/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2008 by Rapid-I and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapid-i.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.operator.generator;

import com.rapidminer.example.Attribute;
import com.rapidminer.tools.RandomGenerator;

/** Generator for an artificial audio data set (based on real-world data from drilling processes).
 * 
 *  @author Sebastian Land
 *  @version $Id: DrillerOscillationFunction.java,v 1.4 2008/05/09 19:22:51 ingomierswa Exp $
 */
public class DrillerOscillationFunction implements TargetFunction {
	
	private static final double SKEW_CATASTROPHY_EXPONENT = 1.2d;
	private double TURN_PERIODS = 16d;
	private static double GENERAL_NOISE = 0.02d;
	private static double INITIAL_SKEW_RATE_VARIANCE = 0.2d;
	private static double LAST_SKEW_CHANGE_PROBABILITY = 0.2d;
	private static double MAXIMAL_SKEW_CHANGE = 0.1d;
	private static double CRITICAL_FREQUENCY_SKEW = 2.7d;
	private static double SKEW_FASTER_PREFERENCE = 0.3d;
	private int periodLength;
	private int period = 0;
	private double[] frequencePeriod;
	private double[] skew;
	private double[] skewChangeDirection;
	private double[] crashed;
	
	public DrillerOscillationFunction() {}
	
	public double calculate(double[] args) throws FunctionException {
		return 0;
	}

	public double[] createArguments(int dimension, RandomGenerator random) throws FunctionException {
		if (skew == null) {
			skew = new double[dimension - 1];
			for (int i = 0; i < dimension - 1; i++) {
				skew[i] = 1d + random.nextDoubleInRange(-INITIAL_SKEW_RATE_VARIANCE, INITIAL_SKEW_RATE_VARIANCE);
			}
			skewChangeDirection = new double[dimension - 1];
			for (int i = 0; i < dimension - 1; i++) {
				skewChangeDirection[i] = random.nextDouble() - SKEW_FASTER_PREFERENCE;
			}
			crashed = new double[dimension];
			frequencePeriod = new double[dimension - 1];
		}
		double[] values = new double[dimension];
		dimension--;
		// with later periods possible change in skewing will be more probable
		double neededProbability = Math.pow((((double)period) / periodLength) , 1.5d) * LAST_SKEW_CHANGE_PROBABILITY;
		
		// now check against needed probability
		for (int i = 0; i < dimension; i++) {
			if (skew[i] > CRITICAL_FREQUENCY_SKEW) {
				skew[i] = Math.pow(skew[i], SKEW_CATASTROPHY_EXPONENT);
				crashed[i] = 1d;
			} else {
				double dice = random.nextDouble();
				if (dice <= neededProbability) {
					// then change skew
					double skewChange = skew[i] * random.nextDoubleInRange(0, MAXIMAL_SKEW_CHANGE);
					if (random.nextDouble() <= skewChangeDirection[i]) {
						skew[i] = skew[i] - skewChange;
					} else {
						skew[i] = skew[i] + skewChange;
					}
				}
			}
		}
		// generating data
		for (int i = 0; i < dimension; i++) {
			frequencePeriod[i] = frequencePeriod[i] + ((Math.PI *  skew[i]) / TURN_PERIODS);
			values[i] = Math.sin(frequencePeriod[i]); 
			// adding noise
			values[i] = values[i] * random.nextDoubleInRange(1d - GENERAL_NOISE, 1d + GENERAL_NOISE);
		}
		values[1] = skew[0];
		values[dimension] = period;
		period++;
		if (period == periodLength) {
			crashed[dimension] = period;
			return crashed;
		}
		return values;
	}

	public Attribute getLabel() {
		return null;
	}

	public void init(RandomGenerator random) {}

	public void setLowerArgumentBound(double lower) {}

	public void setTotalNumberOfAttributes(int number) {
	}

	public void setTotalNumberOfExamples(int number) {
		this.periodLength = number;
	}

	public void setUpperArgumentBound(double upper) {}
}