/*******************************************************************************
 * Copyright (c) 2000, 2017 IBM Corporation and others.
 * 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
 *
 *******************************************************************************/
package org.eclipse.dltk.internal.ui.dnd;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import org.eclipse.core.resources.IResource;
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.dltk.core.IModelElement;
import org.eclipse.dltk.core.IModelStatusConstants;
import org.eclipse.dltk.internal.ui.DLTKUIMessages;
import org.eclipse.dltk.internal.ui.util.SWTUtil;
import org.eclipse.dltk.ui.DLTKUIPlugin;
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.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.ui.part.ResourceTransfer;

/**
 * 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;

	/**
	 * 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;
	}

	@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 Collections.emptyList();
		IStructuredSelection selection = (IStructuredSelection) s;
		List<IResource> result = new ArrayList<>(selection.size());
		for (Iterator iter = selection.iterator(); iter.hasNext();) {
			Object element = iter.next();
			IResource resource = null;
			if (element instanceof IModelElement) {
				// don't use IAdaptable as for members only the top level type
				// adapts
				resource = ((IModelElement) 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(DLTKUIPlugin.PLUGIN_ID,
				IModelStatusConstants.INTERNAL_ERROR,
				DLTKUIMessages.ResourceTransferDragAdapter_cannot_delete_resource,
				null);
		List<IResource> resources = convertSelection();
		for (Iterator<IResource> iter = resources.iterator(); iter.hasNext();) {
			IResource resource = iter.next();
			try {
				resource.delete(true, null);
			} catch (CoreException e) {
				status.add(e.getStatus());
			}
		}
		if (status.getChildren().length > 0) {
			Shell parent = SWTUtil.getShell(event.widget);
			ErrorDialog error = new ErrorDialog(parent,
					DLTKUIMessages.ResourceTransferDragAdapter_moving_resource,
					DLTKUIMessages.ResourceTransferDragAdapter_cannot_delete_files,
					status, IStatus.ERROR);
			error.open();
		}
	}
}