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/*
 * This file is part of ***  M y C o R e  ***
 * See http://www.mycore.de/ for details.
 *
 * MyCoRe is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * MyCoRe 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 MyCoRe.  If not, see .
 */

package org.mycore.common.content.transformer;

import java.io.IOException;
import java.io.OutputStream;

import org.jdom2.Document;
import org.jdom2.JDOMException;
import org.mycore.common.MCRException;
import org.mycore.common.content.MCRContent;
import org.mycore.common.content.MCRStringContent;
import org.mycore.common.xml.MCRXMLHelper;
import org.xml.sax.SAXException;

import com.google.gson.JsonObject;

/**
 * Uses {@link MCRXMLHelper#jsonSerialize(org.jdom2.Element)} to transform the source (must be XML) to JSON.
 * @author Thomas Scheffler (yagee)
 */
public class MCRToJSONTransformer extends MCRContentTransformer {

    /* (non-Javadoc)
     * @see org.mycore.common.content.transformer.MCRContentTransformer#transform(org.mycore.common.content.MCRContent)
     */
    @Override
    public MCRContent transform(MCRContent source) throws IOException {
        JsonObject jsonObject = toJSON(source);
        MCRStringContent result = new MCRStringContent(jsonObject.toString());
        result.setMimeType(mimeType);
        result.setEncoding(getEncoding());
        result.setUsingSession(source.isUsingSession());
        return result;
    }

    private static JsonObject toJSON(MCRContent source) throws IOException {
        try {
            Document xml = source.asXML();
            return MCRXMLHelper.jsonSerialize(xml.getRootElement());
        } catch (JDOMException | SAXException e) {
            throw new MCRException(
                "Could not generate JSON from " + source.getClass().getSimpleName() + ": " + source.getSystemId(), e);
        }
    }

    @Override
    public void transform(MCRContent source, OutputStream out) throws IOException {
        JsonObject jsonObject = toJSON(source);
        out.write(jsonObject.toString().getBytes(getEncoding()));
    }

    @Override
    public String getDefaultMimeType() {
        //default by RFC 4627
        return "application/json";
    }

    @Override
    public String getEncoding() {
        //default by RFC 4627
        return "UTF-8";
    }

    @Override
    protected String getDefaultExtension() {
        return "json";
    }

}