org.refcodes.checkerboard.VonNeumannNeighbourhood Maven / Gradle / Ivy

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// This code is copyright (c) by Siegfried Steiner, Munich, Germany and licensed
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// licenses:
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// GNU General Public License, v3.0 ("http://www.gnu.org/licenses/gpl-3.0.html")
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package org.refcodes.checkerboard;

import org.refcodes.exception.BugException;

/**
 * Definitions of the Von-Neumann neighbourhood.
 */
public enum VonNeumannNeighbourhood implements Neighbourhood {

	LEFT(-1, 0), TOP(0, -1), RIGHT(1, 0), BOTTOM(0, 1);

	private int _posX;
	private int _posY;

	private VonNeumannNeighbourhood( int aPosX, int aPosY ) {
		_posX = aPosX;
		_posY = aPosY;
	}

	/**
	 * Returns the relative X position to position (0, 0).
	 * 
	 * @return The relative position X to the (0,0) coordinate.
	 */
	@Override
	public int getPositionX() {
		return _posX;
	}

	/**
	 * Returns the relative Y position to position (0, 0).
	 * 
	 * @return The relative position Y to the (0,0) coordinate.
	 */
	@Override
	public int getPositionY() {
		return _posY;
	}

	/**
	 * Returns the next clockwise state relative to the current state. Imagine
	 * the states as the positions on a clock, next to {@link #TOP} would be
	 * {@link #RIGHT}, next to {@link #RIGHT} would be {@link #BOTTOM}, and so
	 * on (clockwise).
	 * 
	 * @return The next state relative to the current state.
	 */
	@Override
	public VonNeumannNeighbourhood clockwiseNext() {
		switch ( this ) {
		case TOP:
			return RIGHT;
		case RIGHT:
			return BOTTOM;
		case BOTTOM:
			return LEFT;
		case LEFT:
			return TOP;
		default:
			throw new BugException( "Missing case statement for <" + this + "> in implementation!" );
		}
	}

	/**
	 * Returns the next anti-clockwise state relative to the current state.
	 * Imagine the states as the positions on a clock, next to {@link #TOP}
	 * would be {@link #LEFT}, next to {@link #LEFT} would be {@link #BOTTOM},
	 * and so on (anti-clockwise).
	 * 
	 * @return The next state relative to the current state.
	 */
	@Override
	public VonNeumannNeighbourhood clockwisePrevious() {
		switch ( this ) {
		case TOP:
			return LEFT;
		case LEFT:
			return BOTTOM;
		case BOTTOM:
			return RIGHT;
		case RIGHT:
			return TOP;
		default:
			throw new BugException( "Missing case statement for <" + this + "> in implementation!" );
		}
	}
}