jena-extras/jena-querybuilder/src/main/java/org/apache/jena/arq/querybuilder/updatebuilder/QuadIteratorBuilder.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.arq.querybuilder.updatebuilder;

import java.util.function.Function;

import org.apache.jena.arq.querybuilder.Converters;
import org.apache.jena.graph.Node;
import org.apache.jena.graph.Triple;
import org.apache.jena.query.Query;
import org.apache.jena.query.QueryParseException;
import org.apache.jena.sparql.core.Quad;
import org.apache.jena.sparql.core.TriplePath;
import org.apache.jena.sparql.syntax.*;
import org.apache.jena.util.iterator.ExtendedIterator;
import org.apache.jena.util.iterator.WrappedIterator;

/**
 * A class to construct a quad iterator from the elements.
 *
 */
class QuadIteratorBuilder implements ElementVisitor {
	// the default graph name
	private final Node defaultGraph;
	// the extended iterator we will add to.
	ExtendedIterator<Quad> iter = WrappedIterator.emptyIterator();

	// a function to map triples to quads using the default graph name.
	private final Function<Triple,Quad> MAP = 
			new Function<Triple,Quad>(){

		@Override
		public Quad apply(Triple triple) {
			return new Quad( defaultGraph, 
					Converters.checkVar( triple.getSubject()),
					Converters.checkVar( triple.getPredicate()),
					Converters.checkVar( triple.getObject()));
		}
	};

	/**
	 * Constructor.
	 * @param defaultGraph the default graph name.
	 */
	QuadIteratorBuilder(Node defaultGraph)
	{
		this.defaultGraph = defaultGraph;
	}


	@Override
	public void visit(ElementTriplesBlock el) {
		iter = iter.andThen( WrappedIterator.create(el.getPattern().getList().iterator())
				.mapWith( MAP ));
	}

	@Override
	public void visit(ElementPathBlock el) {
		for (final TriplePath pth : el.getPattern().getList())
		{
			if ( ! pth.isTriple())
			{
				throw new QueryParseException("Paths not permitted in data quad", -1, -1) ;   
			}
		}
		iter = iter.andThen( 
				WrappedIterator.create(el.getPattern().getList().iterator())
				.mapWith( pth -> pth.asTriple() )
				.mapWith( MAP ));
	}

	@Override
	public void visit(ElementFilter el) {
		throw new QueryParseException("Paths not permitted in data quad", -1, -1) ;   
	}

	@Override
	public void visit(ElementAssign el) {
		throw new QueryParseException("element assignment not permitted in data quad", -1, -1) ;   
	}

	@Override
	public void visit(ElementBind el) {
		throw new QueryParseException("bind not permitted in data quad", -1, -1) ;   

	}

	@Override
	public void visit(ElementFind el) {
	    throw new QueryParseException("FIND not permitted in data quad", -1, -1) ;   
	}

	@Override
	public void visit(ElementData el) {
		throw new QueryParseException("element data not permitted in data quad", -1, -1) ;   
	}

	@Override
	public void visit(ElementUnion el) {
		for (final Element e : el.getElements())
		{
			e.visit( this );
		}
	}

	@Override
	public void visit(ElementOptional el) {
		throw new QueryParseException("optional not permitted in data quad", -1, -1) ;   
	}

	@Override
	public void visit(ElementGroup el) {
		for (final Element e : el.getElements())
		{
			e.visit( this );
		}
	}

	@Override
	public void visit(ElementDataset el) {
		iter = iter.andThen(el.getDataset().find());			
	}

	@Override
	public void visit(ElementNamedGraph el) {
		final QuadIteratorBuilder bldr = new QuadIteratorBuilder( el.getGraphNameNode());
		el.getElement().visit(bldr);
		iter = iter.andThen( bldr.iter );
	}

	@Override
	public void visit(ElementExists el) {
		throw new QueryParseException("exists not permitted in data quad", -1, -1) ;   
	}

	@Override
	public void visit(ElementNotExists el) {
		throw new QueryParseException("not exists not permitted in data quad", -1, -1) ;   
	}

	@Override
	public void visit(ElementMinus el) {
		throw new QueryParseException("minus not permitted in data quad", -1, -1) ;		
	}

	@Override
	public void visit(ElementService el) {
		throw new QueryParseException("service not permitted in data quad", -1, -1) ;		
	}

	@Override
	public void visit(ElementSubQuery el) {
		final Query q = el.getQuery();
		q.getQueryPattern().visit( this );
	}

}