/**
 * 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.operation.core;

import org.waveprotocol.wave.model.operation.OperationException;
import org.waveprotocol.wave.model.wave.ParticipantId;
import org.waveprotocol.wave.model.wave.data.core.CoreWaveletData;

/**
 * Operation class for the add-participant operation.
 */
public final class CoreAddParticipant extends CoreWaveletOperation {
  /** Participant to add. */
  private final ParticipantId participant;

  /**
   * Creates an add-participant operation.
   *
   * @param participant  participant to add
   */
  public CoreAddParticipant(ParticipantId participant) {
    if (participant == null) {
      throw new NullPointerException("Null participant ID");
    }
    this.participant = participant;
  }

  /**
   * Gets the participant to add.
   *
   * @return the participant to add.
   */
  public ParticipantId getParticipantId() {
    return participant;
  }

  /**
   * Adds a participant from the given wavelet.
   */
  @Override
  public void doApply(CoreWaveletData target) throws OperationException {
    if (!target.addParticipant(participant)) {
      throw new OperationException("Attempt to add a duplicate participant.");
    }
  }

  @Override
  public CoreWaveletOperation getInverse() {
    return new CoreRemoveParticipant(participant);
  }

  @Override
  public String toString() {
    return "AddParticipant(" + participant + ")";
  }

  @Override
  public int hashCode() {
    return participant.hashCode();
  }

  @Override
  public boolean equals(Object obj) {
    if (!(obj instanceof CoreAddParticipant)) {
      return false;
    }
    CoreAddParticipant other = (CoreAddParticipant) obj;
    return participant.equals(other.participant);
  }
}