/**
 * Stuff that all nodes and branches in the
 * scene tree know.
 **/
abstract public class DrawableNode {
  /**
   * The next branch/node/whatever to process
   **/
  public DrawableNode next;
  
  /**
   * Constructor for DrawableNode just sets
   * next to null
   **/
  public DrawableNode(){
    next = null;
  }
  
  /**
   * Methods to set and get next elements
   * @param nextOne next element in list
   **/
  public void setNext(DrawableNode nextOne){
    this.next = nextOne;
  }
  
  public DrawableNode getNext(){
    return this.next;
  }
  
  /**
   * Use the given turtle to draw oneself
   * @param t the Turtle to draw with
   **/
  abstract public void drawWith(Turtle t);
  // No body in the superclass
  
  /**
   * Draw on the given picture
   **/
  public void drawOn(Picture bg){
    Turtle t = new Turtle(bg);
    t.setPenDown(false);
    this.drawWith(t);
  }
  
  /** Method to remove node from list, fixing links appropriately.
   * @param node element to remove from list.
   **/
  public void remove(DrawableNode node){
    if (node==this)
    {
      System.out.println("I can't remove the first node from the list.");
      return;
    };
    
    DrawableNode current = this;
    // While there are more nodes to consider
    while (current.getNext() != null)
    {
      if (current.getNext() == node){
        // Simply make node's next be this next
        current.setNext(node.getNext());
        // Make this node point to nothing
        node.setNext(null);
        return;
      }
      current = current.getNext();
    }
  }

    
  /**
   * Insert the input node after this node.
   * @param node element to insert after this.
   **/
  public void insertAfter(DrawableNode node){
    // Save what "this" currently points at
    DrawableNode oldNext = this.getNext();
    this.setNext(node);
    node.setNext(oldNext);
  }
  
  /**
   * Return the last element in the list
   **/
    public DrawableNode last() {
      DrawableNode current;
    
      current = this;
      while (current.getNext() != null)
      {
        current = current.getNext();
      };
      return current;
  }

  /**
   * Add the input node after the last node in this list.
   * @param node element to insert after this.
   **/
  public void add(DrawableNode node){
    this.last().insertAfter(node);
  }

}