/**
    * This file Copyright (c) 2019 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.importexport.contenthandler;
  
  import java.io.OutputStream;
  import java.io.UnsupportedEncodingException;
  import java.nio.charset.StandardCharsets;
  
  import javax.xml.transform.OutputKeys;
  import javax.xml.transform.Transformer;
  import javax.xml.transform.TransformerConfigurationException;
  import javax.xml.transform.TransformerFactory;
  import javax.xml.transform.sax.SAXTransformerFactory;
  import javax.xml.transform.sax.TransformerHandler;
  import javax.xml.transform.stream.StreamResult;
  
  import org.apache.jackrabbit.commons.xml.ToXmlContentHandler;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.xml.sax.ContentHandler;
  
  /**
   * A factory for {@code ContentHandler} instances streaming to XML.
   * <p>
   * This implementation tries to use a {@code SAXTransformerFactory} to instantiate
   * a content handler that supports pretty printing the XML output. If the underlying
   * implementation does support this (i.e. {@code SAXTransformerFactory.FEATURE} is
   * not supported) then {@code ToXmlContentHandler} is used as a fallback, which does not
   * do pretty printing.
   */
  public class XmlContentHandlerFactory  {
      private static final Logger LOG = LoggerFactory.getLogger(XmlContentHandlerFactory.class);
  
      public static ContentHandler newXmlContentHandler(OutputStream out) {
          try {
              TransformerFactory transformerFactory = TransformerFactory.newInstance();
              if (transformerFactory.getFeature(SAXTransformerFactory.FEATURE)) {
                  TransformerHandler handler = ((SAXTransformerFactory) transformerFactory).newTransformerHandler();
                  Transformer transformer = handler.getTransformer();
                  transformer.setOutputProperty(OutputKeys.METHOD, "xml");
                  transformer.setOutputProperty(OutputKeys.ENCODING, StandardCharsets.UTF_8.name());
                  transformer.setOutputProperty(OutputKeys.DOCTYPE_PUBLIC, "yes");
                  transformer.setOutputProperty(OutputKeys.INDENT, "yes");
                  transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
                  handler.setResult(new StreamResult(out));
                  return handler;
              } else {
                  LOG.warn("Failed to initialize XML serializer: " + SAXTransformerFactory.FEATURE + " not supported. " +
                           "Falling back to " + ToXmlContentHandler.class.getSimpleName());
  
                  return new ToXmlContentHandler(out, StandardCharsets.UTF_8.name());
              }
          } catch (TransformerConfigurationException | UnsupportedEncodingException e) {
              throw new IllegalStateException("Failed to initialize XML serializer", e);
          }
      }
  
  }