/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.part;

import java.io.*;

import org.eclipse.core.resources.*;
import org.eclipse.core.runtime.Path;
import org.eclipse.swt.dnd.ByteArrayTransfer;
import org.eclipse.swt.dnd.TransferData;

/**
 * The <code>ResourceTransfer</code> class is used to transfer an
 * array of <code>IResources</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 marshall the drag data from the source into a byte array.  If a drop 
 * occurs another <code>Transfer</code> is used to marshall 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>
 *
 * @see org.eclipse.jface.viewers.StructuredViewer
 * @see org.eclipse.swt.dnd.DropTarget
 * @see org.eclipse.swt.dnd.DragSource
 */
public class ResourceTransfer extends ByteArrayTransfer {

	/**
	 * 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;
}
/* (non-Javadoc)
 * Method declared on Transfer.
 */
protected int[] getTypeIds() {
	return new int[] {TYPEID};
}
/* (non-Javadoc)
 * Returns the type names.
 *
 * @return the list of type names
 */
protected String[] getTypeNames() {
	return new String[] {TYPE_NAME};
}
/* (non-Javadoc)
 * Method declared on Transfer.
 */
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 (int i = 0; i < resources.length; i++) {
			writeResource(dataOut, resources[i]);
		}

		//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
	}
}
/* (non-Javadoc)
 * Method declared on Transfer.
 */
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();
		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(new Path(path));
		case IResource.FILE :
			return workspace.getRoot().getFile(new Path(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());
}
}