/*
 *  eXist Open Source Native XML Database: Extension module
 *  Copyright (C) 2008 Josef Willenborg
 *  jwillenborg@mpiwg-berlin.mpg.de
 *  http://www.mpiwg-berlin.mpg.de
 *  
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public License
 *  as published by the Free Software Foundation; either version 2
 *  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 Lesser General Public License for more details.
 *  
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *  
 *  $Id: TextModule.java $
 */
package org.exist.xquery.modules.mpdltext;

import java.util.ArrayList;
import java.util.Date;

import org.exist.dom.QName;
import org.exist.xquery.BasicFunction;
import org.exist.xquery.Cardinality;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.StringValue;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.ValueSequence;

import de.mpg.mpiwg.berlin.mpdl.exception.ApplicationException;
import de.mpg.mpiwg.berlin.mpdl.externalObjects.app.ExtElement;
import de.mpg.mpiwg.berlin.mpdl.externalObjects.app.ExternalObjectsHandler;

/**
 * @author Josef Willenborg (jwillenborg@mpiwg-berlin.mpg.de)
 */
public class ExternalObject extends BasicFunction {

	public final static FunctionSignature signature =
		new FunctionSignature(
			new QName("externalObject", MPDLTextModule.NAMESPACE_URI, MPDLTextModule.PREFIX),
			"A function which add, update, delete or read external elements",
			new SequenceType[] { new SequenceType(Type.STRING, Cardinality.EXACTLY_ONE), 
                           new SequenceType(Type.STRING, Cardinality.EXACTLY_ONE),
			                     new SequenceType(Type.STRING, Cardinality.EXACTLY_ONE) },
			new SequenceType(Type.STRING, Cardinality.EXACTLY_ONE));

	public ExternalObject(XQueryContext context) {
		super(context, signature);
	}

	public Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException {
	  Sequence operation = args[0];  // read, update or delete
    Sequence type = args[1];
    Sequence object = args[2];
		if (operation.isEmpty() || type.isEmpty())
			return Sequence.EMPTY_SEQUENCE;
    String operationStr = operation.getStringValue();
    String typeStr = type.getStringValue();
    String objectStr = object.getStringValue();

    ValueSequence result = null;
    String resultStr = "";
    try {
      if (typeStr.equals("element")) {
        ExtElement e = ExtElement.parseXmlStr(objectStr);
        if (operation.equals("create") || operation.equals("update")) {
          Date now = new Date();
          e.setModificationDate(now);
        }
        String documentId = e.getDocumentId();
        String pageNumber = e.getPageNumber();
        if (operationStr.equals("read")) {
          ExternalObjectsHandler externalObjectsHandler = ExternalObjectsHandler.getInstance();
          ArrayList<ExtElement> elems = externalObjectsHandler.readExternalElements(documentId, pageNumber);
          if (elems != null && elems.size() > 0) {
            resultStr = "<result>";
            for (int i=0; i<elems.size(); i++) {
              ExtElement elem = elems.get(i);
              String elemXmlStr = elem.getXmlString();
              resultStr = resultStr + elemXmlStr;
            }
            resultStr = resultStr + "</result>";
          }
        } else if (operationStr.equals("create")) {
          // TODO          
        } else if (operationStr.equals("update")) {
          // TODO          
        } else if (operationStr.equals("delete")) {
          // TODO          
        }
      } else if (typeStr.equals("query")) {
          // TODO
      }
      result = new ValueSequence();
      result.add(new StringValue(resultStr));
    } catch (ApplicationException e) {
      throw new XPathException(e);
    }
		return result;
	}
	
}