/*
 * Copyright (c) 2003-onwards Shaven Puppy Ltd
 * 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 'Shaven Puppy' 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 THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 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.
 */
package worm;

import com.shavenpuppy.jglib.util.FPMath;

/**
 * Directional facing constants
 * @author Cas
 */
public abstract class Facing {

	public static final int EAST = 0;
	public static final int NORTH = 1;
	public static final int WEST = 2;
	public static final int SOUTH = 3;

	public static final int[] DX = {1, 0, -1, 0};
	public static final int[] DY = {0, 1, 0, -1};
	public static final int[] ANGLE = {0, FPMath.QUARTER, FPMath.HALF, FPMath.HALF + FPMath.QUARTER};

	/**
	 * No c'tor
	 */
	private Facing() {
	}

	/**
	 * Given vector, calculate the facing.
	 * @param ddx
	 * @param ddy
	 * @param oldFacing
	 * @return 0..3, or oldFacing if vector is 0, 0 or a diagonal
	 */
	public static int calcFacing(int ddx, int ddy, int oldFacing) {
		if (ddy > 0 && ddx == 0) {
			return NORTH;
		} else if (ddy < 0 && ddx == 0) {
			return SOUTH;
		} else if (ddx > 0 && ddy == 0) {
			return EAST;
		} else if (ddx < 0 && ddy == 0) {
			return WEST;
		} else if (ddx ==0 && ddy == 0) {
			return oldFacing;
		} else {
			// Hm.
			switch (oldFacing) {
				case NORTH:
					if (ddy < 0) {
						return SOUTH;
					} else {
						return oldFacing;
					}
				case SOUTH:
					if (ddy > 0) {
						return NORTH;
					} else {
						return oldFacing;
					}
				case WEST:
					if (ddx > 0) {
						return EAST;
					} else {
						return oldFacing;
					}
				case EAST:
					if (ddx < 0) {
						return WEST;
					} else {
						return oldFacing;
					}
				default:
					return oldFacing;
			}
		}
	}
}