/*
    * 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 javax.xml.namespace.QName;
  import javax.xml.xpath.XPath;
  import javax.xml.xpath.XPathConstants;
  import javax.xml.xpath.XPathExpressionException;
  import javax.xml.xpath.XPathFactory;
  
  import org.springframework.xml.namespace.SimpleNamespaceContext;
  
  import org.w3c.dom.DOMException;
  import org.w3c.dom.Node;
  import org.w3c.dom.NodeList;
  
  /**
   * JAXP 1.3-specific factory creating {@link XPathExpression} objects.
   *
   * @author Arjen Poutsma
   * @see #createXPathExpression(String)
   * @since 1.0.0
   */
  abstract class Jaxp13XPathExpressionFactory {
  
      private static XPathFactory xpathFactory = XPathFactory.newInstance();
  
      /**
       * Creates a JAXP 1.3 <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 = createXPath();
              javax.xml.xpath.XPathExpression xpathExpression = xpath.compile(expression);
              return new Jaxp13XPathExpression(xpathExpression);
          }
          catch (XPathExpressionException ex) {
              throw new org.springframework.xml.xpath.XPathParseException(
                      "Could not compile [" + expression + "] to a XPathExpression: " + ex.getMessage(), ex);
          }
      }
  
      /**
       * Creates a JAXP 1.3 <code>XPathExpression</code> from the given string expression and namespaces.
       *
       * @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 = createXPath();
              SimpleNamespaceContext namespaceContext = new SimpleNamespaceContext();
              namespaceContext.setBindings(namespaces);
              xpath.setNamespaceContext(namespaceContext);
              javax.xml.xpath.XPathExpression xpathExpression = xpath.compile(expression);
              return new Jaxp13XPathExpression(xpathExpression);
          }
          catch (XPathExpressionException ex) {
              throw new org.springframework.xml.xpath.XPathParseException(
                      "Could not compile [" + expression + "] to a XPathExpression: " + ex.getMessage(), ex);
          }
      }
  
      private static synchronized XPath createXPath() {
          return xpathFactory.newXPath();
      }
      
  
      /** JAXP 1.3 implementation of the <code>XPathExpression</code> interface. */
      private static class Jaxp13XPathExpression implements XPathExpression {
  
          private final javax.xml.xpath.XPathExpression xpathExpression;
  
          private Jaxp13XPathExpression(javax.xml.xpath.XPathExpression xpathExpression) {
              this.xpathExpression = xpathExpression;
          }
 
         public String evaluateAsString(Node node) {
             return (String) evaluate(node, XPathConstants.STRING);
         }
 
         public List<Node> evaluateAsNodeList(Node node) {
             NodeList nodeList = (NodeList) evaluate(node, XPathConstants.NODESET);
             return toNodeList(nodeList);
         }
 
         private Object evaluate(Node node, QName returnType) {
             try {
                 // XPathExpression is not thread-safe
                 synchronized (xpathExpression) {
                     return xpathExpression.evaluate(node, returnType);
                 }
             }
             catch (XPathExpressionException ex) {
                 throw new XPathException("Could not evaluate XPath expression:" + ex.getMessage(), ex);
             }
         }
 
         private List<Node> toNodeList(NodeList nodeList) {
             List<Node> result = new ArrayList<Node>(nodeList.getLength());
             for (int i = 0; i < nodeList.getLength(); i++) {
                 result.add(nodeList.item(i));
             }
             return result;
         }
 
         public double evaluateAsNumber(Node node) {
             return (Double) evaluate(node, XPathConstants.NUMBER);
         }
 
         public boolean evaluateAsBoolean(Node node) {
             return (Boolean) evaluate(node, XPathConstants.BOOLEAN);
         }
 
         public Node evaluateAsNode(Node node) {
             return (Node) evaluate(node, XPathConstants.NODE);
         }
 
         public <T> T evaluateAsObject(Node node, NodeMapper<T> nodeMapper) throws XPathException {
             Node result = (Node) evaluate(node, XPathConstants.NODE);
             if (result != null) {
                 try {
                     return nodeMapper.mapNode(result, 0);
                 }
                 catch (DOMException ex) {
                     throw new XPathException("Mapping resulted in DOMException", ex);
                 }
             }
             else {
                 return null;
             }
         }
 
         public <T> List<T> evaluate(Node node, NodeMapper<T> nodeMapper) throws XPathException {
             NodeList nodes = (NodeList) evaluate(node, XPathConstants.NODESET);
             List<T> results = new ArrayList<T>(nodes.getLength());
             for (int i = 0; i < nodes.getLength(); i++) {
                 try {
                     results.add(nodeMapper.mapNode(nodes.item(i), i));
                 }
                 catch (DOMException ex) {
                     throw new XPathException("Mapping resulted in DOMException", ex);
                 }
             }
             return results;
         }
     }
 
 }