package ejava.projects.esales.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 ESalesParser {
      @SuppressWarnings("unused")
      private static final Logger log = LoggerFactory.getLogger(ESalesParser.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 ESalesParser(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;
  
  			@SuppressWarnings("rawtypes")
  			@Override
  			public Callable<?> resolve(final String id, Class targetType) throws SAXException {
                  return new Callable() {
                      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 element
      * @return
      * @throws XMLStreamException
      * @throws JAXBException
      */
     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);
     }
 }