/**
 * 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.box.server.robots;

import com.google.common.collect.Maps;
import com.google.wave.api.InvalidRequestException;
import com.google.wave.api.OperationType;

import org.waveprotocol.box.server.robots.operations.OperationService;
import org.waveprotocol.wave.util.logging.Log;

import java.util.Map;

/**
 * Abstract class for registering and accessing {@link OperationService} to
 * execute operations for use in the Robot APIs. Note that this class is not
 * thread safe.
 *
 * Implementations of this class are expected to define the way and moment when
 * operations are registered.
 *
 * @author ljvderijk@google.com (Lennard de Rijk)
 */
public abstract class AbstractOperationServiceRegistry implements OperationServiceRegistry {

  private static Log LOG = Log.get(AbstractOperationServiceRegistry.class);

  private Map<OperationType, OperationService> operationMap = Maps.newHashMap();

  public AbstractOperationServiceRegistry() {
  }

  @Override
  public final OperationService getServiceFor(OperationType opType) throws InvalidRequestException {
    OperationService service = operationMap.get(opType);
    if (service == null) {
      throw new InvalidRequestException("No OperationService found for " + opType);
    }
    return service;
  }

  /**
   * Registers the {@link OperationService} for the given {@link OperationType}.
   *
   * @param operation the type of the operation to register for
   * @param service the {@link OperationService} to be registered
   */
  protected final void register(OperationType operation, OperationService service) {
    // Do a put first so we can make it use a concurrent map if needed.
    OperationService oldValue = operationMap.put(operation, service);
    if (oldValue != null) {
      LOG.warning("The OperationService for " + operation.name() + " was overwritten");
    }
  }
}