TrackTarget.java

package vooga.towerdefense.action.movement;

import vooga.towerdefense.action.TargetedAction;
import vooga.towerdefense.attributes.Attribute;
import util.Location;
import util.Vector;


/**
 * Action to move from one location to another location, or to a target. If
 * followTarget is true, projectile follows target, else it moves in straight line
 * in target's direction.
 * 
 * @author Xu Rui
 * 
 */
public class TrackTarget extends TargetedAction {

    private Vector myHeading;
    private Location myCenter;
    private Location myDestination;

    private Attribute mySpeed;
    private boolean isTargetTracking;
    private boolean headingSet;

    public TrackTarget (Location start, Location destination,
                         Attribute movespeed, boolean followTarget) {
        super();
        mySpeed = movespeed;
        myCenter = start;
        myDestination = destination;
        isTargetTracking = followTarget;
        headingSet = false;
    }
    
    public void update(double elapsedTime) {
        if (isEnabled()) {
            executeAction(elapsedTime);
        }
        else {
            updateFollowUpActions(elapsedTime);
        }
    }

    @Override
    public void executeAction (double elapsedTime) {    
		myDestination = getSingleTarget().getCenter();
		setFollowTarget(isTargetTracking);
		Vector v = new Vector(myHeading.getDirection(), mySpeed.getValue());
		v.scale(elapsedTime / 1000);
		myCenter.translate(v);
		updateTargetedFollowUpActions(getTargets());
    }

    /**
     * Set whether projectile follows path of target, or shoots off in initial
     * target direction.
     * 
     * @param follow
     */
    public void setFollowTarget (boolean follow) {
        if (headingSet && !follow) {
            return;
        }
        else {
            myHeading =
                    new Vector(Vector.angleBetween(myDestination, myCenter), mySpeed.getValue());
            headingSet = true;
        }
    }
}