/*
 * Copyright (C) 2005-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco 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.
 *
 * Alfresco 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.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */
package org.alfresco.repo.domain.hibernate;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Set;

import org.alfresco.util.GUID;
import org.hibernate.Session;
import org.hibernate.engine.EntityKey;

/**
 * Support to (optionally) listen to hibernate events generated by a hibernate session. The tracking is bound to a
 * transaction resource
 * 
 * @author andyh
 */
public class HibernateSessionHelperResource implements HibernateSessionHelperResourceProvider
{
    LinkedHashMap<String, Set<EntityKey>> marks = new LinkedHashMap<String, Set<EntityKey>>();

    String currentMark = null;

    HibernateSessionHelperResource()
    {

    }

    public String getCurrentMark()
    {
        return currentMark;
    }
    
    public List<String> getMarks(Session session)
    {
        ArrayList<String> answer = new ArrayList<String>(marks.size());
        for (String key : marks.keySet())
        {
            answer.add(key);
        }
        return answer;
    }

    public void mark(Session session)
    {
        String guid = GUID.generate();
        mark(session, guid);
    }

    @SuppressWarnings("unchecked")
    public void mark(Session session, String label)
    {
        if (label == null)
        {
            throw new HibernateSessionHelperResourceException("Null key is not supported");

        }
        if (marks.containsKey(label))
        {
            throw new HibernateSessionHelperResourceException("Key already exists - " + label);
        }

        if (marks.size() == 0)
        {
            SessionSizeResourceManager.setDisableInTransaction();
        }

        HashSet<EntityKey> mark = new HashSet<EntityKey>((Set<EntityKey>) session.getStatistics().getEntityKeys());
        
        // If the mark is too large, then the flush process will be excessive.
        if (mark.size() > 1000)
        {
            // The session is to big.  Use the mark to as a basis for cleaning out the session.
            if (currentMark == null)
            {
                // The session is just too big
                SessionSizeResourceManager.clear(session);
            }
            else
            {
                reset(session);
            }
            // Get the mark list again
            mark = new HashSet<EntityKey>((Set<EntityKey>) session.getStatistics().getEntityKeys());
        }
        
        marks.put(label, mark);
        currentMark = label;
    }

    public void removeMark(Session session)
    {
        if (currentMark != null)
        {
            removeMark(session, currentMark);
        }
        else
        {
            throw new HibernateSessionHelperResourceException("No current mark");
        }
        
    }

    public void removeMark(Session session, String label)
    {
        if (label == null)
        {
            throw new HibernateSessionHelperResourceException("Null key is not supported");

        }
        if (!marks.containsKey(label))
        {
            throw new HibernateSessionHelperResourceException("Key does not exist - " + label);
        }

        if (marks.size() > 0)
        {
            marks.remove(label);

            if (label.equals(currentMark))
            {
                currentMark = getLastMarkOrNull();
            }
        }

        if (marks.size() == 0)
        {
            SessionSizeResourceManager.setEnableInTransaction();
        }
    }

    public void reset(Session session)
    {
        if (currentMark != null)
        {
            doResetAndRemove(session, currentMark, false);
        }
        else
        {
            throw new HibernateSessionHelperResourceException("No current mark");
        }
    }

    public void reset(Session session, String label)
    {
        doResetAndRemove(session, label, false);
    }

    public void resetAndRemoveMark(Session session)
    {
        if (currentMark != null)
        {
            doResetAndRemove(session, currentMark, true);
        }
        else
        {
            throw new HibernateSessionHelperResourceException("No current mark");
        }
    }

    public void resetAndRemoveMark(Session session, String label)
    {
        doResetAndRemove(session, label, true);
    }

    @SuppressWarnings("unchecked")
    private void doResetAndRemove(Session session, String label, boolean remove)
    {
        if (label == null)
        {
            throw new HibernateSessionHelperResourceException("Null key is not supported");

        }
        if (!marks.containsKey(label))
        {
            throw new HibernateSessionHelperResourceException("Key does not exist - " + label);
        }
        if (marks.size() > 0)
        {
            session.flush();

            Set<EntityKey> check = marks.get(label);
            Set<EntityKey> current = new HashSet<EntityKey>((Set<EntityKey>) session.getStatistics().getEntityKeys());

            Set<Object> toEvict = new HashSet<Object>(Math.max((int) (current.size() / .75f) + 1, 16));

            for (EntityKey key : current)
            {
                if (!check.contains(key))
                {
                    Object val = session.get(key.getEntityName(), key.getIdentifier());
                    if (val != null)
                    {
                        toEvict.add(val);
                    }
                }
            }

            for (Object evitee : toEvict)
            {
                session.evict(evitee);
            }

            String last;
            while ((last = getLastMarkOrNull()) != null)
            {
                if (!label.equals(last))
                {
                    marks.remove(last);
                }
                else
                {
                    if (remove)
                    {
                        marks.remove(last);
                    }
                    break;
                }
            }

            currentMark = getLastMarkOrNull();

            if (marks.size() == 0)
            {
                SessionSizeResourceManager.setEnableInTransaction();
            }
            
            //System.out.println("Removed "+marks.size()+" "+label);
        }
    }

    private String getLastMarkOrNull()
    {
        String mark = null;
        for (String key : marks.keySet())
        {
            mark = key;
        }
        return mark;
    }

}