// @(#) $Id: TwoWayNode.jml-refined,v 1.11 2007/07/01 02:38:46 chalin Exp $

// Copyright (C) 1998, 1999 Iowa State University

// This file is part of JML

// JML is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.

// JML 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 Public License for more details.

// You should have received a copy of the GNU General Public License
// along with JML; see the file COPYING.  If not, write to
// the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

// Author:  Clyde Ruby

package org.jmlspecs.samples.list.node2;

//@ model import org.jmlspecs.models.JMLObjectSequence;

public class TwoWayNode extends OneWayNode { // Doubly Linked Node

  // data members

  /*@ public model non_null JMLObjectSequence prevEntries;
    @                         in entries;
    @ public model nullable TwoWayNode nextDL;
    @                         in nextNode;
    @*/

  //@ public invariant (nextNode == null || nextNode instanceof TwoWayNode);
  //@ public represents nextDL <- (TwoWayNode) nextNode;

  /*@ public model nullable TwoWayNode prevNode;
    @                         in prevEntries;
    @*/

  /*@ public normal_behavior
    @   assignable entries;
    @   ensures theEntry == ent &&  entries.itemAt(0) == ent 
    @       && entries.int_size() == 1 &&  prevEntries.isEmpty()
    @       && allButFirst.isEmpty();
    @*/
    public TwoWayNode(/*@ nullable @*/ Object ent);

  /*@ also
    @ public normal_behavior
    @   assignable allButFirst;
    @   ensures \not_modified(prevEntries);
    @*/
    public void insertAfter(/*@ nullable @*/ Object newEntry);

  /*@ also
    @ public normal_behavior
    @   assignable allButFirst;
    @   ensures \not_modified(prevEntries);
    @*/
    public void removeNextNode();

  /*@ public normal_behavior
    @   assignable \nothing;
    @   ensures \result == prevNode;
    @*/
    public /*@ nullable @*/ TwoWayNode getPrevNode();

  /*@ public normal_behavior
    @    requires prevNode != null;
    @    assignable \nothing;
    @    ensures \result.node == this;
    @ also
    @    requires prevNode == null;
    @    assignable \nothing;
    @    ensures \result == null;
    @*/
    public /*@ pure nullable @*/ DualLink getPrevLink();

  /*@ public normal_behavior
    @    requires nextNode == null;
    @    assignable prevEntries;
    @    ensures prevEntries.equals(\old(prevEntries).insertBack(newEntry));
    @ also public normal_behavior
    @    requires nextNode != null;
    @    assignable prevEntries;
    @    ensures prevEntries.equals(\old(prevEntries).insertBack(newEntry)) 
    @        && \not_modified(allButFirst);
    @*/
    public void insertBefore(/*@ nullable @*/ Object newEntry);

}