/*
 * Copyright 2012  Research Studios Austria Forschungsges.m.b.H.
 *
 *    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 won.protocol.rest;

import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.ModelFactory;
import org.apache.jena.atlas.web.ContentType;
import org.apache.jena.riot.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

import java.io.IOException;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;


/**
 * HttpMessageConverter for using jena models with Spring WebMVC. Supports all formats jena supports, plus JSON-LD
 */
public class RdfModelConverter extends AbstractHttpMessageConverter<Model> {
    private static final Logger logger = LoggerFactory.getLogger(RdfModelConverter.class);

    public RdfModelConverter() {
      this(buildMediaTypeArray());
    }

    public RdfModelConverter(MediaType supportedMediaType) {
        super(supportedMediaType);
    }

    public RdfModelConverter(MediaType... supportedMediaTypes) {
        super(supportedMediaTypes);
    }

    @Override
    protected boolean supports(Class<?> clazz) {
        return Model.class.isAssignableFrom(clazz);
    }

    @Override
    protected Model readInternal(Class<? extends Model> aClass, HttpInputMessage httpInputMessage) throws IOException, HttpMessageNotReadableException {
      Model model = ModelFactory.createDefaultModel();
      Lang rdfLanguage = mimeTypeToJenaLanguage(httpInputMessage.getHeaders().getContentType(), Lang.TURTLE);
      RDFDataMgr.read(model, httpInputMessage.getBody(), "", rdfLanguage);
      return model;
    }

    @Override
    protected void writeInternal(Model model, HttpOutputMessage httpOutputMessage) throws IOException, HttpMessageNotWritableException {
      Lang rdfLanguage = mimeTypeToJenaLanguage(httpOutputMessage.getHeaders().getContentType(), Lang.N3);
      RDFDataMgr.write(httpOutputMessage.getBody(), model, rdfLanguage);
      httpOutputMessage.getBody().flush();
    }

    private static Lang mimeTypeToJenaLanguage(MediaType mediaType, Lang defaultLanguage) {
      Lang lang = RDFLanguages.contentTypeToLang(mediaType.toString());
      if (lang == null) return defaultLanguage;
      return lang;
    }

    private static MediaType[] buildMediaTypeArray(){
      // now register the media types this converter can handle
      Collection<Lang> languages = RDFLanguages.getRegisteredLanguages();
      Set<MediaType> mediaTypeSet = new HashSet<MediaType>();
      for(Lang lang: languages){
        if (datasetWriterExistsForLang(lang)) {
          ContentType ct = lang.getContentType();
          logger.debug("registering converter for rdf content type {}", lang.getContentType());
          MediaType mt = new MediaType(ct.getType(), ct.getSubType());
          mediaTypeSet.add(mt);
        }
      }
      return mediaTypeSet.toArray(new MediaType[mediaTypeSet.size()]);
    }

  private static boolean datasetWriterExistsForLang(Lang lang) {
    RDFFormat serialization = RDFWriterRegistry.defaultSerialization(lang) ;
    WriterDatasetRIOTFactory wf = RDFWriterRegistry.getWriterDatasetFactory(serialization) ;
    return wf != null;
  }



}