/*
 *                    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 09.05.2004
 * @author Andreas Prlic
 *
 */

package org.biojava.nbio.structure;

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


/** An iterator over all groups of a structure.
 * @author Andreas Prlic
 * @since 1.4
 * @version %I% %G%
 */

public class GroupIterator implements Iterator<Group> {

        Structure structure   ;
        int current_model_pos ;
        int current_chain_pos ;
        int current_group_pos ;

        /**
         * Constructs a GroupIterator object.
         *
         * @param struct  a Structure object
         */

        public GroupIterator (Structure struct) {
                structure = struct     ;
                current_model_pos = 0  ;
                current_chain_pos = 0  ;
                current_group_pos = -1 ;

        }


        /** needed to do a copy of iterator ... */
        private Structure getStructure() { return structure         ;}
        private int  getModelPos()       { return current_model_pos ;}
        private void setModelPos(int pos){ current_model_pos = pos  ;}
        private int  getChainPos()       { return current_chain_pos ;}
        private void setChainPos(int pos){ current_chain_pos = pos  ;}
        private int  getGroupPos()       { return current_group_pos ;}
        private void setGroupPos(int pos){ current_group_pos = pos  ;}

        /**  Creates and returns a copy of this object. */
        @Override
        public Object clone () {

                GroupIterator gr = new GroupIterator(this.getStructure()) ;
                gr.setModelPos(this.getModelPos());
                gr.setChainPos(this.getChainPos());
                gr.setGroupPos(this.getGroupPos());
                return gr ;

        }


        /** is there a group after the current one in the structure? */
        @Override
        public boolean hasNext() {
                return hasSubGroup(current_model_pos,current_chain_pos , current_group_pos +1) ;
        }

        /** recursive method to determine if there is a next group. Helper
         * method for hasNext().
         * @see #hasNext
         */
        private boolean hasSubGroup(int tmp_model,int tmp_chain,int tmp_group) {

                if (tmp_model >= structure.nrModels()) {
                        return false;
                }

                List<Chain> model = structure.getModel(tmp_model);

                if (tmp_chain >= model.size()) {
                        return hasSubGroup(tmp_model + 1, 0, 0);
                }

                Chain chain = model.get(tmp_chain);

                // start search at beginning of next chain.
                return tmp_group < chain.getAtomLength() || hasSubGroup(tmp_model, tmp_chain + 1, 0);

        }

        /** Get the model number of the current model.
         *
         * @return the number of the model
         */
        public int getCurrentModel(){

                return current_model_pos;
        }

        /** Get the current Chain. Returns null if we are at the end of the iteration.
         *
         * @return the Chain of the current position
         */
        public Chain getCurrentChain(){
                if ( current_model_pos >= structure.nrModels()){
                        return null;
                }

                List<Chain> model =  structure.getModel(current_model_pos);

                if ( current_chain_pos >= model.size() ){
                        return null;
                }

                return model.get(current_chain_pos);

        }

        /** get next Group.
         * @return next Group
         * @throws NoSuchElementException ...
         */
        @Override
        public Group next()
        throws NoSuchElementException
        {

                return getNextGroup(current_model_pos,current_chain_pos,current_group_pos+1);
        }

        /** recursive method to retrieve the next group. Helper
         * method for gext().
         * @see #next
         */
        private Group getNextGroup(int tmp_model,int tmp_chain,int tmp_group)
        throws NoSuchElementException
        {

                if ( tmp_model >= structure.nrModels()){
                        throw new NoSuchElementException("arrived at end of structure!");
                }

                List<Chain> model = structure.getModel(tmp_model);

                if ( tmp_chain >= model.size() ){
                        return getNextGroup(tmp_model+1,0,0);
                }

                Chain     chain = model.get(tmp_chain);

                if (tmp_group  >= chain.getAtomLength()){
                        // start search at beginning of next chain.
                        return getNextGroup(tmp_model,tmp_chain+1,0);
                } else {
                        current_model_pos = tmp_model;
                        current_chain_pos = tmp_chain;
                        current_group_pos = tmp_group;
                        return chain.getAtomGroup(current_group_pos);
                }

        }

        /** does nothing .
         */
        @Override
        public void remove() {
                throw new UnsupportedOperationException("Cannot call remove() for GroupIterator");
        }


}