/*
 * Copyright 2007-2013
 * Licensed under GNU Lesser General Public License
 * 
 * This file is part of EpochX: genetic programming software for research
 * 
 * EpochX 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 3 of the License, or
 * (at your option) any later version.
 * 
 * EpochX 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 EpochX. If not, see <http://www.gnu.org/licenses/>.
 * 
 * The latest version is available from: http://www.epochx.org
 */
package org.epochx.epox.lang;

import org.epochx.epox.Node;
import org.epochx.tools.DataTypeUtils;

/**
 * A node which provides the facility to sequence a specific number of
 * instructions, specified at construction. Each of the instructions may be any
 * other function or terminal node with a <code>Void</code> return type. This is the
 * same function that Koza calls <code>progN</code> in his work.
 * 
 * @since 2.0
 */
public class SeqN extends Node {

    public static final String IDENTIFIER = "SEQN";

	/**
	 * Constructs a <code>SeqNFunction</code> with the given number of <code>null</code>
	 * children.
	 * 
	 * @param n the arity of the function
	 */
	public SeqN(int n) {
		this((Node) null);

		setChildren(new Node[n]);
	}

	/**
	 * Constructs a <code>SeqNFunction</code> with the given children. When 
	 * evaluated, each child will be evaluated in sequence.
	 * 
	 * @param children the child nodes to be executed in sequence
	 */
	public SeqN(Node ... children) {
		super(children);
	}

	/**
	 * Evaluates this function. Each of the children is evaluated in sequence.
	 * After evaluating its children, this method will return <code>null</code>.
	 * 
	 * @return the return type of this function node is <code>Void</code> and so
	 *         the value returned from this method is undefined
	 */
	@Override
	public Void evaluate() {
		final int arity = getArity();
		for (int i = 0; i < arity; i++) {
			getChild(i).evaluate();
		}

		return null;
	}

	/**
	 * Returns the identifier of this function which is <code>SEQN</code>
	 * 
	 * @return this node's identifier
	 */
	@Override
	public String getIdentifier() {
		return IDENTIFIER;
	}

	/**
	 * Returns this function node's return type for the given child input types.
	 * If there is the correct number of inputs of Void type, then the
	 * return type of this function is Void. Otherwise this method will return
	 * <code>null</code> to indicate that the inputs are invalid.
	 * 
	 * @return <code>Void</code> or otherwise <code>null</code> if the input type is 
	 * invalid
	 */
	@Override
	public Class<?> dataType(Class<?> ... inputTypes) {
		if ((inputTypes.length == getArity()) && DataTypeUtils.allEqual(inputTypes, Void.class)) {
			return Void.class;
		} else {
			return null;
		}
	}
}