extras/rya.pcj.fluo/pcj.fluo.app/src/main/java/org/apache/rya/indexing/pcj/fluo/app/ConstructGraph.java

package org.apache.rya.indexing.pcj.fluo.app;
/*
 * 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.
 */

import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.UUID;

import org.apache.rya.api.domain.RyaStatement;
import org.apache.rya.api.model.VisibilityBindingSet;
import org.eclipse.rdf4j.model.BNode;
import org.eclipse.rdf4j.model.Value;
import org.eclipse.rdf4j.model.impl.SimpleValueFactory;
import org.eclipse.rdf4j.query.algebra.StatementPattern;

import com.google.common.base.Preconditions;

/**
 * Creates a construct query graph (represented as a Set of
 * {@link RyaStatement}s with Binding names subject, predicate, object) from a
 * given BindingSet and the underlying {@link ConstructProjection}s.
 *
 */
public class ConstructGraph {

    private Set<ConstructProjection> projections;
    private Set<String> bNodeNames;
    
    /**
     * Creates a ConstructGraph from the specified collection of {@link ConstructProjection}s.
     * @param projections - ConstructProjections used to create a ConstructGraph
     */
    public ConstructGraph(Set<ConstructProjection> projections) {
        Preconditions.checkNotNull(projections);
        Preconditions.checkArgument(projections.size() > 0);
        this.projections = projections;
        this.bNodeNames = getBNodeNames(projections);
    }
    
    /**
     * Creates a ConstructGraph from the given Collection of {@link StatementPattern}s.
     * @param patterns - StatementPatterns used to create a ConstructGraph
     */
    public ConstructGraph(Collection<StatementPattern> patterns) {
        Preconditions.checkNotNull(patterns);
        Preconditions.checkArgument(patterns.size() > 0);
        Set<ConstructProjection> projections = new HashSet<>();
        for(StatementPattern pattern: patterns) {
            projections.add(new ConstructProjection(pattern));
        }
        this.projections = projections;
        this.bNodeNames = getBNodeNames(projections);
    }
    
    private Set<String> getBNodeNames(Set<ConstructProjection> projections) {
        Set<String> bNodeNames = new HashSet<>();
        for (ConstructProjection projection : projections) {
            Optional<Value> optVal = projection.getSubjValue();
            if (optVal.isPresent() && optVal.get() instanceof BNode) {
                bNodeNames.add(projection.getSubjectSourceName());
            }
        }
        return bNodeNames;
    }
    
    private Map<String, BNode> getBNodeMap() {
        Map<String, BNode> bNodeMap = new HashMap<>();
        for(String name: bNodeNames) {
            bNodeMap.put(name, SimpleValueFactory.getInstance().createBNode(UUID.randomUUID().toString()));
        }
        return bNodeMap;
    }
    
    /**
     * @return - the {@link ConstructProjection}s used to build the construct graph
     * returned by {@link ConstructGraph#createGraphFromBindingSet(VisibilityBindingSet)}.
     */
    public Set<ConstructProjection> getProjections() {
        return projections;
    }
    
    /**
     * Creates a construct query graph represented as a Set of {@link RyaStatement}s 
     * @param bs - VisibilityBindingSet used to build statement BindingSets
     * @return - Set of RyaStatements that represent a construct query graph.  
     */
    public Set<RyaStatement> createGraphFromBindingSet(VisibilityBindingSet bs) {
        Set<RyaStatement> bSets = new HashSet<>();
        long ts = System.currentTimeMillis();
        Map<String, BNode> bNodes = getBNodeMap();
        for(ConstructProjection projection: projections) {
            RyaStatement statement = projection.projectBindingSet(bs, bNodes);
            //ensure that all RyaStatements in graph have the same timestamp
            statement.setTimestamp(ts);
            bSets.add(statement);
        }
        return bSets;
    }
    
    @Override
    public boolean equals(Object o) {
        if(this == o) {
            return true;
        }
        
        if(o instanceof ConstructGraph) {
            ConstructGraph graph = (ConstructGraph) o;
            return this.projections.equals(graph.projections);
        }
        return false;
    }
    
    @Override
    public int hashCode() {
        int hash = 17;
        for(ConstructProjection projection: projections) {
            hash += projection.hashCode();
        }
        
        return hash;
    }
}