/*
 *    Copyright [2015] [wisemapping]
 *
 *   Licensed under WiseMapping Public License, Version 1.0 (the "License").
 *   It is basically the Apache License, Version 2.0 (the "License") plus the
 *   "powered by wisemapping" text requirement on every single page;
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the license at
 *
 *       http://www.wisemapping.org/license
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 */

const DesignerUndoManager = new Class({
  initialize(fireChange) {
    this._undoQueue = [];
    this._redoQueue = [];
    this._baseId = 0;
  },

  enqueue(command) {
    $assert(command, 'Command can  not be null');
    const { length } = this._undoQueue;
    if (command.discardDuplicated && length > 0) {
      // Skip duplicated events ...
      const lastItem = this._undoQueue[length - 1];
      if (lastItem.discardDuplicated != command.discardDuplicated) {
        this._undoQueue.push(command);
      }
    } else {
      this._undoQueue.push(command);
    }
    this._redoQueue = [];
  },

  execUndo(commandContext) {
    if (this._undoQueue.length > 0) {
      const command = this._undoQueue.pop();
      this._redoQueue.push(command);

      command.undoExecute(commandContext);
    }
  },

  execRedo(commandContext) {
    if (this._redoQueue.length > 0) {
      const command = this._redoQueue.pop();
      this._undoQueue.push(command);
      command.execute(commandContext);
    }
  },

  buildEvent() {
    return { undoSteps: this._undoQueue.length, redoSteps: this._redoQueue.length };
  },

  markAsChangeBase() {
    const undoLength = this._undoQueue.length;
    if (undoLength > 0) {
      const command = this._undoQueue[undoLength - 1];
      this._baseId = command.getId();
    } else {
      this._baseId = 0;
    }
  },

  hasBeenChanged() {
    let result = true;
    const undoLength = this._undoQueue.length;
    if (undoLength == 0 && this._baseId == 0) {
      result = false;
    } else if (undoLength > 0) {
      const command = this._undoQueue[undoLength - 1];
      result = (this._baseId != command.getId());
    }
    return result;
  },
});

export default DesignerUndoManager;