CUndoHistory.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

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.
*/
package com.google.security.zynamics.zylib.gui.zygraph.realizers.KeyBehaviours.UndoHistroy;

import java.util.ArrayList;
import java.util.List;

public class CUndoHistory {
  private final List<CUndoStateData> m_undoStates = new ArrayList<CUndoStateData>();

  private int m_statePointer = 0;

  public void addState(final CUndoStateData undoData) {
    if (m_statePointer < (m_undoStates.size() - 1)) {
      final int offset = m_statePointer > 0 ? -1 : 0;

      final List<CUndoStateData> statesToRemove = new ArrayList<CUndoStateData>();

      for (int index = m_statePointer - offset; index < m_undoStates.size(); ++index) {
        statesToRemove.add(m_undoStates.get(index));
      }

      for (final CUndoStateData state : statesToRemove) {
        m_undoStates.remove(state);
      }
    }

    if (!m_undoStates.isEmpty()) {
      final CUndoStateData prevData = m_undoStates.get(m_undoStates.size() - 1);

      if (prevData.equals(undoData)) {
        m_undoStates.remove(m_undoStates.size() - 1);
      }
    }

    m_undoStates.add(undoData);

    m_statePointer = m_undoStates.size() - 1;
  }

  public boolean isEmpty() {
    return m_undoStates.isEmpty();
  }

  public void redo() {
    if (m_statePointer < (m_undoStates.size() - 1)) {
      ++m_statePointer;

      m_undoStates.get(m_statePointer).restore();
    }
  }

  public void undo() {
    if (!m_undoStates.isEmpty() && (m_statePointer > 0)) {
      --m_statePointer;

      m_undoStates.get(m_statePointer).restore();
    }
  }
}