/*
 * 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.algorithms.fsm.transactional.common.functions;

import com.google.common.collect.Sets;
import org.apache.flink.api.common.functions.RichMapFunction;
import org.apache.flink.configuration.Configuration;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.common.model.impl.pojo.EPGMEdge;
import org.gradoop.flink.algorithms.fsm.transactional.common.TFSMConstants;
import org.gradoop.flink.model.impl.layouts.transactional.tuples.GraphTransaction;

import java.util.Collection;
import java.util.Iterator;
import java.util.Set;

/**
 * Drops edges with infrequent labels and isolated vertices.
 */
public class FilterEdgesByLabel extends RichMapFunction<GraphTransaction, GraphTransaction> {

  /**
   * frequent edge labels
   */
  private Collection<String> frequentEdgeLabels;

  @Override
  public void open(Configuration parameters) throws Exception {
    super.open(parameters);

    Collection<String> broadcast = getRuntimeContext()
      .getBroadcastVariable(TFSMConstants.FREQUENT_EDGE_LABELS);

    this.frequentEdgeLabels = Sets.newHashSet(broadcast);
  }

  @Override
  public GraphTransaction map(GraphTransaction transaction) throws Exception {

    Set<GradoopId> referenceEdgeIds = Sets.newHashSet();

    // drop edges with infrequent labels

    Iterator<EPGMEdge> edgeIterator = transaction.getEdges().iterator();

    while (edgeIterator.hasNext()) {
      EPGMEdge next = edgeIterator.next();

      if (frequentEdgeLabels.contains(next.getLabel())) {
        referenceEdgeIds.add(next.getSourceId());
        referenceEdgeIds.add(next.getTargetId());
      } else {
        edgeIterator.remove();
      }
    }

    // drop vertex without any edges

    transaction.getVertices().removeIf(next -> !referenceEdgeIds.contains(next.getId()));

    return transaction;
  }
}
