/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
/*
 *
 * @author Toni Kalajainen
 */
package org.simantics.g2d.dnd;

import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.simantics.utils.datastructures.context.Context;
import org.simantics.utils.datastructures.hints.HintContext;
import org.simantics.utils.datastructures.hints.IHintContext;

/**
 * Contains an ordered set of context items (see {@link #orderedItems}) which
 * works around the fact that {@link Context} base implementation does not
 * preserve any kind of order information for the added drag items, which is
 * often useful for user experience's sake.
 * 
 * <b>WARNING</b> DnDContext is not as thread-safe as its base implementation
 * {@link Context}.
 * 
 * @author Tuukka Lehtonen
 */
public class DnDContext extends Context<IDragItem> implements IDnDContext {

    IHintContext            hintCtx       = new HintContext();

    List<IDragItem>         orderedItems  = new ArrayList<IDragItem>();

    Map<IDragItem, Point2D> itemPositions = new HashMap<IDragItem, Point2D>();

    public DnDContext() {
        super(IDragItem.class);
    }

    @Override
    public IHintContext getHints() {
        return hintCtx;
    }

    @Override
    public synchronized void setItemPosition(IDragItem item, Point2D pos) {
        if (item == null)
            throw new NullPointerException("trying to set position " + pos + " for null IDragItem");
        if (pos == null)
            throw new NullPointerException("trying to set null position for dragged item " + item);
        itemPositions.put(item, pos);
    }

    @Override
    public synchronized Point2D getItemPosition(IDragItem item) {
        return itemPositions.get(item);
    }

    @Override
    public void add(IDragItem item) {
        assertNotDisposed();
        orderedItems.add(item);
        boolean added = false;
        try {
            super.add(item);
            added = true;
        } finally {
            if (!added)
                orderedItems.remove(item);
        }
    }

    @Override
    public boolean remove(IDragItem item) {
        assertNotDisposed();
        boolean existed = super.remove(item);
        if (existed)
            orderedItems.remove(item);
        return existed;
    }

    @Override
    public void clear() {
        assertNotDisposed();
        orderedItems.clear();
        super.clear();
    }

    @Override
    public IDragItem[] toArray() {
        assertNotDisposed();
        return orderedItems.toArray(new IDragItem[orderedItems.size()]);
    }

}