/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.jdo.tck.util;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * This class extends java.lang.ThreadGroup and stores any uncaught exception of threads from this
 * ThreadGroup for later retrieval.
 *
 * @author Michael Bouschen
 */
public class ThreadExceptionHandler extends ThreadGroup {
  /**
   * Map of uncaught exceptions. The thread is the key and the uncaught Throwable is the value in
   * the map.
   */
  private final Map<Thread, Throwable> uncaughtExceptions = new HashMap<>();

  /** Constructor. */
  public ThreadExceptionHandler() {
    super("ThreadExceptionHandler");
  }

  /**
   * Called by the Java Virtual Machine when a thread in this thread group stops because of an
   * uncaught exception. This implementation stores the uncaught exception in a map for later
   * retrieval.
   */
  @Override
  public void uncaughtException(Thread t, Throwable e) {
    uncaughtExceptions.put(t, e);
  }

  /**
   * Returns an uncaught exception for the specified thread.
   *
   * @param t the thread
   * @return uncaught exception for the specified thread
   */
  public Throwable getUncaughtException(Thread t) {
    return uncaughtExceptions.get(t);
  }

  /**
   * Returns all uncaught exceptions stored in this ThreadGroup. Each element in the returned set is
   * a Map.Entry with the thread as the key and the uncaught Throwable is the value.
   *
   * @return Set of uncaught exceptions
   */
  public Set<Map.Entry<Thread, Throwable>> getAllUncaughtExceptions() {
    return uncaughtExceptions.entrySet();
  }

  /** Clears all exceptions in this ThreadGroup. */
  public void clear() {
    uncaughtExceptions.clear();
  }
}