package org.tinyjee.maven.dim.utils;
   
   import org.w3c.dom.Document;
   import org.w3c.dom.Node;
   import org.w3c.dom.NodeList;
   
   import javax.xml.namespace.NamespaceContext;
   import javax.xml.transform.OutputKeys;
   import javax.xml.transform.Transformer;
  import javax.xml.transform.TransformerException;
  import javax.xml.transform.TransformerFactory;
  import javax.xml.transform.dom.DOMSource;
  import javax.xml.transform.stream.StreamResult;
  import javax.xml.xpath.XPath;
  import javax.xml.xpath.XPathConstants;
  import javax.xml.xpath.XPathExpressionException;
  import javax.xml.xpath.XPathFactory;
  import java.io.StringWriter;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  
  /**
   * Implements {@link XPathEvaluator}.
   *
   * @author Juergen_Kellerer, 2011-10-12
   */
  public class XPathEvaluatorImplementation implements XPathEvaluator {
  
  	public static final String DEFAULT_PREFIX = "default";
  
  	public static String serializeNode(Node node, boolean omitDeclaration, boolean standalone) {
  		try {
  			StringWriter buffer = new StringWriter(4096);
  			Transformer transformer = TransformerFactory.newInstance().newTransformer();
  			if (omitDeclaration) transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
  			if (standalone) transformer.setOutputProperty(OutputKeys.STANDALONE, "yes");
  			transformer.transform(new DOMSource(node), new StreamResult(buffer));
  			return buffer.toString();
  		} catch (TransformerException e) {
  			throw new RuntimeException(e);
  		}
  	}
  
  	private final Node context;
  	private final XPath xPath;
  
  	/**
  	 * Creates a new evaluator around the given document.
  	 *
  	 * @param document the document to evaluate on.
  	 */
  	public XPathEvaluatorImplementation(final Document document) {
  		context = document;
  		xPath = XPathFactory.newInstance().newXPath();
  		xPath.setNamespaceContext(new NamespaceContext() {
  			public String getNamespaceURI(String prefix) {
  				return DEFAULT_PREFIX.equals(prefix) ? document.lookupNamespaceURI(null) : document.lookupNamespaceURI(prefix);
  			}
  
  			public String getPrefix(String namespaceURI) {
  				return namespaceURI.equals(document.lookupNamespaceURI(null)) ? DEFAULT_PREFIX : document.lookupPrefix(namespaceURI);
  			}
  
  			public Iterator getPrefixes(String namespaceURI) {
  				return Collections.singleton(getPrefix(namespaceURI)).iterator();
  			}
  		});
  	}
  
  	private XPathEvaluatorImplementation(XPath xPath, Node context) {
  		this.xPath = xPath;
  		this.context = context;
  	}
  
  	public String findText(String xpathExpression) {
  		try {
  			return (String) xPath.evaluate(xpathExpression, context, XPathConstants.STRING);
  		} catch (XPathExpressionException e) {
  			throw new RuntimeException(e);
  		}
  	}
  
  	public List<Node> findNodes(String xpathExpression) {
  		try {
  			final NodeList nodeList = (NodeList) xPath.evaluate(xpathExpression, context, XPathConstants.NODESET);
  			return asList(nodeList);
  		} catch (XPathExpressionException e) {
  			throw new RuntimeException(e);
  		}
  	}
  
  	public String serialize(Node node) {
  		return serializeNode(node, true, true);
  	}
  
  	public List<Node> asList(final NodeList nodeList) {
  		return new NodeListAdapter(nodeList);
  	}
 
 	public XPathEvaluator newEvaluator(Node node) {
 		return new XPathEvaluatorImplementation(xPath, node);
 	}
 }