/*
    * #%L
    * prolobjectlink-jpi-jtrolog
    * %%
    * Copyright (C) 2012 - 2018 WorkLogic Project
    * %%
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as
    * published by the Free Software Foundation, either version 2.1 of the
   * License, or (at your option) any later version.
   * 
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Lesser Public License for more details.
   * 
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-2.1.html>.
   * #L%
   */
  package jTrolog.terms;
  
  import jTrolog.parser.Parser;
  
  import java.util.Iterator;
  
  /**
   * @author ivar.orstavik@hist.no
   */
  @SuppressWarnings({ "rawtypes" })
  class ListIterator implements Iterator {
  
  	Term hereIAmBaby;
  
  	public ListIterator(Struct origin) {
  		hereIAmBaby = origin;
  	}
  
  	public boolean hasNext() {
  		return hereIAmBaby != null;
  	}
  
  	public Object next() {
  		if (hereIAmBaby == null)
  			throw new IndexOutOfBoundsException("iterating out of list");
  		if (hereIAmBaby.equals(Term.emptyList)) {
  			hereIAmBaby = null;
  			return Term.emptyList;
  		}
  		if (hereIAmBaby instanceof Struct && ((Struct) hereIAmBaby).predicateIndicator == Parser.listSignature) {
  			Term timeToDeliver = ((Struct) hereIAmBaby).getArg(0);
  			hereIAmBaby = ((Struct) hereIAmBaby).getArg(1);
  			return timeToDeliver;
  		}
  		Term ImYours = hereIAmBaby;
  		hereIAmBaby = null;
  		return ImYours;
  	}
  
  	public void remove() {
  		throw new UnsupportedOperationException("don't delete on List iteration");
  	}
  }