From ef9afedf42f4ca6539f8feae5670f52fcb1c48df Mon Sep 17 00:00:00 2001
From: Joonas Rikkonen <poe.regalis@gmail.com>
Date: Thu, 18 Oct 2018 00:18:57 +0300
Subject: [PATCH] Added a level equality check to client error handling to make
 it easier to diagnose bugs like #848 in the future.

---
 .../Source/Networking/GameClient.cs              |  3 ++-
 .../BarotraumaShared/Source/Map/Levels/Level.cs  | 13 +++++++++++++
 .../Source/Networking/GameServer.cs              | 16 +++++++++++-----
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/Barotrauma/BarotraumaClient/Source/Networking/GameClient.cs b/Barotrauma/BarotraumaClient/Source/Networking/GameClient.cs
index 08897f112..541c878df 100644
--- a/Barotrauma/BarotraumaClient/Source/Networking/GameClient.cs
+++ b/Barotrauma/BarotraumaClient/Source/Networking/GameClient.cs
@@ -1647,11 +1647,12 @@ namespace Barotrauma.Networking
             return false;
         }
 
-        public void ReportError(ClientNetError error,UInt16 expectedID=0,UInt16 eventID=0,UInt16 entityID=0)
+        public void ReportError(ClientNetError error, UInt16 expectedID = 0, UInt16 eventID = 0, UInt16 entityID = 0)
         {
             NetOutgoingMessage outMsg = client.CreateMessage();
             outMsg.Write((byte)ClientPacketHeader.ERROR);
             outMsg.Write((byte)error);
+            outMsg.Write(Level.Loaded == null ? 0 : Level.Loaded.EqualityCheckVal);
             switch (error)
             {
                 case ClientNetError.MISSING_EVENT:
diff --git a/Barotrauma/BarotraumaShared/Source/Map/Levels/Level.cs b/Barotrauma/BarotraumaShared/Source/Map/Levels/Level.cs
index ec25608db..419bab0b6 100644
--- a/Barotrauma/BarotraumaShared/Source/Map/Levels/Level.cs
+++ b/Barotrauma/BarotraumaShared/Source/Map/Levels/Level.cs
@@ -128,6 +128,16 @@ namespace Barotrauma
             get { return seed; }
         }
 
+        /// <summary>
+        /// A random integer assigned at the end of level generation. If these values differ between clients/server,
+        /// it means the levels aren't identical for some reason and there will most likely be major ID mismatches.
+        /// </summary>
+        public int EqualityCheckVal
+        {
+            get;
+            private set;
+        }
+
         public float Difficulty
         {
             get;
@@ -538,6 +548,9 @@ namespace Barotrauma
             GenerateSeaFloor(mirror);
 
             backgroundSpriteManager.PlaceSprites(this, generationParams.BackgroundSpriteAmount);
+
+            EqualityCheckVal = Rand.Int(int.MaxValue, Rand.RandSync.Server);
+
 #if CLIENT
             backgroundCreatureManager.SpawnSprites(80);
 #endif
diff --git a/Barotrauma/BarotraumaShared/Source/Networking/GameServer.cs b/Barotrauma/BarotraumaShared/Source/Networking/GameServer.cs
index 0989ffc84..e1d2b39f7 100644
--- a/Barotrauma/BarotraumaShared/Source/Networking/GameServer.cs
+++ b/Barotrauma/BarotraumaShared/Source/Networking/GameServer.cs
@@ -618,6 +618,7 @@ namespace Barotrauma.Networking
             string errorStr = "Unhandled error report";
 
             ClientNetError error = (ClientNetError)inc.ReadByte();
+            int levelEqualityCheckVal = inc.ReadInt32();
             switch (error)
             {
                 case ClientNetError.MISSING_EVENT:
@@ -631,30 +632,35 @@ namespace Barotrauma.Networking
                     Entity entity = Entity.FindEntityByID(entityID);
                     if (entity == null)
                     {
-                        errorStr = "Received an update for an entity that doesn't exist (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ")";
+                        errorStr = "Received an update for an entity that doesn't exist (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ").";
                     }
                     else if (entity is Character character)
                     {
-                        errorStr = "Missing character " + character.Name + " (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ")";
+                        errorStr = "Missing character " + character.Name + " (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ").";
                     }
                     else if (entity is Item item)
                     {
-                        errorStr = "Missing item " + item.Name + " (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ")";
+                        errorStr = "Missing item " + item.Name + " (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ").";
                     }
                     else
                     {
-                        errorStr = "Missing entity " + entity.ToString() + " (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ")";
+                        errorStr = "Missing entity " + entity.ToString() + " (event id " + eventID.ToString() + ", entity id " + entityID.ToString() + ").";
                     }
                     break;
             }
 
+            if (Level.Loaded != null && levelEqualityCheckVal != Level.Loaded.EqualityCheckVal)
+            {
+                errorStr += " Level equality check failed, something went wrong during level generation (seed " + Level.Loaded.Seed + ").";
+            }
+
             if (c == null)
             {
                 KickClient(inc.SenderConnection, errorStr);
             }
             else
             {
-				GameServer.Log(c.Name + " has reported an error: " + errorStr, ServerLog.MessageType.Error);
+				Log(c.Name + " has reported an error: " + errorStr, ServerLog.MessageType.Error);
 				KickClient(c, errorStr);
             }
         }