/**
 * Copyright (C) 2014-2016 LinkedIn Corp. (pinot-core@linkedin.com)
 *
 * 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 com.linkedin.pinot.transport.metrics;

import com.linkedin.pinot.common.metrics.LatencyMetric;
import com.linkedin.pinot.transport.pool.AsyncPool;
import com.yammer.metrics.core.Sampling;
import com.yammer.metrics.core.Summarizable;


public interface PoolStats<T extends Sampling & Summarizable> {
  /**
   * Get the total number of pool objects created between
   * the starting of the Pool and the call to getStats().
   * Does not include create errors.
   * @return The total number of pool objects created
   */
  int getTotalCreated();

  /**
   * Get the total number of pool objects destroyed between
   * the starting of the Pool and the call to getStats().
   * Includes lifecycle validation failures, disposes,
   * and timed-out objects, but does not include destroy errors.
   * @return The total number of pool objects destroyed
   */
  int getTotalDestroyed();

  /**
   * Get the total number of lifecycle create errors between
   * the starting of the Pool and the call to getStats().
   * @return The total number of create errors
   */
  int getTotalCreateErrors();

  /**
   * Get the total number of lifecycle destroy errors between
   * the starting of the Pool and the call to getStats().
   * @return The total number of destroy errors
   */
  int getTotalDestroyErrors();

  /**
   * Get the total number of pool objects destroyed (or failed to
   * to destroy because of an error) because of disposes or failed
   * lifecycle validations between the starting of the Pool
   * and the call to getStats().
   * @return The total number of destroyed "bad" objects
   */
  int getTotalBadDestroyed();

  /**
   * Get the total number of timed out pool objects between the
   * starting of the Pool and the call to getStats().
   * @return The total number of timed out objects
   */
  int getTotalTimedOut();

  /**
   * Get the number of pool objects checked out at the time of
   * the call to getStats().
   * @return The number of checked out pool objects
   */
  int getCheckedOut();

  /**
   * Get the configured maximum pool size.
   * @return The maximum pool size
   */
  int getMaxPoolSize();

  /**
   * Get the configured minimum pool size.
   * @return The minimum pool size
   */
  int getMinPoolSize();

  /**
   * Get the pool size at the time of the call to getStats().
   * @return The pool size
   */
  int getPoolSize();

  /**
   * Get the maximum number of checked out objects. Reset
   * after each call to getStats().
   * @return The maximum number of checked out objects
   */
  int getSampleMaxCheckedOut();

  /**
   * Get the maximum pool size. Reset after each call to
   * getStats().
   * @return The maximum pool size
   */
  int getSampleMaxPoolSize();

  /**
   * Get the number of objects that are idle(not checked out)
   * in the pool.
   * @return The number of idle objects
   */
  int getIdleCount();

  /**
   * Get the wait time to get pooled object
   * @return
   */
  LatencyMetric<T> getWaitTime();

  /**
   * Get stats collected from {@link AsyncPool.Lifecycle}
   * @return Lifecycle stats
   */
  LifecycleStats<T> getLifecycleStats();

  /**
   * Return a string which represents the pool stats
   */
  @Override
  String toString();

  /**
   * Refresh stats
   */
  void refresh();

  public class LifecycleStats<T extends Sampling & Summarizable> {
    private final LatencyMetric<T> _latencyMetric;

    public LifecycleStats(LatencyMetric<T> metric) {
      _latencyMetric = metric;
    }

    /**
     * Get latency metric for creating resources
     * @return
     */
    public LatencyMetric<T> getCreateTime() {
      return _latencyMetric;
    }

    @Override
    public String toString() {
      return "LifecycleStats [_latencyMetric=" + _latencyMetric + "]";
    }

  }
}