001    /*
002     *  www.ti.bfh.ch
003     *
004     *  Copyright 2007, Berne University of Applied Sciences, 
005     *  School of Engineering and Information Technology
006     *  and individual contributors as indicated by the @authors tag.
007     *
008     *  This is free software; you can redistribute it and/or modify it under the terms of the 
009     *  GNU Lesser General Public License as published by the Free Software Foundation; 
010     *  either version 3 of the License, or (at your option) any later version.
011     *
012     *  This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
013     *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
014     *  See the GNU Lesser General Public License for more details.
015     *
016     *  You should have received a copy of the GNU Lesser General Public License along with this software; 
017     *  if not, see <http://www.gnu.org/licenses/>.
018     *
019     */
020    package ch.bfh.algo.core.sequence;
021    
022    
023    
024    public class LinkedCursor<E,P extends GenericLinkedPosition<E,P>> implements Observer{
025    
026            private P previous;
027        private P next;
028        
029        private ObserverPosition before;
030        private ObserverPosition after;
031        
032        public LinkedCursor(P previous, P next){
033                    this.previous=previous;
034                    this.next=next;
035                    this.attach();
036        }
037        
038        public P getPrevious(){
039            return this.previous;
040        }
041        
042        public P getNext(){
043            return this.next;
044        }
045        
046        public void attach(){
047                    this.before=this.previous.attachAfter(this);
048                    this.after=this.next.attachBefore(this);
049        }
050        
051        public void detach(){
052                    this.previous.detachAfter(this.before);
053                    this.next.detachBefore(this.after);
054        }
055        
056        public void moveNext(){
057            this.detach();
058            this.previous=this.next;
059            this.next=this.next.getNext();
060            this.attach();
061        }
062        
063        public void movePrevious(){
064            this.detach();
065            this.next=this.previous;
066            this.previous=this.previous.getPrevious();
067            this.attach();
068        }
069        
070            public void updateBefore(){             
071                    this.previous.detachAfter(this.before);
072                    this.previous=this.next.getPrevious();
073                    this.before=this.previous.attachAfter(this);
074            }
075            
076            public void updateAfter(){
077                    this.next.detachBefore(this.after);
078                    this.next=this.previous.getNext();
079                    this.after=this.next.attachBefore(this);
080            }
081    }