/******************************************************************************
 * Copyright (C) Ultraleap, Inc. 2011-2021.                                   *
 *                                                                            *
 * Use subject to the terms of the Apache License 2.0 available at            *
 * http://www.apache.org/licenses/LICENSE-2.0, or another agreement           *
 * between Ultraleap and you, your company or other organization.             *
 ******************************************************************************/

using Leap.Unity.Query;
using System;
using System.Collections.Generic;
using System.Reflection;
using UnityEditor;
using UnityEngine;
using UnityEngine.SceneManagement;

namespace Leap.Unity
{

    using UnityObject = UnityEngine.Object;

    public static class EditorUtils
    {

        private class SceneReference<T> where T : UnityObject
        {
            SerializedObject objectContainingReference;
            SerializedProperty reference;
        }

        /// <summary>
        /// Scans the currently-open scene for references of a and replaces them with b.
        /// These swaps are performed with Undo.RecordObject before an object's references
        /// are changed, so they can be undone.
        /// </summary>
        public static void ReplaceSceneReferences<T>(T a, T b) where T : UnityObject
        {
            var aId = a.GetInstanceID();
            var refType = typeof(T);

            var curScene = SceneManager.GetActiveScene();
            var rootObjs = curScene.GetRootGameObjects();
            foreach (var rootObj in rootObjs)
            {
                var transforms = rootObj.GetComponentsInChildren<Transform>();
                foreach (var transform in transforms)
                {
                    var components = transform.GetComponents<Component>();

                    var objectChanges = new List<Action>();
                    foreach (var component in components)
                    {
                        var compType = typeof(Component);
                        var fieldInfos = compType.GetFields(BindingFlags.Instance
                          | BindingFlags.FlattenHierarchy | BindingFlags.NonPublic
                          | BindingFlags.Public);
                        foreach (var fieldInfo in fieldInfos.Query()
                          .Where(fi => fi.FieldType.IsAssignableFrom(refType)))
                        {
                            var refValue = fieldInfo.GetValue(component) as T;
                            if (refValue.GetInstanceID() == aId)
                            {
                                objectChanges.Add(() =>
                                {
                                    fieldInfo.SetValue(fieldInfo, b);
                                });
                            }
                        }
                    }
                    if (objectChanges.Count > 0)
                    {
                        Undo.RecordObject(transform.gameObject,
                          "Swap " + transform.name + " references from " + a.name + " to " + b.name);
                        foreach (var change in objectChanges)
                        {
                            change();
                        }
                    }
                }
            }
        }

    }

}