/*
 * Copyright The OpenTelemetry Authors
 * SPDX-License-Identifier: Apache-2.0
 */

package io.opentelemetry.javaagent.instrumentation.spring.webflux.v5_0.server;

import static io.opentelemetry.javaagent.extension.matcher.AgentElementMatchers.hasClassesNamed;
import static io.opentelemetry.javaagent.extension.matcher.AgentElementMatchers.implementsInterface;
import static io.opentelemetry.javaagent.instrumentation.spring.webflux.v5_0.server.WebfluxSingletons.httpRouteGetter;
import static io.opentelemetry.javaagent.instrumentation.spring.webflux.v5_0.server.WebfluxSingletons.instrumenter;
import static net.bytebuddy.matcher.ElementMatchers.isAbstract;
import static net.bytebuddy.matcher.ElementMatchers.isMethod;
import static net.bytebuddy.matcher.ElementMatchers.isPublic;
import static net.bytebuddy.matcher.ElementMatchers.named;
import static net.bytebuddy.matcher.ElementMatchers.not;
import static net.bytebuddy.matcher.ElementMatchers.takesArgument;
import static net.bytebuddy.matcher.ElementMatchers.takesArguments;

import io.opentelemetry.context.Context;
import io.opentelemetry.context.Scope;
import io.opentelemetry.instrumentation.api.instrumenter.http.HttpServerRoute;
import io.opentelemetry.instrumentation.api.instrumenter.http.HttpServerRouteSource;
import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
import net.bytebuddy.asm.Advice;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.matcher.ElementMatcher;
import org.springframework.web.server.ServerWebExchange;

public class HandlerAdapterInstrumentation implements TypeInstrumentation {

  @Override
  public ElementMatcher<ClassLoader> classLoaderOptimization() {
    return hasClassesNamed("org.springframework.web.reactive.HandlerAdapter");
  }

  @Override
  public ElementMatcher<TypeDescription> typeMatcher() {
    return not(isAbstract())
        .and(implementsInterface(named("org.springframework.web.reactive.HandlerAdapter")));
  }

  @Override
  public void transform(TypeTransformer transformer) {
    transformer.applyAdviceToMethod(
        isMethod()
            .and(isPublic())
            .and(named("handle"))
            .and(takesArgument(0, named("org.springframework.web.server.ServerWebExchange")))
            .and(takesArgument(1, Object.class))
            .and(takesArguments(2)),
        this.getClass().getName() + "$HandleAdvice");
  }

  @SuppressWarnings("unused")
  public static class HandleAdvice {

    @Advice.OnMethodEnter(suppress = Throwable.class)
    public static void methodEnter(
        @Advice.Argument(0) ServerWebExchange exchange,
        @Advice.Argument(1) Object handler,
        @Advice.Local("otelContext") Context context,
        @Advice.Local("otelScope") Scope scope) {

      Context parentContext = Context.current();

      // HttpRouteSource.CONTROLLER has useFirst true, and it will update http.route only once
      // using the last portion of the nested path.
      // HttpRouteSource.NESTED_CONTROLLER has useFirst false, and it will make http.route updated
      // twice: 1st using the last portion of the nested path, 2nd time using the full nested path.
      HttpServerRoute.update(
          parentContext, HttpServerRouteSource.NESTED_CONTROLLER, httpRouteGetter(), exchange);

      if (handler == null) {
        return;
      }

      if (!instrumenter().shouldStart(parentContext, handler)) {
        return;
      }

      context = instrumenter().start(parentContext, handler);
      scope = context.makeCurrent();
    }

    @Advice.OnMethodExit(onThrowable = Throwable.class, suppress = Throwable.class)
    public static void methodExit(
        @Advice.Argument(0) ServerWebExchange exchange,
        @Advice.Argument(1) Object handler,
        @Advice.Thrown Throwable throwable,
        @Advice.Local("otelContext") Context context,
        @Advice.Local("otelScope") Scope scope) {
      if (scope == null) {
        return;
      }
      scope.close();

      if (throwable != null) {
        instrumenter().end(context, handler, null, throwable);
      } else {
        AdviceUtils.registerOnSpanEnd(exchange, context, handler);
        // span finished by wrapped Mono in DispatcherHandlerInstrumentation
        // the Mono is already wrapped at this point, but doesn't read the ON_SPAN_END until
        // the Mono is resolved, which is after this point
      }
    }
  }
}
