Handle authenticated room instance takeover

app/Services/Rooms/RoomParticipationService.php

@@ -205,6 +205,17 @@ class RoomParticipationService
         ?User $user,
         mixed $sessionPlayerId,
     ): ?Player {
+        if ($user !== null) {
+            $userPlayer = $room->players()
+                ->where('user_id', $user->id)
+                ->lockForUpdate()
+                ->first();
+
+            if ($userPlayer !== null) {
+                return $userPlayer;
+            }
+        }
+
         if (is_numeric($sessionPlayerId)) {
             $sessionPlayer = $room->players()
                 ->whereKey((int) $sessionPlayerId)
@@ -216,14 +227,53 @@ class RoomParticipationService
             }
         }
 
-        if ($user === null) {
-            return null;
+        return null;
+    }
+
+    public function activateInstance(Room $room, Player $player, string $instanceId): Player
+    {
+        [$activePlayer, $replacedInstanceId, $stateVersion] = DB::transaction(function () use ($room, $player, $instanceId): array {
+            $lockedRoom = Room::query()
+                ->lockForUpdate()
+                ->findOrFail($room->id);
+            $lockedPlayer = $lockedRoom->players()
+                ->lockForUpdate()
+                ->findOrFail($player->id);
+
+            if ($lockedPlayer->active_instance_id === $instanceId) {
+                return [$lockedPlayer, null, null];
+            }
+
+            $replacedInstanceId = $lockedPlayer->active_instance_id;
+            $lockedPlayer->update([
+                'active_instance_id' => $instanceId,
+                'last_seen_at' => now(),
+            ]);
+
+            if ($replacedInstanceId === null) {
+                return [$lockedPlayer, null, null];
+            }
+
+            $lockedRoom->update([
+                'last_activity_at' => now(),
+                'state_version' => $lockedRoom->state_version + 1,
+            ]);
+
+            return [$lockedPlayer, $replacedInstanceId, $lockedRoom->state_version];
+        });
+
+        if (is_string($replacedInstanceId) && is_int($stateVersion)) {
+            RoomStateChanged::dispatch(
+                $room->id,
+                $stateVersion,
+                RoomStateChange::PlayerInstanceReplaced,
+                $this->realtimeState->for($room),
+                $activePlayer->id,
+                $replacedInstanceId,
+            );
         }
 
-        return $room->players()
-            ->where('user_id', $user->id)
-            ->lockForUpdate()
-            ->first();
+        return $activePlayer;
     }
 
     public function kick(

app/Services/Rooms/RoomPlayerInstanceService.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Services\Rooms;
+
+use Illuminate\Http\Request;
+use Illuminate\Support\Str;
+
+class RoomPlayerInstanceService
+{
+    private const string SESSION_KEY = 'room_player_instance_id';
+
+    public function for(Request $request): string
+    {
+        $instanceId = $request->session()->get(self::SESSION_KEY);
+
+        if (is_string($instanceId) && Str::isUuid($instanceId)) {
+            return $instanceId;
+        }
+
+        $instanceId = (string) Str::uuid();
+        $request->session()->put(self::SESSION_KEY, $instanceId);
+
+        return $instanceId;
+    }
+}