/*
    * Copyright 2011 Jakub Narloch
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
    * http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.exolab.castor.xml.util;
  
  import java.util.Enumeration;
  
  import javax.xml.stream.XMLStreamException;
  import javax.xml.stream.XMLStreamWriter;
  
  import org.castor.core.util.Assert;
  import org.exolab.castor.xml.NamespacesStack;
  import org.xml.sax.Attributes;
  import org.xml.sax.SAXException;
  import org.xml.sax.helpers.DefaultHandler;
  
  /**
   * A document handler that uses internally a instance of {@link XMLStreamWriter} to output the result xml.
   *
   * @author <a herf="mailto:jmnarloch AT gmail DOT com">Jakub Narloch</a>
   * @version 1.3.3
   * @since 1.3.3
   */
  public class StaxStreamHandler extends DefaultHandler {
  
      /**
       * Represents the instance of {@link XMLStreamWriter} class, that will be used to output the marshalled object.
       */
      private final XMLStreamWriter xmlStreamWriter;
  
      /**
       * Instance of {@link org.exolab.castor.xml.Namespaces} used for handling the namespace.
       */
      private NamespacesStack namespacesStack = new NamespacesStack();
  
      /**
       * Flag indicating whether the new namespace scope is required to create.
       */
      private boolean createNamespaceScope = true;
  
      /**
       * Creates new instance of {@link StaxStreamHandler} class.
       *
       * @param xmlStreamWriter the instance of {@link XMLStreamWriter} to use
       *
       * @throws IllegalArgumentException if xmlStreamWriter is null
       */
      public StaxStreamHandler(XMLStreamWriter xmlStreamWriter) {
          Assert.paramNotNull(xmlStreamWriter, "xmlStreamWriter");
  
          this.xmlStreamWriter = xmlStreamWriter;
      }
  
      @Override
      public void startDocument() throws SAXException {
          try {
              xmlStreamWriter.writeStartDocument();
          } catch (XMLStreamException e) {
              convertToSAXException("Error occurred when writing the document start.", e);
          }
      }
  
      @Override
      public void endDocument() throws SAXException {
          try {
              xmlStreamWriter.writeEndDocument();
              xmlStreamWriter.flush();
          } catch (XMLStreamException e) {
              convertToSAXException("Error occurred when writing the document end.", e);
          }
      }
  
      @Override
      public void startPrefixMapping(String prefix, String uri) throws SAXException {
          if (createNamespaceScope) {
              namespacesStack.addNewNamespaceScope();
              createNamespaceScope = false;
          }
  
          namespacesStack.addNamespace(prefix, uri);
      }
  
      @Override
      public void startElement(String uri, String localName,
                               String qName, Attributes attributes) throws SAXException {
          try {
              // writes the element start
             xmlStreamWriter.writeStartElement(qName);
 
             // iterates through all attributes and writes them
             for (int i = 0; i < attributes.getLength(); i++) {
                 xmlStreamWriter.writeAttribute(attributes.getQName(i), attributes.getValue(i));
             }
 
             // retrieves the default namespace
             String defaultNamespace = namespacesStack.getDefaultNamespaceURI();
             if(defaultNamespace != null && defaultNamespace.length() > 0) {
                 xmlStreamWriter.setDefaultNamespace(defaultNamespace);
             }
 
             // iterates over all namespaces declared in current scope
             Enumeration enumeration = namespacesStack.getLocalNamespacePrefixes();
             String prefix;
             while(enumeration.hasMoreElements()) {
                 prefix = (String)enumeration.nextElement();
                 xmlStreamWriter.writeNamespace(prefix,
                         namespacesStack.getNamespaceURI(prefix));
             }
         } catch (XMLStreamException e) {
             convertToSAXException("Error occurred when writing the element start.", e);
         }
     }
 
     @Override
     public void endElement(String uri, String localName, String qName) throws SAXException {
         try {
             // writes the element end
             xmlStreamWriter.writeEndElement();
         } catch (XMLStreamException e) {
             convertToSAXException("Error occurred when writing the element end.", e);
         }
     }
 
     @Override
     public void ignorableWhitespace(char[] ch, int start, int length) throws SAXException {
         try {
             // writes the characters to output xml
             xmlStreamWriter.writeCharacters(ch, start, length);
         } catch (XMLStreamException e) {
             convertToSAXException("Error occurred when writing the white spaces.", e);
         }
     }
 
     @Override
     public void characters(char[] ch, int start, int length) throws SAXException {
         try {
             // writes the characters to output xml
             xmlStreamWriter.writeCharacters(ch, start, length);
         } catch (XMLStreamException e) {
             convertToSAXException("Error occurred when writing the characters.", e);
         }
     }
 
     @Override
     public void processingInstruction(String target, String data) throws SAXException {
         try {
             // writes the processing instruction
             xmlStreamWriter.writeProcessingInstruction(target, data);
         } catch (XMLStreamException e) {
             convertToSAXException("Error occurred when writing the processing instruction.", e);
         }
     }
 
     /**
      * Converts the passed exception into a {@link SAXException} instance with using the provided error message and
      * exception cause.
      *
      * @param msg the error message
      * @param e   the inner cause of newly created exception
      *
      * @throws SAXException the newly created exception instance
      */
     private void convertToSAXException(String msg, XMLStreamException e) throws SAXException {
         throw new SAXException(msg, e);
     }
 }