TriGWriter.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.riot.writer;

import static org.apache.jena.riot.writer.WriterConst.*;

import java.util.Set;

import org.apache.jena.atlas.io.IndentedWriter;
import org.apache.jena.atlas.iterator.Iter;
import org.apache.jena.graph.Node;
import org.apache.jena.riot.system.PrefixMap;
import org.apache.jena.sparql.core.DatasetGraph;
import org.apache.jena.sparql.core.Quad;
import org.apache.jena.sparql.util.Context;

/** TriG pretty writer */
public class TriGWriter extends TriGWriterBase
{
    @Override
    protected void output(IndentedWriter iOut, DatasetGraph dsg, PrefixMap prefixMap, String baseURI, Context context) {
        TriGWriter$ w = new TriGWriter$(iOut, prefixMap, baseURI, context);
        w.write(dsg);
    }

    private static class TriGWriter$ extends TurtleShell
    {
        TriGWriter$(IndentedWriter out, PrefixMap prefixMap, String baseURI, Context context) {
            super(out, prefixMap, baseURI, context);
        }

        private void write(DatasetGraph dsg) {
            writeBase(baseURI);
            writePrefixes(prefixMap);
            if ( !prefixMap.isEmpty() && !dsg.isEmpty() )
                out.println();

            Set<Node> graphNames = Iter.toSet(dsg.listGraphNodes());

            boolean anyGraphOutput = writeGraphTriG(dsg, null, graphNames);

            for ( Node gn : graphNames ) {
                if ( anyGraphOutput )
                    out.println();
                anyGraphOutput |= writeGraphTriG(dsg, gn, graphNames);
            }
        }

        /** Return true if anything written */
        private boolean writeGraphTriG(DatasetGraph dsg, Node name, Set<Node> graphNames) {
            boolean dftGraph = ( name == null || name == Quad.defaultGraphNodeGenerated  );

            if ( dftGraph && dsg.getDefaultGraph().isEmpty() )
                return false;

            if ( dftGraph && ! GDFT_BRACE ) {
                // Non-empty default graph, no braces.
                // No indenting.
                writeGraphTTL(dsg, name, graphNames);
                return true;
            }

            // The graph will go in braces, whether non-empty default graph or a named graph.
            boolean NL_START =  ( dftGraph ? NL_GDFT_START : NL_GNMD_START );
            boolean NL_END =    ( dftGraph ? NL_GDFT_END : NL_GNMD_END );
            int INDENT_GRAPH =  ( dftGraph ? INDENT_GDFT : INDENT_GNMD );

            if ( !dftGraph ) {
                writeNode(name);
                out.print(" ");
            }

            out.print("{");
            if ( NL_START )
                out.println();
            else
                out.print(" ");

            out.incIndent(INDENT_GRAPH);
            writeGraphTTL(dsg, name, graphNames);
            out.decIndent(INDENT_GRAPH);

            if ( NL_END )
                out.ensureStartOfLine();
            out.println("}");
            return true;
        }
    }
}