEnvelope, CancellationToken, Task>? FrameEmitted;
#pragma warning restore CS0067

        public Task PushAsync(MsgEnvelope envelope, Stock stock, CancellationToken ct) =>
            throw new NotSupportedException("StubParticipant.PushAsync — harness drives the engine directly; a frame must not reach the participant relay.");
        public Task RunAsync(CancellationToken ct) =>
            throw new NotSupportedException("StubParticipant.RunAsync should not be called in harness tests.");
        public Task TerminateAsync(BattleFinishReason reason) =>
            throw new NotSupportedException("StubParticipant.TerminateAsync should not be called in harness tests.");
        public ValueTask DisposeAsync() => ValueTask.CompletedTask;
    }
}