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 * @author  Tomáš Müller
018 * @version IFS 1.3 (Iterative Forward Search)<br>
019 *          Copyright (C) 2014 Tomáš Müller<br>
020 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
021 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
022 * <br>
023 *          This library is free software; you can redistribute it and/or modify
024 *          it under the terms of the GNU Lesser General Public License as
025 *          published by the Free Software Foundation; either version 3 of the
026 *          License, or (at your option) any later version. <br>
027 * <br>
028 *          This library is distributed in the hope that it will be useful, but
029 *          WITHOUT ANY WARRANTY; without even the implied warranty of
030 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
031 *          Lesser General Public License for more details. <br>
032 * <br>
033 *          You should have received a copy of the GNU Lesser General Public
034 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
035 * @param <V> Variable
036 * @param <T> Value
037 **/
038public class DefaultSingleAssignmentContextHolder<V extends Variable<V, T>, T extends Value<V, T>> extends AssignmentContextHolderMap<V, T> {
039
040    public DefaultSingleAssignmentContextHolder() {
041    }
042    
043    @Override
044    @SuppressWarnings("unchecked")
045    public <U extends AssignmentContext> U getAssignmentContext(Assignment<V, T> assignment, AssignmentContextReference<V, T, U> reference) {
046        if (reference.getParent() instanceof CanHoldContext) {
047            AssignmentContext[] contexts = ((CanHoldContext)reference.getParent()).getContext();
048            if (contexts[0] == null)
049                contexts[0] = reference.getParent().createAssignmentContext(assignment);
050            return (U)contexts[0];
051        } else {
052            return super.getAssignmentContext(assignment, reference);
053        }
054    }
055    
056    @Override
057    public <C extends AssignmentContext> void clearContext(AssignmentContextReference<V, T, C> reference) {
058        if (reference.getParent() instanceof CanHoldContext) {
059            AssignmentContext[] contexts = ((CanHoldContext)reference.getParent()).getContext();
060            contexts[0] = null;
061        } else {
062            super.clearContext(reference);
063        }
064    }
065}