/* Copyright (C) 2004 - 2008  db4objects Inc.  http://www.db4o.com

This file is part of the db4o open source object database.

db4o is free software; you can redistribute it and/or modify it under
the terms of version 2 of the GNU General Public License as published
by the Free Software Foundation and as clarified by db4objects' GPL 
interpretation policy, available at
http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
Suite 350, San Mateo, CA 94403, USA.

db4o 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 General Public License
for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
package com.db4o.typehandlers;

import java.util.*;
import com.db4o.ext.*;
import com.db4o.foundation.*;
import com.db4o.internal.*;
import com.db4o.internal.activation.*;
import com.db4o.internal.delete.*;
import com.db4o.internal.handlers.*;
import com.db4o.internal.marshall.*;
import com.db4o.marshall.*;

/**
 * TypeHandler for classes that implement java.util.List.<br><br>
 * 
 * @decaf.ignore.jdk11
 * 
 */
public class ListTypeHandler implements TypeHandler4, FirstClassHandler,
		CanHoldAnythingHandler, VariableLengthTypeHandler {

	public PreparedComparison prepareComparison(Context context, Object obj) {
		// TODO Auto-generated method stub
		return null;
	}

	public void write(WriteContext context, Object obj) {
		List list = (List) obj;
		writeElementCount(context, list);
		writeElements(context, list);
	}

	public Object read(ReadContext context) {
		List list = (List) ((UnmarshallingContext) context).persistentObject();
		int elementCount = context.readInt();
		TypeHandler4 elementHandler = elementTypeHandler(context, list);
		for (int i = 0; i < elementCount; i++) {
			list.add(context.readObject(elementHandler));
		}
		return list;
	}

	private void writeElementCount(WriteContext context, List list) {
		context.writeInt(list.size());
	}

	private void writeElements(WriteContext context, List list) {
		TypeHandler4 elementHandler = elementTypeHandler(context, list);
		final Iterator elements = list.iterator();
		while (elements.hasNext()) {
			context.writeObject(elementHandler, elements.next());
		}
	}

	private ObjectContainerBase container(Context context) {
		return ((InternalObjectContainer) context.objectContainer())
				.container();
	}

	private TypeHandler4 elementTypeHandler(Context context, List list) {

		// TODO: If all elements in the list are of one type,
		// it is possible to use a more specific handler

		return container(context).handlers().untypedObjectHandler();
	}

	public void delete(final DeleteContext context) throws Db4oIOException {
		if (!context.cascadeDelete()) {
			return;
		}
		TypeHandler4 handler = elementTypeHandler(context, null);
		int elementCount = context.readInt();
		for (int i = elementCount; i > 0; i--) {
			handler.delete(context);
		}
	}

	public void defragment(DefragmentContext context) {
		TypeHandler4 handler = elementTypeHandler(context, null);
		int elementCount = context.readInt();
		for (int i = 0; i < elementCount; i++) {
			handler.defragment(context);
		}
	}

	public final void cascadeActivation(ActivationContext4 context) {
		Iterator all = ((List) context.targetObject()).iterator();
		while (all.hasNext()) {
			context.cascadeActivationToChild(all.next());
		}
	}

	public TypeHandler4 readCandidateHandler(QueryingReadContext context) {
		return this;
	}


	private TypeHandler4 untypedObjectHandlerFrom(Context context) {
	    return context.transaction().container().handlers().untypedObjectHandler();
	}

    public void collectIDs(final QueryingReadContext context) {
        int elementCount = context.readInt();
        TypeHandler4 elementHandler = untypedObjectHandlerFrom(context);
        for (int i = 0; i < elementCount; i++) {
            context.readId(elementHandler);
        }
    }

}
