/*******************************************************************************
 * 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.Component;
import java.awt.Point;
import java.awt.dnd.DropTarget;
import java.awt.dnd.DropTargetDragEvent;
import java.awt.dnd.DropTargetDropEvent;
import java.awt.dnd.DropTargetEvent;
import java.awt.dnd.DropTargetListener;
import java.awt.geom.Point2D;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;

import org.simantics.g2d.canvas.ICanvasContext;
import org.simantics.g2d.canvas.impl.AbstractCanvasParticipant;


/**
 * This participant handles drop operations of a canvas.
 * 
 * To implement a drop operation add an implementation of {@link IDropTargetParticipant} to the canvas.
 * 
 * Intantiates DragPainter for the duration of drag operations.
 * 
 * DropInteractor is added by chassis.
 */
public class DropInteractor extends AbstractCanvasParticipant implements DropTargetListener {

    private final Component component;
    @SuppressWarnings("unused")
    private DropTarget dropTarget;
    private DnDContext dropCtx;
    int allowedOps;

    /**
     * Create new abstract drop interactor
     * @param context
     * @param component
     * @param ops  see DnDConstants
     */
    public DropInteractor(Component component) {
        super();
        this.component = component;
    }

    @Override
    public void addedToContext(ICanvasContext ctx) {
        super.addedToContext(ctx);
        installDropTarget();
    }

    @Override
    public void removedFromContext(ICanvasContext ctx) {
        super.removedFromContext(ctx);
        component.setDropTarget(null);
    }

    private int getAllowedOps() {
        int result = 0;
        for (IDropTargetParticipant p : getDropParticipants())
            result |= p.getAllowedOps();
        return result;
    }

    void installDropTarget() {
        allowedOps = getAllowedOps();
        dropTarget = new DropTarget(component, allowedOps, this);
    }

    protected Collection<IDropTargetParticipant> getDropParticipants() {
    	ArrayList<IDropTargetParticipant> participants = new ArrayList<IDropTargetParticipant>(getContext().getItemsByClass(IDropTargetParticipant.class));
    	Collections.sort(participants, new Comparator<IDropTargetParticipant>() {
			@Override
			public int compare(IDropTargetParticipant o1, IDropTargetParticipant o2) {
				return Double.compare(o2.getPriority(), o1.getPriority());
			}
		});
    	return participants;
    }

    IDropTargetParticipant dropAccepter = null;
    private DragPainter currentDragPainter;

    public Collection<DragPainter> getDragPainters() {
        return getContext().getItemsByClass(DragPainter.class);
    }

    @Override
    public void dragEnter(final DropTargetDragEvent dtde) {
        dropAccepter = null;
        final Collection<IDropTargetParticipant> participants = getDropParticipants();
        if (participants.isEmpty()) {
            dtde.rejectDrag();
            return;
        }
        dropCtx = new DnDContext();
        syncExec(new Runnable() {
            @Override
            public void run() {
                for (IDropTargetParticipant p : participants) {
                    p.dragEnter(dtde, dropCtx);
                    if (dropCtx.toArray().length > 0) {
                        dropAccepter = p;
                        break;
                    }

                }
            }});

        if (dropCtx.toArray().length==0)
            dtde.rejectDrag();
        else
            dtde.acceptDrag(dtde.getDropAction());

        // if drag is accepted, start drag interactor
        Point mouseLocation = dtde.getLocation();
        Point2D mouseControlPos = new Point2D.Double(mouseLocation.getX(), mouseLocation.getY());
        currentDragPainter = new DragPainter(dropCtx, mouseControlPos);
        getContext().add(currentDragPainter);

        setDirty();
    }

    @Override
    public void dragExit(final DropTargetEvent dte) {
        syncExec(new Runnable() {
            @Override
            public void run() {
                if (dropAccepter != null)
                    dropAccepter.dragExit(dte, dropCtx);
//                final Collection<IDropTargetParticipant> participants = getDropParticipants();
//                for (IDropTargetParticipant p : participants)
//                    p.dragExit(dte, dropCtx);

                endDrag();
            }
        });
    }



    @Override
    public void dragOver(final DropTargetDragEvent dtde) {
        final Collection<DragPainter> interactors = getDragPainters();
        if (interactors.isEmpty()) {
            dtde.rejectDrag();
            return;
        }

        syncExec(new Runnable() {
            @Override
            public void run() {
                Point mouseLocation = dtde.getLocation();
                Point2D mouseControlPos = new Point2D.Double(mouseLocation.getX(), mouseLocation.getY());
                for (DragPainter interactor : interactors)
                    interactor.setMousePos( mouseControlPos );

                if (dropAccepter != null)
                    dropAccepter.dragOver(dtde, dropCtx);
//                final Collection<IDropTargetParticipant> participants = getDropParticipants();
//                for (IDropTargetParticipant p : participants)
//                    p.dragOver(dtde, dropCtx);

            }
        });
    }

    @Override
    public void drop(final DropTargetDropEvent dtde) {
//        ITask task = ThreadLogger.getInstance().begin("Drop");
        final Collection<DragPainter> interactors = getDragPainters();
        if (interactors.isEmpty()) {
            dtde.rejectDrop();
            return;
        }

        // Try to make sure that all DragItems have a position
        // before invoking IDropTargetParticipant.drop.
        Point mouseLocation = dtde.getLocation();
        Point2D mouseControlPos = new Point2D.Double(mouseLocation.getX(), mouseLocation.getY());
        for (DragPainter interactor : interactors)
            interactor.setMousePos( mouseControlPos, true );

        // Remove drag painter before dropping just to prevent it from
        // doing anything with the DNDContext after this point.
        if (currentDragPainter != null) {
            getContext().remove(currentDragPainter);
            currentDragPainter = null;
        }

        syncExec(new Runnable() {
            @Override
            public void run() {
//                DragPainter painter = getDragPainter();
                if (dropAccepter != null)
                    dropAccepter.drop(dtde, dropCtx);
//                final Collection<IDropTargetParticipant> participants = getDropParticipants();
//                for (IDropTargetParticipant p : participants)
//                    p.drop(dtde, dropCtx);

                endDrag();
            }
        });
        //dtde.acceptDrop(dtde.getDropAction());
//        task.finish();
    }

    @Override
    public void dropActionChanged(DropTargetDragEvent dtde) {
        //System.out.println("dropActionChanged: "+dtde.getDropAction());
        // remove interactor when action is canceled
    }

    public void endDrag()
    {
        Collection<DragPainter> dragPainters = getContext().getItemsByClass(DragPainter.class);
        if (dragPainters.isEmpty()) return;
        for (DragPainter dp : dragPainters)
            dp.remove();
        dropAccepter = null;
        setDirty();
    }

}