    001/*
    002 * Copyright (c) 2016 Chris K Wensel <chris@wensel.net>. All Rights Reserved.
    003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
    004 *
    005 * Project and contact information: http://www.cascading.org/
    006 *
    007 * This file is part of the Cascading project.
    008 *
    009 * Licensed under the Apache License, Version 2.0 (the "License");
    010 * you may not use this file except in compliance with the License.
    011 * You may obtain a copy of the License at
    012 *
    013 *     http://www.apache.org/licenses/LICENSE-2.0
    014 *
    015 * Unless required by applicable law or agreed to in writing, software
    016 * distributed under the License is distributed on an "AS IS" BASIS,
    017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    018 * See the License for the specific language governing permissions and
    019 * limitations under the License.
    020 */
    021
    022package cascading.flow.planner.iso.transformer;
    023
    024import cascading.flow.planner.PlannerContext;
    025import cascading.flow.planner.graph.ElementGraph;
    026import cascading.flow.planner.graph.ElementGraphs;
    027import cascading.flow.planner.graph.ElementSubGraph;
    028import cascading.flow.planner.iso.expression.ExpressionGraph;
    029import cascading.flow.planner.iso.finder.GraphFinder;
    030import cascading.flow.planner.iso.finder.Match;
    031import cascading.flow.planner.rule.TransformException;
    032
    033/**
    034 * Class SubGraphTransformer will return a bounded sub-graph after matching a sub-graph within a contracted graph.
    035 */
    036public class SubGraphTransformer extends GraphTransformer<ElementGraph, ElementSubGraph>
    037  {
    038  private GraphTransformer graphTransformer;
    039  private ExpressionGraph subGraphMatcher;
    040  private GraphFinder subGraphFinder;
    041  private boolean findAllPrimaries = false;
    042
    043  public SubGraphTransformer( GraphTransformer graphTransformer, ExpressionGraph subGraphMatcher )
    044    {
    045    this.graphTransformer = graphTransformer;
    046    this.subGraphMatcher = subGraphMatcher;
    047    this.subGraphFinder = new GraphFinder( subGraphMatcher );
    048    this.findAllPrimaries = subGraphMatcher.supportsNonRecursiveMatch();
    049    }
    050
    051  public Transformed<ElementSubGraph> transform( PlannerContext plannerContext, ElementGraph rootGraph )
    052    {
    053    Transformed<ElementSubGraph> transformed = new Transformed<>( plannerContext, this, subGraphMatcher, rootGraph );
    054
    055    try
    056      {
    057      Transformed contractedTransformed = graphTransformer.transform( plannerContext, rootGraph ); // contracted graph transform
    058
    059      transformed.addChildTransform( contractedTransformed );
    060
    061      // apply contracted sub-graph matcher to get the bounded sub-graph of the original graph
    062      ElementGraph contractedGraph = contractedTransformed.getEndGraph();
    063
    064      Match match = findAllPrimaries ? subGraphFinder.findAllMatches( plannerContext, contractedGraph ) : subGraphFinder.findFirstMatch( plannerContext, contractedGraph );
    065
    066      if( !match.foundMatch() )
    067        return transformed;
    068
    069      ElementGraph contractedSubGraph = match.getMatchedGraph();
    070
    071      ElementSubGraph resultSubGraph = asSubGraphOf( rootGraph, contractedSubGraph ); // the bounded sub-graph of the rootGraph
    072
    073      transformed.setEndGraph( resultSubGraph );
    074
    075      return transformed;
    076      }
    077    catch( Throwable throwable )
    078      {
    079      throw new TransformException( throwable, transformed );
    080      }
    081    }
    082
    083  protected ElementSubGraph asSubGraphOf( ElementGraph rootGraph, ElementGraph contractedSubGraph )
    084    {
    085    return ElementGraphs.asSubGraph( rootGraph, contractedSubGraph, null );
    086    }
    087  }