/*
    * 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.assertArrayEquals;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNotEquals;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.beans.PropertyChangeEvent;
  import java.beans.PropertyChangeListener;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.commons.lang3.AbstractLangTest;
  import org.apache.commons.lang3.ArrayUtils;
  import org.junit.jupiter.api.Test;
  
  /**
   * Test class for {@code EventCountCircuitBreaker}.
   */
  class EventCountCircuitBreakerTest extends AbstractLangTest {
  
      /**
       * A test change listener for checking whether correct change events are generated.
       */
      private static final class ChangeListener implements PropertyChangeListener {
  
          /** The expected event source. */
          private final Object expectedSource;
  
          /** A list with the updated values extracted from received change events. */
          private final List<Boolean> changedValues;
  
          /**
           * Creates a new instance of {@code ChangeListener} and sets the expected event
           * source.
           *
           * @param source the expected event source
           */
          ChangeListener(final Object source) {
              expectedSource = source;
              changedValues = new ArrayList<>();
          }
  
          @Override
          public void propertyChange(final PropertyChangeEvent evt) {
              assertEquals(expectedSource, evt.getSource(), "Wrong event source");
              assertEquals("open", evt.getPropertyName(), "Wrong property name");
              final Boolean newValue = (Boolean) evt.getNewValue();
              final Boolean oldValue = (Boolean) evt.getOldValue();
              assertNotEquals(newValue, oldValue, "Old and new value are equal");
              changedValues.add(newValue);
          }
  
          /**
           * Verifies that change events for the expected values have been received.
           *
           * @param values the expected values
           */
          public void verify(final Boolean... values) {
              assertArrayEquals(values, changedValues.toArray(ArrayUtils.EMPTY_BOOLEAN_OBJECT_ARRAY));
          }
      }
  
      /**
       * A test implementation of {@code EventCountCircuitBreaker} which supports mocking the timer.
       * This is useful for the creation of deterministic tests for switching the circuit
       * breaker's state.
       */
      private static final class EventCountCircuitBreakerTestImpl extends EventCountCircuitBreaker {
  
          /** The current time in nanoseconds. */
          private long currentTime;
  
          EventCountCircuitBreakerTestImpl(final int openingThreshold, final long openingInterval,
                                                  final TimeUnit openingUnit, final int closingThreshold, final long closingInterval,
                                                  final TimeUnit closingUnit) {
              super(openingThreshold, openingInterval, openingUnit, closingThreshold,
                      closingInterval, closingUnit);
          }
  
         /**
          * Sets the current time to be used by this test object for the next operation.
          *
          * @param time the time to set
          * @return a reference to this object
          */
         public EventCountCircuitBreakerTestImpl at(final long time) {
             currentTime = time;
             return this;
         }
 
         /**
          * {@inheritDoc} This implementation returns the value passed to the {@code at()}
          * method.
          */
         @Override
         long nanoTime() {
             return currentTime;
         }
     }
 
     /** Constant for the opening threshold. */
     private static final int OPENING_THRESHOLD = 10;
 
     /** Constant for the closing threshold. */
     private static final int CLOSING_THRESHOLD = 5;
 
     /** Constant for the factor for converting nanoseconds. */
     private static final long NANO_FACTOR = 1000L * 1000L * 1000L;
 
     /**
      * Tests whether a new check interval is started if the circuit breaker has a
      * transition to open state.
      */
     @Test
     void testAutomaticOpenStartsNewCheckInterval() {
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 2,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         long time = 10 * NANO_FACTOR;
         for (int i = 0; i <= OPENING_THRESHOLD; i++) {
             breaker.at(time++).incrementAndCheckState();
         }
         assertTrue(breaker.isOpen(), "Not open");
         time += NANO_FACTOR - 1000;
         assertFalse(breaker.at(time).incrementAndCheckState(), "Already closed");
         time += 1001;
         assertTrue(breaker.at(time).checkState(), "Not closed in time interval");
     }
 
     /**
      * Tests whether events are generated when the state is changed.
      */
     @Test
     void testChangeEvents() {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS);
         final ChangeListener listener = new ChangeListener(breaker);
         breaker.addChangeListener(listener);
         breaker.open();
         breaker.close();
         listener.verify(Boolean.TRUE, Boolean.FALSE);
     }
 
     /**
      * Tests that automatic state transitions generate change events as well.
      */
     @Test
     void testChangeEventsGeneratedByAutomaticTransitions() {
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 2,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         final ChangeListener listener = new ChangeListener(breaker);
         breaker.addChangeListener(listener);
         long time = 0;
         for (int i = 0; i <= OPENING_THRESHOLD; i++, time += 1000) {
             breaker.at(time).incrementAndCheckState();
         }
         breaker.at(NANO_FACTOR + 1).checkState();
         breaker.at(3 * NANO_FACTOR).checkState();
         listener.verify(Boolean.TRUE, Boolean.FALSE);
     }
 
     /**
      * Tests whether the circuit breaker can be closed explicitly.
      */
     @Test
     void testClose() {
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 2,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         long time = 0;
         for (int i = 0; i <= OPENING_THRESHOLD; i++, time += 1000) {
             breaker.at(time).incrementAndCheckState();
         }
         assertTrue(breaker.isOpen(), "Not open");
         breaker.close();
         assertTrue(breaker.isClosed(), "Not closed");
         assertTrue(breaker.at(time + 1000).incrementAndCheckState(), "Open again");
     }
 
     /**
      * Tests that the circuit breaker closes automatically if the number of events
      * received goes under the closing threshold.
      */
     @Test
     void testClosingWhenThresholdReached() {
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD,
                 10, TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         breaker.open();
         breaker.at(1000).incrementAndCheckState();
         assertFalse(breaker.at(2000).checkState(), "Already closed");
         assertFalse(breaker.at(NANO_FACTOR).checkState(), "Closed at interval end");
         assertTrue(breaker.at(NANO_FACTOR + 1).checkState(), "Not closed after interval end");
         assertTrue(breaker.isClosed(), "Not closed at end");
     }
 
     /**
      * Tests that the closing interval is the same as the opening interval if it is not
      * specified.
      */
     @Test
     void testDefaultClosingInterval() {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD);
         assertEquals(NANO_FACTOR, breaker.getClosingInterval(), "Wrong closing interval");
     }
 
     /**
      * Tests that the closing threshold is the same as the opening threshold if not
      * specified otherwise.
      */
     @Test
     void testDefaultClosingThreshold() {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS);
         assertEquals(NANO_FACTOR, breaker.getClosingInterval(), "Wrong closing interval");
         assertEquals(OPENING_THRESHOLD, breaker.getClosingThreshold(), "Wrong closing threshold");
     }
 
     /**
      * Tests that a circuit breaker is closed after its creation.
      */
     @Test
     void testInitiallyClosed() {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS);
         assertFalse(breaker.isOpen(), "Open");
         assertTrue(breaker.isClosed(), "Not closed");
     }
 
     /**
      * Tests that time units are correctly taken into account by constructors.
      */
     @Test
     void testIntervalCalculation() {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 2, TimeUnit.MILLISECONDS);
         assertEquals(NANO_FACTOR, breaker.getOpeningInterval(), "Wrong opening interval");
         assertEquals(2 * NANO_FACTOR / 1000, breaker.getClosingInterval(), "Wrong closing interval");
     }
 
     /**
      * Tests that an open circuit breaker does not close itself when the number of events
      * received is over the threshold.
      */
     @Test
     void testNotClosingOverThreshold() {
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD,
                 10, TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         long startTime = 0;
         breaker.open();
         for (int i = 0; i <= CLOSING_THRESHOLD; i++) {
             assertFalse(breaker.at(startTime).incrementAndCheckState(), "Not open");
             startTime += 1000;
         }
         assertFalse(breaker.at(startTime + NANO_FACTOR).incrementAndCheckState(), "Closed in new interval");
         assertTrue(breaker.isOpen(), "Not open at end");
     }
 
     /**
      * Tests that the circuit breaker stays closed if there are a number of received
      * events, but not in a single check interval.
      */
     @Test
     void testNotOpeningCheckIntervalExceeded() {
         long startTime = 0L;
         final long timeIncrement = 3 * NANO_FACTOR / (2 * OPENING_THRESHOLD);
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         for (int i = 0; i < 5 * OPENING_THRESHOLD; i++) {
             assertTrue(breaker.at(startTime).incrementAndCheckState(), "In open state");
             startTime += timeIncrement;
         }
         assertTrue(breaker.isClosed(), "Not closed");
     }
 
     /**
      * Tests that the circuit breaker stays closed if the number of received events stays
      * below the threshold.
      */
     @Test
     void testNotOpeningUnderThreshold() {
         long startTime = 1000;
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         for (int i = 0; i < OPENING_THRESHOLD - 1; i++) {
             assertTrue(breaker.at(startTime).incrementAndCheckState(), "In open state");
             startTime++;
         }
         assertTrue(breaker.isClosed(), "Not closed");
     }
 
     /**
      * Tests whether the current time is correctly determined.
      */
     @Test
     void testNow() {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS);
         final long nowNanos = breaker.nanoTime();
         final long deltaNanos = Math.abs(System.nanoTime() - nowNanos);
         assertTrue(deltaNanos < 100_000, String.format("Delta %,d ns to current time too large", deltaNanos));
     }
 
     /**
      * Tests that the circuit breaker opens if all conditions are met.
      */
     @Test
     void testOpeningWhenThresholdReached() {
         long startTime = 0;
         final long timeIncrement = NANO_FACTOR / OPENING_THRESHOLD - 1;
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         boolean open = false;
         for (int i = 0; i < OPENING_THRESHOLD + 1; i++) {
             open = !breaker.at(startTime).incrementAndCheckState();
             startTime += timeIncrement;
         }
         assertTrue(open, "Not open");
         assertFalse(breaker.isClosed(), "Closed");
     }
 
     /**
      * Tests that the circuit breaker opens if all conditions are met when using
      * {@link EventCountCircuitBreaker#incrementAndCheckState(Integer increment)}.
      */
     @Test
     void testOpeningWhenThresholdReachedThroughBatch() {
         final long timeIncrement = NANO_FACTOR / OPENING_THRESHOLD - 1;
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 1,
             TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         final long startTime = timeIncrement * (OPENING_THRESHOLD + 1);
         final boolean open = !breaker.at(startTime).incrementAndCheckState(OPENING_THRESHOLD + 1);
         assertTrue(open, "Not open");
         assertFalse(breaker.isClosed(), "Closed");
     }
 
     /**
      * Tests whether an explicit open operation fully initializes the internal check data
      * object. Otherwise, the circuit breaker may close itself directly afterwards.
      */
     @Test
     void testOpenStartsNewCheckInterval() {
         final EventCountCircuitBreakerTestImpl breaker = new EventCountCircuitBreakerTestImpl(OPENING_THRESHOLD, 2,
                 TimeUnit.SECONDS, CLOSING_THRESHOLD, 1, TimeUnit.SECONDS);
         breaker.at(NANO_FACTOR - 1000).open();
         assertTrue(breaker.isOpen(), "Not open");
         assertFalse(breaker.at(NANO_FACTOR + 100).checkState(), "Already closed");
     }
 
     /**
      * Tests whether a change listener can be removed.
      */
     @Test
     void testRemoveChangeListener() {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS);
         final ChangeListener listener = new ChangeListener(breaker);
         breaker.addChangeListener(listener);
         breaker.open();
         breaker.removeChangeListener(listener);
         breaker.close();
         listener.verify(Boolean.TRUE);
     }
 
     /**
      * Tests that a state transition triggered by multiple threads is handled correctly.
      * Only the first transition should cause an event to be sent.
      */
     @Test
     void testStateTransitionGuarded() throws InterruptedException {
         final EventCountCircuitBreaker breaker = new EventCountCircuitBreaker(OPENING_THRESHOLD, 1,
                 TimeUnit.SECONDS);
         final ChangeListener listener = new ChangeListener(breaker);
         breaker.addChangeListener(listener);
 
         final int threadCount = 128;
         final CountDownLatch latch = new CountDownLatch(1);
         final Thread[] threads = new Thread[threadCount];
         for (int i = 0; i < threadCount; i++) {
             threads[i] = new Thread() {
                 @Override
                 public void run() {
                     try {
                         latch.await();
                     } catch (final InterruptedException iex) {
                         // ignore
                     }
                     breaker.open();
                 }
             };
             threads[i].start();
         }
         latch.countDown();
         for (final Thread thread : threads) {
             thread.join();
         }
         listener.verify(Boolean.TRUE);
     }
 }