package rac;

/**
 * The abstract node of a doubly-linked Lisp-like circular  list.
 * @author S. Wong
 */
public abstract class ARACNode{
    protected ARACNode next;
    protected ARACNode previous;
    /**
     * Accessor method to get the next node in the doubly linked circular  list.
     * @return An abstract node
     */
    public ARACNode getNext()  {
        return next;
    }

    /**
     * Accessor method to get the previous node in the doubly-linked circular  list.
     * @return An abstract node
     */
    public ARACNode getPrevious() {
        return previous;
    }

    /**
     * Accessor method to set the next node of the doubly linked circular  list.
     *  The remaining links to the node are NOT established.
     * @param next The new next node.
     */
    protected void setNext(ARACNode next) {
        this.next = next;
    }

    /**
     * Accessor method to set the previous node of the doubly linked circular list.
     *  The remaining  links to the node are NOT established.
     * @param previous The new previous node.
     */
    protected void setPrevious(ARACNode previous) {
        this.previous = previous;
    }

    /**
     * Inserts the supplied data into a new previous node of the current node.
     * The links to the new node are automatically established.
     * @param data The data to inserts
     */
    public void insertPrevious(Object data) {
        previous.insertNext(data);
    }

    /**
     * Inserts the supplied data as a new next node of the current node.
     * The links to the new node are automatically established.
     * @param data The data to store.
     */
    public void insertNext(Object data) {
        ARACNode tmpNext = next;
        next = new RACDataNode(data, tmpNext, this);
        tmpNext.setPrevious(next);
    }

    /**
     * Abstract method that removes the current node, returning its data.
     * The links to/from this node are automatically connected.
     * @return The data stored in the current node.
     */
    public abstract Object removeNode();

    /**
     * Generalized abstract method to execute a visitor design pattern IRACVisitor algorithm on the doubly linked circular list.
     * @param param An generalized parameter for use by the visiting algorithm.
     * @param visitor An IRACVisitor algorithm to be executed on the list.
     * @return A genrealized output from the algorithm.
     */
    public abstract Object execute(IRACVisitor visitor, Object param);
}