// Copyright 2018 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.dynamic;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import com.google.devtools.build.lib.actions.ExecutionStrategy;
import com.google.devtools.build.lib.actions.ExecutorInitException;
import com.google.devtools.build.lib.actions.Spawn;
import com.google.devtools.build.lib.actions.SpawnActionContext;
import com.google.devtools.build.lib.actions.Spawns;
import com.google.devtools.build.lib.buildtool.BuildRequest;
import com.google.devtools.build.lib.concurrent.ExecutorUtil;
import com.google.devtools.build.lib.exec.ExecutionPolicy;
import com.google.devtools.build.lib.exec.ExecutorBuilder;
import com.google.devtools.build.lib.runtime.BlazeModule;
import com.google.devtools.build.lib.runtime.Command;
import com.google.devtools.build.lib.runtime.CommandEnvironment;
import com.google.devtools.common.options.OptionsBase;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.logging.Logger;

/**
 * {@link BlazeModule} providing support for dynamic spawn execution and scheduling.
 */
public class DynamicExecutionModule extends BlazeModule {
  private ExecutorService executorService;
  private static final Logger logger = Logger.getLogger(DynamicExecutionModule.class.getName());
  static List<Map.Entry<String, List<String>>> localStrategiesByMnemonic;
  static List<Map.Entry<String, List<String>>> remoteStrategiesByMnemonic;

  @Override
  public Iterable<Class<? extends OptionsBase>> getCommandOptions(Command command) {
    return "build".equals(command.name())
        ? ImmutableList.<Class<? extends OptionsBase>>of(DynamicExecutionOptions.class)
        : ImmutableList.<Class<? extends OptionsBase>>of();
  }

  @Override
  public void beforeCommand(CommandEnvironment env) {
    executorService =
        Executors.newCachedThreadPool(
            new ThreadFactoryBuilder().setNameFormat("dynamic-execution-thread-%d").build());
    env.getEventBus().register(this);
  }

  /**
   * Adds a strategy that backs the dynamic scheduler to the executor builder.
   *
   * @param builder the executor builder to modify
   * @param name the name of the strategy
   * @param flagName name of the flag the strategy came from; used for error reporting
   *     purposes only
   * @throws ExecutorInitException if the provided strategy would cause a scheduling cycle
   */
  private static void addBackingStrategy(ExecutorBuilder builder, String name, String flagName)
      throws ExecutorInitException {
    ExecutionStrategy strategy = DynamicSpawnStrategy.class.getAnnotation(ExecutionStrategy.class);
    checkNotNull(strategy, "DynamicSpawnStrategy lacks expected ExecutionStrategy annotation");

    if (Arrays.asList(strategy.name()).contains(name)) {
      throw new ExecutorInitException("Cannot use strategy " + name + " in flag " + flagName
          + " as it would create a cycle during execution");
    }

    builder.addStrategyByContext(SpawnActionContext.class, name);
  }

  private static void addStrategiesByMnemonic(
      List<Map.Entry<String, List<String>>> strategies, ExecutorBuilder builder, String flagName)
      throws ExecutorInitException {
    List<String> mnemonics = new ArrayList<>();
    for (Map.Entry<String, List<String>> entry : strategies) {
      if (mnemonics.contains(entry.getKey())) {
        logger.warning(
            String.format(
                "Strategy for mnemonic %s set twice. Using most recent value (%s)",
                entry.getKey(), entry.getValue()));
      }
      mnemonics.add(entry.getKey());
      for (String strategy : entry.getValue()) {
        addBackingStrategy(builder, strategy, flagName);
      }
    }
  }

  @VisibleForTesting
  static void setDefaultStrategiesByMnemonic(DynamicExecutionOptions options) {
    // Options that set "allowMultiple" to true ignore the default value, so we replicate that
    // functionality here. Additionally, since we are still supporting --dynamic_worker_strategy,
    // but will deprecate it soon, we add its functionality to --dynamic_local_strategy. This allows
    // users to set --dynamic_local_strategy and not --dynamic_worker_strategy to stop defaulting to
    // worker strategy.
    // TODO(steinman): Deprecate --dynamic_worker_strategy and clean this up.
    if (options.dynamicLocalStrategy == null || options.dynamicLocalStrategy.isEmpty()) {
      localStrategiesByMnemonic =
          options.dynamicWorkerStrategy.isEmpty()
              ? ImmutableList.of(Maps.immutableEntry("", ImmutableList.of("worker", "sandboxed")))
              : ImmutableList.of(
                  Maps.immutableEntry(
                      "", ImmutableList.of(options.dynamicWorkerStrategy, "sandboxed")));
    } else {
      localStrategiesByMnemonic = options.dynamicLocalStrategy;
      if (!options.dynamicWorkerStrategy.isEmpty()) {
        for (int i = 0; i < localStrategiesByMnemonic.size(); i++) {
          if ("".equals(localStrategiesByMnemonic.get(i).getKey())) {
            List<String> newValue = Lists.newArrayList(options.dynamicWorkerStrategy);
            newValue.addAll(localStrategiesByMnemonic.get(i).getValue());
            localStrategiesByMnemonic.set(i, Maps.immutableEntry("", newValue));
            break;
          }
        }
      }
    }

    remoteStrategiesByMnemonic =
        (options.dynamicRemoteStrategy == null || options.dynamicRemoteStrategy.isEmpty())
            ? ImmutableList.of(Maps.immutableEntry("", ImmutableList.of("remote")))
            : options.dynamicRemoteStrategy;
  }

  @Override
  public void executorInit(CommandEnvironment env, BuildRequest request, ExecutorBuilder builder)
      throws ExecutorInitException {
    DynamicExecutionOptions options = env.getOptions().getOptions(DynamicExecutionOptions.class);
    if (options.internalSpawnScheduler) {
      if (options.legacySpawnScheduler) {
        builder.addActionContext(
            new LegacyDynamicSpawnStrategy(executorService, options, this::getExecutionPolicy));
      } else {
        builder.addActionContext(
            new DynamicSpawnStrategy(executorService, options, this::getExecutionPolicy));
      }
      builder.addStrategyByContext(SpawnActionContext.class, "dynamic");
      setDefaultStrategiesByMnemonic(options);
      addStrategiesByMnemonic(remoteStrategiesByMnemonic, builder, "--dynamic_remote_strategy");
      addStrategiesByMnemonic(localStrategiesByMnemonic, builder, "--dynamic_local_strategy");
    }
  }

  /**
   * Use the {@link Spawn} metadata to determine if it can be executed locally, remotely, or both.
   * @param spawn the {@link Spawn} action
   * @return the {@link ExecutionPolicy} containing local/remote execution policies
   */
  protected ExecutionPolicy getExecutionPolicy(Spawn spawn) {
    if (!Spawns.mayBeExecutedRemotely(spawn)) {
      return ExecutionPolicy.LOCAL_EXECUTION_ONLY;
    }

    return ExecutionPolicy.ANYWHERE;
  }

  @Override
  public void afterCommand() {
    ExecutorUtil.interruptibleShutdown(executorService);
    executorService = null;
  }
}