/*
    * Copyright (C) 2011 The Guava 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 com.google.common.util.concurrent;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  import static java.util.concurrent.TimeUnit.MILLISECONDS;
  import static java.util.concurrent.TimeUnit.NANOSECONDS;
  import static junit.framework.Assert.fail;
  
  import com.google.common.testing.TearDown;
  import com.google.common.testing.TearDownAccepter;
  
  import java.util.concurrent.TimeUnit;
  import java.util.logging.Logger;
  
  /**
   * Utilities for performing thread interruption in tests
   * 
   * @author Kevin Bourrillion
   * @author Chris Povirk
   */
  final class InterruptionUtil {
    private static final Logger logger =
        Logger.getLogger(InterruptionUtil.class.getName());
  
    /**
     * Runnable which will interrupt the target thread repeatedly when run.
     */
    private static final class Interruptenator implements Runnable {
      private final long everyMillis;
      private final Thread interruptee;
      private volatile boolean shouldStop = false;
  
      Interruptenator(Thread interruptee, long everyMillis) {
        this.everyMillis = everyMillis;
        this.interruptee = interruptee;
      }
  
      @Override
      public void run() {
        while (true) {
          try {
            Thread.sleep(everyMillis);
          } catch (InterruptedException e) {
            // ok. just stop sleeping.
          }
          if (shouldStop) {
            break;
          }
          interruptee.interrupt();
        }
      }
  
      void stopInterrupting() {
        shouldStop = true;
      }
    }
  
    /**
     * Interrupts the current thread after sleeping for the specified delay.
     */
    static void requestInterruptIn(final long time, final TimeUnit unit) {
      checkNotNull(unit);
      final Thread interruptee = Thread.currentThread();
      new Thread(new Runnable() {
        @Override
        public void run() {
          try {
            unit.sleep(time);
          } catch (InterruptedException wontHappen) {
            throw new AssertionError(wontHappen);
          }
          interruptee.interrupt();
        }
      }).start();
    }
  
    static void repeatedlyInterruptTestThread(
        long interruptPeriodMillis, TearDownAccepter tearDownAccepter) {
      final Interruptenator interruptingTask =
          new Interruptenator(Thread.currentThread(), interruptPeriodMillis);
      final Thread interruptingThread = new Thread(interruptingTask);
      interruptingThread.start();
      tearDownAccepter.addTearDown(new TearDown() {
        @Override public void tearDown() throws Exception {
         interruptingTask.stopInterrupting();
         interruptingThread.interrupt();
         joinUninterruptibly(interruptingThread, 2500, MILLISECONDS);
         Thread.interrupted();
         if (interruptingThread.isAlive()) {
           // This will be hidden by test-output redirection:
           logger.severe(
               "InterruptenatorTask did not exit; future tests may be affected");
           /*
            * This won't do any good under JUnit 3, but I'll leave it around in
            * case we ever switch to JUnit 4:
            */
           fail();
         }
       }
     });
   }
 
   // TODO(cpovirk): promote to Uninterruptibles, and add untimed version
   private static void joinUninterruptibly(
       Thread thread, long timeout, TimeUnit unit) {
     boolean interrupted = false;
     try {
       long remainingNanos = unit.toNanos(timeout);
       long end = System.nanoTime() + remainingNanos;
 
       while (true) {
         try {
           // TimeUnit.timedJoin() treats negative timeouts just like zero.
           NANOSECONDS.timedJoin(thread, remainingNanos);
           return;
         } catch (InterruptedException e) {
           interrupted = true;
           remainingNanos = end - System.nanoTime();
         }
       }
     } finally {
       if (interrupted) {
         Thread.currentThread().interrupt();
       }
     }
   }
 }