#if UNITY_EDITOR

using System.Collections.Generic;
using UnityEditor;
using UnityEngine;

/// <summary>
/// UnityAssetHistory Ver 1.0.0
/// Copyright (c) 2025 MMGames
/// Released under the MIT License.
/// https://9cguide.appspot.com/unity_unity_asset_history.html
/// </summary>
public class UnityAssetHistory : EditorWindow
{
    /// <summary>
    /// History of the selected asset (Note: Variable names may have changed)
    /// </summary>
    [SerializeField]
    private List<Object> selectedAssetHistoryList = new();

    /// <summary>
    /// Current scroll position
    /// </summary>
    private Vector2 scrollPosition;

    /// <summary>
    /// Targets only assets (ignores folders and objects within scenes)
    /// </summary>
    private bool IsAssetOlly = false;

    /// <summary>
    /// Add to the Unity Editor menu
    /// </summary>
    [MenuItem("Tools/UnityAssetHistory")]
    private static void RegisterMenu()
    {
        GetWindow<UnityAssetHistory>();
    }

    /// <summary>
    /// Enable
    /// </summary>
    private void OnEnable()
    {
        // Asset Selection Event

        Selection.selectionChanged += OnSelectionChanged;
    }

    /// <summary>
    /// Redraw
    /// </summary>
    private void OnGUI()
    {
        // Convert to a SerializedObject

        var serializedObject = new SerializedObject(this);
        serializedObject.Update();

        // View the history of the selected asset

        scrollPosition = EditorGUILayout.BeginScrollView(scrollPosition);

        EditorGUILayout.PropertyField(serializedObject.FindProperty("selectedAssetHistoryList"), true);

        EditorGUILayout.EndScrollView();

        EditorGUILayout.Space();

        // Clear button

        if (GUILayout.Button("Clean"))
        {
            OnClickCleanButton();
        }
    }

    /// <summary>
    /// An asset has been selected
    /// </summary>
    private void OnSelectionChanged()
    {
        bool isRepaint = false;

        // Get the selected object

        var selectedObjectList = Selection.objects;

        foreach (Object obj in selectedObjectList)
        {
            // If it's not an asset, ignore it

            if (IsAssetOlly)
            {
                if (IsAsset(obj) == false) return;
            }

            // Does it already exist in the history?

            var selectedAssetHistoryIndex = selectedAssetHistoryList.IndexOf(obj);

            if (selectedAssetHistoryIndex >= 0)
            {
                // If it exists, delete it (since it will be added to the beginning, it will move to the top)

                selectedAssetHistoryList.Remove(obj);
            }

            // Redraw flag ON

            isRepaint = true;

            // Add to the front

            selectedAssetHistoryList.Insert(0, obj);
        }

        // If there are any assets that can no longer be accessed, please delete them.

        if (GCAll()) isRepaint = true;

        // Redraw

        if (isRepaint) Repaint();
    }

    /// <summary>
    /// The Clean button was clicked
    /// </summary>
    private void OnClickCleanButton()
    {
        // If there's no history, I won't do anything

        if (selectedAssetHistoryList.Count == 0) return;

        // Clear and redraw

        selectedAssetHistoryList = new();
        Repaint();
    }

    /// <summary>
    /// Remove all inaccessible assets from the history
    /// </summary>
    /// <returns></returns>
    private bool GCAll()
    {
        // If there are none, no need to redraw

        if (GCSingle() == false) return false;

        // Repeat the deletion process as long as there are assets that can no longer be accessed

        while (GCSingle())
        {
        }

        return true;
    }

    /// <summary>
    /// Delete just one inaccessible asset from the history
    /// </summary>
    /// <returns></returns>
    private bool GCSingle()
    {
        // Find assets that can no longer be accessed

        for (int i = 0; i < selectedAssetHistoryList.Count; i++)
        {
            if (selectedAssetHistoryList[i] == null)
            {
                // If found, delete and return

                selectedAssetHistoryList.RemoveAt(i);
                return true;
            }
        }

        // Not a single one

        return false;
    }

    /// <summary>
    /// Is the specified object an asset?
    /// </summary>
    /// <param name="inObject"></param>
    /// <returns></returns>
    private bool IsAsset(Object inObject)
    {
        string assetPath = AssetDatabase.GetAssetPath(inObject);
        return (assetPath.Length > 0);
    }

    /// <summary>
    /// Release
    /// </summary>
    private void OnDestroy()
    {
        Selection.selectionChanged -= OnSelectionChanged;
    }
}

#endif