/*******************************************************************************
 * Copyright (c) 2005, 2010 Andrea Bittau, University College London, and others
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Andrea Bittau - initial API and implementation from the PsychoPath XPath 2.0 
 *     Jesper Steen Moeller - bug 285145 - implement full arity checking
 *     Mukul Gandhi - bug 280798 - PsychoPath support for JDK 1.4
 *******************************************************************************/

package org.eclipse.wst.xml.xpath2.processor.internal.function;

import org.eclipse.wst.xml.xpath2.processor.DynamicError;
import org.eclipse.wst.xml.xpath2.processor.ResultSequence;
import org.eclipse.wst.xml.xpath2.processor.ResultSequenceFactory;
import org.eclipse.wst.xml.xpath2.processor.internal.types.QName;
import org.eclipse.wst.xml.xpath2.processor.internal.types.XSBoolean;

import java.util.Collection;
import java.util.Iterator;

/**
 * If the value of $arg is the empty sequence, the function returns true;
 * otherwise, the function returns false.
 */
public class FnEmpty extends Function {
	/**
	 * Constructor for FnEmpty.
	 */
	public FnEmpty() {
		super(new QName("empty"), 1);
	}

	/**
	 * Evaluate arguments.
	 * 
	 * @param args
	 *            argument expressions.
	 * @throws DynamicError
	 *             Dynamic error.
	 * @return Result of evaluation.
	 */
	public ResultSequence evaluate(Collection args) throws DynamicError {
		return empty(args);
	}

	/**
	 * Empty operation.
	 * 
	 * @param args
	 *            Result from the expressions evaluation.
	 * @throws DynamicError
	 *             Dynamic error.
	 * @return Result of fn:empty operation.
	 */
	public static ResultSequence empty(Collection args) throws DynamicError {

		assert args.size() == 1;

		ResultSequence rs = ResultSequenceFactory.create_new();

		// get args
		Iterator citer = args.iterator();
		ResultSequence arg1 = (ResultSequence) citer.next();

		if (arg1.empty())
			rs.add(new XSBoolean(true));
		else
			rs.add(new XSBoolean(false));

		return rs;
	}
}