/**
 * Data structure representing a playing card, including its numeric value,
 * and pointers to the previous and next cards in the deck order.
 *
 * Copyright (c) 2007 William R. Fraser
 * All rights reserved.
 * 
 * @author William R. Fraser <wfraser@cs.uic.edu>
 * @version 2007.03.29
 */
public class Card
{
    private int      datum;    // value of the card
    private Card     next;     // pointer to next card in the deck
    private Card     prev;     // pointer to the previous card in the deck

    /**
     * Default constructor.
     */
    public Card()
    {
        datum = 0;
        next  = null;
        prev  = null;
    }

    /**
     * Make a new Card instance.
     *
     * @param datum Value of the card
     * @param prev Pointer to next card in the deck
     * @param next Pointer to the previous card in the deck
     */
    public Card(int datum, Card prev, Card next)
    {
        this.datum  = datum;
        this.prev   = prev;
        this.next   = next;
    }

    /**
     * Returns a String of the form "previous -> this -> next" with the values
     * of the cards.
     */
    public String toString()
    {
        String prevDat, nextDat;

        if (prev != null) {
            prevDat = ((Integer) prev.getDatum()).toString();
        } else {
            prevDat = "null";
        }

        if (next != null) {
            nextDat = ((Integer) next.getDatum()).toString();
        } else {
            nextDat = "null";
        }

        return prevDat + " -> " + datum + " -> " + nextDat;
    }

    /**
     * Set the pointer to the next card
     * @param next
     */
    public void setNext(Card next)
    {
        this.next = next;
    }

    /**
     * Set the pointer to the previous card
     * @param prev
     */
    public void setPrev(Card prev)
    {
        this.prev = prev;
    }

    /**
     * Return the next card in the deck.
     * @return
     */
    public Card getNext()
    {
        return next;
    }

    /**
     * Return the previous card in the deck.
     * @return
     */
    public Card getPrev()
    {
        return prev;
    }

    /**
     * Return the value of the card.
     * @return
     */
    public int getDatum()
    {
        return datum;
    }

    /**
     * Set the value of the card, only if it is unset (i.e. is 0).
     *
     * Throws IllegalArgumentException if the card already has a value.
     *
     * @param i
     */
    public void setDatum(int i)
    {
        if (datum != 0) {
            throw new IllegalArgumentException("Card value can only be set "
                      + "once!");
        }

        datum = i;
    }

}