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/*
 * Copyright 2011 The GWT Project Authors
 *
 * 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.gwtproject.event.shared;

import org.gwtproject.event.shared.Event.Type;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

/**
 * Wraps an EventBus to hold on to any HandlerRegistrations, so that they can easily all be cleared
 * at once.
 */
public class ResettableEventBus
    extends EventBus {

  private final EventBus wrapped;

  private final Set registrations = new HashSet<>();

  public ResettableEventBus(EventBus wrappedBus) {
    this.wrapped = wrappedBus;
  }

  @Override
  public  HandlerRegistration addHandler(Type type,
                                            H handler) {
    HandlerRegistration rtn = wrapped.addHandler(type,
                                                 handler);
    return doRegisterHandler(rtn);
  }

  @Override
  public  HandlerRegistration addHandlerToSource(Type type,
                                                    Object source,
                                                    H handler) {
    HandlerRegistration rtn = wrapped.addHandlerToSource(type,
                                                         source,
                                                         handler);
    return doRegisterHandler(rtn);
  }

  @Override
  public void fireEvent(Event event) {
    wrapped.fireEvent(event);
  }

  @Override
  public void fireEventFromSource(Event event,
                                  Object source) {
    wrapped.fireEventFromSource(event,
                                source);
  }

  /**
   * Remove all handlers that have been added through this wrapper.
   */
  public void removeHandlers() {
    Iterator it = registrations.iterator();
    while (it.hasNext()) {
      HandlerRegistration r = it.next();

      /*
       * must remove before we call removeHandler. Might have come from nested
       * ResettableEventBus
       */
      it.remove();

      r.removeHandler();
    }
  }

  /**
   * Visible for testing.
   */
  int getRegistrationSize() {
    return registrations.size();
  }

  private HandlerRegistration doRegisterHandler(final HandlerRegistration registration) {
    registrations.add(registration);
    return () -> doUnregisterHandler(registration);
  }

  private void doUnregisterHandler(HandlerRegistration registration) {
    if (registrations.contains(registration)) {
      registration.removeHandler();
      registrations.remove(registration);
    }
  }

}