/**
 * Copyright 2010 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.client.editor;

import org.waveprotocol.wave.model.util.Preconditions;

import java.util.Stack;

/**
 * Simple implementation of {@link Responsibility.Manager}. The default
 * responsibility is indirect.
 *
 */
public class ResponsibilityManagerImpl implements Responsibility.Manager {

  private static enum SequenceType {
    DIRECT,
    INDIRECT;
  }

  /**
   * Keeps track of whether the op sequence should be routed as undoable, or
   * non-undoable. The top of the stack determines how ops get routed.
   */
  private final Stack<SequenceType> sequenceType = new Stack<SequenceType>();

  private SequenceType currentSequenceType() {
    // Indirect by default, as per javadoc (keep doc and code in sync)
    return sequenceType.isEmpty() ? SequenceType.INDIRECT : sequenceType.peek();
  }

  @Override
  public void startDirectSequence() {
    sequenceType.push(SequenceType.DIRECT);
  }

  @Override
  public void endDirectSequence() {
    Preconditions.checkState(!sequenceType.isEmpty()
        && sequenceType.peek() == SequenceType.DIRECT, "end undoable sequence without begin");
    sequenceType.pop();
  }

  @Override
  public void startIndirectSequence() {
    EditorStaticDeps.logger.trace().log("Depth: ", sequenceType.size());
    sequenceType.push(SequenceType.INDIRECT);
  }

  @Override
  public void endIndirectSequence() {
    Preconditions.checkState(!sequenceType.isEmpty()
        && sequenceType.peek() == SequenceType.INDIRECT,
        "end non-undoable sequence without begin");
    sequenceType.pop();
  }

  @Override
  public boolean withinDirectSequence() {
    return currentSequenceType() == SequenceType.DIRECT;
  }
}