/* @(#)IntArrayListIterator.java   31 October 2005 */

/**
 * An IntArrayListIterator traverses an IntArrayList.
 */
public class IntArrayListIterator
{
    IntArrayList list = null;
    
    IntArrayListNode node = null;
    
    int index = 0;
    
    
    /**
     * Constructs an iterator for the given IntArrayList.
     * 
     * Throws NullPointerException if the given IntArrayList
     * is null.
     */
    public IntArrayListIterator(IntArrayList thelist) {
        if (thelist == null)
            throw new NullPointerException
                ("Null list in IntArrayListIterator constructor");
        
        list = thelist;
        node = list.getHead();
    }
    
    
    /**
     * Returns true if there is a data item available in
     * the list at the current location of this iterator.
     */
    public boolean hasData() {
        if (node == null)
            return false;
        
        if (index < node.getCount())
            return true;
        
        IntArrayListNode next = node.getNext();
        
        if (next == null)
            return false;
        
        return next.getCount() > 0;
    }
    
    
    /**
     * Returns the current data item.
     * 
     * Advances the iterator to the next data item if more
     * data is available or to the end of the list.
     * 
     * Throwns RuntimeException if the iterator is already
     * at the end of the list, that is, hasData() is false
     * when this method is called.
     */
    public int getData() {
        if (! hasData())
            throw new RuntimeException
                ("Request for data at the end of the list");
        
        if (index >= node.getCount()) {
            node = node.getNext();
            index = 0;
        }

        int contents = node.getDataItem(index);
        index++;
        
        return contents;
    }
    
    
    /**
     * Advances the iterator to the next data item if more
     * data is available or to the end of the list.
     *
     * Does nothing if the iterator is already at the end
     * of the list.
     */
    public void advance() {
        if (node == null)
            return;
        
        if (index < node.getCount()) {
            index++;
            return;
        }
        
        node = node.getNext();
        index = 0;
    }
}