/*******************************************************************************
 * 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
 *******************************************************************************/
package org.simantics.diagram.synchronization.graph;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.simantics.db.Resource;
import org.simantics.db.WriteGraph;
import org.simantics.db.common.utils.OrderedSetUtils;
import org.simantics.diagram.synchronization.ModificationAdapter;
import org.simantics.diagram.ui.DiagramModelHints;
import org.simantics.g2d.diagram.IDiagram;
import org.simantics.g2d.element.ElementUtils;
import org.simantics.g2d.element.IElement;

/**
 * This modification reorders the specified diagram in the graph backend
 * according to the order of the elements specified argument element list.
 * 
 * <p>
 * The algorithm is linear with respect to the amount of elements on the
 * diagram. It tries to minimize the number of ordered set operations.
 * 
 * @author Tuukka Lehtonen
 */
public class ElementReorder extends ModificationAdapter {

    IDiagram diagram;
    List<IElement> order;

    public ElementReorder(IDiagram diagram, List<IElement> order) {
        super(LOW_PRIORITY);
        this.diagram = diagram;
        this.order = order;
    }

    @Override
    public void perform(WriteGraph g) throws Exception {
        Resource l = diagram.getHint(DiagramModelHints.KEY_DIAGRAM_RESOURCE);

        List<Resource> graphOrder = OrderedSetUtils.toList(g, l);
        Set<Resource> graphContents = new HashSet<Resource>(graphOrder);

        List<Resource> newGraphOrder = new ArrayList<>();
        for (IElement e : order) {
            Object obj = ElementUtils.getObject(e);
            if (obj instanceof Resource) {
                Resource r = (Resource) obj;
                // Only consider resources that still are in the diagram.
                // This prevents errors in situations where #order contains
                // elements that no longer exist in the diagram.
                if (graphContents.contains(r)) {
                	newGraphOrder.add(r);
                }
            }
        }

        // Safety measure for possible missing elements
        if (graphOrder.size() != newGraphOrder.size()) {
            Set<Resource> added = new HashSet<Resource>(newGraphOrder);
            for (Resource r : graphOrder) {
                if (!added.contains(r)) {
                    newGraphOrder.add(r);
                }
            }
        }

        OrderedSetUtils.reorder(g, l, newGraphOrder);
    }

}