/*
 *  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 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.lt.lex.db.LexHandler;

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

	public final static FunctionSignature signature =
		new FunctionSignature(
			new QName("transcode", MPDLTextModule.NAMESPACE_URI, MPDLTextModule.PREFIX),
			"A function which transcodes the given string to the given coding. First parameter " +
			"is the from coding (e.g. buckwalter), second parameter is the to coding (e.g. unicode) " +
			"and third parameter is the text which should be transcoded.",
			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 GetTranscodedText(XQueryContext context) {
		super(context, signature);
	}

	public Sequence eval(Sequence[] args, Sequence contextSequence) throws XPathException {
	  Sequence fromEncodingSeq = args[0];
    Sequence toEncodingSeq = args[1];
    Sequence inputStrSeq = args[2];
    String fromEncoding = "";
    String toEncoding = "";
    String inputStr = "";
		if (fromEncodingSeq.isEmpty() || toEncodingSeq.isEmpty())
			return Sequence.EMPTY_SEQUENCE;
		fromEncoding = fromEncodingSeq.getStringValue();
		toEncoding = toEncodingSeq.getStringValue();
		inputStr = inputStrSeq.getStringValue();
		String transcodedStr = null;
		try {
	    LexHandler lexHandler = LexHandler.getInstance();
	    transcodedStr = lexHandler.transcode(fromEncoding, toEncoding, inputStr);
    } catch (ApplicationException e) {
      throw new XPathException(e);
    }
    ValueSequence result = new ValueSequence();
    result.add(new StringValue(transcodedStr));
		return result;
	}
	
}