/*
* Copyright (C) 2004 Awarix, Inc. All rights reserved.
*
* $Id: HibernatePersistenceDelegate.java 1915 2004-11-11 22:50:56Z archie $
*/

package com.awarix.util.hibernate;

import java.beans.DefaultPersistenceDelegate;
import java.beans.Encoder;
import java.beans.Expression;
import java.beans.PersistenceDelegate;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.Transaction;

/**
* An extension of {@link PersistenceDelegate PersistenceDelegate}
* that handles Hibernate collections classes. These classes cannot normally
* be instantiated by the application, so they don't pass successfully through
* an XML encoded stream. On the other hand, Hibernate will let you replace
* them with the usual collections classes from <code>java.util</code>. So
* that's what we do here.
*/
public class HibernatePersistenceDelegate extends DefaultPersistenceDelegate {
                                                                               
    static HibernatePersistenceDelegate INSTANCE
      = new HibernatePersistenceDelegate();

    static final Map CLASS_MAP;
    static {
        HashMap map = new HashMap();
        map.put(net.sf.hibernate.collection.Bag.class, ArrayList.class);
        map.put(net.sf.hibernate.collection.IdentifierBag.class,
          ArrayList.class);
        map.put(net.sf.hibernate.collection.List.class, ArrayList.class);
        map.put(net.sf.hibernate.collection.Map.class, HashMap.class);
        map.put(net.sf.hibernate.collection.Set.class, HashSet.class);
        map.put(net.sf.hibernate.collection.SortedMap.class, TreeMap.class);
        map.put(net.sf.hibernate.collection.SortedSet.class, TreeSet.class);
        CLASS_MAP = Collections.synchronizedMap(map);
    }

    private HibernatePersistenceDelegate() {
    }

    /**
     * Get the set of delegates to install in an
     * {@link java.beans.Encoder Encoder}
     *  to properly handle Hibernate collections types. This method returns
     * the set as a mapping from <code>Class</code> -&gt;
     * <code>PersistenceDelegate</code>.
     */
    public static Map getDelegates() {
        HashMap map = new HashMap();
        for (Iterator i = CLASS_MAP.keySet().iterator(); i.hasNext(); )
            map.put(i.next(), INSTANCE);
        return map;
    }

    /**
     * Overridden to handle conversion of Hibernate collection
     * classes into <code>java.util</code> collection classes.
     */
    protected Expression instantiate(Object oldInstance, Encoder out) {
        Class replaceType = (Class)CLASS_MAP.get(oldInstance.getClass());
        if (replaceType != null) {
            return new Expression(oldInstance,
              replaceType, "new", new Object[0]);
        }
        return super.instantiate(oldInstance, out);
    }

    /**
     * Overridden to handle conversion of Hibernate collection
     * classes into <code>java.util</code> collection classes.
     */
    protected boolean mutatesTo(Object oldInstance, Object newInstance) {
        if (oldInstance != null && newInstance != null
          && CLASS_MAP.get(oldInstance.getClass()) == newInstance.getClass())
            return true;
        return super.mutatesTo(oldInstance, newInstance);
    }

    /**
     * Overridden to handle conversion of Hibernate collection
     * classes into <code>java.util</code> collection classes.
     */
    protected void initialize(Class type, Object oldInstance,
      Object newInstance, Encoder out) {
        Class replaceType = (Class)CLASS_MAP.get(oldInstance.getClass());
        if (replaceType != null) {
            Object replace = replace(oldInstance);
            if (type == oldInstance.getClass())
                type = replace.getClass();
            super.initialize(type, replace, newInstance, out);
        }
        super.initialize(type, oldInstance, newInstance, out);
    }

    Object replace(Object obj) {
        if (obj instanceof net.sf.hibernate.collection.Set)
            return new HashSet((Set)obj);
        else if (obj instanceof net.sf.hibernate.collection.Map)
            return new HashMap((Map)obj);
        else if (obj instanceof net.sf.hibernate.collection.SortedSet)
            return new TreeSet((SortedSet)obj);
        else if (obj instanceof net.sf.hibernate.collection.SortedMap)
            return new TreeMap((SortedMap)obj);
        else if (obj instanceof net.sf.hibernate.collection.List
          || obj instanceof net.sf.hibernate.collection.Bag
          || obj instanceof net.sf.hibernate.collection.IdentifierBag)
            return new ArrayList((Collection)obj);
        throw new RuntimeException("unexpected");
    }
}