package net.sf.cpsolver.studentsct.model;

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import net.sf.cpsolver.coursett.model.Placement;
import net.sf.cpsolver.coursett.model.RoomLocation;
import net.sf.cpsolver.coursett.model.TimeLocation;
import net.sf.cpsolver.studentsct.reservation.Reservation;

/**
 * Representation of a class. Each section contains id, name, scheduling
 * subpart, time/room placement, and a limit. Optionally, parent-child relation
 * between sections can be defined. <br>
 * <br>
 * Each student requesting a course needs to be enrolled in a class of each
 * subpart of a selected configuration. In the case of parent-child relation
 * between classes, if a student is enrolled in a section that has a parent
 * section defined, he/she has to be enrolled in the parent section as well. If
 * there is a parent-child relation between two sections, the same relation is
 * defined on their subparts as well, i.e., if section A is a parent section B,
 * subpart of section A isa parent of subpart of section B. <br>
 * <br>
 * 
 * @version StudentSct 1.2 (Student Sectioning)<br>
 *          Copyright (C) 2007 - 2010 Tomáš Müller<br>
 *          <a href="mailto:muller@unitime.org">muller@unitime.org</a><br>
 *          <a href="http://muller.unitime.org">http://muller.unitime.org</a><br>
 * <br>
 *          This library is free software; you can redistribute it and/or modify
 *          it under the terms of the GNU Lesser General Public License as
 *          published by the Free Software Foundation; either version 3 of the
 *          License, or (at your option) any later version. <br>
 * <br>
 *          This library is distributed in the hope that it will be useful, but
 *          WITHOUT ANY WARRANTY; without even the implied warranty of
 *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *          Lesser General Public License for more details. <br>
 * <br>
 *          You should have received a copy of the GNU Lesser General Public
 *          License along with this library; if not see
 *          <a href='http://www.gnu.org/licenses/'>http://www.gnu.org/licenses/</a>.
 */
public class Section implements Assignment, Comparable<Section> {
    private static DecimalFormat sDF = new DecimalFormat("0.000");
    private long iId = -1;
    private String iName = null;
    private Map<Long, String> iNameByCourse = null;
    private Subpart iSubpart = null;
    private Section iParent = null;
    private Placement iPlacement = null;
    private int iLimit = 0;
    private Set<Enrollment> iEnrollments = new HashSet<Enrollment>();
    private Choice iChoice = null;
    private double iPenalty = 0.0;
    private double iEnrollmentWeight = 0.0;
    private double iMaxEnrollmentWeight = 0.0;
    private double iMinEnrollmentWeight = 0.0;
    private double iSpaceExpected = 0.0;
    private double iSpaceHeld = 0.0;
    private String iNote = null;
    private Set<Long> iIgnoreConflictsWith = null;

    /**
     * Constructor
     * 
     * @param id
     *            section unique id
     * @param limit
     *            section limit, i.e., the maximal number of students that can
     *            be enrolled in this section at the same time
     * @param name
     *            section name
     * @param subpart
     *            subpart of this section
     * @param placement
     *            time/room placement
     * @param instructorIds
     *            instructor(s) id -- needed for {@link Section#getChoice()}
     * @param instructorNames
     *            instructor(s) name -- needed for {@link Section#getChoice()}
     * @param parent
     *            parent section -- if there is a parent section defined, a
     *            student that is enrolled in this section has to be enrolled in
     *            the parent section as well. Also, the same relation needs to
     *            be defined between subpart of this section and the subpart of
     *            the parent section
     */
    public Section(long id, int limit, String name, Subpart subpart, Placement placement, String instructorIds,
            String instructorNames, Section parent) {
        iId = id;
        iLimit = limit;
        iName = name;
        iSubpart = subpart;
        iSubpart.getSections().add(this);
        iPlacement = placement;
        iParent = parent;
        iChoice = new Choice(getSubpart().getConfig().getOffering(), getSubpart().getInstructionalType(), getTime(),
                instructorIds, instructorNames);
    }

    /** Section id */
    @Override
    public long getId() {
        return iId;
    }

    /**
     * Section limit. This is defines the maximal number of students that can be
     * enrolled into this section at the same time. It is -1 in the case of an
     * unlimited section
     */
    public int getLimit() {
        return iLimit;
    }

    /** Set section limit */
    public void setLimit(int limit) {
        iLimit = limit;
    }

    /** Section name */
    public String getName() {
        return iName;
    }
    
    /** Set section name */
    public void setName(String name) {
        iName = name;
    }

    /** Scheduling subpart to which this section belongs */
    public Subpart getSubpart() {
        return iSubpart;
    }

    /**
     * Parent section of this section (can be null). If there is a parent
     * section defined, a student that is enrolled in this section has to be
     * enrolled in the parent section as well. Also, the same relation needs to
     * be defined between subpart of this section and the subpart of the parent
     * section.
     */
    public Section getParent() {
        return iParent;
    }

    /**
     * Time/room placement of the section. This can be null, for arranged
     * sections.
     */
    public Placement getPlacement() {
        return iPlacement;
    }
    
    /**
     * Set time/room placement of the section. This can be null, for arranged
     * sections.
     */
    public void setPlacement(Placement placement) {
        iPlacement = placement;
    }

    /** Time placement of the section. */
    @Override
    public TimeLocation getTime() {
        return (iPlacement == null ? null : iPlacement.getTimeLocation());
    }

    /** Number of rooms in which the section meet. */
    @Override
    public int getNrRooms() {
        return (iPlacement == null ? 0 : iPlacement.getNrRooms());
    }

    /**
     * Room placement -- list of
     * {@link net.sf.cpsolver.coursett.model.RoomLocation}
     */
    @Override
    public List<RoomLocation> getRooms() {
        if (iPlacement == null)
            return null;
        if (iPlacement.getRoomLocations() == null && iPlacement.getRoomLocation() != null) {
            List<RoomLocation> ret = new ArrayList<RoomLocation>(1);
            ret.add(iPlacement.getRoomLocation());
            return ret;
        }
        return iPlacement.getRoomLocations();
    }

    /**
     * True, if this section overlaps with the given assignment in time and
     * space
     */
    @Override
    public boolean isOverlapping(Assignment assignment) {
        if (isAllowOverlap() || assignment.isAllowOverlap()) return false;
        if (getTime() == null || assignment.getTime() == null) return false;
        if (assignment instanceof Section && isToIgnoreStudentConflictsWith(assignment.getId())) return false;
        return getTime().hasIntersection(assignment.getTime());
    }

    /**
     * True, if this section overlaps with one of the given set of assignments
     * in time and space
     */
    @Override
    public boolean isOverlapping(Set<? extends Assignment> assignments) {
        if (isAllowOverlap()) return false;
        if (getTime() == null || assignments == null)
            return false;
        for (Assignment assignment : assignments) {
            if (assignment.isAllowOverlap())
                continue;
            if (assignment.getTime() == null)
                continue;
            if (assignment instanceof Section && isToIgnoreStudentConflictsWith(assignment.getId()))
                continue;
            if (getTime().hasIntersection(assignment.getTime()))
                return true;
        }
        return false;
    }

    /** Called when an enrollment with this section is assigned to a request */
    @Override
    public void assigned(Enrollment enrollment) {
        if (iEnrollments.isEmpty()) {
            iMinEnrollmentWeight = iMaxEnrollmentWeight = enrollment.getRequest().getWeight();
        } else {
            iMaxEnrollmentWeight = Math.max(iMaxEnrollmentWeight, enrollment.getRequest().getWeight());
            iMinEnrollmentWeight = Math.min(iMinEnrollmentWeight, enrollment.getRequest().getWeight());
        }
        iEnrollments.add(enrollment);
        iEnrollmentWeight += enrollment.getRequest().getWeight();
    }

    /** Called when an enrollment with this section is unassigned from a request */
    @Override
    public void unassigned(Enrollment enrollment) {
        iEnrollments.remove(enrollment);
        iEnrollmentWeight -= enrollment.getRequest().getWeight();
        if (iEnrollments.isEmpty()) {
            iMinEnrollmentWeight = iMaxEnrollmentWeight = 0;
        } else if (iMinEnrollmentWeight != iMaxEnrollmentWeight) {
            if (iMinEnrollmentWeight == enrollment.getRequest().getWeight()) {
                double newMinEnrollmentWeight = Double.MAX_VALUE;
                for (Enrollment e : iEnrollments) {
                    if (e.getRequest().getWeight() == iMinEnrollmentWeight) {
                        newMinEnrollmentWeight = iMinEnrollmentWeight;
                        break;
                    } else {
                        newMinEnrollmentWeight = Math.min(newMinEnrollmentWeight, e.getRequest().getWeight());
                    }
                }
                iMinEnrollmentWeight = newMinEnrollmentWeight;
            }
            if (iMaxEnrollmentWeight == enrollment.getRequest().getWeight()) {
                double newMaxEnrollmentWeight = Double.MIN_VALUE;
                for (Enrollment e : iEnrollments) {
                    if (e.getRequest().getWeight() == iMaxEnrollmentWeight) {
                        newMaxEnrollmentWeight = iMaxEnrollmentWeight;
                        break;
                    } else {
                        newMaxEnrollmentWeight = Math.max(newMaxEnrollmentWeight, e.getRequest().getWeight());
                    }
                }
                iMaxEnrollmentWeight = newMaxEnrollmentWeight;
            }
        }
    }

    /** Set of assigned enrollments */
    @Override
    public Set<Enrollment> getEnrollments() {
        return iEnrollments;
    }

    /**
     * Enrollment weight -- weight of all requests which have an enrollment that
     * contains this section, excluding the given one. See
     * {@link Request#getWeight()}.
     */
    public double getEnrollmentWeight(Request excludeRequest) {
        double weight = iEnrollmentWeight;
        if (excludeRequest != null && excludeRequest.getAssignment() != null
                && iEnrollments.contains(excludeRequest.getAssignment()))
            weight -= excludeRequest.getWeight();
        return weight;
    }

    /**
     * Maximal weight of a single enrollment in the section
     */
    public double getMaxEnrollmentWeight() {
        return iMaxEnrollmentWeight;
    }

    /**
     * Minimal weight of a single enrollment in the section
     */
    public double getMinEnrollmentWeight() {
        return iMinEnrollmentWeight;
    }

    /** Long name: subpart name + time long name + room names + instructor names */
    public String getLongName() {
        return getSubpart().getName() + " " + getName() + " " + (getTime() == null ? "" : " " + getTime().getLongName())
                + (getNrRooms() == 0 ? "" : " " + getPlacement().getRoomName(","))
                + (getChoice().getInstructorNames() == null ? "" : " " + getChoice().getInstructorNames());
    }

    @Override
    public String toString() {
        return getSubpart().getConfig().getOffering().getName() + " " + getSubpart().getName() + " " + getName()
                + (getTime() == null ? "" : " " + getTime().getLongName())
                + (getNrRooms() == 0 ? "" : " " + getPlacement().getRoomName(","))
                + (getChoice().getInstructorNames() == null ? "" : " " + getChoice().getInstructorNames()) + " (L:"
                + (getLimit() < 0 ? "unlimited" : "" + getLimit())
                + (getPenalty() == 0.0 ? "" : ",P:" + sDF.format(getPenalty())) + ")";
    }

    /** A (student) choice representing this section. */
    public Choice getChoice() {
        return iChoice;
    }

    /**
     * Return penalty which is added to an enrollment that contains this
     * section.
     */
    public double getPenalty() {
        return iPenalty;
    }

    /** Set penalty which is added to an enrollment that contains this section. */
    public void setPenalty(double penalty) {
        iPenalty = penalty;
    }

    /**
     * Compare two sections, prefer sections with lower penalty and more open
     * space
     */
    @Override
    public int compareTo(Section s) {
        int cmp = Double.compare(getPenalty(), s.getPenalty());
        if (cmp != 0)
            return cmp;
        cmp = Double.compare(getLimit() - getEnrollmentWeight(null), s.getLimit() - s.getEnrollmentWeight(null));
        if (cmp != 0)
            return cmp;
        return Double.compare(getId(), s.getId());
    }

    /**
     * Return the amount of space of this section that is held for incoming
     * students. This attribute is computed during the batch sectioning (it is
     * the overall weight of dummy students enrolled in this section) and it is
     * being updated with each incomming student during the online sectioning.
     */
    public double getSpaceHeld() {
        return iSpaceHeld;
    }

    /**
     * Set the amount of space of this section that is held for incoming
     * students. See {@link Section#getSpaceHeld()} for more info.
     */
    public void setSpaceHeld(double spaceHeld) {
        iSpaceHeld = spaceHeld;
    }

    /**
     * Return the amount of space of this section that is expected to be taken
     * by incoming students. This attribute is computed during the batch
     * sectioning (for each dummy student that can attend this section (without
     * any conflict with other enrollments of that student), 1 / x where x is
     * the number of such sections of this subpart is added to this value).
     * Also, this value is being updated with each incomming student during the
     * online sectioning.
     */
    public double getSpaceExpected() {
        return iSpaceExpected;
    }

    /**
     * Set the amount of space of this section that is expected to be taken by
     * incoming students. See {@link Section#getSpaceExpected()} for more info.
     */
    public void setSpaceExpected(double spaceExpected) {
        iSpaceExpected = spaceExpected;
    }

    /**
     * Online sectioning penalty.
     */
    public double getOnlineSectioningPenalty() {
        if (getLimit() <= 0)
            return 0.0;

        double available = getLimit() - getEnrollmentWeight(null);

        double penalty = (getSpaceExpected() - available) / getLimit();

        return Math.max(-1.0, Math.min(1.0, penalty));
    }

    /**
     * Return true if overlaps are allowed, but the number of overlapping slots should be minimized.
     * This can be changed on the subpart, using {@link Subpart#setAllowOverlap(boolean)}.
     **/
    @Override
    public boolean isAllowOverlap() {
        return iSubpart.isAllowOverlap();
    }
    
    /** Sections first, then by {@link FreeTimeRequest#getId()} */
    @Override
    public int compareById(Assignment a) {
        if (a instanceof Section) {
            return new Long(getId()).compareTo(((Section)a).getId());
        } else {
            return -1;
        }
    }

    /**
     * Available space in the section that is not reserved by any section reservation
     * @param excludeRequest excluding given request (if not null)
     **/
    public double getUnreservedSpace(Request excludeRequest) {
        // section is unlimited -> there is unreserved space unless there is an unlimited reservation too 
        // (in which case there is no unreserved space)
        if (getLimit() < 0) {
            // exclude reservations that are not directly set on this section
            for (Reservation r: getSectionReservations()) {
                // ignore expired reservations
                if (r.isExpired()) continue;
                // there is an unlimited reservation -> no unreserved space
                if (r.getLimit() < 0) return 0.0;
            }
            return Double.MAX_VALUE;
        }
        
        double available = getLimit() - getEnrollmentWeight(excludeRequest);
        // exclude reservations that are not directly set on this section
        for (Reservation r: getSectionReservations()) {
            // ignore expired reservations
            if (r.isExpired()) continue;
            // unlimited reservation -> all the space is reserved
            if (r.getLimit() < 0.0) return 0.0;
            // compute space that can be potentially taken by this reservation
            double reserved = r.getReservedAvailableSpace(excludeRequest);
            // deduct the space from available space
            available -= Math.max(0.0, reserved);
        }
        
        return available;
    }
    
    /**
     * Total space in the section that cannot be used by any section reservation
     **/
    public double getTotalUnreservedSpace() {
        if (iTotalUnreservedSpace == null)
            iTotalUnreservedSpace = getTotalUnreservedSpaceNoCache();
        return iTotalUnreservedSpace;
    }
    private Double iTotalUnreservedSpace = null;
    private double getTotalUnreservedSpaceNoCache() {
        // section is unlimited -> there is unreserved space unless there is an unlimited reservation too 
        // (in which case there is no unreserved space)
        if (getLimit() < 0) {
            // exclude reservations that are not directly set on this section
            for (Reservation r: getSectionReservations()) {
                // ignore expired reservations
                if (r.isExpired()) continue;
                // there is an unlimited reservation -> no unreserved space
                if (r.getLimit() < 0) return 0.0;
            }
            return Double.MAX_VALUE;
        }
        
        // we need to check all reservations linked with this section
        double available = getLimit(), reserved = 0, exclusive = 0;
        Set<Section> sections = new HashSet<Section>();
        reservations: for (Reservation r: getSectionReservations()) {
            // ignore expired reservations
            if (r.isExpired()) continue;
            // unlimited reservation -> no unreserved space
            if (r.getLimit() < 0) return 0.0;
            for (Section s: r.getSections(getSubpart())) {
                if (s.equals(this)) continue;
                if (s.getLimit() < 0) continue reservations;
                if (sections.add(s))
                    available += s.getLimit();
            }
            reserved += r.getLimit();
            if (r.getSections(getSubpart()).size() == 1)
                exclusive += r.getLimit();
        }
        
        return Math.min(available - reserved, getLimit() - exclusive);
    }
    
    
    /**
     * Get reservations for this section
     */
    public List<Reservation> getReservations() {
        if (iReservations == null) {
            iReservations = new ArrayList<Reservation>();
            for (Reservation r: getSubpart().getConfig().getOffering().getReservations()) {
                if (r.getSections(getSubpart()) == null || r.getSections(getSubpart()).contains(this))
                    iReservations.add(r);
            }
        }
        return iReservations;
    }
    private List<Reservation> iReservations = null;
    
    /**
     * Get reservations that require this section
     */
    public List<Reservation> getSectionReservations() {
        if (iSectionReservations == null) {
            iSectionReservations = new ArrayList<Reservation>();
            for (Reservation r: getSubpart().getSectionReservations()) {
                if (r.getSections(getSubpart()).contains(this))
                    iSectionReservations.add(r);
            }
        }
        return iSectionReservations;
    }
    private List<Reservation> iSectionReservations = null;

    /**
     * Clear reservation information that was cached on this section
     */
    public void clearReservationCache() {
        iReservations = null;
        iSectionReservations = null;
        iTotalUnreservedSpace = null;
    }
    
    /**
     * Return course-dependent section name
     */
    public String getName(long courseId) {
        if (iNameByCourse == null) return getName();
        String name = iNameByCourse.get(courseId);
        return (name == null ? getName() : name);
    }
    
    /**
     * Set course-dependent section name
     */
    public void setName(long courseId, String name) {
        if (iNameByCourse == null) iNameByCourse = new HashMap<Long, String>();
        iNameByCourse.put(courseId, name);
    }

    /**
     * Return course-dependent section names
     */
    public Map<Long, String> getNameByCourse() { return iNameByCourse; }
    
    @Override
    public boolean equals(Object o) {
        if (o == null || !(o instanceof Section)) return false;
        return getId() == ((Section)o).getId();
    }
    
    @Override
    public int hashCode() {
        return (int) (iId ^ (iId >>> 32));
    }
    
    /**
     * Section note
     */
    public String getNote() { return iNote; }
    
    /**
     * Section note
     */
    public void setNote(String note) { iNote = note; }
    
    /**
     * Add section id of a section that student conflicts are to be ignored with
     */
    public void addIgnoreConflictWith(long sectionId) {
        if (iIgnoreConflictsWith == null) iIgnoreConflictsWith = new HashSet<Long>();
        iIgnoreConflictsWith.add(sectionId);
    }
    
    /**
     * Returns true if student conflicts between this section and the given one are to be ignored
     */
    public boolean isToIgnoreStudentConflictsWith(long sectionId) {
        return iIgnoreConflictsWith != null && iIgnoreConflictsWith.contains(sectionId);
    }
    
    /**
     * Returns a set of ids of sections that student conflicts are to be ignored with (between this section and the others)
     */
    public Set<Long> getIgnoreConflictWithSectionIds() {
        return iIgnoreConflictsWith;
    }
}