/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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
 *
 *   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 org.apache.reef.runtime.common.driver.evaluator;

import org.apache.reef.annotations.audience.DriverSide;
import org.apache.reef.annotations.audience.Private;
import org.apache.reef.driver.parameters.DriverIdentifier;
import org.apache.reef.runtime.common.driver.resourcemanager.ResourceAllocationEvent;
import org.apache.reef.tang.annotations.Parameter;
import org.apache.reef.util.Optional;
import org.apache.reef.tang.util.MonotonicSet;
import org.apache.reef.util.SingletonAsserter;

import javax.inject.Inject;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Manages all Evaluators.
 * See EvaluatorManager for the Driver side representation of a single Evaluator.
 */
@DriverSide
@Private
public final class Evaluators implements AutoCloseable {

  private static final Logger LOG = Logger.getLogger(Evaluators.class.getName());

  /**
   * A map between evaluatorId and the EvaluatorManager that handles this evaluator.
   */
  private final Map<String, EvaluatorManager> evaluators = new HashMap<>();

  /**
   * A set of evaluatorIds for "closed" (failed and returned) evaluators.
   */
  private final MonotonicSet<String> closedEvaluatorIds = new MonotonicSet<>();

  @Inject
  private Evaluators(@Parameter(DriverIdentifier.class) final String driverId) {
    LOG.log(Level.FINE, "Instantiated 'Evaluators' for driver {0}", driverId);
    // There can be several instances of the class for multiple REEFEnvironments.
    // It is still a singleton when REEF Driver owns the entire JVM.
    assert SingletonAsserter.assertSingleton(driverId, Evaluators.class);
  }

  /**
   * Closes all EvaluatorManager instances managed.
   */
  @Override
  public void close() {

    LOG.log(Level.FINER, "Closing the evaluators - begin");

    final List<EvaluatorManager> evaluatorsCopy;
    synchronized (this) {
      evaluatorsCopy = new ArrayList<>(this.evaluators.values());
    }

    for (final EvaluatorManager evaluatorManager : evaluatorsCopy) {
      if (!evaluatorManager.isClosedOrClosing()) {
        LOG.log(Level.WARNING, "Unclean shutdown of evaluator {0}", evaluatorManager.getId());
        evaluatorManager.close();
      }
    }

    LOG.log(Level.FINER, "Closing the evaluators - end");
  }

  /**
   * Return true if <em>all</em> evaluators are in closed state
   * (and their processing queues are empty).
   */
  public synchronized boolean allEvaluatorsAreClosed() {
    synchronized (this.evaluators) {
      for (final EvaluatorManager eval : this.evaluators.values()) {
        if (!eval.isClosed()) {
          return false;
        }
      }
    }
    return true;
  }

  /**
   * @param evaluatorId
   * @return the EvaluatorManager for the given id, if one exists.
   */
  public synchronized Optional<EvaluatorManager> get(final String evaluatorId) {
    return Optional.ofNullable(this.evaluators.get(evaluatorId));
  }

  /**
   * @param evaluatorId
   * @return true if evaluator with this id has already been closed.
   */
  public synchronized boolean wasClosed(final String evaluatorId) {
    return this.closedEvaluatorIds.contains(evaluatorId);
  }

  /**
   * Create new EvaluatorManager and add it to the collection.
   * <p>
   * FIXME: This method is a temporary fix for the race condition
   * described in issues #828 and #839.
   *
   * @param evaluatorManagerFactory Factory that builds new EvaluatorManager objects.
   * @param evaluatorMsg            Resource allocation message that contains data on the new evaluator.
   * @throws java.lang.IllegalArgumentException if the EvaluatorManager is already known.
   */
  public synchronized void put(
      final EvaluatorManagerFactory evaluatorManagerFactory,
      final ResourceAllocationEvent evaluatorMsg) {
    this.put(evaluatorManagerFactory.getNewEvaluatorManagerForNewEvaluator(evaluatorMsg));
  }

  /**
   * Adds an EvaluatorManager.
   *
   * @param evaluatorManager
   * @throws java.lang.IllegalArgumentException if the EvaluatorManager is already known.
   */
  public synchronized void put(final EvaluatorManager evaluatorManager) {
    final String evaluatorId = evaluatorManager.getId();
    if (this.wasClosed(evaluatorId)) {
      throw new IllegalArgumentException(
        "Trying to re-add an Evaluator that has already been closed: " + evaluatorId);
    }
    final EvaluatorManager prev = this.evaluators.put(evaluatorId, evaluatorManager);
    LOG.log(Level.FINEST, "Adding: {0} previous: {1}", new Object[]{evaluatorId, prev});
    if (prev != null) {
      throw new IllegalArgumentException(
        "Trying to re-add an Evaluator that is already known: " + evaluatorId);
    }
  }

  /**
   * Moves evaluator from map of active evaluators to set of closed evaluators.
   */
  public synchronized void removeClosedEvaluator(final EvaluatorManager evaluatorManager) {

    final String evaluatorId = evaluatorManager.getId();
    LOG.log(Level.FINE, "Removing closed evaluator: {0}", evaluatorId);

    if (!evaluatorManager.isClosed()) {
      throw new IllegalArgumentException("Removing evaluator that has not been closed yet: " + evaluatorId);
    }

    if (!this.evaluators.containsKey(evaluatorId) && !this.closedEvaluatorIds.contains(evaluatorId)) {
      throw new IllegalArgumentException("Removing unknown evaluator: " + evaluatorId);
    }

    if (!this.evaluators.containsKey(evaluatorId) && this.closedEvaluatorIds.contains(evaluatorId)) {
      LOG.log(Level.FINE, "Removing closed evaluator which has already been removed: {0}", evaluatorId);
      return;
    }

    evaluatorManager.shutdown();
    this.evaluators.remove(evaluatorId);
    this.closedEvaluatorIds.add(evaluatorId);

    LOG.log(Level.FINEST, "Closed evaluator removed: {0}", evaluatorId);
  }
}