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   * 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.
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  package org.apache.kafka.server.quota;
  
  import org.apache.kafka.common.MetricName;
  import org.apache.kafka.common.metrics.KafkaMetric;
  import org.apache.kafka.common.metrics.MetricConfig;
  import org.apache.kafka.common.metrics.Quota;
  import org.apache.kafka.common.metrics.QuotaViolationException;
  import org.apache.kafka.common.metrics.stats.Rate;
  import org.apache.kafka.common.metrics.stats.Value;
  import org.apache.kafka.common.utils.MockTime;
  import org.apache.kafka.common.utils.Time;
  
  import org.junit.jupiter.api.Test;
  
  import java.util.Map;
  import java.util.concurrent.TimeUnit;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  public class QuotaUtilsTest {
  
      private final Time time = new MockTime();
      private final int numSamples = 10;
      private final int maxThrottleTimeMs = 500;
      private final MetricName metricName = new MetricName("test-metric", "groupA", "testA", Map.of());
  
      @Test
      public void testThrottleTimeObservedRateEqualsQuota() {
          int numSamples = 10;
          double observedValue = 16.5;
  
          assertEquals(0, throttleTime(observedValue, observedValue, numSamples));
  
          // should be independent of window size
          assertEquals(0, throttleTime(observedValue, observedValue, numSamples + 1));
      }
  
      @Test
      public void testThrottleTimeObservedRateBelowQuota() {
          double observedValue = 16.5;
          double quota = 20.4;
          assertTrue(throttleTime(observedValue, quota, numSamples) < 0);
  
          // should be independent of window size
          assertTrue(throttleTime(observedValue, quota, numSamples + 1) < 0);
      }
  
      @Test
      public void testThrottleTimeObservedRateAboveQuota() {
          double quota = 50.0;
          double observedValue = 100.0;
          assertEquals(2000, throttleTime(observedValue, quota, 3));
      }
  
      @Test
      public void testBoundedThrottleTimeObservedRateEqualsQuota() {
          double observedValue = 18.2;
          assertEquals(0, boundedThrottleTime(observedValue, observedValue, numSamples, maxThrottleTimeMs));
  
          // should be independent of window size
          assertEquals(0, boundedThrottleTime(observedValue, observedValue, numSamples + 1, maxThrottleTimeMs));
      }
  
      @Test
      public void testBoundedThrottleTimeObservedRateBelowQuota() {
          double observedValue = 16.5;
          double quota = 22.4;
  
          assertTrue(boundedThrottleTime(observedValue, quota, numSamples, maxThrottleTimeMs) < 0);
  
          // should be independent of window size
          assertTrue(boundedThrottleTime(observedValue, quota, numSamples + 1, maxThrottleTimeMs) < 0);
      }
  
      @Test
      public void testBoundedThrottleTimeObservedRateAboveQuotaBelowLimit() {
          double quota = 50.0;
          double observedValue = 55.0;
          assertEquals(100, boundedThrottleTime(observedValue, quota, 2, maxThrottleTimeMs));
      }
  
      @Test
      public void testBoundedThrottleTimeObservedRateAboveQuotaAboveLimit() {
          double quota = 50.0;
          double observedValue = 100.0;
          assertEquals(maxThrottleTimeMs, boundedThrottleTime(observedValue, quota, numSamples, maxThrottleTimeMs));
      }
  
      @Test
      public void testThrottleTimeThrowsExceptionIfProvidedNonRateMetric() {
          KafkaMetric testMetric = new KafkaMetric(new Object(), metricName, new Value(), new MetricConfig(), time);
  
          assertThrows(IllegalArgumentException.class,
                  () -> QuotaUtils.throttleTime(new QuotaViolationException(testMetric, 10.0, 20.0), time.milliseconds()));
      }
  
      @Test
      public void testBoundedThrottleTimeThrowsExceptionIfProvidedNonRateMetric() {
          KafkaMetric testMetric = new KafkaMetric(new Object(), metricName, new Value(), new MetricConfig(), time);
  
          assertThrows(IllegalArgumentException.class,
                  () -> QuotaUtils.boundedThrottleTime(new QuotaViolationException(testMetric, 10.0, 20.0), maxThrottleTimeMs, time.milliseconds()));
      }
  
      // the `metric` passed into the returned QuotaViolationException will return windowSize = 'numSamples' - 1
      private QuotaViolationException quotaViolationException(double observedValue, double quota, int numSamples) {
          int sampleWindowSec = 1;
          MetricConfig metricConfig = new MetricConfig()
                  .timeWindow(sampleWindowSec, TimeUnit.SECONDS)
                  .samples(numSamples)
                  .quota(new Quota(quota, true));
          KafkaMetric metric = new KafkaMetric(new Object(), metricName, new Rate(), metricConfig, time);
          return new QuotaViolationException(metric, observedValue, quota);
      }
  
      private long throttleTime(double observedValue, double quota, int numSamples) {
          QuotaViolationException e = quotaViolationException(observedValue, quota, numSamples);
          return QuotaUtils.throttleTime(e, time.milliseconds());
      }
  
      private long boundedThrottleTime(double observedValue, double quota, int numSamples, long maxThrottleTime) {
          QuotaViolationException e = quotaViolationException(observedValue, quota, numSamples);
          return QuotaUtils.boundedThrottleTime(e, maxThrottleTime, time.milliseconds());
      }
  }
  