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Library implementing Paxos and Heartbeat components required for High Availability Neo4j
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/*
 * Copyright (c) 2002-2016 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see .
 */
package org.neo4j.cluster.statemachine;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.neo4j.cluster.com.message.Message;
import org.neo4j.cluster.com.message.MessageHolder;
import org.neo4j.cluster.com.message.MessageType;

/**
 * Trigger messages when given state transitions occur
 */
public class StateMachineRules
    implements StateTransitionListener
{
    private final MessageHolder outgoing;

    private Map,List> rules = new HashMap, List>(  );

    public StateMachineRules( MessageHolder outgoing )
    {
        this.outgoing = outgoing;
    }

    public StateMachineRules rule( State oldState,
                                   MessageType messageType,
                                   State newState,
                                   Message... messages
    )
    {
        List fromRules = rules.get( oldState );
        if (fromRules == null)
        {
            fromRules = new ArrayList(  );
            rules.put( oldState, fromRules );
        }
        fromRules.add( new StateMachineRule( oldState,  messageType, newState, messages ) );

        return this;
    }

    @Override
    public void stateTransition( StateTransition transition )
    {
        List oldStateRules = rules.get( transition.getOldState() );
        if (oldStateRules != null)
        {
            for( StateMachineRule oldStateRule : oldStateRules )
            {
                oldStateRule.stateTransition( transition );
            }
        }
    }

    private class StateMachineRule
        implements StateTransitionListener
    {
        State oldState;
        MessageType messageType;
        State newState;

        Message[] messages;

        private StateMachineRule( State oldState, MessageType messageType, State newState, Message[] messages )
        {
            this.oldState = oldState;
            this.messageType = messageType;
            this.newState = newState;
            this.messages = messages;
        }

        @Override
        public void stateTransition( StateTransition transition )
        {
            if (oldState.equals( transition.getOldState() ) &&
                transition.getMessage().getMessageType().equals( messageType ) &&
                newState.equals( transition.getNewState() ))
            {
                for( Message message : messages )
                {
                    outgoing.offer( message );
                }
            }
        }
    }
}