/*
* 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.sparql.modify;
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream ;
import org.apache.jena.atlas.iterator.Iter;
import org.apache.jena.ext.com.google.common.collect.Iterators;
import org.apache.jena.graph.Node;
import org.apache.jena.graph.NodeFactory;
import org.apache.jena.graph.Triple;
import org.apache.jena.sparql.core.Quad;
import org.apache.jena.sparql.core.Substitute;
import org.apache.jena.sparql.core.Var;
import org.apache.jena.sparql.engine.binding.Binding;
import org.apache.jena.sparql.util.ModelUtils;
public class TemplateLib {
// See also Substitute -- combine?
// Or is this specifc enough to CONSTRUCT/Update template processing?
// TODO We could eliminate some of the duplication in this class by writing
// generic methods and adding a shared super-interface to Triple and Quad
/**
* Take a template, as a list of quad patterns, a default graph, and an
* iterator of bindings, and produce an iterator of quads that results from
* applying the template to the bindings.
*/
public static Iterator<Quad> template(List<Quad> quads, final Node dftGraph, Iterator<Binding> bindings) {
if ( quads == null || quads.isEmpty() )
return null;
quads = remapDefaultGraph(quads, dftGraph);
return calcQuads(quads, bindings);
}
/**
* Map quads to a different graph if they are in the default graph.
*/
public static List<Quad> remapDefaultGraph(List<Quad> quads, final Node dftGraph) {
// The fast path is "no change"
if ( quads == null || quads.isEmpty() )
return quads ;
if ( dftGraph == null || Quad.isDefaultGraph(dftGraph) )
return quads ;
Stream<Quad> remappedStream = quads.stream().map(q->
!q.isDefaultGraph() ? q : new Quad(dftGraph, q.getSubject(), q.getPredicate(), q.getObject())
) ;
return remappedStream.collect(Collectors.toList());
}
/** Substitute into triple patterns */
public static Iterator<Triple> calcTriples(final List<Triple> triples, Iterator<Binding> bindings) {
return Iterators.concat(Iter.map(bindings, new Function<Binding, Iterator<Triple>>() {
Map<Node, Node> bNodeMap = new HashMap<>();
@Override
public Iterator<Triple> apply(final Binding b) {
// Iteration is a new mapping of bnodes.
bNodeMap.clear();
List<Triple> tripleList = new ArrayList<>(triples.size());
for ( Triple triple : triples ) {
Triple q = subst(triple, b, bNodeMap);
if ( !q.isConcrete() || !ModelUtils.isValidAsStatement(q.getSubject(), q.getPredicate(), q.getObject()) ) {
// Log.warn(TemplateLib.class, "Unbound quad:
// "+FmtUtils.stringForQuad(quad)) ;
continue;
}
tripleList.add(q);
}
return tripleList.iterator();
}
}));
}
/** Substitute into quad patterns */
public static Iterator<Quad> calcQuads(final List<Quad> quads, Iterator<Binding> bindings) {
return Iterators.concat(Iter.map(bindings, new Function<Binding, Iterator<Quad>>() {
Map<Node, Node> bNodeMap = new HashMap<>();
@Override
public Iterator<Quad> apply(final Binding b) {
// Iteration is a new mapping of bnodes.
bNodeMap.clear();
List<Quad> quadList = new ArrayList<>(quads.size());
for ( Quad quad : quads ) {
Quad q = subst(quad, b, bNodeMap);
if ( !q.isConcrete() ) {
// Log.warn(TemplateLib.class, "Unbound quad:
// "+FmtUtils.stringForQuad(quad)) ;
continue;
}
quadList.add(q);
}
return quadList.iterator();
}
}));
}
/** Substitute into a quad, with rewriting of bNodes */
public static Quad subst(Quad quad, Binding b, Map<Node, Node> bNodeMap) {
Node g = quad.getGraph();
Node s = quad.getSubject();
Node p = quad.getPredicate();
Node o = quad.getObject();
Node g1 = g;
Node s1 = s;
Node p1 = p;
Node o1 = o;
// replace blank nodes.
if ( g1.isBlank() || Var.isBlankNodeVar(g1) )
g1 = newBlank(g1, bNodeMap);
if ( s1.isBlank() || Var.isBlankNodeVar(s1) )
s1 = newBlank(s1, bNodeMap);
if ( p1.isBlank() || Var.isBlankNodeVar(p1) )
p1 = newBlank(p1, bNodeMap);
if ( o1.isBlank() || Var.isBlankNodeVar(o1) )
o1 = newBlank(o1, bNodeMap);
Quad q = quad;
if ( s1 != s || p1 != p || o1 != o || g1 != g )
q = new Quad(g1, s1, p1, o1);
Quad q2 = Substitute.substitute(q, b);
return q2;
}
/** Substitute into a triple, with rewriting of bNodes */
public static Triple subst(Triple triple, Binding b, Map<Node, Node> bNodeMap) {
Node s = triple.getSubject();
Node p = triple.getPredicate();
Node o = triple.getObject();
Node s1 = s;
Node p1 = p;
Node o1 = o;
if ( s1.isBlank() || Var.isBlankNodeVar(s1) )
s1 = newBlank(s1, bNodeMap);
if ( p1.isBlank() || Var.isBlankNodeVar(p1) )
p1 = newBlank(p1, bNodeMap);
if ( o1.isBlank() || Var.isBlankNodeVar(o1) )
o1 = newBlank(o1, bNodeMap);
Triple t = triple;
if ( s1 != s || p1 != p || o1 != o )
t = new Triple(s1, p1, o1);
Triple t2 = Substitute.substitute(t, b);
return t2;
}
/** generate a blank node consistently */
private static Node newBlank(Node n, Map<Node, Node> bNodeMap) {
if ( !bNodeMap.containsKey(n) )
bNodeMap.put(n, NodeFactory.createBlankNode());
return bNodeMap.get(n);
}
}