/*
 * Copyright (c) 2008, the JUNG Project and the Regents of the University
 * of California
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either
 * "license.txt" or
 * http://jung.sourceforge.net/license.txt for a description.
 */

package edu.uci.ics.jung.io.graphml.parser;

import java.util.Iterator;

import javax.xml.stream.XMLEventReader;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;

import edu.uci.ics.jung.graph.Hypergraph;
import edu.uci.ics.jung.io.GraphIOException;
import edu.uci.ics.jung.io.graphml.DataMetadata;
import edu.uci.ics.jung.io.graphml.GraphMLConstants;
import edu.uci.ics.jung.io.graphml.ExceptionConverter;

/**
 * Parses the data element.
 *
 * @author Nathan Mittler - nathan.mittler@gmail.com
 */
public class DataElementParser<G extends Hypergraph<V,E>,V,E> extends AbstractElementParser<G,V,E> {

    public DataElementParser(ParserContext<G,V,E> parserContext) {
        super(parserContext);
    }
    
    @SuppressWarnings("unchecked")
    public DataMetadata parse(XMLEventReader xmlEventReader, StartElement start)
            throws GraphIOException {

        try {
            // Create the new port.
            DataMetadata data = new DataMetadata();

            // Parse the attributes.
            Iterator iterator = start.getAttributes();
            while (iterator.hasNext()) {
                Attribute attribute = (Attribute) iterator.next();
                String name = attribute.getName().getLocalPart();
                String value = attribute.getValue();
                if (data.getKey() == null && GraphMLConstants.KEY_NAME.equals(name)) {
                    data.setKey(value);
                }
            }

            // Make sure the key has been set.
            if (data.getKey() == null) {
                throw new GraphIOException(
                        "Element 'data' is missing attribute 'key'");
            }

            while (xmlEventReader.hasNext()) {

                XMLEvent event = xmlEventReader.nextEvent();
                if (event.isStartElement()) {
                    StartElement element = (StartElement) event;
                        
                    // Treat any child elements as unknown
                    getUnknownParser().parse(xmlEventReader, element);
                }
                if (event.isCharacters()) {
                    Characters characters = (Characters) event;
                    data.setValue(characters.getData());
                }
                if (event.isEndElement()) {
                    EndElement end = (EndElement) event;
                    verifyMatch(start, end);
                    break;
                }
            }

            return data;
            
        } catch (Exception e) {
            ExceptionConverter.convert(e);
        }

        return null;
    }
}