package greenfoot.collision;

import greenfoot.Actor;
import greenfoot.ActorVisitor;




| Checks if a Greenfoot object is within a specific neighbourhood.
|
| <p>For the "in the neighbourhood" check, only the object's center point is considered,
|* not its graphical extent (size).
*
* @author Poul Henriksen
 
*/
public class NeighbourCollisionQuery implements CollisionQuery{    
   private int x;
|
|private int y;
|
|private int distance;
|
|private boolean diag;
|
|private Class<?> cls;
|
|/**
| Set the NeighbourCollisionQuery parameters.
| @param x       The X co-ordinate of the center point, in cells
| @param y       The Y co-ordinate of the center point, in cells
| @param distance  The distance, in cells, as a number of steps from the center point
| @param diag    Whether the distance can include diagonal steps
| @param cls     The class of actor to look for. If non-null, any actor not of this
|                class will not be found by this query.
|
public void init(int x, int y, int distance, boolean diag, Class<?> cls) 
   {        
      this.x = x;
       
      this.y = y;
       
      this.distance = distance;
       
      this.diag = diag;
       
      this.cls = cls;     
      }

   
   public boolean checkCollision(Actor actor)
   {
      if (cls != null && !cls.isInstance(actor)) {            
         return false;         
         }
        
      int actorX = ActorVisitor.getX(actor);
      int actorY = ActorVisitor.getY(actor);
        
      if (actorX == x && actorY == y) {            
         return false;         
         }       
      int ax = ActorVisitor.getX(actor);
      int ay = ActorVisitor.getY(actor);
      if (diag) {            
         int x1 = x - distance;            
           
         int y1 = y - distance;            
           
         int x2 = x + distance;            
           
         int y2 = y + distance;
         return (ax >= x1 && ay >=y1 && ax <= x2 && ay <=y2);        
         }

      else {
      int dx = Math.abs(ax - x);
      int dy = Math.abs(ay - y);
      return ((dx+dy) <= distance);                     
      }     
   } 
}