/*******************************************************************************
 * Copyright (c) 2000, 2015 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
 *     Andrey Loskutov <loskutov@gmx.de> - Bug 205678
 *******************************************************************************/
package org.eclipse.ui.part;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import org.eclipse.core.resources.IResource;
import org.eclipse.core.resources.IWorkspace;
import org.eclipse.core.resources.ResourcesPlugin;
import org.eclipse.core.runtime.IPath;
import org.eclipse.jface.util.Util;
import org.eclipse.swt.dnd.ByteArrayTransfer;
import org.eclipse.swt.dnd.TransferData;
import org.eclipse.ui.internal.ide.IDEWorkbenchPlugin;

/**
 * The <code>ResourceTransfer</code> class is used to transfer an array of
 * <code>IResource</code>s from one part to another in a drag and drop operation
 * or a cut, copy, paste action.
 * <p>
 * In every drag and drop operation there is a <code>DragSource</code> and a
 * <code>DropTarget</code>. When a drag occurs a <code>Transfer</code> is used
 * to marshal the drag data from the source into a byte array. If a drop occurs
 * another <code>Transfer</code> is used to marshal the byte array into drop
 * data for the target.
 * </p>
 * <p>
 * When a <code>CutAction</code> or a <code>CopyAction</code> is performed, this
 * transfer is used to place references to the selected resources on the
 * <code>Clipboard</code>. When a <code>PasteAction</code> is performed, the
 * references on the clipboard are used to move or copy the resources to the
 * selected destination.
 * </p>
 * <p>
 * This class can be used for a <code>Viewer</code> or an SWT component
 * directly. A singleton is provided which may be serially reused (see
 * <code>getInstance</code>). It is not intended to be subclassed.
 * </p>
 * <p>
 * The amount of resources which can be transferred is limited to
 * <code>MAX_RESOURCES_TO_TRANSFER</code> elements.
 * </p>
 *
 * @see org.eclipse.jface.viewers.StructuredViewer
 * @see org.eclipse.swt.dnd.DropTarget
 * @see org.eclipse.swt.dnd.DragSource
 * @noextend This class is not intended to be subclassed by clients.
 */
public class ResourceTransfer extends ByteArrayTransfer {

	/**
	 * See bug 205678: sometimes we can misinterpret native data received from
	 * clipboard. No one seriously would copy/paste or drag/drop more then
	 * 100.000 resources: only creating an *empty* array of 100.000.000
	 * resources will cause OOME on 512 MB heap size (default for shipped
	 * Eclipse packages), same with copy/paste of a *full* array of 10.000.000
	 * elements.
	 */
	private static final int MAX_RESOURCES_TO_TRANSFER = 1000 * 1000;

	/**
	 * Singleton instance.
	 */
	private static final ResourceTransfer instance = new ResourceTransfer();

	// Create a unique ID to make sure that different Eclipse
	// applications use different "types" of <code>ResourceTransfer</code>
	private static final String TYPE_NAME = "resource-transfer-format:" + System.currentTimeMillis() + ":" + instance.hashCode();//$NON-NLS-2$//$NON-NLS-1$

	private static final int TYPEID = registerType(TYPE_NAME);

	private IWorkspace workspace = ResourcesPlugin.getWorkspace();

	/**
	 * Creates a new transfer object.
	 */
	private ResourceTransfer() {
	}

	/**
	 * Returns the singleton instance.
	 *
	 * @return the singleton instance
	 */
	public static ResourceTransfer getInstance() {
		return instance;
	}

	@Override
	protected int[] getTypeIds() {
		return new int[] { TYPEID };
	}

	@Override
	protected String[] getTypeNames() {
		return new String[] { TYPE_NAME };
	}

	@Override
	protected void javaToNative(Object data, TransferData transferData) {
		if (!(data instanceof IResource[])) {
			return;
		}

		IResource[] resources = (IResource[]) data;
		/**
		 * The resource serialization format is:
		 *  (int) number of resources
		 * Then, the following for each resource:
		 *  (int) resource type
		 *  (String) path of resource
		 */

		int resourceCount = resources.length;

		try {
			ByteArrayOutputStream out = new ByteArrayOutputStream();
			DataOutputStream dataOut = new DataOutputStream(out);

			//write the number of resources
			dataOut.writeInt(resourceCount);

			//write each resource
			for (IResource resource : resources) {
				writeResource(dataOut, resource);
			}

			//cleanup
			dataOut.close();
			out.close();
			byte[] bytes = out.toByteArray();
			super.javaToNative(bytes, transferData);
		} catch (IOException e) {
			//it's best to send nothing if there were problems
		}
	}

	@Override
	protected Object nativeToJava(TransferData transferData) {
		/**
		 * The resource serialization format is:
		 *  (int) number of resources
		 * Then, the following for each resource:
		 *  (int) resource type
		 *  (String) path of resource
		 */

		byte[] bytes = (byte[]) super.nativeToJava(transferData);
		if (bytes == null) {
			return null;
		}
		DataInputStream in = new DataInputStream(
				new ByteArrayInputStream(bytes));
		try {
			int count = in.readInt();
			if (count > MAX_RESOURCES_TO_TRANSFER) {
				String message = "Transfer aborted, too many resources: " + count + "."; //$NON-NLS-1$ //$NON-NLS-2$
				if (Util.isLinux()) {
					message += "\nIf you are running in x11vnc environment please consider to switch to vncserver " + //$NON-NLS-1$
							"+ vncviewer or to run x11vnc without clipboard support " + //$NON-NLS-1$
							"(use '-noclipboard' and '-nosetclipboard' arguments)."; //$NON-NLS-1$
				}
				IDEWorkbenchPlugin.log(message, new IllegalArgumentException(
						"Maximum limit of resources to transfer is: " + MAX_RESOURCES_TO_TRANSFER)); //$NON-NLS-1$
				return null;
			}
			IResource[] results = new IResource[count];
			for (int i = 0; i < count; i++) {
				results[i] = readResource(in);
			}
			return results;
		} catch (IOException e) {
			return null;
		}
	}

	/**
	 * Reads a resource from the given stream.
	 *
	 * @param dataIn the input stream
	 * @return the resource
	 * @exception IOException if there is a problem reading from the stream
	 */
	private IResource readResource(DataInputStream dataIn) throws IOException {
		int type = dataIn.readInt();
		String path = dataIn.readUTF();
		switch (type) {
		case IResource.FOLDER:
			return workspace.getRoot().getFolder(IPath.fromOSString(path));
		case IResource.FILE:
			return workspace.getRoot().getFile(IPath.fromOSString(path));
		case IResource.PROJECT:
			return workspace.getRoot().getProject(path);
		}
		throw new IllegalArgumentException(
				"Unknown resource type in ResourceTransfer.readResource"); //$NON-NLS-1$
	}

	/**
	 * Writes the given resource to the given stream.
	 *
	 * @param dataOut the output stream
	 * @param resource the resource
	 * @exception IOException if there is a problem writing to the stream
	 */
	private void writeResource(DataOutputStream dataOut, IResource resource)
			throws IOException {
		dataOut.writeInt(resource.getType());
		dataOut.writeUTF(resource.getFullPath().toString());
	}
}
