Direction.java

package ge.edu.freeuni.sdp.snake.model;

import java.util.Random;

public class Direction {

	// Note there is no Direction.NONE
	public static Direction LEFT = new Direction(-1, 0);
	public static Direction RIGHT = new Direction(1, 0);
	public static Direction UP = new Direction(0, -1);
	public static Direction DOWN = new Direction(0, 1);

	private static Direction[] ALL = {Direction.LEFT,Direction.RIGHT,Direction.UP,Direction.DOWN};

	
	private int _dx;
	private int _dy;

	private Direction(int dx, int dy) {
		_dx = dx;
		_dy = dy;
	}

	public Point addTo(Point point) {
		return new Point(point.X + _dx, point.Y + _dy);
	}

	public boolean isOppositeTo(Direction other) {
		return (this == LEFT && other == RIGHT)
				|| (this == DOWN && other == UP)
				|| (other == LEFT && this == RIGHT)
				|| (other == DOWN && this == UP);
	}
	
	public Direction getNextRandomDirection(Random random){
		Direction candidate = this;
		while(candidate==this || candidate.isOppositeTo(this)) {
			int index = random.nextInt(4);
			candidate = Direction.ALL[index];
		}
		return candidate;
	}

	public static Direction getDirection(Point from, Point to) {
		int newDx = (int)Math.signum(to.X - from.X);
		int newDy = (int)Math.signum(to.Y - from.Y);
		if(newDx == -1 && newDy == 0){
			return Direction.LEFT;
		}
		else if(newDx == 1 && newDy == 0){
			return Direction.RIGHT;
		}
		else if(newDx == 0 && newDy == -1){
			return Direction.UP;
		}
		else if(newDx == 0 && newDy == 1){
			return Direction.DOWN;
		}
		throw new IllegalStateException("no such direction");
	}
}