/*
 * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */

package org.opendaylight.controller.cluster.datastore.utils;

import akka.actor.ActorPath;
import akka.actor.ActorRef;
import akka.actor.ActorSelection;
import akka.actor.ActorSystem;
import akka.util.Timeout;
import org.opendaylight.controller.cluster.datastore.messages.FindPrimary;
import org.opendaylight.controller.cluster.datastore.messages.PrimaryFound;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import scala.concurrent.Await;
import scala.concurrent.Future;
import scala.concurrent.duration.Duration;
import scala.concurrent.duration.FiniteDuration;

import java.util.concurrent.TimeUnit;

import static akka.pattern.Patterns.ask;

/**
 * The ActorContext class contains utility methods which could be used by
 * non-actors (like DistributedDataStore) to work with actors a little more
 * easily. An ActorContext can be freely passed around to local object instances
 * but should not be passed to actors especially remote actors
 */
public class ActorContext {
    private static final Logger
        LOG = LoggerFactory.getLogger(ActorContext.class);

    public static final FiniteDuration ASK_DURATION = Duration.create(5, TimeUnit.SECONDS);
    public static final Duration AWAIT_DURATION = Duration.create(5, TimeUnit.SECONDS);

    private final ActorSystem actorSystem;
    private final ActorRef shardManager;

    public ActorContext(ActorSystem actorSystem, ActorRef shardManager){
        this.actorSystem = actorSystem;
        this.shardManager = shardManager;
    }

    public ActorSystem getActorSystem() {
        return actorSystem;
    }

    public ActorRef getShardManager() {
        return shardManager;
    }

    public ActorSelection actorSelection(String actorPath){
        return actorSystem.actorSelection(actorPath);
    }

    public ActorSelection actorSelection(ActorPath actorPath){
        return actorSystem.actorSelection(actorPath);
    }


    /**
     * Finds the primary for a given shard
     *
     * @param shardName
     * @return
     */
    public ActorSelection findPrimary(String shardName) {
        Object result = executeLocalOperation(shardManager,
            new FindPrimary(shardName), ASK_DURATION);

        if(result instanceof PrimaryFound){
            PrimaryFound found = (PrimaryFound) result;

            LOG.error("Primary found {}", found.getPrimaryPath());

            return actorSystem.actorSelection(found.getPrimaryPath());
        }
        throw new RuntimeException("primary was not found");
    }

    /**
     * Executes an operation on a local actor and wait for it's response
     * @param actor
     * @param message
     * @param duration
     * @return The response of the operation
     */
    public Object executeLocalOperation(ActorRef actor, Object message,
        FiniteDuration duration){
        Future<Object> future =
            ask(actor, message, new Timeout(duration));

        try {
            return Await.result(future, AWAIT_DURATION);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Execute an operation on a remote actor and wait for it's response
     * @param actor
     * @param message
     * @param duration
     * @return
     */
    public Object executeRemoteOperation(ActorSelection actor, Object message,
        FiniteDuration duration){
        Future<Object> future =
            ask(actor, message, new Timeout(duration));

        try {
            return Await.result(future, AWAIT_DURATION);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Execute an operation on the primary for a given shard
     * <p>
     *     This method first finds the primary for a given shard ,then sends
     *     the message to the remote shard and waits for a response
     * </p>
     * @param shardName
     * @param message
     * @param duration
     * @throws java.lang.RuntimeException when a primary is not found or if the message to the remote shard fails or times out
     *
     * @return
     */
    public Object executeShardOperation(String shardName, Object message, FiniteDuration duration){
        ActorSelection primary = findPrimary(shardName);

        return executeRemoteOperation(primary, message, duration);
    }

}