/*******************************************************************************
 * Copyright (c) 2000, 2011 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jdt.internal.ui.dnd;

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

import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.DragSourceAdapter;
import org.eclipse.swt.dnd.DragSourceEvent;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.widgets.Shell;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IAdaptable;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.MultiStatus;

import org.eclipse.core.resources.IResource;

import org.eclipse.jface.dialogs.ErrorDialog;
import org.eclipse.jface.util.TransferDragSourceListener;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.jface.viewers.IStructuredSelection;

import org.eclipse.ui.part.ResourceTransfer;

import org.eclipse.jdt.core.IJavaElement;

import org.eclipse.jdt.internal.corext.util.Messages;

import org.eclipse.jdt.internal.ui.IJavaStatusConstants;
import org.eclipse.jdt.internal.ui.JavaPlugin;
import org.eclipse.jdt.internal.ui.JavaUIMessages;
import org.eclipse.jdt.internal.ui.util.SWTUtil;

/**
 * A drag adapter that transfers the current selection as </code>
 * IResource</code>. Only those elements in the selection are part
 * of the transfer which can be converted into an <code>IResource
 * </code>.
 */
public class ResourceTransferDragAdapter extends DragSourceAdapter implements TransferDragSourceListener {

	private ISelectionProvider fProvider;

	private static final List<IResource> EMPTY_LIST= new ArrayList<>(0);

	/**
	 * Creates a new ResourceTransferDragAdapter for the given selection
	 * provider.
	 *
	 * @param provider the selection provider to access the viewer's selection
	 */
	public ResourceTransferDragAdapter(ISelectionProvider provider) {
		fProvider= provider;
		Assert.isNotNull(fProvider);
	}

	@Override
	public Transfer getTransfer() {
		return ResourceTransfer.getInstance();
	}

	@Override
	public void dragStart(DragSourceEvent event) {
		event.doit= convertSelection().size() > 0;
	}

	@Override
	public void dragSetData(DragSourceEvent event) {
		List<IResource> resources= convertSelection();
		event.data= resources.toArray(new IResource[resources.size()]);
	}

	@Override
	public void dragFinished(DragSourceEvent event) {
		if (!event.doit)
			return;

		if (event.detail == DND.DROP_MOVE) {
			handleFinishedDropMove(event);
		}
	}

	private List<IResource> convertSelection() {
		ISelection s= fProvider.getSelection();
		if (!(s instanceof IStructuredSelection))
			return EMPTY_LIST;
		IStructuredSelection selection= (IStructuredSelection)s;
		List<IResource> result= new ArrayList<>(selection.size());
		for (Object element : selection) {
			IResource resource= null;
			if (element instanceof IJavaElement) {
				// don't use IAdaptable as for members only the top level type adapts
				resource= ((IJavaElement) element).getResource();
			} else if (element instanceof IAdaptable) {
				resource= ((IAdaptable) element).getAdapter(IResource.class);
			}
			if (resource != null)
				result.add(resource);
		}
		return result;
	}

	private void handleFinishedDropMove(DragSourceEvent event) {
		MultiStatus status= new MultiStatus(
			JavaPlugin.getPluginId(),
			IJavaStatusConstants.INTERNAL_ERROR,
			JavaUIMessages.ResourceTransferDragAdapter_cannot_delete_resource,
			null);
		List<IResource> resources= convertSelection();
		for (IResource resource : resources) {
			try {
				resource.delete(true, null);
			} catch (CoreException e) {
				status.add(e.getStatus());
			}
		}
		int childrenCount= status.getChildren().length;
		if (childrenCount > 0) {
			Shell parent= SWTUtil.getShell(event.widget);
			ErrorDialog error= new ErrorDialog(parent,
					JavaUIMessages.ResourceTransferDragAdapter_moving_resource,
					childrenCount == 1 ? JavaUIMessages.ResourceTransferDragAdapter_cannot_delete_files_singular : Messages.format(
							JavaUIMessages.ResourceTransferDragAdapter_cannot_delete_files_plural, String.valueOf(childrenCount)), status, IStatus.ERROR);
			error.open();
		}
	}
}

