/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.uima.caseditor.editor.util;

import java.util.Arrays;

import org.eclipse.swt.dnd.ByteArrayTransfer;
import org.eclipse.swt.dnd.TransferData;

/**
 * This class is able to transfer an {@link Object} object. The object gets saved and only an Id is
 * transfered.
 */
public abstract class ObjectTransfer extends ByteArrayTransfer {

  /** The m id generator. */
  private IDGenerator mIdGenerator = IDGenerator.getInstance();

  /** The m transfer name. */
  private String mTransferName;

  /** The m transfer ID. */
  private int mTransferID;

  /** The m current ID. */
  private byte[] mCurrentID;

  /** The m object. */
  private Object mObject;

  /**
   * Initializes a new instance with a name.
   *
   * @param name
   *          - the name of current instance.
   */
  protected ObjectTransfer(String name) {
    mTransferName = name;
    mTransferID = registerType(mTransferName);
  }

  @Override
  protected void javaToNative(Object object, TransferData transferData) {
    mCurrentID = mIdGenerator.nextUniqueID();
    mObject = object;

    if (transferData != null) {
      super.javaToNative(mCurrentID, transferData);
    }
  }

  @Override
  protected Object nativeToJava(TransferData transferData) {
    byte bytes[] = (byte[]) super.nativeToJava(transferData);
    return Arrays.equals(mCurrentID, bytes) ? mObject : null;
  }

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

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