/**
 * 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 org.apache.jena.atlas.io.AWriter;
import org.apache.jena.atlas.io.IO;
import org.apache.jena.atlas.lib.CharSpace;
import org.apache.jena.graph.Node;
import org.apache.jena.graph.Triple;
import org.apache.jena.riot.out.NodeFormatter;
import org.apache.jena.riot.out.NodeFormatterNT;
import org.apache.jena.riot.system.StreamRDF;
import org.apache.jena.riot.system.StreamRDFLib;
import org.apache.jena.sparql.core.Quad;

/**
 * An output of triples / quads that is streaming. It writes N-triples/N-quads.
 */

public class WriterStreamRDFPlain implements StreamRDF {
    // This class is the overall structure - the NodeFormatter controls the
    // appearance of the Nodes themselves.

    protected final AWriter       out;
    private final NodeFormatter   nodeFmt;

    /**
     * Output tuples, using UTF8 output See {@link StreamRDFLib#writer} for
     * ways to create a AWriter object.
     */
    public WriterStreamRDFPlain(AWriter w) {
        this(w, CharSpace.UTF8);
    }

    /**
     * Output tuples, choosing ASCII or UTF8.
     * See {@link StreamRDFLib#writer} for ways to create a AWriter object.
     */
    public WriterStreamRDFPlain(AWriter w, CharSpace charSpace) {
        this(w, new NodeFormatterNT(charSpace));
    }

    /**
     * Output tuples using a specific {@link NodeFormatter}.
     */
    public WriterStreamRDFPlain(AWriter w, NodeFormatter nodeFmt) {
        this.out = w;
        this.nodeFmt = nodeFmt;
    }

    protected NodeFormatter getFmt() { return nodeFmt; }

    @Override
    public void start() {}

    @Override
    public void finish() {
        IO.flush(out);
    }

    @Override
    public void triple(Triple triple) {
        Node s = triple.getSubject();
        Node p = triple.getPredicate();
        Node o = triple.getObject();

        format(s);
        out.print(" ");
        format(p);
        out.print(" ");
        format(o);
        out.print(" .\n");
    }

    @Override
    public void quad(Quad quad) {
        Node s = quad.getSubject();
        Node p = quad.getPredicate();
        Node o = quad.getObject();
        Node g = quad.getGraph();

        format(s);
        out.print(" ");
        format(p);
        out.print(" ");
        format(o);

        if ( outputGraphSlot(g) ) {
            out.print(" ");
            format(g);
        }
        out.print(" .\n");
    }

    protected void format(Node n) {
        getFmt().format(out, n);
    }

    @Override
    public void base(String base) {}

    @Override
    public void prefix(String prefix, String iri) {}

    private static boolean outputGraphSlot(Node g) {
        return (g != null && g != Quad.tripleInQuad && !Quad.isDefaultGraph(g));
    }
}
