001package org.cpsolver.coursett.constraint;
002
003import java.util.ArrayList;
004import java.util.BitSet;
005import java.util.Collections;
006import java.util.HashMap;
007import java.util.HashSet;
008import java.util.List;
009import java.util.Set;
010import java.util.regex.Matcher;
011import java.util.regex.Pattern;
012
013import org.cpsolver.coursett.Constants;
014import org.cpsolver.coursett.model.Lecture;
015import org.cpsolver.coursett.model.Placement;
016import org.cpsolver.ifs.assignment.Assignment;
017import org.cpsolver.ifs.util.ToolBox;
018
019
020/**
021 * 
022 * The Break constraint checks for instructor lunch break or a break in general in between the given classes.<br>
023 * It has three parameters: a start and an end time of a window in which the break is required / preferred, and a minimal length of a break that is needed.<br>
024 * Reference _Break:132:162:30_ translates to a break of at least 30 minutes between 11 am (slot 132) and 1:30 pm (slot 162).<br>
025 * 
026 * @version CourseTT 1.3 (University Course Timetabling)<br>
027 *          Copyright (C) 2013 Matej Lukac<br>
028 * <br>
029 *          This library is free software; you can redistribute it and/or modify
030 *          it under the terms of the GNU Lesser General Public License as
031 *          published by the Free Software Foundation; either version 3 of the
032 *          License, or (at your option) any later version. <br>
033 * <br>
034 *          This library is distributed in the hope that it will be useful, but
035 *          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. <br>
038 * <br>
039 *          You should have received a copy of the GNU Lesser General Public
040 *          License along with this library; if not see
041 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
042 */
043public class BreakFlexibleConstraint extends FlexibleConstraint {
044    
045    // LunchBreak constraint parameters
046    private int iBreakStart;
047    private int iBreakEnd;
048    private int iBreakLength;
049
050    /**
051     * 
052     * @param id constraint unique id
053     * @param owner identifier of distribution preference the constraint was created for
054     * @param preference time preference ("R" for required, "P" for prohibited, "-2",
055     *            "-1", "1", "2" for soft preference)   
056     * @param reference parameters of the constraint in String form            
057     */
058    public BreakFlexibleConstraint(Long id, String owner, String preference, String reference) {
059        super(id, owner, preference, reference);     
060        
061        Pattern pattern = null;
062        Matcher matcher = null;   
063        
064        // recognize Break constraint        
065        String patternString = "_(Break):([0-9]+):([0-9]+):([0-9]+)_";
066        pattern = Pattern.compile(patternString);
067        matcher = pattern.matcher(reference);
068        if (matcher.find()) {                
069            iBreakStart = Integer.parseInt(matcher.group(2));
070            iBreakEnd = Integer.parseInt(matcher.group(3)); 
071            iBreakLength = Integer.parseInt(matcher.group(4))/Constants.SLOT_LENGTH_MIN; 
072            iConstraintType = FlexibleConstraintType.BREAK;           
073        }   
074    }
075
076    @Override
077    public void computeConflicts(Assignment<Lecture, Placement> assignment, Placement value, Set<Placement> conflicts) {
078        if (!isHard())
079            return;        
080        
081        List<BitSet> weeks = getWeeks();
082       
083        // checks only placements in the break time
084        if (value.getTimeLocation().getStartSlot() <= iBreakEnd
085                && value.getTimeLocation().getStartSlot() + value.getTimeLocation().getLength() > iBreakStart) {
086            
087            for (int dayCode : Constants.DAY_CODES) {
088                // checks only days affected by the placement
089                if ((value.getTimeLocation().getDayCode() & dayCode) != 0) {             
090                    // constraint is checked for every week in semester (or for the whole semester)
091                    for (BitSet week : weeks) {
092                        boolean isProblem = false;
093                        do {
094                            Set<Placement> adepts = new HashSet<Placement>();
095                            // each blocks contains placements which are BTB
096                            // placements are BTB if there is less time between them than the minimal break length
097                            List<Block> blocks = getBreakBlocks(assignment, dayCode, conflicts, value, null, week);
098                            // determine possible conflicts from blocks' placements
099                            getAdeptsLunchBreak(blocks, adepts);
100                            if (adepts.isEmpty())
101                                isProblem = false;
102                            // currently assigned value shouldn't be added to conflicts if possible 
103                            if (adepts.size() >= 2)
104                                adepts.remove(value);
105                            // pick random placement
106                            Placement conflict = ToolBox.random(adepts);
107                            if (conflict != null) {
108                                conflicts.add(conflict);
109                            }
110                        } while (isProblem);
111                    }   
112                }
113            }            
114        }
115    }  
116    
117    /**
118     * Creates a list of consecutive blocks with back-to-back classes.
119     * @param assignment current assignment
120     * @param dayCode days of week
121     * @param conflicts conflicting assignment
122     * @param value placement in question
123     * @param assignments other considered assignments
124     * @param week selected week
125     * @return classes merged into blocks
126     */
127    public List<Block> getBreakBlocks(Assignment<Lecture, Placement> assignment, int dayCode, Set<Placement> conflicts, Placement value, HashMap<Lecture, Placement> assignments, BitSet week) {     
128        
129        List<Placement> toBeSorted = new ArrayList<Placement>(getRelevantPlacements(assignment, dayCode, conflicts, value, assignments, week));
130        Collections.sort(toBeSorted, new PlacementTimeComparator());           
131             
132        return mergeToBlocks(toBeSorted, iBreakLength);
133    }     
134    
135    
136    
137    /**
138     * Method adds Placements from blocks to adepts if there is a possibility, that the placement caused constraint violation
139     * 
140     * @param blocks placements in 
141     * @param adepts
142     */
143    private void getAdeptsLunchBreak(List<Block> blocks, Set<Placement> adepts) {
144        List<Block> matchingBlocks = new ArrayList<Block>();
145        for(Block block: blocks){
146            // if block intersects with break interval, it will be used in conflict selection
147            if (block.getStartSlotCurrentBlock() <= iBreakEnd && block.getEndSlotCurrentBlock() >= iBreakStart) matchingBlocks.add(block);          
148        }
149        int size = matchingBlocks.size();
150        // if there is none block intersecting with break interval, the constraint is satisfied
151        // if there are at least 2 blocks intersecting with break interval, the constraint is satisfied, 
152        // because there must be a space between them, otherwise they would be in one block
153        // if there is only one block intersecting with break interval, constraint might not be satisfied
154        if (size == 1) {
155            Block block = matchingBlocks.get(0);
156            // check whether the block leaves enough space for break
157            if (block.getStartSlotCurrentBlock() - iBreakStart >= iBreakLength || iBreakEnd - block.getEndSlotCurrentBlock() >= iBreakLength){
158                return;
159            // if it doesn't
160            }else{
161                // every placement intersecting with break interval might be potential conflict
162                for (Placement p: block.getPlacements()){
163                    if ( p.getTimeLocation().getStartSlot() <= iBreakEnd && p.getTimeLocation().getStartSlot()+ p.getTimeLocation().getLength() >= iBreakStart){
164                        adepts.add(p);
165                    }
166                }                
167            }
168        }       
169    }
170    
171    @Override
172    public double getNrViolations(Assignment<Lecture, Placement> assignment, Set<Placement> conflicts, HashMap<Lecture, Placement> assignments){
173        List<BitSet> weeks = getWeeks();
174
175        int violatedDays = 0;
176        for (int dayCode : Constants.DAY_CODES) {
177            weekIteration: for (BitSet week : weeks) {
178                Set<Placement> adepts = new HashSet<Placement>();
179                List<Block> blocks = getBreakBlocks(assignment, dayCode, null, null, assignments, week);
180                getAdeptsLunchBreak(blocks, adepts);
181                if (!adepts.isEmpty())
182                    violatedDays++;
183                break weekIteration;
184            }
185        }
186        return violatedDays;
187    }
188    
189}