// Copyright (C) 2014 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.google.gerrit.server.project;

import com.google.common.util.concurrent.ThreadFactoryBuilder;
import com.google.gerrit.extensions.events.LifecycleListener;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.server.config.GerritServerConfig;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import org.eclipse.jgit.lib.Config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Singleton
public class ProjectCacheWarmer implements LifecycleListener {
  private static final Logger log = LoggerFactory.getLogger(ProjectCacheWarmer.class);

  private final Config config;
  private final ProjectCache cache;

  @Inject
  ProjectCacheWarmer(@GerritServerConfig Config config, ProjectCache cache) {
    this.config = config;
    this.cache = cache;
  }

  @Override
  public void start() {
    int cpus = Runtime.getRuntime().availableProcessors();
    if (config.getBoolean("cache", "projects", "loadOnStartup", false)) {
      ThreadPoolExecutor pool =
          new ScheduledThreadPoolExecutor(
              config.getInt("cache", "projects", "loadThreads", cpus),
              new ThreadFactoryBuilder().setNameFormat("ProjectCacheLoader-%d").build());
      ExecutorService scheduler = Executors.newFixedThreadPool(1);

      log.info("Loading project cache");
      scheduler.execute(
          () -> {
            for (final Project.NameKey name : cache.all()) {
              pool.execute(
                  () -> {
                    cache.get(name);
                  });
            }
            pool.shutdown();
            try {
              pool.awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
              log.info("Finished loading project cache");
            } catch (InterruptedException e) {
              log.warn("Interrupted while waiting for project cache to load");
            }
          });
    }
  }

  @Override
  public void stop() {}
}