/**

  * Copyright 2005-2011 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.rule.xmlrouting;

 import javax.xml.xpath.XPath;

 import javax.xml.xpath.XPathFactory;

 import javax.xml.xpath.XPathFunctionResolver;

 import org.kuali.rice.kew.api.WorkflowRuntimeException;

 import org.w3c.dom.Node;

 /**

  * Provides utilities for obtaining XPath instances which are "good-to-go" with access to the Workflow

  * namespace and custom XPath functions.

  * 

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

  */

 public class XPathHelper {

         /**

          * Creates a new XPath instance and initializes it with the WorkflowNamespaceContext and the

          * WorkflowFunctionResolver.

          */

         public static XPath newXPath() {

                 XPath xPath = XPathFactory.newInstance().newXPath();

                 xPath.setNamespaceContext(new WorkflowNamespaceContext());

                 WorkflowFunctionResolver resolver = new WorkflowFunctionResolver();

                 xPath.setXPathFunctionResolver(resolver); 

                 resolver.setXpath(xPath);

                 return xPath;

         }

         /**

          * Creates a new XPath instances and initializes it with the WorkflowNamespaceContext and the

          * WorkflowFunctionResolver.  Also sets the root node on the WorkflowFunctionResolver to 

          * the given Node.  This is required for some of the functions in the function resolver

          * to perform properly.

          */

         public static XPath newXPath(Node rootNode) {

                 XPath xPath = newXPath();

                 WorkflowFunctionResolver resolver = extractFunctionResolver(xPath);

                 resolver.setRootNode(rootNode);

                 return xPath;

         }

         /**

          * A utility to extract the WorkflowFunctionResolver from the given XPath instances.  If the XPath instance

          * does not contain a WorkflowFunctionResolver, then this method will throw a WorkflowRuntimeException.

          * 

          * @throws WorkflowRuntimeException if the given XPath instance does not contain a WorklflowFunctionResolver

          */

         public static WorkflowFunctionResolver extractFunctionResolver(XPath xPath) {

                 XPathFunctionResolver resolver = xPath.getXPathFunctionResolver();

                 if (!hasWorkflowFunctionResolver(xPath)) {

                         throw new WorkflowRuntimeException("The XPathFunctionResolver on the given XPath instance is not an instance of WorkflowFunctionResolver, was: " + resolver);

                 }

                 return (WorkflowFunctionResolver)resolver;

         }

         /**

          * Returns true if the given XPath instance has a WorkflowFunctionResolver, false otherwise.

          */

         public static boolean hasWorkflowFunctionResolver(XPath xPath) {

                 return xPath.getXPathFunctionResolver() instanceof WorkflowFunctionResolver;

         }

 }