using Microsoft.Extensions.Logging;
using SVSim.BattleNode.Lifecycle;
using SVSim.BattleNode.Protocol;
using SVSim.BattleNode.Protocol.Bodies;
using SVSim.BattleNode.Sessions.Dispatch;
using SVSim.BattleNode.Sessions.Dispatch.Handlers;
using SVSim.BattleNode.Sessions.Participants;

namespace SVSim.BattleNode.Sessions;

/// <summary>
/// v2 broker session. Holds two participants and brokers between them. Subscribes
/// to each participant's <see cref="IBattleParticipant.FrameEmitted"/>; on each frame,
/// runs <see cref="ComputeFrames"/> to determine the routing (target + frame + noStock
/// flag) and dispatches via <see cref="IBattleParticipant.PushAsync"/>.
/// </summary>
/// <remarks>
/// Phase 1 wires this for <see cref="BattleType.Scripted"/> only — the dispatch logic
/// preserves v1.2 behaviour. Phase 2 wires Pvp (broadcast Matched/BattleStart per-perspective,
/// forward gameplay frames between participants). Phase 3 wires Bot (ack-only).
/// </remarks>
public sealed class BattleSession
{
    private readonly ILogger<BattleSession> _log;

    private readonly BattleSessionState _state = new();

    public string BattleId { get; }
    public BattleType Type { get; }
    public IBattleParticipant A { get; }
    public IBattleParticipant B { get; }
    public BattleSessionPhase Phase => _state.SessionPhase;

    // Per-URI handlers consulted before the legacy switch. Populated incrementally (Tasks 5-14);
    // each registered URI is served by its handler and its legacy switch arm goes dead.
    private static readonly IReadOnlyDictionary<NetworkBattleUri, IFrameHandler> Handlers =
        new Dictionary<NetworkBattleUri, IFrameHandler>
        {
            [NetworkBattleUri.InitNetwork] = new InitNetworkHandler(),
            [NetworkBattleUri.InitBattle] = new InitBattleHandler(),
            [NetworkBattleUri.Loaded] = new LoadedHandler(),
        };

    private FrameDispatchContext BuildContext(IBattleParticipant from, MsgEnvelope env) =>
        new()
        {
            A = A, B = B, From = from, Other = ReferenceEquals(from, A) ? B : A,
            Env = env, Type = Type, BattleId = BattleId, State = _state,
        };

    public BattleSession(string battleId, BattleType type, IBattleParticipant a, IBattleParticipant b,
        ILogger<BattleSession> log)
    {
        BattleId = battleId;
        Type = type;
        A = a;
        B = b;
        _log = log;

        // Subscribe to both participants' emissions.
        A.FrameEmitted += OnFrameFromA;
        B.FrameEmitted += OnFrameFromB;
    }

    public async Task RunAsync(CancellationToken cancellation)
    {
        using var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellation);
        var aTask = A.RunAsync(cts.Token);
        var bTask = B.RunAsync(cts.Token);

        if (Type == BattleType.Pvp)
        {
            // WhenAny: first WS drop / first graceful close triggers cascade.
            // ScriptedBotParticipant.RunAsync also returns immediately; that's not used
            // here (Pvp has two RealParticipants), but we'd still want a synthesized
            // BattleFinish for the survivor if either side terminates first.
            var first = await Task.WhenAny(aTask, bTask).ConfigureAwait(false);
            var survivor = first == aTask ? B : A;

            if (Phase != BattleSessionPhase.Terminal)
            {
                // Involuntary drop (no graceful Retire): synthesize BattleFinish(DisconnectWin)
                // to survivor. DisconnectWin=201 → client renders "opponent disconnected" →
                // WIN UI; the legacy Win=1 used here previously rendered "no contest".
                try
                {
                    await survivor.PushAsync(
                        BattleFrames.BuildBattleFinish(BattleResult.DisconnectWin), noStock: true, cancellation)
                        .ConfigureAwait(false);
                }
                catch (Exception ex)
                {
                    _log.LogWarning(ex,
                        "BattleSession {Bid}: failed to push BattleFinish to survivor (their WS may also be closed)",
                        BattleId);
                }
                _state.SessionPhase = BattleSessionPhase.Terminal;
            }

            cts.Cancel(); // unblock the survivor's RunAsync read loop
            try { await Task.WhenAll(aTask, bTask).ConfigureAwait(false); }
            catch { /* swallow cancellation / WS exceptions */ }
        }
        else
        {
            // Phase 1 semantics for Scripted/Bot: wait for ALL participants. The bot's
            // RunAsync returns immediately; the session keeps running for the real one.
            try { await Task.WhenAll(aTask, bTask).ConfigureAwait(false); }
            catch { /* swallow */ }
        }

        // Audit Md11 — release per-participant outbound archives at battle-end
        // (only RealParticipant has one; bots don't archive). Heavy state is
        // dropped synchronously here so the participant's TerminateAsync doesn't
        // need to keep the dict alive through its disposal handshake.
        if (A is RealParticipant rpA) rpA.Outbound.Clear();
        if (B is RealParticipant rpB) rpB.Outbound.Clear();

        await Task.WhenAll(
            A.TerminateAsync(BattleFinishReason.NormalFinish),
            B.TerminateAsync(BattleFinishReason.NormalFinish))
            .ConfigureAwait(false);
    }

    private Task OnFrameFromA(MsgEnvelope env, CancellationToken ct) => HandleFrameAsync(A, env, ct);
    private Task OnFrameFromB(MsgEnvelope env, CancellationToken ct) => HandleFrameAsync(B, env, ct);

    private async Task HandleFrameAsync(IBattleParticipant from, MsgEnvelope env, CancellationToken ct)
    {
        try
        {
            var routes = ComputeFrames(from, env);
            foreach (var (target, frame, noStock) in routes)
            {
                await target.PushAsync(frame, noStock, ct);
            }
        }
        catch (Exception ex)
        {
            _log.LogError(ex, "BattleSession {Bid}: unhandled in HandleFrameAsync", BattleId);
        }
    }

    /// <summary>
    /// Pure-logic dispatch: given an inbound frame from one participant, return the list
    /// of (target, frame, noStock) tuples the session should dispatch. Transitions
    /// <see cref="Phase"/>. Extracted so unit tests can drive the dispatch without
    /// standing up real participants.
    /// </summary>
    internal IReadOnlyList<DispatchRoute> ComputeFrames(
        IBattleParticipant from, MsgEnvelope env)
    {
        if (Handlers.TryGetValue(env.Uri, out var handler))
            return handler.Handle(BuildContext(from, env));

        // --- legacy switch (shrinking; deleted in the final task) ---
        var result = new List<DispatchRoute>();
        var other = ReferenceEquals(from, A) ? B : A;
        var phaseFrom = from as IHasHandshakePhase;

        // The dispatch table only covers the Scripted-mode behaviour Phase 1 needs;
        // Phase 2 (Pvp) and Phase 3 (Bot) add the other-type branches. Handshake-phase
        // arms read the SENDER's Phase (per-participant); the session-level Phase
        // remains only for the Terminal short-circuit.
        switch (env.Uri)
        {
            case NetworkBattleUri.InitNetwork when phaseFrom?.Phase == BattleSessionPhase.AwaitingInitNetwork:
                result.Add(new DispatchRoute(from, BattleFrames.BuildAck(NetworkBattleUri.InitNetwork), true));
                phaseFrom!.Phase = BattleSessionPhase.AwaitingInitBattle;
                break;

            // --- Phase 3 Bot arms — placed BEFORE the existing handshake arms so they
            // win pattern matching on Type == Bot. Bot mode: ack handshake, silent
            // Loaded, Judge-to-sender on TurnEnd. The rest reuse Scripted's arms
            // (Retire/Kill → BattleFinishNoContest, Swap → per-sender response,
            // default → drop). Reference: docs/api-spec/in-battle/ai-passive.md.
            //
            // Critically, do NOT push Matched or BattleStart for Bot mode. The
            // architecture spec was right about this:
            //   1. The client's MatchingInitBattle (Matching.cs:298) immediately calls
            //      StartBattleLoad + GotoBattle on the IsAINetwork branch right after
            //      emitting InitBattle — it does NOT wait for a wire Matched or
            //      BattleStart envelope. The state-machine trigger is _initNetworkSuccess
            //      (set when InitNetwork uri is received, i.e., our ack).
            //   2. Sending Matched is harmless (gated on status == Connect, which is
            //      already past by the time the wire round-trip completes).
            //   3. Sending BattleStart is ACTIVELY HARMFUL: its handler at
            //      Matching.cs:417 runs unconditionally and SetNetworkInfo
            //      (RealTimeNetworkAgent.cs:1553-1564) overwrites OppoBattleStartInfo
            //      with the wire envelope's oppoInfo. Our oppoInfo comes from
            //      NoOpBotParticipant.Context placeholders (classId:0, emblemId:0,
            //      etc.), corrupting the good values the client just set from the
            //      HTTP /ai_<fmt>_rank_battle/start response — subsequent asset
            //      loads (LoadOpponentAssets at SBattleLoad.cs:933) then look up
            //      non-existent assets and silently hang on "Waiting for opponent."

            case NetworkBattleUri.InitBattle
                when Type == BattleType.Bot && phaseFrom?.Phase == BattleSessionPhase.AwaitingInitBattle:
                // Ack only — NO Matched push.
                result.Add(new DispatchRoute(from, BattleFrames.BuildAck(NetworkBattleUri.InitBattle), true));
                phaseFrom!.Phase = BattleSessionPhase.AwaitingLoaded;
                break;

            case NetworkBattleUri.Loaded
                when Type == BattleType.Bot && phaseFrom?.Phase == BattleSessionPhase.AwaitingLoaded:
                // Silent — no BattleStart, no Deal. The client's AINetworkBattleManager
                // populates opponent state from AIBattleStart HTTP data; pushing
                // BattleStart here overwrites that state with zeros.
                phaseFrom!.Phase = BattleSessionPhase.AwaitingSwap;
                break;

            case NetworkBattleUri.TurnEnd
                when Type == BattleType.Bot && phaseFrom?.Phase == BattleSessionPhase.AfterReady:
            case NetworkBattleUri.TurnEndFinal
                when Type == BattleType.Bot && phaseFrom?.Phase == BattleSessionPhase.AfterReady:
                // Judge to sender ONLY (not broadcast — there's no real other side).
                // The client's JudgeOperation → ControlTurnStartPlayer flips back to
                // the local AI's turn after this Judge arrives.
                result.Add(new DispatchRoute(from, BattleFrames.BuildJudgeBroadcast(), false));
                break;

            case NetworkBattleUri.InitBattle when phaseFrom?.Phase == BattleSessionPhase.AwaitingInitBattle:
                // Phase 1: push Matched only to the "real" participant. The session reads
                // selfInfo from from.Context and oppoInfo from other.Context (the scripted
                // bot's Context fixture preserves the prod-captured cosmetics that previously
                // lived in ScriptedProfiles).
                result.Add(new DispatchRoute(from, ScriptedLifecycle.BuildMatched(
                    from.Context, other.Context,
                    from.ViewerId, other.ViewerId,
                    BattleId, ScriptedProfiles.BattleSeed), false));
                phaseFrom!.Phase = BattleSessionPhase.AwaitingLoaded;
                break;

            case NetworkBattleUri.Loaded when phaseFrom?.Phase == BattleSessionPhase.AwaitingLoaded:
            {
                // Exactly one side goes first. A goes first deterministically: in Scripted that's
                // the real player (constructed as A); in PvP that's the first arriver. No Type
                // check — the rule is correct in both modes, and Bot/AINetwork never reaches this
                // arm (its silent Loaded arm above wins the match). A per-battle coin-flip is a
                // follow-up (see plan § Out of scope).
                var turnState = ReferenceEquals(from, A) ? 0 : 1;
                result.Add(new DispatchRoute(from, ScriptedLifecycle.BuildBattleStart(
                    from.Context, other.Context, from.ViewerId, turnState), false));
                result.Add(new DispatchRoute(from, ScriptedLifecycle.BuildDeal(), false));
                phaseFrom!.Phase = BattleSessionPhase.AwaitingSwap;
                break;
            }

            case NetworkBattleUri.Swap when phaseFrom?.Phase == BattleSessionPhase.AwaitingSwap:
            {
                var hand = ScriptedLifecycle.ComputeHandAfterSwap(BattleFrames.ExtractIdxList(env));
                // SwapResponse is always immediate — it completes the sender's own mulligan UI.
                result.Add(new DispatchRoute(from, ScriptedLifecycle.BuildSwapResponse(hand), false));
                _state.PostSwapHands[from] = hand;
                phaseFrom!.Phase = BattleSessionPhase.AfterReady;

                // Release Ready to every swapper once all handshake-driving participants have
                // swapped. IHasHandshakePhase membership IS the "participates in mulligan" set:
                //   PvP        → {A, B}            (both reals)            → waits for both
                //   Scripted   → {player, bot}     (bot now emits Swap)    → waits for both
                //   Bot/AINet  → {real} only       (NoOp isn't a phase impl)→ releases on the one Swap
                var swappers = new[] { A, B }.Where(p => p is IHasHandshakePhase).ToList();
                if (swappers.All(_state.PostSwapHands.ContainsKey))
                {
                    foreach (var p in swappers)
                    {
                        var opponent = ReferenceEquals(p, A) ? B : A;
                        var ready = opponent is IHasHandshakePhase && _state.PostSwapHands.TryGetValue(opponent, out var oppoHand)
                            ? ScriptedLifecycle.BuildReady(_state.PostSwapHands[p], oppoHand)   // both hands known
                            : ScriptedLifecycle.BuildReady(_state.PostSwapHands[p]);            // non-interactive opponent
                        result.Add(new DispatchRoute(p, ready, false));
                    }
                }
                break;
            }

            // Regular TurnEnd: continues the game. Scripted forwards to bot for the 3-frame
            // burst; PvP broadcasts; Bot stays silent.
            case NetworkBattleUri.TurnEnd when phaseFrom?.Phase == BattleSessionPhase.AfterReady:
                if (Type == BattleType.Pvp && BothAfterReady())
                {
                    var turnEndBroadcast = BattleFrames.BuildTurnEndBroadcast();
                    var judgeBroadcast = BattleFrames.BuildJudgeBroadcast();
                    result.Add(new DispatchRoute(from, turnEndBroadcast, false));
                    result.Add(new DispatchRoute(other, turnEndBroadcast, false));
                    result.Add(new DispatchRoute(from, judgeBroadcast, false));
                    result.Add(new DispatchRoute(other, judgeBroadcast, false));
                }
                else if (Type == BattleType.Scripted)
                {
                    result.Add(new DispatchRoute(other, env, false));
                }
                // Bot type: no-op (NoOpBot swallows; client handles its own turn end).
                break;

            // TurnEndFinal: client signals the player's FINAL turn is over (game-end
            // condition met, usually killed opponent's leader). Unified across types:
            // forward the envelope to other (matches prod TK2 capture
            // battle-traffic_tk2_regular.ndjson:273 — loser-side receives TurnEndFinal
            // from server before BattleFinish), then push BattleFinish per-side with
            // player-perspective codes (LifeWin to winner, LifeLose to loser).
            // ScriptedBotParticipant no longer reacts to TurnEndFinal (only TurnEnd) —
            // this dispatch arm owns it. NoOpBotParticipant swallows. Phase → Terminal
            // so the RunAsync cascade doesn't synthesize a follow-up BattleFinish.
            case NetworkBattleUri.TurnEndFinal when phaseFrom?.Phase == BattleSessionPhase.AfterReady:
                result.Add(new DispatchRoute(other, env, false));
                result.Add(new DispatchRoute(from, BattleFrames.BuildBattleFinish(BattleResult.LifeWin), true));
                result.Add(new DispatchRoute(other, BattleFrames.BuildBattleFinish(BattleResult.LifeLose), true));
                _state.SessionPhase = BattleSessionPhase.Terminal;
                break;

            // Retire / Kill: sender concedes (Retire) or the client requested an immediate
            // terminate (Kill). Unified across types: push BattleFinish per-side with the
            // proper retire codes. Bots swallow their push (no real-opponent state).
            case NetworkBattleUri.Retire:
            case NetworkBattleUri.Kill:
                result.Add(new DispatchRoute(from, BattleFrames.BuildBattleFinish(BattleResult.RetireLose), true));
                result.Add(new DispatchRoute(other, BattleFrames.BuildBattleFinish(BattleResult.RetireWin), true));
                _state.SessionPhase = BattleSessionPhase.Terminal;
                break;

            // Frames emitted by the scripted bot (TurnStart / TurnEnd / Judge) — forward
            // to the real participant. These match the v1.2 burst's three outbound pushes.
            // Pre-migration this arm only handled TurnStart/Judge because the handshake
            // TurnEnd arm above (gated on session-level Phase) also caught the bot's TurnEnd.
            // Post-migration that arm gates on the sender's per-participant Phase, which the
            // bot doesn't have, so the bot's TurnEnd now lands here.
            // The `IsRealForwardableFromScripted` guard ensures this arm matches ONLY the
            // scripted bot's emissions (sender ViewerId == FakeOpponentViewerId) — without
            // it, a TurnStart/TurnEnd/Judge from a real participant in PvP mode would match
            // here and `goto default` would skip the PvP forwarder arm below.
            case NetworkBattleUri.TurnStart when IsRealForwardableFromScripted(from, env):
            case NetworkBattleUri.TurnEnd when IsRealForwardableFromScripted(from, env):
            case NetworkBattleUri.Judge when IsRealForwardableFromScripted(from, env):
                // Generic forwarder for scripted-bot emissions. The Scripted bot's TurnStart,
                // TurnEnd, and Judge are intended for the real participant.
                result.Add(new DispatchRoute(other, env, false));
                break;

            // Gameplay-frame forwarding (post-AfterReady). Unified across types:
            // BothAfterReady() is only true when both participants are RealParticipants
            // (ScriptedBot/NoOpBot don't implement IHasHandshakePhase so their Phase is
            // always null), so this arm naturally fires for PvP only. Order matters:
            // this MUST come after the FakeOpponentViewerId arms so Scripted bot
            // emissions don't fall into this forwarder.
            case NetworkBattleUri.TurnStart when BothAfterReady():
            case NetworkBattleUri.PlayActions when BothAfterReady():
            case NetworkBattleUri.Echo when BothAfterReady():
            case NetworkBattleUri.TurnEndActions when BothAfterReady():
            case NetworkBattleUri.JudgeResult when BothAfterReady():
                result.Add(new DispatchRoute(other, env, false));
                break;

            default:
                _log.LogDebug("BattleSession {Bid}: dropping uri={Uri} in phase={Phase} from vid={Vid}",
                    BattleId, env.Uri, Phase, from.ViewerId);
                break;
        }

        return result;
    }

    // Phase 1: the only "scripted-bot" emissions we need to forward are the three burst
    // frames (TurnStart, TurnEnd, Judge) — and TurnEnd is already handled in the switch
    // above as a forwardable bot emission. This helper exists so the TurnStart/Judge cases
    // above only fire when the source is actually a participant (not malformed inbound).
    private static bool IsRealForwardableFromScripted(IBattleParticipant from, MsgEnvelope env)
    {
        // The bot's emitted frames carry ViewerId == FakeOpponentViewerId.
        return from.ViewerId == ScriptedLifecycle.FakeOpponentViewerId;
    }

    // Phase 2: PvP gameplay-frame forwarding is gated on BOTH sides having completed
    // the handshake (i.e. reached AfterReady). Until then, an early TurnStart/PlayActions
    // from one side has no valid recipient.
    private bool BothAfterReady() =>
        (A as IHasHandshakePhase)?.Phase == BattleSessionPhase.AfterReady &&
        (B as IHasHandshakePhase)?.Phase == BattleSessionPhase.AfterReady;

}