/*
 * 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.raft.behaviors;

import akka.actor.ActorRef;
import org.opendaylight.controller.cluster.raft.RaftActorContext;
import org.opendaylight.controller.cluster.raft.RaftState;
import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;

/**
 * Leader which is termed as isolated.
 * <p/>
 * If the reply from the majority of the followers  is not received then the leader changes its behavior
 * to IsolatedLeader. An isolated leader may have followers and they would continue to receive replicated messages.
 * <p/>
 * A schedule is run, at an interval of (10 * Heartbeat-time-interval),  in the Leader
 * to check if its isolated or not.
 * <p/>
 * In the Isolated Leader , on every AppendEntriesReply, we aggressively check if the leader is isolated.
 * If no, then the state is switched back to Leader.
 *
 */
public class IsolatedLeader extends AbstractLeader {
    public IsolatedLeader(RaftActorContext context) {
        super(context);
    }

    // we received an Append Entries reply, we should switch the Behavior to Leader
    @Override
    protected RaftActorBehavior handleAppendEntriesReply(ActorRef sender,
        AppendEntriesReply appendEntriesReply) {
        RaftActorBehavior ret = super.handleAppendEntriesReply(sender, appendEntriesReply);

        // it can happen that this isolated leader interacts with a new leader in the cluster and
        // changes its state to Follower, hence we only need to switch to Leader if the state is still Isolated
        if (ret.state() == RaftState.IsolatedLeader && !isLeaderIsolated()) {
            LOG.info("IsolatedLeader {} switching from IsolatedLeader to Leader", leaderId);
            return switchBehavior(new Leader(context));
        }
        return ret;
    }

    @Override
    public RaftState state() {
        return RaftState.IsolatedLeader;
    }
}