/*
 * 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.fusion.functions;

import org.apache.flink.api.common.functions.FlatJoinFunction;
import org.apache.flink.util.Collector;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.common.model.impl.pojo.EPGMEdge;
import org.gradoop.common.model.impl.pojo.EPGMVertex;

/**
 * 1) If there is no vertex match (the vertex is null) then it means that the edge should not be
 *    updated
 * 2) If there is vertex match, it means that the matched vertex the fused one, so the edge
 *    should now point to the newly fused vertex
 * 3) Ignore the edges not matching with the vertices (pointless edges that should not occur and
 *    should be removed)
 */
public class UpdateEdgesThoughToBeFusedVertices implements FlatJoinFunction<EPGMEdge, EPGMVertex, EPGMEdge> {
  /**
   * Reusable edge that is used to update the previous edges in order to connect them with the
   * new fused vertex
   */
  private static final EPGMEdge REUSABLE_EDGE = new EPGMEdge();

  /**
   * the fused vertex's id
   */
  private GradoopId vId;

  /**
   * Checks if I have to check the fused vertex among the edges' sources or not.
   */
  private boolean isSourceNow;

  /**
   * Given the parameters, I have the edge update utility function
   * @param vId       Id for the fused vertex
   * @param isSource  If the fusedVertex is considered as source or as a destination
   */
  public UpdateEdgesThoughToBeFusedVertices(GradoopId vId, boolean isSource) {
    this.vId = vId;
    this.isSourceNow = isSource;
  }

  @Override
  public void join(EPGMEdge edge, EPGMVertex vertex, Collector<EPGMEdge> collector) throws Exception {
    if (vertex == null) {
      collector.collect(edge);
    } else if (edge != null) {
      REUSABLE_EDGE.setId(GradoopId.get());
      REUSABLE_EDGE.setSourceId(isSourceNow ? vId : edge.getSourceId());
      REUSABLE_EDGE.setTargetId(isSourceNow ? edge.getTargetId() : vId);
      REUSABLE_EDGE.setProperties(edge.getProperties());
      REUSABLE_EDGE.setLabel(edge.getLabel());
      REUSABLE_EDGE.setGraphIds(edge.getGraphIds());
      collector.collect(REUSABLE_EDGE);
    }
  }
}
