001package org.cpsolver.studentsct.constraint;
002
003import java.util.Set;
004
005import org.cpsolver.ifs.assignment.Assignment;
006import org.cpsolver.ifs.model.GlobalConstraint;
007import org.cpsolver.studentsct.model.CourseRequest;
008import org.cpsolver.studentsct.model.Enrollment;
009import org.cpsolver.studentsct.model.Request;
010
011/**
012 * Fixed assignment constraint. This global constraint checks that the 
013 * conflicts that have been computed so far (by other global constraints earlier
014 * in the list) do not create a conflict with a fixed assignment. This constraint
015 * is to be used only when there are fixed course requests and it is to be last global constraint
016 * in the list.
017 * 
018 * @author  Tomáš Müller
019 * @version StudentSct 1.3 (Student Sectioning)<br>
020 *          Copyright (C) 2007 - 2015 Tomáš Müller<br>
021 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
022 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
023 * <br>
024 *          This library is free software; you can redistribute it and/or modify
025 *          it under the terms of the GNU Lesser General Public License as
026 *          published by the Free Software Foundation; either version 3 of the
027 *          License, or (at your option) any later version. <br>
028 * <br>
029 *          This library is distributed in the hope that it will be useful, but
030 *          WITHOUT ANY WARRANTY; without even the implied warranty of
031 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
032 *          Lesser General Public License for more details. <br>
033 * <br>
034 *          You should have received a copy of the GNU Lesser General Public
035 *          License along with this library; if not see
036 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
037 */
038public class FixedAssignments extends GlobalConstraint<Request, Enrollment> {
039
040    /**
041     * If there is a conflict that is fixed (method {@link CourseRequest#isFixed()} returns true)
042     * and equal to the initial assignment (returned by {@link CourseRequest#getFixedValue()}),
043     * the given enrollment is put into the conflicts.
044     */
045    @Override
046    public void computeConflicts(Assignment<Request, Enrollment> assignment, Enrollment enrollment, Set<Enrollment> conflicts) {
047        for (Enrollment conflict: conflicts) {
048            if (conflict.getRequest() instanceof CourseRequest) {
049                CourseRequest cr = (CourseRequest)conflict.getRequest();
050                if (cr.isFixed() && conflict.equals(cr.getFixedValue())) {
051                    conflicts.add(enrollment);
052                    return;
053                }
054            }
055        }
056    }
057}