/*
 * Copyright (C) 2009-2018 Lightbend Inc. <https://www.lightbend.com>
 */

package jdocs.sharding;


import java.util.Optional;
import java.time.Duration;

import akka.actor.AbstractActor;
import akka.actor.ActorInitializationException;
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.OneForOneStrategy;
import akka.actor.PoisonPill;
import akka.actor.Props;
import akka.actor.SupervisorStrategy;
import akka.actor.ReceiveTimeout;
//#counter-extractor
import akka.cluster.sharding.ShardRegion;

//#counter-extractor

//#counter-start
import akka.japi.Option;
import akka.cluster.sharding.ClusterSharding;
import akka.cluster.sharding.ClusterShardingSettings;

//#counter-start
import akka.persistence.AbstractPersistentActor;
import akka.japi.pf.DeciderBuilder;

// Doc code, compile only
public class ClusterShardingTest {

  ActorSystem system = null;

  ActorRef getSelf() {
    return null;
  }

  public void demonstrateUsage() {
    //#counter-extractor
    ShardRegion.MessageExtractor messageExtractor = new ShardRegion.MessageExtractor() {

      @Override
      public String entityId(Object message) {
        if (message instanceof Counter.EntityEnvelope)
          return String.valueOf(((Counter.EntityEnvelope) message).id);
        else if (message instanceof Counter.Get)
          return String.valueOf(((Counter.Get) message).counterId);
        else
          return null;
      }

      @Override
      public Object entityMessage(Object message) {
        if (message instanceof Counter.EntityEnvelope)
          return ((Counter.EntityEnvelope) message).payload;
        else
          return message;
      }

      @Override
      public String shardId(Object message) {
        int numberOfShards = 100;
        if (message instanceof Counter.EntityEnvelope) {
          long id = ((Counter.EntityEnvelope) message).id;
          return String.valueOf(id % numberOfShards);
        } else if (message instanceof Counter.Get) {
          long id = ((Counter.Get) message).counterId;
          return String.valueOf(id % numberOfShards);
        } else {
          return null;
        }
      }

    };
    //#counter-extractor

    //#counter-start
    Option<String> roleOption = Option.none();
    ClusterShardingSettings settings = ClusterShardingSettings.create(system);
    ActorRef startedCounterRegion = ClusterSharding.get(system).start("Counter",
      Props.create(Counter.class), settings, messageExtractor);
    //#counter-start

    //#counter-usage
    ActorRef counterRegion = ClusterSharding.get(system).shardRegion("Counter");
    counterRegion.tell(new Counter.Get(123), getSelf());

    counterRegion.tell(new Counter.EntityEnvelope(123,
        Counter.CounterOp.INCREMENT), getSelf());
    counterRegion.tell(new Counter.Get(123), getSelf());
    //#counter-usage

    //#counter-supervisor-start
    ClusterSharding.get(system).start("SupervisedCounter",
        Props.create(CounterSupervisor.class), settings, messageExtractor);
    //#counter-supervisor-start

    //#proxy-dc
    ActorRef counterProxyDcB =
      ClusterSharding.get(system).startProxy(
        "Counter",
        Optional.empty(),
        Optional.of("B"), // data center name
        messageExtractor);
    //#proxy-dc
  }

  public void demonstrateUsage2() {
    ShardRegion.MessageExtractor messageExtractor = new ShardRegion.MessageExtractor() {

      @Override
      public String entityId(Object message) {
        if (message instanceof Counter.EntityEnvelope)
          return String.valueOf(((Counter.EntityEnvelope) message).id);
        else if (message instanceof Counter.Get)
          return String.valueOf(((Counter.Get) message).counterId);
        else
          return null;
      }

      @Override
      public Object entityMessage(Object message) {
        if (message instanceof Counter.EntityEnvelope)
          return ((Counter.EntityEnvelope) message).payload;
        else
          return message;
      }

      //#extractShardId-StartEntity
      @Override
      public String shardId(Object message) {
        int numberOfShards = 100;
        if (message instanceof Counter.EntityEnvelope) {
          long id = ((Counter.EntityEnvelope) message).id;
          return String.valueOf(id % numberOfShards);
        } else if (message instanceof Counter.Get) {
          long id = ((Counter.Get) message).counterId;
          return String.valueOf(id % numberOfShards);
        } else if (message instanceof ShardRegion.StartEntity) {
          long id = Long.valueOf(((ShardRegion.StartEntity) message).entityId());
          return String.valueOf(id % numberOfShards);
        } else {
          return null;
        }
      }
      //#extractShardId-StartEntity

    };
  }

  static//#counter-actor
  public class Counter extends AbstractPersistentActor {

    public enum CounterOp {
      INCREMENT, DECREMENT
    }

    public static class Get {
      final public long counterId;

      public Get(long counterId) {
        this.counterId = counterId;
      }
    }

    public static class EntityEnvelope {
      final public long id;
      final public Object payload;

      public EntityEnvelope(long id, Object payload) {
        this.id = id;
        this.payload = payload;
      }
    }

    public static class CounterChanged {
      final public int delta;

      public CounterChanged(int delta) {
        this.delta = delta;
      }
    }

    int count = 0;

    // getSelf().path().name() is the entity identifier (utf-8 URL-encoded)
    @Override
    public String persistenceId() {
      return "Counter-" + getSelf().path().name();
    }

    @Override
    public void preStart() throws Exception {
      super.preStart();
      getContext().setReceiveTimeout(Duration.ofSeconds(120));
    }

    void updateState(CounterChanged event) {
      count += event.delta;
    }

    @Override
    public Receive createReceiveRecover() {
      return receiveBuilder()
          .match(CounterChanged.class, this::updateState)
          .build();
    }

    @Override
    public Receive createReceive() {
      return receiveBuilder()
        .match(Get.class, this::receiveGet)
        .matchEquals(CounterOp.INCREMENT, msg -> receiveIncrement())
        .matchEquals(CounterOp.DECREMENT, msg -> receiveDecrement())
        .matchEquals(ReceiveTimeout.getInstance(), msg -> passivate())
        .build();
    }

    private void receiveGet(Get msg) {
      getSender().tell(count, getSelf());
    }

    private void receiveIncrement() {
      persist(new CounterChanged(+1), this::updateState);
    }

    private void receiveDecrement() {
      persist(new CounterChanged(-1), this::updateState);
    }

    private void passivate() {
      getContext().getParent().tell(
          new ShardRegion.Passivate(PoisonPill.getInstance()), getSelf());
    }

  }

  //#counter-actor

  static//#supervisor
  public class CounterSupervisor extends AbstractActor {

    private final ActorRef counter = getContext().actorOf(
        Props.create(Counter.class), "theCounter");

    private static final SupervisorStrategy strategy =
      new OneForOneStrategy(DeciderBuilder.
        match(IllegalArgumentException.class, e -> SupervisorStrategy.resume()).
        match(ActorInitializationException.class, e -> SupervisorStrategy.stop()).
        match(Exception.class, e -> SupervisorStrategy.restart()).
        matchAny(o -> SupervisorStrategy.escalate()).build());

    @Override
    public SupervisorStrategy supervisorStrategy() {
      return strategy;
    }

    @Override
    public Receive createReceive() {
      return receiveBuilder()
        .match(Object.class, msg -> counter.forward(msg, getContext()))
        .build();
    }

  }
  //#supervisor

}