// This Source Code is Copyright & Licenced as indicated below
package org.litesoft.GWT.client.widgets.nonpublic.external;
/*
 * Copyright 2007 Mat Gessel <mat.gessel@gmail.com>
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

import com.google.gwt.core.client.*;
import com.google.gwt.user.client.*;

/**
 * Converts {@link MouseEvent}s to {@link DragEvent}s and delegates to the
 * specified {@link DragGesture}.
 */
public class MouseDragHandler extends MouseHandlerAdaptor
{
    private static MouseDragHandlerImpl s_Impl = (MouseDragHandlerImpl) GWT.create( MouseDragHandlerImpl.class );

    private DragGesture m_dragGesture;
    private MouseEvent m_mouseDown = null;
    private MouseEvent m_previousEvent = null;

    public MouseDragHandler( DragGesture dragGesture )
    {
        super( Event.ONMOUSEDOWN | Event.ONMOUSEMOVE | Event.ONMOUSEUP );
        m_dragGesture = dragGesture;
    }

    protected MouseEvent getMouseDown()
    {
        return m_mouseDown;
    }

    protected MouseEvent getPreviousEvent()
    {
        return m_previousEvent;
    }

    /**
     * Get the delegate object which will handle drag operations.
     */
    public DragGesture getDragGesture()
    {
        return m_dragGesture;
    }

    /**
     * Set the delegate object which will handle drag operations.
     */
    public void setDragGesture( DragGesture dragGesture )
    {
        m_dragGesture = dragGesture;
    }

    @Override
    public void onMouseDown( MouseEvent e )
    {
        DOM.eventCancelBubble( e.getDomEvent(), true );
        s_Impl.onMouseDown( e.getDomEvent() );

        if ( m_dragGesture != null )
        {
            m_mouseDown = e;
            m_dragGesture.start( e );
            m_previousEvent = e;
        }
    }

    @Override
    public void onMouseMove( MouseEvent e )
    {
        if ( m_mouseDown != null )
        {
            m_dragGesture.step( new DragEvent( e, m_mouseDown, m_previousEvent ) );
            m_previousEvent = e;
        }
    }

    @Override
    public void onMouseUp( MouseEvent e )
    {
        // it is possible to get a mouse up without a mouse down
        if ( m_mouseDown != null )
        {
            // clear MD first to prevent reentrancy
            m_mouseDown = null;
            m_dragGesture.finish();
            m_previousEvent = null;
        }

        if ( e != null )
        {
            s_Impl.onMouseUp( e.getDomEvent() );
        }
    }

    protected static class MouseDragHandlerImpl
    {
        public void onMouseDown( Event event )
        {
            // prevents text selection and image dragging in Mozilla, Safari & Opera
            DOM.eventPreventDefault( event );
        }

        public void onMouseUp( Event event )
        {
        }
    }

    protected static class MouseDragHandlerImplIE6 extends MouseDragHandlerImpl
    {
        @Override
        public native void onMouseDown( Event event ) /*-{
            $doc.body.onselectstart = function()
            {
                return false;
            };
            $doc.body.ondragstart = function()
            {
                return false;
            };
        }-*/;

        @Override
        public native void onMouseUp( Event event ) /*-{
            $doc.body.onselectstart = null;
            $doc.body.ondragstart = null;
        }-*/;
    }
}