From b089bbca37b3006401b4950f6847d9c38c9c7391 Mon Sep 17 00:00:00 2001
From: ackwell <saxon@ackwell.com.au>
Date: Wed, 17 Jan 2024 23:13:53 +1100
Subject: [PATCH] Merge element ids and flags

---
 .../ModEditWindow.Models.MdlTab.cs            | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs b/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs
index 9cfe0739..841eff4c 100644
--- a/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs
+++ b/Penumbra/UI/AdvancedWindow/ModEditWindow.Models.MdlTab.cs
@@ -1,3 +1,4 @@
+using Lumina.Data.Parsing;
 using OtterGui;
 using Penumbra.GameData;
 using Penumbra.GameData.Files;
@@ -161,6 +162,13 @@ public partial class ModEditWindow
             if (ImportKeepAttributes)
                 MergeAttributes(newMdl, Mdl);
 
+            // Until someone works out how to actually author these, unconditionally merge element ids.
+            MergeElementIds(newMdl, Mdl);
+
+            // TODO: Add flag editing.
+            newMdl.Flags1 = Mdl.Flags1;
+            newMdl.Flags2 = Mdl.Flags2;
+            
             Initialize(newMdl);
             _dirty = true;
         }
@@ -210,6 +218,29 @@ public partial class ModEditWindow
             }
         }
 
+        /// <summary> Merge element ids from the source onto the target. </summary>
+        /// <param name="target"> Model that will be updated. ></param>
+        /// <param name="source"> Model to copy element ids from. </param>
+        private static void MergeElementIds(MdlFile target, MdlFile source)
+        {
+            var elementIds = new List<MdlStructs.ElementIdStruct>();
+
+            foreach (var sourceElement in source.ElementIds)
+            {
+                var sourceBone = source.Bones[sourceElement.ParentBoneName];
+                var targetIndex = target.Bones.IndexOf(sourceBone);
+                // Given that there's no means of authoring these at the moment, this should probably remain a hard error.
+                if (targetIndex == -1)
+                    throw new Exception($"Failed to merge element IDs. Original model contains element IDs targeting bone {sourceBone}, which is not present on the imported model.");
+                elementIds.Add(sourceElement with
+                {
+                    ParentBoneName = (uint)targetIndex,
+                });
+            }
+
+            target.ElementIds = [.. elementIds];
+        }
+
         private void RecordIoExceptions(Exception? exception)
         {
             IoExceptions = exception switch {