refactor(battle-node): move session phase + post-swap hands into BattleSessionState

SVSim.BattleNode/Sessions/BattleSession.cs

@@ -22,19 +22,13 @@ public sealed class BattleSession
 {
     private readonly ILogger<BattleSession> _log;
 
-    // Mulligan barrier: each side's post-mulligan hand, captured on its Swap. Ready is
+    private readonly BattleSessionState _state = new();
-    // withheld until every IHasHandshakePhase participant has swapped (prod withholds it
-    // ~3-6 s — see data_dumps/captures/battle-traffic_tk2_*.ndjson). Keyed on the
-    // IBattleParticipant so the per-side hand is retrievable when releasing both Readys.
-    // NOTE: mutated from ComputeFrames, which is not lock-guarded — same pre-existing
-    // single-threaded-dispatch assumption as the Phase mutations (see plan § Out of scope).
-    private readonly Dictionary<IBattleParticipant, long[]> _postSwapHands = new();
 
     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 BattleSessionPhase Phase => _state.SessionPhase;
 
     public BattleSession(string battleId, BattleType type, IBattleParticipant a, IBattleParticipant b,
         ILogger<BattleSession> log)
@@ -82,7 +76,7 @@ public sealed class BattleSession
                         "BattleSession {Bid}: failed to push BattleFinish to survivor (their WS may also be closed)",
                         BattleId);
                 }
-                Phase = BattleSessionPhase.Terminal;
+                _state.SessionPhase = BattleSessionPhase.Terminal;
             }
 
             cts.Cancel(); // unblock the survivor's RunAsync read loop
@@ -235,7 +229,7 @@ public sealed class BattleSession
                 var hand = ScriptedLifecycle.ComputeHandAfterSwap(ExtractIdxList(env));
                 // SwapResponse is always immediate — it completes the sender's own mulligan UI.
                 result.Add(new DispatchRoute(from, ScriptedLifecycle.BuildSwapResponse(hand), false));
-                _postSwapHands[from] = hand;
+                _state.PostSwapHands[from] = hand;
                 phaseFrom!.Phase = BattleSessionPhase.AfterReady;
 
                 // Release Ready to every swapper once all handshake-driving participants have
@@ -244,14 +238,14 @@ public sealed class BattleSession
                 //   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(_postSwapHands.ContainsKey))
+                if (swappers.All(_state.PostSwapHands.ContainsKey))
                 {
                     foreach (var p in swappers)
                     {
                         var opponent = ReferenceEquals(p, A) ? B : A;
-                        var ready = opponent is IHasHandshakePhase && _postSwapHands.TryGetValue(opponent, out var oppoHand)
+                        var ready = opponent is IHasHandshakePhase && _state.PostSwapHands.TryGetValue(opponent, out var oppoHand)
-                            ? ScriptedLifecycle.BuildReady(_postSwapHands[p], oppoHand)   // both hands known
+                            ? ScriptedLifecycle.BuildReady(_state.PostSwapHands[p], oppoHand)   // both hands known
-                            : ScriptedLifecycle.BuildReady(_postSwapHands[p]);            // non-interactive opponent
+                            : ScriptedLifecycle.BuildReady(_state.PostSwapHands[p]);            // non-interactive opponent
                         result.Add(new DispatchRoute(p, ready, false));
                     }
                 }
@@ -290,7 +284,7 @@ public sealed class BattleSession
                 result.Add(new DispatchRoute(other, env, false));
                 result.Add(new DispatchRoute(from, BuildBattleFinish(BattleResult.LifeWin), true));
                 result.Add(new DispatchRoute(other, BuildBattleFinish(BattleResult.LifeLose), true));
-                Phase = BattleSessionPhase.Terminal;
+                _state.SessionPhase = BattleSessionPhase.Terminal;
                 break;
 
             // Retire / Kill: sender concedes (Retire) or the client requested an immediate
@@ -300,7 +294,7 @@ public sealed class BattleSession
             case NetworkBattleUri.Kill:
                 result.Add(new DispatchRoute(from, BuildBattleFinish(BattleResult.RetireLose), true));
                 result.Add(new DispatchRoute(other, BuildBattleFinish(BattleResult.RetireWin), true));
-                Phase = BattleSessionPhase.Terminal;
+                _state.SessionPhase = BattleSessionPhase.Terminal;
                 break;
 
             // Frames emitted by the scripted bot (TurnStart / TurnEnd / Judge) — forward

SVSim.BattleNode/Sessions/Dispatch/BattleSessionState.cs

@@ -0,0 +1,11 @@
+namespace SVSim.BattleNode.Sessions.Dispatch;
+
+/// <summary>Mutable per-session state shared across frame handlers. Today: the session-level
+/// phase (only ever advanced to <see cref="BattleSessionPhase.Terminal"/>) and the mulligan
+/// barrier's post-swap hands. FUTURE (PvP equivalency, NOT this refactor): per-side idx->cardId
+/// maps + reveal-gating state land here.</summary>
+internal sealed class BattleSessionState
+{
+    public BattleSessionPhase SessionPhase { get; set; } = BattleSessionPhase.AwaitingInitNetwork;
+    public Dictionary<IBattleParticipant, long[]> PostSwapHands { get; } = new();
+}