001package org.cpsolver.ifs.assignment.context;
002
003import org.cpsolver.ifs.assignment.Assignment;
004import org.cpsolver.ifs.model.BinaryConstraint;
005import org.cpsolver.ifs.model.Model;
006import org.cpsolver.ifs.model.Value;
007import org.cpsolver.ifs.model.Variable;
008
009/**
010 * A binary constraint with an assignment context. This is a variant of the {@link ConstraintWithContext} that extends the
011 * {@link BinaryConstraint} class.
012 * 
013 * 
014 * @see AssignmentContext
015 * 
016 * @author  Tomáš Müller
017 * @version IFS 1.3 (Iterative Forward Search)<br>
018 *          Copyright (C) 2014 Tomáš Müller<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 * @param <C> Assignment Context
037 **/
038public abstract class BinaryConstraintWithContext<V extends Variable<V, T>, T extends Value<V, T>, C extends AssignmentConstraintContext<V, T>> extends BinaryConstraint<V, T> implements HasAssignmentContext<V, T, C>, CanHoldContext {
039    private AssignmentContextReference<V, T, C> iContextReference = null;
040    private AssignmentContext[] iContext = new AssignmentContext[CanHoldContext.sMaxSize];
041    
042    public BinaryConstraintWithContext() {
043        super();
044    }
045    
046    @Override
047    public void setModel(Model<V, T> model) {
048        super.setModel(model);
049        if (model != null)
050            iContextReference = model.createReference(this);
051    }
052    
053    /**
054     * Returns an assignment context associated with this constraint. If there is no 
055     * assignment context associated with this constraint yet, one is created using the
056     * {@link ConstraintWithContext#createAssignmentContext(Assignment)} method. From that time on,
057     * this context is kept with the assignment and automatically updated by calling the
058     * {@link AssignmentConstraintContext#assigned(Assignment, Value)} and {@link AssignmentConstraintContext#unassigned(Assignment, Value)}
059     * whenever a variable of this constraint is changed.
060     * @param assignment given assignment
061     * @return assignment context associated with this constraint and the given assignment
062     */
063    @Override
064    public C getContext(Assignment<V, T> assignment) {
065        return AssignmentContextHelper.getContext(this, assignment);
066    }
067
068    @Override
069    public AssignmentContextReference<V, T, C> getAssignmentContextReference() { return iContextReference; }
070
071    @Override
072    public void setAssignmentContextReference(AssignmentContextReference<V, T, C> reference) { iContextReference = reference; }
073
074    @Override
075    public AssignmentContext[] getContext() { return iContext; }
076    
077    @Override
078    public void assigned(Assignment<V, T> assignment, long iteration, T value) {
079        super.assigned(assignment, iteration, value);
080        getContext(assignment).assigned(assignment, value);
081    }
082    
083    @Override
084    public void unassigned(Assignment<V, T> assignment, long iteration, T value) {
085        super.unassigned(assignment, iteration, value);
086        getContext(assignment).unassigned(assignment, value);
087    }
088}