/**
    * 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          // replace out of date histories with the new historicStmtVO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;
      }   
  }