public class StudentAssignmentRemover {
   
   
    //GLOBALS
    private static Logger logger = Logger.getLogger(StudentAssignmentRemover.class);
    protected Session session;
    protected Transaction tx;
    protected User user;
    protected Relation relation;
    protected ContentRecord contRec;
    protected AssignmentRecord assignRec;
    protected Group group;
    protected Assignment assignment;
    protected Location location;
    protected Permission permission;
   
    /** Creates a new instance of StudentAssignmentRemover */
    public StudentAssignmentRemover() {
    }
   
    /** Deletes assignment history records from LMS_CONTENT_RECORD. This method calls
     * removeRelations(Set "User Object".getRelations()) and deleteContentRecords(Set "User Object".getAssignmentsAssignedTo()) */
    public void deleteAssignments()   {
        session = HibernateUtil.getSessionFactory().getCurrentSession();
        tx = session.beginTransaction();
        Query query;
        List users;
       
        query = session.getNamedQuery("findAllNonSystemGroups");        // get all non-system groups
        Object[] groups = query.list().toArray();                       //throw them into an array of Object[]
        int numGroupsFound = groups.length;                             //num of groups found
       
       for(int g = 0; g < numGroupsFound;g++)   {                       //loop through each group
            group = (Group) groups[g];                                  //cast to a Group obj from the group array
            logger.debug("Getting users of group: " + group.getName());
            //If the session was closed by a commit(), reopen it
            if(! session.isOpen())
            {
                logger.warn("SessionFactory was closed, no worries, Re-opening sessionFactory for StudentAssignmentRemover");
                session = HibernateUtil.getSessionFactory().getCurrentSession();
                tx = session.beginTransaction();
            }
// bypassing UserDAO and calling the query directly. Doing this because Group.getUsers() returned DAOFactory exception (null)
            query = session.getNamedQuery("findUsersInGroup");         
            query.setParameter(0,group);
            users = query.list();                                       //query for the users of this group
            logger.debug("Working on group: " + group.getName());
           
            if(! users.isEmpty())   {                        //if no users in group do nothing.
                int index = 0;
                Object[] relObj;
                logger.info("Query Returned Results.. ");
                int resultSize = users.size();
                int userCounter = 0;
                logger.debug("There is/are " + resultSize + " users for the above listed class");

                while(userCounter < resultSize)   {                //for each user, remove each content_record for each assignment
                    user = (User) users.get(userCounter);
                    logger.info("Deleting LMS assignment data of user: " + user.getUsername() + " for the current group");
                    //Delete relations
                    logger.debug("Removing any entries for user in LMS_RELATION");
                    deleteRelations(user.getRelations());
                    //delete content_records
                    logger.debug("Removing assignment history for the user in the current group...");
                    deleteContentRecords(user.getAssignmentsAssignedTo());
                    userCounter++;               
                }

            tx.commit();
            }

            else    {
            logger.info("No records that match query");     
            } 
           
       }
       
        if(session.isOpen())    {
            session.close();
        }
   }    // end
   
   
   protected void deleteRelations(Set relationSet)    {
       Set relations = relationSet;
       Object[] relObj;
       
       for(int i = 0; i < relations.size(); i++)   {
            relObj = relations.toArray();
            relation = (Relation) relObj[i];
            logger.info("Deleting the relation: " + relation.getRelationshipType().toString());
            session.delete(relObj[i]);
            tx.commit();
        }
   }    // end listRelations(Set relationSet)
   
   
   protected void deleteContentRecords(Set assignedTo)  {

        Object[] assgnToArr = assignedTo.toArray();
        Set contRecs;
       
        for(int i = 0; i < assignedTo.size(); i++)   {
            if(! session.isOpen())
            {
                logger.warn("SessionFactory was closed, no worries, Re-opening sessionFactory for StudentAssignmentRemover");
                session = HibernateUtil.getSessionFactory().getCurrentSession();
                tx = session.beginTransaction();
            }
            assignment = (Assignment) assgnToArr[i];
            logger.info("Deleting assignment history for: " + assignment.getName() + ", PK_ASSIGNMENT_ID: " + assignment.getId());
            assignRec = assignment.getAssignmentRecord();   //LMS_CONTENT_RECORD
           
            contRecs = assignRec.getContentRecords();       //LMS_CONTENT_RECORD
            Object[] contRecArr = contRecs.toArray();
            int arrSize = contRecs.size();
            logger.debug("For the current user there is/are " + contRecs.size() + " content record(s) for the assignment: " + assignRec.getAssignment().getName());
           
                for(int r = 0; r < arrSize; r++)    {
                    contRec = (ContentRecord) contRecArr[r];
                    logger.info("Deleting content Record " + contRec.getId());
                    assignRec.removeActivityRecord(contRec);
                    tx.commit();
                        if(! session.isOpen())
                        {
                            logger.warn("Re-opening sessionFactory for StudentAssignmentRemover");
                            session = HibernateUtil.getSessionFactory().getCurrentSession();
                            tx = session.beginTransaction();
                        }
                }
        }
   }        // end deleteContentRecords()
   
   
}       // End Class