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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.
   */
  package org.apache.kafka.common.metrics.stats;
  
  import org.apache.kafka.common.MetricName;
  import org.apache.kafka.common.metrics.CompoundStat.NamedMeasurable;
  import org.apache.kafka.common.metrics.JmxReporter;
  import org.apache.kafka.common.metrics.MetricConfig;
  import org.apache.kafka.common.metrics.Metrics;
  import org.apache.kafka.common.metrics.Sensor;
  import org.apache.kafka.common.utils.MockTime;
  import org.apache.kafka.common.utils.Time;
  
  import org.junit.jupiter.api.AfterEach;
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  import java.util.Collections;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  
  public class FrequenciesTest {
  
      private static final double DELTA = 0.0001d;
      private MetricConfig config;
      private Time time;
      private Metrics metrics;
  
      @BeforeEach
      public void setup() {
          config = new MetricConfig().eventWindow(50).samples(2);
          time = new MockTime();
          metrics = new Metrics(config, Collections.singletonList(new JmxReporter()), time, true);
      }
  
      @AfterEach
      public void tearDown() {
          metrics.close();
      }
  
      @Test
      public void testFrequencyCenterValueAboveMax() {
          assertThrows(IllegalArgumentException.class,
              () -> new Frequencies(4, 1.0, 4.0, freq("1", 1.0), freq("2", 20.0)));
      }
  
      @Test
      public void testFrequencyCenterValueBelowMin() {
          assertThrows(IllegalArgumentException.class,
              () -> new Frequencies(4, 1.0, 4.0, freq("1", 1.0), freq("2", -20.0)));
      }
  
      @Test
      public void testMoreFrequencyParametersThanBuckets() {
          assertThrows(IllegalArgumentException.class,
              () -> new Frequencies(1, 1.0, 4.0, freq("1", 1.0), freq("2", -20.0)));
      }
  
      @Test
      public void testBooleanFrequenciesStrategy1() {
          MetricName metricTrue = metricName("true");
          MetricName metricFalse = metricName("false");
          Frequencies frequencies = Frequencies.forBooleanValues(metricFalse, metricTrue);
          final NamedMeasurable falseMetric = frequencies.stats().get(0);
          final NamedMeasurable trueMetric = frequencies.stats().get(1);
  
          // Record 25 "false" and 75 "true"
          for (int i = 0; i != 25; ++i) {
              frequencies.record(config, 0.0, time.milliseconds());
          }
          for (int i = 0; i != 75; ++i) {
              frequencies.record(config, 1.0, time.milliseconds());
          }
          assertEquals(0.25, falseMetric.stat().measure(config, time.milliseconds()), DELTA);
          assertEquals(0.75, trueMetric.stat().measure(config, time.milliseconds()), DELTA);
      }
  
      @Test
      public void testBooleanFrequenciesStrategy2() {
          MetricName metricTrue = metricName("true");
          MetricName metricFalse = metricName("false");
          Frequencies frequencies = Frequencies.forBooleanValues(metricFalse, metricTrue);
          final NamedMeasurable falseMetric = frequencies.stats().get(0);
          final NamedMeasurable trueMetric = frequencies.stats().get(1);
  
          // Record 40 "false" and 60 "true"
          for (int i = 0; i != 40; ++i) {
              frequencies.record(config, 0.0, time.milliseconds());
          }
          for (int i = 0; i != 60; ++i) {
              frequencies.record(config, 1.0, time.milliseconds());
          }
          assertEquals(0.40, falseMetric.stat().measure(config, time.milliseconds()), DELTA);
          assertEquals(0.60, trueMetric.stat().measure(config, time.milliseconds()), DELTA);
      }
  
      @Test
      public void testWithMetricsStrategy1() {
          Frequencies frequencies = new Frequencies(4, 1.0, 4.0, freq("1", 1.0),
                  freq("2", 2.0), freq("3", 3.0), freq("4", 4.0));
          Sensor sensor = metrics.sensor("test", config);
          sensor.add(frequencies);
  
          // Record 100 events uniformly between all buckets
          for (int i = 0; i < 100; ++i) {
              frequencies.record(config, i % 4 + 1, time.milliseconds());
          }
          assertEquals(0.25, metricValue("1"), DELTA);
          assertEquals(0.25, metricValue("2"), DELTA);
          assertEquals(0.25, metricValue("3"), DELTA);
          assertEquals(0.25, metricValue("4"), DELTA);
      }
  
      @Test
      public void testWithMetricsStrategy2() {
          Frequencies frequencies = new Frequencies(4, 1.0, 4.0, freq("1", 1.0),
                  freq("2", 2.0), freq("3", 3.0), freq("4", 4.0));
          Sensor sensor = metrics.sensor("test", config);
          sensor.add(frequencies);
  
          // Record 100 events half-half between 1st and 2nd buckets
          for (int i = 0; i < 100; ++i) {
              frequencies.record(config, i % 2 + 1, time.milliseconds());
          }
          assertEquals(0.50, metricValue("1"), DELTA);
          assertEquals(0.50, metricValue("2"), DELTA);
          assertEquals(0.00, metricValue("3"), DELTA);
          assertEquals(0.00, metricValue("4"), DELTA);
      }
  
      @Test
      public void testWithMetricsStrategy3() {
          Frequencies frequencies = new Frequencies(4, 1.0, 4.0, freq("1", 1.0),
                  freq("2", 2.0), freq("3", 3.0), freq("4", 4.0));
          Sensor sensor = metrics.sensor("test", config);
          sensor.add(frequencies);
  
          // Record 50 events half-half between 1st and 2nd buckets
          for (int i = 0; i < 50; ++i) {
              frequencies.record(config, i % 2 + 1, time.milliseconds());
          }
          // Record 50 events to 4th bucket
          for (int i = 0; i < 50; ++i) {
              frequencies.record(config, 4.0, time.milliseconds());
          }
          assertEquals(0.25, metricValue("1"), DELTA);
          assertEquals(0.25, metricValue("2"), DELTA);
          assertEquals(0.00, metricValue("3"), DELTA);
          assertEquals(0.50, metricValue("4"), DELTA);
      }
  
      private MetricName metricName(String name) {
          return new MetricName(name, "group-id", "desc", Collections.emptyMap());
      }
  
      private Frequency freq(String name, double value) {
          return new Frequency(metricName(name), value);
      }
  
      private double metricValue(String name) {
          return (double) metrics.metrics().get(metricName(name)).metricValue();
      }
  }
  