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/***********************************************************************************************************************
 *
 * blueBill Mobile - open source birdwatching
 * ==========================================
 *
 * Copyright (C) 2009, 2010 by Tidalwave s.a.s. (http://www.tidalwave.it)
 * http://bluebill.tidalwave.it/mobile/
 *
 ***********************************************************************************************************************
 *
 * 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.
 *
 ***********************************************************************************************************************
 *
 * $Id: RdfJsonParser.java,v 012efc9c7b75 2010/07/11 12:34:22 fabrizio $
 *
 **********************************************************************************************************************/
package it.tidalwave.semantic.io.json;

import org.openrdf.model.Statement;
import org.openrdf.model.Value;
import javax.annotation.Nonnull;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.Enumeration;
import org.json.me.JSONArray;
import org.json.me.JSONException;
import org.json.me.JSONObject;
import org.json.me.JSONTokener;
import it.tidalwave.semantic.io.json.impl.Literals;
import org.openrdf.rio.RDFFormat;
import org.openrdf.rio.RDFHandlerException;
import org.openrdf.rio.RDFParseException;
import org.openrdf.rio.helpers.RDFParserBase;

/***********************************************************************************************************************
 *
 * @author  Fabrizio Giudici
 * @version $Id: $
 *
 **********************************************************************************************************************/
public class RdfJsonParser extends RDFParserBase
  {
    /*******************************************************************************************************************
     *
     * {@inheritDoc}
     *
     ******************************************************************************************************************/
    @Nonnull
    public RDFFormat getRDFFormat()
      {
        throw new UnsupportedOperationException("Not supported yet.");
      }

    /*******************************************************************************************************************
     *
     * {@inheritDoc}
     *
     ******************************************************************************************************************/
    public void parse (final @Nonnull InputStream is, final @Nonnull String string)
      throws IOException, RDFParseException, RDFHandlerException
      {
        parse(new InputStreamReader(is, "UTF-8"), string);
      }

    /*******************************************************************************************************************
     *
     * {@inheritDoc}
     *
     ******************************************************************************************************************/
    public void parse (final @Nonnull Reader r, final @Nonnull String string)
      throws IOException, RDFParseException, RDFHandlerException
      {
        try
          {
            final JSONTokener jt = new JSONTokener(readString(r));
            final JSONObject rootObject = (JSONObject)jt.nextValue();
            unmarshalGraph(rootObject);
          }
        catch (JSONException e)
          {
            throw new RDFParseException(e);
          }
      }

    /*******************************************************************************************************************
     *
     *
     ******************************************************************************************************************/
    @Nonnull
    private void unmarshalGraph (final @Nonnull JSONObject parentObject)
      throws JSONException, RDFParseException, RDFHandlerException
      {
        rdfHandler.startRDF();

        for (final Enumeration e1 = parentObject.keys(); e1.hasMoreElements();)
          {
            final String subject = e1.nextElement();
            final JSONObject object1 = parentObject.getJSONObject(subject);

            for (Enumeration e2 = object1.keys(); e2.hasMoreElements(); )
              {
                final String predicate = e2.nextElement();
                final JSONArray objects = object1.getJSONArray(predicate);

                for (int i = 0; i < objects.length(); i++)
                  {
                    final Value object = Literals.unmarshalLiteral(objects.getJSONObject(i));
                    final Statement statement = createStatement(createURI(subject), createURI(predicate), object);
                    rdfHandler.handleStatement(statement);
                  }
              }
          }

        rdfHandler.endRDF();
      }

    /*******************************************************************************************************************
     *
     *
     ******************************************************************************************************************/
    @Nonnull
    private static String readString (final @Nonnull Reader r)
      throws IOException
      {
        final StringBuilder buffer = new StringBuilder();

        for (;;)
          {
            int c = r.read();

            if (c < 0)
              {
                break;
              }

            buffer.append((char)c);
          }

        return buffer.toString();
      }
  }