/*******************************************************************************
 * Copyright (c) 2004 Actuate Corporation.
 * 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:
 *  Actuate Corporation  - initial API and implementation
 *******************************************************************************/

package org.eclipse.birt.report.designer.internal.ui.dnd;

import java.util.ArrayList;
import java.util.List;

import org.eclipse.birt.report.designer.internal.ui.util.Policy;
import org.eclipse.birt.report.model.api.ThemeHandle;
import org.eclipse.gef.dnd.TemplateTransfer;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.StructuredViewer;
import org.eclipse.swt.dnd.DragSourceAdapter;
import org.eclipse.swt.dnd.DragSourceEvent;

/**
 * Supports dragging elements in outline view.
 */

public abstract class DesignElementDragAdapter extends DragSourceAdapter
{

	private StructuredViewer viewer;

	// added this member to fix bug 116180
	private List selectionList = new ArrayList( );

	/**
	 * Constructor
	 * 
	 * @param viewer
	 */
	public DesignElementDragAdapter( StructuredViewer viewer )
	{
		super( );
		this.viewer = viewer;
	}

	/**
	 * @see DragSourceAdapter#dragFinished(DragSourceEvent)
	 */
	public void dragFinished( DragSourceEvent event )
	{
		if ( event.doit )
		{
			TemplateTransfer.getInstance( ).setTemplate( null );
			if ( Policy.TRACING_DND_DRAG )
			{
				System.out.println( "DND >> Drag finished." ); //$NON-NLS-1$
			}
		}
	}

	/**
	 * @see DragSourceAdapter#dragSetData(DragSourceEvent)
	 */
	public void dragSetData( DragSourceEvent event )
	{
//		IStructuredSelection selection = (IStructuredSelection) getViewer( ).getSelection( );
//		Object[] objects = selection.toList( ).toArray( );

		// fix bug 116180
		Object[] objects = selectionList.toArray( );
		if ( TemplateTransfer.getInstance( ).isSupportedType( event.dataType ) )
			event.data = objects;
	}

	/**
	 * @see DragSourceAdapter#dragStart(DragSourceEvent)
	 */
	public void dragStart( DragSourceEvent event )
	{
		boolean doit = !getViewer( ).getSelection( ).isEmpty( );
		if ( doit )
		{
			IStructuredSelection selection = (IStructuredSelection) getViewer( ).getSelection( );
			selectionList = selection.toList( );
			Object[] objects = selection.toList( ).toArray( );
			if ( validateType( objects ) )
			{
				for ( int i = 0; i < objects.length; i++ )
					if ( !validateTransfer( objects[i] ) )
					{
						doit = false;
						break;
					}
			}
			else
				doit = false;
			if ( doit )
				TemplateTransfer.getInstance( ).setTemplate( objects );
		}
		event.doit = doit;
		if ( Policy.TRACING_DND_DRAG && doit )
		{
			System.out.println( "DND >> Drag starts." ); //$NON-NLS-1$
		}
	}

	/**
	 * Validates every transfer element
	 * 
	 * @param transfer
	 *            every transfer element
	 * @return if transfer element can be dragged
	 */
	protected abstract boolean validateTransfer( Object transfer );

	/**
	 * Validates types of transfer elements.
	 * <p>
	 * Default implementation is verify all types of transfer elements are same
	 * 
	 * @param transfer
	 *            transfer elements
	 * @return type is same or not
	 */
	protected boolean validateType( Object transfer )
	{
		Object[] objects = (Object[]) transfer;
		if ( objects.length <= 0 )
		{
			return false;
		}

		// Theme can be draged when only one is selected. Fix bug #151953
		if ( objects[0] instanceof ThemeHandle )
		{
			if ( objects.length == 1 )
			{
				return true;
			}
			else
			{
				return false;
			}
		}

		// Drag the elements if selected ones are the same type.
		Class type = null;
		for ( int i = 0; i < objects.length; i++ )
		{
			if ( type == null )
				type = objects[i].getClass( );
			else if ( !type.equals( objects[i].getClass( ) ) )
				return false;
		}
		return true;
	}

	/**
	 * Returns viewer
	 * 
	 * @return viewer
	 */
	protected StructuredViewer getViewer( )
	{
		return viewer;
	}
}