/*
    * 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
    *
    *      https://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.commons.lang3.concurrent;
  
  import static org.apache.commons.lang3.LangAssertions.assertIllegalArgumentException;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNotNull;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.time.Duration;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.ScheduledFuture;
  import java.util.concurrent.ScheduledThreadPoolExecutor;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.commons.lang3.AbstractLangTest;
  import org.apache.commons.lang3.ThreadUtils;
  import org.easymock.EasyMock;
  import org.junit.jupiter.api.Test;
  
  /**
   * Tests {@link TimedSemaphore}.
   */
  class TimedSemaphoreTest extends AbstractLangTest {
  
      /**
       * A test thread class that will be used by tests for triggering the
       * semaphore. The thread calls the semaphore a configurable number of times.
       * When this is done, it cannotify the main thread.
       */
      private static final class SemaphoreThread extends Thread {
  
          /** The semaphore. */
          private final TimedSemaphore semaphore;
  
          /** A latch for communication with the main thread. */
          private final CountDownLatch latch;
  
          /** The number of acquire() calls. */
          private final int count;
  
          /** The number of invocations of the latch. */
          private final int latchCount;
  
          SemaphoreThread(final TimedSemaphore b, final CountDownLatch l, final int c, final int lc) {
              semaphore = b;
              latch = l;
              count = c;
              latchCount = lc;
          }
  
          /**
           * Calls acquire() on the semaphore for the specified number of times.
           * Optionally the latch will also be triggered to synchronize with the
           * main test thread.
           */
          @Override
          public void run() {
              try {
                  for (int i = 0; i < count; i++) {
                      semaphore.acquire();
  
                      if (i < latchCount) {
                          latch.countDown();
                      }
                  }
              } catch (final InterruptedException iex) {
                  Thread.currentThread().interrupt();
              }
          }
      }
  
      /**
       * A specialized implementation of {@code TimedSemaphore} that is easier to
       * test.
       */
      private static final class TimedSemaphoreTestImpl extends TimedSemaphore {
  
          /** A mock scheduled future. */
          ScheduledFuture<?> schedFuture;
  
          /** A latch for synchronizing with the main thread. */
         volatile CountDownLatch latch;
 
         /** Counter for the endOfPeriod() invocations. */
         private int periodEnds;
 
         TimedSemaphoreTestImpl(final long timePeriod, final TimeUnit timeUnit, final int limit) {
             super(timePeriod, timeUnit, limit);
         }
 
         TimedSemaphoreTestImpl(final ScheduledExecutorService service, final long timePeriod, final TimeUnit timeUnit, final int limit) {
             super(service, timePeriod, timeUnit, limit);
         }
 
         /**
          * Invokes the latch if one is set.
          *
          * @throws InterruptedException because it is declared that way in TimedSemaphore
          */
         @Override
         public synchronized void acquire() throws InterruptedException {
             super.acquire();
             if (latch != null) {
                 latch.countDown();
             }
         }
 
         /**
          * Counts the number of invocations.
          */
         @Override
         protected synchronized void endOfPeriod() {
             super.endOfPeriod();
             periodEnds++;
         }
 
         /**
          * Returns the number of invocations of the endOfPeriod() method.
          *
          * @return the endOfPeriod() invocations
          */
         int getPeriodEnds() {
             synchronized (this) {
                 return periodEnds;
             }
         }
 
         /**
          * Either returns the mock future or calls the super method.
          */
         @Override
         protected ScheduledFuture<?> startTimer() {
             return schedFuture != null ? schedFuture : super.startTimer();
         }
     }
 
     /**
      * A test thread class which invokes {@code tryAcquire()} on the test semaphore and
      * records the return value.
      */
     private static final class TryAcquireThread extends Thread {
 
         /** The semaphore. */
         private final TimedSemaphore semaphore;
 
         /** A latch for communication with the main thread. */
         private final CountDownLatch latch;
 
         /** Flag whether a permit could be acquired. */
         private boolean acquired;
 
         TryAcquireThread(final TimedSemaphore s, final CountDownLatch l) {
             semaphore = s;
             latch = l;
         }
 
         @Override
         public void run() {
             try {
                 if (latch.await(10, TimeUnit.SECONDS)) {
                     acquired = semaphore.tryAcquire();
                 }
             } catch (final InterruptedException iex) {
                 // ignore
             }
         }
     }
 
     /** Constant for the time period. */
     private static final long PERIOD_MILLIS = 500;
 
     private static final Duration DURATION = Duration.ofMillis(PERIOD_MILLIS);
 
     /** Constant for the time unit. */
     private static final TimeUnit UNIT = TimeUnit.MILLISECONDS;
 
     /** Constant for the default limit. */
     private static final int LIMIT = 10;
 
     /**
      * Prepares an executor service mock to expect the start of the timer.
      *
      * @param service the mock
      * @param future the future
      */
     private void prepareStartTimer(final ScheduledExecutorService service,
             final ScheduledFuture<?> future) {
         service.scheduleAtFixedRate((Runnable) EasyMock.anyObject(), EasyMock.eq(PERIOD_MILLIS), EasyMock.eq(PERIOD_MILLIS), EasyMock.eq(UNIT));
         EasyMock.expectLastCall().andReturn(future);
     }
 
     /**
      * Tests the acquire() method if a limit is set.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testAcquireLimit() throws InterruptedException {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         final ScheduledFuture<?> future = EasyMock.createMock(ScheduledFuture.class);
         prepareStartTimer(service, future);
         EasyMock.replay(service, future);
         final int count = 10;
         final CountDownLatch latch = new CountDownLatch(count - 1);
         final TimedSemaphore semaphore = new TimedSemaphore(service, PERIOD_MILLIS, UNIT, 1);
         final SemaphoreThread t = new SemaphoreThread(semaphore, latch, count, count - 1);
         semaphore.setLimit(count - 1);
         // start a thread that calls the semaphore count times
         t.start();
         latch.await();
         // now the semaphore's limit should be reached and the thread blocked
         assertEquals(count - 1, semaphore.getAcquireCount(), "Wrong semaphore count");
         // this wakes up the thread, it should call the semaphore once more
         semaphore.endOfPeriod();
         t.join();
         assertEquals(1, semaphore.getAcquireCount(), "Wrong semaphore count (2)");
         assertEquals(count - 1, semaphore.getLastAcquiresPerPeriod(), "Wrong acquire() count");
         EasyMock.verify(service, future);
     }
 
     /**
      * Tests a bigger number of invocations that span multiple periods. The
      * period is set to a very short time. A background thread calls the
      * semaphore a large number of times. While it runs at last one end of a
      * period should be reached.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testAcquireMultiplePeriods() throws InterruptedException {
         final int count = 1000;
         final TimedSemaphoreTestImpl semaphore = new TimedSemaphoreTestImpl(PERIOD_MILLIS / 10, TimeUnit.MILLISECONDS, 1);
         semaphore.setLimit(count / 4);
         final CountDownLatch latch = new CountDownLatch(count);
         final SemaphoreThread t = new SemaphoreThread(semaphore, latch, count, count);
         t.start();
         latch.await();
         semaphore.shutdown();
         assertTrue(semaphore.getPeriodEnds() > 0, "End of period not reached");
     }
 
     /**
      * Tests the acquire() method if more threads are involved than the limit.
      * This method starts a number of threads that all invoke the semaphore. The
      * semaphore's limit is set to 1, so in each period only a single thread can
      * acquire the semaphore.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testAcquireMultipleThreads() throws InterruptedException {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         final ScheduledFuture<?> future = EasyMock.createMock(ScheduledFuture.class);
         prepareStartTimer(service, future);
         EasyMock.replay(service, future);
         final TimedSemaphoreTestImpl semaphore = new TimedSemaphoreTestImpl(service, PERIOD_MILLIS, UNIT, 1);
         semaphore.latch = new CountDownLatch(1);
         final int count = 10;
         final SemaphoreThread[] threads = new SemaphoreThread[count];
         for (int i = 0; i < count; i++) {
             threads[i] = new SemaphoreThread(semaphore, null, 1, 0);
             threads[i].start();
         }
         for (int i = 0; i < count; i++) {
             semaphore.latch.await();
             assertEquals(1, semaphore.getAcquireCount(), "Wrong count");
             semaphore.latch = new CountDownLatch(1);
             semaphore.endOfPeriod();
             assertEquals(1, semaphore.getLastAcquiresPerPeriod(), "Wrong acquire count");
         }
         for (int i = 0; i < count; i++) {
             threads[i].join();
         }
         EasyMock.verify(service, future);
     }
 
     /**
      * Tests the acquire() method if no limit is set. A test thread is started
      * that calls the semaphore a large number of times. Even if the semaphore's
      * period does not end, the thread should never block.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testAcquireNoLimit() throws InterruptedException {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         final ScheduledFuture<?> future = EasyMock.createMock(ScheduledFuture.class);
         prepareStartTimer(service, future);
         EasyMock.replay(service, future);
         final TimedSemaphoreTestImpl semaphore = new TimedSemaphoreTestImpl(service, PERIOD_MILLIS, UNIT, TimedSemaphore.NO_LIMIT);
         final int count = 1000;
         final CountDownLatch latch = new CountDownLatch(count);
         final SemaphoreThread t = new SemaphoreThread(semaphore, latch, count, count);
         t.start();
         latch.await();
         EasyMock.verify(service, future);
     }
 
     /**
      * Tests whether the available non-blocking calls can be queried.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testGetAvailablePermits() throws InterruptedException {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         final ScheduledFuture<?> future = EasyMock.createMock(ScheduledFuture.class);
         prepareStartTimer(service, future);
         EasyMock.replay(service, future);
         final TimedSemaphore semaphore = new TimedSemaphore(service, PERIOD_MILLIS, UNIT, LIMIT);
         for (int i = 0; i < LIMIT; i++) {
             assertEquals(LIMIT - i, semaphore.getAvailablePermits(), "Wrong available count at " + i);
             semaphore.acquire();
         }
         semaphore.endOfPeriod();
         assertEquals(LIMIT, semaphore.getAvailablePermits(), "Wrong available count in new period");
         EasyMock.verify(service, future);
     }
 
     /**
      * Tests the methods for statistics.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testGetAverageCallsPerPeriod() throws InterruptedException {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         final ScheduledFuture<?> future = EasyMock.createMock(ScheduledFuture.class);
         prepareStartTimer(service, future);
         EasyMock.replay(service, future);
         final TimedSemaphore semaphore = new TimedSemaphore(service, PERIOD_MILLIS, UNIT, LIMIT);
         semaphore.acquire();
         semaphore.endOfPeriod();
         assertEquals(1.0, semaphore.getAverageCallsPerPeriod(), .005, "Wrong average (1)");
         semaphore.acquire();
         semaphore.acquire();
         semaphore.endOfPeriod();
         assertEquals(1.5, semaphore.getAverageCallsPerPeriod(), .005, "Wrong average (2)");
         EasyMock.verify(service, future);
     }
 
     /**
      * Tests creating a new instance.
      */
     @Test
     void testInit() {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         EasyMock.replay(service);
         final TimedSemaphore semaphore = new TimedSemaphore(service, PERIOD_MILLIS, UNIT, LIMIT);
         EasyMock.verify(service);
         assertEquals(service, semaphore.getExecutorService(), "Wrong service");
         assertEquals(PERIOD_MILLIS, semaphore.getPeriod(), "Wrong period");
         assertEquals(UNIT, semaphore.getUnit(), "Wrong unit");
         assertEquals(0, semaphore.getLastAcquiresPerPeriod(), "Statistic available");
         assertEquals(0.0, semaphore.getAverageCallsPerPeriod(), .05, "Average available");
         assertFalse(semaphore.isShutdown(), "Already shutdown");
         assertEquals(LIMIT, semaphore.getLimit(), "Wrong limit");
     }
 
     /**
      * Tests whether a default executor service is created if no service is
      * provided.
      */
     @Test
     void testInitDefaultService() {
         final TimedSemaphore semaphore = new TimedSemaphore(PERIOD_MILLIS, UNIT, LIMIT);
         final ScheduledThreadPoolExecutor exec = (ScheduledThreadPoolExecutor) semaphore.getExecutorService();
         assertFalse(exec.getContinueExistingPeriodicTasksAfterShutdownPolicy(), "Wrong periodic task policy");
         assertFalse(exec.getExecuteExistingDelayedTasksAfterShutdownPolicy(), "Wrong delayed task policy");
         assertFalse(exec.isShutdown(), "Already shutdown");
         semaphore.shutdown();
     }
 
     /**
      * Tries to create an instance with a negative period. This should cause an
      * exception.
      */
     @Test
     void testInitInvalidPeriod() {
         assertIllegalArgumentException(() -> new TimedSemaphore(0L, UNIT, LIMIT));
     }
 
     /**
      * Tries to call acquire() after shutdown(). This should cause an exception.
      */
     @Test
     void testPassAfterShutdown() {
         final TimedSemaphore semaphore = new TimedSemaphore(PERIOD_MILLIS, UNIT, LIMIT);
         semaphore.shutdown();
         assertThrows(IllegalStateException.class, semaphore::acquire);
     }
 
     /**
      * Tests multiple invocations of the shutdown() method.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testShutdownMultipleTimes() throws InterruptedException {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         final ScheduledFuture<?> future = EasyMock.createMock(ScheduledFuture.class);
         prepareStartTimer(service, future);
         EasyMock.expect(Boolean.valueOf(future.cancel(false))).andReturn(Boolean.TRUE);
         EasyMock.replay(service, future);
         final TimedSemaphoreTestImpl semaphore = new TimedSemaphoreTestImpl(service, PERIOD_MILLIS, UNIT, LIMIT);
         semaphore.acquire();
         for (int i = 0; i < 10; i++) {
             semaphore.shutdown();
         }
         EasyMock.verify(service, future);
     }
 
     /**
      * Tests the shutdown() method if the executor belongs to the semaphore. In
      * this case it has to be shut down.
      */
     @Test
     void testShutdownOwnExecutor() {
         final TimedSemaphore semaphore = new TimedSemaphore(PERIOD_MILLIS, UNIT, LIMIT);
         semaphore.shutdown();
         assertTrue(semaphore.isShutdown(), "Not shutdown");
         assertTrue(semaphore.getExecutorService().isShutdown(), "Executor not shutdown");
     }
 
     /**
      * Tests the shutdown() method for a shared executor service before a task
      * was started. This should do pretty much nothing.
      */
     @Test
     void testShutdownSharedExecutorNoTask() {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         EasyMock.replay(service);
         final TimedSemaphore semaphore = new TimedSemaphore(service, PERIOD_MILLIS, UNIT, LIMIT);
         semaphore.shutdown();
         assertTrue(semaphore.isShutdown(), "Not shutdown");
         EasyMock.verify(service);
     }
 
     /**
      * Tests the shutdown() method for a shared executor after the task was
      * started. In this case the task must be canceled.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testShutdownSharedExecutorTask() throws InterruptedException {
         final ScheduledExecutorService service = EasyMock.createMock(ScheduledExecutorService.class);
         final ScheduledFuture<?> future = EasyMock.createMock(ScheduledFuture.class);
         prepareStartTimer(service, future);
         EasyMock.expect(Boolean.valueOf(future.cancel(false))).andReturn(Boolean.TRUE);
         EasyMock.replay(service, future);
         final TimedSemaphoreTestImpl semaphore = new TimedSemaphoreTestImpl(service, PERIOD_MILLIS, UNIT, LIMIT);
         semaphore.acquire();
         semaphore.shutdown();
         assertTrue(semaphore.isShutdown(), "Not shutdown");
         EasyMock.verify(service, future);
     }
 
     /**
      * Tests starting the timer.
      *
      * @throws InterruptedException so we don't have to catch it
      */
     @Test
     void testStartTimer() throws InterruptedException {
         final TimedSemaphoreTestImpl semaphore = new TimedSemaphoreTestImpl(PERIOD_MILLIS, UNIT, LIMIT);
         final ScheduledFuture<?> future = semaphore.startTimer();
         assertNotNull(future, "No future returned");
         ThreadUtils.sleepQuietly(DURATION);
         final int trials = 10;
         int count = 0;
         do {
             Thread.sleep(PERIOD_MILLIS);
             assertFalse(count++ > trials, "endOfPeriod() not called!");
         } while (semaphore.getPeriodEnds() <= 0);
         semaphore.shutdown();
     }
 
     /**
      * Tests the tryAcquire() method. It is checked whether the semaphore can be acquired
      * by a bunch of threads the expected number of times and not more.
      */
     @Test
     void testTryAcquire() throws InterruptedException {
         final TimedSemaphore semaphore = new TimedSemaphore(PERIOD_MILLIS, TimeUnit.SECONDS, LIMIT);
         final TryAcquireThread[] threads = new TryAcquireThread[3 * LIMIT];
         final CountDownLatch latch = new CountDownLatch(1);
         for (int i = 0; i < threads.length; i++) {
             threads[i] = new TryAcquireThread(semaphore, latch);
             threads[i].start();
         }
         latch.countDown();
         int permits = 0;
         for (final TryAcquireThread t : threads) {
             t.join();
             if (t.acquired) {
                 permits++;
             }
         }
         assertEquals(LIMIT, permits, "Wrong number of permits granted");
     }
 
     /**
      * Tries to call tryAcquire() after shutdown(). This should cause an exception.
      */
     @Test
     void testTryAcquireAfterShutdown() {
         final TimedSemaphore semaphore = new TimedSemaphore(PERIOD_MILLIS, UNIT, LIMIT);
         semaphore.shutdown();
         assertThrows(IllegalStateException.class, semaphore::tryAcquire);
     }
 }