/**
* 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.path.eval ;
import java.util.* ;
import org.apache.jena.atlas.iterator.Iter ;
import org.apache.jena.graph.Graph ;
import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.path.P_FixedLength ;
import org.apache.jena.sparql.path.P_Mod ;
import org.apache.jena.sparql.path.P_NegPropSet ;
import org.apache.jena.sparql.path.Path ;
import org.apache.jena.sparql.util.Context ;
/** PathEngine, SPARQL semantics */
public class PathEngineSPARQL extends PathEngine
{
private boolean forwardMode ;
public PathEngineSPARQL(Graph graph, Context context) {
this(graph, true, context) ;
}
/* package */PathEngineSPARQL(Graph graph, boolean forward, Context context) {
super(graph, context) ;
this.forwardMode = forward ;
}
protected Collection<Node> collector() {
return new HashSet<Node>() ;
}
protected Set<Node> visitedAcc() {
return new HashSet<Node>() ;
}
@Override
protected void doSeq(Path pathStepLeft, Path pathStepRight, Node node, Collection<Node> output) {
Path part1 = forwardMode ? pathStepLeft : pathStepRight ;
Path part2 = forwardMode ? pathStepRight : pathStepLeft ;
// Feed one side into the other
Iter<Node> iter = eval(part1, node) ;
iter.forEachRemaining((n)->eval(part2, n, output)) ;
}
@Override
protected void doAlt(Path pathStepLeft, Path pathStepRight, Node node, Collection<Node> output) {
// Try both sizes, accumulate into output.
Iterator<Node> iter = eval(pathStepLeft, node) ;
fill(iter, output) ;
iter = eval(pathStepRight, node) ;
fill(iter, output) ;
}
@Override
protected void doNegatedPropertySet(P_NegPropSet pathNotOneOf, Node node, Collection<Node> output) {
if ( pathNotOneOf.getFwdNodes().size() > 0 ) {
Iterator<Node> nodes1 = stepExcludeForwards(node, pathNotOneOf.getFwdNodes()) ;
fill(nodes1, output) ;
}
if ( pathNotOneOf.getBwdNodes().size() > 0 ) {
Iterator<Node> nodes2 = stepExcludeBackwards(node, pathNotOneOf.getBwdNodes()) ;
fill(nodes2, output) ;
}
}
@Override
protected void doZeroOrOne(Path pathStep, Node node, Collection<Node> output) {
Collection<Node> x = visitedAcc() ;
eval(pathStep, node, x) ;
x.add(node) ;
output.addAll(x) ;
}
@Override
protected void doZeroOrMore(Path pathStep, Node node, Collection<Node> output) {
Set<Node> visited = visitedAcc() ;
ALP_1(forwardMode, 0, -1, node, pathStep, visited) ;
output.addAll(visited) ;
}
@Override
protected void doOneOrMore(Path pathStep, Node node, Collection<Node> output) {
Set<Node> visited = visitedAcc() ;
// Do one step without including.
Iter<Node> iter1 = eval(pathStep, node) ;
for (; iter1.hasNext();) {
Node n1 = iter1.next() ;
ALP_1(forwardMode, 0, -1, n1, pathStep, visited) ;
}
output.addAll(visited) ;
}
@Override
protected void doZero(Path path, Node node, Collection<Node> output) {
// {0} -- Not SPARQL
output.add(node) ;
}
private void ALP_1(boolean forwardMode, int stepCount, int maxStepCount, Node node, Path path, Set<Node> visited) {
if ( maxStepCount >= 0 && stepCount > maxStepCount )
return ;
if ( !visited.add(node) )
return ;
Iter<Node> iter1 = eval(path, node) ;
// For each step, add to results and recurse.
for (; iter1.hasNext();) {
Node n1 = iter1.next() ;
ALP_1(forwardMode, stepCount + 1, maxStepCount, n1, path, visited) ;
}
}
// Not SPARQL - counting versions.
@Override
protected void doZeroOrMoreN(Path pathStep, Node node, Collection<Node> output) {
Set<Node> visited = new HashSet<>() ;
ALP_N(node, pathStep, visited, output) ;
}
@Override
protected void doOneOrMoreN(Path pathStep, Node node, Collection<Node> output) {
Set<Node> visited = new HashSet<>() ;
// Do one step without including.
Iterator<Node> iter1 = eval(pathStep, node) ;
for (; iter1.hasNext();) {
Node n1 = iter1.next() ;
ALP_N(n1, pathStep, visited, output) ;
}
}
// This is the worker function for path{*} /counting (non_SPARQL) semantics.
private void ALP_N(Node node, Path path, Collection<Node> visited, Collection<Node> output) {
if ( visited.contains(node) )
return ;
// If output is a set, then no point going on if node has been added to
// the results.
// If output includes duplicates, more solutions are generated
// "visited" is nodes on this path (see the matching .remove).
if ( !output.add(node) )
return ;
visited.add(node) ;
Iterator<Node> iter1 = eval(path, node) ;
// For each step, add to results and recurse.
for (; iter1.hasNext();) {
Node n1 = iter1.next() ;
ALP_N(n1, path, visited, output) ;
}
visited.remove(node) ;
}
@Override
protected void doMultiLengthPath(Path pathStep, Node node, long min1, long max1, Collection<Node> output) {
// Not SPARQL
// Why not always reduce {N,M} to {N} and {0,M-N}
// Why not iterate, not recurse, for {N,}
// -- optimizer will have expanded this so only in unoptimized mode.
if ( min1 == P_Mod.UNSET )
// {,N}
min1 = 0 ;
// ----------------
// This code is for p{n,m} and :p{,n} inc :p{0,n}
// and for :p{N,}
// if ( max1 == P_Mod.UNSET ) max1 = 0 ;
if ( min1 == 0 )
output.add(node) ;
if ( max1 == 0 )
return ;
// The next step
long min2 = dec(min1) ;
long max2 = dec(max1) ;
Path p1 = pathStep ;
Path p2 = new P_Mod(pathStep, min2, max2) ;
if ( !forwardMode ) {
// Reverse order. Do the second bit first.
Path tmp = p1 ;
p1 = p2 ;
p2 = tmp ;
// This forces execution to be in the order that it's written, when
// working backwards.
// {N,*} is {*} then {N} backwards != do {N} then do {*} as
// cardinality of the
// two operations is different.
}
// One step.
Iterator<Node> iter = eval(p1, node) ;
// Moved on one step
for (; iter.hasNext();) {
Node n2 = iter.next() ;
Iterator<Node> iter2 = eval(p2, n2) ;
fill(iter2, output) ;
}
// If no matches, will not call eval and we drop out.
}
@Override
protected void doFixedLengthPath(Path pathStep, Node node, long fixedLength, Collection<Node> output) {
// Not SPARQL
if ( fixedLength == 0 ) {
output.add(node) ;
return ;
}
// P_Mod(path, count, count)
// One step.
Iterator<Node> iter = eval(pathStep, node) ;
// Build a path for all remaining steps.
long count2 = dec(fixedLength) ;
P_FixedLength nextPath = new P_FixedLength(pathStep, count2) ;
// For each element in the first step, do remaining step
// Accumulate across everything from first step.
for (; iter.hasNext();) {
Node n2 = iter.next() ;
Iterator<Node> iter2 = eval(nextPath, n2) ;
fill(iter2, output) ;
}
}
@Override
protected void flipDirection() {
forwardMode = !forwardMode ;
}
@Override
protected boolean direction() {
return forwardMode ;
}
}