/**
 * 
 */
package eu.dnetlib.data.search.app;

import java.io.StringReader;
import java.io.StringWriter;
import java.util.Iterator;

import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerFactoryConfigurationError;
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.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.apache.log4j.Logger;
import org.w3c.dom.Node;
import org.xml.sax.InputSource;

/**
 * @author stoumpos
 *
 */
public class RankDocUtil {

	private static Logger logger = Logger.getLogger(RankDocUtil.class);
	
	private static XPathExpression RANK_EXPRESSION = null;
	private static XPathExpression DMF_EXPRESSION = null;
	private static Transformer TRANSFORMER = null;
	
	static {
	    try {
			TRANSFORMER = TransformerFactory.newInstance().newTransformer();
			TRANSFORMER.setOutputProperty(OutputKeys.INDENT, "yes");
			
		} catch (TransformerConfigurationException tce) {
			throw new RuntimeException("Failed to build doc transformer.", tce);
		} catch (TransformerFactoryConfigurationError tfe) {
			throw new RuntimeException("Failed to build doc transformer.", tfe);
		}
	    		
	    try {
		    XPathFactory factory = XPathFactory.newInstance();
		    XPath xpath = factory.newXPath();
		    xpath.setNamespaceContext(new DriverNamespaceContext());
		    
		    RANK_EXPRESSION = xpath.compile("/record/@rank");
		    DMF_EXPRESSION = xpath.compile("/record/result");
		    
	    } catch (XPathExpressionException e) {
			throw new RuntimeException("Failed to build xpath expression.", e);
		}
	}

	// TODO remove synchronized by removing static fields!!! 
	public static synchronized String parseDmf(String record) {
		String dmf = null;
		
		try {
			Node node = (Node) DMF_EXPRESSION.evaluate(
					new InputSource(new StringReader(record)),
					XPathConstants.NODE);

			StreamResult result = new StreamResult(new StringWriter());
			TRANSFORMER.transform(new DOMSource(node), result);
			dmf = result.getWriter().toString();
			
		} catch (XPathExpressionException xpee) {
			logger.error("Cannot parse dmf", xpee);
			
		} catch (TransformerException te) {
			logger.error("Cannot parse dmf", te);
		}
		
		return dmf;
	}
	
	public static synchronized double parseRank(String record) {
		double rank = 0.0;
		
		try {
			String string = (String) RANK_EXPRESSION.evaluate(
					new InputSource(new StringReader(record)),
					XPathConstants.STRING);
			rank = Double.parseDouble(string);
			
		} catch (XPathExpressionException xpee) {
			logger.error("Cannot parse rank", xpee);
			
		} catch (NumberFormatException nfe) {
			logger.error("Cannot parse rank", nfe);
		}
		
		return rank;
	}
}

class DriverNamespaceContext implements NamespaceContext {

    public String getNamespaceURI(String prefix) {
        if (prefix == null) {
        	throw new NullPointerException("Null prefix");
        
        } else if ("dr".equals(prefix)) {
        	return "http://www.driver-repository.eu/namespace/dr";
        
        } else if ("xml".equals(prefix)) {
        	return XMLConstants.XML_NS_URI;
        
        }
        return XMLConstants.NULL_NS_URI;
    }

    // This method isn't necessary for XPath processing.
    public String getPrefix(String uri) {
        throw new UnsupportedOperationException();
    }

    // This method isn't necessary for XPath processing either.
    public Iterator<String> getPrefixes(String uri) {
        throw new UnsupportedOperationException();
    }
}