/*
    * 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;
 	}
 }