content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  package io.opentelemetry.javaagent.instrumentation.opentelemetryapi;
  
  import static net.bytebuddy.matcher.ElementMatchers.named;
  
  import application.io.opentelemetry.context.ContextStorage;
  import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
  import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
  import io.opentelemetry.javaagent.instrumentation.opentelemetryapi.context.AgentContextStorage;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.function.Function;
  import net.bytebuddy.asm.Advice;
  import net.bytebuddy.description.type.TypeDescription;
  import net.bytebuddy.matcher.ElementMatcher;
  
  /**
   * Returns {@link AgentContextStorage} as the implementation of {@link ContextStorage} in the
   * application classpath. We do this instead of using the normal service loader mechanism to make
   * sure there is no dependency on a system property or possibility of a user overriding this since
   * it's required for instrumentation in the agent to work properly.
   */
  public class ContextStorageWrappersInstrumentation implements TypeInstrumentation {
  
    @Override
    public ElementMatcher<TypeDescription> typeMatcher() {
      return named("application.io.opentelemetry.context.ContextStorageWrappers");
    }
  
    @Override
    public void transform(TypeTransformer transformer) {
      transformer.applyAdviceToMethod(
          named("getWrappers"),
          ContextStorageWrappersInstrumentation.class.getName() + "$AddWrapperAdvice");
    }
  
    @SuppressWarnings("unused")
    public static class AddWrapperAdvice {
  
      @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
      public static void methodExit(
          @Advice.Return(readOnly = false)
              List<Function<? super ContextStorage, ? extends ContextStorage>> wrappers) {
        wrappers = new ArrayList<>(wrappers);
        // AgentContextStorage wrapper doesn't delegate, so needs to be the innermost wrapper
        wrappers.add(0, AgentContextStorage.wrap());
      }
    }
  }
  