package ejava.projects.eleague.xml;
   
   import java.io.InputStream;
   import java.util.HashMap;
   import java.util.concurrent.Callable;
   
   import javax.xml.XMLConstants;
   import javax.xml.bind.JAXBContext;
   import javax.xml.bind.JAXBElement;
  import javax.xml.bind.JAXBException;
  import javax.xml.bind.Unmarshaller;
  import javax.xml.stream.XMLInputFactory;
  import javax.xml.stream.XMLStreamException;
  import javax.xml.stream.XMLStreamReader;
  import javax.xml.transform.stream.StreamSource;
  import javax.xml.validation.Schema;
  import javax.xml.validation.SchemaFactory;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.xml.sax.SAXException;
  
  import com.sun.xml.bind.IDResolver;
  
  /**
   * This class will read in Java objects from a specified XML file. These objects
   * can be used to create ingest data for projects.
   */
  public class ELeagueParser {
  	@SuppressWarnings("unused")
  	private Logger log = LoggerFactory.getLogger(ELeagueParser.class);
  	protected XMLInputFactory xmlif = XMLInputFactory.newInstance();
  	protected Unmarshaller um;
  	protected XMLStreamReader xmlr;
  	public static final String SAMPLE_FILE = "xml/eSales-10.xml";
  
  	/**
  	 * Pass in the JAXB class that represents the root node of the document and
  	 * an InputStream for the document to parse.
  	 * 
  	 * @param rootType
  	 *            - the class of the root type
  	 * @param is
  	 *            - am input stream with document to parse
  	 * @throws JAXBException
  	 * @throws XMLStreamException
  	 */
  	public ELeagueParser(Class<?> rootType, InputStream is)
  			throws JAXBException, XMLStreamException {
  		JAXBContext jaxbContext = JAXBContext.newInstance(rootType);
  		um = jaxbContext.createUnmarshaller();
  		xmlif = XMLInputFactory.newInstance();
  		xmlr = xmlif.createXMLStreamReader(is);
  
  		// This (anonymous) class is a near replicate of sun's DefaultIDResolver
  		// except that they added a clear() of the idmap within startDocument()
  		// that prevents the unmarshaller from being called multiple times.
  		IDResolver idResolver = new IDResolver() {
  			private HashMap<String, Object> idmap = null;
  
  			@Override
  			public Callable<?> resolve(final String id, 
  					@SuppressWarnings("rawtypes") Class targetType)
  					throws SAXException {
  				return new Callable<Object>() {
  					public Object call() throws Exception {
  						if (idmap == null)
  							return null;
  						return idmap.get(id);
  					}
  				};
  			}
  
  			@Override
  			public void bind(String id, Object obj) throws SAXException {
  				if (idmap == null)
  					idmap = new HashMap<String, Object>();
  				idmap.put(id, obj);
  			};
  		};
  		um.setProperty(IDResolver.class.getName(), idResolver);
  	}
  
  	public void setSchema(InputStream schema) throws SAXException {
  		SchemaFactory sf = SchemaFactory
  				.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
  		Schema schemaObject = sf.newSchema(new StreamSource(schema));
  		um.setSchema(schemaObject);
  	}
  
  	private boolean contains(String elements[], String localName) {
  		for (String element : elements) {
  			if (element.equalsIgnoreCase(localName)) {
  				return true;
  			}
  		}
  		return false;
  	}
  
 	/**
 	 * This method will return either the object or null if we hit the end of
 	 * stream before getting another instance. Note that only the local-name is
 	 * being used. That won't work to great when two namespaces declare a common
 	 * local-name. Should be easily fixable when needed.
 	 * 
 	 * @param elements an vararg of element names you wish to pull from document
 	 * @return The next element that matches one of the element names in elements.
 	 * @throws XMLStreamException
 	 * @throws JAXBException
 	 */
     @SuppressWarnings("rawtypes")
 	public Object getObject(String... elements) throws XMLStreamException,
 			JAXBException {
 		xmlr.next();
 		while (xmlr.hasNext()) {
 			if (xmlr.isStartElement()
 					&& contains(elements, xmlr.getName().getLocalPart())) {
 				Object object = um.unmarshal(xmlr);
 				return (object instanceof JAXBElement) ? ((JAXBElement) object)
 						.getValue() : object;
 			}
 			xmlr.next();
 		}
 		return null;
 	}
 
 	public static InputStream getSampleData() {
 		return Thread.currentThread().getContextClassLoader()
 				.getResourceAsStream(SAMPLE_FILE);
 	}
 }