/*
    * Copyright 2005-2008 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.edl.impl.components;
  
  import java.util.List;
  
  import org.apache.commons.lang.StringUtils;
  import org.kuali.rice.edl.impl.EDLContext;
  import org.kuali.rice.edl.impl.EDLModelComponent;
  import org.kuali.rice.edl.impl.EDLXmlUtils;
  import org.kuali.rice.edl.impl.RequestParser;
  import org.w3c.dom.Document;
  import org.w3c.dom.Element;
  
  
  /**
   * Handles setting the current page in the EDL XML.
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   *
   */
  public class PageHandler implements EDLModelComponent {
  
  	public static final String CURRENT_PAGE = "currentPage";
  	public static final String PREVIOUS_PAGE = "previousPage";
  	public static final String GOTO_PAGE = "edl.gotoPage";
  	
  	public void updateDOM(Document dom, Element configElement, EDLContext edlContext) {
  	    String currentPage = edlContext.getRequestParser().getParameterValue("edl." + CURRENT_PAGE);
  	    String previousPage = edlContext.getRequestParser().getParameterValue("edl." + PREVIOUS_PAGE);
  	    String gotoPage = findGotoPage(edlContext.getRequestParser(), currentPage);
  	    if (!StringUtils.isBlank(gotoPage)) {
  		previousPage = currentPage;
  		currentPage = gotoPage;
  	    }
  	    establishCurrentPage(dom, currentPage);
  	    establishPreviousPage(dom, previousPage);
  	}
  	
  	/**
  	 * Find parameter that looks like gotoPage:<pageName>
  	 */
  	private String findGotoPage(RequestParser requestParser, String currentPage) {
  	    List<String> parameterNames = requestParser.getParameterNames();
  	    for (String parameterName : parameterNames) {
  		if (parameterName.startsWith(GOTO_PAGE + ":")) {
  		    return parameterName.split(":")[1];
  		}
  	    }
  	    return null;
  	}
  
  	private void establishCurrentPage(Document dom, String currentPage) {
  	    if (!StringUtils.isBlank(currentPage)) {
  		Element currentPageElement = EDLXmlUtils.getOrCreateChildElement(dom.getDocumentElement(), CURRENT_PAGE, true);
  		currentPageElement.appendChild(dom.createTextNode(currentPage));
  	    }
  	}
  	
  
  	private void establishPreviousPage(Document dom, String previousPage) {
  	    if (!StringUtils.isBlank(previousPage)) {
  		Element previousPageElement = EDLXmlUtils.getOrCreateChildElement(dom.getDocumentElement(), PREVIOUS_PAGE, true);
  		previousPageElement.appendChild(dom.createTextNode(previousPage));
  	    }
  	}
  	    
  
  }