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.Config;
008import org.cpsolver.studentsct.model.Enrollment;
009import org.cpsolver.studentsct.model.Request;
010import org.cpsolver.studentsct.model.Section;
011import org.cpsolver.studentsct.reservation.Reservation;
012
013
014/**
015 * Disabled sections constraint. This global constraint ensures that no enrollment
016 * containing a disabled sections (using {@link Section#isEnabled()}) is used, unless
017 * there is a reservation allowing for the use of disabled sections
018 * (using {@link Reservation#isAllowDisabled()}).
019 * 
020 * @author  Tomáš Müller
021 * @version StudentSct 1.3 (Student Sectioning)<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
038 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
039 */
040public class DisabledSections extends GlobalConstraint<Request, Enrollment> {
041    
042    /**
043     * A given enrollment is conflicting, if there is a section that
044     * is disabled and there is not a matching reservation that would allow for that.
045     * 
046     * @param enrollment {@link Enrollment} that is being considered
047     * @param conflicts all computed conflicting requests are added into this set
048     */
049    @Override
050    public void computeConflicts(Assignment<Request, Enrollment> assignment, Enrollment enrollment, Set<Enrollment> conflicts) {
051        if (inConflict(assignment, enrollment))
052            conflicts.add(enrollment);
053    }
054    
055    /**
056     * A given enrollment is conflicting, if there is a section that
057     * is disabled and there is not a matching reservation that would allow for that.
058     * 
059     * @param enrollment {@link Enrollment} that is being considered
060     * @return true, if the enrollment does not follow a reservation that must be used 
061     */
062    @Override
063    public boolean inConflict(Assignment<Request, Enrollment> assignment, Enrollment enrollment) {
064        // enrollment's config
065        Config config = enrollment.getConfig();
066
067        // exclude free time requests
068        if (config == null) return false;
069        
070        // student allows for disabled sections >> no problem
071        if (enrollment.getStudent().isAllowDisabled()) return false;
072        
073        boolean hasDisabledSection = false;
074        // check all sections of the given enrollment
075        for (Section section: enrollment.getSections())
076            if (!section.isEnabled(enrollment.getStudent())) {
077                hasDisabledSection = true;
078                break;
079            }
080        
081        // no disabled section >> no conflict
082        if (!hasDisabledSection) return false;
083        
084        // no reservations >> conflict not allowed
085        if (!config.getOffering().hasReservations())
086            return true;
087        
088        // enrollment's reservation
089        Reservation reservation = enrollment.getReservation();
090        
091        // already has a reservation that all for disabled sections
092        if (reservation != null && reservation.isAllowDisabled()) return false;
093        
094        // if a there is some other reservation that allows for disabled sections >> also fine
095        for (Reservation r: config.getOffering().getReservations())
096            if (r.isAllowDisabled() && r.isApplicable(enrollment.getStudent()) && r.isIncluded(enrollment))
097                return false;
098        
099        return true;
100    }
101    
102    @Override
103    public String toString() {
104        return "DisabledSections";
105    }
106}