package lrs;

/**
 * Represents the abstract list state.
 * @author Dung X. Nguyen  Copyright 2000 - All rights reserved.
 * @since 02/15/00
 */
abstract class ANode
{
    /**
     * Returns the tail LRStruct of the referencing LRStruct.
     * @param owner the LRStruct referencing this ANode.
     * @return the tail LRStruct of owner.
     * @throw java.util.NoSuchElementException if empty.
     */
    abstract LRStruct getRest(LRStruct owner);

    /**
     * Returns the first data object of the referencing LRStruct.
     * @param owner the LRStruct referencing this ANode.
     * @return the tail LRStruct of owner.
     * @throw java.util.NoSuchElementException if empty.
     */
    abstract Object getFirst(LRStruct owner);

    /**
     * Sets a new tail for the referencing LRStruct.
     * @param tail the new tail for the owner LRStruct.
     * @param owner the LRS referencing this ANode.
     * @throw java.util.NoSuchElementException if empty.
     */
    abstract void setRest(LRStruct tail, LRStruct owner);

    /**
     * Sets a new first data object for the referencing LRStruct.
     * @param first the new data object for this ANode.
     * @param owner the LRS referencing this ANode.
     * @throw java.util.NoSuchElementException if empty.
     */
    abstract void setFirst(Object dat, LRStruct owner);

    /**
     * Inserts a data object at the front of the LRStruct owner.
     * @param dat the object to be inserted at the front.
     * @param owner the LRS referencing this ANode.
     */
    abstract void insertFront(Object dat, LRStruct owner);

    /**
     * Removes and returns the first data object for the referencing LRStruct.
     * @param owner the LRS referencing this ANode.
     * @return the front data of the LRStruct owner.
     */
    abstract Object removeFront(LRStruct owner);

    /**
     * Executes an algorithm and returns the output.
     * @param visitor the algorithm to be executed.
     * @param input the input needed by the algorithm.
     * @param owner the LRStruct referencing this ANode.
     */
    abstract Object execute(IAlgo visitor, Object input, LRStruct owner);
}