/*
 * Copyright (C) 1999-2004 <a href="mailto:mandarax@jbdietrich.com">Jens Dietrich</a>
 *
 * 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 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.mandarax.lib.date;

import java.util.Calendar;
import org.mandarax.kernel.Term;
import org.mandarax.kernel.Session;
import org.mandarax.lib.AbstractFunction;

/**
 * Abstract superclass for date functions with one argument returning an integer.
 * @author <A HREF="mailto:mandarax@jbdietrich.com">Jens Dietrich</A>
 * @version 3.3.1 <9 August 2004>
 * @since 1.4
 */
public abstract class UnaryDateFunction1 extends AbstractFunction {

	private static Class[] structure = { Calendar.class };

	/**
	 * Get the return type of the function.
	 * @return the return type of the function
	 */
	public Class getReturnType() {
		return Integer.class;
	}

	/**
	 * Get the structure of the function.
	 * @return the structure of the function
	 */
	public Class[] getStructure() {
		return structure;
	}

	/**
	 * Perform the function using an array of terms as parameters.
	 * @return the result of the computation
	 * @param parameter an array of terms
	 * @param session a session object
	 * @throws java.lang.UnsupportedOperationException
	 * @throws java.lang.IllegalArgumentException
	 */
	public Object perform(Term[] parameter, Session session)
		throws IllegalArgumentException, UnsupportedOperationException {
		Calendar c = null;

		try {
			c = (Calendar) (parameter[0].resolve(session));
		} catch (Exception x) {
			throw new IllegalArgumentException();
		}

		return new Integer(compute(c));
	}

	/**
	 * Compute the result using the function.
	 * @return the result
	 * @param c value
	 */
	protected abstract int compute(Calendar c);
}
