/**
 * 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.
 *
 * Copyright 2012-2015 the original author or authors.
 */
package org.assertj.swing.monitor;

import static org.assertj.core.util.Sets.newHashSet;
import static org.assertj.swing.util.Maps.newWeakHashMap;

import java.awt.Component;
import java.awt.EventQueue;
import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import org.assertj.swing.annotation.RunsInCurrentThread;

/**
 * A mapping of AWT or Swing {@code Component}s, and their respective {@link EventQueue}.
 *
 * @author Yvonne Wang
 * @author Alex Ruiz
 */
class EventQueueMapping {
  final Map<Component, WeakReference<EventQueue>> queueMap = newWeakHashMap();

  @RunsInCurrentThread
  void addQueueFor(@Nonnull Component c) {
    EventQueue queue = c.getToolkit().getSystemEventQueue();
    queueMap.put(c, new WeakReference<EventQueue>(queue));
  }

  @RunsInCurrentThread
  @Nullable
  EventQueue queueFor(@Nonnull Component c) {
    EventQueue queue = storedQueueFor(c);
    if (queue == null) {
      return c.getToolkit().getSystemEventQueue();
    }
    return queue;
  }

  @Nullable
  EventQueue storedQueueFor(@Nonnull Component c) {
    return queueFrom(queueMap.get(c));
  }

  @Nonnull
  Collection<EventQueue> eventQueues() {
    Set<EventQueue> eventQueues = newHashSet();
    for (WeakReference<EventQueue> reference : queueMap.values()) {
      EventQueue queue = queueFrom(reference);
      if (queue != null) {
        eventQueues.add(queue);
      }
    }
    return eventQueues;
  }

  private @Nullable EventQueue queueFrom(@Nullable WeakReference<EventQueue> reference) {
    if (reference == null) {
      return null;
    }
    return reference.get();
  }
}