/*
    * 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.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.assertNull;
  import static org.junit.jupiter.api.Assertions.assertSame;
  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.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.apache.commons.lang3.AbstractLangTest;
  import org.apache.commons.lang3.ThreadUtils;
  import org.junit.jupiter.api.Test;
  
  class BackgroundInitializerTest extends AbstractLangTest {
      /**
       * A concrete implementation of BackgroundInitializer. It also overloads
       * some methods that simplify testing.
       */
      protected static class AbstractBackgroundInitializerTestImpl extends
              BackgroundInitializer<CloseableCounter> {
          /** An exception to be thrown by initialize(). */
          Exception ex;
  
          /** A flag whether the background task should sleep a while. */
          boolean shouldSleep;
  
          /** A latch tests can use to control when initialize completes. */
          final CountDownLatch latch = new CountDownLatch(1);
          boolean waitForLatch;
  
          /** An object containing the state we are testing */
          CloseableCounter counter = new CloseableCounter();
  
          AbstractBackgroundInitializerTestImpl() {
          }
  
          AbstractBackgroundInitializerTestImpl(final ExecutorService exec) {
              super(exec);
          }
  
          public void enableLatch() {
              waitForLatch = true;
          }
  
          public CloseableCounter getCloseableCounter() {
              return counter;
          }
  
          /**
           * Records this invocation. Optionally throws an exception or sleeps a
           * while.
           *
           * @throws Exception in case of an error
           */
          protected CloseableCounter initializeInternal() throws Exception {
              if (ex != null) {
                  throw ex;
              }
              if (shouldSleep) {
                  ThreadUtils.sleep(Duration.ofMinutes(1));
              }
              if (waitForLatch) {
                  latch.await();
              }
              return counter.increment();
          }
  
          public void releaseLatch() {
              latch.countDown();
          }
      }
  
      protected static class CloseableCounter {
         /** The number of invocations of initialize(). */
         AtomicInteger initializeCalls = new AtomicInteger();
 
         /** Has the close consumer successfully reached this object. */
         AtomicBoolean closed = new AtomicBoolean();
 
         public void close() {
             closed.set(true);
         }
 
         public int getInitializeCalls() {
             return initializeCalls.get();
         }
 
         public CloseableCounter increment() {
             initializeCalls.incrementAndGet();
             return this;
         }
 
         public boolean isClosed() {
             return closed.get();
         }
     }
 
     protected static class MethodBackgroundInitializerTestImpl extends AbstractBackgroundInitializerTestImpl {
 
         MethodBackgroundInitializerTestImpl() {
         }
 
         MethodBackgroundInitializerTestImpl(final ExecutorService exec) {
             super(exec);
         }
 
         @Override
         protected CloseableCounter initialize() throws Exception {
             return initializeInternal();
         }
     }
 
     /**
      * Helper method for checking whether the initialize() method was correctly
      * called. start() must already have been invoked.
      *
      * @param init the initializer to test
      */
     private void checkInitialize(final AbstractBackgroundInitializerTestImpl init) throws ConcurrentException {
         final Integer result = init.get().getInitializeCalls();
         assertEquals(1, result.intValue(), "Wrong result");
         assertEquals(1, init.getCloseableCounter().getInitializeCalls(), "Wrong number of invocations");
         assertNotNull(init.getFuture(), "No future");
     }
 
     protected AbstractBackgroundInitializerTestImpl getBackgroundInitializerTestImpl() {
         return new MethodBackgroundInitializerTestImpl();
     }
 
     protected AbstractBackgroundInitializerTestImpl getBackgroundInitializerTestImpl(final ExecutorService exec) {
         return new MethodBackgroundInitializerTestImpl(exec);
     }
 
     @Test
     void testBuilder() throws ConcurrentException {
         // @formatter:off
         final BackgroundInitializer<Object> backgroundInitializer = BackgroundInitializer.builder()
             .setCloser(null)
             .setExternalExecutor(null)
             .setInitializer(null)
             .get();
         // @formatter:on
         assertNull(backgroundInitializer.getExternalExecutor());
         assertFalse(backgroundInitializer.isInitialized());
         assertFalse(backgroundInitializer.isStarted());
         assertThrows(IllegalStateException.class, backgroundInitializer::getFuture);
     }
 
     @Test
     void testBuilderThenGetFailures() throws ConcurrentException {
         // @formatter:off
         final BackgroundInitializer<Object> backgroundInitializer = BackgroundInitializer.builder()
             .setCloser(null)
             .setExternalExecutor(null)
             .setInitializer(() -> {
                 throw new IllegalStateException("test");
             })
             .get();
         // @formatter:on
         assertNull(backgroundInitializer.getExternalExecutor());
         assertFalse(backgroundInitializer.isInitialized());
         assertFalse(backgroundInitializer.isStarted());
         assertThrows(IllegalStateException.class, backgroundInitializer::getFuture);
         // start
         backgroundInitializer.start();
         assertEquals("test", assertThrows(IllegalStateException.class, backgroundInitializer::get).getMessage());
     }
 
     /**
      * Tries to obtain the executor before start(). It should not have been
      * initialized yet.
      */
     @Test
     void testGetActiveExecutorBeforeStart() {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         assertNull(init.getActiveExecutor(), "Got an executor");
     }
 
     /**
      * Tests whether an external executor is correctly detected.
      */
     @Test
     void testGetActiveExecutorExternal() throws InterruptedException, ConcurrentException {
         final ExecutorService exec = Executors.newSingleThreadExecutor();
         try {
             final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl(exec);
             init.start();
             assertSame(exec, init.getActiveExecutor(), "Wrong executor");
             checkInitialize(init);
         } finally {
             exec.shutdown();
             exec.awaitTermination(1, TimeUnit.SECONDS);
         }
     }
 
     /**
      * Tests getActiveExecutor() for a temporary executor.
      */
     @Test
     void testGetActiveExecutorTemp() throws ConcurrentException {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         init.start();
         assertNotNull(init.getActiveExecutor(), "No active executor");
         checkInitialize(init);
     }
 
     /**
      * Tests calling get() before start(). This should cause an exception.
      */
     @Test
     void testGetBeforeStart() {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         assertThrows(IllegalStateException.class, init::get);
     }
 
     /**
      * Tests the get() method if background processing causes a checked
      * exception.
      */
     @Test
     void testGetCheckedException() {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         final Exception ex = new Exception();
         init.ex = ex;
         init.start();
         final ConcurrentException cex = assertThrows(ConcurrentException.class, init::get);
         assertEquals(ex, cex.getCause(), "Exception not thrown");
     }
 
     /**
      * Tests the get() method if waiting for the initialization is interrupted.
      *
      * @throws InterruptedException because we're making use of Java's concurrent API
      */
     @Test
     void testGetInterruptedException() throws InterruptedException {
         final ExecutorService exec = Executors.newSingleThreadExecutor();
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl(
                 exec);
         final CountDownLatch latch1 = new CountDownLatch(1);
         init.shouldSleep = true;
         init.start();
         final AtomicReference<InterruptedException> iex = new AtomicReference<>();
         final Thread getThread = new Thread() {
             @Override
             public void run() {
                 try {
                     init.get();
                 } catch (final ConcurrentException cex) {
                     if (cex.getCause() instanceof InterruptedException) {
                         iex.set((InterruptedException) cex.getCause());
                     }
                 } finally {
                     assertTrue(isInterrupted(), "Thread not interrupted");
                     latch1.countDown();
                 }
             }
         };
         getThread.start();
         getThread.interrupt();
         latch1.await();
         exec.shutdownNow();
         exec.awaitTermination(1, TimeUnit.SECONDS);
         assertNotNull(iex.get(), "No interrupted exception");
     }
 
     /**
      * Tests the get() method if background processing causes a runtime
      * exception.
      */
     @Test
     void testGetRuntimeException() {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         final RuntimeException rex = new RuntimeException();
         init.ex = rex;
         init.start();
         final Exception ex = assertThrows(Exception.class, init::get);
         assertEquals(rex, ex, "Runtime exception not thrown");
     }
 
     /**
      * Tests whether initialize() is invoked.
      */
     @Test
     void testInitialize() throws ConcurrentException {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         init.start();
         checkInitialize(init);
     }
 
     /**
      * Tests the execution of the background task if a temporary executor has to
      * be created.
      */
     @Test
     void testInitializeTempExecutor() throws ConcurrentException {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         assertTrue(init.start(), "Wrong result of start()");
         checkInitialize(init);
         assertTrue(init.getActiveExecutor().isShutdown(), "Executor not shutdown");
     }
 
     /**
      * Tests isInitialized() before and after the background task has finished.
      */
     @Test
     void testIsInitialized() throws ConcurrentException {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         init.enableLatch();
         init.start();
         assertTrue(init.isStarted(), "Not started"); //Started and Initialized should return opposite values
         assertFalse(init.isInitialized(), "Initialized before releasing latch");
         init.releaseLatch();
         init.get(); //to ensure the initialize thread has completed.
         assertTrue(init.isInitialized(), "Not initialized after releasing latch");
     }
 
     /**
      * Tests isStarted() after the background task has finished.
      */
     @Test
     void testIsStartedAfterGet() throws ConcurrentException {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         init.start();
         checkInitialize(init);
         assertTrue(init.isStarted(), "Not started");
     }
 
     /**
      * Tests isStarted() before start() was called.
      */
     @Test
     void testIsStartedFalse() {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         assertFalse(init.isStarted(), "Already started");
     }
 
     /**
      * Tests isStarted() after start().
      */
     @Test
     void testIsStartedTrue() {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         init.start();
         assertTrue(init.isStarted(), "Not started");
     }
 
     /**
      * Tests whether an external executor can be set using the
      * setExternalExecutor() method.
      */
     @Test
     void testSetExternalExecutor() throws ConcurrentException {
         final ExecutorService exec = Executors.newCachedThreadPool();
         try {
             final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
             init.setExternalExecutor(exec);
             assertEquals(exec, init.getExternalExecutor(), "Wrong executor service");
             assertTrue(init.start(), "Wrong result of start()");
             assertSame(exec, init.getActiveExecutor(), "Wrong active executor");
             checkInitialize(init);
             assertFalse(exec.isShutdown(), "Executor was shutdown");
         } finally {
             exec.shutdown();
         }
     }
 
     /**
      * Tests that setting an executor after start() causes an exception.
      *
      * @throws org.apache.commons.lang3.concurrent.ConcurrentException because the test implementation may throw it
      */
     @Test
     void testSetExternalExecutorAfterStart() throws ConcurrentException, InterruptedException {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         init.start();
         final ExecutorService exec = Executors.newSingleThreadExecutor();
         try {
             assertThrows(IllegalStateException.class, () -> init.setExternalExecutor(exec));
             init.get();
         } finally {
             exec.shutdown();
             exec.awaitTermination(1, TimeUnit.SECONDS);
         }
     }
 
     /**
      * Tests invoking start() multiple times. Only the first invocation should
      * have an effect.
      */
     @Test
     void testStartMultipleTimes() throws ConcurrentException {
         final AbstractBackgroundInitializerTestImpl init = getBackgroundInitializerTestImpl();
         assertTrue(init.start(), "Wrong result for start()");
         for (int i = 0; i < 10; i++) {
             assertFalse(init.start(), "Could start again");
         }
         checkInitialize(init);
     }
 }