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/*
 * eXist-db Open Source Native XML Database
 * Copyright (C) 2001 The eXist-db Authors
 *
 * [email protected]
 * http://www.exist-db.org
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */
package org.exist.xquery.modules.example;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.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
 * @author Loren Cahlander ([email protected])
 */
public class EchoFunction extends BasicFunction {

    @SuppressWarnings("unused")
	private final static Logger logger = LogManager.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(this, "echo: " + str));
		}
		return result;
	}

}