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A generic command shell with a client and server part.
There is a newer version: 3.3.2
/*
 * 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 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.shell.impl;

import java.io.Serializable;
import java.rmi.RemoteException;
import java.util.Collections;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;

import org.neo4j.shell.Session;
import org.neo4j.shell.ShellException;
import org.neo4j.shell.ShellServer;
import org.neo4j.shell.TabCompletion;
import org.neo4j.shell.Welcome;

/**
 * A common implementation of a {@link ShellServer}.
 */
public abstract class SimpleAppServer implements ShellServer
{
    private ShellServer remoteEndPoint;
    protected final BashVariableInterpreter bashInterpreter = new BashVariableInterpreter();

    /**
     * The default RMI name for a shell server,
     * see {@link #makeRemotelyAvailable(int, String)}.
     */
    public static final String DEFAULT_NAME = "shell";

    /**
     * The default RMI port for a shell server,
     * see {@link #makeRemotelyAvailable(int, String)}.
     */
    public static final int DEFAULT_PORT = 1337;

    private final Map clientSessions = new ConcurrentHashMap<>();

    private final AtomicInteger nextClientId = new AtomicInteger();

    /**
     * Constructs a new server.
     * @throws RemoteException if an RMI exception occurs.
     */
    public SimpleAppServer()
        throws RemoteException
    {
        super();
    }

    @Override
    public String getName()
    {
        return DEFAULT_NAME;
    }

    @Override
    public Serializable interpretVariable( Serializable clientID, String key ) throws ShellException, RemoteException
    {
        return (Serializable) getClientSession( clientID ).get( key );
    }

    protected Serializable newClientId()
    {
        return nextClientId.incrementAndGet();
    }

    @Override
    public Welcome welcome( Map initialSession ) throws RemoteException, ShellException
    {
        Serializable clientId = newClientId();
        if ( clientSessions.containsKey( clientId ) )
        {
            throw new IllegalStateException( "Client " + clientId + " already initialized" );
        }
        Session session = newSession( clientId, initialSession );
        clientSessions.put( clientId, session );
        try
        {
            String message = noWelcome( initialSession ) ? "" : getWelcomeMessage();
            return new Welcome( message, clientId, getPrompt( session ) );
        }
        catch ( ShellException e )
        {
            throw new RemoteException( e.getMessage() );
        }
    }

    private boolean noWelcome( Map initialSession )
    {
        final Serializable quiet = initialSession.get( "quiet" );
        if ( quiet == null )
        {
            return false;
        }
        if ( quiet instanceof Boolean )
        {
            return (Boolean) quiet;
        }
        return quiet.toString().equalsIgnoreCase( "true" );
    }

    private Session newSession( Serializable id, Map initialSession ) throws ShellException
    {
        Session session = new Session( id );
        initialPopulateSession( session );
        for ( Map.Entry entry : initialSession.entrySet() )
        {
            session.set( entry.getKey(), entry.getValue() );
        }
        return session;
    }

    protected void initialPopulateSession( Session session ) throws ShellException
    {   // No initial session by default
    }

    /**
     * Returns a prompt given a session, where the session may contain a custom "PS1" prompt variable.
     *
     * @param session the session to get custom prompt and other variables from.
     * @return the interpreted prompt to return to the client.
     */
    protected abstract String getPrompt( Session session ) throws ShellException;

    protected String getDefaultPrompt()
    {
        return "sh$ ";
    }

    protected String getWelcomeMessage()
    {
        return "Welcome to the shell";
    }

    public Session getClientSession( Serializable clientID )
    {
        Session session = clientSessions.get( clientID );
        if ( session == null )
        {
            throw new IllegalStateException( "Client " + clientID + " not initialized" );
        }
        return session;
    }

    @Override
    public void leave( Serializable clientID ) throws RemoteException
    {
        // TODO how about clients not properly leaving?

        if ( clientSessions.remove( clientID ) == null )
        {
            throw new IllegalStateException( "Client " + clientID + " not initialized" );
        }
    }

    @Override
    public synchronized void shutdown() throws RemoteException
    {
        if ( remoteEndPoint != null )
        {
            remoteEndPoint.shutdown();
            remoteEndPoint = null;
        }
    }

    @Override
    public synchronized void makeRemotelyAvailable( int port, String name )
        throws RemoteException
    {
        remoteEndPoint().makeRemotelyAvailable( port, name );
    }

    @Override
    public synchronized void makeRemotelyAvailable( String host, int port, String name ) throws RemoteException
    {
        remoteEndPoint().makeRemotelyAvailable( host, port, name );
    }

    private ShellServer remoteEndPoint() throws RemoteException
    {
        if ( remoteEndPoint == null )
        {
            remoteEndPoint = new RemotelyAvailableServer( this );
        }
        return remoteEndPoint;
    }

    @Override
    public String[] getAllAvailableCommands()
    {
        return new String[0];
    }

    public TabCompletion tabComplete( String partOfLine, Session session )
    {
        return new TabCompletion( Collections.emptyList(), 0 );
    }

    @Override
    public void setSessionVariable( Serializable clientID, String key, Object value ) throws ShellException
    {
        getClientSession( clientID ).set( key, value );
    }
}