OpUtils.java example

Explorer
WaveInCloud-master
/**
 * Copyright 2009 Google Inc.
 *
 * Licensed 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.waveprotocol.wave.model.wave.undo;

import org.waveprotocol.wave.model.operation.wave.AddParticipant;
import org.waveprotocol.wave.model.operation.wave.NoOp;
import org.waveprotocol.wave.model.operation.wave.RemoveParticipant;
import org.waveprotocol.wave.model.operation.wave.VersionUpdateOp;
import org.waveprotocol.wave.model.operation.wave.WaveletBlipOperation;
import org.waveprotocol.wave.model.operation.wave.WaveletOperation;

/**
 * Utility methods.
 *
 */
final class OpUtils {
  private OpUtils() {
  }

  /**
   * Returns true iff the wavelet operation is considered a no-op as far as undo
   * is concerned.
   *
   * @param op
   */
  static boolean isNoop(WaveletOperation op) {
    if (op instanceof VersionUpdateOp || op instanceof NoOp) {
      return true;
    } else if (op instanceof AddParticipant || op instanceof RemoveParticipant
        || op instanceof WaveletBlipOperation) {
      return false;
    } else {
      // This happens when the op parameter is a non-core subclass of
      // WaveletOperation, not supported by wave.
      throw new RuntimeException("Unhandled op:" + op.getClass());
    }
  }
}