/*
 *                    BioJava development code
 *
 * This code may be freely distributed and modified under the
 * terms of the GNU Lesser General Public Licence.  This should
 * be distributed with the code.  If you do not have a copy,
 * see:
 *
 *      http://www.gnu.org/copyleft/lesser.html
 *
 * Copyright for this code is held jointly by the individual
 * authors.  These should be listed in @author doc comments.
 *
 * For more information on the BioJava project and its aims,
 * or to join the biojava-l mailing list, visit the home page
 * at:
 *
 *      http://www.biojava.org/
 *
 * Created on 24.05.2004
 * @author Andreas Prlic
 *
 */

package org.biojava.bio.structure;

import java.util.Iterator;
import java.util.NoSuchElementException;


/** an iterator over all atoms of a structure / group. 
 * @author Andreas Prlic
 * @since 1.4
 * @version %I% %G%
 */

public class AtomIterator implements Iterator<Atom> {
	Structure structure     ;
	Group     group         ;
	int current_atom_pos    ;
	GroupIterator groupiter ;

	/**
	 * Constructs an AtomIterator object.
	 *
	 * @param struct  a Structure object
	 */
	public AtomIterator(Structure struct) {
		structure = struct;
		current_atom_pos = -1 ;

		groupiter = new GroupIterator(structure) ;
		if ( groupiter.hasNext() ) {
			group = (Group) groupiter.next() ;
		}
		else 
			group = null ;
	}

	/** Get the  chain that contains the current atom.
	 * 
	 * @return a Chain object
	 */
	public Chain getCurrentChain(){
		return groupiter.getCurrentChain();
	}


	/** Get the model number of the model containing the current atom.
	 * 
	 * @return the number of the model
	 */
	public int getCurrentModel(){
		return groupiter.getCurrentModel();
	}

	/**
	 * Constructs an AtomIterator object.
	 *
	 * @param g  a Group object
	 */
	public AtomIterator(Group g) {
		structure = null;
		group = g ;
		current_atom_pos = -1 ;
		groupiter = null ;


	}

	/** Is there a next atom ?
	 * @return true if there is an atom after the current one 
	 * */
	public boolean hasNext() {

		// trying to iterate over an empty structure...

		if ( group == null)
			return false;

		// if there is another group ...
		if ( current_atom_pos < group.size()-1 ) {	    
			return true ;
		} else { 
			// search through the next groups if they contain an atom
			if (groupiter != null) {
				GroupIterator tmp = (GroupIterator) groupiter.clone() ;
				while (tmp.hasNext()) {
					Group tmpg = (Group) tmp.next() ;

					if ( tmpg.size() > 0 ) {
						return true ;
					}

				}
			} else {
				// just an iterator over one group ...
				return false ;
			}
		}
		return false ;
	}

	/** Return next atom.
	 *
	 * @return the next Atom
	 * @throws NoSuchElementException if there is no atom after the current one
	 */
	public Atom next() 
	throws NoSuchElementException
	{
		current_atom_pos++ ;
		if ( current_atom_pos >= group.size() ) {
			if ( groupiter == null ) {
				throw new NoSuchElementException("no more atoms found in group!");

			}
			if ( groupiter.hasNext() ) {
				group = (Group) groupiter.next() ;
				current_atom_pos = -1 ;
				return next();
			} else {
				throw new NoSuchElementException("no more atoms found in structure!");
			}
		} 

		Atom a ;

		try {
			a = group.getAtom(current_atom_pos);
		} catch (StructureException e) {
			System.err.println("current_atom_pos " + current_atom_pos + " group " + group + "size:" + group.size());
			e.printStackTrace();
			throw new NoSuchElementException("error wile trying to retrieve atom");
		}

		return a ;

	}

	/** does nothing. */
	public void remove() {
	}

}