/*

  * Copyright 2007-2010 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.opensource.org/licenses/ecl2.php

  *

  * 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.rice.kns.web;

 import java.util.HashMap;

 import java.util.HashSet;

 import java.util.LinkedList;

 import java.util.Map;

 import java.util.Queue;

 import java.util.Set;

 import org.kuali.rice.kns.service.KNSServiceLocator;

 import org.kuali.rice.kns.service.KualiConfigurationService;

 import org.kuali.rice.kns.util.Guid;

 /**

  * A class which will hold a Map of editable properties, dropping editable properties when too many

  * are filled in. 

  * 

  * @author Kuali Rice Team (rice.collab@kuali.org)

  *

  */

 public class EditablePropertiesHistoryHolder implements java.io.Serializable {

         private Map<String, Set<String>> editablePropertiesMap;

         private Integer maxLength = null;

         private Queue<String> historyOrder;

         private static final String EDITABLE_PROPERTIES_HISTORY_SIZE_PROPERTY_NAME = "kns.editable.properties.history.size";

         private transient KualiConfigurationService configurationService;

         /**

          * Constructs the EditablePropertiesHistoryHolder

          *

          */

         public EditablePropertiesHistoryHolder() {

                 editablePropertiesMap = new HashMap<String, Set<String>>();

                 historyOrder = new LinkedList<String>();

         }

         /**

          * @return the maximum length of the history that this will hold

          */

         public int getMaxHistoryLength() {

                 if (maxLength == null) {

                         final String historyLengthAsString = getConfigurationService().getPropertyString(EditablePropertiesHistoryHolder.EDITABLE_PROPERTIES_HISTORY_SIZE_PROPERTY_NAME);

                         if (historyLengthAsString == null) {

                                 maxLength = new Integer(20);

                         } else {

                                 try {

                                         maxLength = new Integer(historyLengthAsString);

                                 } catch (NumberFormatException nfe) {

                                         throw new RuntimeException("Cannot convert property "+EditablePropertiesHistoryHolder.EDITABLE_PROPERTIES_HISTORY_SIZE_PROPERTY_NAME+" with value "+historyLengthAsString+" to integer", nfe);

                                 }

                         }

                 }

                 return maxLength.intValue();

         }

         /**

          * Adds a Set of editable property names to the history, keyed with the given guid String.  If the editable properties exceeds the buffer size,

          * the earliest editable properties will be bumped

          * @param editableProperties the Set of editable property names to save in the history

          * @return a String to act as a key (or guid) to the editable properties

          */

         public String addEditablePropertiesToHistory(Set<String> editableProperties) {

                 String guid = generateNewGuid();

                 if (getHistoryOrder().size() > getMaxHistoryLength()) {

                         final String guidForRemoval = getHistoryOrder().remove();

                         getEditablePropertiesMap().remove(guidForRemoval);

                 }

                 getHistoryOrder().add(guid);

                 getEditablePropertiesMap().put(guid, editableProperties);

                 return guid;

         }

         /**

          * 

          * @return a newly generated Guid to act as a key to an editable properties Set

          */

         public String generateNewGuid() {

                 final String guid = new Guid().toString();

                 return guid;

         }

         /**

          * Returns the editable properties registered with the current guid

          * @param guid the guid to find editable properties for

          * @return a Set<String> of editable properties

          */

         public Set<String> getEditableProperties(String guid) {

                 return getEditablePropertiesMap().get(guid);

         }

         /**

          * Clears out the editable properties associated with the given guid

          * @param guid the guid to clear out editable properties for

          */

         public void clearEditableProperties(String guid) {

                 getEditablePropertiesMap().put(guid, createNewEditablePropertiesEntry());

         }

         /**

          * @return the order of the entries as they chronologically were created

          */

         protected Queue<String> getHistoryOrder() {

                 return historyOrder;

         }

         /**

          * @return the Map which associates editable property guids with Sets of editable property names

          */

         protected Map<String, Set<String>> getEditablePropertiesMap() {

                 return editablePropertiesMap;

         }

         /**

          * @return a new Entry to hold the names of editable properties

          */

         protected Set<String> createNewEditablePropertiesEntry() {

                 return new HashSet<String>();

         }

         /**

          * @return an implementation of the KualiConfigurationService

          */

         protected KualiConfigurationService getConfigurationService() {

                 if (configurationService == null) {

                         configurationService = KNSServiceLocator.getKualiConfigurationService();

                 }

                 return configurationService;

         }

 }