code: /*
   *  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.skywalking.oap.server.receiver.otel.otlp;
  
  import io.opentelemetry.proto.metrics.v1.ExponentialHistogram;
  import io.opentelemetry.proto.metrics.v1.ExponentialHistogramDataPoint;
  import io.opentelemetry.proto.metrics.v1.Metric;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  import org.apache.skywalking.oap.server.library.module.ModuleManager;
  import org.apache.skywalking.oap.server.library.util.prometheus.metrics.Histogram;
  import org.apache.skywalking.oap.server.receiver.otel.OtelMetricReceiverConfig;
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  public class OpenTelemetryMetricRequestProcessorTest {
  
      private OtelMetricReceiverConfig config;
  
      private ModuleManager manager;
  
      private OpenTelemetryMetricRequestProcessor metricRequestProcessor;
  
      private Map<String, String> nodeLabels;
  
      @BeforeEach
      public void setUp() {
          manager = new ModuleManager();
          config = new OtelMetricReceiverConfig();
          metricRequestProcessor = new OpenTelemetryMetricRequestProcessor(manager, config);
          nodeLabels = new HashMap<>();
      }
  
      @Test
      public void testAdaptExponentialHistogram() throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
          Class<OpenTelemetryMetricRequestProcessor> clazz = OpenTelemetryMetricRequestProcessor.class;
          Method adaptMetricsMethod = clazz.getDeclaredMethod("adaptMetrics", Map.class, Metric.class);
          adaptMetricsMethod.setAccessible(true);
  
          // number is 4; 7, 7.5; 8.5, 8.7, 9.4
          var positiveBuckets = ExponentialHistogramDataPoint.Buckets.newBuilder()
                                                                     .setOffset(10)
                                                                     .addBucketCounts(
                                                                         1) // (0, 6.72]
                                                                     .addBucketCounts(
                                                                         2
                                                                     ) // (6.72, 8]
                                                                     .addBucketCounts(
                                                                         3
                                                                     ) // (8, 9.51]
                                                                     .build();
          // number is -14, -14.5, -15; -18; -21, -26
          var negativeBuckets = ExponentialHistogramDataPoint.Buckets.newBuilder()
                                                                     .setOffset(15)
                                                                     .addBucketCounts(
                                                                         3
                                                                     ) // (-16, -13.45]
                                                                     .addBucketCounts(
                                                                         1
                                                                     ) // (-19.02, -16]
                                                                     .addBucketCounts(
                                                                         2
                                                                     ) // (-INFINITY, -19.02]
                                                                     .build();
          var dataPoint = ExponentialHistogramDataPoint.newBuilder()
                                                       .setCount(12)
                                                       .setSum(-63.4)
                                                       .setScale(2)
                                                       .setPositive(positiveBuckets)
                                                       .setNegative(negativeBuckets)
                                                       .setTimeUnixNano(1000000)
                                                       .build();
          ExponentialHistogram exponentialHistogram = ExponentialHistogram.newBuilder()
                                                                          .addDataPoints(dataPoint)
                                                                          .build();
          Metric metric = Metric.newBuilder()
                                .setName("test_metric")
                                .setExponentialHistogram(exponentialHistogram)
                                .build();
  
          Stream<Histogram> stream = (Stream<Histogram>) adaptMetricsMethod.invoke(
              metricRequestProcessor, nodeLabels, metric);
          List<Histogram> list = stream.collect(Collectors.toList());
          Histogram histogramMetric = list.get(0);
          assertEquals("test_metric", histogramMetric.getName());
          assertEquals(1, histogramMetric.getTimestamp());
          assertEquals(12, histogramMetric.getSampleCount());
          assertEquals(-63.4, histogramMetric.getSampleSum());
  
          // validate the key and value of bucket
          double base = Math.pow(2, Math.pow(2, -2));
  
          assertTrue(histogramMetric.getBuckets().containsKey(Math.pow(base, 11)));
          assertEquals(1, histogramMetric.getBuckets().get(Math.pow(base, 11)));
  
          assertTrue(histogramMetric.getBuckets().containsKey(Math.pow(base, 12)));
          assertEquals(2, histogramMetric.getBuckets().get(Math.pow(base, 12)));
  
          assertTrue(histogramMetric.getBuckets().containsKey(Double.POSITIVE_INFINITY));
          assertEquals(3, histogramMetric.getBuckets().get(Double.POSITIVE_INFINITY));
  
          assertTrue(histogramMetric.getBuckets().containsKey(-Math.pow(base, 15)));
          assertEquals(3, histogramMetric.getBuckets().get(-Math.pow(base, 15)));
  
          assertTrue(histogramMetric.getBuckets().containsKey(-Math.pow(base, 16)));
          assertEquals(1, histogramMetric.getBuckets().get(-Math.pow(base, 16)));
  
          assertTrue(histogramMetric.getBuckets().containsKey(-Math.pow(base, 17)));
          assertEquals(2, histogramMetric.getBuckets().get(-Math.pow(base, 17)));
      }
  }
  