/* This file is part of the db4o object database http://www.db4o.com

Copyright (C) 2004 - 2011  Versant Corporation http://www.versant.com

db4o is free software; you can redistribute it and/or modify it under
the terms of version 3 of the GNU General Public License as published
by the Free Software Foundation.

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, see http://www.gnu.org/licenses/. */
package com.db4o.typehandlers;

import java.util.*;

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

/**
 * TypeHandler for Collections.
 * 
 * On the .NET side, usage is restricted to instances of IList.
 * 
 * @sharpen.partial
 */
@decaf.Ignore(decaf.Platform.JDK11)
public class CollectionTypeHandler implements ReferenceTypeHandler, CascadingTypeHandler,
		VariableLengthTypeHandler, QueryableTypeHandler {

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

	public void write(WriteContext context, Object obj) {
		Collection collection = (Collection) obj;
		TypeHandler4 elementHandler = detectElementTypeHandler(container(context), collection);
		writeElementClassMetadataId(context, elementHandler);
		writeElementCount(context, collection);
		writeElements(context, collection, elementHandler);
	}

	public void activate(ReferenceActivationContext context) {
		Collection collection = (Collection) ((UnmarshallingContext) context).persistentObject();
		clearCollection(collection);
		TypeHandler4 elementHandler = readElementTypeHandler(context, context);
		int elementCount = context.readInt();
		for (int i = 0; i < elementCount; i++) {
			Object element = context.readObject(elementHandler);
			addToCollection(collection, element);
		}
	}

	private void writeElementCount(WriteContext context, Collection collection) {
		context.writeInt(collection.size());
	}

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

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

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

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

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

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

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

	private void writeElementClassMetadataId(WriteContext context, TypeHandler4 elementHandler) {
		context.writeInt(0);
	}

	private TypeHandler4 readElementTypeHandler(ReadBuffer buffer, Context context) {
		buffer.readInt();
		return (TypeHandler4) container(context).handlers().openTypeHandler();
	}

	private TypeHandler4 detectElementTypeHandler(InternalObjectContainer container, Collection collection) {
		return (TypeHandler4) container.handlers().openTypeHandler();
	}

	/**
	 * @sharpen.ignore
	 */
	private void addToCollection(Collection collection, Object element) {
		collection.add(element);
	}

	/**
	 * @sharpen.ignore
	 */
	private void clearCollection(Collection collection) {
		collection.clear();
	}

	public boolean descendsIntoMembers() {
		return true;
    }
}