Sprite

package feAttempt;

public class Sprite
{
  private Grid<Sprite> grid;
  private Location location;
  private String imageFileName;

  /**
   * Gets the grid in which this sprite is located.
   * @return the grid of this sprite, or <code>null</code> if this sprite is
   * not contained in a grid
   */
  public Grid<Sprite> getGrid()
  {
    return grid;
  }

  /**
   * Gets the location of this sprite.
   * @return the location of this sprite, or <code>null</code> if this sprite is
   * not contained in a grid
   */
  public Location getLocation()
  {
    return location;
  }

  public String getImageFileName()
  {
    return imageFileName;
  }

  public void setImageFileName(String imageFileName)
  {
    this.imageFileName = imageFileName;
  }

  /**
   * Puts this sprite into a grid. If there is another sprite at the given
   * location, it is removed. <br />
   * Precondition: (1) This sprite is not contained in a grid (2)
   * <code>loc</code> is valid in <code>gr</code>
   * @param gr the grid into which this sprite should be placed
   * @param loc the location into which the sprite should be placed
   */
  public void putSelfInGrid(Grid<Sprite> gr, Location loc)
  {
    if (grid != null)
      throw new IllegalStateException(
                                      "This sprite is already contained in a grid.");

    Sprite sprite = gr.get(loc);
    if (sprite != null)
      sprite.removeSelfFromGrid();
    gr.put(loc, this);
    grid = gr;
    location = loc;
  }

  /**
   * Removes this sprite from its grid. <br />
   * Precondition: This sprite is contained in a grid
   */
  public void removeSelfFromGrid()
  {
    if (grid == null)
      throw new IllegalStateException(
                                      "This sprite is not contained in a grid.");
    if (grid.get(location) != this)
      throw new IllegalStateException(
                                      "The grid contains a different sprite at location "
                                        + location + ".");

    grid.remove(location);
    grid = null;
    location = null;
  }

  /**
   * Moves this sprite to a new location. If there is another sprite at the
   * given location, it is removed. <br />
   * Precondition: (1) This sprite is contained in a grid (2)
   * <code>newLocation</code> is valid in the grid of this sprite
   * @param newLocation the new location
   */
  public void moveTo(Location newLocation)
  {
    if (grid == null)
      throw new IllegalStateException("This sprite is not in a grid.");
    if (grid.get(location) != this)
      throw new IllegalStateException(
                                      "The grid contains a different sprite at location "
                                        + location + ".");
    if (!grid.isValid(newLocation))
      throw new IllegalArgumentException("Location " + newLocation
                                           + " is not valid.");

    if (newLocation.equals(location))
      return;
    grid.remove(location);
    Sprite other = grid.get(newLocation);
    if (other != null)
      other.removeSelfFromGrid();
    location = newLocation;
    grid.put(location, this);
  }

  /**
   * Creates a string that describes this sprite.
   * @return a string with the location of this sprite
   */
  public String toString()
  {
    return getClass().getName() + "[location=" + location + "]";
  }
}