001package org.cpsolver.ifs.assignment.context;
002
003import org.cpsolver.ifs.assignment.Assignment;
004import org.cpsolver.ifs.model.Constraint;
005import org.cpsolver.ifs.model.Model;
006import org.cpsolver.ifs.model.Value;
007import org.cpsolver.ifs.model.Variable;
008
009/**
010 * A constraint with an assignment context. In order to be able to hold multiple assignments in memory
011 * it is desired for all the assignment dependent data a constraint may need (to effectively enumerate
012 * conflicting values), to store these data in a separate class (implementing the 
013 * {@link AssignmentConstraintContext} interface). This context is created by calling
014 * {@link ConstraintWithContext#createAssignmentContext(Assignment)} and accessed by
015 * {@link ConstraintWithContext#getContext(Assignment)}.
016 * 
017 * 
018 * @see AssignmentContext
019 * 
020 * @author  Tomáš Müller
021 * @version IFS 1.3 (Iterative Forward Search)<br>
022 *          Copyright (C) 2014 Tomáš Müller<br>
023 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
024 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
025 * <br>
026 *          This library is free software; you can redistribute it and/or modify
027 *          it under the terms of the GNU Lesser General Public License as
028 *          published by the Free Software Foundation; either version 3 of the
029 *          License, or (at your option) any later version. <br>
030 * <br>
031 *          This library is distributed in the hope that it will be useful, but
032 *          WITHOUT ANY WARRANTY; without even the implied warranty of
033 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
034 *          Lesser General Public License for more details. <br>
035 * <br>
036 *          You should have received a copy of the GNU Lesser General Public
037 *          License along with this library; if not see <a href='http://www.gnu.org/licenses'>http://www.gnu.org/licenses</a>.
038 * @param <V> Variable
039 * @param <T> Value
040 * @param <C> Assignment Context
041 **/
042public abstract class ConstraintWithContext<V extends Variable<V, T>, T extends Value<V, T>, C extends AssignmentConstraintContext<V, T>> extends Constraint<V, T> implements HasAssignmentContext<V, T, C>, CanHoldContext {
043    private AssignmentContextReference<V, T, C> iContextReference = null;
044    private AssignmentContext[] iContext = new AssignmentContext[CanHoldContext.sMaxSize];
045    
046    public ConstraintWithContext() {
047        super();
048    }
049    
050    @Override
051    public void setModel(Model<V, T> model) {
052        super.setModel(model);
053        if (model != null)
054            iContextReference = model.createReference(this);
055    }
056    
057    /**
058     * Returns an assignment context associated with this constraint. If there is no 
059     * assignment context associated with this constraint yet, one is created using the
060     * {@link ConstraintWithContext#createAssignmentContext(Assignment)} method. From that time on,
061     * this context is kept with the assignment and automatically updated by calling the
062     * {@link AssignmentConstraintContext#assigned(Assignment, Value)} and {@link AssignmentConstraintContext#unassigned(Assignment, Value)}
063     * whenever a variable of this constraint is changed.
064     * @param assignment given assignment
065     * @return assignment context associated with this constraint and the given assignment
066     */
067    @Override
068    public C getContext(Assignment<V, T> assignment) {
069        return AssignmentContextHelper.getContext(this, assignment);
070    }
071
072    @Override
073    public AssignmentContextReference<V, T, C> getAssignmentContextReference() { return iContextReference; }
074
075    @Override
076    public void setAssignmentContextReference(AssignmentContextReference<V, T, C> reference) { iContextReference = reference; }
077
078    @Override
079    public AssignmentContext[] getContext() { return iContext; }
080
081    @Override
082    public void assigned(Assignment<V, T> assignment, long iteration, T value) {
083        super.assigned(assignment, iteration, value);
084        getContext(assignment).assigned(assignment, value);
085    }
086    
087    @Override
088    public void unassigned(Assignment<V, T> assignment, long iteration, T value) {
089        super.unassigned(assignment, iteration, value);
090        getContext(assignment).unassigned(assignment, value);
091    }
092}