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/*
 * Copyright © 2012 The Feign Authors ([email protected])
 *
 * Licensed 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 feign.micrometer;

import static feign.micrometer.MetricTagResolver.EMPTY_TAGS_ARRAY;

import feign.*;
import io.micrometer.core.instrument.*;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

/** Wrap feign {@link InvocationHandler} with metrics. */
public class MeteredInvocationHandleFactory implements InvocationHandlerFactory {

  /**
   * Methods that are declared by super class object and, if invoked, we don't wanna record metrics
   * for
   */
  private static final List JAVA_OBJECT_METHODS =
      Arrays.asList("equals", "toString", "hashCode");

  private final InvocationHandlerFactory invocationHandler;
  private final MeterRegistry meterRegistry;
  private final MetricName metricName;
  private final MetricTagResolver metricTagResolver;

  public MeteredInvocationHandleFactory(
      InvocationHandlerFactory invocationHandler, MeterRegistry meterRegistry) {
    this(
        invocationHandler,
        meterRegistry,
        new FeignMetricName(Feign.class),
        new FeignMetricTagResolver());
  }

  public MeteredInvocationHandleFactory(
      InvocationHandlerFactory invocationHandler,
      MeterRegistry meterRegistry,
      MetricName metricName,
      MetricTagResolver metricTagResolver) {
    this.invocationHandler = invocationHandler;
    this.meterRegistry = meterRegistry;
    this.metricName = metricName;
    this.metricTagResolver = metricTagResolver;
  }

  @Override
  public InvocationHandler create(Target target, Map dispatch) {
    final InvocationHandler invocationHandle = invocationHandler.create(target, dispatch);
    return (proxy, method, args) -> {
      if (JAVA_OBJECT_METHODS.contains(method.getName()) || Util.isDefault(method)) {
        return invocationHandle.invoke(proxy, method, args);
      }

      final Timer.Sample sample = Timer.start(meterRegistry);
      Timer timer = null;
      try {
        final Object invoke = invocationHandle.invoke(proxy, method, args);
        timer = createTimer(target, method, args, null);
        return invoke;
      } catch (final FeignException e) {
        timer = createTimer(target, method, args, e);
        createFeignExceptionCounter(target, method, args, e).increment();
        throw e;
      } catch (final Throwable e) {
        timer = createTimer(target, method, args, e);
        throw e;
      } finally {
        if (timer == null) {
          timer = createTimer(target, method, args, null);
        }
        sample.stop(timer);
      }
    };
  }

  protected Timer createTimer(Target target, Method method, Object[] args, Throwable e) {
    final Tag[] extraTags = extraTags(target, method, args, e);
    final Tags allTags = metricTagResolver.tag(target.type(), method, target.url(), e, extraTags);
    return meterRegistry.timer(metricName.name(e), allTags);
  }

  protected Counter createFeignExceptionCounter(
      Target target, Method method, Object[] args, FeignException e) {
    final Tag[] extraTags = extraTags(target, method, args, e);
    final Tags allTags =
        metricTagResolver
            .tag(target.type(), method, target.url(), e, extraTags)
            .and(
                Tag.of("http_status", String.valueOf(e.status())),
                Tag.of("error_group", e.status() / 100 + "xx"));
    return meterRegistry.counter(metricName.name("http_error"), allTags);
  }

  protected Tag[] extraTags(Target target, Method method, Object[] args, Throwable throwable) {
    return EMPTY_TAGS_ARRAY;
  }
}