/*
    * Copyright 2005-2007 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.kew.engine.node.var.schemes;
  
  import java.io.StringReader;
  
  import javax.xml.namespace.QName;
  import javax.xml.xpath.XPath;
  import javax.xml.xpath.XPathConstants;
  import javax.xml.xpath.XPathExpressionException;
  import javax.xml.xpath.XPathVariableResolver;
  
  import org.apache.log4j.Logger;
  import org.kuali.rice.kew.engine.RouteContext;
  import org.kuali.rice.kew.engine.node.BranchState;
  import org.kuali.rice.kew.engine.node.service.BranchService;
  import org.kuali.rice.kew.engine.node.var.Property;
  import org.kuali.rice.kew.engine.node.var.PropertyScheme;
  import org.kuali.rice.kew.rule.xmlrouting.XPathHelper;
  import org.kuali.rice.kew.service.KEWServiceLocator;
  import org.xml.sax.InputSource;
  
  
  /**
   * A PropertyScheme that resolves the Property by evaluating it as an XPath expression.
   * DocumentRouteHeaderValue variables are set on the XPath instance so they are accessible.
   * 
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class XPathScheme implements PropertyScheme {
      private static final Logger LOG = Logger.getLogger(XPathScheme.class);
  
      public String getName() {
          return "xpath";
      }
  
      public String getShortName() {
          return "xpath";
      }
  
      public Object load(Property property, final RouteContext context) {
          XPath xpath = XPathHelper.newXPath();
          final BranchService branchService = KEWServiceLocator.getBranchService();
          xpath.setXPathVariableResolver(new XPathVariableResolver() {
              public Object resolveVariable(QName name) {
                  LOG.debug("Resolving XPath variable: " + name);
                  String value = branchService.getScopedVariableValue(context.getNodeInstance().getBranch(), BranchState.VARIABLE_PREFIX + name.getLocalPart());
                  LOG.debug("Resolved XPath variable " + name + " to " + value);
                  return value;
              }
          });
          try {
              String docContent = context.getDocument().getDocContent();
              LOG.debug("Executing xpath expression '" + property.locator + "' in doc '" + docContent + "'");
              return xpath.evaluate(property.locator, new InputSource(new StringReader(docContent)), XPathConstants.STRING);
          } catch (XPathExpressionException xpee) {
              throw new RuntimeException("Error evaluating xpath expression '" + property.locator + "'", xpee);
          }
      }
  }