/*
 * Copyright © 2014 - 2021 Leipzig University (Database Research Group)
 *
 * Licensed 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.gradoop.flink.model.impl.operators.matching.single.simulation.dual.functions;

import org.apache.flink.api.common.functions.FlatMapFunction;
import org.apache.flink.api.java.functions.FunctionAnnotation;
import org.apache.flink.util.Collector;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.flink.model.impl.operators.matching.common.tuples.TripleWithCandidates;
import org.gradoop.flink.model.impl.operators.matching.single.simulation.dual.tuples.TripleWithDirection;

/**
 * Clones and reverses the incoming triple:<br>
 * {@code (e,s,t,c) -> (e,s,t,true,c),(e,t,s,false,c)}
 * <p>
 * Forwarded fields:<br>
 * {@code f0->f0}: edge id<br>
 * {@code f3->f4}: query candidates
 */
@FunctionAnnotation.ForwardedFields("f0;f3->f4")
public class CloneAndReverse implements
  FlatMapFunction<TripleWithCandidates<GradoopId>, TripleWithDirection> {

  /**
   * Reduce instantiations
   */
  private final TripleWithDirection reuseTuple;

  /**
   * Constructor
   */
  public CloneAndReverse() {
    reuseTuple = new TripleWithDirection();
  }

  @Override
  public void flatMap(TripleWithCandidates<GradoopId> tripleWithCandidates,
    Collector<TripleWithDirection> collector) throws Exception {
    reuseTuple.setEdgeId(tripleWithCandidates.getEdgeId());
    reuseTuple.setCandidates(tripleWithCandidates.getCandidates());

    reuseTuple.setSourceId(tripleWithCandidates.getSourceId());
    reuseTuple.setTargetId(tripleWithCandidates.getTargetId());
    reuseTuple.setOutgoing(true);
    collector.collect(reuseTuple);

    reuseTuple.setSourceId(tripleWithCandidates.getTargetId());
    reuseTuple.setTargetId(tripleWithCandidates.getSourceId());
    reuseTuple.setOutgoing(false);
    collector.collect(reuseTuple);
  }
}
