/* $Id: ContentHandlerToXMLStreamWriter.java,v 1.6 2005/10/25 18:36:24 ryan_shoemaker Exp $
 *
 * Copyright (c) 2004, Sun Microsystems, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *
 *     * Neither the name of Sun Microsystems, Inc. nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package javanet.staxutils;

import java.util.Stack;

import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamWriter;

import org.xml.sax.Attributes;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * This is a simple utility class that adapts SAX events into StAX
 * {@link javax.xml.stream.XMLStreamWriter} events, bridging between the two
 * parser technologies.
 *
 * This ContentHandler does not own the XMLStreamWriter. Therefore, it will not
 * close or flush the writer at any point.
 * 
 * @author Ryan.Shoemaker@Sun.COM
 * @version 1.0
 */
public class ContentHandlerToXMLStreamWriter extends DefaultHandler {

  // SAX events will be sent to this XMLStreamWriter
  private final XMLStreamWriter staxWriter;

  // storage for prefix bindings
  private final Stack prefixBindings;

  public ContentHandlerToXMLStreamWriter(XMLStreamWriter staxCore) {
    this.staxWriter = staxCore;
    prefixBindings = new Stack(); // default of 10 seems reasonable
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#endDocument()
   */
  public void endDocument() throws SAXException {
    try {
      staxWriter.writeEndDocument();
      staxWriter.flush();
    } catch (XMLStreamException e) {
      throw new SAXException(e);
    }
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#startDocument()
   */
  public void startDocument() throws SAXException {
    try {
      staxWriter.writeStartDocument();
    } catch (XMLStreamException e) {
      throw new SAXException(e);
    }
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#characters(char[], int, int)
   */
  public void characters(char[] ch, int start, int length) throws SAXException {

    try {
      staxWriter.writeCharacters(ch, start, length);
    } catch (XMLStreamException e) {
      throw new SAXException(e);
    }

  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#ignorableWhitespace(char[], int, int)
   */
  public void ignorableWhitespace(char[] ch, int start, int length) throws SAXException {

    characters(ch, start, length);
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#endPrefixMapping(java.lang.String)
   */
  public void endPrefixMapping(String prefix) throws SAXException {
    // TODO: no-op?

    // I think we can ignore these SAX events because StAX
    // automatically scopes the prefix bindings.
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#skippedEntity(java.lang.String)
   */
  public void skippedEntity(String name) throws SAXException {
    try {
      staxWriter.writeEntityRef(name);
    } catch (XMLStreamException e) {
      throw new SAXException(e);
    }
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#setDocumentLocator(org.xml.sax.Locator)
   */
  public void setDocumentLocator(Locator locator) {
    // TODO: no-op?
    // there doesn't seem to be any way to pass location info
    // along to the XMLStreamWriter. On the XMLEventWriter side, you
    // can set the location info on the event objects.
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#processingInstruction(java.lang.String,
   * java.lang.String)
   */
  public void processingInstruction(String target, String data) throws SAXException {

    try {
      staxWriter.writeProcessingInstruction(target, data);
    } catch (XMLStreamException e) {
      throw new SAXException(e);
    }

  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#startPrefixMapping(java.lang.String,
   * java.lang.String)
   */
  public void startPrefixMapping(String prefix, String uri) throws SAXException {

    if (prefix.equals("xml")) {
      return;
    }

    // defend against parsers that pass null in for "xmlns" prefix
    if (prefix == null) {
      prefix = "";
    }

    prefixBindings.add(prefix);
    prefixBindings.add(uri);
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#endElement(java.lang.String,
   * java.lang.String, java.lang.String)
   */
  public void endElement(String namespaceURI, String localName, String qName) throws SAXException {

    try {
      // TODO: is this all we have to do?
      staxWriter.writeEndElement();
    } catch (XMLStreamException e) {
      throw new SAXException(e);
    }
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.xml.sax.ContentHandler#startElement(java.lang.String,
   * java.lang.String, java.lang.String, org.xml.sax.Attributes)
   */
  public void startElement(String namespaceURI, String localName, String qName, Attributes atts)
      throws SAXException {

    try {
      staxWriter.writeStartElement(getPrefix(qName), localName, namespaceURI);

      String uri, prefix;
      while (prefixBindings.size() != 0) {
        uri = (String) prefixBindings.pop();
        prefix = (String) prefixBindings.pop();
        if (prefix.length() == 0) {
          staxWriter.setDefaultNamespace(uri);
        } else {
          staxWriter.setPrefix(prefix, uri);
        }

        // this method handles "", null, and "xmlns" prefixes properly
        staxWriter.writeNamespace(prefix, uri);
      }

      writeAttributes(atts);
    } catch (XMLStreamException e) {
      throw new SAXException(e);
    }

  }

  /**
   * Generate a StAX writeAttribute event for each attribute
   * 
   * @param atts
   *          attributes from the SAX event
   */
  private void writeAttributes(Attributes atts) throws XMLStreamException {
    for (int i = 0; i < atts.getLength(); i++) {
      final String prefix = getPrefix(atts.getQName(i));
      if (!prefix.equals("xmlns")) { // defend againts broken transformers
        // that
        // report xmlns decls as attrs
        staxWriter.writeAttribute(prefix, atts.getURI(i), atts.getLocalName(i), atts.getValue(i));
      }
    }
  }

  /**
   * Pull the prefix off of the specified QName.
   * 
   * @param qName
   *          the QName
   * @return the prefix or the empty string if it doesn't exist.
   */
  private String getPrefix(String qName) {
    int idx = qName.indexOf(':');
    if (idx == -1) {
      return "";
    } else {
      return qName.substring(0, idx);
    }
  }

}
