package org.simantics.diagram.elements;

import java.awt.geom.AffineTransform;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import org.simantics.db.ReadGraph;
import org.simantics.db.Resource;
import org.simantics.db.UndoContext;
import org.simantics.db.WriteGraph;
import org.simantics.db.common.CommentMetadata;
import org.simantics.db.common.request.IndexRoot;
import org.simantics.db.common.request.WriteRequest;
import org.simantics.db.exception.DatabaseException;
import org.simantics.db.exception.ManyObjectsForFunctionalRelationException;
import org.simantics.db.exception.NoSingleResultException;
import org.simantics.db.exception.ServiceException;
import org.simantics.db.request.Write;
import org.simantics.diagram.query.DiagramRequests;
import org.simantics.diagram.stubs.DiagramResource;
import org.simantics.diagram.synchronization.graph.DiagramGraphUtil;
import org.simantics.g2d.diagram.DiagramClass;
import org.simantics.g2d.diagram.IDiagram;
import org.simantics.g2d.diagram.impl.Diagram;
import org.simantics.g2d.element.ElementClass;
import org.simantics.g2d.element.ElementUtils;
import org.simantics.g2d.element.IElement;
import org.simantics.g2d.element.impl.Element;
import org.simantics.g2d.utils.GeometryUtils;
import org.simantics.scl.commands.Command;
import org.simantics.scl.commands.Commands;
import org.simantics.ui.SimanticsUI;

/**
 * Tools to align, rotate, and flip diagram elements.
 * 
 * TODO : We need to add capability hints to elements to prevent rotating and mirroring elements that do not support that.
 *        Example: mirrored text does not make any sense.
 * 
 * 
 * @author Marko Luukkainen <marko.luukkainen@vtt.fi> (implementation)
 * @author Tuukka Lehtonen (documentation)
 */
public final class ElementTransforms {

    public static enum SIDE { LEFT, RIGHT, TOP, BOTTOM, VERT, HORIZ, VERT_BTW, HORIZ_BTW };

    /**
     * Align the specified set of diagram element resources in line with each
     * other calculated by the specified side.
     * 
     * <p>
     * Alignment requires at least two elements to do anything.
     * 
     * @param resources diagram element resources to rotate
     * @param side the side of each element to use for distancing. Does not support between aligments.
     */
    public static void align(final Resource resources[], final SIDE side) {
        if (resources.length < 2)
            return;
        if (side == SIDE.HORIZ_BTW || side == SIDE.VERT_BTW )
            return;

        SimanticsUI.getSession().asyncRequest(new WriteRequest() {

            @Override
            public void perform(WriteGraph graph) throws DatabaseException {
                graph.markUndoPoint();
                IDiagram hints = Diagram.spawnNew(DiagramClass.DEFAULT);

                List<AlignElement> elements = new ArrayList<AlignElement>();
                for (Resource r : resources) {
                    AlignElement e = create(graph, hints, r);
                    if (e != null)
                        elements.add(e);
                }
                if (elements.size() < 2)
                    return;
                double mx = 0;
                double my = 0;
                for (AlignElement e : elements) {
                    mx += e.transform[4];
                    my += e.transform[5];
                }
                mx /= elements.size();
                my /= elements.size();

                // prevent moving symbols into the same position
                int count = 0;
                for (AlignElement e : elements) {
                    if (side == SIDE.VERT || side == SIDE.LEFT || side == SIDE.RIGHT) {
                        if (Math.abs(e.transform[5] - my) < 0.1) {
                            count++;
                        }
                    } else {
                        if (Math.abs(e.transform[4] - mx) < 0.1) {
                            count++;
                        }
                    }
                }
                if (count > 1)
                    return;

                if (side == SIDE.HORIZ || side == SIDE.VERT) {


                    for (AlignElement e : elements) {

                        if (side == SIDE.VERT)
                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],mx,e.transform[5]});
                        else if (side == SIDE.HORIZ) {
                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],e.transform[4],my});
                        }
                    }
                } else {
                    double lx, rx;
                    double ty, by;
                    lx = elements.get(0).transform[4] + elements.get(0).rotatedBounds.getMinX();
                    rx = elements.get(0).transform[4] + elements.get(0).rotatedBounds.getMaxX();

                    ty = elements.get(0).transform[5] + elements.get(0).rotatedBounds.getMinY();
                    by = elements.get(0).transform[5] + elements.get(0).rotatedBounds.getMaxY();

                    for (int i = 1; i < elements.size(); i++) {
                        double tlx, trx;
                        double tty, tby;
                        tlx = elements.get(i).transform[4] + elements.get(i).rotatedBounds.getMinX();
                        trx = elements.get(i).transform[4] + elements.get(i).rotatedBounds.getMaxX();

                        tty = elements.get(i).transform[5] + elements.get(i).rotatedBounds.getMinY();
                        tby = elements.get(i).transform[5] + elements.get(i).rotatedBounds.getMaxY();
                        if (tlx < lx)
                            lx = tlx;
                        if (trx > rx)
                            rx = trx;
                        if (tty < ty)
                            ty = tty;
                        if (tby > by)
                            by = tby;

                    }

                    for (AlignElement e : elements) {
                        mx = e.transform[4];
                        my = e.transform[5];
                        if (side == SIDE.LEFT) {
                            mx = lx - e.rotatedBounds.getMinX() ;
                        } else if (side == SIDE.RIGHT) {
                            mx = rx - e.rotatedBounds.getMaxX();
                        } else if (side == SIDE.TOP) {
                            my = ty - e.rotatedBounds.getMinY();
                        } else {
                            my = by - e.rotatedBounds.getMaxY();
                        }
                        DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],mx,my});

                    }

                }

            }
        });
    }

    /**
     * Distance specified set of diagram element resources equally. Distancing
     * is performed on the specified side of the each element.
     * 
     * <p>
     * Distancing requires at least three elements to work.
     * 
     * @param resources diagram element resources to rotate
     * @param side the side of each element to use for distancing
     */
    public static void dist(final Resource resources[], final SIDE side) {

        if (resources.length < 3)
            return;

        SimanticsUI.getSession().asyncRequest(new WriteRequest() {

            @Override
            public void perform(WriteGraph graph) throws DatabaseException {
                graph.markUndoPoint();
                IDiagram hints = Diagram.spawnNew(DiagramClass.DEFAULT);

                List<AlignElement> elements = new ArrayList<AlignElement>();
                for (Resource r : resources) {
                    //System.out.println(r + " " + GraphUtils.getReadableName(graph, r));
                    AlignElement e = create(graph, hints, r);
                    if (e != null)
                        elements.add(e);
                }
                if (elements.size() < 3)
                    return;
                switch (side) {
                    case LEFT: {
                        Collections.sort(elements, new XComparator());
                        AlignElement left = elements.get(0);
                        AlignElement right = elements.get(elements.size() - 1);

                        double leftEdge = left.transform[4] + left.rotatedBounds.getMinX();
                        double rightEdge = right.transform[4] + right.rotatedBounds.getMinX();

                        double totalDist = rightEdge - leftEdge;
                        double dist = totalDist / (elements.size() - 1);
                        double d = leftEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double mx = d - e.rotatedBounds.getMinX();

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],mx,e.transform[5]});
                        }

                        break;
                    }
                    case VERT: {
                        Collections.sort(elements, new XComparator());
                        AlignElement left = elements.get(0);
                        AlignElement right = elements.get(elements.size() - 1);

                        double leftEdge = left.transform[4];
                        double rightEdge = right.transform[4];

                        double totalDist = rightEdge - leftEdge;
                        double dist = totalDist / (elements.size() - 1);
                        double d = leftEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double mx = d;

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],mx,e.transform[5]});
                        }

                        break;
                    }
                    case RIGHT:{
                        Collections.sort(elements, new XComparator());
                        AlignElement left = elements.get(0);
                        AlignElement right = elements.get(elements.size() - 1);

                        double leftEdge = left.transform[4] + left.rotatedBounds.getMaxX();
                        double rightEdge = right.transform[4] + right.rotatedBounds.getMaxX();

                        double totalDist = rightEdge - leftEdge;
                        double dist = totalDist / (elements.size() - 1);
                        double d = leftEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double mx = d - e.rotatedBounds.getMaxX();

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],mx,e.transform[5]});
                        }
                        break;
                    }
                    case VERT_BTW:{
                        Collections.sort(elements, new XComparator());
                        AlignElement left = elements.get(0);
                        AlignElement right = elements.get(elements.size() - 1);

                        double leftEdge = left.transform[4] + left.rotatedBounds.getMaxX();
                        double rightEdge = right.transform[4] + right.rotatedBounds.getMinX();

                        double totalDist = rightEdge - leftEdge;
                        double totalElementSize = 0;
                        for (int i = 1; i < elements.size() -1; i++) {
                            totalElementSize += elements.get(i).rotatedBounds.getWidth();
                        }
                        double totalAvail = totalDist - totalElementSize;
                        double dist = totalAvail / (elements.size() - 1);
                        double d = leftEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double mx = d - e.rotatedBounds.getMinX();
                            d += e.bounds.getWidth();

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],mx,e.transform[5]});
                        }

                        break;
                    }
                    case BOTTOM: {
                        Collections.sort(elements, new YComparator());
                        AlignElement top = elements.get(0);
                        AlignElement bottom = elements.get(elements.size() - 1);

                        double topEdge = top.transform[5] + top.rotatedBounds.getMaxY();
                        double bottomEdge = bottom.transform[5] + bottom.rotatedBounds.getMaxY();

                        double totalDist = bottomEdge - topEdge;
                        double dist = totalDist / (elements.size() - 1);
                        double d = topEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double my = d - e.rotatedBounds.getMaxY();

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],e.transform[4],my});
                        }

                        break;
                    }
                    case TOP: {
                        Collections.sort(elements, new YComparator());
                        AlignElement top = elements.get(0);
                        AlignElement bottom = elements.get(elements.size() - 1);

                        double topEdge = top.transform[5] + top.rotatedBounds.getMinY();
                        double bottomEdge = bottom.transform[5] + bottom.rotatedBounds.getMinY();

                        double totalDist = bottomEdge - topEdge;
                        double dist = totalDist / (elements.size() - 1);
                        double d = topEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double my = d - e.rotatedBounds.getMinY();

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],e.transform[4],my});
                        }

                        break;
                    }
                    case HORIZ: {
                        Collections.sort(elements, new YComparator());
                        AlignElement top = elements.get(0);
                        AlignElement bottom = elements.get(elements.size() - 1);

                        double topEdge = top.transform[5];
                        double bottomEdge = bottom.transform[5];

                        double totalDist = bottomEdge - topEdge;
                        double dist = totalDist / (elements.size() - 1);
                        double d = topEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double my = d;

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],e.transform[4],my});
                        }

                        break;
                    }
                    case HORIZ_BTW: {
                        Collections.sort(elements, new YComparator());
                        AlignElement top = elements.get(0);
                        AlignElement bottom = elements.get(elements.size() - 1);

                        double topEdge = top.transform[5] + top.rotatedBounds.getMaxY();
                        double bottomEdge = bottom.transform[5] + bottom.rotatedBounds.getMinY();

                        double totalDist = bottomEdge - topEdge;
                        double totalElementSize = 0;
                        for (int i = 1; i < elements.size() -1; i++) {
                            totalElementSize += elements.get(i).rotatedBounds.getHeight();
                        }
                        double totalAvail = totalDist - totalElementSize;
                        double dist = totalAvail / (elements.size() - 1);
                        double d = topEdge;

                        for (int i = 1; i < elements.size() -1; i++) {
                            d += dist;
                            AlignElement e = elements.get(i);

                            double my = d - e.rotatedBounds.getMinY();
                            d += e.rotatedBounds.getHeight();

                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{e.transform[0],e.transform[1],e.transform[2],e.transform[3],e.transform[4],my});
                        }

                        break;
                    }

                }


            }
        });

    }

    /**
     * Rotate specified set of diagram element resources around the center of
     * mass of the specified element selection.
     * 
     * @param resources diagram element resources to rotate
     * @param clockwise <code>true</code> to rotate 90 degrees clockwise,
     *        <code>false</code> to rotate 90 degrees counter-clockwise
     */
    public static void rotate(final Resource resources[], final boolean clockwise) {
        SimanticsUI.getSession().asyncRequest(new WriteRequest() {
            @Override
            public void perform(WriteGraph graph) throws DatabaseException {
                graph.markUndoPoint();
                IDiagram hints = Diagram.spawnNew(DiagramClass.DEFAULT);

                DiagramResource DIA = DiagramResource.getInstance(graph);
                
                List<AlignElement> elements = new ArrayList<AlignElement>();
                List<Resource> connections = new ArrayList<Resource>();
                for (Resource r : resources) {
                    AlignElement e = create(graph, hints, r);
                    if (e != null)
                        elements.add(e);
                    else if(graph.isInstanceOf(r, DIA.RouteGraphConnection))
                        connections.add(r);
                }
                if (elements.size() < 1)
                    return;

                // Add comment to change set.
                CommentMetadata cm = graph.getMetadata(CommentMetadata.class);
                graph.addMetadata( cm.add("Rotate " + elements.size() + " elements " + (clockwise ? "clockwise" : "counter-clockwise")) );

                AffineTransform at = clockwise ? AffineTransform.getQuadrantRotateInstance(1)
                        : AffineTransform.getQuadrantRotateInstance(3);

                if (elements.size() == 1 && connections.isEmpty()) {
                    for (AlignElement e : elements) {
                        AffineTransform eat = new AffineTransform(e.transform[0], e.transform[1], e.transform[2], e.transform[3], 0, 0);
                        eat.preConcatenate(at);
                        
                        DiagramGraphUtil.changeTransform(graph, e.element, 
                                new double[]{eat.getScaleX(),eat.getShearY(),eat.getShearX(),eat.getScaleY(),e.transform[4],e.transform[5]});
                    }
                } else {
                    Rectangle2D selectionBounds = null;
                    for (AlignElement e : elements) {
                        if (selectionBounds != null) {
                            selectionBounds.add(e.transform[4], e.transform[5]);
                        } else {
                            selectionBounds = new Rectangle2D.Double(e.transform[4], e.transform[5], 0, 0);
                        }
                    }
                    
                    double cx = selectionBounds.getCenterX();
                    double cy = selectionBounds.getCenterY();

                    for (AlignElement e : elements) {
                        double x = e.transform[4];
                        double y = e.transform[5];                        
                        double dx = x - cx;
                        double dy = y - cy;
                        Point2D r = at.transform(new Point2D.Double(dx, dy), null);
                        double mx = r.getX() + cx;
                        double my = r.getY() + cy;
                        AffineTransform eat = new AffineTransform(e.transform[0], e.transform[1], e.transform[2], e.transform[3], 0, 0);
                        eat.preConcatenate(at);
                        
                        DiagramGraphUtil.changeTransform(graph, e.element, 
                                new double[]{eat.getScaleX(),eat.getShearY(),eat.getShearX(),eat.getScaleY(),mx,my});
                    }
                    
                    if(!connections.isEmpty()) {
                        Command rotateConnection = Commands.get(graph, "Simantics/Diagram/rotateConnection");
                        Resource model = graph.syncRequest(new IndexRoot(connections.get(0)));
                        for(Resource r : connections)
                            rotateConnection.execute(graph, model, r, cx, cy, clockwise);
                    }
                }
            }
        });
    }

    /**
     * Flip specified set of diagram element resources around either the x or
     * y-axis specified by the mass center of the selection bounding box.
     * Each element is considered to weigh an equal amount.
     * 
     * @param resources diagram element resources to flip
     * @param xAxis <code>true</code> to flip around x-axis, <code>false</code>
     *        for y-axis
     */
    public static void flip(final Resource resources[], final boolean xAxis) {
        SimanticsUI.getSession().asyncRequest(new WriteRequest() {
            @Override
            public void perform(WriteGraph graph) throws DatabaseException {
                graph.markUndoPoint();
                IDiagram hints = Diagram.spawnNew(DiagramClass.DEFAULT);
                
                DiagramResource DIA = DiagramResource.getInstance(graph);

                List<AlignElement> elements = new ArrayList<AlignElement>();
                List<Resource> connections = new ArrayList<Resource>();
                for (Resource r : resources) {
                    AlignElement e = create(graph, hints, r);
                    if (e != null)
                        elements.add(e);
                    else if(graph.isInstanceOf(r, DIA.RouteGraphConnection))
                        connections.add(r);
                }
                if (elements.size() < 1)
                    return;

                // Add comment to change set.
                CommentMetadata cm = graph.getMetadata(CommentMetadata.class);
                graph.addMetadata( cm.add("Flip " + elements.size() + " elements " + (xAxis ? "vertically" : "horizontally")) );

                if (elements.size() == 1 && connections.isEmpty()) {
                    for (AlignElement e : elements) {
                        if (xAxis) {
                        	  AffineTransform at = new AffineTransform(e.transform);
                              AffineTransform at2 = AffineTransform.getScaleInstance(1, -1);
                              at.preConcatenate(at2);
                              DiagramGraphUtil.changeTransform(graph, e.element, new double[]{at.getScaleX(),at.getShearY(),at.getShearX(),at.getScaleY(),e.transform[4],e.transform[5]});
                        } else {
                        	 AffineTransform at = new AffineTransform(e.transform);
                             AffineTransform at2 = AffineTransform.getScaleInstance(-1, 1);
                             at.preConcatenate(at2);
                             DiagramGraphUtil.changeTransform(graph, e.element, new double[]{at.getScaleX(),at.getShearY(),at.getShearX(),at.getScaleY(),e.transform[4],e.transform[5]});
                        }
                    }
                } else {

                    Rectangle2D selectionBounds = null;
                    for (AlignElement e : elements) {
                        if (selectionBounds != null) {
                            selectionBounds.add(e.transform[4], e.transform[5]);
                        } else {
                            selectionBounds = new Rectangle2D.Double(e.transform[4], e.transform[5], 0, 0);
                        }
                    }

                    for (AlignElement e : elements) {
                        if (xAxis) {
                            double y = e.transform[5];
                            double cy = selectionBounds.getCenterY();
                            double my = cy + cy - y;
                            AffineTransform at = new AffineTransform(e.transform);
                            AffineTransform at2 = AffineTransform.getScaleInstance(1, -1);
                            at.preConcatenate(at2);
                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{at.getScaleX(),at.getShearY(),at.getShearX(),at.getScaleY(),e.transform[4],my});
                        } else {
                            double x = e.transform[4];
                            double cx = selectionBounds.getCenterX();
                            double mx = cx + cx - x;
                            
                            AffineTransform at = new AffineTransform(e.transform);
                            AffineTransform at2 = AffineTransform.getScaleInstance(-1, 1);
                            at.preConcatenate(at2);
                            DiagramGraphUtil.changeTransform(graph, e.element, new double[]{at.getScaleX(),at.getShearY(),at.getShearX(),at.getScaleY(),mx,e.transform[5]});
                        }
                    }
                    
                    if(!connections.isEmpty()) {
                        Command flipConnection = Commands.get(graph, "Simantics/Diagram/flipConnection");
                        Resource model = graph.syncRequest(new IndexRoot(connections.get(0)));
                        for(Resource r : connections)
                            flipConnection.execute(graph, model, r, xAxis, 
                                    xAxis ? selectionBounds.getCenterY() 
                                            : selectionBounds.getCenterX());
                    }
                }

            }
        });
    }

    private static AlignElement create(ReadGraph graph, IDiagram hints, Resource r) throws ManyObjectsForFunctionalRelationException, NoSingleResultException, ServiceException, DatabaseException {
        DiagramResource dr = DiagramResource.getInstance(graph);

        if (graph.isInstanceOf(r, dr.Element) && !graph.isInstanceOf(r, dr.Connection) /*&& !graph.isInstanceOf(r, dr.Monitor)*/) {
            double transform[] = graph.getPossibleRelatedValue(r, dr.HasTransform);
            ElementClass ec = graph.syncRequest(DiagramRequests.getElementClass(graph.getSingleType(r, dr.Element), hints));
            IElement e = Element.spawnNew(ec);
            Rectangle2D bounds = ElementUtils.getElementBounds(e);
            if (transform != null && bounds != null) {
                return new AlignElement(r, transform, bounds);
            }
        }
        return null;
    }


    private static class AlignElement {
        public Resource element;
        public double[] transform;
        public Rectangle2D bounds;
        public Rectangle2D rotatedBounds;
//        public Rectangle2D transformedBounds;

        public AlignElement(Resource element, double[] transform, Rectangle2D bounds) {
            this.element = element;
            this.transform = transform;
            this.bounds = bounds;
//            this.transformedBounds = getBounds();
            this.rotatedBounds = getRotatedBounds();
        }

//        public Rectangle2D getBounds() {
//            AffineTransform at = new AffineTransform(transform[0], transform[1], transform[2], transform[3], transform[4], transform[5]);
//            return GeometryUtils.transformShape(bounds, at).getBounds2D();
//        }

        public Rectangle2D getRotatedBounds() {
            AffineTransform at = new AffineTransform(transform[0], transform[1], transform[2], transform[3], 0.0, 0.0);
            return GeometryUtils.transformShape(bounds, at).getBounds2D();
        }

        public double getDeterminant() {
            return transform[0] * transform[3] - transform[1] * transform[2];
        }

    }

    private static class XComparator implements Comparator<AlignElement> {
        @Override
        public int compare(AlignElement o1, AlignElement o2) {
            if (o1.transform[4] < o2.transform[4])
                return -1;
            if (o1.transform[4] > o2.transform[4])
                return 1;
            return 0;

        }
    }

    private static class YComparator implements Comparator<AlignElement> {
        @Override
        public int compare(AlignElement o1, AlignElement o2) {
            if (o1.transform[5] < o2.transform[5])
                return -1;
            if (o1.transform[5] > o2.transform[5])
                return 1;
            return 0;

        }
    }

    /**
     * Set 2D affine transforms for the listed diagram element resources.
     * 
     * @param elements diagram element resources to set transforms for
     * @param transforms transforms for each element
     */
    public static Write setTransformRequest(final Collection<TransformedObject> elements)
    {
        return new WriteRequest() {
            @Override
            public void perform(WriteGraph graph) throws DatabaseException {
                for (TransformedObject element : elements)
                    DiagramGraphUtil.changeTransform(graph, element.element, element.transform);
            }
        };
    }

    /**
     * Set 2D affine transforms for the listed diagram element resources.
     * 
     * @param undoContext the database undo context to use for the returned
     *        request
     * @param elements diagram element resources to set transforms for
     * @param transforms transforms for each element
     * @param preConcatenate <code>true</code> to pre-concatenate the
     *        transforms, <code>false</code> to concatenate
     */
    public static Write concatenateTransformRequest(
            UndoContext undoContext,
            final Collection<TransformedObject> elements,
            final boolean preConcatenate)
    {
        return new WriteRequest() {
            @Override
            public void perform(WriteGraph graph) throws DatabaseException {
                for (TransformedObject element : elements) {
                    AffineTransform at = DiagramGraphUtil.getTransform(graph, element.element);
                    if (preConcatenate)
                        at.preConcatenate(element.transform);
                    else
                        at.concatenate(element.transform);
                    DiagramGraphUtil.setTransform(graph, element.element, at);
                }
            }
        };
    }

    public static class TransformedObject {
        public final Resource        element;
        public final AffineTransform transform;

        public TransformedObject(Resource element) {
            this.element = element;
            this.transform = new AffineTransform();
        }
        public TransformedObject(Resource element, AffineTransform transform) {
            this.element = element;
            this.transform = transform;
        }
    }

}