#if UNITY_EDITOR
  /**
   * AreaEditor
   *
   * Custom editor for Area scriptable object representing area of effect (for abilities and other effects).
   */
  [CustomEditor(typeof(Area))]
  public class AreaEditor : UnityEditor.Editor {

    private VisualElement _root;
    private PropertyField _needsLOSField;
    private PropertyField _areaSizeField;
    // private PropertyField affectedTilesField;
    private VisualElement _areaMatrix;

    private void OnEnable() {
      Undo.undoRedoPerformed += this.OnUndoRedo;
    }

    private void OnDisable() {
      Undo.undoRedoPerformed -= this.OnUndoRedo;
    }

    public override VisualElement CreateInspectorGUI() {
      this._root = new VisualElement();

      // needsLOS property
      this._needsLOSField = new PropertyField(this.serializedObject.FindProperty("_needsLOS"));
      this._needsLOSField.label = "Needs line of sight";
      this._root.Add(this._needsLOSField);

      // area size
      this._areaSizeField = new PropertyField(this.serializedObject.FindProperty("_areaSize"));
      this._areaSizeField.label = "Area size";
      this._areaSizeField.RegisterValueChangeCallback((evt) => {
        this._areaMatrix.Clear();
        this._areaMatrix.Add(this.CreateAreaMatrix());
      });
      this._root.Add(this._areaSizeField);

      // create a matrix of buttons for editing affected tiles
      this._areaMatrix = new VisualElement();
      this._areaMatrix.Add(this.CreateAreaMatrix());
      this._root.Add(this._areaMatrix);

      return this._root;
    }

    private VisualElement CreateAreaMatrix() {
      VisualElement matrix = new VisualElement();
      matrix.style.flexDirection = FlexDirection.Row;
      matrix.style.flexWrap = Wrap.Wrap;

      Foldout foldout = new Foldout();
      foldout.text = "Affected tiles";
      foldout.Q<VisualElement>("unity-content").style.marginLeft = 3;
      foldout.Add(matrix);

      Area area = (Area) this.target;
      Vector2Int areaSize = area.areaSize;
      Vector2Int centerSize = new Vector2Int(areaSize.x / 2, areaSize.y / 2);

      Color activeColor = Color.green;
      Color centerColor = Color.blue;

      VisualElement row;

      for (int x = 0; x < areaSize.x; ++x) {
        // create new row
        row = new VisualElement();
        matrix.Add(row);

        for (int y = 0; y < areaSize.y; ++y) {
          int aX = x;
          int aY = y;

          // for every column, create new button
          Button button = new Button();
          button.style.width = 20;
          button.style.height = 20;
          button.style.marginBottom = 0;
          button.style.marginRight = 0;
          button.style.marginTop = 0;
          button.style.marginLeft = 0;
          button.RegisterCallback<ClickEvent>((evt) => {
            // skip if its center tile
            if (new Vector2Int(aX, aY) == centerSize) {
              return;
            }

            this.HandleButtonPress(aX, aY, area);
          });

          // if its center tile then always mark it as active
          if (x == centerSize.x && y == centerSize.y) {
            button.style.backgroundColor = centerColor;
          } else {
            // check if this tile is in affected tiles
            Vector3Int tile = new Vector3Int(x - centerSize.x, 0, y - centerSize.y);
            if (area.affectedTiles != null && area.affectedTiles.Contains(tile)) {
              button.style.backgroundColor = activeColor;
            }
          }

          row.Add(button);
        }

      }

      return foldout;
    }

    private void HandleButtonPress(int aX, int aY, Area area) {
      Vector2Int areaSize = area.areaSize;
      Vector2Int centerSize = new Vector2Int(areaSize.x / 2, areaSize.y / 2);
      Vector3Int tile = new Vector3Int(aX - centerSize.x, 0, aY - centerSize.y);

      List<Vector3Int> affectedTiles = area.affectedTiles.ToList();
      if (affectedTiles.Contains(tile)) {
        affectedTiles.Remove(tile);
      } else {
        affectedTiles.Add(tile);
      }

      Undo.RecordObject(area, "Change affected tiles");
      area.SetAffectedTiles(affectedTiles);
      EditorUtility.SetDirty(area);

      this._areaMatrix.Clear();
      this._areaMatrix.Add(this.CreateAreaMatrix());

      this.serializedObject.Update();
    }

    private void OnUndoRedo() {
      this._areaMatrix.Clear();
      this._areaMatrix.Add(this.CreateAreaMatrix());
    }

  }
 #endif