/**
 * Copyright 2010 Neuroph Project http://neuroph.sourceforge.net
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.neuroph.nnet.comp.neuron;

import org.neuroph.core.Neuron;
import org.neuroph.core.input.InputFunction;
import org.neuroph.core.transfer.TransferFunction;

/**
 * Provides behaviour specific for neurons which act as input and the output
 * neurons within the same layer. For example in Hopfield network and BAM.
 * 
 * @author Zoran Sevarac <sevarac@gmail.com>
 */
public class InputOutputNeuron extends Neuron {
	
	/**
	 * The class fingerprint that is set to indicate serialization
	 * compatibility with a previous version of the class.
	 */	
	private static final long serialVersionUID = 1L;
		
	/**
	 * Flag which is set true if neuron external input is set
	 */
	private boolean externalInputSet;
		
	/**
	 * Bias value for this neuron
	 */	
	private double bias = 0;

	/**
	 * Creates an instance of neuron for Hopfield network
	 */
	public InputOutputNeuron() {
		super();
	}

	/**
	 * Creates an instance of neuron for Hopfield network with specified input
	 * and transfer functions
	 * @param inFunc neuron input function
	 * @param transFunc neuron transfer function
	 */
	public InputOutputNeuron(InputFunction inFunc, TransferFunction transFunc) {
		super(inFunc, transFunc);
	}

	/**
	 * Sets total net input for this cell
	 * 
	 * @param input
	 *            input value
	 */
	@Override
	public void setInput(double input) {
		this.netInput = input;
		this.externalInputSet = true;
	}

	/**
	 * Returns bias value for this neuron
	 * @return bias value for this neuron
	 */	
	public double getBias() {
		return bias;
	}

	/**
	 * Sets bias value for this neuron
	 * @param bias bias value for this neuron
	 */	
	public void setBias(double bias) {
		this.bias = bias;
	}

	/**
	 * Calculates neuron output
	 */
	@Override
	public void calculate() {

		if (!externalInputSet) { // ako ulaz nije setovan spolja
			if (this.hasInputConnections()) // bias neuroni ne racunaju ulaz iz mreze jer
									// nemaju ulaze
				netInput = inputFunction.getOutput(this.inputConnections);
		}

		// calculqate cell output
		this.output = transferFunction.getOutput(this.netInput + bias); // izracunaj
																		// izlaz

		if (externalInputSet) { // ulaz setovan 'spolja' vazi samo za jedno izracunavanje
			externalInputSet = false;
			netInput = 0;
		}
	}

}
