EDIT

package eu.etaxonomy.taxeditor.navigation.navigator;

import java.util.Arrays;

import java.util.Comparator;

import java.util.HashMap;

import java.util.Iterator;

import java.util.LinkedHashSet;

import java.util.Map;

import java.util.Set;

import org.eclipse.jface.util.LocalSelectionTransfer;

import org.eclipse.jface.viewers.IStructuredSelection;

import org.eclipse.swt.dnd.TransferData;

import org.eclipse.ui.internal.navigator.dnd.CommonDropAdapterDescriptor;

import org.eclipse.ui.internal.navigator.dnd.CommonDropDescriptorManager;

import org.eclipse.ui.internal.navigator.extensions.CommonDragAssistantDescriptor;

import org.eclipse.ui.internal.navigator.extensions.NavigatorViewerDescriptor;

import org.eclipse.ui.navigator.CommonDragAdapterAssistant;

import org.eclipse.ui.navigator.CommonDropAdapter;

import org.eclipse.ui.navigator.CommonDropAdapterAssistant;

import org.eclipse.ui.navigator.INavigatorContentService;

import org.eclipse.ui.navigator.INavigatorDnDService;

import eu.etaxonomy.taxeditor.navigation.navigator.dnd.TaxonNavigatorDragAdapterAssistant;

public class TaxonNavigatorDnDService implements INavigatorDnDService {

	private static final CommonDropAdapterAssistant[] NO_ASSISTANTS = new CommonDropAdapterAssistant[0];

	private INavigatorContentService contentService;

	private TaxonNavigatorDragAdapterAssistant[] dragAssistants;

	private TreeNodeDropAdapter dropAdapter;

	private final Map dropAssistants = new HashMap();

	public TaxonNavigatorDnDService(INavigatorContentService contentService){

		this.contentService = contentService;

	}

	@Override

	public CommonDragAdapterAssistant[] getCommonDragAssistants() {

		return dragAssistants;

	}

	@Override

	public void bindDragAssistant(CommonDragAdapterAssistant anAssistant) {

		if(dragAssistants == null) 

			initializeDragAssistants(); 

		TaxonNavigatorDragAdapterAssistant[] newDragAssistants = new TaxonNavigatorDragAdapterAssistant[dragAssistants.length + 1];

		System.arraycopy(dragAssistants, 0, newDragAssistants, 0, dragAssistants.length);

		newDragAssistants[dragAssistants.length] = (TaxonNavigatorDragAdapterAssistant) anAssistant;

		dragAssistants = newDragAssistants;		

	}

	private void initializeDragAssistants() {

		int i = 0;

		Set dragDescriptors = ((NavigatorViewerDescriptor) contentService

				.getViewerDescriptor()).getDragAssistants();

		dragAssistants = new TaxonNavigatorDragAdapterAssistant[dragDescriptors

				.size()];

		for (Iterator iter = dragDescriptors.iterator(); iter.hasNext();) {

			CommonDragAssistantDescriptor descriptor = (CommonDragAssistantDescriptor) iter

					.next();

			dragAssistants[i++] = (TaxonNavigatorDragAdapterAssistant) descriptor.createDragAssistant();

		}

	}

	@Override

	public CommonDropAdapterAssistant[] findCommonDropAdapterAssistants(

			Object aDropTarget, TransferData aTransferType) {

		CommonDropAdapterDescriptor[] descriptors = CommonDropDescriptorManager

				.getInstance().findCommonDropAdapterAssistants(aDropTarget,

						contentService);

		if (descriptors.length == 0) {

			return NO_ASSISTANTS;

		}

		if (LocalSelectionTransfer.getTransfer().isSupportedType(aTransferType)  

						&& LocalSelectionTransfer.getTransfer().getSelection() instanceof IStructuredSelection) {

			return getAssistantsBySelection(descriptors, (IStructuredSelection) LocalSelectionTransfer.getTransfer().getSelection());

		} 

		return getAssistantsByTransferData(descriptors, aTransferType);

	}

	private CommonDropAdapterAssistant[] getAssistantsByTransferData(

			CommonDropAdapterDescriptor[] descriptors,

			TransferData aTransferType) {

		Set assistants = new LinkedHashSet();

		for (int i = 0; i < descriptors.length; i++) {

			CommonDropAdapterAssistant asst = getAssistant(descriptors[i]);

			if (asst.isSupportedType(aTransferType)) {

				assistants.add(asst);

			}

		}

		return sortAssistants((CommonDropAdapterAssistant[]) assistants

				.toArray(new CommonDropAdapterAssistant[assistants.size()]));

	}

	private CommonDropAdapterAssistant[] getAssistantsBySelection(

			CommonDropAdapterDescriptor[] descriptors, IStructuredSelection aSelection) {

		Set assistants = new LinkedHashSet(); 

		for (int i = 0; i < descriptors.length; i++) {

			if(descriptors[i].areDragElementsSupported(aSelection)) {

				assistants.add(getAssistant(descriptors[i]));

			}

		}  

		return sortAssistants((CommonDropAdapterAssistant[]) assistants

				.toArray(new CommonDropAdapterAssistant[assistants.size()]));

	}

	private CommonDropAdapterAssistant getAssistant(

			CommonDropAdapterDescriptor descriptor) {

		TreeNodeDropAdapterAssistant asst = (TreeNodeDropAdapterAssistant) dropAssistants

				.get(descriptor);

		if (asst != null) {

			return asst;

		}

		synchronized (dropAssistants) {

			asst = (TreeNodeDropAdapterAssistant) dropAssistants.get(descriptor);

			if (asst == null) {

				dropAssistants.put(descriptor, (asst = (TreeNodeDropAdapterAssistant) descriptor

						.createDropAssistant()));

				asst.init(contentService);

				//asst.setCommonDropAdapter(dropAdapter);

			}

		}

		return asst;

	}

	private CommonDropAdapterAssistant[] sortAssistants(CommonDropAdapterAssistant[] array) {

		Arrays.sort(array, new Comparator() {

			public int compare(Object arg0, Object arg1) {

				CommonDropAdapterAssistant a = (CommonDropAdapterAssistant) arg0;

				CommonDropAdapterAssistant b = (CommonDropAdapterAssistant) arg1;

				// This is to ensure that the navigator resources drop assistant will

				// always be first on the list of drop assistant, if a conflict ever 

				// occurs.

				String id = "org.eclipse.ui.navigator.resources."; //$NON-NLS-1$

				if (a.getClass().getName().startsWith(id))

					return -1;

				if (b.getClass().getName().startsWith(id))

					return 1;

				return a.getClass().getName().compareTo(b.getClass().getName());

			}

		});

		return array;

	}

	@Override

	public CommonDropAdapterAssistant[] findCommonDropAdapterAssistants(

			Object aDropTarget, IStructuredSelection theDragSelection) {

		// TODO Auto-generated method stub

		return null;

	}

	public void setDropAdaptor(TreeNodeDropAdapter da) {

		dropAdapter = da;

	}

}