content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  package io.opentelemetry.javaagent.instrumentation.grpc.v1_6;
  
  import static io.opentelemetry.javaagent.extension.matcher.AgentElementMatchers.extendsClass;
  import static io.opentelemetry.javaagent.extension.matcher.AgentElementMatchers.hasClassesNamed;
  import static net.bytebuddy.matcher.ElementMatchers.declaresField;
  import static net.bytebuddy.matcher.ElementMatchers.isMethod;
  import static net.bytebuddy.matcher.ElementMatchers.named;
  
  import io.grpc.ClientInterceptor;
  import io.grpc.ManagedChannelBuilder;
  import io.opentelemetry.instrumentation.api.util.VirtualField;
  import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
  import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
  import java.util.List;
  import net.bytebuddy.asm.Advice;
  import net.bytebuddy.description.type.TypeDescription;
  import net.bytebuddy.matcher.ElementMatcher;
  
  public class GrpcClientBuilderBuildInstrumentation implements TypeInstrumentation {
    @Override
    public ElementMatcher<ClassLoader> classLoaderOptimization() {
      return hasClassesNamed("io.grpc.ManagedChannelBuilder");
    }
  
    @Override
    public ElementMatcher<TypeDescription> typeMatcher() {
      return extendsClass(named("io.grpc.ManagedChannelBuilder"))
          .and(declaresField(named("interceptors")));
    }
  
    @Override
    public void transform(TypeTransformer transformer) {
      transformer.applyAdviceToMethod(
          isMethod().and(named("build")),
          GrpcClientBuilderBuildInstrumentation.class.getName() + "$AddInterceptorAdvice");
    }
  
    @SuppressWarnings("unused")
    public static class AddInterceptorAdvice {
  
      @Advice.OnMethodEnter(suppress = Throwable.class)
      public static void addInterceptor(
          @Advice.This ManagedChannelBuilder<?> builder,
          @Advice.FieldValue("interceptors") List<ClientInterceptor> interceptors) {
        VirtualField<ManagedChannelBuilder<?>, Boolean> instrumented =
            VirtualField.find(ManagedChannelBuilder.class, Boolean.class);
        if (!Boolean.TRUE.equals(instrumented.get(builder))) {
          interceptors.add(0, GrpcSingletons.CLIENT_INTERCEPTOR);
          instrumented.set(builder, true);
        }
      }
    }
  }
  