import ciips.animation.*;
import java.awt.*;


public class ListLinked implements DrawingObj {

	private int x, y;	
	private AlgAnimFrame frame;
	/**
	 * Sentinel link reference before the start of the list
	 */

	private Link before;

	/**
	 * Sentinel link reference after the end of the list
	 */
	private Link after;


	/**
	 * Initialise a new linked list
	 * The list is initially empty
	 * The before link references the after link.
	 */

	public ListLinked() {
	after = new Link(null,null);
	before = new Link(null, after);
	} 





	
	/**
	 * Test to determine if the linked list is an empty list
	 * @return true if the list is empty
	 */

	public boolean isEmpty() { return before.successor == after; }










	/**
	 * Test to determine if the window is at the before first position
	 * @param w is the reference to the window w
	 * @return true if the window is at the before first position
	 */

	public boolean isBeforeFirst(WindowLinked w) { return w.link == before; }









	/**
	 * Test to determine if the window is at the after last position
	 * @param w is the reference to the window w
	 * @return true if the window is at the after last position
	 */
	
	public boolean isAfterLast(WindowLinked w) { return w.link == after; }









	/**
	 * Sets the window to be at the before first position
	 * @param w is the reference to the window w
	 */

	public void beforeFirst(WindowLinked w) { w.link = before; }









	/**
	 * Sets the window to be at the after last position
	 * @param w is the reference to the window w
	 */


	public void afterLast(WindowLinked w) { w.link = after; }









	/**
	 * Moves the window to the immediate right of its current position on the list
	 * @param w is the reference to the window 
	 * @exception OutOfBoundsException if the window w is at the afterLast link position
	 */

	public void next(WindowLinked w) throws OutOfBoundsException {

		if(!isAfterLast(w)) w.link = w.link.successor;

		else
		throw new OutOfBoundsException("Calling next after end of list.");
	}












	/**
	 * Moves the window w to the immediate left of its current position on the list
	 * @param w is the reference to the window 
	 * @exception OutOfBoundsException if the window w is at the beforeFirst link position
	 */

	public void previous(WindowLinked w) throws OutOfBoundsException {

		if(!isBeforeFirst(w)) {
			Link current = before.successor;
			Link previous = before;

			while(current != w.link) {
				previous = current;
				current = current.successor;
			}

		w.link = previous;

		}

		else 
		throw new OutOfBoundsException("Calling previous when window is at the before first position");
	}











	/**
	 * Insert an Object to the immediate right of the current window position
	 * @param e is the Object to insert.
	 * @param w is the reference to the window 
	 * @exception OutOfBoundsException if window w is at the beforeFirst or afterLast link position
	 */

	public void insertAfter(Object e, WindowLinked w) throws OutOfBoundsException {

		if(!isAfterLast(w)) {
			Link toLink = w.link.successor;
			w.link.successor = new Link(e, toLink);
		}

		else if (isAfterLast(w)){
			previous(w);
			w.link.successor = new Link(e, after);
		}

		else
		throw new OutOfBoundsException("Attempt to insert after the end of the list");
	}











	/**
	 * Insert an Object to the immediate left of the current window position
	 * @param e is the Object to insert.
	 * @param w is the reference to the window 
	 * @exception OutOfBoundsException if window w is at the beforeFirst or afterLast link position
	 */

/*-------------------------------------------------------------------------*/
	public void insertBefore(Object e, WindowLinked w) throws OutOfBoundsException {
		/*-*/ frame.Highlight(0);
		if(!isBeforeFirst(w)) {	/*-*/ frame.Highlight(1);
			w.link.successor = new Link(w.link.item, w.link.successor);
				if(isAfterLast(w)) after = w.link.successor;
			w.link.item = e;
			w.link = w.link.successor;
			/*-*/ frame.waitStep();
		}

		else
		throw new OutOfBoundsException("Inserting b4 the start of the list.");
	}











	/**
	 * Examines the Object that the current window is referencing
	 * @param w is the reference to the window 
	 * @return the Object that the current window is referencing
	 * @exception OutOfBoundsException if window w is at the beforeFirst or afterLast link position
	 * @exception UnderFlow if the list is empty
 	 */
	 
	public Object examine(WindowLinked w) throws OutOfBoundsException, UnderflowException {

		if(!isEmpty()) {

			if(!isBeforeFirst(w) && !isAfterLast(w)) return w.link.item;

			else
			throw new OutOfBoundsException("Window is over a non-data node.");
		}
		else 
		throw new UnderflowException("Attempt to examine a list that is empty.");
	}











	/**
	 * Replace the Object in the list which the current window is referencing
	 * @param e is the new Object that will replace the current Object.
	 * @param w is the reference to the window 
	 * @exception OutOfBoundsException if window w is at the beforeFirst or afterLast link position
	 * @exception UnderFlow if the list is empty
 	 */

	public void replace(Object e, WindowLinked w) throws OutOfBoundsException, UnderflowException {
		if(!isEmpty()) {

			if(!isBeforeFirst(w) && !isAfterLast(w)) w.link.item = e;
				
			else 
			throw new OutOfBoundsException("Attempt to examine an item that is out ofbounds.");
		}
		else
		throw new UnderflowException("Attempt to replace in an empty list");
	}
		








	/**
	 * Deletes the first link in the list
	 * @exception UnderFlow if the list is empty
 	 */

	public void deleteFromFront() throws UnderflowException {
		if(!isEmpty()) before.successor = before.successor.successor;
		
		else throw new UnderflowException("Attempt to delete from an empty list.");
	}








	/**
	 * Deletes the last link in the list
	 * @exception UnderFlow if the list is empty
 	 */


	public void deleteFromBack() throws UnderflowException {
		if(!isEmpty()) {
			Link follower = before;
			Link current = before.successor;

				while(current.successor!= after) {
				follower = current;
				current = current.successor;
				}		
	
		follower.successor = after;
		}
		else 
		throw new UnderflowException("Attempt to delete from an empty list.");
	}
		
		










	/**
	 * Prints all the Objects in the list.
	 * @exception UnderFlow if the list is empty
 	 */

	public void printList() throws UnderflowException {
		if(!isEmpty()) {
		Link current = before.successor;
			while(current != after) {
				System.out.println(current.item);
				current = current.successor;
			}
		}
		else throw new UnderflowException("Attempt to print an empty queue");
	}


	public void draw( Graphics g ) {
		Link h = before;
		while ( h != null ) {
			h.draw( g );
			h = h.successor;
			}
		}

	public void move( int x, int y ) {
		this.x = x; this.y = y;
		}

	public int getX() { return x; }
	public int getY() { return y; }

	public void initBeforeOffsc( AlgAnimFrame frame, Object t ) {
		this.frame = frame;
		}

} // end of class definition.