001 package net.sf.cpsolver.studentsct.constraint;
002
003 import java.util.Enumeration;
004 import java.util.Set;
005 import java.util.Vector;
006
007 import net.sf.cpsolver.ifs.model.Constraint;
008 import net.sf.cpsolver.ifs.model.Value;
009 import net.sf.cpsolver.ifs.util.ToolBox;
010 import net.sf.cpsolver.studentsct.model.CourseRequest;
011 import net.sf.cpsolver.studentsct.model.Enrollment;
012 import net.sf.cpsolver.studentsct.model.Student;
013
014 /**
015 * Abstract reservation constraint. This constraint allow some section, courses, and other
016 * parts to be reserved to particular group of students. A reservation can be unlimited
017 * (any number of students of that particular group can attend a course, section, etc.) or
018 * with a limit (only given number of seats is reserved to the students of the particular
019 * group).
020 *
021 * <br><br>
022 *
023 * @version
024 * StudentSct 1.1 (Student Sectioning)<br>
025 * Copyright (C) 2007 Tomáš Müller<br>
026 * <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
027 * Lazenska 391, 76314 Zlin, Czech Republic<br>
028 * <br>
029 * This library is free software; you can redistribute it and/or
030 * modify it under the terms of the GNU Lesser General Public
031 * License as published by the Free Software Foundation; either
032 * version 2.1 of the License, or (at your option) any later version.
033 * <br><br>
034 * This library is distributed in the hope that it will be useful,
035 * but WITHOUT ANY WARRANTY; without even the implied warranty of
036 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
037 * Lesser General Public License for more details.
038 * <br><br>
039 * You should have received a copy of the GNU Lesser General Public
040 * License along with this library; if not, write to the Free Software
041 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
042 */
043 public abstract class Reservation extends Constraint {
044 /** Student cannot be enrolled */
045 public static int CAN_ENROLL_NO = 0;
046 /** Student can be enrolled */
047 public static int CAN_ENROLL_YES = 1;
048 /** Student can be enrolled, however, some other student has to dropped out of the section, course, etc. */
049 public static int CAN_ENROLL_INSTEAD = 2;
050
051 /**
052 * Check, whether a student can be enrolled into the given section, course, etc.
053 * @param student given student
054 * @return {@link Reservation#CAN_ENROLL_YES}, {@link Reservation#CAN_ENROLL_NO}, or {@link Reservation#CAN_ENROLL_INSTEAD}
055 */
056 public abstract int canEnroll(Student student);
057
058 /**
059 * Check whether the given student can be enrolled instead of another student
060 * @param student student that is to be enrolled in the particular course, section, etc.
061 * @param insteadOfStudent student, that is currently enrolled, which is going to be
062 * bumped out of the course, section, etc. in order to enroll given studen
063 * @return true, if the move is permitted
064 */
065 public abstract boolean canEnrollInstead(Student student, Student insteadOfStudent);
066
067 /**
068 * Check whether the reservation is applicable to the given enrollment.
069 * This means that the given enrollment contains the particular section, course, etc.
070 * @param enrollment enrollment of a student that is being considered
071 * @return true, if the reservation applies to the enrollment
072 */
073 public abstract boolean isApplicable(Enrollment enrollment);
074
075 /**
076 * Implementation of the constraint primitives.
077 * See {@link Constraint#computeConflicts(Value, Set)} for more details.
078 */
079 public void computeConflicts(Value value, Set conflicts) {
080 Enrollment enrollment = (Enrollment)value;
081
082 if (!isApplicable(enrollment)) return;
083
084 int ce = canEnroll(enrollment.getStudent());
085
086 if (ce==CAN_ENROLL_YES) return;
087
088 if (ce==CAN_ENROLL_NO) {
089 // Unable to bump out some other student
090 conflicts.add(enrollment);
091 return;
092 }
093
094 // Try other bump out some other student
095 Vector conflictEnrollments = null;
096 double conflictValue = 0;
097 for (Enumeration e=assignedVariables().elements();e.hasMoreElements();) {
098 CourseRequest request = (CourseRequest) e.nextElement();
099 if (canEnrollInstead(enrollment.getStudent(),request.getStudent())) {
100 if (conflictEnrollments==null || conflictValue>enrollment.toDouble()) {
101 if (conflictEnrollments==null)
102 conflictEnrollments = new Vector();
103 else
104 conflictEnrollments.clear();
105 conflictEnrollments.add(request.getAssignment());
106 conflictValue = request.getAssignment().toDouble();
107 }
108 }
109 }
110 if (conflictEnrollments!=null && !conflictEnrollments.isEmpty()) {
111 conflicts.add(ToolBox.random(conflictEnrollments));
112 return;
113 }
114
115 // Unable to bump out some other student
116 conflicts.add(enrollment);
117 }
118
119 /**
120 * Implementation of the constraint primitives.
121 * See {@link Constraint#inConflict(Value)} for more details.
122 */
123 public boolean inConflict(Value value) {
124 Enrollment enrollment = (Enrollment)value;
125
126 if (!isApplicable(enrollment)) return false;
127
128 return canEnroll(enrollment.getStudent())!=CAN_ENROLL_YES;
129 }
130
131 }