/**
 * Copyright (C) 2013 - present by OpenGamma Inc. and the OpenGamma group of companies
 *
 * Please see distribution for license.
 */
package com.opengamma.sesame.proxy;

import java.lang.reflect.Method;

import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.Timer;
import com.opengamma.sesame.config.EngineUtils;

/**
 * A proxy that measured the time taken by each method call and
 * sends it to the metrics repository.
 */
public final class MetricsProxy extends ProxyNodeDecorator {

  private final MetricRegistry _metricRegistry;

  /**
   * Create a metrics proxy using the specified registry to
   * record the timings.
   *
   * @param metricRegistry  registry to record the timings in
   */
  public MetricsProxy(MetricRegistry metricRegistry) {
    _metricRegistry = metricRegistry;
  }

  @Override
  protected boolean decorate(Class<?> interfaceType, Class<?> implementationType) {
    return true;
  }

  @Override
  protected Object invoke(Object proxy, Object delegate, Method method, Object[] args) throws Throwable {
    // this avoids timing calls to toString(),
    // hashCode() etc especially in a debugger
    if (method.getDeclaringClass() != Object.class) {
      String name = generateName(delegate, method);
      try (Timer.Context ignored = _metricRegistry.timer(name).time()) {
        return method.invoke(delegate, args);
      }
    } else {
      return method.invoke(delegate, args);
    }
  }

  private String generateName(Object delegate, Method method) {
    Object proxiedObject = EngineUtils.getProxiedObject(delegate);
    return proxiedObject.getClass().getCanonicalName() + "." + method.getName();
  }

  @Override
  public boolean equals(Object o) {
    // We only care that the other object is also a metrics proxy in which
    // case nodes can safely be cached
    return this == o || (o != null && getClass() == o.getClass());
  }

  @Override
  public int hashCode() {
    return getClass().hashCode();
  }
}