/**
 * Copyright (c) 2011, 2016-2017 Luke Shumaker
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the FIRST nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY FIRST AND CONTRIBUTORS``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY NONINFRINGEMENT AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL FIRST OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @author Luke Shumaker <lukeshu@sbcglobal.net>
 */
package org.usfirst.frc.team4272.robotlib;

import edu.wpi.first.wpilibj.PIDSource;
import edu.wpi.first.wpilibj.PIDSourceType;
import edu.wpi.first.wpilibj.PIDOutput;

/**
 * RollingAvg implements a rolling average.
 */
public class RollingAvg implements PIDSource, PIDOutput {
	private PIDSource source = null;
	private double[] points;
	private double avg;
	private int i;

	/**
	 * Construct a RollingAvg that must be updated with the
	 * {@link #push(double)} or {@link #pidWrite(double)} methods.
	 *
	 * @param len The number of samples to keep in the average.
	 */
	public RollingAvg(int len) {
		points = new double[len];
		i = 0;
		avg = 0;
	}
	/**
	 * Construct a RollingAvg that will automatically update
	 * itself from a {@link PIDSource} each time {@link #pidGet()}
	 * is called.
	 *
	 * That is, it wraps the {@link PIDSource} to stabalize any
	 * noise.
	 *
	 * If {@link #pidGet()} is not called an iteration, then it is
	 * not updated that iteration; so be sure to call it each
	 * iteration whether or not you actually care about the value.
	 *
	 * @param len The number of samples to keep in the average.
	 * @param src The underlying PIDSource to read from.
	 */
	public RollingAvg(int len, PIDSource src) {
		this(len);
		source = src;
	}

	/**
	 * Push a new value on to the rolling average (pushing out a
	 * previous value).
	 *
	 * @param v The new value to push.
	 * @return The new average after pushing v.
	 */
	public double push(double v) {
		avg -= points[i];
		points[i] = v/points.length;
		avg += points[i];
		i++; i %= points.length;
		return avg;
	}

	/**
	 * Return the current value of the rolling average, without
	 * mutating anything.
	 *
	 * @return The current value of the rolling average.
	 */
	public double get() {
		return avg;
	}

	/**
	 * If constructed with an underlying {@link PIDSource}, read from it
	 * and push the value; returning the new average after pushing
	 * that value.
	 *
	 * If not constructed with an underlying {@link PIDSource},
	 * then this is simply an alias for {@link #get()}.
	 *
	 * @return The value of the rolling average.
	 */
	public double pidGet() {
		if (source!=null)
			return push(source.pidGet());
		else
			return get();
	}

	/**
	 * An alias for {@link #push(double)} (but doesn't return the
	 * new average), in order to implement the {@link PIDOutput}
	 * interface.
	 *
	 * @param output The value to push.
	 */
	public void pidWrite(double output) {
		push(output);
	}

	/**
	 * See the documentation for {@link PIDSource#setPIDSourceType(PIDSourceType)}.
	 */
	public void setPIDSourceType(PIDSourceType srcType) {
		if (source!=null)
			source.setPIDSourceType(srcType);
	}

	/**
	 * See the documentation for {@link PIDSource#getPIDSourceType}.
	 */
	public PIDSourceType getPIDSourceType() {
		if (source!=null)
			return source.getPIDSourceType();
		else
			return null;
	}
}