/*
 *  eXist Open Source Native XML Database
 *  Copyright (C) 2001-09 Wolfgang M. Meier
 *  wolfgang@exist-db.org
 *  http://exist.sourceforge.net
 *  
 *  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.
 *  
 *  $Id$
 */
package org.exist.xquery.modules.example;

import org.apache.log4j.Logger;
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.FunctionParameterSequenceType;
import org.exist.xquery.value.FunctionReturnSequenceType;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceIterator;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.StringValue;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.ValueSequence;

/**
 * This is an example module showing how to create a function module.
 * 
 * @author Wolfgang Meier (wolfgang@exist-db.org)
 * @author Loren Cahlander (loren@syntactica.com)
 */
public class EchoFunction extends BasicFunction {

    private final static Logger logger = Logger.getLogger(EchoFunction.class);

    public final static FunctionSignature signature =
		new FunctionSignature(
			new QName("echo", ExampleModule.NAMESPACE_URI, ExampleModule.PREFIX),
			"A useless example function. It just echoes the input parameters.",
			new SequenceType[] { new FunctionParameterSequenceType("text", Type.STRING, Cardinality.ZERO_OR_MORE, "The text to echo")},
			new FunctionReturnSequenceType(Type.STRING, Cardinality.ZERO_OR_MORE, "the echoed text"));

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

	public Sequence eval(Sequence[] args, Sequence contextSequence)
		throws XPathException {

		// is argument the empty sequence?
		if (args[0].isEmpty()) {
			return Sequence.EMPTY_SEQUENCE;
		}
		
		// iterate through the argument sequence and echo each item
		ValueSequence result = new ValueSequence();
		for (SequenceIterator i = args[0].iterate(); i.hasNext();) {
			String str = i.nextItem().getStringValue();
			result.add(new StringValue("echo: " + str));
		}
		return result;
	}

}