001package org.cpsolver.ifs.assignment.context;
002
003import org.cpsolver.ifs.assignment.Assignment;
004import org.cpsolver.ifs.assignment.DefaultSingleAssignment;
005import org.cpsolver.ifs.model.Value;
006import org.cpsolver.ifs.model.Variable;
007
008/**
009 * A simple assignment context holder implementation used by the {@link DefaultSingleAssignment} class.
010 * {@link CanHoldContext} are used when possible, storing contexts in arrays of length 1 (one context per
011 * {@link HasAssignmentContext} class).
012 * 
013 * @see AssignmentContext
014 * @see AssignmentContextReference
015 * @see AssignmentContextHolder
016 * 
017 * @version IFS 1.3 (Iterative Forward Search)<br>
018 *          Copyright (C) 2014 Tomas Muller<br>
019 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
020 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
021 * <br>
022 *          This library is free software; you can redistribute it and/or modify
023 *          it under the terms of the GNU Lesser General Public License as
024 *          published by the Free Software Foundation; either version 3 of the
025 *          License, or (at your option) any later version. <br>
026 * <br>
027 *          This library is distributed in the hope that it will be useful, but
028 *          WITHOUT ANY WARRANTY; without even the implied warranty of
029 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
030 *          Lesser General Public License for more details. <br>
031 * <br>
032 *          You should have received a copy of the GNU Lesser General Public
033 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
034 * @param <V> Variable
035 * @param <T> Value
036 **/
037public class DefaultSingleAssignmentContextHolder<V extends Variable<V, T>, T extends Value<V, T>> extends AssignmentContextHolderMap<V, T> {
038
039    public DefaultSingleAssignmentContextHolder() {
040    }
041    
042    @Override
043    @SuppressWarnings("unchecked")
044    public <U extends AssignmentContext> U getAssignmentContext(Assignment<V, T> assignment, AssignmentContextReference<V, T, U> reference) {
045        if (reference.getParent() instanceof CanHoldContext) {
046            CanHoldContext holder = (CanHoldContext)reference.getParent();
047            AssignmentContext[] contexts = holder.getContext();
048            if (contexts != null)
049                return (U) contexts[0];
050            
051            U context = reference.getParent().createAssignmentContext(assignment);
052            holder.setContext(new AssignmentContext[] {context});
053
054            return context;
055        } else {
056            return super.getAssignmentContext(assignment, reference);
057        }
058    }
059    
060    @Override
061    public <C extends AssignmentContext> void clearContext(AssignmentContextReference<V, T, C> reference) {
062        if (reference.getParent() instanceof CanHoldContext) {
063            CanHoldContext holder = (CanHoldContext)reference.getParent();
064            holder.setContext(null);
065        } else {
066            super.clearContext(reference);
067        }
068    }
069}