/*
 * Copyright 2018 LinkedIn Corp. Licensed under the BSD 2-Clause License (the "License"). See License in the project root for license information.
 *
 */

package com.linkedin.kafka.cruisecontrol.model;

import com.linkedin.cruisecontrol.monitor.sampling.aggregator.MetricValues;
import com.linkedin.kafka.cruisecontrol.common.Resource;
import com.linkedin.kafka.cruisecontrol.monitor.metricdefinition.KafkaMetricDef;
import java.util.Set;
import java.util.function.Function;

/**
 * A factory class of replica sort functions. It is always preferred to use the functions in this factory instead
 * of writing ad-hoc functions.
 */
public final class ReplicaSortFunctionFactory {
  // Priority functions
  /** Prioritize the immigrant replicas */
  private static final Function<Replica, Integer> PRIORITIZE_IMMIGRANTS = r -> r.originalBroker() != r.broker() ? 0 : 1;
  /** Prioritize the offline replicas */
  private static final Function<Replica, Integer> PRIORITIZE_OFFLINE_REPLICAS = r -> r.isCurrentOffline() ? 0 : 1;
  /** Prioritize the disk immigrant replicas */
  private static final Function<Replica, Integer> PRIORITIZE_DISK_IMMIGRANTS = r -> r.originalDisk() != r.disk() ? 0 : 1;

  // Selection functions
  /** Select leaders only */
  private static final Function<Replica, Boolean> SELECT_LEADERS = Replica::isLeader;
  /** Select followers only */
  private static final Function<Replica, Boolean> SELECT_FOLLOWERS = r -> !r.isLeader();
  /** Select online replicas only */
  private static final Function<Replica, Boolean> SELECT_ONLINE_REPLICAS = r -> !r.isCurrentOffline();
  /** Select offline replicas only */
  private static final Function<Replica, Boolean> SELECT_OFFLINE_REPLICAS = Replica::isCurrentOffline;
  /** Select immigrants only */
  private static final Function<Replica, Boolean> SELECT_IMMIGRANTS = r -> r.originalBroker() != r.broker();
  /** Select immigrant or offline replicas only */
  private static final Function<Replica, Boolean> SELECT_IMMIGRANT_OR_OFFLINE_REPLICAS = r -> r.originalBroker() != r.broker()
                                                                                              || r.isCurrentOffline();

  private ReplicaSortFunctionFactory() {
  }

  // Score functions
  /**
   * @param metricGroup the metric group to score
   * @return A score function to score by the metric group value of the given metric group in positive way, i.e. the higher
   *         the metric group value, the higher the score.
   */
  public static Function<Replica, Double> sortByMetricGroupValue(String metricGroup) {
    return r -> {
      MetricValues metricValues = r.load()
                                   .loadByWindows()
                                   .valuesForGroup(metricGroup, KafkaMetricDef.commonMetricDef(), true);
      return (double) metricValues.avg();
    };
  }

  /**
   * @param metricGroup the metric group to score
   * @return A score function to score by the metric group value of the given metric group in negative way, i.e. the higher
   *         the metric group value, the lower the score.
   */
  public static Function<Replica, Double> reverseSortByMetricGroupValue(String metricGroup) {
    return r -> {
      MetricValues metricValues = r.load()
                                   .loadByWindows()
                                   .valuesForGroup(metricGroup, KafkaMetricDef.commonMetricDef(), true);
      return -(double) metricValues.avg();
    };
  }

  // Priority functions
  /**
   * @return A priority function that prioritize the immigrants replicas.
   */
  public static Function<Replica, Integer> prioritizeImmigrants() {
    return PRIORITIZE_IMMIGRANTS;
  }

  /**
   * @return A priority function that prioritize the offline replicas.
   */
  public static Function<Replica, Integer> prioritizeOfflineReplicas() {
    return PRIORITIZE_OFFLINE_REPLICAS;
  }

  /**
   * @return A priority function that prioritize the immigrant replicas to the disk.
   */
  public static Function<Replica, Integer> prioritizeDiskImmigrants() {
    return PRIORITIZE_DISK_IMMIGRANTS;
  }

  // Selection functions
  /**
   * @return A selection function that only includes immigrant replicas.
   */
  public static Function<Replica, Boolean> selectImmigrants() {
    return SELECT_IMMIGRANTS;
  }

  /**
   * @return A selection function that only includes immigrant replicas and offline replicas.
   */
  public static Function<Replica, Boolean> selectImmigrantOrOfflineReplicas() {
    return SELECT_IMMIGRANT_OR_OFFLINE_REPLICAS;
  }

  /**
   * @return A selection function that only includes leaders.
   */
  public static Function<Replica, Boolean> selectLeaders() {
    return SELECT_LEADERS;
  }

  /**
   * @return A selection function that only includes followers.
   */
  public static Function<Replica, Boolean> selectFollowers() {
    return SELECT_FOLLOWERS;
  }

  /**
   * @return A selection function that only includes offline replicas.
   */
  public static Function<Replica, Boolean> selectOfflineReplicas() {
    return SELECT_OFFLINE_REPLICAS;
  }

  /**
   * @return A selection function that only includes online replicas.
   */
  public static Function<Replica, Boolean> selectOnlineReplicas() {
    return SELECT_ONLINE_REPLICAS;
  }

  /**
   * @param excludedTopics Topics excluded from partition movements.
   *
   * @return A selection function that filters out replicas which are online and from topics which should be excluded.
   */
  public static Function<Replica, Boolean> selectReplicasBasedOnExcludedTopics(Set<String> excludedTopics) {
    return r -> r.isOriginalOffline() || !excludedTopics.contains(r.topicPartition().topic());
  }

  /**
   * @param includedTopics Topics included for partition movements.
   *
   * @return A selection function that filters out replicas which are not from topics which should be included.
   */
  public static Function<Replica, Boolean> selectReplicasBasedOnIncludedTopics(Set<String> includedTopics) {
    return r -> includedTopics.contains(r.topicPartition().topic());
  }

  /**
   * @param resource The resource to check.
   * @param limit The resource limit used to filter replicas.
   *
   * @return A selection function that only includes replicas whose metric value for certain resource is above limit.
   */
  public static Function<Replica, Boolean> selectReplicasAboveLimit(Resource resource, double limit) {
    return r -> r.load().expectedUtilizationFor(resource) > limit;
  }

  /**
   * @param resource The resource to check.
   * @param limit The resource limit used to filter replicas.
   *
   * @return A selection function that only includes replicas whose metric value for certain resource is below limit.
   */
  public static Function<Replica, Boolean> selectReplicasBelowLimit(Resource resource, double limit) {
    return r -> r.load().expectedUtilizationFor(resource) < limit;
  }
}
