package genLRS;

/**
 * Represents the abstract list state. Has a concrete toString () method that
 * uses anynomous inner classes to compute the String representation of the
 * LRStruct owner.
 * @author Dung X. Nguyen, Stephen B. Wong  Copyright 2005 - All rights reserved.
 * @stereotype abstract state
 */
abstract class ANode<E> {
    /**
     * Uses anonymous visitor class to compute a String representation.
     * Anonymous inner classes will be discussed soon!
     */
    IAlgo<Object, ?, ?> ToStringAlgo = new ToStringAlgo();
    
    String toString(LRStruct<E> owner) {
        return (String)owner.execute (ToStringAlgo);
    }
    
    /**
     * 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<E> getRest(LRStruct<E> 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 E getFirst(LRStruct<E> 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.
     * @return <code>LRStruct</code> owner
     */
    abstract LRStruct<E> setRest(LRStruct<E> tail, LRStruct<E> 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.
     * @return <code>LRStruct</code> owner
     */
    abstract <EE extends E> LRStruct<E> setFirst(EE dat, LRStruct<E> 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.
     * @return <code>LRStruct</code> owner
     */
    abstract LRStruct<E> insertFront(E dat, LRStruct<E> 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 E removeFront(LRStruct<E> owner);
    
    /**
     * Executes a visitor algorithm and returns the output.
     * @param algo the visitor algorithm to be executed.
     * @param inp the input needed by the algorithm.
     * @param owner the LRStruct referencing this ANode.
     */
    abstract <R, P>  R execute(LRStruct<E> owner, IAlgo<? super E, R, P> algo, P ... inp);
}