/**
 * Copyright (C) 2003-2008 eXo Platform SAS.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Affero General Public License
 * as published by the Free Software Foundation; either version 3
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see<http://www.gnu.org/licenses/>.
 */

package org.etk.core.rest.impl.provider;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

import javax.ws.rs.Consumes;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;
import javax.ws.rs.ext.Providers;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.UnmarshalException;
import javax.xml.transform.stream.StreamSource;

import org.etk.common.logging.Logger;
import org.etk.core.rest.provider.EntityProvider;

/**
 * @author <a href="mailto:andrew00x@gmail.com">Andrey Parfonov</a>
 * @version $Id: $
 */
@Provider
@Consumes({ MediaType.APPLICATION_XML, MediaType.TEXT_XML, MediaType.APPLICATION_XHTML_XML })
@Produces({ MediaType.APPLICATION_XML, MediaType.TEXT_XML, MediaType.APPLICATION_XHTML_XML })
public class JAXBElementEntityProvider implements EntityProvider<JAXBElement<?>> {

  /**
   * Logger.
   */
  private static final Logger LOG = Logger.getLogger(JAXBElementEntityProvider.class);

  /**
   * @see Providers
   */
  @Context
  private Providers        providers;

  /**
   * {@inheritDoc}
   */
  public boolean isReadable(Class<?> type,
                            Type genericType,
                            Annotation[] annotations,
                            MediaType mediaType) {
    return type == JAXBElement.class && genericType instanceof ParameterizedType;
  }

  /**
   * {@inheritDoc}
   */
  public JAXBElement<?> readFrom(Class<JAXBElement<?>> type,
                                 Type genericType,
                                 Annotation[] annotations,
                                 MediaType mediaType,
                                 MultivaluedMap<String, String> httpHeaders,
                                 InputStream entityStream) throws IOException {
    ParameterizedType pt = (ParameterizedType) genericType;
    Class<?> c = (Class<?>) pt.getActualTypeArguments()[0];
    try {
      JAXBContext jaxbctx = getJAXBContext(c, mediaType);
      return jaxbctx.createUnmarshaller().unmarshal(new StreamSource(entityStream), c);
    } catch (UnmarshalException e) {
      // if can't read from stream (e.g. steam is empty)
      if (LOG.isDebugEnabled())
        e.printStackTrace();
      return null;
    } catch (JAXBException e) {
      throw new IOException("Can't read from input stream " + e);
    }
  }

  /**
   * {@inheritDoc}
   */
  public long getSize(JAXBElement<?> t,
                      Class<?> type,
                      Type genericType,
                      Annotation[] annotations,
                      MediaType mediaType) {
    return -1;
  }

  /**
   * {@inheritDoc}
   */
  public boolean isWriteable(Class<?> type,
                             Type genericType,
                             Annotation[] annotations,
                             MediaType mediaType) {
    return JAXBElement.class.isAssignableFrom(type);
  }

  /**
   * {@inheritDoc}
   */
  public void writeTo(JAXBElement<?> t,
                      Class<?> type,
                      Type genericType,
                      Annotation[] annotations,
                      MediaType mediaType,
                      MultivaluedMap<String, Object> httpHeaders,
                      OutputStream entityStream) throws IOException {
    Class<?> c = t.getDeclaredType();
    try {
      JAXBContext jaxbctx = getJAXBContext(c, mediaType);
      Marshaller m = jaxbctx.createMarshaller();
      // Must respect application specified character set.
      String charset = mediaType.getParameters().get("charset");
      if (charset != null)
        m.setProperty(Marshaller.JAXB_ENCODING, charset);

      m.marshal(t, entityStream);
    } catch (JAXBException e) {
      throw new IOException("Can't write to output stream " + e);
    }
  }

  /**
   * @param type type
   * @param mediaType media type
   * @return JAXBContext JAXBContext
   * @throws JAXBException if JAXBContext creation failed
   */
  protected JAXBContext getJAXBContext(Class<?> type, MediaType mediaType) throws JAXBException {
    ContextResolver<JAXBContextResolver> resolver = providers.getContextResolver(JAXBContextResolver.class,
                                                                                 mediaType);
    if (resolver == null)
      throw new RuntimeException("Not found any JAXBContextResolver for media type " + mediaType);
    JAXBContextResolver jaxbres = resolver.getContext(type);
    return jaxbres.getJAXBContext(type);
  }

}