File: public/js/tinymce/src/plugins/imagetools/src/main/js/core/UndoStack.js

/**
 * UndoStack.js
 *
 * Released under LGPL License.
 * Copyright (c) 1999-2017 Ephox Corp. All rights reserved
 *
 * License: http://www.tinymce.com/license
 * Contributing: http://www.tinymce.com/contributing
 */

define(
  'tinymce.plugins.imagetools.core.UndoStack',
  [
  ],
  function () {
    return function () {
      var data = [], index = -1;

      function add(state) {
        var removed;

        removed = data.splice(++index);
        data.push(state);

        return {
          state: state,
          removed: removed
        };
      }

      function undo() {
        if (canUndo()) {
          return data[--index];
        }
      }

      function redo() {
        if (canRedo()) {
          return data[++index];
        }
      }

      function canUndo() {
        return index > 0;
      }

      function canRedo() {
        return index !== -1 && index < data.length - 1;
      }

      return {
        data: data,
        add: add,
        undo: undo,
        redo: redo,
        canUndo: canUndo,
        canRedo: canRedo
      };
    };
  }
);