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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
   *
   *     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.avro.ipc.stats;
  
  import static org.junit.jupiter.api.Assertions.*;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.TreeSet;
  import org.apache.avro.ipc.stats.Histogram.Entry;
  import org.apache.avro.ipc.stats.Histogram.Segmenter;
  import org.junit.jupiter.api.Test;
  
  public class TestHistogram {
  
    @Test
    void basicOperation() {
      Segmenter<String, Integer> s = new Histogram.TreeMapSegmenter<>(new TreeSet<>(Arrays.asList(0, 1, 2, 4, 8, 16)));
  
      Histogram<String, Integer> h = new Histogram<>(s);
  
      for (int i = 0; i < 20; ++i) {
        h.add(i);
      }
      assertEquals(20, h.getCount());
      assertArrayEquals(new int[] { 1, 1, 2, 4, 8, 4 }, h.getHistogram());
  
      assertEquals("[0,1)=1;[1,2)=1;[2,4)=2;[4,8)=4;[8,16)=8;[16,infinity)=4", h.toString());
  
      String[] correctBucketLabels = { "[0,1)", "[1,2)", "[2,4)", "[4,8)", "[8,16)", "[16,infinity)" };
  
      // test bucket iterator
      int pos = 0;
      Iterator<String> it = h.getSegmenter().getBuckets();
      while (it.hasNext()) {
        assertEquals(correctBucketLabels[pos], it.next());
        pos = pos + 1;
      }
      assertEquals(correctBucketLabels.length, pos);
  
      List<String> labels = h.getSegmenter().getBucketLabels();
      assertEquals(correctBucketLabels.length, labels.size());
      if (labels.size() == correctBucketLabels.length) {
        for (int i = 0; i < labels.size(); i++) {
          assertEquals(correctBucketLabels[i], labels.get(i));
        }
      }
  
      String[] correctBoundryLabels = { "0", "1", "2", "4", "8", "16" };
      List<String> boundryLabels = h.getSegmenter().getBoundaryLabels();
  
      assertEquals(correctBoundryLabels.length, boundryLabels.size());
      if (boundryLabels.size() == correctBoundryLabels.length) {
        for (int i = 0; i < boundryLabels.size(); i++) {
          assertEquals(correctBoundryLabels[i], boundryLabels.get(i));
        }
      }
  
      List<Entry<String>> entries = new ArrayList<>();
      for (Entry<String> entry : h.entries()) {
        entries.add(entry);
      }
      assertEquals("[0,1)", entries.get(0).bucket);
      assertEquals(4, entries.get(5).count);
      assertEquals(6, entries.size());
  
      h.add(1010);
      h.add(9191);
      List<Integer> recent = h.getRecentAdditions();
      assertTrue(recent.contains(1010));
      assertTrue(recent.contains(9191));
  
    }
  
    @Test
    void badValue() {
      assertThrows(Histogram.SegmenterException.class, () -> {
        Segmenter<String, Long> s = new Histogram.TreeMapSegmenter<>(
            new TreeSet<>(Arrays.asList(0L, 1L, 2L, 4L, 8L, 16L)));
  
        Histogram<String, Long> h = new Histogram<>(s);
        h.add(-1L);
      });
    }
  
    /** Only has one bucket */
    static class SingleBucketSegmenter implements Segmenter<String, Float> {
      @Override
      public Iterator<String> getBuckets() {
        return Collections.singletonList("X").iterator();
      }
  
      public List<String> getBoundaryLabels() {
        return Collections.singletonList("X");
      }
  
      public List<String> getBucketLabels() {
        return Collections.singletonList("X");
      }
  
      @Override
      public int segment(Float value) {
        return 0;
      }
  
      @Override
      public int size() {
        return 1;
      }
  
    }
  
    @Test
    void floatHistogram() {
      FloatHistogram<String> h = new FloatHistogram<>(new SingleBucketSegmenter());
      h.add(12.0f);
      h.add(10.0f);
      h.add(20.0f);
  
      assertEquals(3, h.getCount());
      assertEquals(14.0f, h.getMean(), 0.0001);
      assertEquals(5.291f, h.getUnbiasedStdDev(), 0.001);
    }
  
  }
  