/**

  * Copyright 2010 The Kuali Foundation Licensed under the

  * Educational Community 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.osedu.org/licenses/ECL-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 org.kuali.student.common.ui.client.widgets.rules;

 import java.io.Serializable;

 import java.util.ArrayList;

 import java.util.List;

 public class EditHistory implements Serializable {

     private static final long serialVersionUID = 1L;

     private List<StatementVO> histories = new ArrayList<StatementVO>();

     private static final int MAX_NUM_HISTORIES = 10;

     private int currHistoryIndex = -1;

     public EditHistory(StatementVO origStatementVO) {

         save(origStatementVO);

     }

     public void save(StatementVO historicStmtVO) {

         List<StatementVO> newHistories = new ArrayList<StatementVO>();

         // replace out of date histories with the new historicStmtVO

         if (currHistoryIndex >= 0 && currHistoryIndex < histories.size()) {

             for (int i = 0; i < currHistoryIndex + 1; i++) {

                 newHistories.add(histories.get(i));

             }

             histories = newHistories;

         }

         histories.add(RulesUtil.clone(historicStmtVO));

         currHistoryIndex++;

         // delete old element

         if (histories.size() > MAX_NUM_HISTORIES) {

             histories.remove(0);

             currHistoryIndex = histories.size() - 1;

         }

     }

     public StatementVO getLastHistoricStmtVO() {

         return RulesUtil.clone(histories.get(currHistoryIndex));

     }

     public StatementVO getSafeHistoricStmtVO(int index) {

         index = (index < 0 ? 0 : (index < histories.size() ? index : histories.size()));

         return RulesUtil.clone(histories.get(index));

     }

     public StatementVO undo() {

         currHistoryIndex--;

         currHistoryIndex = (currHistoryIndex < 0 ? -1 : currHistoryIndex);

         StatementVO lastHistoricStmtVO = getSafeHistoricStmtVO(currHistoryIndex);

         return lastHistoricStmtVO;

     }

     public StatementVO redo() {

         currHistoryIndex++;

         currHistoryIndex = (currHistoryIndex < histories.size() ? currHistoryIndex : histories.size());

         StatementVO futureHistoricStmtVO = getSafeHistoricStmtVO(currHistoryIndex);

         return futureHistoricStmtVO;

     }

     public boolean isUndoable() {

         return currHistoryIndex > 0;

     }

     public boolean isRedoable() {

         return currHistoryIndex < histories.size() - 1;

     }   

 }