// Particles for a lattice gas. Goofy rool.

import java.lang.Object;
import java.util.Vector;
import java.lang.Math;
import HexCoord;
import HexGrid;

public class Particle extends Object {
  HexGrid myHexGrid;
  public HexCoord location;
  public int direction;				  // 0 is north, goes clockwise
  public boolean bumped;
  
  public Particle(HexGrid hg, int x, int y, int d) {
    location = new HexCoord(hg, x, y);
    myHexGrid = hg;
    hg.setElementAt(this, location);
    direction = d;
  }

  public String toString() {
    return new String("Particle: direction " + direction + " at " + location);
  }

  public void rotate(int i) {
    direction = (direction + i) % 6;
    if (direction < 0)
      direction += 6;
  }
  
  // move in the given direction and check for collisions
  // the collision detection stuff is funky - basically, only the first
  // particle gets to be on that spot. Everyone on the spot where there's
  // a collision is added to the list
  public void step() {
    HexCoord newLocation = new HexCoord(location);
    newLocation.moveInDirection(direction);
    newLocation.renormalize();
    if (myHexGrid.elementAt(newLocation) == null) {
      bumped = false;
      // remove ourselves if appropriate
      if (myHexGrid.elementAt(location) == this)
	myHexGrid.setElementAt(null, location);
      myHexGrid.setElementAt(this, newLocation);
      location = newLocation;
    } else {
      if (bumped)				  // bumped last time
	rotate(Math.random() < 0.5 ? -1 : 1);	  // rotate randomly
      bumped = true;
    }
  }	
}