// Copyright (C) 2019 The Android Open Source Project
//
// 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.googlesource.gerrit.plugins.healthcheck.check;

import static com.googlesource.gerrit.plugins.healthcheck.check.HealthCheckNames.ACTIVEWORKERS;

import com.codahale.metrics.MetricRegistry;
import com.google.common.util.concurrent.ListeningExecutorService;
import com.google.gerrit.metrics.MetricMaker;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.gerrit.server.config.ThreadSettingsConfig;
import com.google.inject.Inject;
import com.googlesource.gerrit.plugins.healthcheck.HealthCheckConfig;
import java.util.Optional;
import org.eclipse.jgit.lib.Config;

public class ActiveWorkersCheck extends AbstractHealthCheck {

  public static final String ACTIVE_WORKERS_METRIC_NAME =
      "queue/ssh_interactive_worker/active_threads";

  private Integer threshold;
  private Integer interactiveThreadsMaxPoolSize;
  private MetricRegistry metricRegistry;

  @Inject
  public ActiveWorkersCheck(
      @GerritServerConfig Config gerritConfig,
      ListeningExecutorService executor,
      HealthCheckConfig healthCheckConfig,
      ThreadSettingsConfig threadSettingsConfig,
      MetricRegistry metricRegistry,
      MetricMaker metricMaker) {
    super(executor, healthCheckConfig, ACTIVEWORKERS, metricMaker);
    this.threshold = healthCheckConfig.getActiveWorkersThreshold(ACTIVEWORKERS);
    this.metricRegistry = metricRegistry;
    this.interactiveThreadsMaxPoolSize =
        getInteractiveThreadsMaxPoolSize(threadSettingsConfig, gerritConfig);
  }

  @Override
  protected Result doCheck() throws Exception {
    return Optional.ofNullable(metricRegistry.getGauges().get(ACTIVE_WORKERS_METRIC_NAME))
        .map(
            metric -> {
              float currentInteractiveThreadsPercentage =
                  ((long) metric.getValue() * 100) / interactiveThreadsMaxPoolSize;
              return (currentInteractiveThreadsPercentage <= threshold)
                  ? Result.PASSED
                  : Result.FAILED;
            })
        .orElse(Result.PASSED);
  }

  /**
   * This method is following logic from com.google.gerrit.sshd.CommandExecutorQueueProvider
   *
   * <p>We are not able to use "queue/ssh_interactive_worker/max_pool_size" metric because in
   * current implementation it's always returning Integer.MAX_VALUE.
   *
   * @return max number of allowed threads in interactive work queue
   */
  private Integer getInteractiveThreadsMaxPoolSize(
      ThreadSettingsConfig threadSettingsConfig, Config gerritConfig) {
    int poolSize = threadSettingsConfig.getSshdThreads();
    int batchThreads =
        gerritConfig.getInt("sshd", "batchThreads", threadSettingsConfig.getSshdBatchTreads());
    if (batchThreads > poolSize) {
      poolSize += batchThreads;
    }
    return Math.max(1, poolSize - batchThreads);
  }
}