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Utility component to generate Graphviz .dot notation from Neo4j graphs.
There is a newer version: 3.2.0-alpha05
/*
 * 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.visualization.graphviz;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

public class GraphStyle
{
    GraphStyle( StyleParameter... parameters )
    {
        this.configuration = new DefaultStyleConfiguration( parameters );
        this.nodeStyle = new DefaultNodeStyle( configuration );
        this.edgeStyle = new DefaultRelationshipStyle( configuration );
    }

    /**
     * Constructor for subclasses. Used to provide graph styles with more
     * elaborate configuration than the default configuration parameters can
     * provide.
     * @param nodeStyle
     *            the node style to use.
     * @param edgeStyle
     *            the relationship style to use.
     */
    public GraphStyle( NodeStyle nodeStyle, RelationshipStyle edgeStyle )
    {
        this.configuration = null;
        this.nodeStyle = nodeStyle;
        this.edgeStyle = edgeStyle;
    }

    /**
     * Emit the end of a graph. Override this method to change the format of the
     * end of a graph.
     * @param stream
     *            the stream to emit the graph ending to.
     * @throws IOException
     *             if there is an error in emitting the graph ending.
     */
    protected void emitGraphEnd( Appendable stream ) throws IOException
    {
        stream.append( "}\n" );
    }

    /**
     * Emit the start of a graph. Override this method to change the format of
     * the start of a graph.
     * @param stream
     *            the stream to emit the graph start to.
     * @throws IOException
     *             if there is an error in emitting the graph start.
     */
    protected void emitGraphStart( Appendable stream ) throws IOException
    {
        stream.append( "digraph Neo {\n" );
        emitHeaders(stream);
    }

    protected void emitHeaders( Appendable stream ) throws IOException
    {
        if ( configuration != null )
        {
            configuration.emitHeader( stream );
        }
        stream.append( "  node [\n" );
        if ( configuration != null )
        {
            configuration.emitHeaderNode( stream );
        }
        else
        {
            header().emitNode( stream );
        }
        stream.append( "  ]\n" );
        stream.append( "  edge [\n" );
        if ( configuration != null )
        {
            configuration.emitHeaderEdge( stream );
        }
        else
        {
            header().emitEdge( stream );
        }
        stream.append( "  ]\n" );

    }

    final NodeStyle nodeStyle;
    final RelationshipStyle edgeStyle;
    private final DefaultStyleConfiguration configuration;
    private static volatile Header header;

    GraphStyle getSubgraphStyle( final String subgraphName )
    {
        return new GraphStyle( nodeStyle, edgeStyle )
        {
            @Override
            protected void emitGraphStart( Appendable stream ) throws IOException
            {
                stream.append( String.format( " subgraph cluster_%s {", subgraphName ) );
            }

            @Override
            protected void emitGraphEnd( Appendable stream ) throws IOException
            {
                stream.append( String.format( " label = \"%s\"\n }\n", subgraphName ) );
            }
        };
    }

    static Header header()
    {
        Header instance = header;
        if ( instance == null )
        {
            synchronized ( GraphStyle.class )
            {
                instance = header;
                if ( instance == null )
                {
                    header = instance = new Header();
                }
            }
        }
        return instance;
    }

    static final class Header
    {
        private Header()
        {
            String prefix = getClass().getPackage().getName() + ".";
            String nodePrefix = prefix + "node.";
            String relPrefix = prefix + "relationship.";
            Properties properties = System.getProperties();
            for ( Object obj : properties.keySet() )
            {
                try
                {
                    String property = (String) obj;
                    if ( property.startsWith( nodePrefix ) )
                    {
                        nodeHeader.put( property
                            .substring( nodePrefix.length() ),
                            (String) properties.get( property ) );
                    }
                    else if ( property.startsWith( relPrefix ) )
                    {
                        edgeHeader.put(
                            property.substring( relPrefix.length() ),
                            (String) properties.get( property ) );
                    }
                }
                catch ( ClassCastException cce )
                {
                    continue;
                }
            }
            assertMember( nodeHeader, properties, prefix, "fontname",
                "Bitstream Vera Sans" );
            assertMember( nodeHeader, properties, prefix, "fontsize", "8" );
            assertMember( edgeHeader, properties, prefix, "fontname",
                "Bitstream Vera Sans" );
            assertMember( edgeHeader, properties, prefix, "fontsize", "8" );
            nodeHeader.put( "shape", "Mrecord" );
        }

        final Map nodeHeader = new HashMap();
        final Map edgeHeader = new HashMap();
        final Map graphHeader = new HashMap();

        private void assertMember( Map header,
            Properties properties, String prefix, String key, String def )
        {
            if ( !header.containsKey( key ) )
            {
                header.put( key, properties.getProperty( prefix + key, def ) );
            }
        }

        private void emitNode( Appendable stream ) throws IOException
        {
            emitHeader( stream, nodeHeader );
        }

        private void emitEdge( Appendable stream ) throws IOException
        {
            emitHeader( stream, edgeHeader );
        }
    }

    static void emitHeader( Appendable stream, Map header )
        throws IOException
    {
        for ( String key : header.keySet() )
        {
            stream.append( "    " + key + " = \"" + header.get( key ) + "\"\n" );
        }
    }

}