/*
    * Copyright 2019 LINE Corporation
    *
    * LINE Corporation licenses this file to you 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:
    *
    *   https://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.linecorp.centraldogma.server.internal.mirror;
  
  import static java.util.Objects.requireNonNull;
  
  import java.io.File;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.CompletionStage;
  
  import org.jspecify.annotations.Nullable;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.google.common.base.MoreObjects;
  
  import com.linecorp.centraldogma.server.CentralDogmaConfig;
  import com.linecorp.centraldogma.server.ZoneConfig;
  import com.linecorp.centraldogma.server.mirror.MirroringServicePluginConfig;
  import com.linecorp.centraldogma.server.plugin.Plugin;
  import com.linecorp.centraldogma.server.plugin.PluginContext;
  import com.linecorp.centraldogma.server.plugin.PluginTarget;
  
  public final class DefaultMirroringServicePlugin implements Plugin {
  
      private static final Logger logger = LoggerFactory.getLogger(DefaultMirroringServicePlugin.class);
  
      @Nullable
      public static MirroringServicePluginConfig mirrorConfig(CentralDogmaConfig config) {
          return (MirroringServicePluginConfig) config.pluginConfigMap().get(MirroringServicePluginConfig.class);
      }
  
      @Nullable
      private volatile MirrorSchedulingService mirroringService;
  
      @Nullable
      private PluginTarget pluginTarget;
  
      @Override
      public PluginTarget target(CentralDogmaConfig config) {
          requireNonNull(config, "config");
          if (pluginTarget != null) {
              return pluginTarget;
          }
  
          final MirroringServicePluginConfig mirrorConfig = mirrorConfig(config);
          if (mirrorConfig != null && mirrorConfig.zonePinned()) {
              pluginTarget = PluginTarget.ZONE_LEADER_ONLY;
          } else {
              pluginTarget = PluginTarget.LEADER_ONLY;
          }
          return pluginTarget;
      }
  
      @Override
      public synchronized CompletionStage<Void> start(PluginContext context) {
          requireNonNull(context, "context");
  
          MirrorSchedulingService mirroringService = this.mirroringService;
          if (mirroringService == null) {
              final CentralDogmaConfig cfg = context.config();
              final MirroringServicePluginConfig mirroringServicePluginConfig = mirrorConfig(cfg);
              final int numThreads;
              final int maxNumFilesPerMirror;
              final long maxNumBytesPerMirror;
              final ZoneConfig zoneConfig;
  
              if (mirroringServicePluginConfig != null) {
                  numThreads = mirroringServicePluginConfig.numMirroringThreads();
                  maxNumFilesPerMirror = mirroringServicePluginConfig.maxNumFilesPerMirror();
                  maxNumBytesPerMirror = mirroringServicePluginConfig.maxNumBytesPerMirror();
                  if (mirroringServicePluginConfig.zonePinned()) {
                      zoneConfig = cfg.zone();
                      assert zoneConfig != null : "zonePinned is enabled but no zone configuration found";
                  } else {
                      zoneConfig = null;
                  }
                  if (mirroringServicePluginConfig.trustedHostKeys().isEmpty()) {
                      logger.warn("No 'trustedHostKeys' configured in the mirroring service plugin config. " +
                                  "SSH mirror connections will accept any host key without verification.");
                  }
              } else {
                  numThreads = MirroringServicePluginConfig.INSTANCE.numMirroringThreads();
                  maxNumFilesPerMirror = MirroringServicePluginConfig.INSTANCE.maxNumFilesPerMirror();
                  maxNumBytesPerMirror = MirroringServicePluginConfig.INSTANCE.maxNumBytesPerMirror();
                  zoneConfig = null;
                 logger.warn("No 'trustedHostKeys' configured in the mirroring service plugin config. " +
                             "SSH mirror connections will accept any host key without verification.");
             }
             mirroringService = new MirrorSchedulingService(new File(cfg.dataDir(), "_mirrors"),
                                                            context.projectManager(),
                                                            context.meterRegistry(),
                                                            numThreads,
                                                            maxNumFilesPerMirror,
                                                            maxNumBytesPerMirror, zoneConfig,
                                                            context.mirrorAccessController());
             this.mirroringService = mirroringService;
         }
         mirroringService.start(context.commandExecutor());
         return CompletableFuture.completedFuture(null);
     }
 
     @Override
     public synchronized CompletionStage<Void> stop(PluginContext context) {
         final MirrorSchedulingService mirroringService = this.mirroringService;
         if (mirroringService != null && mirroringService.isStarted()) {
             mirroringService.stop();
         }
         return CompletableFuture.completedFuture(null);
     }
 
     @Override
     public Class<?> configType() {
         return MirroringServicePluginConfig.class;
     }
 
     @Nullable
     public MirrorSchedulingService mirroringService() {
         return mirroringService;
     }
 
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
                           .omitNullValues()
                           .add("configType", configType().getName())
                           .add("target", pluginTarget)
                           .toString();
     }
 }