using Microsoft.Extensions.Logging;
using SVSim.BattleNode.Lifecycle;
using SVSim.BattleNode.Protocol;
using SVSim.BattleNode.Protocol.Bodies;
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;

    public string BattleId { get; }
    public BattleType Type { get; }
    public IBattleParticipant A { get; }
    public IBattleParticipant B { get; }
    public BattleSessionPhase Phase { get; private set; } = BattleSessionPhase.AwaitingInitNetwork;

    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)
    {
        // Run both participants' inbound loops in parallel and wait for them all to
        // complete. NoOp/Scripted bots return immediately; Real returns when the WS
        // closes. Using WhenAny here would have killed the session as soon as the
        // scripted bot's no-op RunAsync resolved. Phase 2's Pvp/Bot cases will need
        // disconnect propagation; that's wired in their own task.
        var aTask = A.RunAsync(cancellation);
        var bTask = B.RunAsync(cancellation);
        try { await Task.WhenAll(aTask, bTask); } catch { /* swallow cancellation */ }

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

    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<(IBattleParticipant Target, MsgEnvelope Frame, bool NoStock)> ComputeFrames(
        IBattleParticipant from, MsgEnvelope env)
    {
        var result = new List<(IBattleParticipant, MsgEnvelope, bool)>();
        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((from, BuildAck(NetworkBattleUri.InitNetwork), true));
                phaseFrom!.Phase = BattleSessionPhase.AwaitingInitBattle;
                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((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:
                result.Add((from, ScriptedLifecycle.BuildBattleStart(
                    from.Context, other.Context, from.ViewerId), false));
                result.Add((from, ScriptedLifecycle.BuildDeal(), false));
                phaseFrom!.Phase = BattleSessionPhase.AwaitingSwap;
                break;

            case NetworkBattleUri.Swap when phaseFrom?.Phase == BattleSessionPhase.AwaitingSwap:
            {
                var hand = ScriptedLifecycle.ComputeHandAfterSwap(ExtractIdxList(env));
                result.Add((from, ScriptedLifecycle.BuildSwapResponse(hand), false));
                result.Add((from, ScriptedLifecycle.BuildReady(hand), false));
                phaseFrom!.Phase = BattleSessionPhase.AfterReady;
                break;
            }

            case NetworkBattleUri.TurnEnd when phaseFrom?.Phase == BattleSessionPhase.AfterReady:
            case NetworkBattleUri.TurnEndFinal when phaseFrom?.Phase == BattleSessionPhase.AfterReady:
                // Phase 1: forward the player's TurnEnd to the scripted bot. The bot's
                // PushAsync fires its three-frame burst via FrameEmitted; each emitted
                // frame loops back through HandleFrameAsync → ComputeFrames → routes to
                // the real participant. Net wire effect: same three pushes as v1.2.
                result.Add((other, env, false));
                break;

            case NetworkBattleUri.Retire:
            case NetworkBattleUri.Kill:
                result.Add((from, BuildBattleFinishNoContest(), true));
                Phase = 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.
            case NetworkBattleUri.TurnStart when ReferenceEquals(from, B) || ReferenceEquals(from, A):
            case NetworkBattleUri.TurnEnd when ReferenceEquals(from, B) || ReferenceEquals(from, A):
            case NetworkBattleUri.Judge when ReferenceEquals(from, B) || ReferenceEquals(from, A):
                // Generic forwarder for scripted-bot emissions. The Scripted bot's TurnStart,
                // TurnEnd, and Judge are intended for the real participant.
                if (!IsRealForwardableFromScripted(from, env)) goto default;
                result.Add((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;
    }

    private MsgEnvelope BuildAck(NetworkBattleUri uri) => new(
        uri,
        ViewerId: ScriptedLifecycle.FakeOpponentViewerId,
        Uuid: WireConstants.ServerUuid,
        Bid: null,
        Try: 0,
        Cat: EmitCategory.General,
        PubSeq: null,
        PlaySeq: null,
        Body: new ResultCodeOnlyBody());

    private MsgEnvelope BuildBattleFinishNoContest() => new(
        NetworkBattleUri.BattleFinish,
        ViewerId: ScriptedLifecycle.FakeOpponentViewerId,
        Uuid: WireConstants.ServerUuid,
        Bid: null,
        Try: 0,
        Cat: EmitCategory.Battle,
        PubSeq: null,
        PlaySeq: null,
        Body: new BattleFinishBody(Result: BattleResult.Win));

    private static IReadOnlyList<long> ExtractIdxList(MsgEnvelope env)
    {
        if (env.Body is not RawBody rawBody) return Array.Empty<long>();
        if (rawBody.Entries.TryGetValue("idxList", out var raw) && raw is System.Collections.IEnumerable seq && raw is not string)
        {
            var result = new List<long>();
            foreach (var item in seq)
            {
                switch (item)
                {
                    case long l: result.Add(l); break;
                    case int i: result.Add(i); break;
                    case double d: result.Add((long)d); break;
                    case decimal m: result.Add((long)m); break;
                    case string s when long.TryParse(s, out var p): result.Add(p); break;
                }
            }
            return result;
        }
        return Array.Empty<long>();
    }
}