/**
 * 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.core;

import java.awt.Component;
import java.awt.Container;
import java.awt.Window;

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

import org.assertj.swing.annotation.RunsInCurrentThread;

/**
 * Finds the focus owner of an AWT or Swing {@code Container}.
 * 
 * @author Alex Ruiz
 */
class ContainerFocusOwnerFinder {
  @RunsInCurrentThread
  @Nullable
  Component focusOwnerOf(@Nullable Container c) {
    if (!(c instanceof Window)) {
      return null;
    }
    return focusOwnerOf((Window) c);
  }

  @RunsInCurrentThread
  private @Nullable Component focusOwnerOf(@Nonnull Window w) {
    if (!w.isShowing()) {
      return null;
    }
    Component focus = w.getFocusOwner();
    if (focus != null) {
      return focus;
    }
    for (Window o : w.getOwnedWindows()) {
      focus = o.getFocusOwner();
      if (focus != null) {
        return focus;
      }
    }
    return null;
  }
}