content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  package io.opentelemetry.instrumentation.api.internal;
  
  import static org.assertj.core.api.Assertions.assertThat;
  
  import io.opentelemetry.api.metrics.DoubleHistogramBuilder;
  import io.opentelemetry.api.metrics.Meter;
  import io.opentelemetry.api.metrics.MeterProvider;
  import io.opentelemetry.instrumentation.api.instrumenter.OperationMetrics;
  import io.opentelemetry.instrumentation.testing.junit.InstrumentationExtension;
  import io.opentelemetry.instrumentation.testing.junit.LibraryInstrumentationExtension;
  import java.lang.reflect.Proxy;
  import java.util.concurrent.atomic.AtomicBoolean;
  import org.junit.jupiter.api.Test;
  import org.junit.jupiter.api.extension.RegisterExtension;
  
  class OperationMetricsUtilTest {
    @RegisterExtension
    static final InstrumentationExtension testing = LibraryInstrumentationExtension.create();
  
    @Test
    void noWarning() {
      AtomicBoolean warning = new AtomicBoolean(false);
      OperationMetrics operationMetrics =
          OperationMetricsUtil.create(
              "test metrics", meter -> null, (s, doubleHistogramBuilder) -> warning.set(true));
      operationMetrics.create(testing.getOpenTelemetry().getMeter("test"));
  
      assertThat(warning).isFalse();
    }
  
    @Test
    void noWarningWithNoopMetrics() {
      AtomicBoolean warning = new AtomicBoolean(false);
      OperationMetrics operationMetrics =
          OperationMetricsUtil.create(
              "test metrics", meter -> null, (s, doubleHistogramBuilder) -> warning.set(true));
      operationMetrics.create(MeterProvider.noop().get("test"));
  
      assertThat(warning).isFalse();
    }
  
    @Test
    void warning() {
      AtomicBoolean warning = new AtomicBoolean(false);
      OperationMetrics operationMetrics =
          OperationMetricsUtil.create(
              "test metrics", meter -> null, (s, doubleHistogramBuilder) -> warning.set(true));
      Meter defaultMeter = MeterProvider.noop().get("test");
      Meter meter =
          (Meter)
              Proxy.newProxyInstance(
                  Meter.class.getClassLoader(),
                  new Class<?>[] {Meter.class},
                  (proxy, method, args) -> {
                    if ("histogramBuilder".equals(method.getName())) {
                      // proxy the histogram builder so that the builder instance does not implement
                      // ExtendedDoubleHistogramBuilder which will trigger the warning
                      return proxyDoubleHistogramBuilder(defaultMeter);
                    }
                    return method.invoke(defaultMeter, args);
                  });
      operationMetrics.create(meter);
  
      assertThat(warning).isTrue();
    }
  
    private static DoubleHistogramBuilder proxyDoubleHistogramBuilder(Meter meter) {
      return (DoubleHistogramBuilder)
          Proxy.newProxyInstance(
              DoubleHistogramBuilder.class.getClassLoader(),
              new Class<?>[] {DoubleHistogramBuilder.class},
              (proxy1, method1, args1) -> meter.histogramBuilder((String) args1[0]));
    }
  }
  