/*
    * Copyright 2005-2010 the original author or authors.
    *
    * Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
    *
   * 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.springframework.xml.xpath;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  
  import org.jaxen.JaxenException;
  import org.jaxen.SimpleNamespaceContext;
  import org.jaxen.XPath;
  import org.jaxen.dom.DOMXPath;
  import org.w3c.dom.DOMException;
  import org.w3c.dom.Node;
  
  /**
   * Jaxen-specific factory for creating <code>XPathExpression</code>s.
   *
   * @author Arjen Poutsma
   * @see #createXPathExpression(String)
   * @since 1.0.0
   */
  abstract class JaxenXPathExpressionFactory {
  
      /**
       * Creates a Jaxen <code>XPathExpression</code> from the given string expression.
       *
       * @param expression the XPath expression
       * @return the compiled <code>XPathExpression</code>
       * @throws XPathParseException when the given expression cannot be parsed
       */
      static XPathExpression createXPathExpression(String expression) {
          try {
              XPath xpath = new DOMXPath(expression);
              return new JaxenXpathExpression(xpath);
          }
          catch (JaxenException ex) {
              throw new org.springframework.xml.xpath.XPathParseException(
                      "Could not compile [" + expression + "] to a XPathExpression: " + ex.getMessage(), ex);
          }
      }
  
      /**
       * Creates a Jaxen <code>XPathExpression</code> from the given string expression and prefixes.
       *
       * @param expression the XPath expression
       * @param namespaces the namespaces
       * @return the compiled <code>XPathExpression</code>
       * @throws XPathParseException when the given expression cannot be parsed
       */
      public static XPathExpression createXPathExpression(String expression, Map<String, String> namespaces) {
          try {
              XPath xpath = new DOMXPath(expression);
              xpath.setNamespaceContext(new SimpleNamespaceContext(namespaces));
              return new JaxenXpathExpression(xpath);
          }
          catch (JaxenException ex) {
              throw new org.springframework.xml.xpath.XPathParseException(
                      "Could not compile [" + expression + "] to a XPathExpression: " + ex.getMessage(), ex);
          }
      }
  
      /** Jaxen implementation of the <code>XPathExpression</code> interface. */
      private static class JaxenXpathExpression implements XPathExpression {
  
          private XPath xpath;
  
          private JaxenXpathExpression(XPath xpath) {
              this.xpath = xpath;
          }
  
          public Node evaluateAsNode(Node node) {
              try {
                  return (Node) xpath.selectSingleNode(node);
              }
              catch (JaxenException ex) {
                  throw new XPathException("Could not evaluate XPath expression [" + xpath + "] :" + ex.getMessage(), ex);
              }
          }
  
          public boolean evaluateAsBoolean(Node node) {
              try {
                  return xpath.booleanValueOf(node);
              }
              catch (JaxenException ex) {
                 throw new XPathException("Could not evaluate XPath expression [" + xpath + "] :" + ex.getMessage(), ex);
             }
         }
 
         public double evaluateAsNumber(Node node) {
             try {
                 return xpath.numberValueOf(node).doubleValue();
             }
             catch (JaxenException ex) {
                 throw new XPathException("Could not evaluate XPath expression [" + xpath + "] :" + ex.getMessage(), ex);
             }
         }
 
         public String evaluateAsString(Node node) {
             try {
                 return xpath.stringValueOf(node);
             }
             catch (JaxenException ex) {
                 throw new XPathException("Could not evaluate XPath expression [" + xpath + "] :" + ex.getMessage(), ex);
             }
         }
 
         @SuppressWarnings("unchecked")
         public List<Node> evaluateAsNodeList(Node node) {
             try {
                 return xpath.selectNodes(node);
             }
             catch (JaxenException ex) {
                 throw new XPathException("Could not evaluate XPath expression [" + xpath + "] :" + ex.getMessage(), ex);
             }
         }
 
         public <T> T evaluateAsObject(Node context, NodeMapper<T> nodeMapper) throws XPathException {
             try {
                 Node result = (Node) xpath.selectSingleNode(context);
                 if (result != null) {
                     try {
                         return nodeMapper.mapNode(result, 0);
                     }
                     catch (DOMException ex) {
                         throw new XPathException("Mapping resulted in DOMException", ex);
                     }
                 }
                 else {
                     return null;
                 }
             }
             catch (JaxenException ex) {
                 throw new XPathException("Could not evaluate XPath expression [" + xpath + "] :" + ex.getMessage(), ex);
             }
         }
 
         public <T> List<T> evaluate(Node context, NodeMapper<T> nodeMapper) throws XPathException {
             try {
                 List<?> nodes = xpath.selectNodes(context);
                 List<T> results = new ArrayList<T>(nodes.size());
                 for (int i = 0; i < nodes.size(); i++) {
                     Node node = (Node) nodes.get(i);
                     try {
                         results.add(nodeMapper.mapNode(node, i));
                     }
                     catch (DOMException ex) {
                         throw new XPathException("Mapping resulted in DOMException", ex);
                     }
                 }
                 return results;
             }
             catch (JaxenException ex) {
                 throw new XPathException("Could not evaluate XPath expression [" + xpath + "] :" + ex.getMessage(), ex);
             }
         }
     }
 }