Centered Parent Menu

using UnityEngine;
using UnityEditor;

public class CenteredParentMenu
{
    [MenuItem("GameObject/Create Centered Empty Parent", false, 0)]
    static void CreateCenteredEmptyParent(MenuCommand menuCommand)
    {
        // Run the operation only if it's triggered on the first selected object
        if (menuCommand.context != Selection.activeTransform.gameObject)
        {
            return;
        }

        // Get the selected objects in the hierarchy
        GameObject[] selectedObjects = Selection.gameObjects;

        if (selectedObjects.Length == 0)
        {
            Debug.LogWarning("No objects selected. Please select at least one object in the hierarchy.");
            return;
        }

        // Get the parent of the first selected object (assuming all selected objects share the same parent)
        Transform originalParent = selectedObjects[0].transform.parent;

        // Validate that all selected objects share the same parent
        foreach (GameObject go in selectedObjects)
        {
            if (go.transform.parent != originalParent)
            {
                Debug.LogWarning("Cannot select children from different family trees.");
                return;
            }
        }

        // Create the new parent GameObject and register it in the Undo system
        GameObject parentObject = new GameObject("CenteredParent");
        Undo.RegisterCreatedObjectUndo(parentObject, "Create Centered Empty Parent");

        // Calculate the center of all selected objects
        Vector3 center = Vector3.zero;
        foreach (GameObject obj in selectedObjects)
        {
            center += obj.transform.position;
        }
        center /= selectedObjects.Length;

        // Set the new parent object's position to the calculated center
        parentObject.transform.position = center;

        // Set the new parent object under the original parent
        if (originalParent != null)
        {
            Undo.SetTransformParent(parentObject.transform, originalParent, "Reparent Centered Empty");
        }

        // Move all selected objects under the new parent and preserve their world positions
        foreach (GameObject obj in selectedObjects)
        {
            Undo.SetTransformParent(obj.transform, parentObject.transform, "Parent Selected Objects");
        }

        // Ensure that after undo, the objects retain their original positions
        foreach (GameObject obj in selectedObjects)
        {
            Undo.RecordObject(obj.transform, "Move Object");
        }

        // Select the new parent object in the hierarchy
        Selection.activeGameObject = parentObject;
    }
}