/*
 * GetValue.java
 *
 * Created on 13 November 2006, 15:13
 * go fetch some xpath value from 
 *  and xml file
 * 
 */

package resolve;
import net.sf.saxon.om.NamespaceConstant;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.xpath.XPathEvaluator;
import org.xml.sax.InputSource;

import javax.xml.namespace.QName;
import javax.xml.transform.sax.SAXSource;
import javax.xml.xpath.*;
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.util.Iterator;
import java.util.List;
/**
 *
 * @author dpawson
 */
public class GetValue  implements XPathVariableResolver{


 /**
  *Filename of input document - Set by constructor, read by all methods
  **/
 private String filename="";

 /**
  *The compiled source document
  **/
 NodeInfo builtDoc=null;


 /**
  * XpathExpression to be used
  **/
 //XPath xpe = null;
 XPath xpe=null;


 /**
  *Debug value - Higher value, more output
  **/
 private int debug=6;

 /** Constructor Creates a new instance of GetValue
  * Set the filename as the working document
  *
  **/
 public GetValue(String filename) {
   this.filename=filename;
   this.builtDoc = buildSrc(filename);
 }


 /**
  *Build the source document into Saxon specific format
  **/
 public NodeInfo buildSrc(String inputDocument){
   InputSource is=null;;
   //Following is specific to Saxon: should be in a properties file
   System.setProperty("javax.xml.xpath.XPathFactory:"+
     NamespaceConstant.OBJECT_MODEL_SAXON,
"net.sf.saxon.xpath.XPathFactoryImpl");
   XPathFactory xpf =null;
   try {
     xpf= XPathFactory.newInstance(NamespaceConstant.OBJECT_MODEL_SAXON);
   } catch (XPathFactoryConfigurationException ex) {
     System.err.println("Unable to create Xpath factory. Quitting\n"+
ex.toString());
     ex.printStackTrace();
   }
   this.xpe = xpf.newXPath();
   if (debug > 6){
     System.err.println("Loaded xpath provider "+xpe.getClass());
   }

   try {
     is = new InputSource(new File(inputDocument).toURL().toString());
   } catch (MalformedURLException ex) {
     System.err.println("Input file exception" + ex.toString());
     ex.printStackTrace();
     System.exit(2);
   }
   SAXSource ss = new SAXSource(is);
   NodeInfo doc =null;
   try {
     doc = ((XPathEvaluator)xpe).setSource(ss);
   } catch (net.sf.saxon.trans.XPathException ex) {
     System.err.println("Xpath exception, quitting. \n"+ ex.toString());
     ex.printStackTrace();
   }
   return doc;
 }


 /**
  *Resolve the xpath expression against the input document
  **/
 public String [] resolveExpression(String xpathExpression){
   xpe.setXPathVariableResolver(this);
   XPathExpression exp=null;
   String [] res= null;
   List matchedLines=null;
   try {
     exp = xpe.compile(xpathExpression);
   } catch (XPathExpressionException ex) {
     System.err.println("Invalid xpath expression "+ xpathExpression);
     ex.printStackTrace();
   }
   try {
     matchedLines = (List)exp.evaluate(builtDoc, XPathConstants.NODESET);
     if (debug > 2){
       System.err.println(matchedLines.size()+" matches");
     }
   } catch (XPathExpressionException ex) {
     System.err.println("Invalid xpath expression: "+ xpathExpression);
     ex.printStackTrace();
   }
   if (matchedLines != null){
     int i = 0;
     Iterator iter = matchedLines.iterator();
     res = new String[matchedLines.size()];
     NodeInfo item = null;
     while ( iter.hasNext()){
       item = (NodeInfo)iter.next();
       res[i]=item.getStringValue();
       i++;
     }
   }
   return res;
 }


 /**
  * This class serves as a variable resolver. The only variable used is $word.
  * @param qName the name of the variable required
  * @return the current value of the variable
  */

 public Object resolveVariable(QName qName) {
   if (qName.getLocalPart().equals("word")) {
     return "";
   } else {
     return null;
   }
 }
 public static void main(String []args){
   GetValue m = new GetValue("in.xml");
   String exp="//attendee-list/name[1]";
   String names [] = m.resolveExpression(exp);
   for (int i = 0; i < names.length; i++){
     System.out.println( names[i]);
   }

 }

}